Abstract: A nonlinear mathematic model for multi-cylinder forging hydraulic press system is established, in which the uncertainty of large load and the coupling of multi-cylinder is taken into consideration. The over actuation of the hydraulic cylinder is solved using control allocation method based on generalized inverse. Then a two-level nonlinear controller is proposed to solve the above problems. Employing Lyapunov Direct Method, the inner-loop controller controls the four SISO hydraulic cylinder pressure system to achieve accurate and fast tracking for the desired pressure. To control the uncertain large load MIMO system, the out-loop controller is designed using adaptive control strategy, with reference to the control allocation theory, to obtain the desired pressure of each cylinder. Simulation and experiment demonstrate that the strategy proposed is better than the sliding mode variable structure control strategy with single controller, and high-accuracy of the leveling and tracking control under slow running can be achieved.

Key words: automatic control technology, hydraulic cylinder overactuated, control allocation, hydraulic forging press model, adaptive control