Optimal Trajectory Design Of The Stratospheric Airship

Stratospheric airship is a kind of lighter-than-air vehicle, and usually operates at the height of 18~22km. As a new type of high height platform, stratospheric airship platform can provide telecommunications, television broadcasting, environment observation and monitoring, and so on. Compared with fixed-wing airplanes, stratospheric airship has the unique characteristic of long duration station-keeping. Compared with that of the satellites, stratospheric airship can ensure long endurance at geostationary position near the surface of the earth, also the cost is much lower.This paper focuses on the optimal trajectory design according to different flight phases from the ground to the stratosphere. The optimal trajectories for ascent and level flight are studied. These optimal trajectories satisfy different performance indexes, and can be used to the trajectory tracking. First of all, the dynamics model of the airship is established, and the model is simplified for the ascent and the level flight. Then the environment model is also developed including the density of the atmosphere and the wind field, which gives the practical flight condition. Next, the optimal model of straroshperic airship's trajectory planning is studied, in which the direct collocation method is used to transfer the infinite-dimension optimal problem into finite-dimension nonlinear parameter programming problem, and the SQP method is provided to solute the optimal problem. Finally, the simulation results give the optimal ascend and level flight trajectories. These trajectories satify the performance indexes, and the constraint and the influence of the atmosphere environment are taken into account. The control variables in the optimal parameters can be used as the reference of the airship's input in the flight.