A Method of Resolver-to-Digital Conversion Based on Square Wave Excitation

A novel method of resolver-to-digital conversion based on square wave excitation is proposed in this paper. First, the outputs of the resolver under square wave excitation are theoretically analyzed in comparison with those under cosine excitation. Analysis results indicate that the former outputs are proportional to the desired demodulated waves, whereas the latter are coupled with the excitation signal. On this basis, demodulation can be achieved by multiplying the square wave excitation with the outputs, respectively, yielding the sine and cosine demodulated waves. Smooth and independent of the excitation, these demodulated waves can be sampled at any time with the sampling frequency no longer restricted to the excitation frequency, thus solving the problems of fixed-point and fixed-frequency sampling under the traditional cosine excitation. Finally, a simple design of the peripheral circuits is presented to realize the proposed method, and the effectiveness and feasibility of the method is verified by experimental results.