Servo System Analysis And Design Of Sliding Mode Variable Structure Controller

Electro-hydraulic servo system has high and fast response, controlprecision and larger output power etc, it has been widely applied in variousfields of industrial control and nation defense industry. However,electro-hydraulic servo system in practice has complex workingenvironment(uncertainties outside interference), the changes in its parametersand a series of factors, it is difficult to establish accurate mathematical modelaccording to the system, the controller design for linear systems lack of goodadaptability and anti-interference, can not meet the control performance thedesired.In this paper, the electro-hydraulic position servo control system asresearch object, by linearizing the AMESim software analysis tools, themathematical model of electro-hydraulic servo system is get. Valve-controlledsymmetrical cylinder systems and valve-controlled asymmetrical cylindersystems whose characteristics of the cylinder piston in the different position areanalyzed. The sliding mode variable structure control method is used in theelectro-hydraulic servo system, and the sliding mode variable structurecontroller is designed, and carry on the experiment in the AMESim/Matlabco-simulation platform, the results showed that the ability of sliding modevariable structure control for the tracking of signals and anti disturbance hasgood performance, but there is chattering phenomenon greatly in the output ofthe controller, which needs to be improved.For the chattering problem of sliding mode variable structure control, thispaper presents three kinds of improved methods. First of all, this paper designsan improved boundary layer method, in the boundary layer using a nonlinearfeedback, a smaller system state converges to the sliding mode surface area,making the system reach the sliding surface for a limited time surface. Secondly,this paper designs double power-law exponent reaching law, in which thecontrol system dynamic quality and speeds up the approaching sliding surface.Thirdly, the fuzzy control and the sliding mode variable structure are combined and use fuzzy control to compensate the amount of sliding mode control, inorder to overcome the chattering of sliding mode variable structure controlproblems. Finally, three improved methods on AMESim/Matlab co-simulationplatform are for simulation experiments. The results show that: Improvedboundary layer method effectively accelerate the system state approaching speedsliding surface. The fuzzy sliding mode control method effectively weakens thesystem exists chattering. The double power-law exponent reaching law methodnot only weakens the system chattering, and speeds up the approaching systemin the sliding mode surface.