Simulation and experimental validation of electro hydraulic servo system using fuzzy logic controller

Abstract

This Paper describes the implementation of fuzzy controller for a servo valve controlled hydraulic press cylinder. The hydraulic setup consists of a 3HP motor, a single Fixed Displacement Vane Pump which delivers 25 lpm of fluid, a linear actuator of bore diameter of 80\u2005mm, piston rod diameter of 50mm and a stroke length of 250\u2005mm, a load cell of 2 ton capacity, a linear motion potentiometer of 250mm stroke length, a flapper nozzle type servo valve and a Data Acquisition system. The fluid pressure supplied to the hydraulic press cylinder is varied from 10bar to 40bar with 5bar intervals. The spool movement of the servo valve is achieved by adjusting the electrical signal supplied to the valve which ranges from 0V to 10V in forward direction and 0V to -10V in reverse direction. In order to obtain a virtual simulation, Solid Model of hydraulic system with linear actuator is developed using Solidworks. The Solid Model is imported in MATLAB using SimMechanics Link. To obtain a graphical response, the corresponding hydraulic system is built using SimHydraulic blocks and the responses are analyzed from graph. Hydraulic systems are highly non-linear because of friction and external disturbances. In order to reduce the non-linearities in the system, controller is required. For that an advanced controller called Fuzzy logic controller is proposed. The position of the linear actuator and the load exerted by the linear actuator are taken as output parameters and they are to be controlled. The output parameters are fed to the fuzzy controller through a USB interface. With these output parameters the voltage to the servo valve for spool movement is controlled by the fuzzy controller. Based on these, position and load exertion control of the servo valve is verified for various pressure ratings. The responses obtained from the system provide critical information to develop an advanced controller.