Fuzzy PID controller to control the pH neutralization process

Research and experiments were conducted to build a fuzzy controlled PID controller to control a pH neutralization process. Process modeling and control was performed chiefly with the SIMULINK software in MATLAB based on the McAvoy model. A gain scheduling method was studied to aid in tuning the P control of the PID. A PID controller was designed first, and then a fuzzy K_c controller was built using a Mamdani type fuzzy inference system (FIS) with the controller settings based on the results obtained from gain scheduling testing. Next, the Sugeno FIS was used to create a fuzzy τ₁ controller to complement the fuzzy P controller. The compiled fuzzy PI controller was then tested on servo and regulator problems. The servo test used a uniform random number generator to simulate set points between pH=3 to pH= 11 and the simulation was run over 100 s. The regulator test was run at ±5% of acid flow, F_a. The result of the servo test was a near perfect response with no overshoot or oscillatory responses. The response time was very quick with practically no lag time. The result of the regulator test was a response that changed in tandem with the disturbances but was limited to a narrow range of <0.01 pH units.