JPH1142578A - Control method and device for robot - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control so that compliance motion can be performed relating to fine external force with a good follow up property without using a force sensor, when external force is applied to a robot manipulator. SOLUTION: This control device for a robot comprises a servomotors 1 to 1N driving a robot manipulator, motor current detectors 2 to 2N detecting a current driving the servomotors 1 to 1N, motor rotational speed detectors 5 to 5N detecting a rotational speed of the servomotors 1 to 1N, disturbance load detectors 6 to 6N detecting disturbance load torque applied to the robot manipulator with this motor rotational speed and motor current, feed forward compensators 10 to 10N multiplying an moving command value by a feed forward gain to calculate a feed forward speed command value, and a force arithmetic device 13 adding fine initial torque to the detected disturbance load torque to calculate the moving command value when a robot manipulator is stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a robot control method and apparatus for driving a robot manipulator by a servomotor to flexibly escape an external force applied to an end effector of the robot, that is, a compliance operation.

[0002]

2. Description of the Related Art Conventionally, a robot controller (Japanese Patent Application Laid-Open No. Hei 6-39760) has been proposed which does not use a force sensor, and when an external force is applied to a robot manipulator, operates the manipulator in accordance with the external force to perform a compliance operation. Are known.

In this conventional example, when an external force is applied to a robot manipulator, the position is added to a position command value as a position change in accordance with a motor current command value increased compared to when the robot manipulator is stopped, and the robot manipulator is operated. A compliance operation can be performed by following an external force without installing a force sensor or the like at the tip of the robot.

[0004]

However, in the above conventional example, since the position command value is added to the position command value as a position change in accordance with the motor current command value increased compared to when the motor is stopped, the vertical tracking performance is particularly poor. Articulated robots have poor ability to follow external forces, and when the robot is stopped, the static friction of the reducer is large. There was a problem that can not be.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems. In a robot which performs a flexible operation when an external force is applied to a robot manipulator without using a force sensor, that is, a robot which performs a compliance operation, the followability to the external force is improved. It is an object of the present invention to provide a control method and apparatus for a robot capable of performing a compliance operation in response to an external force even when the external force applied to the manipulator is minute.

[0006]

In order to achieve this object, a first means of the present invention is to detect a motor current value of a servomotor driving a robot manipulator, to detect a motor rotation speed of the servomotor, A disturbance load torque applied to the robot manipulator is detected from the motor current value and the motor rotation speed, a compliance operation command value is calculated from the detected disturbance load torque and output to a position controller, and a compliance speed is calculated from the compliance operation command value. A robot control method comprising calculating a command value and outputting the command value to a speed controller, performing a feedforward compensation calculation, and performing a compliance operation.

The second means of the present invention calculates the compliance speed command value by multiplying a compliance operation command value by a feed forward gain set by a robot program in the feed forward compensation calculation of the first means, and calculates a feed speed compensation value. It is a method to do.

Next, a third means of the present invention detects a motor current value for driving a servomotor of the robot manipulator, and detects a motor rotation speed of the servomotor,
A disturbance load torque applied to the robot manipulator is detected from the motor current value and the motor rotation speed, and a small initial torque is added to the detected disturbance load torque when the robot manipulator is stopped to calculate a compliance operation command value. And performing a compliance operation.

Next, a fourth means of the present invention is a method in which the value of the minute initial torque of the third means is set by a robot program, and a compliance operation command value is calculated.

Next, a fifth means of the present invention is a method in which the sign of the minute initial torque of the third means is set by a robot program and a compliance operation command value is calculated.

Next, a sixth means of the present invention comprises a servomotor for driving a robot manipulator, a motor current detector for detecting a current for driving the servomotor, and a motor rotation for detecting a rotation speed of the servomotor. A speed detector, a disturbance detector for detecting a disturbance load torque applied to the robot manipulator from the motor rotation speed and the motor current, a position controller for controlling a position of the servomotor, and controlling a speed of the servomotor. A speed controller, a force calculator for calculating a compliance operation command value from the detected disturbance load torque and outputting the same to the position controller, and a feed for calculating a compliance speed command value from the compliance operation command value and outputting the same to the speed controller It has a forward compensator.

Next, a seventh means of the present invention is characterized in that the feedforward compensator of the sixth means calculates a compliance speed command value by multiplying a compliance operation command value by a feedforward gain set by a robot program. It was done.

Next, an eighth means of the present invention comprises a servomotor for driving a robot manipulator, a motor current detector for detecting a current for driving the servomotor, and a motor rotation for detecting a rotation speed of the servomotor. A speed detector, a disturbance detector that detects a disturbance load torque applied to the robot manipulator from the motor rotation speed and the motor current, and a small initial torque added to the detected disturbance load torque when the robot manipulator is stopped. And a force calculator for calculating a compliance operation command value.

Next, a ninth means of the present invention is configured such that the force calculator of the eighth means sets a value of a minute initial torque by a robot program and calculates a compliance operation command value.

Next, a tenth means of the present invention is configured such that the force calculator of the eighth means sets a sign of a minute initial torque by a robot program and calculates a compliance operation command value.

[0016]

According to the above-mentioned means, according to the method of the first means of the present invention and the apparatus of the sixth means for using the method, when an external force is applied to the robot manipulator without using a force sensor, It has a function of performing a compliance operation with good followability to external force.

Further, according to the method of the second means of the present invention and the apparatus of the seventh means for using the method, when an external force is applied to the robot manipulator without using a force sensor, the robot can follow the external force. It has a function of performing a compliance operation with good followability to external force by being changed by a program.

Further, according to the method of the third means of the present invention and the apparatus of the eighth means for using the method, even when the external force applied to the manipulator is very small, there is an effect that the compliance operation can be performed in response to the external force. .

Further, according to the method according to the fourth means of the present invention and the apparatus according to the ninth means for using the method, the value of the small initial torque is set by a robot program, and even when the external force applied to the manipulator is small, It has the function of performing a compliance operation in response to an external force.

Further, according to the method according to the fifth aspect of the present invention and the apparatus according to the tenth aspect for using the method, the sign of the minute initial torque is set by a robot program, and even when the external force applied to the manipulator is minute. It has the function of performing a compliance operation in response to an external force.

FIG. 1 shows an embodiment of the present invention.
This will be described with reference to FIG.

As shown in FIG. 1, this embodiment employs servo motors 1 to 1N for driving a robot manipulator.
And motor current detectors 2 to 2N for detecting currents for driving the servo motors 1 to 1N. The rotation of the servo motors 1 to 1N is detected in the servo devices 3 to 3N based on signals from the rotary encoders 4 to 4N. Motor rotation speed detectors 5 to 5N for detecting the speed, and disturbance detectors 6 to 6 for detecting a disturbance load torque applied to the robot manipulator from the motor rotation speed and the motor current.
N, a feedforward compensator 10 that calculates a feedforward speed command value by multiplying the compliance command value by a feedforward gain, a position controller 9 that controls the position of the servomotor 1, and a speed of the servomotor 1 The arithmetic unit 1 includes a speed controller 8 and a servo amplifier 7 that controls and drives the current of the servo motor 1.
4, a normal operation calculator 1 for calculating normal operation command values R1 to RN, which are operation amounts of a normal playback operation or the like.
2, an initial torque commander 11 which is instructed by the robot program to generate a value and sign of a minute torque, and a force control for calculating a compliance operation command value from the disturbance load torque detected by the disturbance detectors 6 to 6N and the minute initial torque. When a disturbance load torque T1 to TN is applied to the robot manipulator, the calculation device 7 calculates compliance operation command values S1 to SN from the detected disturbance load torques T1 to TN, Set the manipulator to the disturbance load torque T1 to TN
It is configured to operate in a direction to escape from the vehicle.

The position controller 9 calculates the speed command value by subtracting the operation amount output from the rotary encoder 4 from the sum of the normal operation command values R1 to RN and the compliance operation command values S1 to SN and multiplying the sum by a position loop gain. To the speed controller 8. The speed controller 8 calculates the actual speed from the sum of the feedforward speed command value calculated by the feedforward compensator 10 and the speed command value calculated by the position controller 8 (calculated from the time difference value of the operation amount output from the rotary encoder 4). ) Is multiplied by the speed loop gain to calculate a current command value, which is sent to the servo amplifier 7. The servo amplifier 7 controls the motor current from the current command value calculated by the speed controller 7 and the motor current value sent from the motor current detector 2,
The servo motor 1 is controlled.

Since the robot is usually composed of a plurality of N-axis manipulators, the servomotors 1 to 1N
, The rotary encoders 4 to 4N and the servo devices 3 to 3N are required for N axes.

The disturbance detector 6 calculates a disturbance load torque T1 or TN by subtracting a value obtained by multiplying a motor current by a time differential value of the motor rotation speed and load inertia.

FIG. 2 is a diagram for explaining the operation of the feedforward compensator 10. FIG. 2 shows characteristics of the speed command value when the position command value is given in a step-like manner.
Normally, in the case of a vertical articulated robot, the rigidity of the joint structure is not very high, so that the position loop gain is 15 to 20 [1 /
S], and if there is no feedforward compensation, the speed command value is 100 msec as shown in FIG.
This delays the above, resulting in poor position tracking. On the other hand, when feedforward compensation is applied (feedforward gain of about 40%), the delay is substantially eliminated and the position approaches the position command value, and the position following ability is improved. However, if the feed forward gain is set too high, hunting tends to occur. When the rigidity of the joint structure is not so high in a vertical joint type robot, if feedforward compensation is added to the position command value of normal operation, it tends to be hunting at high speed operation, so feedforward compensation only for compliance operation where speed does not increase To improve the position followability of the compliance operation. In addition, if the setting of the feed forward gain at this time can be changed by the robot program, the ability to follow an external force can be easily changed.

FIG. 3 is a diagram for explaining the method of applying a small initial torque.
Shown in FIG. 3 shows a general vertical articulated robot manipulator, in which a first axis is a turning axis and moves in the direction of the arrow in the figure. For example, when an external force is applied to the manipulator from the outside in the direction of the external force shown in FIG. 3, an external force load torque is applied to the first axis in the direction in which the load shown in FIG. 3 is applied.
Since there is static friction in the speed reducer of the first shaft and the like, the compliance operation is not performed until the external load torque overcomes this static friction. It depends on the size and structure of the robot manipulator, but it requires about 2% of the maximum torque to operate.
The above disturbance load torque is required. In the case where the direction in which disturbance is applied is known in advance and the robot is stopped, a small initial torque is applied in the direction in which the load is applied in FIG. This is a size that does not overcome the static friction. (If you apply more than the static friction, the robot will work even if no external force is applied.) For example, if you need 2% of the maximum torque to overcome the static friction,
A small initial torque of 1.5% is applied in the direction in which a load is applied. Then, an external force is applied to the robot manipulator, and when a disturbance load torque of 0.5% or more is generated on the first axis, the compliance operation becomes possible. Compliance operation is possible. However, since the static friction tends to change depending on the posture of the robot and the state of the reduction gear, care must be taken in setting the value of the minute initial torque. When the direction of the external force is opposite to the direction in which the small initial torque is applied, a larger external force is required than when no small initial torque is applied. In addition, if the direction and value for applying the small initial torque can be set by a robot program, the static operation can be easily changed and the compliance operation can be performed when the static friction is different or the direction in which an external force is applied is different.

[0028]

As described above, according to the method of the first means of the present invention and the apparatus of the sixth means for using the method,
A servo motor that drives the robot manipulator, a motor current detector that detects the current that drives the servo motor, a motor rotation speed detector that detects the rotation speed of the servo motor, and a motor rotation speed and motor current that apply to the robot manipulator. A disturbance detector that detects the disturbance load torque, a position controller that controls the position of the servo motor, a speed controller that controls the speed of the servo motor, and a compliance operation command value calculated from the detected disturbance load torque. External force is applied to the robot manipulator without using a force sensor by providing a force calculator that outputs to the position controller and a feedforward compensator that calculates the compliance speed command value from the compliance operation command value and outputs it to the speed controller. Good compliance and smooth compliance In which an excellent effect of being able to work.

According to the method of the second means of the present invention and the apparatus of the seventh means for using the method, the first method
The feedforward compensator of the means multiplies the compliance operation command value by the feedforward gain set by the robot program to calculate the compliance speed command value, so that the followability to external force can be easily changed by the robot program. Therefore, the compliance operation can be performed smoothly and the compliance operation can be performed smoothly.

Further, according to the method of the third means of the present invention and the apparatus of the eighth means for using the method, a servo motor for driving a robot manipulator and a motor current detection for detecting a current for driving the servo motor are provided. When the robot manipulator is stopped, a motor rotation speed detector that detects the rotation speed of the servo motor, a disturbance detector that detects the disturbance load torque applied to the robot manipulator from the motor rotation speed and the motor current, and Equipped with a force calculator that adds a small initial torque to the detected disturbance load torque and calculates the compliance operation command value, so that even when a small external force is applied to the robot manipulator without using a force sensor, it can respond to external force This provides an excellent effect that a compliance operation can be performed.

According to the method of the fourth aspect of the present invention and the apparatus of the ninth means for using the method, the third aspect
The value of the small initial torque of the means is set by the robot program, and the configuration is such that the compliance operation command value is calculated. This provides an excellent effect that a compliance operation can be performed.

According to the method of the fifth aspect of the present invention and the apparatus of the tenth aspect for using the method, the sign of the small initial torque of the third means is set by a robot program, and the compliance operation command is set. By adopting the method of calculating the value, the superior effect that the sign of the minute initial torque can be easily changed by the robot program and the compliance operation can be performed for the minute external force in the direction of the designated sign Is played.

[Brief description of the drawings]

FIG. 1 is a block diagram of a robot control device according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram of a speed command value when a position command value is given in a step form in the embodiment.

FIG. 3 is a diagram for explaining a small initial torque adding method in the embodiment.

[Explanation of symbols]

 1 to 1N Servo motor 2 to 2N Motor current detector 5 to 5N Motor rotation speed detector 6 to 6N Disturbance detector 8 Speed controller 9 Position controller 10 Feed forward compensator 13 Force control calculator S1 to SN Compliance operation command Value T1 to TN Disturbance load torque

Claims (10)

[Claims] 1. A motor current value of a servomotor for driving a robot manipulator is detected, a rotation speed of the servomotor is detected, and a disturbance load torque applied to the robot manipulator is detected from the motor current value and the motor rotation speed. Then, a compliance operation command value is calculated from the detected disturbance load torque and output to the position controller, a compliance speed command value is calculated from the compliance operation command value and output to the speed controller to perform feedforward compensation, and compliance is performed. A method for controlling a robot, which performs an operation. 2. The robot control method according to claim 1, wherein a compliance speed command value is calculated by multiplying the compliance operation command value by a feedforward gain set by a robot program to perform feedforward compensation. 3. A motor current value of a servomotor for driving the robot manipulator is detected, a rotation speed of the servomotor is detected, and a disturbance load torque applied to the robot manipulator is detected from the motor current value and the motor rotation speed. A robot control method comprising: performing a compliance operation by calculating a compliance operation command value by adding a small initial torque to the detected disturbance load torque when the robot manipulator is stopped. 4. The robot control method according to claim 3, wherein a value of the minute initial torque is set by a robot program and a compliance operation command value is calculated. 5. The robot control method according to claim 3, wherein a sign of the minute initial torque is set by a robot program and a compliance operation command value is calculated. 6. A servo motor for driving a robot manipulator, a motor current detector for detecting a current for driving the servo motor, a motor rotation speed detector for detecting a rotation speed of the servo motor, and the motor rotation speed. And a disturbance detector for detecting a disturbance load torque applied to the robot manipulator from the motor current, a position controller for controlling the position of the servo motor, a speed controller for controlling the speed of the servo motor, and a detected disturbance. A force calculator that calculates a compliance operation command value from the load torque and outputs the value to the position controller; and a feedforward compensator that calculates a compliance speed command value from the compliance operation command value and outputs the value to the speed controller. Robot control device to do. 7. The robot controller according to claim 6, wherein the feed forward compensator is configured to calculate a compliance speed command value by multiplying the compliance operation command value by a feed forward gain set by a robot program. 8. A servo motor for driving a robot manipulator, a motor current detector for detecting a current for driving the servo motor, a motor rotation speed detector for detecting a rotation speed of the servo motor, and the motor rotation speed. And a disturbance detector that detects the disturbance load torque applied to the robot manipulator from the motor current, and a force that calculates the compliance operation command value by adding a small initial torque to the detected disturbance load torque when the robot manipulator is stopped. A robot controller that has a computing unit and performs compliance operations. 9. The control device for a robot according to claim 8, wherein the force calculator sets a value of a minute initial torque by a robot program and calculates a compliance operation command value. 10. The robot controller according to claim 8, wherein the force calculator sets a sign of the minute initial torque by a robot program and calculates a compliance operation command value.