Fractional AC Servo System Controller

With the rapid development of science and technology the AC servo systemwas widely used in the field of industrial production, and the requirement ofservo system is increasingly demanding. Traditional PID controller has theadvantages which the structure is simple and easily implemented, but therobustness of the system is not good enough when external disturbance andchange in the system parameter. Recently, the fractional order operator isdigitital realized benefited from the development of computer technology, andthe issues about the application of fractional order controller receivedwidespread attention. In this paper, the applications of fractional order controllerin AC servo system are studied in order to improve the control performance ofAC servo system.Firstly, a method of designing and turning fractional order PIλDμcontrollerwas proposed for AC servo system. The proportional, integral and derivativefunction coefficient of the PIλDμcontroller were turned by using integer orderparameter turning method, and the integral and the differential order wereaccording to the phase margin specification by a graphical method, which couldovercome the diffcult of solving nonlinear equations The simulation resultsshow that, the proposed method was simple and effective, and has better controleffect than the traditional PID controller.Secondly, a method of designing and turning fractional order internalmodel controller is proposed for AC servo system. Based on internal modelcontrol principle, a fractional order internal model controller was deduced byusing a fractional order filter to replace the integer order one. The proposedcontroller contained only two adjustable parameters, and the defects of thefractional PIλDμcontroller tuning method were effectively overcome. Moreover,the dominant pole was selected according to the time domain performanceindicators of the system, and an analytical tuning approach of the controller wasgiven. So the blindness of selecting the controller parameter was averted. Thesimulation results show that the proposed method not only could overcome the problem of need turning more parameters of the fractional order controller, butalso could improve system control performance.Thirdly, a method of designing single neuron adaptive fractional order PDμcontroller was proposed for AC servo system. The three single neurons wereused to complete the online adaptive turning the three parameters of thefractional order PDμcontroller, which were adjusted according to the deviationchanges in real time. The simulation results show that, the proposed methodeffectively improving the control performance of the AC servo system.Finally, the advantages and disadvantages of the three methods proposed inthis paper were summarized, and the direction of further work is pointed out.