Fractional Order PD^μ Controller Tuning Based on Nonlinear Least Squares Iteration

Aiming at the randomness of the evolutionary algorithm in searching PID controller parameters, a parameter tuning method based on nonlinear least squares iteration is proposed. The parameter tuning of fractional order PD^μ controller is realized by identifying the transfer function of DC motor servo system. Similar to the iterative feedback tuning method, the desired response of the servo system is set firstly, and the three controller parameters are determined by minimizing the sum of squared errors. The compared results of the controllers tuned by nonlinear least squares method and evolutionary algorithm show that the proposed iterative controller tuning method can make the system response approximate the desired response, and also determine the unique controller parameters rapidly.