Resolver to Digital Converter Based on Angle Tracking Observer Method

The importances of reliability make resolver key building blocks in flight control and navigation dynamics. The conversion of resolver signals to measure position is usually accomplished using a tracking loop which causes phase lag between the actual and measured positions. This phase lag causes instability in the control loop and ultimately reduces performance of the servo system. Resolver-to-digital converters (RDCs) have a structure similar to observers so that RDCs can be modified to behave like observers. This paper proposes a novel scheme to digitize the angle information of the resolvers based on angle tracking observer (ATO) method, in which a closed loop LTI observer is combined with a quadrature encoder. Simulation results of this work shows that the proposed ATO design is stable in two cases where an LTI observer is unstable due to high speed and acceleration. The tracking accuracy of the proposed method is more accurate than a single quadratur encoder.