Nonlinear output-feedback speed servo systems through active damping injection and position filtering approaches without current feedback

Abstract

This paper proposes a novel current feedback-free speed regulation method for servo systems subject to system parameter and load uncertainties. The proposed solution has two features. First, the position measurement from the rotary encoder constitutes the speed and acceleration estimates for control loops through a position filter with nonlinearly-structured design parameters and without dependence on the system parameters. Second, the proposed controller only requires nominal system parameter information, and stabilizes both the speed and acceleration loops using only position measurements by injecting active damping terms, which leads to pole-zero cancellation. A prototype servo system was built using a 500 W brushless DC-motor-based dynamo. The prototype experimentally validates the effectiveness of the proposed solution in terms of speed tracking and regulation tasks.