Disturbance Rejection Control for Underwater Propulsion Motor at Low Speed Based on Fusion Observation of Resolver and High-Frequency Injection

The low-speed control performance constitutes a fundamental prerequisite for the propulsion system of unmanned undersea vehicle to execute critical missions such as deep-sea exploration and military reconnaissance effectively. In response to the need for enhanced control capabilities during low-speed operations, limitations in permanent magnet synchronous motor drive systems employing both schemes with and without position sensor were systematically examined. Resolvers tend to introduce position detection errors under harsh environmental conditions. However, among dominant sensorless solutions, due to inherent observation dead zones near zero speed in back-electromotive-force observers, high-frequency signal injection methods improve low-speed observation performance, but their accuracy remains susceptible to motor parameter variations. Moreover, the accuracy of all sensorless control schemes exhibits high dependence on current sampling precision, making such schemes vulnerable to severe engineering challenges in complex disturbance-intensive operating conditions. To resolve these issues, a hybrid observation-based low-speed disturbance rejection control strategy integrating resolver with high-frequency square wave injection was proposed. By applying hardware redundancy and information fusion techniques, the deep integration was achieved between the absolute position reference provided by resolvers and dynamic observations generated through high-frequency square wave injection. An advantage-complementary observation architecture was established to significantly enhance system robustness in difficult scenarios including low-speed operations, variable loading conditions, and signal interference contexts. Simulation results verify the capability of the proposed method to effectively suppress detection error disturbance from position sensors and current sensors, enabling stable and precise rotor position observation and delivering a high-reliability control solution for underwater equipment power systems.