UC San Diego

This dissertation develops a theory to design a controller which estimates and cancels unknown sinusoidal disturbances forcing a linear time-invariant system by using only measurement of state-derivatives of the system. Our design is based on the following steps; parametrization of the sinusoidal disturbance as the output of a known feedback system with an unknown output vector that depends on both unknown disturbance parameters and unknown plant parameters, design of an adaptive disturbance observer, and finally design of an adaptive controller. We extend the results for unmatched disturbances by using a backstepping procedure. We employ the developed controller to solve the problem of cargo transfer in high sea states over a ramp from a large, medium-speed, roll-on/roll-off (LMSR) vessel to a smaller connector vessel of a surface effect ship (SES) type. Our aim is to reduce ramp motion between the LMSR and SES in order to provide a safer environment for cargo transfer. We design an air cushion actuated controller to estimate and cancel the wave disturbance and stabilize the heave of the SES via heave acceleration feedback with actuation of the louver area for the case where the hydrodynamic and other parameters of the SES are not known a priori and the pressure dynamics of the air-cushion contains nonlinearly parameterized unknown terms. We also consider a two- chamber air-cushion SES model and design an adaptive controller to regulate heave and pitch simultaneously. In addition a tracking algorithm is proposed to keep the ramp stationary during the cargo transfer. We demonstrate the effects of our control designs in simulations in a time- domain seakeeping code, named AEGIR. We also implement the developed controller on a scale model SES. We perform several experiments in a wave tank to test the performance of the controller. It is shown that the experimental results we have obtained are consistent with the developed theory