Affine Parameter-Dependent Preview Control for Rotorcraft Terrain Following Flight

Abstract

This paper presents a terrain-following controller for rotorcraft that takes into account the terrain characteristics ahead of the vehicle as measured by a laser range scanner. The methodology used to solve the terrain-following control problem poses it as a discrete time path following control problem in which a conveniently defined error state-space model of the plant is augmented with terrain preview data. A piecewise affine parameter-dependent model representation is used to accurately describe the linearized error dynamics for a predefined set of operating regions. For each region, the synthesis problem is stated as a state feedback H 2 control problem for affine parameter-dependent systems and solved using linear matrix inequalities. An alternative technique to compute the feedforward preview gain matrix is proposed that avoids solving linear matrix inequalities involving a large number of unknowns. The resulting nonlinear controller is implemented within the scope of gain-scheduled control theory using the D-methodology. Simulation results obtained with the full nonlinear helicopter model are presented and discussed.