Position estimation for synchronous motor drives: Unified framework for design and analysis

This paper deals with the model-based speed and position estimation for synchronous reluctance motors (SyRMs) and interior permanent-magnet synchronous motors (IPMs). A unified design and analysis framework for a class of observers is developed and the links between apparently different observer structures are brought out. Adaptive state observers equipped with a speed-adaptation law are shown to equal voltage-model-based flux observers equipped with a position-tracking phase-locked loop (PLL). The error signal driving the adaptation law or the PLL is presented in a generalized form. The developed framework enables revealing potential instability issues of existing observer designs and exploiting already existing stability results. A stabilizing gain design is reviewed and design guidelines are given. The observer design is experimentally evaluated using a 6.7-kW SyRM drive.