A Coastline Following Preview Controller for the DELFIMx Vehicle

This paper describes the development and test in simulation of a coast line following preview controller for the DELFIMx autonomous surface craft (ASC) that takes into account the reference characteristics ahead of the vehicle. The presented solution is based on the definition of an error vector to be driven to zero by the path-following controller. The proposed methodology for controller design adopts a polytopic Linear Parameter Varying (LPV) representation with piecewise affine dependence on the chosen parameters to accurately describe the error dynamics. The controller synthesis problem is formulated as a discretetime H2 control problem for LPV systems and solved using Linear Matrix Inequalities (LMIs). To increase the path-following performance, a preview controller design technique is used. The resulting nonlinear controller is implemented with the D-Methodology under the scope of gain-scheduling control theory. To build the reference path from laser range finder measurements, an automatic reference path reconstruction technique is presented that employs B-splines computed using least squares coefficient estimation. The final control system is tested in simulation with a full nonlinear model of the DELFIMx catamaran.