Active control of ER valves with application to seaport cargo handling system

This paper presents the position control of a cylinder system using electro -rheological (ER) valves with application to a seaport cargo handling syste m. On the basis of the field-dependent yield stress of the ER fluid, cylind rical ER valves are designed and manufactured. The ER valve bridge circuit for the position control of the cylinder is formulated and its governing eq uation of motion is derived. In order to demonstrate the position controlla bility, the bridge circuit is applied to a laboratory model of a cargo hand ling system consisting of two principal components: container palette trans fer car and platform controlled by ER valve-bridge cylinder. After describi ng the principle of loading and unloading procedures, a sliding mode contro ller is designed for the platform which needs to be tracked the position of the cargo ship subjected to time-varying tide and wave motion. The control ler is experimentally realized and position control results are presented.