An improved hydraulic valve and its trajectory control of valve spool based on fractional order PI controller

When the regular 4/3-way valve, which has two load orifices connected rigidly with each other, is working, there will be some throttle loss caused by these two orifices. In order to reduce the energy loss, a 4/3-way valve with improved structure and its trajectory control of valve spool with a novel tuning method for fractional order PI controller are proposed. Compared with the regular 4/3-way valve, the structure of the valve spool has great improvement. Meanwhile, because of the structural changes, the working mode of the improved valve will be significantly different from the conventional mode. Depending on the load condition, the working mode of the hydraulic valve needs to be changed timely by adjusting the position of the valve spool. Otherwise, the hydraulic valve will work in the wrong mode and the energy efficiency will not be achieved. Therefore, this paper has made some further study for the position control strategy of valve spool. It is required that the spool has rapid stet-point response and high tracking accuracy. The fractional order proportionalintegral (FOPI) controller is adopted aiming to reject the uncertainty disturbance coming from the fluid flow and friction. For the recommended controller, a parameter tuning method is proposed to calculate the parameters directly so as to satisfy the frequency domain performance. The simulation and experiment results show the control effect of the tuning methods.