Abstract: To make the direct drive rotary feeding system with good interference rejection and tracking performance to speed command, an H∞ speed controller based on model matching robust two-degree-of-freedom (2DOF) control is designed. The H∞ controller is better in robustness against load disturbances and parameters variations. Simultaneity, the robust 2DOF structure is adopted and the model matching problem is considered to enhance asymptotical tracking performance of the servo system to speed signal and respond speed and to solve the conflict between interference rejection and fast tracking performance. Simulation results show that the proposed robust 2DOF H∞ speed controller guarantees the robustness and exact speed tracking for high-precision direct drive round table servo system.

Key words: Direct drive, H∞ speed control, NC rotary table, Ring permanent magnet torque motor, Robust two-degree-of- freedom(2DOF)