Abstract:In the position detection of electromagnetic shock absorber (ESA), the commonly used displacement sensors often require large installation space and clean usage environment. To reduce the complexity of the detection method and the limitation of the detection environment, three linear Hall sensors are used in the actuator end of the ESA and are arranged at a spacing of 120° from each other at an electrical angle. They are used for detecting the information of the magnetic density change of the stator′s permanent magnets and converting it into the position information of the ESA. The research of the position detection method is implemented under the consideration of the installation error of Hall sensors, the sensitivity error between multiple sensors and the harmonic component generated by the magnetic field distortion. First, the arrangement position of Hall sensors is determined by analyzing the magnetic density variation, magnetic density peak, and harmonic content in the end region by the finite element method. Then, a mathematical model of the output Hall signal considering the Hall sensor error and harmonic interference is formulated. Based on the characteristics of this model, a dual phase-locked loop (DPLL) combined with a band-pass frequency synchronization extraction filter ( DPLL-BPFSEF) position-solving method is proposed. DPLL is used to suppress the influence of high-frequency harmonics on the signal, and BPFSEF is utilized to suppress the influence of low-frequency harmonics appearing in the signal to compensate for the unstable suppression ability of DPLL on low-frequency signals during the solving process. Finally, the effectiveness of the position detection method under uniform speed and sinusoidal motion conditions is analyzed through experiments. The results show that both DPLL-BPFSEF and DPLL can accurately solve Hall signals and realize the detection of the speed and position of the ESA actuator at the same time. The error rate of velocity is 5. 1% when detecting the sinusoidal motion of the actuator by DPLL-BPFSEF, and the position accuracy of DPLL-BPFSEF is 42. 8% and 37% higher than those of DPLL for both uniform velocity and sinusoidal motion.