FPGA-based all-digital resolver-digital conversion algorithm

An FPGA based all-digital close-loop angle tracking algorithm is proposed to achieve an all-digital resolver-digital converter (RDC) with low cost and high integration. ΔΣ modulation technology is introduced into sine reference signal generator, to simplify hardware filtering circuit and minimize the damping and phase lag. Optimized control of sampling and filter processing are applied to guarantee favorable acquisition of sine and cosine feedback signals under harsh EMI environment. A PLL-based angle tracking observer is designed, which uses CORDIC arithmetic for phase detection and PI regulator for rapid close-loop tracking. ΔΣ modulator, time sequence controller, CORDIC phase detector, and PI regulator IP cores are written in Verilog HDL and have been tested on Xilinx XC3S400 FPGA. Experimental results verify that the all-digital RDC can make digital conversion with high precision, high dynamic and static characteristics, relying on rapid parallel algorithm of FPGA without much cost increase.