Design of H∞ command and control loops for unmanned aerial vehicles using static output-feedback

The aim of this paper is to design a helicopter position control system with guaranteed performance that allows tracking control of unmanned aerial vehicle positions - X, Y, Z, and yaw while preserving a structure that is generally accepted in the helicopter control community. The paper presents an approach for designing compensators for shaping the closed-loop inertial positions and yaw step response using H_infin output-feedback design techniques. Simplified conditions are used which only require the solution of two coupled matrix design equations. H_infin framework is utilized to pose the problem of stabilization as an outer position command loop and an inner control loop. Inner loop controls attitude rates along with roll and pitch and provides robustness and structure. This paper thereby presents a design for hover and station-keeping control of UAV helicopters. It is shown that the rotorcraft model can be first loop shaped to achieve desired characteristics about the hover operating condition. A numerically efficient solution algorithm to solve the H_infin coupled design equations for both inner and outer loops is used. A major contribution is that an initial stabilizing gain is not needed. The efficacy of the control law and the disturbance accommodation properties are shown on a rotorcraft design example.