Control Of Airship Motion In The Presence Of Wind
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This research effort develops a guidance and control system for a small airship to fly through assigned waypoints in the three dimensional space with a desired speed in the presence of wind and wind gust. In the control system development and validation, a simulation environment based on the nonlinear 6-DOF model of an airship, including the effect of the wind, is used. The airship has five control variables, the main thrust, the main thrust angle, the tail thrust, elevator and rudder deflections. The effectiveness of the elevator and rudder degrades as the speed of the airship decreases. The controller design is based on MIMO (Multi-Input Multi-Output) LQR (Linear Quadratic Regulator) method. A gain scheduling scheme is used to cover multiple operating conditions based on the forward speed. An extensive nominal condition analysis is performed to understand the variation of the nominal values of the state and control variables with the change in speed. This enabled a better choice of the nominal conditions used in the gain scheduling controller. The simulation experiments show that the airship can fly through the assigned waypoints, even when the waypoints are at different altitudes, when the commanded speed is constant. Alternatively, the way-point navigation can be achieved while commanded speed is changed if the commanded altitude is kept constant. The simulations show that altitude and the speed changes cannot be commanded simultaneously if the changes are large.