Research Of PID Controller Design Based On FPGA

PID control method is widely used in industrial processing control. Today when computer technology be widely used, PID control method gains farther development. The PID controller based on microprocessor solved the problem that the parameter cann't be change flexibly in traditional analog PID controller. But the general microprocessor has a limit of blind running when placed in atrocious condition. If the microprocessor which implements PID arithmetic break down for disturbance or other reasons, it will cause the output value change a lot or stop response. This circs is not allowed in productive practice, even cause severe productive accident.The PID controller based on FPGA receive the information of setting parameter at the beginning of its running, which is provided by external microprocessor.Thus, the characteristic that PID parameter can freely be adjusted is reserved. Once parameter adjusting complete, the PID controller run independently and will not affected by microprocessor. So the shortcoming that using programme to realize PID control algorithm is overcame farthest. On the other hand, due to the technology of FPGA, the controller has wider range in sampling calculate speed. In order to be propitious to bring some modified algorithm into effect, the positional PID control algorithm is selected, and the integral separation algorithm was designed as an example.Using FPGA to design PID controller is to implement PID control by digital logic circuit. Due to the large operation workload of PID control algorithm, the difficulty to realize algorithm rise, especially when deal with the problem of precision and overflow. In order to ensure the precision of operation, floating point number calculate scheme is obligatory. Technically, aim at the characteristic of each parameter, use different floating point scheme and put forward relevant means to adjust rank. Consequently, the resource in FPGA can be saved and the calculate precision also be ensured.According to top-down designing conception, the whole circuit is divided into several parts, such as calculate amount of dispersion module, proportion module, integral module, differential module, alignment rank module and time sequence control module. Every module in the circuit is carry out by RTL level language. And the function of every module in circuit is validated by emulation. At last, the designed circuit's speed performance is analysis. After encapsulation the PID controller becomes a IP core. It can be used to build lager system.