Torque dynamics in sensorless PMSM drives

In automotive drivetrains used in hybrid electric vehicles, the transmission connecting the electric machine(s) and the combustion engine often introduce non linear phenomena such as gear play and backlash. These non-ideal effects can result in drivetrain oscillations which, in turn, can be mitigated by a controller manipulating the torque reference of the electric machine. If a permanent-magnet synchronous machine (PMSM) is operated without using a position sensor (sensorless), the resulting torque dynamics (from the torque reference to the shaft torque) is different compared to the situation when the rotor position is known. Hence, it is desirable to know the torque dynamics for PMSMs operating sensorless when the drivetrain torque oscillation controller is tuned. This paper presents a number of models, evaluated using simulations, describing the torque dynamics of PMSM drives with and without the use of a position sensor.