Fractional order control and its application of PI/sup /spl alpha//D controller for robust two-inertia speed control

This paper deals with the speed control of two-inertia system by fractional order PI/sup /spl alpha//D controller which means the order of I controller will not only be integer but also can be any real number. The significance of fractional order control is that it is a generalization and "interpolation" of the classical integer order control theory, which can achieve more adequate modeling and clear-cut design of robust control system. However, most of fractional order control researches were originated and concentrated on the control of chemical processes, while in motion control the research is still in a primitive stage. In this paper, a frequency-band fractional order PI/sup /spl alpha//D controller is proposed to speed control of the two-inertia system, which is a basic control problem in motion control. A frequency-band broken-Line approximation method is introduced to realize the designed fractional order PI/sup /spl alpha//D controller that has a satisfactory accuracy in frequency domain. The better robustness performances of the PI/sup /spl alpha//D control system against saturation nonlinearity and load inertia variation are shown by the comparison of fractional order PID control\´s experimental time responses with integer order PID control\´s. The superior robustness and clear-cut control design highlight the promising aspects of applying fractional order control in motion control.