DC Brushless Motor Servo-control System Based On DSP

With the rapid and remarkable development of electronic technology, the application of DSP becomes more and more extensive owing to its high speed in proceeding data. In this paper, a DC brushless motor servo-control system based on DSP is designed. In this system, according to the performance requires of servo-system in rapid character, high precision, drive-stiffness and high-speed stability, we adopted a closed-loop control structure that includes three closed-loops: position closed-loop, speed closed-loop and current closed-loop.Among these control loops, the position control is in the most external. In this control loop, on account of giving consideration to both the rapidity and precision of position servo-control, we designed a fuzzy controller. This fuzzy controller can implement real-time regulation of the motor's rotational speed in light of the position error and its variable rate, therefore, the system can run in the direction of cutting down the position error with maximum speed when the system is under the condition of a higher position error. When the error is slight, the fuzzy controller also can reduce the motor's rotational speed gradually, thus the precision of the system will play a dominant role, which can create good conditions for an accurate stop when the position error diminished.For the sake of having a fine stiffness and speed stability in this system, we designed a rotational speed regulation loop inside the position loop and adopted PI regulation algorithm as a basic algorithm of speed loop controller. So it not only achieves the real-time feedback and the regulation of speed but also eliminate the static error of speed due to the integral action of PI regulator when the system is in a steady state.As we know, a servomotor usually works under three states that is starting,running and stopping. When its work states change frequently, the starting-time can influence the performance of the servo-system. In order to enhance the rapid reaction performance and regulate the current of main circuit in real time, a current loop's controller is set up inside the speed loop, it takes the PI regulator for the current loop's controller, which can make the output limited. Under the control of a current loop, the system can make advantage of the motor's ability of over-current with a maximum limit, as a result, the motor can implement constant-current staring under a maximum let-through current. Therefore, the motor's rotational speed can rise at a maximum acceleration and reach the given speed within the shortest time.In order to make the operator control the system more conveniently and know the state of the system in real time clearly, we established the interface that can be utilized for display and set-up. In this way, we can implement human-computer dialogue.