Design Of Fractional-order PID Controller And Research On Its Time Delay

The fractional-order PID,based on fractional calculus and PID control theory,is a novel research area and of popularity for a higher freedom of design than integer-order PID.When the research of fractional-order PID control is growing rapidly,there are many problems in it such as time delay robustness of fractional-order PID controller,design of fractional-order PID controller and the application of fractional-order PID controller in remote control systems.In order to solve these problems,an adjustable fractional-order PID controller and its digital implement is proposed in this dissertation,and the main contents of this dissertation are presented as follows.Firstly,the rule of phase and gain margin is adopted for fractional-order PID controller parameters tuning,which is used to control a second-order plant with a time delay,and the parameters of fractional PID controller and their influence on the controlling performance are also considered.Simulation results show that fractional-order PID controller performes better time delay robustness than integer-order PID controller.Secondly,an approximation of arbitrary order derivatives is proposed based on variable-order derivatives and fuzzy Oustaloup approximation.A fuzzy derivative module and a adjustable-fractional-order PID controller in Simulink are also prosed.Simulation results show that fuzzy derivatives have same performance as normal ones,and so does the controller which performes better than integer ones.At last,an OPC client is implemented based on Visual C# in Microsoft.Net which contains fractional-order PID algorithm,and a remote control network is established with an OPC client and a KingView OPC server,in which the double-tank is considered as a plant.The experiment is made to analyze the stability of fractional-order PID controller on time delay,results of which show that fractional controller has poorer performance than that in simulation.Considering the difference in condition between simulation and experiment,and the step response curves of the two both have same trend,it is still shown that fractional PID controller has a proper application in remote control system.