High-frequency precision motion control of fast axis servo device

Fast Axis Servo (FAS) device, also known as Long Stroke Fast Tool Servo (LFTS) device, is a high dynamic response servo module with a frequency response of several tens of Hertz in a millimeter displacement stroke, which is mainly used for high-efficiency machining of Non-Rotationally Symmetric (NRS) surfaces. The development of optical design takes challenge to the manufacturing technology. Based on the principle of free-form surface turning, the accuracy of free-form surface processed by the FAS system is directly affected by its motion accuracy. With the increase of motion frequency and stroke, the error caused by amplitude attenuation and phase lag will be greatly increased. In order to maintain the accuracy of FAS system at high-frequency motion, in this paper, a FAS prototype is designed and manufactured. The power PMAC controller is used to form a control system. The model of the system is identified through open-loop sweep frequency test. And the feed forward and PID feedback servo control algorithm is used. finally, the tracking error of the prototype under 20 Hz frequency and 5 mm stroke sinusoidal motion is measured to be ±1 um, which has achieved good control effect.