Sensor Fusion of Self-Sensed Measurements for Position Control of a Constant Air-Gap Solenoid

This article presents a novel constant air-gap solenoid (CAS) actuator design that can perform accurate and wide-bandwidth closed-loop position control with two fused self-sensed plunger measurements. The recently patented CAS actuator is experimentally validated to be the first electromagnetic actuator with the ability to simultaneously produce two plunger position measurements with complementary bandwidth characteristics. First, a variable reluctance differential solenoid transducer (VRDST) is converted into a stacked CAS actuator through minor geometry modifications. Next, two complementary self-sensing methods that are based on inductance and back electromotive force (BEMF) are selected. Then, a complementary filter design is proposed to fuse the inductance- and BEMF-based self-sensing methods. Afterward, the design and fabrication of the prototype CAS actuator and the experimental setup are discussed. The experimental setup is then used to characterize the prototype CAS actuator and observe the performance of the individual self-sensing methods. Finally, the fused measurement is used for feedback in closed-loop position control. The closed-loop position control experiments show that the self-sensed feedback performs comparably with a dedicated high-end laser vibrometer. Furthermore, the results show that the sensor fusion output performs better than the individual self-sensing methods.