Quadrature Demodulation Method for Resolver Signal Processing Under Different Sampling Rate

Abstract

Resolvers are widely used as position sensors to obtain angle information. The resolver requires the excitation signal and its amplitude is modulated by the rotor position. The envelope of the modulated signal can be detected precisely only when the samplings are synchronized with the excitation signal. A large error can occur if the synchronization fails. In this paper, the resolver signals are sampled in synchronization with the pulsewidth modulation (PWM) carrier, not the excitation signal. When the resolver excitation signal frequency and the PWM carrier frequency are different, the envelope cannot be detected, so additional signal processing is required to obtain the angle information. For signal processing, multiple auxiliary signals are synthesized based on the sampled signals and quadrature demodulation is performed. A detailed error analysis according to the PWM frequency and motor speed is also performed. The effectiveness is demonstrated through simulation and experimental evidence.

Keywords

• Phase-locked loop (PLL)
• resolver-to-digital conversion (RDC)
• demodulation
• resolver
• envelope detection