JPH0583971A - Servo motor oscillation prevention method - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a method of preventing oscillation at the time of starting a servo motor. [Structure] When the servo motor is started from the stop to the maximum speed, whether the value 4 obtained by multiplying the current deviation value 10 between the current command value 1 and the current feedback value 2 by the current gain 3 in the preceding stage exceeds the preset upper limit value. If it exceeds the limit, the limiter 6 limits it to the upper limit value and multiplies it with the current gain 8 of 1 or less in the subsequent stage to output the current output value 9. By multiplying the gain by 7 and outputting the current output value 9, oscillation at the start of the servo motor is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of preventing oscillation of a servomotor for driving an NC, an articulated industrial robot or the like and smoothly controlling it.

[0002]

2. Description of the Related Art A servo driver for driving a servo motor, as shown in FIG. 2, has a position control circuit 31, a speed control circuit 32, and a current control circuit in order to control the position and speed of a mechanical system with high precision. 33, a servo motor 34, a speed detector 35, and a current detector 36. Reference numeral 37 is a driven mechanical system, and 38 is an integrator. Position command value 43,
Speed feedback value 4 detected from the speed detector 35
The value obtained by integrating 0 by the integrator 38 is used as the position feedback value 41, and the position control circuit 31 performs position control. The speed control circuit 32 performs speed control based on the speed command value 44 output from the position control circuit 31 and the speed feedback value 40. The current control circuit 33 performs current control based on the current command value 45 output from the speed control circuit 32 and the current feedback value 42 detected by the current detector 36.
In the current control, as shown in FIG. 3, a value obtained by multiplying the current deviation amount 47 between the current control value 45 and the current feedback value 42 by the current gain (KIP) 46 is supplied to the servo motor as the current output value 48, and the control is performed. Is going.

[0003]

However, in the above-mentioned conventional configuration, the current command value reaches the upper limit value when the servo motor is rapidly started from the stop to the maximum speed, and the current output value becomes the maximum due to the delay of the current feedback. . At this time, the system becomes unstable with small motors with small inertia,
Oscillation was likely to occur, although temporarily until the speed stabilized. This oscillation occurs only at the time of starting, but exceeds the allowable current value of the motor at the time of oscillation, so that the motor is deteriorated by repeating the starting and stopping for a long time. Oscillation can be prevented by reducing the current gain, but simply reducing the gain will reduce the steady-state gain, leaving control performance problems.

The present invention solves the above-mentioned conventional problems, and provides a method of preventing oscillation of a servomotor, which prevents oscillation at startup without degrading control performance and prevents deterioration of the motor. With the goal.

[0005]

In order to achieve the above object, according to the present invention, it is determined in the current control circuit whether or not the multiplication value of the current gain of the preceding stage and the current deviation amount exceeds the upper limit value of the current, If the limit is exceeded, limit the value to the upper limit value, set the value multiplied by the gain of the latter stage as the current output value, and set the gain of the latter stage to an appropriate value of 1 or less so that the maximum speed is reached from the time of stop. When starting, the current output value does not reach the upper limit. When the multiplication value of the current gain of the previous stage and the current deviation value does not exceed the upper limit value, the normal gain is output.

When the current deviation amount reaches the upper limit,
The speed deviation amount in the speed control circuit also exceeds the upper limit and the value is limited, so the speed gain is substantially small, so by setting a limiter for the current gain and setting the current gain of the latter stage to an appropriate value, The relationship between the speed gain and the current gain is properly maintained.

[0007]

By the above method, the current output value is prevented from reaching the upper limit value when the mechanical system is started from the stop to the maximum speed to prevent the servo motor from oscillating and deteriorating, and at the time of steady operation. The resolution of can be limited without loss.

[0008]

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a current control circuit of a servo driver used in the present invention. In FIG. 1, 1 is a current command value, 2 is a current feedback value, 3 is a previous stage current gain (KIP1), 4 is a previous stage current calculation value, 5 is an upper limit value determination circuit, 6 is a limiter, and 7 is a normal time. The current gain (KIP2) in the latter stage, 8 is the current gain (KIP3) in the latter stage at the time of limit processing, 9 is the current output value, and 10 is the current deviation value.

The operation of the current control circuit configured as described above is as already described in the section of the means for solving the problem, but the current command value 1 and the current feedback value 2 are used.
The current deviation value 10 obtained by calculating the deviation is multiplied by the current calculation value 4 at the preceding stage obtained by multiplying the current gain (KIP1) 3 at the preceding stage by the upper limit determination circuit 5 to determine whether or not it exceeds the preset upper limit. Limiter 6 if the upper limit is exceeded
The current output value 9 at this time is the product of the current gain (KIP3) 8 in the subsequent stage, which is branched to the upper limit and is set to an appropriate value of 1 or less. When the calculated current value 4 in the front stage does not exceed the upper limit value, the current gain (K
The current output value 9 at this time is a value obtained by branching to the IP2) 7 and multiplying the current gain (KIP3) 8 in the subsequent stage set to an appropriate value.

[0010]

As is apparent from the above description, the method of preventing oscillation of the servo motor according to the present invention changes the current gain appropriately according to the situation, and the servo motor of the servo motor when it is started up from the stop to the maximum speed. Oscillation is prevented and smooth control is performed.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a current control circuit of a servo driver including an oscillation prevention method according to the present invention.

FIG. 2 is an overall configuration diagram of a conventional servo system

FIG. 3 is a circuit diagram of a conventional current control circuit.

[Explanation of symbols]

3 Current gain of the previous stage 5 Upper limit value determination circuit (circuit that determines whether the upper limit value is exceeded) 6 Limiter 7 Current gain of the latter stage (Current gain of the latter stage that does not limit the gain value) 8 Current gain of the latter stage ( (Post-stage current gain applied to the limiter output)

Claims (1)

[Claims] 1. A servo driver current control circuit is capable of discriminating whether or not a multiplication value of a current gain of a preceding stage and a current deviation amount and a current gain of a preceding stage exceeds an upper limit value. A circuit for selecting a subsequent processing route depending on whether or not it is present, and the gain applied to the limiter and the limiter output is limited to 1 or less for the processing route when the multiplication value exceeds the limit value. The current gain of the limited second stage is given, and the current route of the latter stage which does not limit the gain value is given to the processing route when the above multiplication value does not exceed the limit value, and the servo motor is started from the stop to the maximum speed. A method to prevent the servo motor from oscillating when it does.