A Low-Energy Variable Air Gap-Based Reluctance-Actuated Motion System

This article presents a design and characterization of a motion stage driven by a low-energy reluctance actuator (RA). The low-energy concept reflects the ability of the RA to generate a high force with low current values due to the quadratic relation of the force with the input current. First, the critical voltage is determined for stable operation; then, the open-loop response is obtained under different applied voltages. The experimental results show that the motion stage exhibits nonlinear force characteristics. Second, a feedforward controller is proposed to linearize the dynamic behavior of the RA. The experimental results show the ability of the proposed feedforward controller to achieve linear input-output characteristics between the desired force and the measured force. Next, a state feedback controller based on a robust backstepping approach is designed to achieve the desired displacement, considering the force errors due to the bounded open-loop compensation, which can be reduced by tuning the controller gains. The experimental results show the ability to achieve a tracking to a step reference signal with an error less than 2% and to a sinusoidal reference signal with a tracking error less than 15% of motion range for a moving mass about of 1.6 kg.