DDV servocontrol system based on variable-structure PID control

A triplex-redundancy direct-drive-valve (DDV) servocontrol system is designed, in which a brushless DC motor (BLDCM) drives rotational valve core directly. Mathematical models of the system based on duplex closed-loop control structure are built up in this paper. And a novel variable-structure PID control strategy is proposed and analyzed. The experiment results show that the proposed control scheme is easy to real-time control, and reduces the effects of non-linear saturation and uncertain hydraulic resistance effectively. It improves static and dynamic operation performance, and ensures the redundancy characteristics after first or second electrical failure. The system satisfies the DDV actuator of airplane.