Development of an adaptive disturbance rejection system for the rapidly deployable stable platform–part 1: Mathematical modeling and open loop response

A Rapidly Deployable Stable Platform (RDSP) concept was investigated at Florida Atlantic University in response to military and civilian needs for ocean platforms with improved sea-keeping characteristics. The RDSP is designed to have enhanced sea-keeping abilities through the combination of a novel hull and thruster design coupled with active control. The RDSP is comprised of a catamaran that attaches via a hinge to a spar, enabling it to transit like a trimaran and then reconfigure so that the spar lifts the catamaran out of the water, creating a stable spar platform. The focus of this research is the mathematical modeling, simulation, and response characterization of the RDSP to provide a foundation for controller design, testing, and tuning. The mathematical model includes a detailed representation of residual drag, friction drag, added mass, hydrostatic and hydrodynamic pressure, and control actuator dynamics. Validation has been performed by comparing the simulation predicted motions of the RDSP operating in waves to the measured motions of the 1/10th scale prototype measured at sea. Resulting from this paper is an empirical assessment of the response characteristics of the RDSP that quantifies the performance under extreme conditions and provides a solid basis for controller development and testing.