A Full-Order State Sliding Mode Observer for Sensorless Control of UAV PMSM with Online Temperature Identification Strategy

In the sensorless control system of Unmanned Aerial Vehicle (UAV) permanent magnet synchronous motor (PMSM), online temperature monitoring is critical for ensuring operational safety. During PMSM operation, excessively high temperatures may lead to permanent magnet demagnetization and stator winding insulation damage, which seriously affects the reliability and service life of the UAV. In order to address this issue, this paper proposes a full-order state sliding mode observer method with integrated online temperature identification. First, a full-order state sliding mode observer is constructed in the estimated γ-δ reference frame. This observer takes stator currents and extended back electromotive force (EEMF) as state variables, which can improve the system robustness and dynamic observation performance. Then, an affine projection algorithm (APA) is designed in the γ-δ reference frame. By selecting regularization parameters via a piecewise method, stator resistance is identified in real time to indirectly acquire stator temperature information. This approach ensures both convergence speed and steady-state accuracy while avoiding the use of additional temperature sensors. The experimental results demonstrate that the proposed full-order state sliding mode observer not only accurately estimates rotor position and speed but also achieves real-time temperature monitoring of UAV across the entire speed range.