Synchronous Control Strategy Of Electro-Hydraulic Multiple Cylinders Position Servo System

Electro-hydraulic servo systems have the advantages of high stiffness,fast response time,high accuracy and large power-to-weight ratio.So they are widely used in aerospace,defence industry and construction machinery.In some heavy-duty equipment,multiple hydraulic cylinders are often required to work together to ensure the smoothness and reliability of equipment operation.Due to the large number of non-linearities and uncertainties in electrohydraulic multi-cylinder synchronous systems,the existence of these factors increases the difficulty of accurate synchronous control.Therefore,it is of practical importance to study synchronous control strategies with high performance.The main research elements of this paper are as follows.(1)The mathematical relationships between the physical quantities of the valvecontrolled cylinder are analysed in detail.Afterwards,a mathematical model considering the main non-linearities and uncertainties of the valve-controlled cylinder is built.So,the model can more accurately describe the dynamic and static physical characteristics of the system,which is the basis for the design of single and multi-cylinder controllers.(2)The trajectory tracking accuracy of a single cylinder is the prerequisite and guarantee for synchronous control.Based on the established non-linear mathematical model of the valve-controlled cylinder,three control strategies,namely fuzzy PID control,deterministic robust control and adaptive robust control,are designed.The tracking effect and robustness of the three control strategies are analysed and compared by MATLAB/Simulink to select the best control strategy for multi-cylinder synchronous control.(3)For the two-cylinder position synchronous control system,an adaptive robust synchronous control strategy based on the idea of cross-coupling is proposed.Firstly,a coupled error vector containing both the position tracking error and the synchronization error is designed,and then an adaptive robust controller is designed for each hydraulic cylinder to converge the coupled error vector by combining Lyapunov stability theory and the backstepping method,so that the position tracking error and the synchronization error can converge simultaneously.(4)An adaptive robust control strategy based on adjacent cross-coupling is proposed for the four-cylinder position synchronous system.On the basis of adaptive robust control for single-cylinder position tracking,the synchronization error between two adjacent cylinders is compensated by a PID coupling controller,so as to achieve accurate synchronization of four cylinders.(5)A joint simulation model is built through the AMEsim and Simulink joint simulation environment,which is used to verify the effectiveness of the proposed control strategy by comparing the numerical simulation results.The results show that among the three designed single-cylinder position control strategies,the adaptive robust control has the best effect,and the tracking accuracy of different desired trajectories can be maintained within 0.9%.The synchronisation accuracy of the adopted two-cylinder and four-cylinder position synchronisation control strategies can be controlled within 0.26% and 0.34% respectively.Additionally,the designed control strategies have strong robustness to external disturbances.