Research On The Control Strategy Of Double Cylinder Synchronous System Under Heavy Load And Strong Disturbance

Dual-cylinder synchronous driven system has been widely used in various occasions that need heavy load driven.However,due to the non-linearity of the electro-hydraulic servo system itself and the poor control performance of the valve-controlled cylinder system under a large mass load and the position error of valve-controlled cylinder under strong load disturbance has been difficult to be effectively solved,the control characteristics of electro-hydraulic position servo system under heavy load disturbance have been studied by many scholars.In the dual-cylinder synchronous driven system,the load inconsistency and the component assembly and manufacture error will also cause the synchronization error.With the increasing demand for the performance of the dual-cylinder synchronous driven system,it is necessary to study the dual-cylinder synchronous control method under heavy load and strong disturbance.First of all,the performance of the dual-cylinder system is fundamentally dependent on the performance of a single valve-controlled cylinder,therefore,this paper firstly studies the control method of a single valve-controlled cylinder system according to the characteristics of the subject.Based on the new leakage flow calculation method,a more accurate mathematical model of valve-controlled cylinder system is established;in view of the low natural frequency and damping of heavy-duty valve-controlled hydraulic cylinder system,combined pressure feedback and velocity feedback are introduced to improve the damping ratio,natural frequency and closed-loop stiffness of the system,so as to improve the control performance of the system and the ability to resist external load interference;The parameters of feedback loop and open loop gain are adjusted according to the third order optimal form.The results of simulation and experiment show that the above control method can improve the control performance of the system significantly,which lays a foundation for further research on control strategy.Secondly,because the traditional PID control can not meet the demands of "best interference suppression" and "best signal tracking" in a control system.Therefore,the 2DOF-PID control method is adopted to achieve the best interference suppression and signal tracking characteristics of the system at the same time.Experimental and simulation results show that the 2DOF-PID control method has better control effects under the same control parameters.Then,for the piston position error caused by severe disturbance of external load is difficult to be effectively eliminated by control method,according to the dual-valve control principle,the dissertation suggests the use of flow compensation valve in the very beginning of the error to compensate the flow of the cylinder to decrease the compression and reflux of the oil under the conditions of sudden increase of load and to make up for the lack of rapidity of the main valve in small openings.Thus the error caused by load disturbance is greatly reduced and the closed-loop stiffness of the system is improved.