Block diagram of a semi closed loop feed servo system with noise disturbance. The position command signal from the interpolator is set to X (s), and the angular displacement output signal of the servo motor is set to Y (s). The position control loop is set to adopt proportional control, and the transfer function is noise disturbance signal. The steady-state error generated by the disturbance signal is related to the disturbance signal itself, as well as the part before the action point of N (s) in the feed servo system.

In the feed servo system, a noise disturbance observation and compensation link is added. As shown in Figure 2, by detecting the voltage signal applied to the servo driver and the angular displacement of the servo motor, the disturbance signal N (s) is observed, and the disturbance compensation amount is added to the output of the position controller to achieve compensation.

From equations (3) to (5), the closed-loop transfer function G (s) of the system with the addition of noise disturbance and observation and compensator can be obtained, which is completely consistent with equation (2). This indicates that the observation and compensation method for noise disturbance shown in Figure 2 can compensate for the influence of disturbance and improve the system's anti-interference ability.

The position controller adopts PID control, with a proportional coefficient of 8.1, an integral coefficient of 0.002, and a differential coefficient of 0.032. When conducting observation compensation simulation research on noise disturbances, set the position command input signal as 2sin (0.4 π t); The noise disturbance is a sawtooth wave signal with an amplitude of 0.5 and a period of 2 seconds.

When noise disturbance signals are not considered, the tracking error of the servo feed system is shown in Figure 4, and the system tracking error is within the range of ± 0.006mm; When noise disturbance signals are added without disturbance observation and compensation, the tracking error is shown in Figure 5, and the system tracking error is within the range of ± 0.02mm; After using the noise disturbance observation and compensation method mentioned in the article, the tracking error is shown in Figure 6, and the system tracking error is within the range of ± 0.007mm. The comparison shows that the noise disturbance observation and compensation methods studied can effectively improve the anti-interference ability of the servo feed system.

Noise signals are everywhere, and at the interface of the servo system driver in CNC machine tools, noise disturbances include drift caused by temperature changes and various electrical disturbance signals. Various noise disturbance signals will inevitably reduce the tracking accuracy of servo systems. In the article, a method for observing and compensating noise disturbances is designed not from the perspective of hardware, but from the perspective of software compensation: by detecting the voltage applied to the servo driver and the rotational angular displacement of the servo motor, the noise disturbance is observed, and the disturbance compensation amount is added to the output of the position controller to achieve compensation. The simulation of typical sawtooth wave disturbance signals shows that the proposed observation and compensation method can effectively improve tracking accuracy and enhance the system's anti-interference ability. This method is a beneficial supplement to hardware anti-interference technology.