Hardware implementation of a sensorless control algorithm for permanent magnet synchronous motors

Abstract

The position-sensorless control of AC motor drives has been an important research area during the last decade. Significant results have been obtained in laboratory experiments. However, the intensive computations required, and the complexity of the algorithms involved are serious obstacles for the implementation of these results in industrial drives. The reliability and cost reduction gained by removing the position sensor usually do not justify the introduction of significantly more powerful and expensive processors. In this thesis, we take one particular sensorless control algorithm for Permanent Magnet Synchronous Motors, which presents an attractive numerical structure and good performance in the laboratory, and implement it in a low-cost custom designed board. The board design is based on a 16-bit fixed-point Digital Signal Processor (DSP) and a low-cost Field Programmable Gate Array (FPGA), which work in parallel to perform the signal acquisition, position and speed estimation, controller computation, and Pulse Width Modulation (PWM) generation. The introduction of programmable logic in the circuit provides an opportunity to relieve the processor from certain time-consuming tasks, liberating resources to perform the heaviest computations. The FPGA was programmed in VHDL, an industry standard language, which concedes the possibility of easily converting the design into an ASIC. To program the DSP, finite word-length effects of the fixed-point operations were addressed. The board was built and tested in the laboratory. Experimental results are presented, showing a satisfactory performance of this implementation over a wide range of rotor speeds and torque loads.