DSP-based resolver-to-digital conversion system designed in time domain

Resolver is an absolute angle measurement and is mounted on the motor shaft to acquire the motor´s absolute angular position. This study presents an equivalent circuit of the resolver neglected rotational back electromotive force. The transfer function of the resolver is derived from the equivalent circuit. The frequency response of the resolver is measured by a dynamic signal analyser to obtain the adequate frequency of resolver´s reference signal. Furthermore, a digital signal processor (DSP)-based resolver-to-digital conversion system is designed in time domain. A pulse signal generated by the DSP is utilised as a reference signal coupled into the resolver´s rotor winding and provides primary excitation. The sine and cosine modulated output signals are sampled by the analogue-to-digital converter of the DSP within 1 μs. The sampled frequency of outputs signals are the same frequency as the pulse signal. The angular position is derived by the inverse tangent of the quotient of the demodulated sine and cosine samples. Test results are presented to validate the performances of the proposed scheme.