Design of an Angle Tracking Observer for Resolver Sensors using a Type-II System and Root Locus Technique

Resolver is an angular position sensor widely used in motor drives when robustness is critical. This sensor generates two high-frequency amplitude-modulated signals which give information about the angular position. A resolver-to-digital converter (RDC) is an equipment used to get the angular position from the resolver outputs. Many RDCs are based on angle tracking observer (ATO) which reduce the angle estimation error. The transient behavior of the angle estimation depends on the ATO parameters. This paper proposes the tuning of an ATO with two embedded integrators (a type-II system) through root-locus technique. It was used a lead compensator to improve the transient response of the ATO, while the embedded integrators make the steady-state error tend to zero for constant position and speed operation. Simulation results show that the ATO was properly tuned through root locus technique, allowing a good angle estimation.