JP2001251880A - Servo control unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem where unwanted frequency components are not necessarily one, but probably plural so that the conventional art has disadvantage in that only one notch filter can be installed and when plural notch filters are arranged in a control loop, the number of delay elements in a control system increased and a speed loop gain is decreased. SOLUTION: In a servo system, in which a machine is driven with a servo motor, a bi biquadratic function type filter 6 is added to an input stage of a torque command or an output stage of a motor speed, in a control system in which mechanical vibration is generated. The zero point of the filter 6 is made to coincide with the resonance point of a mechanical system. The pole of the filter 6 is made to coincide with the vicinity which contains the antiresonance point of the mechanical system, and the coefficient of viscosity of the filter 6 is adjusted and set.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servo system controller for removing mechanical resonance and higher-order vibration components generated by a servo motor and a machine.

[0002]

2. Description of the Related Art As a technique for removing a vibration generated in a servo system, as shown in JP-A-6-78575, when a notch filter is inserted to remove unnecessary frequency components,
There is a feature of an automatic parameter adjustment method for solving the problem of not knowing how to set a notch filter.

[0003]

The number of unnecessary frequency components is not limited to a single one, but may be a plurality. In Japanese Patent Application Laid-Open No. 6-78575, there is a disadvantage that only one notch filter can be set. However, when a plurality of notch filters are put in a control loop, delay elements of a control system increase, and conversely, the speed loop gain cannot be reduced. It becomes a situation that can not be obtained. It is also conceivable to remove a vibration component using one notch filter and a torque filter. However, similarly, not only the speed loop gain does not increase but also vibration may be induced in the control loop. . An object of the present invention is to provide a servo control device capable of removing a vibration component and a higher-order vibration component that most affect a servo system by using one biquadratic function filter.

[0004]

In order to achieve the above object, the present invention provides a servo system for driving a machine that generates vibration by a servomotor, wherein a zero point is set to a resonance point of a mechanical system and a pole is set. A biquadratic function type filter whose viscosity coefficient is adjusted and set in the vicinity including the anti-resonance point of the machine is provided at the input stage of the torque command or the output stage of the motor speed of the servo system. It is characterized by.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to a block diagram. 1 and 2 are block diagrams showing an embodiment of the present invention. The block diagram is a speed control system having the mechanical resonance system 1. The speed control system includes an integrator 2, a speed gain 3, a torque filter 4, a converter 5 for converting a motor angle into speed data, a biquadratic function filter 6, a speed command 8, and a motor speed 9. . A system having a mechanical resonance system has an anti-resonance point 10 and a resonance point 11 as shown in FIG. In addition, machines typically have one or more resonant systems. The biquadratic filter is expressed by equation (1), that is,

[0006]

(Equation 1)

[0007] (In the equation (1), the zero point ωp, the pole ωz, and Qp in the biquadratic filter correspond to ζp (viscosity coefficient) of the numerator, and Qz corresponds to ζz (viscosity coefficient) of the denominator.) In order to remove the noise, a commonly used filter is given by equation (2), that is,

[0008]

(Equation 2)

## EQU1 ## Actually, the speed control system is digitally controlled. Therefore, when the expression (1) is bilinearly transformed,
Equations (3) and (4), that is,

[0010]

(Equation 3)

## EQU1 ## In the parameter setting of the poles and zeros of the biquadratic filter 6, after examining the frequency characteristics of the machine (FIG. 3), 10 frequencies and poles of the biquadratic filter are determined for each pole and zero. When ωz is set in accordance with the frequency 11 and the zero point ωp of the biquadratic function filter, a speed control system having a gentle curve in the gain characteristic of FIG. 4 can be obtained. The feature of this filter is that the same effect can be obtained even if the notch filter is not used in multiple stages. When the biquad filter is set as described above, the frequency characteristics are as shown in FIG. As can be seen from this figure, the gain characteristic is 0 dB at low frequencies, and decreases in the high frequency region. By utilizing the fact that the gain characteristic decreases in the high frequency region, the peak of the resonance point of higher-order mechanical vibration decreases. That is, by using the filtering characteristics, high-order vibration is prevented from being generated. A simulation (FIG. 2) was performed in consideration of mechanical resonance and higher-order vibration. The command was set to a trapezoidal waveform, and a comparison was made between when the notch filter was used and when the biquadratic function type filter was used. As a result, in the comparison in FIGS. In contrast, the biquadratic function type filter does not generate vibration at a constant speed. It can be seen that the high-order vibration component could not be suppressed by the notch filter.

[0012]

According to the servo control device of the present invention,
By including a quadratic filter, the influence of higher-order vibration components can be cut without any additional filters.
Further, since the notch characteristic of the anti-resonance, which is a feature of the two-mass vibration system, is moderated, the loop gain can be increased as compared with the notch filter.

[Brief description of the drawings]

FIG. 1 Speed control system

FIG. 2 is a block diagram of a simulation experiment.

FIG. 3 is a frequency response characteristic of a speed control system.

FIG. 4 is a frequency characteristic when a biquadratic function type filter is included in the speed control system.

FIG. 5 shows the frequency response of a biquad filter.

FIG. 6: Response with notch filter

FIG. 7: Response using biquadratic filter

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mechanical vibration system 2 Integrator 3 Speed gain 4 Torque filter 5 Converter which converts rotation angle into rotation speed 6 Biquadratic function filter 7 Higher-order vibration component 8 Speed command 9 Motor rotation speed 10 Zero point of mechanical vibration system 11 Mechanical vibration system poles

Claims (1)

[Claims] In a servo system for driving a machine that generates vibration by a servomotor, a zero point is adjusted to a resonance point of a mechanical system, and a pole is adjusted to a vicinity including an anti-resonance point of the machine, so that a viscosity coefficient is increased. A servo controller, wherein a biquadratic function type filter to be adjusted and set is provided in an input stage of a torque command or an output stage of a motor speed of the servo system.