DE20216641U1 - Sensor arrangement for monitoring a plurality of positions of a moving part - Google Patents

Description

PATENT ATTORNEYS "*-

DR. ULRICH OSTERTAG DR. REINHARD OSTERTAG

EIBENWEG 10 D-70597 STUTTGART TEL.+49-71 1-766845 FAX +49-711-7655701

Sensor arrangement for monitoring a plurality of positions of a moving part

Applicant: Klaschka GmbH & Co.
PO Box 1122

75229 Tiefenbronn
Attorney file: 8463.9

TIT.02-049

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Sensor arrangement for monitoring a plurality of positions of a moving part

The invention relates to a sensor arrangement for monitoring a plurality of positions of a moving part according to the preamble of claim 1.

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There are various areas of application of technology in which it must be determined whether a moving part is in one of a number of predetermined positions. Examples include not only moving machine parts but also, in particular, the positions of doors that can be used to open access to a danger zone for repair, maintenance or supply purposes, but which normally make access to the danger zone impossible.

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To detect the moving part in the majority of positions of the moving part, separate sensors were previously used. For each position to be detected, a fixed sensor part and a sensor part that moved along with the moving part were provided.

These sensor arrangements are expensive, especially when the sensor parts have to meet high safety requirements.

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The present invention therefore aims to provide a sensor arrangement according to the preamble of claim 1, which ensures the detection of the presence of a moving part in a plurality of positions with less structural effort.

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This object is achieved according to the invention by a sensor arrangement having the features in claim 1.

In the sensor arrangement according to the invention, only a single fixed sensor part is used, which is designed to receive different identification signals, one of which is generated by one of the plurality of moving sensor parts.

By having only one fixed sensor part, not only is the effort for the other fixed sensor parts saved, but the installation of such a sensor arrangement is also simplified, since only one fixed sensor part needs to be wired. For the same reason, the maintenance and inspection of the sensor arrangement is also simplified.

As a rule, moving sensor parts can be constructed that do not require their own power supply or have only a low power requirement. In this case, no electrical connections to the moving sensor parts need to be made.

This means that the entire sensor arrangement is easy to cabling, monitor and maintain. In practice, the only fixed sensor part can often be installed at a location that is at the end of the movement stroke of the moving part. This means that the fixed sensor part is generally only exposed to a smaller risk of damage. The same applies to the cabling leading to the fixed sensor part.

It should be noted that a signal in the sense of

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present claims and description can be realized both by providing energy in an otherwise energy-free location and by dissipating energy in an otherwise energy-filled area of space. 05

Advantageous developments of the invention are specified in subclaims.

The development of the invention according to claim 2 is particularly suitable for use in harsh environments.

Such a sensor arrangement does not influence the movement of the moving part in any way.

With a sensor arrangement according to claim 3, a very reliable distinction can be made between the different positions of the moving part, since qualitatively different signals are provided in the different positions. For example, for one position of the moving part, a static magnetic field of a certain strength can be used as an identification signal (permanent magnet in combination with a Hall probe), for a second position of the moving part, a light signal can be used (e.g. light barrier operating in transmission or reflection), for a third position of the moving part, an HF signal (principle of an inductive proximity switch), for yet another position of the moving part, a signal that changes in a certain way over time can be used (e.g. an HF signal modulated by a bit pattern).

The development of the invention according to claim 4 allows a very large number of different identification signals to be generated and detected using simple means of digital data technology. The identification signal can be very short in time

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so that a very rapid position detection is obtained.

If optical patterns are used as identification signals for the moving sensor parts, as specified in claim 5, these can be distinguished reliably and without interference, even from a very large distance, if desired. The fixed sensor part therefore does not need to be arranged in the immediate vicinity of the path of the moving sensor parts, which is sometimes of interest in view of the installation effort and in view of the inaccessibility of the fixed sensor part with regard to manipulation.

The development of the invention according to claim 6 also makes it possible to ensure very simple and reliable detection of the position assumed by the moving part. The position is also easily recognizable visually by a human observer.

The variant according to claim 7 is also well suited for harsh operating conditions.

A sensor arrangement according to claim 8 is characterized by a particularly simple structure and a large degree of agreement in the logical subunits, which simplifies the design and manufacture and saves costs.

According to claim 9, a particularly reliable evaluation of the output signal of the receiving head is obtained, since the evaluation with regard to the different positions of the moving part takes place in separate evaluation circuits, so that if a hardware error occurs in one of the evaluation circuits, the other evaluation circuits remain functional. This is advantageous for safety reasons.

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liability.

Sensor arrangements for monitoring a plurality of positions of a moving part that are used in safety-relevant areas or danger areas often have to undergo an approval test. Any intervention in the approved sensor arrangement that could affect the operation of the sensor arrangement would invalidate the type approval of the sensor arrangement. The development of the sensor arrangement according to claim 10 allows additional, non-safety-relevant positions of the moving part to be detected with such a sensor arrangement without any intervention in the approved part of the sensor arrangement that would call the type approval into question. The one-way coupling circuit provided according to claim 10 ensures that no interference signals that could lead to errors can be sent back from the single-channel evaluation circuits to the input of the two-channel evaluation circuits.

The evaluation circuits specified in claim 11 and 12 can be implemented particularly easily using standard circuits available on the market. Amplitude discriminators are available in many different types on the market, and course discriminators, which monitor the temporal course of a signal, in particular a bit pattern modulated signal, are also used in connection with starter locks for motor vehicles, so that the corresponding circuits are also available at low cost.

The invention is explained in more detail below using exemplary embodiments with reference to the drawing. In this drawing:
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8463.9

Figure 1: a schematic view of a roller door, through which access to a danger area is possible, as well as a sensor arrangement that detects various predetermined positions of the roller door, and a block circuit

image of a control system for a roller shutter drive and an emergency shutdown for a manipulation robot working behind the roller shutter;

Figure 2: a block diagram of the sensor arrangement of Figure 1; and

Figures 3 to 6 show modified sensor arrangements for detecting a plurality of positions of a moving part, e.g. a door.

In Figure 1, a roller shutter is designated by 10. It has a curtain 14 composed of individual bars 12, which can be wound onto a drum 16 arranged at the upper end of the curtain.

The lateral boundary surfaces of the armor 14 run in vertical guide rails not shown in detail in Figure 1.

A gear motor 18 is provided for moving the drum 16. This can be supplied with signals via control lines 20, 22 that specify the direction of rotation and the speed of rotation. An electromagnetic brake of the gear motor 18 can be activated via a further control line 24.

The gear motor 18 is controlled by a motor control unit 26.

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The tank 14 carries four transponders 28, 30, 32 and 34 on its side surface located on the left in Figure 1. These are shown schematically as circles in Figure 1 for the sake of better representation. In reality, the transponders 28, 30, 32 and 34 are cylindrical components that are inserted into the side surface of the tank 14 from the left with the cylinder axis running parallel to the rods 12.

The transponders 28, 30, 32, 34 can cooperate, in a manner to be explained in more detail below, with a receiving head 36 which belongs to a fixed sensor part 38 which is arranged at the upper end of the desired stroke of the roller door 10.

The transponders 28, 30, 32, 34 can have an internal structure similar to that known from starter locks for motor vehicles. Such transponders are manufactured by TEMIC Semiconductors, for example. For details of the structure, please refer to the publication U22 70B with printing reference TELEFUNKEN Semiconductors, Rev. A3, 13-Dec-96.

5 The transponders 28, 30, 32 and 34 have, roughly speaking, the following structure: In their front face they have a coil which, together with a capacitor, forms an oscillating circuit. This oscillating circuit is magnetically coupled via the coil field to an LC oscillating circuit which is arranged in the receiving head 36. The oscillating circuit of the receiving head 36 is excited by an operating circuit to oscillate at or near the natural frequency.

5 The transponders and the receiver head have the same

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Frequency running clocks, and the transponder clock circulates a shift register in which a specific bit sequence is stored. In practice, the circulating register can contain 64 bits. The bit sequence is only assigned once by the transponder manufacturer, so that each transponder is individual.

The bit sequence controls a switching transistor, via which a loss resistor can be switched into the transponder's oscillating circuit. If the resistor is switched on, more RF energy is dissipated in the transponder than if this resistor is not switched on. The receiving head 36 registers the increased attenuation caused by this switching on of the loss resistor. The bit sequence contained in the transponder's shift register can thus be recovered from the output signal of the receiving head 36.

The bit sequences detected by the receiving head 36 are sent to an evaluation unit in the sensor part 38, designated overall by 40, which analyzes the incoming bit sequences and determines which of a plurality of reference bit sequences stored there corresponds to the bit sequence just received. From the reference bit sequence that matches the received bit sequence, it can thus be deduced which of the transponders 28, 30, 32, 34 the receiving head 36 is currently facing.

Depending on which of the reference bit sequences the incoming bit sequence matches, the evaluation unit 40 then generates an output signal on one of four output lines 42, 44, 46, 48.

If the bit sequence of the transponder 28 is received, the bit sequence connected to the output lines 42, 44, 46, 48

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The motor control unit 26 ensures that the roller door 10 is in its upper end position. The motor control unit 26 will terminate the signals on the control lines 20, 22 and, by applying a signal to the control line 24, will engage the brake of the gear motor 18.

If, when the roller door 10 is moved upwards, the evaluation unit 40 determines that the incoming bit sequence corresponds to the reference bit sequence for the transponder 3 0, the motor control unit 26 knows that it can now reduce the speed of the gear motor 18 in order to ensure that the roller door 10 moves slowly into the upper end position.

If the evaluation unit 40 determines when the roller door 10 is moved downwards that the received bit sequence corresponds to the reference bit sequence for the transponder 32, the motor control unit 26 knows that the speed of the gear motor 18 can now be reduced in order to slowly move the roller door 10 into the lower position.

If the evaluation unit 40 determines that the received bit sequence corresponds to the reference bit sequence for the transponder 34, the motor control unit 26 knows that the roller door 10 has reached the lower end position. The motor control unit 26 then stops the signaling of the control lines 22 and 24 and ensures that the brake of the gear motor 18 is engaged via the control line 24.

If the roller door 10 has reached the lower end position, as described above, this also means that the space behind the roller door 10 is no longer accessible. From this point onwards,

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At this point in time, work that involves danger to operating personnel can now be carried out again, e.g. a schematically controlled manipulation robot 50 set up in this room can now work again without endangering people. For this purpose, the output signal of the evaluation unit 40, which signals that the lower position of the roller door 10 has been reached (transponder 34 is in front of the receiving head 36), is passed on through the motor control unit 26 to a robot control unit 52, which controls the operation of the manipulation robot 50.

Due to the design of the transponders 28, 30, 32, 34 and the receiving head 36, it is ensured that a signal transmission between these two sensor parts only takes place if the distance between them is in the range of fractions of a cm to a maximum of 1 cm.

0 For some applications, it is necessary that high demands be placed on the safety of determining the closed state (or another end position) of a moving part (here a roller shutter door). For such applications, safety regulations stipulate that position monitoring must be carried out on multiple channels.

For these reasons, such safety-relevant position monitoring is currently carried out with duplicate sensors, i.e., for the lower end position of the roller door 10, for example, two separate mechanical limit switches and associated signal processing channels would have to be provided.

Since sensors operating according to the transponder principle described above are manufactured in very large quantities and, once they have been

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meet the requirements and work very reliably in long-term operation, the safety regulations allow a position measurement based on the transponder principle to be carried out with only one transponder and one receiving head - only the signal processing behind the receiving head has to be duplicated.

Figure 2 shows a sensor arrangement which meets such increased safety criteria for the lower end position of the roller door 10. Parts of the sensor arrangement which were already explained above with reference to Figure 1 are again provided with the same reference numerals and will not be described in detail again. 15

The evaluation unit 40 has a sub-unit 54, which is designed in two-channel technology for high safety requirements in order to detect the lower end position of the roller door, and a sub-unit 56 in single-channel technology located at the bottom in Figure 2, which serves to detect the other positions of the roller door, which are less safety-relevant.

The subunit 54 is connected directly to the receiving head 3 6 , the subunit 56 with the interposition of a one-way coupler 58. The latter only allows signals to pass from the receiving head 3 6 to the subunit 56, but not in the opposite direction. This means that if errors occur in the subunit 0 56, repercussions on the safety-relevant subunit 54 of the evaluation unit 4 0 are excluded. In practice, the one-way coupler 58 can be formed by an opto-coupler.

5 The subunit 54 of the evaluation unit 4 0 comprises two

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Serial comparators 60, 62. Each of these has an input register, which is loaded with the incoming bits, and a reference bit register of the same length, which was filled during production with a reference bit pattern that corresponds to the identification bit pattern of the transponder 34. The two registers are connected to a comparator, which checks the register contents against each other (if necessary with a suitable phase shift) and, if the test result is positive, provides an output signal, which controls a downstream output stage 64 or 66.

The Serial Comparator 62 has a similar logic design, but uses different hardware and software to perform the same test for safety reasons.

As shown by arrowed lines, the serial-0 comparators 60, 62 each check the correct overall function of the signal channel under consideration and the other signal channel.

In the embodiment considered here, the 5 signal outputs of the two output stages 64, 66 are linked via an AND gate 67, so that a signal is only received on the line 42 connected to the output of the subunit 54 if both signal channels of the subunit 54 signal the presence of the transponder 34 at the receiving head 36.

The subunit 56 has serial comparators 68, 70, 72, which are constructed similarly to the serial comparators 60 and 62. However, these comparators now contain reference bit patterns that correspond to the identification bit patterns of the trans-

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ponder 32, 3 0 and 2 8 correspond.

The serial comparators 68, 70, 72 are connected to output stages 74, 76, 78, to which the output lines 44, 46 and 48 are connected.

It can be seen that with the sensor arrangement described above, several positions of the roller door 10 can be monitored by wiring only one sensor part. The transponders 28, 30, 32, 34 attached to the roller door 10 do not require their own power supply.

If one wishes to change one of the positions to be monitored, this can be done very easily by moving the corresponding transponder in the side of the tank 14. Changes to the wiring are not necessary.

If the individual bars of the curtain 0 14 of a roller door 10 are made of metallic material,

the end sections of the rods are made of plastic material or slotted so that the coils of the transponders are sufficiently reached by the reading magnetic field of the receiving head 36.
25

In the embodiment described above, the individual transponders 28, 30, 32, 34 were distinguished by the bit sequences stored in them, with which the magnetic field built up by the receiving head 36 is weakened in a controlled manner.

The transponders that move with the roller shutter 10 or another moving part can also be individualized in other ways.
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In the embodiment shown in Figure 3, the transponders 28, 30, 32, 34 are individualized in that their surface facing the receiving head 36 is red ("R"), green ("G"), blue ("B") and white ("W"). 05

The receiving head 3 6 now has a lens 80 in its front surface facing the path of the transponder, which lens is surrounded by a ring of white light diodes 82.

Behind the lens 80 there is a first semi-transparent mirror 84 which reflects one third of the light and transmits two thirds.

Behind the semi-transparent mirror 84 there is a second semi-transparent mirror 86 which reflects 50% of the light and transmits 50% of the light.

The light reflected by the mirror 84 passes through a red filter 88 to a light detector 90, which can be, for example, a 0 phototransistor.

The light reflected by the mirror 86 passes through a green filter 92 to a light detector 94.

5 The light passing through the mirror 86 passes through a blue filter 96 to a light detector 98.

The output signals of the light detectors 92, 94 and 98 are amplified by amplifiers 100, 102 and 104.

In this embodiment, the output signals of the amplifiers 100, 102 and 104 are applied to the output lines 42, 44 and 46. The output line 48 is connected to the output of an AND gate 106, the inputs of which are connected to the outputs of the amplifiers 100, 102 and

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104 are connected.

In this way, a signal is again received on one of the output lines 42, 44, 46 and 48, depending on which of the differently colored transponders 28, 30, 32 and 34 is opposite the receiving head 36.

In the embodiment according to Figure 4, small circular areas are provided on the transponder, which are arranged along lines perpendicular to the direction of movement of the moving part and thus form an optical pattern. In the selected embodiment, the circular areas are selected so that they correspond to the binary representation of the numbers "1", "2", "3" and "4".

The circular pattern lines are read by three light barriers 110, 112 and 114 operating in reflection, the beam directions of which are actually perpendicular to the plane of the drawing in Figure 4, but which are shown tilted into the plane of Figure 4 for the sake of better illustration.

The outputs of the light barriers 110, 112 and 114 are connected to the inputs of a binary/decimal converter 116. Its outputs corresponding to the numbers "1" to "4" are connected to the output lines 42, 44, 46 and 48.

In this way, it is also possible to determine which of the transponders 28, 30, 32 and 34 is currently in front of the receiving head 3 6.

In a modification of an optically readable number display 5 on the transponders, one can also have a corresponding

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make tactile marking of the transponders. In this case, the light barriers 110, 112 and 114 are replaced by mechanical buttons. The rest of the arrangement is the same as shown in Figure 4.

Figure 5 shows another way of differentiating the transponders by means of information carried by them. According to Figure 5, this information consists of different marks 118, 120, 122 and 124, which are carried by the transponders and differ in their edge contour.

The front surface of the receiving head 3 6 facing the path of the transponders is designed in a similar way to that already described with reference to Figure 3. However, the lens 80 now serves to project the marks carried by the transponders onto an image converter 12 8. This can be a similar image converter to that used in video cameras.

0 The pixels of the image converter 12 8 are fed to one input of an image comparator 13 0 , which is connected with its other input to a reference image memory 132. This contains pixels in four memory fields, as they are obtained on the image converter 12 8 by the marks 118, 120, 122 and 124.

The image comparator 13 0 generates a signal on each of its four outputs whenever the image generated on the image converter 128 corresponds to one of the images stored in the reference image memory 132. The outputs of the image comparator 13 0 are connected to the output lines 42, 44, 4 6 and 4 8 .

In the embodiment according to Figure 6, the transponders 28, 30, 32 and 34 carry permanent magnets 134, 136,

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138, 140, which generate static magnetic fields h of different strengths (IH, 2H, 3H, 4H).

The receiving head 36 now contains a Hall probe 140.

The Hall voltage generated by this is fed to the inputs of four window discriminators 142, 144, 146, 148, whose windows are set so that they cover a narrow range around the Hall voltage obtained when the transponder 28, 30, 32 or 34 is compared with the Hall probe 140. The outputs of the window discriminators 142, 144, 146, 148 are connected to the output lines 42, 44, 46, 48.

The embodiments described above each concerned cases in which the information carried by the transponders 28, 30, 32 and 34 could be read out using the same measuring principle, i.e. was modulated onto the same physical quantity.

0 In a modification of the embodiments described above, the information on the transponders 28, 30, 32 and 34 can also be selected in such a way that different measuring methods are necessary to read this information. In this case, the receiving head 5 3 6 must comprise sensor elements that operate according to different measuring methods.

This means an additional metrological decoupling of the monitoring of the different positions, which can be interesting for safety reasons.

Since there are sensor elements on the market that work according to different measuring methods and require only a small amount of space, these sensor elements can also be accommodated together in a compact receiving head, so that

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In terms of cabling, ease of maintenance and monitoring, such a receiving head can also achieve the same advantages as a receiving head that only operates according to a single measuring principle.

In the embodiments described above, a roller door was considered as the part to be monitored. It goes without saying that the same sensor arrangement can also be used on rigid doors.

In the embodiments described above, a linear movement of the part to be monitored was also assumed. It goes without saying that the sensor arrangements described above can also be used, with appropriate modifications, for rotary movements or other movements that are a superposition of linear movements and rotary movements.

In the embodiments described above, the transponders were attached directly to the part to be monitored. It goes without saying that the sensor arrangement can also be made to work with another moving part that is coupled to a moving part to be monitored in a clear and secure manner.

Claims (12)

1. Sensor arrangement for monitoring a plurality of positions of a moving part ( 14 ) with an arrangement of fixed sensor parts and with an arrangement of sensor parts ( 28 , 30 , 32 , 34 ) which move with the moving part ( 14 ), characterized in that the arrangement of fixed sensor parts has a single fixed sensor part ( 38 ) which comprises a receiving head ( 36 ) which can receive a plurality of different identification signals, and an evaluation unit ( 40 ) which compares the received identification signals with a plurality of different reference signals and provides one of a plurality of different output signals when the received identification signal matches a reference signal, and that the moving sensor parts ( 28 , 30 , 32 , 34 ) each provide an identification signal when they are in a position adjacent to the fixed sensor part ( 36 ). stand. 2. Sensor arrangement according to claim 1, characterized in that the moving sensor parts ( 28 , 30 , 32 , 34 ) cooperate with the fixed sensor part ( 36 ) without contact. 3. Sensor arrangement according to claim 1 or 2, characterized in that the different identification signals differ in their physical carrier, their amplitude, their temporal course or their spatial distribution. 4. Sensor arrangement according to claim 3, characterized in that at least one of the identification signals is formed by a bit pattern. 5. Sensor arrangement according to claim 3 or 4, characterized in that at least one of the identification signals is formed by an optical pattern ( 108 ; 118 ). 6. Sensor arrangement according to one of claims 3 to 5, characterized in that at least one of the identification signals is formed by a color. 7. Sensor arrangement according to one of claims 3 to 6, characterized in that at least one of the identification signals is formed by a magnetic field. 8. Sensor arrangement according to one of claims 1 to 7, characterized in that the fixed sensor part ( 38 ) has a single receiving head ( 36 ) and a plurality of evaluation circuits ( 60 , 68 , 70 , 72 ) connected to it, each of which provides one of the output signals when the received identification signal corresponds to a reference signal. 9. Sensor arrangement according to claim 8, characterized in that for at least one of the evaluation circuits ( 60 ) a parallel-connected second evaluation circuit ( 62 ) is provided, which has the same reference signal. 10. Sensor arrangement according to claim 9, characterized in that the evaluation circuits ( 68 , 70 , 72 ) having only one channel are supplied with the output signal of the receiving head ( 36 ) via a one-way coupler ( 58 ). 11. Sensor arrangement according to one of claims 1 to 10, characterized in that the evaluation unit ( 40 ) has at least one evaluation circuit ( 142 , 144 , 146 , 148 ) which comprises an amplitude discriminator. 12. Sensor arrangement according to one of claims 1 to 11, characterized in that the evaluation unit ( 40 ) has at least one course detector ( 60 , 62 , 68 , 70 , 72 ) which determines the temporal course of the output signal of the receiving head ( 36 ).