DE112006004264B4 - Encoder frequency analysis - Google Patents

Abstract

A new method for diagnosing problems with a valve actuator or other rotating equipment. Frequency analysis is performed on velocity, position, moment, thrust or vibration data. Speed or position data can be provided by a rotary encoder.

Description

Technical area

The invention relates generally to the analysis of valve actuators and rotary position encoders, and more particularly to performing frequency analysis of the valve actuators and rotary position encoders with a built-in self-test.

background

In many applications it is necessary to measure the position of a rotating shaft of a rotating device. However, rotating devices are often complicated and have parts that are difficult to access. Further, rotating devices are often integrated into industrial processes where the cost of stopping operations to repair the rotating device often exceeds the cost of the rotating device. For example, rotary valves are often critical in industrial processes and repairing some parts of the valves requires shutting down the process. There is a need to precisely identify the position of a rotating shaft and objects driven by the rotating shaft, such as a valve stem. Likewise, there is a need to identify all load-bearing parts in a rotary device, such as a valve, so that preventive maintenance can be performed during scheduled shutdowns, or so that the rotary device can be operated in a manner that the device can last until the next planned shutdown remains operational. A need exists for a device capable of identifying both the position of a rotating shaft and the severity and location of problems within the rotating device to which the rotating shaft is connected.

One way to diagnose rotating devices uses frequency analysis. Cyclic data can be analyzed using a Fourier Transform (FT) algorithm to transform the data from a time domain to a frequency domain. One attempt to apply FT to motor operated valves involves measuring the current flowing to the motor, applying FT to the motor data, and consequently using the peaks in the frequency spectrum to diagnose the problems in the valve actuator drive train. However, this option does not measure the rotation speed of a shaft or determine the position of a rotating shaft. A motor current measuring device also does not include a device capable of determining the position of a rotating shaft.

One way to measure the position of a rotating component includes a rotary encoder. Rotary encoders include incremental and absolute encoders. Incremental encoders are used to measure the change in rotation of a shaft. A basic incremental encoder includes a plate with a large number of radially drawn lines. A photodiode or other sensor produces an electrical pulse each time a drawn line is sensed. A computer or other processor tracks the pulses to determine the position of the plate, and in turn the position of the shaft to which the plate is attached. For incremental encoders, position information is lost if the computer has no power, even if power is restored. Previous incremental encoders for valve actuators included a speed sensor, but the speed sensor and resulting data were not used for frequency analysis.

Absolute encoders do not require a power supply to maintain position information. Absolute encoders produce a single digital code for each specific angle of a rotating shaft. Absolute encoders can be a single wheel with a complex pattern built into the wheel. The single wheel is attached to the shaft in question and numerous unique angular positions can be identified by the patterns on the wheel. However, such wheels are only useful if the shaft will only make a single rotation.

Another version of absolute encoders uses multiple wheels with concentric rings on each of the wheels, with each ring providing a 1-bit data position. The multi-wheel version allows the measured shaft to make numerous rotations and still tracks the positions and number of rotations of the shaft. The presence of multiple wheels allows tracking multiple shaft rotations or determining multiple positions for a single rotation. However, multi-wheel absolute encoders are often special and not very reliable. It would be desirable to have a multi-wheel absolute encoder that is reliable and capable of producing velocity data for use in frequency analysis.

One attempt to solve this problem uses either 6 or 7 wheels. Each wheel provides 3-bit data. However, only a 2-bit Gray code is generated as position data by v-bit processing. This increases the reliability of the absolute encoder. However, dual sensors are not used. In addition, a speed sensor is not integrated into the absolute encoder and the velocity data is not generated for use in frequency analysis.

US 5,640,007 A discloses an absolute encoder that monitors rotational position and senses rotational displacement relative to a measurement scale. The absolute encoder comprises a plurality of rotatably mounted coding wheels, each wheel containing at least one sequence which, in combination, comprises the measuring scale. A pinion is provided between each pair of encoder wheels so that each of the encoder wheels rotates as the shaft rotates. Each sequence of the encoder wheel is monitored by a scanning mechanism to evaluate the shaft position. The scanning mechanism includes light emitting and detecting devices that monitor a specific area of each sequence to determine rotational position.

DE 92 08 470 U1 discloses an adjusting device for the relative angular difference between two rotating parts, comprising at least a guide arrangement for the driving part and a driven guide arrangement for at least one rotating part. The driven guide assemblies perform mutual sliding guidance of the rotating drive member to perform relative axial movement with respect to the rotating drive member and/or the rotating driven members to change the relative angular difference with respect to the axis between the rotating driver member and the rotating driven members. US 5,418,362 A discloses an encoder and a code plate for determining absolute position. The code plate includes a substrate, at least two bands formed on the substrate corresponding to factors of the desired count, two positions formed in each band, and an identifier in each band for identifying each band position so that each code plate position is uniquely identified by measuring the band identifiers. DE 103 61 062 A1 discloses a method for determining the actuating force generated by an electric drive, in particular a commutated direct current motor. First, the current consumption I1, I2 of the electric drive is recorded, then frequency spectra characteristic of the rotational position of the electric drive are recorded. These are present during times T1, T2 of a period Tges. The frequency spectra are differentiated within an FFT level; The speed n of the electric drive is then determined. DE 100 47 924 A1 discloses a sensor system for location or position detection with a signal generator for generating an analog sensor signal, an evaluation circuit for the analog sensor signal, an analog/digital converter for converting the evaluated analog sensor signal into a digital output variable, a computing means for converting it into a digital physical output variable, in particular in a location/position value, and an output interface for transmitting the digital physical output variable to a higher-level processing unit at synchronous deterministic times, in particular at a controller clock of the higher-level processing unit.

Disclosure of the invention

The present invention solves the problems with a valve system according to independent claim 1. Advantageous developments are specified in the dependent claims 2 to 20.

One embodiment of the invention includes rotary encoders for use with a rotary device. The rotary encoder includes one or more encoding wheels, each of the one or more encoding wheels including at least one encoding section capable of encoding a position of the rotating device. Also included is at least one double set of sensors that are suitable for monitoring the at least one coding section.

Another embodiment of the invention includes a valve actuator with an absolute encoder and a drive train adapted to drive the absolute encoder. The absolute encoder includes at least one encoding plate, a plurality of sensors capable of reading the at least one encoding plate, a speed sensor capable of generating speed data, at least one dual sensor for each of the plurality of sensors, and the speed sensor.

The features, advantages and various aspects of the present invention will become apparent to those skilled in the art from a consideration of the following detailed description in combination with the accompanying drawings.

Brief description of the drawings

• 1 die Räder einer Ausführungsform eines Drehgebers zeigt;
• 2 eine vollständig zusammengebaute Version der Ausführungsform von 1 zeigt;
• 3 eine teilweise zusammengebaute Version der Ausführungsform der 1 zeigt;
• 4 eine Draufsicht der Ausführungsform von 3 zeigt;
• 5 die Räder einer besonderen Ausführungsform eines Drehgebers zeigt;
• 6 eine repräsentative Reindiagnose in dem Frequenzbereich zeigt;
• 7 eine repräsentative Problemdiagnose in dem Frequenzbereich zeigt;
• 8 Datenwerte mit 128 Proben zeigt;
• 9 die in 8 verwendeten Daten vor dem Durchführen einer FourierTransformation (FT) der Daten zeigt;
• 10 die Datenauflösung mit 256 Proben zeigt;
• 11 die in 10 verwendeten Daten vor dem Durchführen einer FT der Daten zeigt;
• 12 eine Datenbestimmung mit 512 Proben zeigt;
• 13 die in 12 verwendeten Daten vor dem Durchführen einer FT der Daten zeigt;
• 14 die Datenauflösung mit 1024 Proben zeigt;
• 15 eine Tabelle zeigt, die die Genauigkeit einiger Ausführungsformen der vorliegenden Erfindung zeigt;
• 16 ein Beispiel von Frequenzbereichsdaten ist, die bei 26 Drehungen pro Minute (U/min) erhalten wurden;
• 17 ein weiteres Beispiel für Frequenzbereichsdaten ist, die bei 26 U/min erhalten wurden;
• 18 ein Beispiel für Frequenzbereichsdaten ist, die bei 18 U/min erhalten wurden; und
• 19 ein weiteres Beispiel für Frequenzbereichsdaten ist, die bei 18 U/min erhalten wurden.

While the description with the claims particularly sets out and clearly claims what is considered to be the present invention, the advantages of this invention can be more easily derived from the following description of the invention when read in conjunction with the accompanying drawings, in which:

• 1 shows the wheels of an embodiment of a rotary encoder;
• 2 a fully assembled version of the embodiment of 1 shows;
• 3 a partially assembled version of the embodiment of 1 shows;
• 4 a top view of the embodiment of 3 shows;
• 5 shows the wheels of a special embodiment of a rotary encoder;
• 6 shows a representative pure diagnosis in the frequency range;
• 7 shows a representative problem diagnosis in the frequency range;
• 8th Shows data values with 128 samples;
• 9 in the 8th used data before performing a Fourier Transform (FT) on the data;
• 10 shows the data resolution with 256 samples;
• 11 in the 10 used data before performing an FT of the data;
• 12 shows a data determination with 512 samples;
• 13 in the 12 used data before performing an FT of the data;
• 14 shows the data resolution with 1024 samples;
• 15 shows a table showing the accuracy of some embodiments of the present invention;
• 16 is an example of frequency domain data obtained at 26 revolutions per minute (rpm);
• 17 another example of frequency domain data obtained at 26 rpm;
• 18 is an example of frequency domain data obtained at 18 rpm; and
• 19 another example of frequency domain data obtained at 18 rpm.

Best Modes for Carrying Out the Invention

The present invention can be used with any valve actuator or other rotating device, such as a device that rotates between two positions. A particular embodiment of the present invention uses a rotary encoder with an integrated speed sensor. The speed sensor is suitable for generating speed data for frequency analysis. The present invention may also utilize other types of sensors capable of generating data translatable into the frequency domain. The frequency analysis can then be used to diagnose any problems with the valve actuator or any other rotating device. In one embodiment, the rotary encoder is an absolute encoder with dual sensor pairs.

In the figures, like reference numerals designate like elements. 1 shows an embodiment of a rotary encoder of the present invention. The rotary encoder 1 represents a special embodiment of an absolute encoder. The terms “wheel” or “wheels” without a modification such as “input”, “clocking” or “encoding” can mean an input wheel 10, a timing wheel 20 and coding wheels 30 to 110 be. The term “coding wheel” or “coding wheels” refers to coding wheels 30 to 110.

A lower mounting frame 130 is secured to a lower board 120 by bolts 132. The bolts 132 may also be rivets, screws, clamps, clips, adhesives, spot welds, a snap fastener, or any other fastener known in the art. The bolts 132 can be attached anywhere. For example, if the bolt 132 is a clamp, the lower mounting frame 130 may extend to the edge of the lower board 120 and the bolt 132 may be located at that edge. Alternatively, if the bolt 132 is an adhesive, the adhesive may be spread over any surface of the lower mounting frame 130 that is in contact with the lower board 120.

The bottom board 120 may include a semiconductor substrate on which electrical components such as a processor 150 and a sensor 160 may be integrated together. However, rather than integrating the circuits into the bottom board 120, the circuits may be positioned outside of the bottom board 120. For example, holes may be drilled in the bottom board 120 that correspond to the inputs and outputs of the sensor 160 and the inputs and outputs of the processor 150. The insulated wires may be interconnected between the sensors 160 and the processor 150. Additionally, if a circuit is positioned outside of the lower board 120, it may be desirable to integrate the lower mounting rack 130 into the lower board 120.

The encoder 1 may also include an upper mounting frame 140 and an upper board 170 as shown in FIG 2 until 4 shown. The same description regarding the lower board 120 and the lower mounting frame 130 applies to the upper mounting frame 140 and the upper board 170. The top board 170 can also be a semiconductor substrate. However, any circuitry may also be external to the top board 170. The upper mounting frame 140 can be integrated within the upper board 170. The upper mounting frame 140 can be secured to the lower mounting frame 130 by bolts 132. A lock nut 122 is attached to the lower board 120. The upper board 170 is secured to the lower board 120 by a screw 172 and by the lock nut 122, as shown in 2 shown. The rotary encoder 1 can be secured to another device by fastening bolts 124. The designs described with respect to bolts 132 may also utilize locknuts 122, screws 172, and mounting bolts 174. Like in the 3 and 4 As shown, the upper mounting frame 140 may be a single piece of material. This is allowed in the 3 and 4 shown embodiment of the upper mounting frame 140 to thermally expand in a uniform manner. The same applies to the lower mounting frame 130. In an alternative embodiment, the upper mounting frame 140 and the lower mounting frame 130 can be made from several pieces.

In addition, the rotary encoder 1 is not limited to a particular shape. The rotary encoder 1 can be circular, rectangular or specially shaped for a particular device or application. The terms “top” and “bottom” are only used here to simplify the description of the rotary encoder 1. Accordingly, the rotary encoder 1 can be used in any orientation.

In the particular example of 1 until 4 The input wheel 10 includes teeth 12 on the gear 11. The input wheel 10 also includes an opening 14 which is used with sensors to provide a means for tracking the number of rotations of the input wheel 10. A closure cap 16 is attached to the input wheel 10. As in 3 shown, when the cap 16 is in place, any movement of the input wheel 10 is limited by the contact of the cap 16 with the upper mounting frame 140. The closure cap 16 can be included whenever the encoder 1 is moved or transported and then removed again when the input shaft is ready to engage the encoder 1.

A timing wheel 20 includes a gear 21 and a pinion 25. The gear 21 includes teeth 22. The pinion 25 includes teeth 26. The timing wheel 20 also includes timing marks 28. In this embodiment, the timing marks 28 are shaped as holes extending from the upper surface of the gear 21 to the lower surface of the gear 21, and the timing marks 28 are shaped as arc portions which appear to be rectangular . However, it is understood that these elements can take any form. The timing marks 28 may also be drawn lines, embedded magnets, or any other structures that can be detected. The timing markings 28 can also not be present and other devices can take over the function of the timing markings 28 instead. For example, the teeth on the gear 21 may be made of a ferrous component and include a sufficient number to correspond to the desired timing markings. A magnetic pick-up is located near the gear 21 and can sense each tooth 22 rotating proximal to the magnetic pick-up. The timing wheel 20 represents only one embodiment of a timing mechanism that may be used with the present invention.

The timing wheel 20 also includes encoder sections 24, which in the present invention are designed as arcuate holes extending from the top surface of the pinion 25 to the bottom of the gear 21. 1 shows coding sections 24 as ending in straight edges in a line with rays that extend radially from the center of the timing wheel 20. The coding sections 24 may also be arcuate sections ending in concave edges similar to the concave column 134 and column 144. The coding sections 24 are shown as dividing the inner ring 27 of the timing wheel 20 into eighths. However, the coding sections 24 may be designed to divide the inner ring 27 into halves, quarters, sixteenths or any other 1/2 ⁿ division.

In the embodiment shown the 1 The coding wheel 30 includes a gear 31 which includes teeth 32 and a pinion 35 which includes teeth 36. The coding wheel 30 has an inner ring 37 which includes the coding section 34 and an outer ring 39 which includes the coding section 38. The encoder sections 34 and 38 extend from the upper surface of the encoder wheel 30 to the lower surface of the wheel 30. The encoder sections 38 have a continuous arcuate shape that occupies one half of the outer ring 39. The encoder section 34 includes two distinct arcuate sections, section 34a and section 34b, each occupying a quarter of the inner ring and equally spaced from one another. Section 34a begins with the same radial ray as the encoding section 38. Section 34b begins with the same radial ray where the encoding section 38 ends. The coding sections can be asymmetrical, as in 1 shown, or symmetrical, like that Coding sections in 5 . Asymmetrical orientation of the coding sections may facilitate positioning of redundant sensors on the lower board 120 in locations that are not blocked by non-coding section portions of the coding wheels.

The encoding wheel 40 includes a gear 41 including teeth 42 and a pinion including teeth (not shown). The pinion is mounted on the underside of the coding wheel 40 and is not shown in the figures. The encoding wheel 40 has an inner ring 47 which includes an encoding section 44 and an outer ring 49 which includes the encoding section 48. The encoder sections 44 and 48 extend from the upper surface of the encoder wheel 40 to the lower surface of the wheel 40. The encoder section 48 includes a continuous arcuate section which occupies one half of the outer ring 49. The encoder section 44 is divided into two arcuate sections, sections 44a and 44b, each of which occupies a quarter of the inner ring and are equally spaced from each other. Section 44a begins at the same radial ray as the encoding section 48. Section 44b begins at the same radial ray at which the encoding section 48 ends.

In the present embodiment, the encoding wheels 50, 70, 90 and 110 are identical to the encoding wheel 30, and the encoding wheels 60, 80 and 100 are identical to the encoding wheel 40. However, it is not necessary that any of the encoding wheels is identical to another coding wheel. When the terms “inner ring” or “inner rings” are used, reference is made to the inner rings 37, 47, 57, 67, 87, 97, 107 and 117 of each of the coding wheels 30 to 110. Only the inner rings of the timing wheel 20 and the coding wheels 30 and 40 are in 1 clearly marked. When the terms “outer ring” or “outer rings” are used, reference is made to the outer rings 39, 49, 59, 69, 79, 89, 99, 109 and 119 of each of the coding wheels 30 to 110. Only the outer rings of the coding wheels 30 and 40 are in 1 clearly marked. When the terms “coding section” or “coding sections” are used, reference is made to coding sections 24, 34, 44, 48, 54, 58, 64, 68, 74, 78, 84, 88, 94, 98, 104, 108, 114 and 118 of the timing wheel 20 and each of the encoding wheels 30 to 110 are referred to. Only the coding sections of the timing wheel 20 and the coding wheels 30 and 40 are in 1 clearly marked. Additionally, the timing marks 28 can be viewed as “encoding sections”. The data generated by the timing markings 28 is used for both position determination and/or speed determination. Likewise, the data generated by the other coding sections can be used for both position and/or speed determination.

The gear 11 of the input wheel 10 interacts with the pinion 25 of the timing wheel 20. The gear 21 of the timing wheel 20 interacts with the gear 31 of the coding wheel 30. The pinion 35 of the coding wheel 30 interacts with the gear 41 of the coding wheel 40. The pinion 45 of the coding wheel 40 interacts with an intermediate pinion 180. The intermediate pinion 180 interacts with the gear 51 of the coding wheel 50. The pinion 55 of the coding wheel 50 interacts with the gear 61 of the coding wheel 60. The pinion 65 of the coding wheel 60 interacts with the intermediate pinion 180. The intermediate pinion 180 interacts with the gear 71 of the coding wheel 70. The pinion 75 of the coding wheel 70 interacts with the gear 81 of the coding wheel 80. The pinion 85 of the coding wheel 80 interacts with the intermediate pinion 180. The intermediate pinion 180 interacts with the gear 91 of the coding wheel 90. The pinion 95 of the coding wheel 90 interacts with the gear 101 of the coding wheel 100. The pinion 105 of the coding wheel 100 interacts with the intermediate pinion 180. The intermediate pinion 180 interacts with the gear 111 of the coding wheel 110.

As in 3 As can be seen, the gears of the input wheel 10 and the coding wheels 40, 60, 80 and 100 are in the same location as the pinions of the timing wheel 20 and the coding wheels 30, 50, 70, 90 and 110. The pinions of the coding wheels 40, 60, 80 and 100 are in the same location as the timing wheel 20 gears and the coding wheels 30, 50, 70, 90 and 110.

Lightweight protective covers (not shown) may protrude from the lower mounting frame 130 and the upper mounting frame 140. The protective cover is arranged in a partial or fully concentric ring between the inner and outer rings. For example, in the coding wheel 30, the protective cover is located between the inner ring 37 and the outer ring 39. The protective cover can be designed to have different heights depending on the distance between the lower surface of the timing wheel 20 and the coding wheels 30 to 110 on one side and the lower fastening frame 130. The protective cover provides a light barrier between the sensors 160. The protective cover Coverage may include concentric rings built into the lower mounting frame 130 built into the coding wheels and timing wheel 20, or may be built into the lower board 120 and upper board 170. Alternatively, barriers can be built around the individual sensors 160 or around the detectors 162 and the emitters 164. The protective covers may be concentric fin rings, walls, or any other structure capable of preventing crosstalk between different sensors 160.

The interaction of the input wheel 10, the timing wheel 20 and the coding wheels 30 to 110 is in the 1 until 4 shown as a serpentine figure. However, this design can be varied to suit different encoder designs. For example, if the encoder 1 is desired to be a circle, the wheels can then be arranged in a spiral configuration. Various shapes of the rotary encoder 1 and numerous designs of the wheels are possible. 5 shows an alternative U-shaped design of the wheels within the same encoder shape.

The rotary encoder 1 can also be designed in a stepped structure. The input wheel 10, the timing wheel 20 and the encoding wheels 30 to 110 are in the 1 until 4 shown as arranged on a single level. Alternatively, the encoder 1 may be designed to include wheels at different levels. In 1 Each wheel is individually secured to the lower mounting frame 130. However, multiple wheels could be mounted on a single axle. In one embodiment, coding wheels 60 and 70, coding wheels 50 and 80, coding wheels 40 and 90, and coding wheels 30 and 100 could each be arranged on the same axle. The timing wheel 20 and the encoding wheel 110 may be arranged on the same axis. For an even narrower encoder, the wheels 40, 50, 80 and 90 could be arranged on the same axis and the encoding wheels 30, 60, 70, 100 and 110 could be arranged on the same axis. It will be understood that a variety of designs and combinations are possible.

The input wheel 10, the timing wheel 20 and the encoding wheels 30 to 110 are shown as spur gears. However, these gears can also be worm gears, bevel gears, angle gears, hypoid, rim gears, tooth and pinion and helical gears. The rotary encoder 1 shows an embodiment in which the encoding wheels have a rigid rotation. Alternatively, a wheel and pinion system could be used if the timing wheel 20 and the encoding wheels 30 to 110 do not have rigid rotation.

With reference to the special one in which 1 until 4 In the embodiment shown, the inner and outer rings of various coding wheels are arranged at the same distance from the center of the wheels. For example, the inner ring 37 and the coding portion 34 are the same distance from the center of the wheel 30 as the inner ring 47 and the coding portion 44 are from the center of the wheel 40, even though the wheel 40 has a larger diameter. Therefore, the number of teeth 42 and teeth 36 can determine the speed reduction of the wheel 40 to the wheel 30. The same applies to the other wheels. However, it is not necessary that the coding sections of the different coding wheels are arranged radially in the same way.

The speed of the input wheel 10 is determined by the speed of the rotating device to be monitored. For example, in the present embodiment, the timing wheel 20 rotates approximately 1.34 times faster than the input wheel 10. The encoding wheel 30 rotates at the same speed as the timing wheel 20. The encoding wheel 40 rotates a quarter of the speed of the encoding wheel 30. The encoding Wheel 50 rotates at a quarter of the speed of the encoding wheel 40, which rotates at a sixteenth of the speed of the encoding wheel 30. The same may apply to the other encoding wheels, so that the encoding wheel 110 rotates a quarter of the speed of the encoding wheel 100, which rotates at 1/65,536th the speed of the encoding wheel 30. In some scenarios, the encoding wheel will rotate, but not enough to trigger rotation of the encoding wheel 110. In alternative embodiments, additional encoding wheels can be added to the encoder 1. The speed of the additional encoding wheels can be calculated as 1/4 ⁿ of the encoding wheel 30 (counting the encoding wheel as n=o, the encoding wheel 40 as n=1,..., the encoding wheel 110 as n=8, etc.) be calculated. Certain embodiments of the invention may include an encoding wheel with a small number of bits for the highest speed wheel, but allow increasing higher numbers of bits per wheel as the relative encoding wheel speed decreases as the wheel train increases.

There may be situations where it is desirable to vary the number of teeth from wheel to wheel. For example, if the coding wheels 40 and 60 do not have the same number of teeth. Additionally, in conjunction with varying the number of teeth on a gear, the radial position of an encoder section relative to another gear can be varied to to produce a reduction or increase in speed.

The wheels can be made from any number of materials. A few representative examples include steels, stainless steels, aluminum, other metals, ceramics, plastics, glass and metal-covered plastics. Any gear material known in the art can be used. All wheels may be made of the same composition, or the compositions may vary between wheels.

As shown with respect to the encoding wheel 80, the sensor 160 includes detectors 162 and emitters 164. The detectors 162 and emitters 164 are built into the lower board 120. Columns 134 are built into the lower mounting frame 130 to prevent obscuration of the detectors 162 and emitters 164. With respect to the emitters 164 and detectors 162, they may be fabricated within the bottom board 120 via semiconductor manufacturing technologies, the emitters 164 and detectors 162 secured to the bottom board 120, and the emitters 164 and detectors 162 through holes in the bottom board 120 can be inserted. It is understood that any other way to secure the emitters 164 and detectors 162 to the bottom board 120 is also included in the present invention. Column 144 ( 4 ) are installed in the upper mounting frame 140 and have the same function as column 134. Although not shown, the encoder 1 may include sensors, including emitters and detectors, which are installed in the lower surface of the upper board 170. For each detector 162 installed in the bottom board 120, an emitter may be located directly above it. For each emitter 164 installed in the bottom board 120, a detector may be located directly above it. The column 144 in the upper mounting frame 140, in 4 shown prevent any blocking of the emitters and detectors by the upper mounting frame 140. The sensors, detectors and emitters located on the lower surface of the upper board 170 are typically identical to the sensors 160, emitters 164 and detectors 162 located located directly above it. Also, for ease of discussion, corresponding components located on the upper board 170, which are substantially the same as the components located on the lower board 120, although not shown in the figures, are given the same reference numeral followed by a Prime (') marking can be given (e.g. detector 162 and detector 162').

The embodiment shown includes sensors 160, 161, 163 and 165. The sensors 161 correspond to the inner rings of the timing wheel 20 and the coding wheels 30 to 110. The sensors 163 and 165 correspond to the outer rings of the coding wheels 30 to 110. The sensors 160', 161', 163' and 165' are located respectively directly above sensors 160, 161, 163 and 165. Sensors 163 and 165 may be located approximately 90 degrees radially apart from each other. In the coding wheels 30, 60, 70, 100 and 110, the sensor 161 can halve the angle between the sensors 163 and 165. In the coding wheels 40, 50, 80 and 90, sensors 161 and 163 may be approximately 45 degrees radially apart and sensors 161 and 165 may be approximately 135 degrees radially apart. The sensors 161, 163, 165 and 169 are numbered only in relation to the coding wheels 80 and 100 and the timing wheel 20. Each sensor 161, 163 and 165 includes an emitter 164 and a detector 162. Each sensor 161', 163' and 165' includes an emitter 164' and detector 162'.

The sensors 160/160', including the emitters 164/164' and the detectors 162/162' can be described as a set of sensor pairs or as a dual set of sensors. The same applies to the special shapes of the sensors 160/160' and 160'/160" (i.e. the sensors 161, 161', 163, 163', 165, 165', 169 and 169'). Instead of the emitter 164 and the detector 162 as a pair and the emitter 164' and detector 162' as an opposite second pair, the emitter 164 and detector 162' can be seen as a pair, and the emitter 164' and detector 162 can be seen as a parallel second pair can be seen. The second pair, however seen, can provide double sampling. This redundancy allows the encoder 1 to be highly fault tolerant. For example, if one of these pairs were to fail, the encoder 1 would still be operational. The Encoder can work with a variety of activated sensors depending on which, if any, sensor or sensor component may have failed.

In a particular embodiment, the location of an emitter 164 and a detector 162 of a sensor 160 is the location that gives the sensor 160 (and the corresponding sensor 160') the widest and most symmetrical offset tolerance possible. The locations where the code values change for a sensor leave as much room in the clockwise (CW) direction as in the counterclockwise (CCW) direction before the bit value will change again. This way is in 1 shown. In a special embodiment, this leads to asymmetrical sensor offsets with a corresponding asymmetry in the code change points.

In an alternative embodiment, an emitter 164 may be offset relative to a detector 162. The resulting first and offset encoded values can then be compared to ensure that the arithmetic difference between the two values is the same. If the arithmetic difference is not the same, the problem could be in the self-test described below.

In either embodiment, as long as the offset is within the limits of the v-bit anti-backlash logic and within the limits of the allowed mechanical tolerances of the components, the resulting codes will be identical.

In an alternative embodiment, sensors 161, 163 and 165 could each have a single emitter, and corresponding sensors 161', 163' and 165' could each have a corresponding single detector without any redundancy.

The various sensors are connected to timing marks 28. The sensor 169, in 1 shown includes at least one emitter 164 and at least one detector 162. Sensor 169', located on top board 170, is mounted directly above sensor 169 and includes at least one emitter 164' and at least one detector 162'.

In a special embodiment, the corresponding sensors are located on the lower 120 and the upper board 170 and can be activated simultaneously with a wheel. Alternatively, all or some of the wheels can be activated at the same time. The bottom of each wheel is typically activated first, followed by the top of each wheel. In a special embodiment, individual emitters of the sensors 160/160' can be activated. The various sensors 169/169' for monitoring the timing marks 28 are continuously activated, as described in detail below. With respect to the coding wheels 30 to 110, the emitters 164 of the sensors 161, 163 and 165 can be activated. If the rotary encoder 1 is in the in 1 position shown, then the detectors 162' of the sensors 161', 163' and 165' each receive a signal from the corresponding emitters 164. However, the rotary encoder 1 could be positioned so that only the detectors 162' of the sensors 161' and 163 ', 161' and 165', 163' and 165', 161', 163' and 165' or none of these sensors receive a signal. Regardless of the position of the encoder 1, the detectors 162 will receive a signal when the emitters 164 are activated. In a particular embodiment, the emitters 164 and the detectors 162 are capable of direct communication both vertically and laterally. Therefore, when three emitters 164 are activated, the three detectors 162 should receive a signal and the three detectors 162' can receive a signal when an opening in the encoder wheel (ie and the encoding section) between an emitter 164 and a detector 162' is arranged. Therefore, 6-bit data is generated.

In the same way, when the emitters 164' of the sensors 161', 163' and 165' located on the top board 170 are activated, 6-bit data is generated. The detectors 162' of the same sensor are activated, as are the detectors 162 of the sensors 161, 163 and 165 on the lower side of the rotary encoder 1. The sensors 161, 163 and 165 of the coding wheel 30 can be activated. Then the sensors 161', 163' and 165' of the coding wheel 30 can be activated. This pattern of alternative sensor activation may continue relative to the encoding wheels 40 to 110.

With respect to the timing wheel 20, the sensors 161 and 161' may be activated as described above with respect to the coding wheels 30 to 110. In a particular embodiment, the emitters of sensors 169 and 169' are continuously activated. In the in 2 In the embodiment shown, sensor 169' includes two emitters and sensor 169 includes two detectors. In a particular embodiment, all of the other sensors have both an emitter and a detector. In a particular embodiment, only one emitter of sensor 169 is activated at a time.

The first detector 162a and the second detector 162b can be positioned so that when a timing mark 28 is present over the first detector 162a, a timing mark 28 is not present over the second detector 162b. This is in 1 shown where detector 162a and an optional emitter 164 are visible, but detector 162b is not visible.

Alternatively, sensors 169 and 169' could each have both an emitter and a detector and the direct side-by-side transmission feature could be turned off. This feature could be turned off using another type of sensor or by placing a barrier around the edges of detectors 162 and 162' and/or emitters 164 and 164'.

Sensors 169 and 169' may also include other emitters and detectors. For example shows 2 an emitter 164 in a sensor 169, which a detector 162 'in a sensor would correspond to 169. The emitter 164 may be positioned a sufficient distance from the first detector 162a so that the first detector 162a does not receive a light signal when the emitter 164 is activated. In an alternative embodiment, the emitters 164, the first emitter 164a' and the second emitter 164b' may be activated alternately.

Sensors 160 and 160' provide three levels of redundancy. First, if any of the emitters 164' and 164 and the detectors 162' and 162 fail, the sensors 160 and 160' will still be operational. For example, should the emitter 164 of the sensor 161 of the coding wheel 80 fail, the sensor 161 will still be operational because the emitter 164' of the sensor 161' is still capable of communicating with the detector 162 of the sensor 161 .

A second level of redundancy is based on a built-in self-test function. Placing a detector 162 adjacent an emitter 164 allows for a self-test. Even if there is no clear light path due to the position of an encoding wheel, the detector 162 will receive a signal when the emitter 164 is activated. If detector 162 has not received a signal, then either or both of emitter 164 and detector 162 (or the associated circuitry and processing) are not functioning. Once an encoding wheel has been moved to a position where there is a clear light path, and if the detector 192 does not receive a signal, the emitter 164 is likely malfunctioning. The usefulness of detectors 162' and 164 can be determined by activating emitter 164'. The same logic applies if detector 162, detector 162', or emitter 164' begins to malfunction instead of emitter 164.

The processor 150 will consider any failed component, such as an emitter 164 or a detector 162', once it is determined which position was identified by the sensors 160 and 160'. For example, if the detector 162 of the sensor 163 adjacent to the coding wheel 80 were to fail, the processor 150 can then compensate for this if the sensors 163 and 163 'do not detect a blocked light path in the same rotation point of the coding wheel 80. Alternatively, using the same example, if detector 162 is not receiving a signal, detector 162 may be tested by adjacent emitter 164 to determine whether detector 162 is operational. The emitter 164' can be tested by the adjacent detector 162 to determine whether the emitter 164' is the source of the problem. If the emitter 164' and detector 162 are operational, and the emitter 164' is transmitting but the detector 162 is not receiving the transmission, then the outer ring 89 blocks the light path between the emitter 164' and the detector 162. Even if the detector 162 has failed, the processor 150 can then evaluate the position of the coding wheels 30 to 70 and 90 to 110 to determine whether the outer ring 89 is actually blocking the failed detector 162.

A third redundancy may be provided by each of sensors 160 and 160' using Viterbi decoding. For example, either the output of sensor 163 or sensor 165 can be used to generate a Viterbi bit (v-bit). If a sensor 160 or a sensor 160' is not operating to generate a v-bit, then the sensor 160 or 160' is used to generate a data bit. In a particular embodiment, sensors 165 and 165' are used to generate the v bit. The Viterbi decoding algorithm is an advanced error correction technology. The v bit provides redundant data that can be used to decode the positions of the other 2 bits. In this embodiment, sensors 161 and 161' may provide 1-bit data and sensors 163 and 163' may provide the second bit of data. By using a v bit, the angular offset of the signals generated by sensors 161 and 161' and by sensors 163 and 163' can deviate more than +/- 22.5 degrees from the optimal position without causing an encoding error. Therefore, even if a signal is received with an offset, the true position of the wheel can still be determined. The v bit on an encoding wheel also clarifies the true position of an adjacent encoding wheel. For example, the v bit of the encoding wheel 30 helps clarify the true position of the encoding wheel 40.

Viterbi decoding is not the only decoding algorithm that the encoding wheels 30-110 may be designed to implement. Other suitable algorithms for use with the present invention include, for example, sequential decoding, Reed-Solomon coding and turbo coding. Another alternative to Viterbi decoding is gear counting.

In the encoder 1, the sensors 165, which generate the v-bits, are offset from the sensors 161 and 163. Alternatively, sensor 165 may be arranged in line with data bit producing sensor 163 or 161. 5 shows an embodiment of an absolute encoder ( 5 : rotary encoder 2), with the v-bit sensor 2165 positioned in a row with a data bit sensor 2161 and is offset by a data bit sensor 2163. As seen with respect to timing wheel 2020, v-bit sensor 2165 may also be positioned to sense encoder portion 2034 on inner ring 2027. The v-bit sensors 2165 may be positioned to sense the inner rings for any or all of the coding wheels 2030 to 2110. Therefore, the sensors 161 or the data bit sensors 2161 may also be a v-bit.

The rotary encoder 2, shown in 5 , works like encoder 1, except for a few differences. The 2010 input wheel has a different number of teeth. The coding section 2024 divides the inner ring 2027 into halves rather than quarters. In addition, a sensor 2165 is inserted into the same concentric ring as a data bit sensor 2161. The timing wheel 2020 includes a pinion 2025 on the side, which is an intermediate pinion 2180.

The coding wheel 2030 includes the gear 2031 with teeth 2032 and the pinion 2035 with teeth 2036. The encoding wheel 2030 includes an inner ring 2037 which includes an encoding section 2034 and an outer ring 2039 which in turn receives the encoding section 2038. The encoder sections 2034 and 2038 extend from the upper surface of the encoder wheel 2030 to the lower surface of the wheel 2030. The encoder section 2038 is shown as a continuous arcuate section occupying one half of the outer ring 2039. The encoder section 2034 includes two distinct arcuate sections, section 2034a and section 2034b, each of which is shown occupying a quarter of the inner ring and are equally spaced apart. The middle part of section 2034a is in line with the middle part of encoding section 2038. Section 2034b occupies the space directly opposite section 2034a.

The coding wheel 2040 includes a gear 2041 with teeth 2042 and a pinion 2045 with teeth 2046. The pinion 2045 is attached to the bottom of the coding wheel 2040. In the embodiment of 5 the pinion 2045 is visible through the coding wheel 2040. The encoding wheel 2040 has encoding sections 2044 and 2088 similar to the encoding wheel 2030. For the description, only the coding sections of the timing wheel 2020 and the coding wheel 2030 are included 5 designated.

The coding wheels 2050, 2070, 2090 and 2110 may be identical to the coding wheel 2030. The coding wheels 2060, 2080 and 2100 may be identical to the coding wheel 2060. The terms “inner ring”, “inner rings”, “outer ring”, “outer rings”, “coding section” and “coding sections” are used to describe the rotary encoder 2 of the 5 in the same way as the encoder 1.

The input wheel 2010 works together with the intermediate pinion 2180, which in turn works together with the pinion 2025 of the timing wheel 2020. The pinion 2025 works together with the intermediate pinion 2180, which in turn works together with the gear 2031 of the coding wheel 2030. The pinion 2035 of the coding wheel 30 cooperates with the gear 2041 of the coding wheel 2040 and so on up to the coding wheel 2110. The coding wheels 2030 to 2110 act in the same way as the coding wheels 30 to 110.

In the present embodiment, the teeth of the input wheel 2010 and the gears of the coding wheels 2030, 2050, 2070, 2090 and 2110 may be designed to lie in the same plane as the pinions of the timing wheel 2020 and the coding wheels 2040, 2060, 2080 and 2100. The pinions of the coding wheels 2030, 2050, 2070, 2090 and 2110 may be arranged in the same plane as the gears of the coding wheels 2040, 2060, 2080 and 2100. The pinions of the coding wheels 2030, 2050, 2070, 2090 and 2110 can be arranged in the same plane as the gears of the coding wheels 2040, 2060, 2080 and 2100.

With respect to the encoder 1, the sensors 160 and 160' provide an indication of the absolute position of the input shaft that rotates the input wheel 10. As shown, encoder 1 is an 18-bit absolute encoder. Therefore, the encoder 1 is able to designate 262,144 positions. Of course, not all of these positions need to be used. The encoder 1 can be scaled up or down by adding or subtracting wheels and sensors to or from the end of the string. Three sets of sensors 160 and 160' can be provided via a wheel. Alternatively, only one or two of the sets of sensors 160 and 160' may be provided per wheel or on the last wheel in the chain, as long as the sensors are positioned to act as the no larger magnitude bits in the encoded value. The rotary encoder 1 can also have only a single coding wheel, which serves as both a source of speed and position data. The rotary encoder 1 can therefore only have a single position-encoding wheel and a single speed-sensing mechanism, such as a timing wheel. In addition, each of the encoding wheels may have a number of encoding sections and corresponding ones Sensors 160 and 160 'have. The rotary encoder 1 can be of any encoder form that uses the sensors 160 and 160'.

As described above, the sensors 160 and 160' are capable of communicating when an encoding section is disposed between the sensors, thereby providing a clear light path. In sensors 160, detectors 162 output a logic 0 value when a signal is received and output a logic 1 value when no signal is received. Similarly, detectors 162' in sensors 160' output a logic 0 value when a signal is received and output a logic 1 value when no signal is received. Therefore, when an encoding section is between the sensor 160 and the sensor 160' when the emitter 164 is activated, the processor 150 receives two separate logical inputs: an input from the detector 162', which senses position, and an input from the detector 162, which carries out a self-test. Once emitter 164 is turned off and emitter 164' is activated, processor 150 then receives two individual logic inputs: a logic input from detector 162 sensing position and a logic input from detector 162' performing a self-test.

If an inner or outer ring blocks communication between sensors 160 and 160', processor 150 will then receive a logical 0 input corresponding to a bit value in the position code and a logical 1 input indicating a successful test of a Emitter in connection with this bit position represents. For example, if emitter 164 is activated, detector 162' will be blocked from receiving a signal and a logic 1 will be transmitted. The detector 162 will still receive a signal through a direct side-by-side transmission, and therefore transmit a logical o to the processor 150.

If the processor 150 receives logic o signals from a detector 162' and an opposing emitter 164 is activated, then the processor 150 recognizes that an encoding section must be present. The same result is achieved when an emitter 164' is activated and a detector 162 sends logic o signals. The present embodiment uses o and logic o signals, but 0 and 5 volts, 1 and 5 volts, or any other common sensor signals or combinations thereof may also be used. Additionally, detectors 162 and 162' may be configured to generate a logic 0 whenever a light signal is not received and 0 volts are generated whenever a light signal is received. In such an embodiment, a processor 150 would receive an indication of an encoding section between sensors 160 and 160' when 0 volts are received from detector 162' and emitter 164 is activated.

In a particular embodiment, the self-test of an adjacent detector 162 is performed by an emitter 164 through direct transmission from the emitter 164 to the detector 162. For example, detector 162 may be located 0.5 mm from emitter 164. Alternatively, sensors that are not suitable for direct side-to-side transmission can be used. In such an embodiment, a self-test can be performed by reflection. For example, if an encoding section is present between sensors 160 and 160' and emitter 164 is activated, only detector 162' would receive a signal. If emitter 164' is activated, only detector 162 would receive the signal. This would allow both emitters 164 and 164' to be activated at the same time. If an encoding section is not present such that light would be blocked between sensors 160 and 160', detectors 162 and 162' may be adapted to receive reflected light signals. In this scenario, when emitter 164 is activated, light may be reflected from the bottom surface of an inner or outer ring. The detector 162 can receive a portion of the reflected light. The detector 162 may be configured to transmit a logic 0 when no light is received. The detector 162 may be designed to transmit a voltage that is comparable to the intensity of the received light. Therefore, if an encoding section is present, the detector 162 can then receive a direct, relatively high intensity light signal from the emitter 164' located directly above the detector 162. When no encoding section is present, the detector 162 may receive a relatively low intensity reflected light signal from the adjacent emitter 164.

In another embodiment, the coding portions may be drawn on the wheels rather than relying on cut-out portions in the wheels. In such an embodiment, no communication occurs between sensors 160 and 160'. Instead, detector 162 receives reflected light from emitter 164. The same applies to detector 162' and emitter 164'. For example, if the wheels are non-reflective (e.g. painted black) and the encoder sections are reflective (e.g. painted white), or vice versa, then the detector 162' will produce a voltage when light is reflected from the encoder sections and a different voltage when light is reflected from a non-coder section is reflected. Additionally, sensors 160 and 160' may be located on the same side of an encoding wheel.

Sensors 160 and 160' have been described in relation to optical sensors. However, it will be understood that many other sensors can be used with the invention. Suitable examples of sensors include, without limitation, magnetic sensors, Hall effect sensors, and electrical contacts. Any sampling known in the art for incremental and absolute encoders can be used with the present invention. Encoding sections may also include any material or design compatible with the selected sensor.

The processor 150 can also be designed to generate alarms. If a detector 162, an emitter 164, a detector 162', an emitter 164', a detector 162a, a detector 162b, an emitter 164a' or an emitter 164b' should fail, the processor 150 may enable an alarm to be issued. Varying alarms can be provided for different levels of failure priority. In extreme situations, the processor 150 may be designed to force the shutdown of the valve actuator or other rotary device monitored by the rotary encoder 1. Alarms can be expressed in a variety of ways, such as visual alarms (such as a flashing light or LCD message on a valve actuator control panel or at a control station), audible alarm, or written warnings.

In the sensor 160 and 160', if the emitters 164 and 164' and the detectors 162 and 162' are not functioning properly, the generated data bit or v-bit is then declared invalid. Invalid bit values can be judged by their influence on the performance of the valve actuator or other rotating device, which is judged by the rotary encoder 1 based on the decoded value of the fallen bit and the lead time. Invalid bit values can also be judged based on the number of bits that failed.

The lead time for a valve actuator is the time it takes for it to move from an open position to a closed position or vice versa. The lead time for the other rotating device is the time required for the rotating device to move from a first position to a second position. For example, for an industrial spool, lead time is the time it takes the spool to go from fully wound to fully unwound. If the lead time is long, a single bit represents only a small percentage of the total lead time. Therefore, a single bit failure is unlikely to be critical and providing an alarm or warning just before a machine is forced to shut down may be sufficient for such an application. If the lead time is short, a single bit failure can indicate a large deviation between the current position and the position indicated by the encoder 1. Therefore, for short lead times, a single bit failure may be sufficient to force shutdown of the rotator in addition to providing an alarm or warning. The significance of a bit failure may depend on what portion of the lead time is represented by the bit failure for a given application. In a particular embodiment, the user may be able to design the permissible loss of accuracy threshold below which the BIST feature would be more likely to trigger an alarm or warning, but beyond which the BIST feature would force a safe shutdown of the machine , and would also issue an alarm or warning.

For a rotating device that does not have a predetermined first and second position, the lead time cannot be specified. Examples of such a rotating device include the flywheel of an engine or the main shaft of a turbine. A rotary encoder of the present invention can be used with any type of rotary device as well.

As previously mentioned, if both detectors 162 and 162' of sensors 160 and 160' have been verified as operational through self-tests, but detector 162 is not receiving a signal, with detector 162' receiving a signal, then a check of the positions of the other wheels can be made be used to confirm the position of the wheel in question. In this scenario, the data bits generated by sensors 160 and 160' are actually valid, but half of the sensors 160 and 160' are blocked by an inner or outer ring. The Viterbi logic operations may obtain the identical position code of either the first or redundant sensor set (i.e., emitter 164 or detector 162). It will be understood that the terms “first” and “second” or “redundant” are arbitrary.

Alternatively, the sensors 160 and 160' may be fully functional, but another component of the encoder 1 has failed. For example, if one of the teeth on a coding wheel shears, the current position indicated by sensors 160 and 160' may not match the position indicated based on the previous position indicated by sensors 160 and 160' provided data is accepted. Therefore, while the sensors 160 and 160' function properly, they do not indicate the correct position. The processor 150 or any other processor can correct this error and trigger an alarm. For example, if the coding wheel 60 were to lose a tooth 62 from the gear 61, the coding wheel 60 may begin to miss positions during each rotation. Therefore, the valve position indicated by the coding wheels will no longer correspond precisely to the valve position. It will appear as if the valve has jumped to a different position. In one embodiment, processor 150 may search for discontinuities in valve position indicated by the positions of the encoding wheels. Alternatively or additionally, the timing wheel 20 may be used as an incremental encoder to verify the position of the encoding wheels. The processor 150 (or any other suitable processor) may then recalculate the valve position taking into account the error introduced by the encoding wheel 60. The processor 150 could also trigger an alarm and/or trigger a safety shutdown if the failure has reached a serious level.

Any failure of the encoder 1, which results in a more discontinuous indication of the valve position, can be identified by the processor 150, or by any other processor in communication with the processor 150.

Sensors 160 and 161' have been described herein as each including both an emitter and a detector. Alternatively, the sensor 160 may be designed to include only one emitter and the sensor 160' may be designed to include only one detector. In other embodiments, the sensor 160' does not need to be present in the encoder 1. 2 shows a sensor 160 with multiple emitters and detectors. The sensor 169 includes an emitter 164, a first detector 162a and a second detector 162b. Although not shown, sensor 169' includes a corresponding detector 162', a first emitter 164a' and a second emitter 164b'. The second detector 162b and the second emitter 164b can be used to verify the data from the first detector 162a and the first emitter 164a', or to effectively double the data output generated by the sensors 169 and 169'. Sensors 160 may include any number of emitters, detectors, and/or both. Sensors 160 and 160' can be used with any encoder to provide fault-tolerant speed and position data.

The 1 until 5 show an absolute encoder, with each of the encoding wheels having only an inner ring and an outer ring. However, each of the encoding wheels may have any number of rings without limitation. For example, each coding wheel could have 3, 4, 5 or 6 rings. At least one sensor 160 and at least one sensor 160' could be provided for each ring. Therefore, the number of rings would determine the number of data bits that could be generated per encoding wheel.

The number of rings per encoding wheel is governed by the size of the encoding wheel and the width of the encoding sections needed to allow sensors 160 and 160' to communicate with each other. Additionally, a sufficient gap should be provided between the rings to limit crosstalk between sensors on the same side. For example, a gap is provided to prevent a detector 162 of a sensor 161 from registering a signal from an emitter 164 of a sensor 163. However, technologies other than the column, such as the use of the masking guard discussed above, can be used to limit crosstalk and allow for smaller encoder wheel diameters.

Any number of encoding wheels can be added to the encoders of the present invention. For example, the rotary encoder 1 can provide position data from a common speed valve actuator with a lead time of one hour. Adding multiple encoder wheels would provide multiple bits of data and increase the lead time that can be achieved with encoder 1. Of course, the rotary encoder 1 can also be used with valve actuators or other rotary devices that have a lead time of less than an hour. The rotary encoder 1 can also have fewer coding wheels than the one in 1 until 4 have shown.

In addition, the rotary encoder 1 can be a single-wheel absolute encoder or a single-wheel incremental encoder. In those embodiments, sensors 160 and 160' may include multiple emitters and detectors, thereby providing built-in self-test and fault-tolerant operation. Therefore, a set of sensors 160 and 160' may monitor multiple coding sections, such as timing marks 28 or coding section 34, or a set of sensors 160 and 160' may monitor a single coding section, such as coding section 38.

In addition, the timing wheel 20 can be used as an incremental encoder in connection with the absolute encoding functions of the remainder of the encoder 1. For example, a particular incremental encoder embodiment may be scaled such that the incremental pulse rate exactly matches the count rate of the encoder's absolute section. In this way, the incremental encoder could be used to obtain position data while the actuator is operating. When the motor stops, the final incremental number added to the absolute position code at the start of monitoring should exactly equal the new absolute coded position.

If the position designated by the timing wheel 20 (also acting as an incremental encoder) deviates from the position designated by the encoder wheels, then a self-test of the sensors 160 and 160' may be performed. If a self-test confirms that all sensors 160 and 160' are functioning properly, then it is likely that an encoding wheel is not following properly. Therefore, alarms or warnings can be generated. In a particular embodiment in that scenario, a rotary encoder may depend on the incremental encoder until the rotary encoder is repaired.

Encoders 1 and 2 are designed to use Gray coding, but binary coding can also be used. The use of v-bits and dual sensors allows encoders 1 and 2 to never deviate by more than the least significant bit (LSB), increasing the user's confidence in the reliability of the encoder values.

The present invention can be used with a variety of rotating devices that rotate between two positions, such as a valve actuator, a door opener, or a spool. In a typical valve actuator, an electric motor may drive the valve via a set of gears. The motor's output shaft may be directly coupled to a worm. The worm may drive a worm wheel assembly, which in turn drives a drive sleeve or shaft, which in turn raises and lowers or rotates a valve stem. A second shaft may also be driven by the worm wheel assembly to drive the input wheel 10 of the encoder 1. Alternatively, the valve actuator may use a different gear set, or the output shaft of the electric motor may be coupled directly to the valve stem without an intermediate gear set. There are many ways known in the art to connect rotary position encoders to rotating devices that can be used with the present invention, but are not discussed here. In a preferred embodiment, the rotating encoders 1 and 2 can be used to perform diagnostics of rotating devices, such as valve actuators. With regard to the diagnostic function, the rotary encoder 1 is used as an illustrative example. However, other encoders of the present invention, such as a rotary encoder 2, can also be used. Additionally, a timing wheel 20 could be included in each encoder. The timing wheel 20 could be the encoding wheel of an incremental encoder or a single-wheel absolute encoder. For example, the timing markings 28 can also be used for position coding of an absolute encoder. Alternatively, as in 1 As shown, the timing wheel 20 may also include coding sections separate from the timing marks 28. In another embodiment, the timing marks 28 may be part of a larger encoding pattern, such as the encoding pattern of a single-wheel absolute encoder. In a particular embodiment, the timing wheel 20 may be an incremental encoder separate from or in conjunction with other encoder wheels. In this embodiment, timing marks 28 are used not only to generate velocity data, but also to generate incremental position data. The timing marks 28, like the encoding sections, may take any shape or structure to cooperate with the sensors 160 and 160'. The timing marks 28 may be holes, lines, embedded magnets, engravings, or other structures known in the art for use with an absolute or incremental encoder.

The timing wheels 20 and 2020 are shown with thirty-two timing marks 28 and timing marks 2028, respectively. However, the timing wheels 20 and 2020 may have any number of timing marks 28.

With respect to frequency analysis, a particular embodiment of performing frequency analysis (also referred to herein as frequency domain analysis) of velocity data is discussed in principle below, followed by discussion of non-velocity data embodiments. Additionally, for purposes of illustration, the timing wheel 20 or the timing marks 28 of the timing wheel 20 are often referred to herein as the source of the velocity data. In other embodiments, any type of speed sensor, with or without rotational position encoders, may be used for diagnostics (ie, frequency analysis). Additionally, the discussion regarding frequency analysis of velocity data applies to the other data embodiments as well applicable. Other embodiments of data may include, for example, torque data, position data, thrust data, acoustic noise data, current data, voltage data, motor power data, motor volt-ampere feedback data, and vibration data. Many types of data and types of sensors can be used in frequency analysis that are known in the art. The invention covers any type of data that can be generated by sensors and a valve actuator or other rotating devices.

Although the following discussion includes an encoder 1, it will be understood that the same discussion applies to the encoder 2 5 applies. The timing marks 28 on the timing wheel 20 can be used to generate speed data. The sensors 169 and 169' can record the length of time that each of the timing marks 28 appears before the sensors. This hold time can then be used to precisely determine the speed of rotating devices such as valve actuators. The speed data can be used to determine the speed of an input wheel 10 driving the input shaft. Often the input shaft is in turn attached to other rotating devices, such as the worm wheel of a valve actuator. Therefore, the timing marks 28 can be used to determine the speed of another rotating device, such as a worm wheel.

In a particular embodiment, the timing marks 28 are designed as evenly spaced and uniformly sized holes in the timing wheel 20. However, each of the previously discussed encoder section embodiments and sensor embodiments is also applied to the embodiments of timing marks 28 and embodiments of sensors 169 and 169', respectively.

The velocity data generated by the timing marks 28 can be processed with an FT to convert the velocity data from a time domain to a frequency domain. However, any type of speed sensor can be used to generate the speed data for conversion to frequency data.

FT expects signal examples to occur at regularly spaced time intervals. However, since the hold time values for the velocity signals cannot be constant in this invention, a means may be used to allow the FT to obtain useful information. By selecting a sufficiently large number of data points, the vast majority of which are taken while the machine is operating in a steady state, the average hold time of the large data can be used as the “regular” hold time [t _d ] for each data sample. This “regular” hold time can be used to scale the frequency scale of the resulting FT. (f _n (Hz)= 1 _/ (t _d * # samples). When the frequency data is properly scaled, a user is provided with data with sufficient information to determine the variations in speed associated with the known rotational speeds of the various components of the drive train and may indicate existing or lurking problems in the drive train of a valve actuator or other rotary device. For example, a baseline frequency versus amplitude image or graph could be generated and stored when the device is new. New ones could be created later Frequency versus amplitude images or graphs are generated and compared with the stored baseline image or graph. If a peak corresponding to an operating frequency of a given component should occur at a frequency or amplitude different from that previously measured, it then becomes clear that the component In connection with this frequency, it is determined differently than when new, which usually indicates wear and possible failure or failure that has occurred. Therefore, appropriate maintenance can be performed at an appropriate time before the component fails. Additionally, an FT analysis could be scheduled to run automatically in the processor 150, which would be programmed or designed so that a change in the amplitude of a peak above a set threshold to generate an automatic alarm or warning or force a safety shutdown of the machine can be used. Any method for properly scaling frequency data as in the prior art can be used.

Examples of frequency domain analysis are in the 6 until 8th locked in. 6 shows an example of a clean diagnosis in the frequency range for a valve actuator or a “good” drive. 6 shows a peak at 45.9 Hz; however, the peak, measured at 0.1% relative to the actuator operating speed (100% magnification at 26 rpm or 0.43 Hz), is not a sufficient magnitude to cause concern. 7 shows an example of a valve actuator that produces some different signals in the frequency range or a “bad” actuator. The frequency of the aberrant signal can be used to identify the problematic powertrain component. In 7 is a worm shaft or worm wheel outside of tolerance. For example, the peak at 26.1 Hz indicates a problem. However, the peaks at 52.5 Hz and 78.6 Hz are overtones of the 26.1 Hz peak.

The processor 150 or the processor performing the FT may be designed to automatically generate the appropriate markers for peaks that are significant (e.g., above a certain threshold). For example, the processor may include a program designed to combine recently generated peaks with the amplitude and frequency of recently generated peaks. In this embodiment, if the processor is unable to identify a peak, such failure may serve as a warning to a user of a potential problem. Alternatively, the data in the frequency domain can be manually correlated with parts of a drive train of the valve actuator. A user may be trained to identify and understand the relevance of the various peaks. For example, if a rotary encoder 1 is present in a valve actuator, the timing wheel 20 and sensors 169 and 169' can then be used to identify the speed of a drive train component. In a special embodiment, the input shaft, which drives the input wheel 10, is in turn driven by a worm wheel. Therefore, the speed sensor can be used to determine the speed and consequently the frequency of the worm wheel. Then, based on the gear ratios, the frequencies of the other drivetrain components can be calculated. The component frequencies and any overtones could then be identified in a graphical representation of the data in the frequency domain. On the other hand, if a speed sensor is not present in the valve actuator but the current motor shaft speed is known, the information can be used to generate component frequencies. Various types of electrical or magnetic measurements of the current speed of the motor can be used, thus improving the diagnostic ability of the system as a whole. In many cases, factory personnel could perform the above manual identification. Therefore, end users can be provided with pre-marked sample frequency domain graphs and correlations.

In a particular embodiment, the construction information for an actuator (gear ratios, motor speed, teeth per gear, balls per bearing, etc.) may be downloaded from a memory in an electronics package of the actuator. An on-board CPU can then refer to the stored information and conclude which part of the drive is causing the deviation. A representation of the FT can be displayed directly on an operator's LCD screen, or the data field can be downloaded to a user's data management system for analysis or to a service technician's laptop or PDA for transmission to the home office for detailed analysis.

The programming for collecting data and/or performing frequency analysis may be stored in firmware, software, hardware, or other forms known in the art. For example, frequency analysis programming can be stored in the firmware of a valve actuator.

Additionally, a user can identify peaks in the frequency domain simply by comparing a current analysis with a previous analysis. The previous analysis can then be an analysis carried out in the factory. However, there may be situations where it is desirable or necessary to identify the peaks in the frequency domain independently of prior analysis. For example, at the design stage of a new valve actuator, an engineer may wish to perform frequency analysis on a new prototype to ensure that there are no life-limiting vibrations, resonances, and/or overtones inherent in the prototype's design. Alternatively, frequency analysis can be used as a post-assembly, pre-shipment inspection tool to determine whether some parts of the mechanical drive train were manufactured with a physical defect.

A processor built into the encoder or incorporated into or connected to the valve actuator or other rotating device can perform the FT. A display, printer, or other output device may be included in the valve actuator to display the results in an image or graphical form. Alternatively, the speed data generated by the timing marks 28 may be sent to a remote computer, such as a user's PC, to perform FT based on the speed data and display it in more user-friendly formats, or to transmit the data or FT to technicians on site or may not be.

Providing more examples can result in finer frequency resolution after applying FT to the velocity data. Multiple samples can be provided by increasing the length of time that samples are taken or by increasing the sampling rate. 8th until 15 show graphs generated from data taken at 17 samples per second. 8th shows the frequency analysis resolution of a valve actuator with a total of 128 samples. 9 shows the speed data of 8th before performing an FT on the velocity data. 10 shows the frequency analysis resolution of a valve actuator with a total of 256 samples. 11 shows the speed data of 10 before performing an FT on the velocity data. 12 shows the frequency analysis resolution of a valve actuator with a total of 512 samples. 13 shows the speed data of 12 before performing an FT on the velocity data. 14 shows the frequency analysis resolution of a valve actuator with a total of 1024 samples. As can be seen, the resolution of the frequency analysis improves with an increasing number of samples.

Any type of frequency analysis known in the art can be used with the present invention. In the particular embodiment described, the FT on velocity data was performed using a number of samples equal to ²ⁿ , where n is any integer. Therefore, the total sum of samples is equal to e.g. 128, 256, 512, 1024, 2048, 4096, 8192 etc. Therefore, if 3500 samples were taken, only 2048 of the samples can be used in the FT. In other embodiments, the FT may be applied to samples that are not precisely equal to ²ⁿ . However, leakage becomes a problem in these embodiments. Technologies that deal with leakage are known in the prior art.

Additionally, in a particular embodiment, the FT uses samples taken at steady state. Therefore, the timing wheel 20 is rotated at a relatively constant speed. If the rotary encoder 1 is within an electrically driven valve actuator, the timing wheel 20 will accelerate and decelerate during a period of time. The velocity data generated during acceleration and deceleration can be constrained, averaged, or cut out before performing the FT. Transient frequency analyzes are known in the art and can be used instead of rounding the data.

Rounding of the velocity data may be performed by an algorithm designed to analyze the velocity data prior to the FT process to remove any acceleration or deceleration data. Alternatively, velocity data can be rounded to make the number of samples compatible with the FT 2 ⁿ requirement.

FT, as the term is used here, covers a wide range of algorithms, including the fast Fourier transform. FT, as used here, covers four main families of Fourier transforms: the continuous Fourier transform, Fourier series, discrete time Fourier transform, and discrete Fourier transform. There are also FT algorithms designed to handle approximate and non-uniform data. The discrete Fourier transform is most commonly used for digital signal processing. The term FT, as used herein, includes any algorithm that is compatible with the data produced.

The lead time represents the maximum time during which samples can be taken. For example, with a valve actuator, the time it takes for a valve to move from the open to the closed position, or vice versa, is the maximum amount of time during which velocity data can be collected. A valve can also only be partially moved and therefore only part of the lead time can be available for velocity data recording. An exemplary way to increase the number of velocity data samples generated includes increasing the sampling rate. The sampling rate is controlled by the speed of the timing wheel 20 and the number of timing marks 28. Rotary encoders 1 and 2 are suitable for sampling rates significantly higher than 17 samples per second.

Yet another way to increase the number of data samples generated involves collecting data over multiple lead times. Each new data set can be linked to the existing data collection until the sample number is sufficiently high to allow FT to be performed on it. Once the data set is full, any new data samples can replace the oldest data samples, and therefore obtain the newest data sets for analysis. The velocity or position data can be stored, for example in a data table, for near real-time or next frequency domain analysis.

15 provides a table of possible sampling rates and the resulting total number of samples that can be used for frequency analysis. In 15 The incremental pulse frequency corresponds to the sampling rate in Hz. The speed DS is the drive speed of the drive sleeve (DS) of a valve actuator. However, the speed could be DS with a Rotary components of each rotary device match. The cone set speed multiplier represents the speed increase resulting from connecting the gear of the DS to the input shaft that drives the input gear 10. The input wheel 10 speed multiplier represents the increase in speed due to the gear ratio between the gear 11 of the input wheel 10 and the pinion 25 of the timing wheel 20.

An example of a rotating component of a rotating device is a rotating sleeve of a valve actuator. An input shaft could connect the drive sleeve to the input wheel 10 via a set of cones. Any type of connection known in the art can be used to drive the input wheel 10. As a possible example of data extraction, if the drive sleeve is rotating at 200 RPM, and if the cone set results in an approximately 4.8:1 increase in speed, then the input shaft would be rotating at 960 RPM. Therefore, the input wheel 10 would rotate at 960 rpm. The input wheel 10 drives the timing wheel 20. If a 51/38 degree track amplifier is used, then the timing wheel 20 rotates at approximately 1288 rpm. 1288 rpm divided by 60 corresponds to the revolutions per second of the timing wheel 20. The exemplary timing wheel 20, as in 1 shown has 32 timing marks. However, if only 16 timing marks are used, then the revolutions per second multiplied by the number of timing marks produces a sampling rate (incremental pulse frequency) of 343 samples per second. In the same scenario, if the timing wheel 20 has 32 timing marks, the sampling rate is then approximately 678 samples per second. The Nyquist frequency is half the sampling rate. The sample rate multiplied by the lead time in seconds equals the total number of samples that can be collected during a single full run.

15 shows the interaction of lead time and sampling rate in calculating the accuracy of frequency analysis. An alternative, when only short velocity data runs are available, is to combine the short runs together before performing FT on the data to increase frequency resolution.

15 was generated using a Hanning window to prevent disturbances in the resulting frequency values caused by discontinuities in the velocity signal at the beginning and end of the data set. Other possible windows include rectangular, Blackman, Hamming, Kaiser, exponential and flat top. However, any window known in the art can be used to evaluate the speed data. It is known in the art how to perform frequency analysis without the use of windows. Any way known in the art to perform frequency analysis can be used in the present invention.

Frequency data can be evaluated on a case-by-case basis to determine what indicates the peak locations and height relative to a valve actuator. Alternatively, the frequency analysis can be compared to known frequency analysis signatures to determine the health of a valve actuator or rotary device.

16 until 19 show representative frequency analyzes that can be used for comparisons. 18 and 19 show speed variations that generally vary based on the rotational speed of the valve actuator or other rotating device. The data for the 16 and 17 were generated on an actuator operating at 26 revolutions per minute (rpm) steady state. The data for 18 and 19 were generated on an actuator operating at an 18 rpm steady state. 16 and 19 and 17 and 18 each use the same encoder pinion adapter. 16 has significant peaks at 45.4 Hz and 91.1 Hz. The significant peaks in 19 are much more emphasized and frequent. Many problems within a valve actuator or other rotating device can combine to appear as a single peak in the frequency range. Frequency analysis at different operating speeds can reveal potential problems that are hidden within a single peak at one speed but appear as multiple peaks at different speeds.

The encoder of the present invention has been described as a multi-wheel absolute encoder. The encoder can also be a single-wheel absolute encoder or an incremental encoder. For example, the timing wheel 20 could be integrated into the same wheel as the input wheel 10. The input wheel 10 could then act as an incremental encoder or as a timing wheel. Furthermore, the coding sections of the coding wheels 30 to 110 can be integrated into the input wheel 10, as is known in the art. The input wheel 10 can then operate as a single wheel absolute encoder. The input wheel 10 may be designed to cooperate with the end of an input shaft or alternatively the input wheel 10 may be mounted around an input shaft, i.e. in the longitudinal center of the input shaft. However The input wheel 10 may be attached at any point along the length of an input shaft.

Previously, frequency analysis was discussed relative to velocity data. An additional data embodiment includes torque data. In valve actuators in which torque is measured, the oscillations of the torque can be converted into the frequency range. Where the output torque delivered to a valve stem is monitored, the torque data could also be analyzed in the frequency domain. A processor integrated in or remote from the valve actuator could convert the torque data in the frequency domain in any of the ways discussed above with respect to the velocity data, or by any technology known in the art. The frequencies can then be identified with the powertrain components and the user is provided with an indicator of the health of the valve actuator.

Another data embodiment includes thrust data. As an example, an electric motor of a valve actuator is coupled to the worm of a worm/worm wheel in the drive train. The axial thrust of the worm is monitored to read the torque delivered by the worm wheel. A processor included in the valve actuator or a processor included remotely from the valve actuator may convert the thrust data in the frequency domain identical to any of the types discussed above with respect to the velocity data or by any technology known in the art. The frequencies can then be identified with the powertrain components - either by the user or by a computer program. Therefore, a diagnosis of the valve actuator is provided. In addition, several thrust sensors can be used.

An additional data embodiment includes vibration data. For example, eight accelerometers are arranged at a variety of locations in a valve actuator. All eight accelerometers read the same vibrations in the valve actuator. However, the accelerometer closest to the given source would have the most intense signal. Viewing vibration data from all eight sensors in the frequency domain can enable pinpoint location of vibration sources. The frequencies of the vibrations can then be correlated with the powertrain components. Therefore, a user can be warned of upcoming problems with the valve actuator.

Any number of sensors in any of the embodiments can be used. For example, more than one speed sensor can be used. In addition, several sensors of different types can be used. For example, a valve actuator may include a rotary encoder, such as rotary encoder 1. The valve actuator may also include an axial thrust sensor. Frequency analyzes can be performed on the velocity data generated by the timing wheel 20, or on the thrust data, or both.

The rotating device or valve actuator to be monitored by the present invention may be driven by an electric motor, hydraulic pressure, a machine, a handwheel, or any other type known in the art.

Although the foregoing description includes several features, these are not intended to limit the scope of the present invention, but rather to provide certain exemplary embodiments. Similarly, other embodiments of the invention may be devised which do not depart from the spirit or scope of the present invention. The spirit of the invention is therefore indicated and limited only by the appended claims and their legal equivalents, rather than by the foregoing description. All additions, deletions and variations of the invention as described herein that fall within the meaning and scope of the claims are included in the present invention.

Claims (20)

A valve system comprising: a valve actuator having a plurality of sensors (160, 160') adapted to generate data; a timing mechanism including a timing wheel (20) with a plurality of timing marks (28) arranged in a concentric pattern around the timing wheel (20), the plurality of sensors (160, 160 ') forming a dual set of redundant timing sensors monitoring the plurality of timing marks (28) of the timing wheel (20), wherein the plurality of sensors (160, 160') and the timing mechanism generate data relating to one or more components of the valve actuator, and wherein the dual set of redundant timing sensors includes a first sensor, which is positioned on a first side of the timing wheel (20), and a second sensor which is positioned on a second, opposite side of the timing wheel (20). ned, wherein the first sensor and the second sensor each include an emitter (164) and a detector (162), the detector (162) being positioned adjacent the emitter (164); and a processor (150) in communication with the plurality of sensors (160, 160') and adapted to convert the data in a frequency range. valve system Claim 1 wherein the plurality of sensors (160, 160') further includes one or more of a speed sensor, a position sensor, a torque sensor, a thrust sensor and a vibration sensor, and wherein the data includes at least one of rotational speed data, position data, torque data, thrust data, and Include vibration data. valve system Claim 1 , wherein the plurality of sensors (160, 160') includes at least one speed sensor, and the processor (150) is adapted to receive speed data from the at least one speed sensor and to perform a frequency analysis of the speed data. valve system Claim 3 , in which the at least one speed sensor is included in a rotary position encoder. valve system Claim 4 , in which the rotary position encoder is an incremental encoder. valve system Claim 4 , in which the rotary position encoder is an absolute encoder. valve system Claim 6 , in which the absolute encoder comprises a single encoder plate. valve system Claim 6 , in which the absolute encoder comprises several encoder plates. valve system Claim 8 , in which the plurality of encoder plates each comprise coding sections (44, 48) which are capable of coding a plurality of positions of a rotating device, and in which the absolute encoder has at least one double set of position sensors for each of the at least one coding sections (44, 48). includes, wherein the at least one dual set of position sensors is capable of monitoring each of the at least one coding sections (44, 48). valve system Claim 4 , further comprising a handwheel, which is suitable for operating the valve actuator, and is suitable for operating the rotary position encoder. valve system Claim 4 , in which the rotary position encoder is adapted for actuation by a drive train of the valve actuator. valve system Claim 11 , in which the rotary position encoder is actuated by an input shaft driven by a worm wheel of the drive train. valve system Claim 4 , in which the rotary position encoder is adapted for actuation by an electric motor in the valve actuator. valve system Claim 3 , in which the plurality of sensors (160, 160 ') include at least one torque sensor, wherein the processor (150) is adapted to receive torque data from the at least one torque sensor and to perform a frequency analysis of the torque data. valve system Claim 3 , in which at least one sensor of the plurality of sensors (160, 160 ') is an axial thrust sensor, wherein the processor (150) is adapted to receive axial thrust data from the at least one axial thrust sensor and to carry out the frequency analysis of the axial thrust data. valve system Claim 3 , in which at least one sensor of the plurality of sensors (160, 160 ') is an accelerometer, the processor (150) being adapted to receive acceleration data from the at least one accelerometer and to carry out the frequency analysis of the acceleration data. valve system Claim 4 , in which the rotary position encoder includes the timing mechanism and the plurality of sensors (160, 160 '). valve system Claim 4 , in which the rotary position encoder includes the processor (150). valve system Claim 1 , in which the processor (150) uses a Fourier transform to convert the data into the frequency domain. valve system Claim 1 , further comprising a display adapted to Communication with the processor (150) and for displaying the data.

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