JPH10247109A - Method and device for detecting abnormality of encoder and controller for actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the abnormality detection device of an encoder, which does not need to execute analog adjustment and which is not affected by external noise. SOLUTION: The abnormality detection device of the encoder is provided with a differential circuit 3 detecting the rise/fall voltage changes of an A phase or a B phase and generates pulse output in synchronizing with the rise/fall of the A phase and the B phase, a travel direction discrimination circuit 4 generating pulse output showing the travel direction in a positive direction or an opposite direction based on the phase difference of the A phase and the B phase only when the A phase and the B phase change and a pulse counter 5 setting the pulse output of the differential circuit 3 to be counting input and setting the pulse output of the travel direction discrimination circuit to be a clear signal. When the counting value of the pulse counter 5 becomes not less than a prescribed value, the encoder is judged to be abnormal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to encoder abnormality,
In particular, the present invention relates to a method and a device for detecting a disconnection of an output wire of an encoder, and further relates to a control device for an actuator using the device. .

[0002]

2. Description of the Related Art Generally, an actuator (for example, a motor) used for an industrial robot is provided with an encoder (for example, a rotary encoder) for detecting an operation state of the actuator, and an encoder (for example, a rotary encoder) is provided based on a signal transmitted from the encoder. Thus, the position or speed of the actuator is controlled.

The encoder outputs A-phase and B-phase pulse signals having a phase difference from each other according to the traveling direction of the actuator (rotating direction in the case of a motor). Then, the controller of the robot determines the traveling direction of the actuator based on the received phase difference between the A phase and the B phase, that is, which of the A phase and the B phase is relatively advanced. When the B-phase is continuously received, it is determined that the actuator has advanced a predetermined distance (a predetermined angle in the case of a motor), and the actuator is controlled based on such information.

Here, if one of the encoder wires, for example, the wire related to the A-phase is broken, the control device determines that the actuator is not operating at all, and there is a possibility that the robot may run away. is there. For this reason,
2. Description of the Related Art A robot has a built-in encoder abnormality detection device for preventing runaway.

FIG. 7 shows an example of a circuit configuration of a conventional abnormality detection device. In FIG. 7, 31 is a pull-up power supply having a potential of 5.0 V, 32 is a pull-up resistor, and 33 is T
4.8 V which is a value slightly higher than the high level of the TL level
A reference power supply having a potential of (Vth), 34 is a comparator, and 35 is an AND circuit that outputs a logical sum of outputs of the two comparators 34.

The comparator 34 compares the pulse output of each of the A-phase and the B-phase output from the encoder 2 with a reference voltage (Vth). It is designed to output a signal.

That is, if the encoder is normal, A
The phase and B-phase pulse output voltages are input as rectangular waves of 4.8 V or less even at the high level, so that the comparison results of the comparator 34 are both normal.

On the other hand, when the signal line from the encoder is disconnected, the input voltage to the comparator 34 by the pull-up resistor 32 is the voltage of the pull-up power supply 31 of 5.0.
Since the voltage increases to V, that is, the voltage becomes higher than the reference voltage (Vth), it is determined that there is an abnormality.

[0009]

However, since the above-described method is performed by comparing analog values, fine adjustment is required for setting the reference voltage, and malfunction occurs due to noise superimposed on the signal line. It may be possible. In order to prevent such a malfunction, it is necessary to remove high-frequency components using a low-pass filter.

The present invention has been made in view of the above circumstances, and eliminates the need for fine analog adjustments and minimizes the effects of disturbance noise, thereby enabling highly accurate determination of an encoder. It is an object of the present invention to provide an abnormality detection method and device, and a control device for an actuator including the device.

[0011]

In order to achieve the above object, a first means is an abnormality detection apparatus for an encoder which outputs an A phase and a B phase having a phase difference from each other.
When the phase and the B phase are input and at least one of the outputs of the A phase and the B phase is changed, the A phase and the B phase are changed.
A first circuit that generates a pulse output in synchronization with the rising or falling of a phase, and the A-phase and the B-phase are input, and only when the outputs of the A-phase and the B-phase are both changed, A second circuit that generates a pulse output in synchronization with the rise or fall of the A phase or the B phase;
A pulse counter having a pulse output from the first circuit as a count input and a pulse output from the second circuit as a clear input, wherein when the count value of the pulse counter becomes a certain value or more, The encoder is determined to be abnormal.

Further, the second means is an encoder abnormality detecting device for outputting an A-phase and a B-phase having a phase difference with each other, and detects a rising or falling voltage change of the A-phase and the B-phase. A differentiating circuit for generating a pulse output in synchronization with the rise or fall of the A and B phases, and based on the phase difference between the A and B phases only when both the A and B phases are changing A traveling direction discriminating circuit for generating a pulse output representing a forward direction or a backward traveling direction, a pulse counter having a pulse output of the differentiating circuit as a count input, and a pulse output of the traveling direction discriminating circuit as a clear signal; And when the count value of the pulse counter becomes equal to or more than a certain value, it is determined that the encoder is abnormal.

According to the first and second means, it is not necessary to make fine analog adjustments, and the influence of disturbance noise is minimized. An apparatus can be provided.

The third means is a control device for an actuator for driving a robot or the like, wherein the encoder detects a traveling direction of the actuator and outputs an A phase and a B phase having a phase difference with each other; A differentiating circuit that detects a voltage change at the rising or falling of the phase and the B phase and generates a pulse output in synchronization with the rising or falling of the A and the B phase; Only when the phase difference between the A phase and the B phase, a traveling direction discriminating circuit that generates a pulse output indicating a forward traveling direction or a backward traveling direction based on the phase difference, and the pulse output of the differentiating circuit as a count input. A pulse counter that uses the pulse output of the traveling direction discriminating circuit as a clear signal, an A-phase output and a B-phase output of the encoder, and a pulse counter of the traveling direction discriminating circuit. A feedback control system that controls the actuator based on the pulse output, and an interlock device that stops the actuator when the count value of the pulse counter becomes equal to or greater than a certain value. It is.

According to the third means, the output of the traveling direction discriminating circuit can be shared by the actuator control system and the encoder abnormality detecting device. For this reason, the runaway prevention function of the actuator can be realized with a simple circuit configuration.

The fourth means is a method for detecting an abnormality of an encoder which outputs an A phase and a B phase having a phase difference with each other, wherein at least one of the outputs of the A phase and the B phase is changed. Generating a first pulse output synchronized with the rise or fall of the A phase or the B phase; and rising the A phase or the B phase only when both the outputs of the A phase and the B phase are changing. Or a step of generating a second pulse output synchronized with the falling, and detecting the first and second pulse outputs, and detecting the first and second pulse outputs while detecting the first pulse output a predetermined number of times. And a step of determining that the encoder is abnormal when the second pulse output is not detected.

According to the fourth means, it is not necessary to make fine analog adjustments, and it is possible to detect the disconnection of the encoder with high accuracy while minimizing the influence of disturbance noise.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. First Embodiment First, a first embodiment will be described. 1 to 4 show the first embodiment of the present invention.

First, the configuration of a robot provided with the abnormality detection device 1 according to the present invention will be described. As shown in FIG. 1, the robot has a servomotor 11 as an example of an actuator that drives an arm unit (neither is shown) to which a hand effector is attached, for example.

The servo motor 11 is provided with a rotary encoder 2 (hereinafter simply referred to as an encoder 2) as an example of an encoder. The encoder 2 outputs an A-phase and a B-phase having a phase difference with each other in accordance with the rotation state of the servomotor 11. The output of the encoder 2 is connected to a rotation direction determination circuit 4 which is an example of a traveling direction determination circuit. The rotation direction determination circuit 4
As will be described in detail later, the IC is an IC that transmits rotation information (information of a rotation direction and a rotation amount) of the servomotor 11 as a pulse signal.

The pulse signal is input as feedback data to a position / speed control unit 13 which is a part of a position / speed control system 10, which is an example of a robot control system, and thereby the operation of the servomotor 11 is controlled. It is controlled. That is, the servo motor 11, the position / speed control unit 13, the encoder 2, and the rotation direction determination circuit 4 constitute a position / speed control system 10 of the robot.

The robot has a position / speed controller 13.
And a power supply device 12 for supplying a current to a servo driver 14 provided in the power supply device.

As shown in FIGS. 2 and 3, the output of the encoder 2 is also connected to a differentiating circuit 3. The differentiating circuit 3 and the rotation direction discriminating circuit 4 are connected to the OR circuit 6 and the OR circuit 7, respectively.
7 are connected to the counter 5 respectively. Counter 5
Are connected to an interlock device 15 built in the power supply device 12. The above-described rotation direction discriminating circuit 4, OR circuits 6, 7 and counter 5 constitute the encoder abnormality detecting device 1. In FIG. 2, reference numerals 8a and 8b denote receivers, and reference numerals 9a and 9b denote buffers, both of which fulfill a buffer function such as adjusting received digital waveforms.

Further, T is upstream of the receivers 8a and 8b.
A pull-up power supply 33 having a potential slightly higher than the high level of the TL level and a pull-up resistor 34 are connected.

Next, the operation of this embodiment having the above configuration will be described with reference to FIGS. Note that FIG.
The waveforms shown in (a) to (h) and FIGS. 4 (a) to (i) indicate the waveforms obtained at the positions denoted by reference numerals (a) to (i) in FIG. 2, respectively.

First, the operation of the encoder abnormality detecting device 1 when the encoder 2 is normal will be described with reference to FIGS. FIG. 3 shows waveforms obtained at the respective portions (a) to (i) when the servo motor 11 rotates forward until time t1 and reversely rotates after time t2.

As shown in FIGS. 3A and 3B, when the servo motor 11 is rotating forward, the A phase is 9
When a set of pulse outputs advanced by 0 degrees is output from the encoder 2 and the servo motor 11 is rotating in the reverse direction, the A phase becomes B
A pulse delayed by 90 degrees with respect to the phase is output from the encoder 2.

The A phase and the B phase output from the encoder 2 are input to the differentiating circuit 3 respectively. Differentiating circuit 3 is A
Pulses as shown in FIGS. 3C and 3D are output by capturing the rising edges of the phase and the B phase. Note that the differentiation circuit 3
May capture the fall of the A phase and the B phase.

The pulses corresponding to the A-phase and the B-phase output from the differentiating circuit 3 are input to both terminals of the OR circuit 6, and the OR circuit 6 outputs the logical sum as shown in FIG. I do. This logical sum is input to the counter 5 as a count pulse.

The A-phase and B-phase output from the encoder 2 are also input to the rotation direction determination circuit 4. The rotation direction discriminating circuit 4 discriminates the rotation direction of the servo motor 11 based on the leading and lag relationship between the A phase and the B phase only when both the A phase and the B phase are changing, and counts. An up pulse (hereinafter referred to as a C / U pulse) and a countdown pulse (hereinafter referred to as a C / D pulse) are output.

That is, when the A-phase is advanced, the rotation direction discriminating circuit 4 outputs a C / U pulse in synchronization with the fall of the A-phase, as shown in FIG. Is delayed, a C / D pulse is output in synchronization with the rise of the A-phase as shown in FIG.

The C / U pulse or the C / D pulse is input to both terminals of the OR circuit 7, and the OR circuit 7 outputs a logical sum thereof as shown in FIG. This logical sum is input to the counter 5 as a clear pulse.

As is clear from the relationship between FIG. 3E and FIG. 3H, when the encoder 2 is normal, the counter 5
Is always 2, a clear pulse is inputted to the counter 5. Therefore, the count value of the counter does not exceed 2.

Next, with reference to FIG. 4, description will be given of a case where the wiring related to the A-phase is broken at the time t2 in the encoder 2 which is operating normally.

As shown on the left side of FIG. 4, when the phase A is advanced by 90 degrees with respect to the phase B, and there is no disconnection in any of the wirings related to the phase A and the phase B, in each of the portions a to h The measured waveforms are shown in FIG.
It is exactly the same as the waveform measured in (h).

When a disconnection occurs in the wiring related to the A phase,
Since the output of the phase A detected at the portion (a) is constant at the high level (H) due to the influence of the pull-up resistor 34,
The pulse output from the differentiating circuit 3 is only that shown in FIG. 4D, and the counting pulse input to the counter 5 per unit rotation amount of the servo motor 11 is
Is の of the normal case.

On the other hand, when one of the wirings related to the A-phase or the B-phase is broken, the rotation
Since neither the U pulse nor the C / D pulse is output, the OR circuit 7 does not generate any clear pulse. For this reason, the count value of the counter 5 is
It increases with an increase in the amount of rotation.

The counter 4 generates a carry output when the count value exceeds a predetermined count. That is, for example, when the counter 5 is a 4-bit counter, a carry output is generated when the count value reaches 16 counts.

The carry output is output as an abnormality detection signal, and is input to an interlock device 15 provided in the power supply device 12, and the interlock device 15 stops supplying current to the servo driver 14.

If it is desired to generate an abnormality detection signal when the count value of the counter 4 reaches 4 before the count value of the counter 4 reaches 16, for example, the Qc output of the counter 4 may be used as the abnormality detection signal. . The Qc output is an output that becomes high level (H) when the count value becomes 4, as shown in FIG. 3 (see FIG. 4 (i)). The Qd of the counter 4 which becomes high level (H) when the count value becomes 8
The output may be used as an abnormality detection signal.

As described above, according to the present embodiment, since the output of the encoder is processed as a digital signal, it is not necessary to make an analog adjustment of the disconnection detecting device, and it is hardly affected by disturbance noise. There is no. Therefore, it is possible to accurately and easily detect an abnormality of the encoder, for example, a disconnection of the signal line.

Further, since the rotation direction discriminating circuit can be shared by the control system of the servomotor and the abnormality detecting device of the encoder, the configuration of the control device of the robot can be simplified.

In the description of the embodiments of the present specification, an actuator that performs rotational driving is exemplified as an actuator, and a rotary encoder is exemplified as an encoder corresponding to the driving method of the actuator. However, the present invention is not limited to this. Not something. That is, a linear actuator may be used as the actuator, and in that case, a linear encoder is used as the encoder. Further, in this specification, the term “progression direction determination circuit” includes both a type that determines a direction of a rotary operation and a type that determines a direction other than a rotation operation, for example, a direction of a linear operation. Used in

Second Embodiment Next, a second embodiment will be described. The second embodiment constitutes an encoder abnormality detection device without using the rotation direction discriminating circuit used in the first embodiment. In the second embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description is omitted.

As shown in FIG. 5, the encoder abnormality detecting device has a NAND circuit 21 and a NOR 22 circuit to which the outputs of the A and B phases of the encoder 2 are input. These NAND circuit 21 and NOR circuit 22 include:
Differentiating circuits 3A and 3B are connected respectively. In addition,
The functions of the differentiating circuits 3A and 3B are the same as those of the differentiating circuit 3 of the first embodiment.

The output of the differentiating circuit 3A is used as a count input of the counter 5, and the output of the differentiating circuit 3B is used as a clear pulse of the counter 5.

Next, the operation of the present embodiment having the above configuration will be described with reference to FIGS. FIG.
In (f), a pulse in which the A-phase leads the B-phase by 90 degrees with the encoder 2 in a normal state until the time t2 is output. At the time t2, a disconnection occurs in the A-phase wiring of the encoder. FIG. 6 shows waveforms measured at the respective portions (a) to (f) shown in FIG.

As shown in FIG. 6C, the NAND circuit 21 outputs a low-level (L) signal only when both the A-phase and the B-phase are at the high level (H). Always outputs a high level (H) signal.

As shown in FIG. 6D, the NOR circuit 22 has a low-level (L) signal for both the A-phase and the B-phase.
, A high-level (H) signal is output, and in other cases, a low-level (L) signal is always output.

Each of the differentiating circuits 3A and 3B has a NAND
A rising edge of an output pulse from the circuit 21 and the NOR circuit 22 is detected and a pulse signal is output.

As described above, the output pulse of the differentiating circuit 3A is used as a count input of the counter 5, and the output pulse of the differentiating circuit 3B is used as a clear pulse of the counter 5. Therefore, when the encoder 2 is normal,
As shown in FIGS. 6E and 6F, the count input and the clear pulse are alternately input to the counter 5, so that
The count value of the counter 5 does not exceed 1.

On the other hand, when a disconnection occurs in the wiring related to the phase A of the encoder, the output of the phase A detected at the portion (a) is constant at a high level (H) due to the influence of the pull-up resistor 34. Becomes Therefore, only the count input from the differentiating circuit 3A is input to the counter 5, and the clear pulse from the differentiating circuit 3B is not input to the counter 5. Therefore, the count value of the counter 5 is
It increases according to the amount of rotation of.

The counter 5 generates a carry output when the count value exceeds a predetermined count. This carry output is output as an abnormality detection signal, and is input to an interlock device 15 provided in the power supply device 12 in the same manner as in the first embodiment, and the interlock device 15 supplies a current to the servo driver 14. To stop.

In the present embodiment, similarly to the first embodiment, since the output of the encoder is processed digitally, it is not necessary to perform analog adjustment of the abnormality detection device, and the influence of disturbance noise is eliminated. Hardly ever. For this reason, the abnormality of the encoder can be accurately and easily detected.

[0055]

As described above, according to the present invention,
Since the output of the encoder is digitally processed, there is no need to perform analog adjustment unlike a conventional abnormality detection device, and there is almost no influence from disturbance noise. For this reason, the abnormality of the encoder can be accurately and easily detected.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a robot including an encoder abnormality detection device according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a first embodiment of the encoder abnormality detection device, and is a block diagram illustrating a circuit configuration of the encoder abnormality detection device.

FIG. 3 is a diagram showing waveforms detected on the output side of each member when the encoder is normal.

FIG. 4 is a diagram showing a change in a waveform detected on the output side of each member when a disconnection occurs in a wiring of an encoder.

FIG. 5 is a diagram illustrating a second embodiment of the encoder abnormality detection device, and is a block diagram illustrating a circuit configuration of the encoder abnormality detection device.

FIG. 6 is a diagram showing a change in a waveform detected on the output side of each member when a disconnection occurs in a wiring of an encoder.

FIG. 7 is a block diagram showing a circuit configuration of a conventional encoder abnormality detection device.

[Explanation of symbols]

 2 Encoder 3, 3A, 3B Differentiating circuit 4 Traveling direction discriminating circuit 3 and 6, 3A and 21 First circuit 4, 3B and 22 Second circuit 5 Pulse counter 10 Feedback control system 11 Actuator 15 Interlock device

Claims (4)

[Claims] An abnormality detection device for an encoder that outputs an A phase and a B phase having a phase difference from each other, wherein the A phase and the B phase are input, and at least one of the outputs of the A phase and the B phase changes. A first circuit that generates a pulse output in synchronization with the rise or fall of the A-phase and the B-phase, the A-phase and the B-phase are input, and the outputs of the A-phase and the B-phase both change. A second circuit that generates a pulse output in synchronization with the rise or fall of the A-phase or the B-phase, and the pulse output from the first circuit is used as a count input, And a pulse counter that receives a pulse output from the circuit as a clear input.If the count value of the pulse counter exceeds a certain value, the encoder determines that the encoder is abnormal. Abnormality detection device. 2. An abnormality detection device for an encoder that outputs an A-phase and a B-phase having a phase difference with each other, wherein a rise or fall voltage change of the A-phase and the B-phase is detected. A differentiating circuit for generating a pulse output in synchronization with rising or falling; and a positive direction based on the phase difference between the A-phase and the B-phase only when the outputs of the A-phase and the B-phase are both changing. Or a traveling direction discriminating circuit that generates a pulse output representing a traveling direction in the reverse direction, and a pulse counter that uses the pulse output of the differentiating circuit as a count input and uses the pulse output of the traveling direction discriminating circuit as a clear signal, An abnormality detection device, wherein when the count value of the pulse counter becomes equal to or more than a certain value, the encoder is determined to be abnormal. 3. A control device for an actuator for driving a robot or the like, comprising: an encoder for detecting a traveling direction of the actuator and outputting an A phase and a B phase having a phase difference with each other; Or a differentiating circuit that detects a voltage change at the falling edge and generates a pulse output in synchronization with the rising or falling of the A-phase and the B-phase, and only when the A-phase and the B-phase are both changed,
A traveling direction discriminating circuit for generating a pulse output representing a forward traveling direction or a backward traveling direction based on the phase difference between the A phase and the B phase; A pulse counter that uses the pulse output of the encoder as a clear signal, a feedback control system that controls the actuator based on the A-phase and B-phase outputs of the encoder, and a pulse output of the traveling direction determination circuit; An interlock device for stopping the actuator when the count value becomes equal to or more than a predetermined value, and a control device for the actuator. 4. A method for detecting an abnormality of an encoder that outputs an A phase and a B phase having a phase difference with each other, wherein at least one of the outputs of the A phase and the B phase changes, the A phase or the B phase being changed. Generating a first pulse output synchronized with the rising or falling of the phase; and setting the rising or falling of the A or B phase only when both the outputs of the A and B phases are changing. Generating a synchronized second pulse output; detecting the first and second pulse outputs; and detecting the second pulse output while detecting the first pulse output a predetermined number of times. If no is detected, determining that the encoder is abnormal.