Solution To The Servo Motor Noise in CNC Machining Center

Noise is usually defined as useless components in the signal, and noise is everywhere. In CNC machine tools and their surrounding environment, noise disturbance is inevitable. Noise disturbance includes drift caused by temperature change and various electrical disturbance signals. All kinds of noise disturbance signals will inevitably reduce the tracking accuracy of the servo system. In the control cabinet of CNC machine tool, grounding technology, shielding technology and isolation technology are generally used to eliminate the influence of noise disturbance signal.

Designing a disturbance observer for various disturbance signals and compensating it in the servo control system is a way to reduce the influence of disturbance and improve the robustness of the system. Some experts analyzed the influence of noise disturbance on the tracking accuracy of servo system, and proposed a control method for the observation and compensation of noise disturbance signal: by detecting the voltage added to the servo driver and the rotation angular displacement of servo motor to observe the noise disturbance, and the disturbance compensation is superimposed on the output of position controller to realize compensation. 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 the noise disturbance is observed and compensated, the position command input signal is set as 2Sin (0.4 π T); The noise disturbance is sawtooth signal with amplitude of 0.5 and period of 2S. When the noise disturbance signal is not considered, the system tracking error is within ± 0.006mm; When the noise disturbance signal is added without disturbance observation and compensation, the system tracking error is within ± 0.02mm; When the noise disturbance observation and compensation method is adopted, the tracking error of the system is within ± 0.007mm. The comparison shows that the noise disturbance observation and compensation method can effectively improve the anti-interference ability of servo feed system