Research On Flight Motion Control Of A Stratospheric Airship

A stratospheric airship is a low-speed near space aerostat capable of autonomous flight with relying on buoyancy to stay in the air.The stratospheric airship has broad application prospects,such as relay communication,traffic monitoring,military recon-naissance based on its advantages of more sustained airborne presence,higher safety,better economy,energy conservation and environmental protection and so on.This pa-per mainly studies flight motion control of the stratospheric airship with the dynamic model.The specific research contents are as follows:To achieve altitude adjustment of the stratospheric airship,a control strategy for regulating its elevator to change altitude is studied,depending on the kinematics and dynamics models.A desired pitch angle tracking equation is first presented to achieves altitude error convergence.Then applying small disturbance theory to the airship mod-el,the active disturbance rejection control law is introduced for pitch angle.The con-troller parameters can be tuned to ensure tracking expected pitch angle and stability of the system through the pole assignment method.Altitude of the stratospheric airship is regulated to reach the desired value under the proposed control law,which solves the problem of underactuated stratospheric airship altitude control.Three-degree-of-freedom trajectory tracking of the stratospheric airship is inves-tigated.With a simplified planar mathematical model based on Lagrange dynamics equation,an adaptive backstepping sliding mode controller is designed to weaken the chattering problem of the sliding mode and keep the airship to globally asymptotically track a desired trajectory.Lyapunov functions are used to ensure the tracking perfor-mance when model parametric uncertainty and external disturbance exist.Simulation results are given to verify the proposed control strategy possesses effectiveness and good robustness.A terminal sliding mode control approach based on extended state observer is pro-posed for attitude tracking control problem of a stratospheric airship.Due to the char-acteristic such as nonlinear,strong coupling,the attitude control system is decoupled into three single input single output subsystems through active disturbance rejection control technique.Extended state observer can achieve estimation and compensation of disturbance for each subsystem.Using the state of observation,a terminal sliding mode control law is designed to obtain finite time convergence and ensure good ro-bustness to disturbance.Simulation results show that the attitude of the airship can be stabilized at the desired value in the specified time.