Research Of Fully Digital Brushless Dc Motor Control System Based On FPGA

Brushless DC motor (BLDCM), in which electrical commutator is used instead of mechanical, has not only the same governing performance as traditional DC motor, but also the good characteristics of AC Motor. Besides, the machines have high power density and small volume. Brushless DC motors have been widely used in many areas, especially in high performance servo and drive areas, such as the spacecraft pose control and robot. In these scenarios, not only a small volume but also the parallel controls of multiple motors are required. The motor controllers based on the digital processor like MCU or DSP are usually implemented in software. As a result, the problems of slow response speed and low reliability are existed, and the controller performances are difficult to meet demands. The FPGA (Field Programmable Gate Array) may realize the complex control function on a piece of system chip. The volume of control system has been cut down greatly. This kind of control system presents a good application prospect in the industrial and civil territory even in the servo domain.Under these backgrounds, the operation principles of the BLDCM are analyzed and also the mathematical model is setted up. On this basis, the BLDCM control algorithm with feed-forward, current and speed double-closed loops is designed. Moreover, the algorithm of integral saturation restrain PI is used.Based on the performance comparisons of various controllers, this paper proposes a fully digital hardware designed scheme of BLDCM speed servo controller, which is verified and implemented on one-chip field programmable gate arrays Cyclone III FPGA made in ALTERA. Also the methods to realize the speed adjusting of BLDCM with this controller have been validated. By using luxuriant logic cells of FPGA and combined with the characteristics of signal detection and motor control, the hardware logical circuits of all motor control modules including PI regulator, filter, speed measurement, feed forward control, PWM generator and BLDCM switching are constructed in HDL. The control system has the advantages of quick dynamic response, small overshoot, little steady-state error, high reliability and flexibility. It realizes total digital control and has preferable application value in high performance speed or position servo system. Experimental results show that the system control period is within 40μs and the controller possesses good dynamic and static performances.The hardware language VHDL (VHSIC Hardware Description Language) has been used to program some special circuit in FPGA. This paper prepared some work for the system on chip, also laid the foundation for single-chip high- performance multi-motors control system.