Design Of Fuzzy PID Controller Based On FPGA

With the rapid development of control theory today, as a result of it is simple and easy to implement can be debug of the field, so PID control method is widely applied in industrial control. In the practical operation, most of control processes have characteristics of non-linear, time-varying and uncertain. Conventional PID control can not meet the control requirements. Fuzzy control simulation of the way of thinking of human brain's, can deal with non-precision, non-linear information of the objective world, and it has a strong anti-interference ability. Combining with fuzzy control technology, PID control technology can provide a new solution for modern automation industrial. For FPGA chip, considering its high integration degree, its short development period and its strong repeatability, the fuzzy PID controller based on FPGA has a good practical value and an optimistic future.This thesis mainly studies the design of fuzzy PID controller based on FPGA. Two kinds of design methods are discussed:The first one is the checking table method. This method is to calculate off-line fuzzy control table, then realize it through programming on the FPGA.The second one is the on-line inference method. The whole fuzzy inference process is realized by programming directly on the QuartusⅡsoftware platform. According to the basic structure of fuzzy PID controller, it is divided into three major part:fuzzification part, fuzzy inference part and defuzzification part. In fuzzification part, the relevant membership degree and language variable of the input variable are obtained through multi-branch choice and judgment structure. In fuzzy inference part, the exterior adopts circulation structure and the interior adopts multi-branch judgment and choice structure, which is used in the calculation of membership degree of the output language variable. At the same time, Max-Min inference operation is carried to work out output control variable. In defuzzification part, two defuzzification methods are designed, users can choose each one according to need.This design adopts method of up to down, uses VHDL hardware language to design, and makes use of the Quartus II software platform to carry on simulation and verification. The result of simulation accords with that of fuzzy control table.And then simulink is used to establish a closed-loop control system, and conventional PID control result and fuzzy PID control result are compared which proves its effectiveness.