Adaptive robust motion control of a fast forging hydraulic press considering the nonlinear uncertain accumulator model

Abstract

This article focuses on the high-performance motion control of an accumulator assistant fast forging hydraulic press. As the accumulator has a significant impact on the motion control performance of the fast forging hydraulic press, the dynamic and static characteristics of the accumulator are studied and a simplified mathematical model is applied in the motion controller design. To hold the nonlinear parameter uncertainty associated with the accumulator model, a nonlinear damping regulator and a nonlinear robust feedback are synthesized based on the simplified mathematical model. The virtual control law “lumped flow” is proposed to act as the equivalent input of the fast forging hydraulic press, which successfully solves the decoupling problem and makes the motion controller design feasible. And the most economical distribution scheme is finally applied to synthesize the actual control law for each fast forging valve. In consideration of the parametric uncertainties and uncertain nonlinearities appearing in the mathematical model of the accumulator assistant fast forging hydraulic press, the discontinuous projection-based adaptive robust control is extended to synthesize the motion controller. Both simulation and experiment results demonstrate that with the proposed motion controller, the transient performance and final tracking accuracy are guaranteed although the system is subjected to various model uncertainties coming from both parametric uncertainties and uncertain nonlinearities. Furthermore, with the proposed nonlinear damping regulator, the influence of the accumulator can be well compensated and the control performance is improved.