A Sensorless-Based Control Scheme to Enhance the Accuracy of Position Encoders Used in Permanent Magnet Synchronous Motors for Automotive Applications

In this paper, the problem of designing a position and speed observer for Permanent Magnet Synchronous Motors (PMSMs) used in automotive applications is addressed adopting a three-step approach. First, we propose to estimate at rest the initial rotor angular position. This is done by injecting high-frequency currents within the stator windings. Second, for low speed, we propose to use an incremental sensor with coarse accuracy, similar to those attached to the crankshaft of the internal combustion engine. Third, for speed range above a given threshold, we design a nonlinear observer that relies on stator currents and voltages measurements and generates exactly the position estimate. These different estimations are then used in the field oriented torque control scheme to respond to a torque request in a vehicle application. Several experimental results are provided and the control scheme is then implemented on a vehicle benchmark application which consists in a shuttle system for inner-city transportation. The theory is verified via experimental results on an HIL testbed.