Research On Micro-Motor Servo Control Algorithm And FPGA Implementation

With the rapid development of power electronics technology, the DC servo system has been widely applied in industry, agriculture and other fields. DC motor has the advantages of wide speed range, fast response, high positioning accuracy, excellent dynamic and static characteristics, simple structure and so on, depend on which it occupies an important position in servo system. FPGA has the benefits of rich logic elements, short development cycle and it can be programmed repeatedly, the method of controlling the DC motor by a digital circuit based on FPGA has become a new trend in current research. In order to realize the array antenna fast, accurate beam scanning, it requires that each antenna unit turns quickly and accurately. Based on properties of DC motor, it can be applied to drive the antenna unit, which demands fast response and high positioning accuracy of the DC servo system. In order to meet the system volume requirement, this thesis select DC micro-motor.To achieve the fast and precise control of DC Micro-motor’s position, this thesis studies the DC Micro-motor closed-loop control system. Firstly the basic structure and working principle of DC motor are described, based on which the mathematical model of DC motor is deduced. Then the proportional-integral-derivative (PID) control algorithm is discussed and DC micro-motor control system simulation model in Simulink is established. Simulation results show that when using PID algorithm to drive DC micro-motor only, overshoot appears in the system, and short response time and small overshoot cannot be taken into account both, the rotation of the motor is beyond control as well. In order to optimize the dynamic performance of the system, this thesis studies velocity profile, feed-forward control algorithm, and proposes a new DC micro-motor servo control algorithm based on PID control, feed-forward control and velocity profile. Results show that the performance of the system is enhanced with optimized algorithm, no obvious overshoot exists, response time is shorter, and positioning accuracy is higher.In order to realize multi-axis DC micro-motor servo control based on FPGA, this thesis designs an IP core for DC micro-motor controller by using Verilog hardware description language. According to the function, the IP core can be divided into PositionControl module, PWM module, QEP module and Avalon interface module. As IP core performs many internal operations with complex timing, and by using finite state machines, timing relationship of each module is under strictly control. To reduce the number of logical unit for IP core and optimize hardware description language in each module, try to refine the program. The function and timing simulation of the IP core is verified by simulation tool, the simulation results show that the internal operation timing of IP core is correct and the calculation results are as expected.Finally, experimental test platform is set up, and SOPC system is established, Nios Ⅱ software engineering is finished too. Preliminary experimental results show that the only PID algorithm is difficult to achieve the fast and accurate control of DC micro-motor, as a large overshoot exists, the ability to adjust small angle is weak, and it cannot achieve high precision positioning. By optimizing the control algorithms and using subsection control and start-stop monitoring mode, the dynamic performance of the servo system get improved effectively, and the overshoot is reduced, the ability of small angle positioning is improved, the system response time gets shorter as well. In addition, the adaptability of IP core to different motor systems is tested.