JPH0740268A - Robot arm controlling device - Google Patents

Abstract

PURPOSE:To provide a robot arm controlling device for sufficiently damping vibration. CONSTITUTION:A robot arm controlling device is provided with a driving means 5 for driving a robot arm 2 and a first control unit 6 for measuring the driving speed of the driving means 5, and controlling the driving speed of the driving means 5 on the basis of the deviation between the measured driving speed signal and the speed command signal of the driving means 5. Moreover, it is provided with an arm acceleration detecting unit 1 provided on the tip of the robot arm 2, a second control unit 3 for controlling vibrational component of arm speed on the basis of the arm acceleration signal from the arm acceleration detecting unit 1 and a calculator for correcting the output of the first control unit 6 on the basis of the output of the second control unit 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for controlling the drive of a robot arm.

[0002]

2. Description of the Related Art Conventionally, in order to control the drive of a robot arm, as shown in FIG. 2, a drive means including a motor and a speed reduction mechanism is provided at the joint part of the arm and the speed of the motor is controlled to control the speed of the arm. A method of controlling is done. In this control, the motor speed command signal ωm * is compared with the motor speed signal ωm, the deviation thereof is used as an input of the motor speed controller Cm, and the output control current i ^* is amplified by the power amplifier 5 to drive the motor. Feedback control to drive is being performed. Further, as the motor speed controller, a PI controller that normally performs proportional operation and integral operation is adopted.

However, it is physically impossible to form the deceleration mechanism with a completely rigid body, and besides the deceleration action, a spring or damping action and a delay in operation due to backlash occur, and the motor rotation passes through these. Vibration is generated in the operation of the arm. Further, when a disturbance is applied to the arm 2, the influence of the disturbance is transmitted to the motor through the speed reduction mechanism having the characteristics of the spring, damping, rattling, etc., so that the influence of the disturbance cannot be accurately detected in the motor section. Control does not work well. FIG. 4 shows the step response of a conventional arm. The response of this figure shows a vibration waveform of the speed of the arm when a stepwise motor speed command is given after 0.5 seconds and a stepwise disturbance is applied after 1.5 seconds. In the figure, the horizontal axis represents time (seconds) and the vertical axis represents velocity (rad / s).

[0004]

As described above,
The speed reduction mechanism described above has a drawback that the control cannot be performed well with respect to the arm speed command and the disturbance. The present invention solves this drawback and provides a vibration-free control device.

[0005]

In order to solve the above-mentioned problems, the present invention provides a driving means for driving a robot arm,
A controller for a robot arm, comprising a first controller for detecting a drive speed of the drive means and controlling the drive speed of the drive means based on a deviation between the detected drive speed signal and a speed command signal of a motor. An arm vibration detector provided on the arm, a second controller for controlling the vibration component of the arm speed based on information from the arm vibration detector, and the first control by the output of the second controller It is configured to include an arithmetic unit for correcting the output of the container.

[0006]

The motion including the vibration of the robot arm is detected by the acceleration sensor, and only the internal vibration component of this motion is negatively fed back and suppressed by the second controller and the arithmetic unit.

[0007]

FIG. 1 shows an embodiment of the present invention. In FIG. 1, the same numbers are attached to the same elements as in the conventional example. The arm 2 is rotatably fixed to the robot body 4 with a joint 7. The arm 2 is rotationally driven by a drive motor 5 having a speed reduction mechanism provided at the joint 7. The rotation speed of the drive motor is converted into an electric signal ωm by a rotation speed meter (not shown) and input to the adder 8. On the other hand, the speed command signal ωm * of the motor is input to the adder 8 and the deviation ε is output. This deviation is first
It is converted into a current command i ^* by the controller Cm. This first
The controller Cm is for controlling the motor speed and is composed of, for example, a PI type controller or the like. After the current command i ^* is amplified by the power amplifier 10,
It is applied to the input terminal of the drive motor 5 to drive it.

Further, the robot arm is provided with an acceleration sensor 1 at the tip of the arm, and the acceleration of the arm is measured. The signal from the sensor 1 is input to the arm speed controller Ca that is the second controller. The second controller Ca is for converting the vibration information of the arm detected by the sensor 1 into a velocity, and for removing the vibration of the band unnecessary for the operation of the arm itself from the motion of the arm. As the second controller Ca, for example, a transfer function G
(S) = (ωc ² · s / (s ² + 2ωc · s + ωc ² )) · K
A controller with is used. In the above transfer function, ωc represents a cutoff frequency, K represents a feedback gain, and s represents a Laplace operator. The transfer function can be configured by a bandpass filter in which a first-order lowpass filter having a cutoff frequency ωc and a first-order highpass filter are combined. The integral characteristic is obtained in a range higher than ωc. The output from the second controller is input to the arithmetic unit 9 provided between the output terminal of the first controller and the power amplifier 10,
A signal obtained by subtracting the output signal of the second controller from the output signal of the first controller is amplified by the power amplifier 10 to drive the drive motor 5.

In this embodiment, the acceleration sensor detects a motion including a vibration component, the second controller removes signals other than the vibration component, and only the signal corresponding to the vibration component is negative. Will be returned. Therefore, the vibration of the arm 2 is suppressed, and the speed control of the arm is easily performed. The effect of this embodiment is shown in FIG. FIG. 3 was performed under the same conditions as FIG. 4, and the vertical axis and the horizontal axis have the same scale. In these figures, a waveform of the arm speed ωa when a stepwise arm speed command is given after 5 seconds and a stepwise disturbance is applied to the arm after 1.5 seconds is shown. As can be seen from these figures, almost no vibration occurs in the device according to this embodiment. In this experimental example, the cutoff frequency ωc = 3 rad / s and the gain K = 38.

Although one embodiment of the present invention has been described above, the present invention is not limited to this. For example, the transfer function of the second controller is not limited to that described above, but may be a quadratic function of another form or a linear, cubic, or higher-order function. Further, the place where the signal of the vibration component is negatively fed back is not limited to the place of the embodiment, and any equivalent configuration may be used. For example, an inverse system of the motor speed controller may be incorporated in the arm speed controller to provide negative feedback at the same position as the motor speed signal. Further, although the present embodiment shows an example of one joint, it can be applied to a multi-joint robot arm.

[0011]

As described above, according to the present invention, in the speed control of the robot arm, since the vibration component is sufficiently attenuated by the negative feedback, it is possible to provide a good controller for the robot arm.

[Brief description of drawings]

FIG. 1 shows a block diagram of a robot arm controller according to an embodiment of the present invention.

FIG. 2 shows a block diagram of a conventional robot arm controller.

FIG. 3 shows an example of a step response of an embodiment according to the present invention.

FIG. 4 shows an example of a step response of a conventional robot arm controller.

[Explanation of symbols]

 1 ... Vibration detector 2 ... Arm 3 ... Arm speed controller 4 ... Robot main body 5 ... Drive motor 6 ... Motor speed controller 8, 9 ... Addition calculator 10 ...・ Power amplifier

Claims (3)

[Claims] 1. A drive means for driving a robot arm, a drive speed of the drive means is detected, and the drive speed of the drive means is controlled based on a deviation between the detected drive speed signal and a motor speed command signal. In a controller for a robot arm including a first controller, an arm vibration detector provided on the arm, and a second controller for controlling a vibration component of the arm speed based on information from the arm vibration detector. And a controller for correcting the output of the first controller according to the output of the second controller. 2. The controller for the robot arm according to claim 1, wherein the second controller has a function of converting vibration information from the detector into velocity. 3. The robot arm control device according to claim 1, wherein the vibration detector is an acceleration detector.