Strong-Nonlinear-Load-Disturbance-Compensation-Based Position Tracking Control of Electrohydraulic System for Bidirectional Powder Compaction Press

The powder-compaction process distributes the stress by a variety of kinematic processes that involve sliding, rotation, friction, particle deformation, and rupture. Thus, load stiffness presents complex nonlinear time-varying characteristics, and the so-called mismatched disturbances pose great challenges to the high accuracy tracking controller design of the electrohydraulic system for bidirectional powder compaction press (BPCP). Hence, designing a universal high-performance tracking controller applicable to the granular materials compaction process is of practical significance. In this article, a cancellation mechanism-based nonlinear load observation compensator is proposed to improve the position tracking performance and minimize the compaction velocity fluctuations of the BPCP. The proposed method consists of an open-loop control with feedforward based on a cancellation mechanism and a closed-loop system with negative feedback to yield a stable control system. The main contribution of this article is that the proposed solution attenuates the adverse effects of the nonlinear load disturbances and makes the system behave like a quasi-decoupled linear system, thereby reducing the complexity of the control system. Comparative experiments are performed on an electrohydraulic system for the BPCP to verify the superiority of the proposed control strategy.