Fractional Order Identification And Control Of Hydraulic Cylinder Position System Of Internal High-Pressur Forming Equipment

With the development of modern industry,the internal high pressure forming technology has gradually become the mainstream processing technology.For the internal high pressure forming equipment,the accurate control of its hydraulic cylinder position is the key to parts forming.Fractional order computation is an extension of integer order computation with historical memory and global nature.Compared with the integer order model,the fractional order model can describe the dynamic behavior of the system more accurately.Because of the great advantage of fractional calculus in control,it can be used to model the hydraulic cylinder position system of the internal high pressure forming equipment to improve its control.In this paper,fractional order modeling and corresponding fractional order controller are designed for the hydraulic cylinder position system of an internal high pressure forming machine.Specifically,the following work has been done:Firstly,the parameter identification algorithm of the fractional order system is introduced for the hydraulic cylinder position system.The algorithm first gives an appropriate range of the order of the fractional order system,then uses the regression vector and the parametric equation to represent the output of the model,and obtains the error between the output of the system and the actual output.The system is determined by minimizing the error.The parameters are finally determined by using the interior point method to further determine the order of the system.The accuracy of the algorithm is verified by an example simulationSecondly,the internal high pressure forming machine is analyzed,the mechanism model of the hydraulic cylinder position system is determined,and the movement behavior of the hydraulic cylinder is analyzed.On this basis,based on the collected input and output data,the equation error identification algorithm is used to establish the fractional order model of the hydraulic cylinder position system of the internal high pressure forming machine.In order to reduce the influence of noise,the wavelet threshold method is used to denoise the input and output data.Then the equation error algorithm is used to identify the parameters and order of the fractional model of the hydraulic cylinder position system.Finally,the validity of the model is verified by experiments.And by comparing with the integer order model,the accuracy of the fractional model is provedFinally,the corresponding fractional order controller is designed for the model of the hydraulic cylinder position system of the internal high pressure forming machine.In order to obtain the ideal controller parameters,the performance indicators such as overshoot and adjustment time are integrated into the objective function,and the particle swarm optimization algorithm is used to optimize the objective function to obtain the ideal controller parameters.The superiority of the fractional-order controller is verified by simulation and comparison with the integer-order PID controller.The experimental results verify the effectiveness of the controller.