Sensorless Control of Permanent magnet in-wheel motor for EVs Using Global Fast Terminal Sliding Mode Observer

This article aims to provide a high-precision sensorless controller for permanent magnet in-wheel motors (PMIWMs) used in electric vehicles (EVs) when an unexpected failure of the position sensor occurs. To address this, we propose a position sensorless control method that combines a global fast terminal sliding mode observer (GFTSMO) with a phase-locked loop (PLL) estimation scheme. First, the GFTSMO is introduced to reduce the significant chattering that typically occurs in traditional sliding mode observers (SMO). This control scheme can help the state variable converge to an equilibrium state from any initial condition and minimize chattering. Second, we implement a PLL estimation scheme to replace the conventional arc-tangent estimation method. This method avoids the triggering of high-frequency oscillations, thereby improving the estimation precision and robustness of the control system. In addition, we discuss the stability of the proposed GFTSMO using the Lyapunov function. Simulation and tests on a motor platform demonstrate that the proposed position sensorless algorithm can track speed rapidly and accurately without overshooting. The proposed sensorless control can ensure the control stability of PMIWMs and can be applied in other occasions where installing motor sensors is challenging.