Precision Motion Control of Separate Meter-In and Separate Meter-Out Hydraulic Swing System with State Constraints

Traditional independent meter-in and meter-out hydraulic systems have been widely used in industry because of their energy saving characteristics and control flexibility. However, the control accuracy is limited by the strong nonlinearities and parametric uncertainties. In addition, independent metering systems suffer from safety problem due to complex hydraulic mechanical structures. The conventional solutions to guarantee safety are using mechanical mechanisms to limit the system’s states which increase complexity further. This paper proposes a novel two loop control strategy which regards the physical limits as state constraints to alternative mechanical structures. A conventional adaptive robust controller (ARC) is utilized in the inner loop to achieve high tracking accuracy and handle the nonlinearities, uncertainties and disturbances. A third order trajectory algorithm is synthesized to modify the original severe trajectory to a modest one which will make sure that the state constraints are not violated. Simulations are carried out and the results demonstrate the effectiveness of the proposed control strategy.