This paper presents the activity made by the authors within the National Research Program "PRIN 2000", partially supported by the Italian Ministry of Instruction, University and Research (MIUR). The research has concerned the development of a sensorless controller for interior permanent magnet (IPM) synchronous motors to be used in city-scooter application. The project result has been the design of a sensorless scheme suitable for general applications where low speed and standstill such as high speed operations are required. The final solution consists in an hybrid technique employing an adaptive observer for medium/high speed operation and a signal injection based technique for low speed and standstill operation. The observer detects the rotor magnet flux components in the two-phase stationary reference frame using the motor electrical equations. The motor speed is identified by a model reference adaptive scheme using an additional equation obtained by a Lyapunov function. The analytical development of the observer is fully explained. The convergence of the estimates at low speeds and standstill is achieved through the assistance of a high frequency signal injection technique. Realistic simulations accounting for the inaccuracy of an actual digital signal processor (DSP) implementation and the prototypal implementation on a commercial hardware for city-scooter application are presented and discussed.
