Abstract: On the subject of electro-hydraulic elevating system with multi-cylinder, a two-step nonlinear control algorithm is presented to address the motion synchronization problem after analysis of system modeling and actuator redundancy. The outer-loop controller of the proposed control algorithm is ap-plied to get desired load pressure for all cylinders designed by quantitative feedback theory and actuators redundancy theory of linear multi-input multi-output system. The other inter-loop controller which is composed of n nonlinear load-pressure con-trollers for n simple-input simple-output nonlinear system with disturbance observer theory, is used to precisely track the de-sired load-pressure for every elevating cylinder with system disturbance. The elevating results with four cylinders show that this control strategy can effectively synchronize multi-cylinder motion.

Key words: Actuator redundancy, Electro-hydraulic proportional control, Multi-cylinder, Nonlinear control, synchronization