Design Of Resolver Decoding System Based On CORDIC Algorithm

The resolver who has many advantages of high precision, small size, simplestructure and strong anti-jamming capability, has been widely used in industrialmanufacturing and military fields.But its output is AC analog signal and is verycomplex to deal with. In order to convert the analog signal to a digital angle value,you need to decode the analog signal.Decoding usually have two options, a resolverdedicated decoder chip, and another is to use the MCU or FPGA, AD converter chipsand other separation devices to build a decoding system.While the former wanted toachieve the ideal precision usually require a higher cost, limited its application inother fields.The purpose of this paper is to build a resolver decoding system using FPGA.This system not only can replace a dedicated decoder chip, and can be based on actualproject need to highlight certain aspects of the system characteristics.In this paper, on the basis of the resolver mathematical model and the CORDICalgorithm principle, we determine to use CORDIC algorithm to achieve arc tangentfunction. Because the traditional CORDIC algorithm covers a limited angular range,the design of hardware algorithms has to contain the pre-and post-processing module,to enable them to meet the range of (0,360°) decoding. Compared to the traditionaliteration of the loop, the CORDIC core uses the pipeline structure. We use VHDLhardware description language to write the entire arctangent solver module. Thealgorithm we design has speed, accuracy, flexible and adjustable, hardware andsimple, which is the focus of this article. In this system, FPGA generates theexcitation signal, controls AD sampling module to sample the resolver’s output signal,sends the sampled digital signal to the FPGA angle solver module and sends the anglevalues calculated to the DSP scheduling module via the serial communication module.Then we design the hardware and software of the system. Finally, the errors of thesystem are analyzed theoretically and several compensation methods are introduced.The experimental results show that the decoding system can meet therequirements of the general servo control.