An Experimental Study on Reducing Ramp Stress Levels Using 'Smart' Damping

The United States military has taken an increasing interest in offloading equipment and machinery from Roll-On/Roll-Off (RO/RO) vessels in open seas. However, the current design of the RO/RO Discharge Facility (RRDF) has been determined to be structurally inadequate in sea state 3, in that relative roll motions between the ship and the RRDF induce stresses above yield. This project focuses on experimentally evaluating the efficacy of the Ramp/RRDF Motion Compenstation/Mitigation System proposed by Yang and Spencer on a laboratory-scale ship/ramp/RRDF system utilizing magnetorheological (MR) fluid dampers. Design of the experimental model, verification of the dynamic properties of the system, characterization of the dampers, system identification, control design, and experimental testing are discussed. Results appear to be promising, in that semi-active control achieves performance gains over uncontrolled and optimal passive cases.