JPH10315173A - Abnormality detector for robot - Google Patents

Abstract

PROBLEM TO BE SOLVED: To instantly detect a deviation from an orbit of a position command, reduce erroneous detection at normal operation time, and realistically attain high performance by comparing an output signal from a position control model part with a position signal to show an actual position of an electric motor, and detecting it as abnormality of a robot when its difference is not less than a prescribed value. SOLUTION: An encoder as a sensor to detect turning angle data of an electric motor to operate a robot, is provided, and a position control part to decide a position control quantity on the basis of a position command and the turning angle data from the sensor, is provided. A secondary filter 13 as a position control model part to which the position command is inputted, a secondary filter 13 to detect the robot as abnormal when its difference is not less than a prescribed value by comparing an output signal from this position control model part 13 with a position signal to show an actual position of the electric motor and an abnormality detecting means composed of a comparator 15, an absolute value converting part 16 and a subtracter 17, are provided. Therefore, erroneous detection at normal operation time of the robot can be reduced, and high performance can be realistically attained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a robot abnormality detecting device.

[0002]

2. Description of the Related Art Generally, a robot has a motor for turning an arm and a feedback control system (servo system) having a sensor for detecting rotation angle data of the motor.
And a proportional and proportional integral type position controller for determining a position control amount based on the position command and the rotation angle data from the sensor. The position of the electric motor is controlled by the control amount from the position control amount. Control is performed.

[0003] All industrial robots have a function of monitoring an abnormal operation such as a trajectory deviation or the like and stopping the operation by an emergency stop means when an abnormal operation occurs. This function is, for example, abnormal speed of the motor,
Abnormality of the position deviation between the actual position of the motor and the position command (deviation of the position command with respect to the trajectory), abnormal current command value of the position control unit, overload of the motor, and the operation is stopped by the emergency stop means. Things. When detecting deviation from the position command trajectory during these abnormal operations,
Conventionally, it is determined whether or not the actually measured position deviation is abnormal based on the fixed upper limit value of the position deviation.

[0004]

In the above-mentioned robot, the position deviation usually increases as the speed of the motor increases, even in a normal operation, due to the characteristics of the feedback control system. The value changes every moment, such that the value decreases as the value decreases. As described above, if it is determined whether the actual value of the position deviation that changes every moment is abnormal based on the upper limit of the fixed position deviation, the detection of the deviation of the position command from the trajectory is delayed. This causes the problem that

Therefore, a method of changing the upper limit value (abnormality judgment value) of the position deviation according to the magnitude of the speed command is taken.
Although the above problems can be greatly improved, adjusting the gain of the servo system increases the trouble of adjusting the servo system in order to increase the accuracy of abnormality detection, and the conventional proportional and proportional integral type position control At present, even if the gain of the servo system is adjusted, a large margin is not taken, and an abnormality is erroneously detected unless a large margin is taken. When the abnormality detection accuracy is low, the time from when the robot abnormally operates to when the operation is stopped becomes longer, and the distance traveled by the abnormal operation of the robot becomes longer accordingly.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a realistic and high-performance robot abnormality detecting device capable of instantaneously detecting a deviation of a position command from a trajectory and having less erroneous detection during normal operation. .

[0007]

According to one aspect of the present invention, there is provided an electric motor for operating a robot and a sensor for detecting rotation angle data of the electric motor. A position control unit that determines the position control amount based on the rotation angle data from the sensor,
In the robot abnormality detection device configured to perform the position control of the electric motor by the control amount from the position control unit, the position command is input by modeling the entire motor and its load and the position control unit. Abnormality control means for comparing an output signal from the position control model unit with a position signal indicating an actual position of the electric motor, and detecting a robot abnormality when the difference is equal to or greater than a predetermined value. , The deviation of the position command from the trajectory can be instantaneously detected, the number of erroneous detections during normal operation is small, and it is realistic and high performance.

According to a second aspect of the present invention, in the robot abnormality detecting apparatus according to the first aspect, the position control unit is a position servo system having a closed loop and configured by a pole arrangement system including a disturbance compensation function, The position control model unit is a structure in which the motor, its load, and the position control unit as a whole are configured as a secondary model. Since the model is simple, a filter device to be added can be simple, and gain adjustment can be performed. It does not take much effort. In addition, modeling accuracy is high because the pole arrangement system includes a disturbance compensation function. The deviation of the position command from the trajectory can be detected instantaneously, and there is little erroneous detection during normal operation, and the system is realistic and has high performance.

[0009]

FIG. 1 shows an embodiment of the present invention. This embodiment is an embodiment of the first and second aspects of the present invention. The electric motor (motor) and its load system 11 include an electric motor for turning the robot arm and a load such as an arm turned by the electric motor. The electric motor is controlled by the control device 12. This control device 12
Is constituted by a feedback control system (servo system) having a sensor for detecting rotation angle data of the electric motor, and has a disturbance compensation function of determining a position control amount based on a position command and rotation angle data from the sensor. It is equipped with a pole-positioned proportional and proportional-integral type position controller, and controls the position of the electric motor by a control amount from the position controller.

In the control device 12, the closed loop portion of the position control section is constituted by a pole arrangement system having a disturbance compensation function, and the characteristics of the secondary model based on the poles in which the control device 12, the motor and its load system 11 are arranged as a whole are arranged. To have Here, this pole arrangement system is disclosed in JP-A-6-270079,
The Japan Society of Precision Engineering, Technical Committee on Ultra-Precision Positioning, Preprints, "Robust Decoupling Control of Articulated Robots" 1996
It has been known since February. When a position command indicating the trajectory at that time is input to the control device 12, the robot moves to the actual position, and the response characteristic becomes the characteristic of the secondary model. The secondary filter 13 includes a position control system 1 whose transfer function is composed of the control device 12, the motor, and the load system 11.
4 transfer function m1 · m2 / ｛(s + m1) (s + m
2) Same transfer function m1 · m2 / ｛(s + m1) (s) as｝
+ M2)}, and is a position control model unit including a secondary filter that models the position control system 14 so as to have the characteristics of the secondary model. The same position command as that of the control device 12 is input to the secondary filter 13.

Therefore, during normal operation, a position signal indicating the actual position of the motor and its load system 11, for example, a position signal obtained from the rotation angle data from the sensor and a position signal output from the secondary filter 13 Are almost the same. These position signals are compared by the comparator 15 to determine the difference between them, and the absolute value of the difference is calculated by the absolute value converter 16.

The absolute value obtained by the absolute value conversion section 16 is subtracted from a fixed threshold value set in a memory or the like by a subtractor 17, and the output signal of the subtracter 17 indicates the position of the electric motor and its load system 11 If it deviates from the trajectory of the position command, it becomes negative polarity and is output to the emergency stop device 18 as an abnormal signal. The emergency stop device 18 stops the operation of the robot in response to an abnormal signal (a negative output signal) from the subtractor 17.

Here, since the position control system 14 is constituted by a pole arrangement system and the entire position control system 14 is represented by a secondary model, the characteristics during normal operation are very accurate to the characteristics of the secondary filter 13. Good agreement. Therefore, even if the fixed threshold value is reduced, erroneous detection of deviation of the position command from the trajectory does not occur, and only abnormal operation due to deviation from the true position command trajectory can be instantaneously detected.

FIG. 2 and FIG. 3 show the configuration of the control device 12. The arm 19 of the robot is driven by an electric motor 20 composed of a servomotor. The control device 12 converts a current command from a digital value to an analog value by a D / A converter (D / A converter).
/ AC) 21, a driver 22 for driving the electric motor 20 according to a current command from the D / AC 21, and a sensor for detecting rotation angle data of the electric motor 20 and generating a pulse signal every predetermined rotation of the electric motor 20. Encoder 23
A sensor 24 for performing various types of detection of the robot, a position control unit 25 including a microprocessor system, a counter 26 for counting a pulse signal from the encoder 23 for each rotation of the electric motor 20, a disconnection of the robot, overcurrent,
An error detection unit 27 that detects an error such as an overload of the electric motor 20 or an abnormal temperature, the comparator 15, the absolute value conversion unit 16, the subtractor 17, and the emergency stop device 18 are provided.

The microprocessor system 25 includes a microprocessor (MPU) 28, a ROM 29, and a RAM.
30, a flash memory 31, a shared memory 32, a DI / DO port 33, and an SCI port 34. This microprocessor system 25
Functionally, a pole arrangement controller 35 having a disturbance compensation function for performing position control, a feedforward controller 36,
It has a limiter 38 and a position detector 41. The pole arrangement controller 35 has a proportional unit 37, a first control filter 39, a second control filter 40, and an adder 42.

The MPU 28 operates based on programs and data stored in a ROM 29, and
32, the current command is determined based on the position command and the count value of the counter 26 and output to the D / AC 21 to control the electric motor 20 to control the arm 19, and to transmit information from the sensor 24 to DI / The operation status of the robot is monitored by taking it in from the DO port 33, and the error detection signal from the error detection unit 27 is taken in by the DI / DO port 33 to disconnect the robot, overcurrent, and the motor 2
When an error such as an overload of 0 or abnormal temperature occurs, the operation of the robot is stopped by the emergency stop device 18, and information is exchanged with a host computer 43 including a personal computer (PC) as an external device via the SCI port 34. Or Information is read from and written to the shared memory 32 by the PC 43.

The arm 19 is rotated by being driven by the electric motor 20, and the encoder 23 detects the rotation angle data of the electric motor 20, and generates a pulse signal every time the electric motor 20 rotates by a predetermined angle. The counter 26 counts a pulse signal from the encoder 23 for each rotation of the motor 20, and the position detector 41 detects the rotation position of the motor 20 from the count value of the counter 26. The pole arrangement controller 35 includes a signal obtained by multiplying the position command by the proportional unit 37 and a feedforward controller 36.
, The output signal of the first control filter 39 to which the signal from the pole arrangement controller 35 is input, and the output signal of the second control filter 40 to which the output signal of the position detector 41 is input Are added by the adder 42 to obtain a current command.

The current command from the pole arrangement controller 35 is limited by the limiter 38 and converted into an analog value by the D / AC 21, and the driver 22 drives the electric motor 20 according to the current command from the D / AC 21. This position control unit 2
5 has a characteristic of a secondary model based on the poles in which the closed loop portion is constituted by the pole arrangement system as described above, and the control device 12, the electric motor, and the load system 11 as a whole are arranged. The position signal (including the angle signal) input from the position control system 14 and the secondary filter 13 to the comparator 15 is
The position signal from the position detector 41 in the position control system 14 may be the same as the position signal from the position detector 41 in the position control system 14 and the position signal from the secondary filter 13. And so on.

In this embodiment, since the closed loop portion of the position control section is constituted by a pole arrangement system, the threshold value for abnormality detection can be reduced (detection accuracy can be increased) while erroneous detection during normal operation is reduced. . In addition, the deviation of the position command from the trajectory according to the dynamic operation at that time can be detected instantaneously, and the abnormal operation (runaway) of the robot can be detected and stopped early, and the damage due to the abnormal operation can be detected. Can be kept to a minimum. Further, a comparator 15, an absolute value converter 16, subtractors 17 and 2
The secondary filter 13 is realized by adding software to the microprocessor system 25, and the secondary filter 13
Is also as small as "2", so that it can be realized very easily and at low cost, and has high practicality.

As described above, this embodiment is an embodiment of the first aspect of the present invention, in which an electric motor 20 for operating a robot and an encoder as a sensor for detecting rotation angle data of the electric motor 20 are provided. And a position control unit 25 for determining a position control amount based on the position command and the rotation angle data from the sensor 23. The position control of the electric motor 20 is controlled by the control amount from the position control unit 25. In the robot abnormality detection device, the position control unit 25 is modeled and a secondary filter 13 as a position control model unit to which the position command is input, and an output from the position control model unit 13 Comparing the signal with a position signal indicating the actual position of the motor 20,
When the difference is equal to or greater than a predetermined value, the secondary filter 13 detects the abnormality of the robot, the comparator 15, the absolute value converter 16, and the subtractor 17 are provided. The deviation of the position command from the trajectory according to the dynamic operation can be instantaneously detected, and the erroneous detection during the normal operation is small, and it is realistic and has high performance.

This embodiment is an embodiment of the second aspect of the present invention. In the abnormality detecting device for a robot according to the first aspect, the position control section 25 is a position servo system having a closed loop. And the position control model unit 13 is configured as a secondary model of the position control unit, so that the deviation of the position command from the trajectory can be detected instantaneously, It is practical and high performance with few false detections during operation.

The position control unit 25 is, for example, disclosed in
In the articulated robot, three functions of disturbance compensation, decoupling, and pole assignment to a desired model (transfer function) for each axis are provided in the same manner as that described in JP-A-270079. An output signal (control amount) to the D / Ac 21 is calculated from a position command using a predetermined parameter so that a transfer function matrix leading to rotation angle data obtained from the encoder 23 becomes a desired transfer function matrix having no interference element. You may do so.

Also in this case, since the position control system 14 is a secondary model, the secondary filter 13 is used.
Also, the secondary filter 13, the comparator 15, the absolute value converter 1
The 6 and the subtracter 17 can be used not only for deviation from the trajectory of the position command, but also for early collision detection in a case where intentional collision occurs.

[0024]

As described above, according to the first aspect of the present invention, there is provided a motor for operating a robot, a sensor for detecting rotation angle data of the motor, a position command and a rotation angle from the sensor. A position control unit for determining a position control amount based on the data and a position control unit for controlling the position of the motor based on the control amount from the position control unit. And a position control model unit in which the entire position control unit is modeled and the position command is input, and an output signal from the position control model unit is compared with a position signal indicating an actual position of the electric motor. And an abnormality detecting means for detecting an abnormality of the robot when the difference is equal to or more than a predetermined value. At least false positives is a realistic and high-performance.

According to a second aspect of the present invention, in the abnormality detecting device for a robot according to the first aspect, the position control unit is a position servo system having a closed loop and configured by a pole arrangement system having a disturbance compensation function. Since the position control model unit is configured as a secondary model of the motor and its load and the position control unit as a whole, a deviation of the position command from the trajectory can be detected instantaneously, and an error during normal operation can be detected. Realistic and high performance with little detection.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a control device according to the embodiment.

FIG. 3 is a block diagram showing a functional configuration of a control device according to the embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 11 motor / load system 12 control device 13 secondary filter 14 position control system 15 comparator 16 absolute value conversion unit 17 subtractor 18 emergency stop device 20 motor 23 encoder 25 position control unit

Claims (2)

[Claims] An electric motor for operating a robot, and a position control unit having a sensor for detecting rotation angle data of the electric motor and determining a position control amount based on a position command and the rotation angle data from the sensor. In the robot abnormality detection device, wherein the position of the electric motor is controlled by the control amount from the position control unit, the motor and its load and the position control unit are modeled as a whole. A position control model unit to which a position command is input is compared with an output signal from the position control model unit and a position signal indicating the actual position of the electric motor. An abnormality detection device for a robot, comprising: 2. The robot abnormality detecting device according to claim 1, wherein the position control unit is a position servo system having a closed loop and configured by a pole arrangement system including a disturbance compensation function, and the position control model unit is provided. An abnormality detection device for a robot, wherein the entirety of the motor, its load, and the position control unit are configured as a secondary model.