Implementation of resolver excitation and resolver-to-digital conversion system based on DSP

In order to improve the integration of control moment gyro (CMG) gimbal servo system, this paper proposes a resolver excitation and resolver-to-digital conversion system based on digital signal processor (DSP). Only PWM, A/D functions of one DSP and a few peripheral circuits can afford to supply excitation to resolver, demodulate the resolver outputs and transform them into digital form. For decoding the resolver outputs, a simple inverse tangent method using a short lookup table is introduced. Sallen-Key low-pass filter, FIR band-pass filter, coarseness-precision combing with its error correction and a close-loop control method can improve angle solution and obtain velocity. Then angle and velocity are fed back to angle loop and velocity loop of the gimbal servo system to make the whole system very integrated. The main features include: easy realization, small bulk, light weight, low cost, adjustable parameters and wide uses. Experimental result shows that the angle precision can reach 17 bits.