Load torque and moment of inertia observability analysis for alternating current drive sensorless control

Knowledge of the exact characteristics of a motor is necessary for a high-performance electrical drive control. It is useful to obtain not only the states of electrical and mechanical variables, but also other quantities. Two of the unknown parameters are the moment of inertia and the load torque. This paper addresses theoretical aspects of conditions, on which these quantities are simultaneously observable. Both asynchronous and synchronous drives are considered. The conditions are verified by a simulation and by real-motor data. Obtained results prove the possibility of their sensorless estimation. Some difficulties of the state estimation when controllers are saturated are shown.