JP3173031B2 - Robot arm servo controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servo system having a position transmitting mechanism having uneven rotation, and more particularly to a servo control device for a robot arm for smoothly controlling an articulated industrial robot.

[0002]

2. Description of the Related Art Conventionally, a control device for smoothly controlling a robot arm is, for example, as shown in FIG. 2, a position control circuit 31, a speed control circuit 32, a current control circuit 33, a servomotor 34, and a speed detector 35. , A current detector 36, a speed reducer 37, and a robot arm 38. A value obtained by integrating the speed feedback value 40 detected from the speed detector 35 by the integrator 39 is used as a position feedback value 41, and the position control is performed based on the speed feedback value 40 and the current feedback value 42 detected from the current detector 36. , Speed control and current control. These feedback control circuits constitute a servo system for moving the robot arm according to the command value. In the speed control circuit 32, for example, speed proportional integration control is performed as shown in the block diagram of FIG. 3, and a value obtained by multiplying a difference between the speed command value 44 and the speed feedback value 40 by a speed proportional gain 46 and a difference Is set as the current command value 45. These gains are determined so that the servo system has the most stable optimum value, and the robot arm is controlled using the gains.

[0003]

However, in the above-mentioned conventional configuration, if the gain in the proportional integral control of the speed control circuit is set to exactly the same value at the time of resonance and at the time of non-resonance, the gain at the time of non-resonance is obtained. There is a problem that the resonance vibration becomes large even if the vibration is minimum. This resonance vibration occurs when periodic speed fluctuations due to external torque unevenness, such as motor cogging and reduction gear transmission errors, match the natural frequency of the robot arm, and the gain at the time of non-resonance remains unchanged. In this case, there is a problem that resonance vibration cannot be controlled due to a temporal phase difference between the speed command and the speed feedback. If the speed proportional integral gain is always fixed to a value for suppressing vibration, the vibration can be suppressed, but there is a problem that the tip vibration increases during non-resonance. A digital servo technique can be used to change the gain by speed, but since the natural frequency changes depending on the posture of the arm, resonance vibration cannot be determined only by speed, and the problem has not been solved.

An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide a servo control device of a robot arm which suppresses arm tip vibration at the time of resonance of the robot arm.

[0005]

In order to achieve the above-mentioned object, a servo control device according to the present invention provides a servo control device for operating a robot arm.
At the time of occurrence of resonance vibration, the determination of the resonance vibration state, the determination of the amplitude value and frequency of the tip vibration, and the speed proportional gain and the speed integration gain based on the determined amplitude value and frequency, respectively. Has a circuit for determining an optimum gain that makes the most stable, and performs an optimum control for minimizing the resonance vibration.

[0006]

According to the above-mentioned means, an optimum speed proportional integral gain that minimizes resonance vibration can be obtained, so that resonance vibration at the tip of the robot arm can be suppressed.

[0007]

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, 1 is a position control circuit, 2 is a speed control circuit, 3 is a current control circuit, 4 is a servo motor,
5 is a speed detector of the servo motor 4, 6 is a current detector of a current flowing through the servo motor 4, 7 is a resonance vibration determination circuit, 8 is an amplitude frequency determination circuit, 9 is a proportional integral gain determination circuit, 10 is a speed reducer, 11 is a robot arm, and 12 is a position loop integrator.

The servo control device configured as described above has a speed feedback value 16 sent from the speed detector 5 and a current feedback value sent from the current detector 6 when the resonance vibration of the robot arm 11 occurs. In step 18, the resonance vibration discriminating circuit 7 discriminates whether or not resonance vibration has occurred. If resonance vibration has occurred, a resonance vibration generation signal 19 is sent to the speed control circuit 2 and the amplitude frequency judgment circuit 8.

When the resonance frequency generation signal 19 is sent to the amplitude frequency judgment circuit 8, the amplitude value and frequency of the resonance vibration are judged from the speed feedback value 16 and the current feedback value 18, and the judgment value 20 is determined by the proportional integral gain. Decision circuit 9
Sent to The proportional-integral-gain determining circuit 9 can calculate the gain that minimizes the tip vibration of the robot arm 11 by a mathematical expression. The proportional-gain is determined for the amplitude, and the integral gain is determined for the frequency. The determined speed proportional integral gain 21 is sent to the speed control circuit 2. The speed control circuit 2 always uses the above-mentioned speed proportional integral gain 21 sent from the proportional integral gain determination circuit 9 when the resonance vibration generating signal 19 is sent from the resonance vibration discriminating circuit 7, and at other times. Use the preset normal gain. The determination of the resonance state, the determination of the amplitude value and frequency of the vibration, and the determination of the optimum gain are all dependent on digital servo technology, and the past of the current feedback value and the speed feedback value using a digital signal processor or the like. It can be realized by storage of information and high-speed calculation. The reason for determining the speed proportional gain from the amplitude value of the resonance vibration is to make the feedback value to the speed command value most stably follow. The reason why the speed integration gain is determined from the frequency of the resonance vibration is to prevent the vibration from increasing by changing the time phase difference between the speed command and the speed feedback at the time of resonance.
As described above, the control is performed in which the resonance of the robot arm is suppressed by using the optimum speed proportional integral gain at the time of normal operation and at the time of resonance vibration.

[0011]

As is apparent from the above description, the servo control apparatus for a robot arm according to the present invention is effective for suppressing vibration at the time of resonance of the robot arm, and can realize excellent servo performance. .

[Brief description of the drawings]

FIG. 1 is a block diagram of a servo control device of a robot arm for suppressing resonance vibration according to an embodiment of the present invention.

FIG. 2 is a block diagram of a conventional servo control device.

FIG. 3 is a block diagram of a speed proportional integration circuit;

[Explanation of symbols]

 2 Speed control circuit 7 Resonance vibration discrimination circuit 8 Amplitude frequency judgment circuit 9 Proportional integral gain decision circuit 11 Robot arm 19 Resonance vibration generation signal 20 Resonance vibration amplitude frequency judgment value 21 Speed proportional integral gain

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B25J 13/08 B25J 9/10 G05B 13/02 G05D 3/12 305 G05D 19/02

Claims (1)

(57) [Claims] 1. A resonance vibration discrimination circuit for detecting when a frequency of the tip vibration coincides with a mechanical natural frequency during operation of a robot arm and generating a resonance vibration generation signal, and a vibration amplitude. Amplitude-frequency determination circuit that detects the value and frequency, and amplitude that detects the value of the speed proportional gain and speed integration gain of the speed control circuit that is optimal for suppressing vibration when the resonance vibration generation signal is issued A servo control device for a robot arm, comprising: a proportional-integral-gain determining circuit that is calculated from a value and a frequency and set in a speed control circuit.