Vibration suppression method for servo motor and load multistage drive system

Abstract

A vibration suppression method for a servo motor and a load multistage drive system is provided. For a number N of fixed vibration frequencies and one vibration frequency varying with a load position existing in a multistage drive mechanism, a number of N+1 vibration suppression filters are adopted, and each filter is configured to eliminate a corresponding vibration frequency. Fixed vibration frequencies and a vibration frequency varying with a load position in a multistage drive system are measured by using an offline method, and the varied vibration frequencies are made into a two-dimensional table related to the load positions. The fixed vibration frequencies are eliminated by using fixed-frequency parameter vibration suppression filters; and the varied vibration frequencies are eliminated by using a variable-frequency parameter vibration suppression filter, and the vibration frequencies are obtained in real time according to the load positions and the two-dimensional table.

Claims

1. A vibration suppression method for a servo motor and a load multistage drive system, comprising following steps: step 1: measuring vibration frequencies, including measuring vibration frequencies of stages of drive mechanisms offline, comprising a number N of fixed vibration frequencies and one variable vibration frequency; and for measurement of the variable vibration frequency, successively stopping a load at different positions, recording load positions and measuring vibration frequencies, and drawing a two-dimensional table according to a relationship between the vibration frequencies and the load positions; step 2: setting frequency parameters of fixed-parameter vibration suppression filters, including selecting a number N of fixed-parameter vibration suppression filters, wherein frequency parameters of which respectively correspond to the number N of fixed vibration frequencies measured in the step 1; and step 3_ setting a frequency parameter of a variable-parameter vibration suppression filter, including selecting a variable-parameter vibration suppression filter; during movement, calculating, according to the load positions and the two-dimensional table drawn in the step 1, a vibration frequency of the position by using a linear interpolation method; and setting the vibration frequency to a frequency parameter of the variable-parameter vibration suppression filter.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a lead screw drive system;

(2) FIG. 2 shows a belt pulley drive system;

(3) FIG. 3 is a schematic diagram of measuring a vibration frequency of a belt pulley drive system;

(4) FIG. 4 shows an amplitude-frequency curve of a belt pulley drive system; and

(5) FIG. 5 shows a relationship between a vibration frequency and a load position.

DESCRIPTION OF THE EMBODIMENTS

Embodiment

(6) FIG. 2 shows a typical belt pulley drive system, and the system has a fixed vibration frequency and a variable vibration frequency. There is a rigid coupling 4 and no vibration between a servo motor 3 and a synchronizing wheel 1. A drive mechanism formed by the synchronizing wheel 1, a synchronizing wheel 2, and a belt has a fixed vibration frequency. A drive mechanism formed by the synchronizing wheel 1, the belt 5 and a load has a variable vibration frequency related to a load position.

(7) A vibration suppression filter adopted in this embodiment is a standard notch filter, a transfer function of which is as follows.

(8) $G\left(s\right)=\frac{s^2+{}_n^2}{s^2+2{}_{n}s+{}_n^2}$

(9) Wherein, .sub.n is a center frequency of the notch filter, and is a bandwidth of the notch filter.

(10) Implementation steps are as follows.

(11) Step 1: Measuring Vibration Frequencies

(12) As shown in FIG. 3, a load is stopped at positions of L1, L2, and L3 respectively, and a servo controller is used to give a given torque 6 with relatively rich frequency components, and detect a feedback speed 7 of the motor. Fourier transform is performed on the feedback speed, and an amplitude-frequency curve thereof is drawn, as shown in FIG. 4. There is a fixed vibration frequency F0 and variable vibration frequencies F1, F2, and F3 in the figure. Vibration frequencies of more positions may be measured by repeating this step, and a relationship between the variable vibration frequencies and the positions is made into a two-dimensional table. FIG. 5 shows a relationship between the measured vibration frequencies and the positions.

(13) Step 2: Setting a Notch Filter with a Fixed Center Frequency

(14) A notch filter with a fixed center frequency is adopted. The center frequency thereof is set to the fixed vibration frequency F0.

(15) Step 3: Setting a notch filter with a variable center frequency

(16) A notch filter with a variable center frequency is adopted. During movement, a vibration frequency F of a load position L is calculated according to the position by using a linear interpolation method; and the vibration frequency is set to a center frequency of the notch filter.

(17) According to the method of the present invention, the fixed-parameter vibration suppression filter and the variable-parameter vibration suppression filter are used respectively, and do not affect each other. The vibration frequency is measured in an offline manner. The implementation is relatively simple and may obtain a more accurate vibration frequency. When measuring the vibration frequency offline, only a servo controller is used to give a given torque with relatively rich frequency components, and detect a feedback speed of the motor, and no extra measurement device is required. The variable vibration frequencies are made into a two-dimensional table, and when the system is running, vibration frequencies of different load positions are obtained by using a table look-up method and a linear interpolation method. Therefore, the method is applicable to a multistage drive system with variable vibration frequencies.

(18) A number N+1 of vibration frequencies in the multistage drive system are eliminated by using a number N+1 of vibration suppression filters. A number N of fixed-parameter vibration suppression filters eliminate a number N of fixed vibration frequencies; and one variable-parameter vibration suppression filter eliminates one variable vibration frequency. During online running, frequency parameters of the fixed-parameter vibration suppression filters are unchanged, and vibration frequencies of different load positions are calculated according to the frequency parameter of the variable-parameter vibration suppression filter by using a linear interpolation method.