JPH0347684B2 - - Google Patents

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to an abnormality detection method and circuit for a displacement detection device, and is particularly suitable for use in a linear displacement measuring device, in which signal generation sources are equidistantly spaced. A main scale formed on the main scale and an index scale having a plurality of signal modulation means arranged in parallel at predetermined intervals in the scanning direction for scanning the main scale are moved relative to each other at the same period. By generating a plurality of analog detection signals having substantially the same waveform and amplitude and whose phases are shifted by a predetermined amount, converting the analog detection signals into pulses, and counting the number of pulses,
The present invention relates to an abnormality detection method and circuit improvement for a displacement detection device that determines the amount of relative displacement between both scales.

[Conventional technology]

In general, in a length measuring device that measures the length of an object, such as a caliper or a micrometer, it measures the amount of movement of something that moves relative to it, such as the amount of movement of a measuring point with respect to its main body, the amount of movement of a slider with respect to a column, etc. In this case, for example, an encoder consisting of a light source, a main scale having an optical grating, an index scale having a plurality of optical gratings with a predetermined pitch shift, and a light receiving element is built into the main body of the length measuring instrument, and the main scale and the index scale are connected to each other. and according to the change in light intensity,
The relative displacement between the main scale and the index scale is determined by generating two analog detection signals that are out of phase with each other, converting the analog detection signals into pulses, and counting the number of pulses. A so-called optical displacement detection device is known. This optical displacement detection device is widely used because it can perform highly accurate detection and is easy to read due to its digital display.

Abnormality detection in such displacement detection devices is important, especially as devices become more precise, such as in the feedback systems of machine tools.
When used online, the propriety of detection must be strictly controlled based on product warranties, etc.

In general, malfunctions of the above-mentioned displacement detection device, for example, an optical displacement detection device, include failure of the light source,
Disconnections, dirt on the lens or optical grid, misalignment, power supply voltage fluctuations, etc. caused by the detector itself, disconnections,
Possible causes include division errors, noise intrusion, damage to electronic components, etc. caused by the encoder, and other factors caused by the counter, display, etc.

Among these methods, conventional methods for monitoring electrical signals after the encoder include a method of converting an analog detection signal into a pulse signal for counting and then comparing it with a reference clock pulse to discover abnormal pulses, and a method of detecting abnormal pulses by converting the analog detection signal into a pulse signal for counting A method has been proposed to monitor the decrease in the level of

[Problem that the invention seeks to solve]

However, the former method lacks reliability because the operating conditions of the detection device vary, and the latter method is also insufficient.

In addition, all conventional methods monitor electrical signals after the encoder, and they require work such as reinstallation and disassembly and assembly on the user's side. However, there was a problem in that it was not possible to detect abnormalities that occurred.

In order to solve this problem, each phase analog signal is processed separately from the counting pulse signal.
It is possible to detect abnormalities in the phase or amplitude of the analog detection signal, but in this case, the analog detection signal is modified, which not only complicates the configuration, but also requires modification of the analog detection signal. There was a risk that an abnormality would occur.

[Purpose of the invention]

The present invention was made in order to solve the above-mentioned conventional problems, and it is possible to simultaneously detect abnormalities caused by many causes of failure without modifying the analog detection signal or modifying the pulse signal after it has been converted into pulses for counting. A first object of the present invention is to provide a method for detecting an abnormality in a displacement detecting device that can be monitored.

A second object of the present invention is to provide an abnormality detection circuit for a displacement detection device in which the abnormality detection method according to the present invention is adopted.

[Means for solving problems]

The present invention includes a main scale in which signal generation sources are formed at equal intervals, and an index scale having a plurality of signal modulation means arranged in parallel at predetermined intervals in the scanning direction for scanning the main scale. By causing relative movement, generating multiple analog detection signals having substantially the same waveform and amplitude, which are phase-shifted by a predetermined amount in the same period, converting the analog detection signals into pulses, and counting the number of pulses. , an abnormality detection method for a displacement detection device that calculates the amount of relative displacement between both scales, as shown in Figure 1, a common reference level of all analog detection signals is interposed, and An abnormality detection area is set between a high level and a low level that are set so as not to include all levels that the analog detection signal crosses during normal times, and the actual level of the analog detection signal of each phase is within the abnormality detection area. It is determined that there is an abnormality when the actual levels of all analog detection signals are within the abnormality detection area, and the first
This goal has been achieved.

Further, in an embodiment of the present invention, the difference between the high level and the low level, that is, the abnormality detection area, is set to be smaller as the number of phases of the analog detection signal increases,
This allows abnormalities to be detected with high sensitivity even when the number of phases of the analog detection signal is large.

The present invention also provides an index scale having a main scale in which signal generation sources are formed at equal intervals, and a plurality of signal modulation means arranged in parallel at predetermined intervals in the scanning direction for scanning the main scale. The encoder generates a plurality of analog detection signals having substantially the same waveform and amplitude, which are mutually shifted in phase by a predetermined amount in the same cycle, by moving the signals relatively to each other, and converting the analog detection signals into pulses by a waveform shaping circuit, In the abnormality detection circuit of the displacement detection device, which calculates the amount of relative displacement between both scales by counting the number of pulses with a reversible counter, the common reference level of all analog detection signals is determined.
and a voltage setter that outputs a high level voltage and a low level voltage that are set so as not to include all levels that the plurality of analog detection signals intersect during normal operation; In comparison, a plurality of voltage comparators provided for each analog detection signal of each phase generate an output when the level of the analog detection signal is within the abnormality detection region between the high level voltage and the low level voltage. ,
The second object is achieved by including an abnormality determination circuit that determines that an abnormality exists when all the voltage comparators generate outputs.

Further, in an embodiment of the present invention, the high level voltage and the low level voltage of the output of the voltage setting device are variable,
This allows for easy adaptation to changes in model types, usage patterns, etc.

In another embodiment of the present invention, the voltage comparator is constructed of a comparator having a switching function, so that the processing according to the present invention can be performed accurately with a simple configuration.

[Effect]

The present invention includes a main scale in which signal generation sources are formed at equal intervals, and an index scale having a plurality of signal modulation means arranged in parallel at predetermined intervals in the scanning direction for scanning the main scale. to generate a plurality of analog detection signals having substantially the same waveform and amplitude with the same cycle and a predetermined phase shift, converting the analog detection signals into pulses, and counting the number of pulses. Therefore, when calculating the amount of relative displacement between both scales, the actual level of the analog detection signal of each phase should be between the common reference level of all analog detection signals, and the multiple analog detection signals should intersect under normal conditions. Since it is determined that there is an abnormality when it is within the abnormality detection area between the high level and the low level, which is set so as not to include all levels,
Abnormalities caused by many causes of failure can be monitored all at once without modifying the analog detection signal or modifying the pulse signal after it has been converted into pulses for counting.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a linear displacement measuring machine equipped with an optical displacement detection device employing the present invention will be described in detail with reference to the drawings.

As shown in FIG. 2, this embodiment includes an encoder 12 which is connected to a measuring element such as a spindle (not shown) and is composed of a light source, a main scale, an index scale, and a light receiving element for detecting the displacement of the measuring element (not shown). , a waveform shaping circuit 14 including a direction discrimination circuit and a dividing circuit as necessary, and a counter 1 for reversibly counting counting pulse signals output from the waveform shaping circuit 14.
6, a display driving device 18 that converts the counted value of the counter 16 into a signal suitable for digital display, and a display driving device 18 that is driven by the display driving device 18 and displays the counted value of the counter 16 as a measured value. A digital display device comprising a digital display device 20 and a control section 22 for holding and clearing the count value of the counter 16 and the display value of the digital display device 20, and switching between inch and millimeter units. In the display type linear displacement measuring device 10, a circuit for generating counting pulses (waveform shaping circuit 14, etc.)
Separately, two analog detection signals Sa, which are output from the encoder 12 and whose phases are shifted by 90 degrees, are output from the encoder 12.
A high level voltage that is set to sandwich the common reference level of Sb and not include all levels that the two analog detection signals Sa and Sb intersect during normal operation.
Voltage setting device 3 that outputs La and low level voltage Lb
0, the output of the voltage setter 30 and the levels of the analog detection signals Sa and Sb are compared, and the level of the analog detection signal is within the abnormality detection region S between the high level voltage La and the low level voltage Lb. When the two voltage comparators 32 and 33 provided for each analog detection signal of each phase generate an output, and when all the voltage comparators 32 and 33 generate an output, it is determined that there is an abnormality and an alarm is issued. Abnormality judgment circuit 34 to output
.

The encoder 12 is configured to move together with the probe, as shown in detail in FIG. 3, for example.
Light and dark scale stripes (signal generation source) 12 in the longitudinal direction
Main scale 12A with B formed at equal intervals
and fixed to the main body of the linear displacement measuring device 10,
The main scale 12A is scanned to generate two analog detection signals having substantially the same waveform and amplitude, which are synchronized with each other and whose phases are shifted by 90 degrees at a predetermined interval in the scanning direction. Two bright and dark scale stripes (signal modulation means) arranged in parallel 12
Index scale 12C with D, 12E
, light sources 12F and 12G for irradiating light to the graduation stripes of the main scale 12A and the index scale 12C, and the main scale 12A.
and light receiving elements 12H and 12J for detecting the light transmitted through the index scale 12C and generating two analog detection signals Sa and Sb.

Therefore, the light receiving elements 12H and 12J are connected to the main scale 12A and the index scale 12C.
As shown in FIG. 4, as shown in FIG. 4, two analog detection signals Sa and Sb having substantially the same waveform and amplitude are generated with the same period and a phase shift of 90 degrees.

As shown in detail in FIG. 5, the voltage setting device 30 includes variable resistors 30A, 30B, and 30C for dividing the power supply voltage Vb into a high level voltage La and a low level voltage Lb, respectively.

As shown in detail in FIG. 5, the voltage comparators 32 and 33 respectively detect the first analog detection signal Sa input from the first light receiving element 12H and the high level voltage La or low level voltage Lb. Comparing, the analog detection signal Sa is a high level voltage.
Two comparators 32A and 32B that have a switching function and output a high level signal when the voltage is below La and above the low level voltage Lb.
, the second analog detection signal Sb input from the second light receiving element 12J, and the high level voltage La.
or by comparing the low level voltages Lb, and determining that the analog detection signal Sb is equal to or lower than the high level voltage La;
It also includes two comparators 33A and 33B which also have a switching function and output a high level signal when the voltage is higher than the low level voltage Lb.

The abnormality determination circuit 34 includes the four comparators 32A, 3, as shown in detail in FIG.
The outputs of 2B, 33A, and 33B are connected to each other and then connected to the power supply voltage Vb via a resistor 34A. Therefore, the output of this abnormality determination circuit 34 is transmitted to the four comparators 32.
When the outputs of A, 32B, 33A, and 33B all become high level, that is, the analog detection signals Sa and Sb
When both exist within the abnormality detection region S between the high level voltage La and the low level voltage Lb, the level becomes high and an alarm is output.

The effects of the embodiment will be explained below.

First, under normal conditions, appropriate high level voltage
If La and the low level voltage Lb are set, the output a of the comparators 32A and 32B and the output b of the comparators 33A and 33B will not become high level at the same time. Therefore, no alarm is output.

On the other hand, if a phase shift occurs between the two phases due to an abnormality in the scale graduation or a mechanical malfunction, the timing within the abnormality detection area S will be delayed or advanced, so that both signals Sa and Sb will become synchronous, and the output a, b becomes high at the same time, and an alarm is output. or,
If the amplitude of the analog detection signal becomes small due to dirt on the scale, abnormality in the optical system, electrical system, etc.
Since the stay period in the abnormality detection area S becomes longer, the outputs a and b become high level at the same time,
An alarm is output.

FIG. 6 shows an example of signal waveforms of various parts when an abnormality occurs in this embodiment. As is clear from the figure, when an abnormality occurs in the analog detection signal Sb for some reason, the output a×b of the abnormality determination circuit 34 becomes a high level, so that the phase angle and amplitude of the analog detection signals Sa and Sb change. In addition to abnormalities, all kinds of failures can be discovered, such as disconnection of the light sources 12F and 12G, dirt on the main scale 12A and index scale 12C, and disappearance of analog detection signals due to damage to the light receiving elements 12H and 12J.

The sensitivity of failure detection is determined by applying the difference b between the high level voltage La and the low level voltage Lb to the variable resistors 30A, 30B,
It can be arbitrarily selected by appropriately setting 30C.

In this embodiment, since the high level voltage La and low level voltage Lb in the voltage setting device 30 can be changed, it is possible to easily respond to changes in the model, usage mode, etc.

Note that if the reference voltage common to each phase and the peak value of each phase can also be monitored, it becomes possible to simultaneously monitor a drop in the main power source, etc.

In the embodiment described above, an alarm is generated based on the output of the abnormality determination circuit 34, but the method of using the output of the abnormality determination circuit 34 is not limited to this. It is also possible to give a stop command to a machine tool that is under feedback control.

Note that in the above embodiment, the present invention uses two analog detection signals Sa, Sa and Sa having a phase difference of 90°.
Although the present invention has been applied to a linear displacement measuring device 10 equipped with an optical displacement detection device that generates Sb, the scope of application of the present invention is not limited thereto. For example, in the case of three or more phases, if the abnormality detection area S is narrowed in proportion to the number of phases, more sensitive monitoring can be performed, and even if there are multiple phases, the sensitivity will not decrease. do not have. In addition, it can be applied not only to linear displacement measuring machines equipped with optical displacement detection devices, but also to linear displacement measuring machines and rotary displacement measuring machines equipped with other types of displacement detection devices. can.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to simultaneously monitor abnormalities due to many causes of failure without modifying the analog detection signal or modifying the pulse signal after it has been converted into pulses for counting. This has an excellent effect.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing the outline of an abnormality detection method for a displacement detection device according to the present invention, and FIG. 2 is a flowchart showing an example of a linear displacement measuring machine equipped with an optical displacement detection device to which the present invention is adopted. FIG. 3 is an exploded perspective view showing the configuration of the encoder used in the embodiment, and FIG. 4 shows the relationship between the light receiving element output, that is, the analog detection signal, in the embodiment. A diagram showing an example, FIG. 5 shows a voltage setting device according to the present invention used in the above embodiment,
FIG. 6 is a circuit diagram showing the configuration of the voltage comparator and the abnormality determination circuit, and is a diagram showing examples of signal waveforms of each part in the embodiment. 10...Linear displacement measuring machine, 12...Encoder,
12A...Main scale, 12C...Index scale, 14...Waveform shaping circuit, 16...Counter, 30...Voltage setting device, 30A, 30B, 30C
... Variable resistor, La... High level voltage, Lb... Low level voltage, S... Abnormality detection area, 32, 33... Voltage comparator, 32A, 32B, 33A, 33B... Comparator, 34... Abnormality determination circuit.

Claims (1)

[Scope of Claims] 1. An index having a main scale in which signal generation sources are formed at equal intervals, and a plurality of signal modulation means arranged in parallel at predetermined intervals in the scanning direction for scanning the main scale. The scale is moved relative to the scale to generate multiple analog detection signals with substantially the same waveform and amplitude, which are phase-shifted by a predetermined amount in the same period, convert the analog detection signals into pulses, and count the number of pulses. By doing this, in the abnormality detection method of a displacement detection device that calculates the amount of relative displacement between both scales, a common reference level of all analog detection signals is sandwiched, and multiple analog detection signals intersect in normal conditions. The area between the high level and the low level that is set so as not to include all levels is defined as the abnormality detection area, and whether or not the actual level of the analog detection signal of each phase is within the abnormality detection area is determined for each phase. 1. A method for detecting an abnormality in a displacement detecting device, characterized in that when the actual levels of all analog detection signals are within the abnormality detection area, it is determined that there is an abnormality. 2. An abnormality detection method for a displacement detection device according to claim 1, wherein the difference between the high level and the low level, that is, the abnormality detection area, is set to be smaller as the number of phases of the analog detection signal increases. 3. A main scale in which signal generation sources are formed at equal intervals, and an index scale having a plurality of signal modulation means arranged in parallel at predetermined intervals in the scanning direction for scanning the main scale are relatively moved. Then, the encoder generates multiple analog detection signals with substantially the same waveform and amplitude, which have the same period and are out of phase with each other by a predetermined amount.The waveform shaping circuit converts the analog detection signals into pulses, and the number of pulses is reversibly changed. In the abnormality detection circuit of the displacement detection device, which calculates the amount of relative displacement between both scales by counting with a counter, a common reference level of all analog detection signals is interposed, and multiple analog detection signals are A voltage setting device outputs a high level voltage and a low level voltage that are set so as not to include all levels that intersect during normal operation, and the output of the voltage setting device is compared with the level of the analog detection signal to determine the level of the analog detection signal. A plurality of voltage comparators provided for each analog detection signal of each phase generate an output when the level is within the abnormality detection area between the high level voltage and the low level voltage, and all voltage comparators output. An abnormality detection circuit for a displacement detection device, comprising: an abnormality determination circuit that determines that an abnormality exists when . 4. Claim 3, wherein the high level voltage and low level voltage of the voltage setting device output are variable.
Abnormality detection circuit of the displacement detection device described in . 5. An abnormality detection circuit for a displacement detection device according to claim 3, wherein the voltage comparator is constituted by a comparator having a switching action.