Backstepping Control based on Sliding Mode for Station-Keeping of Stratospheric Airship

Stratospheric airship is a kind of lighter than air flying devices. The vehicle is designed to be able to operate unmanned, autonomous, and operation with remote control at altitude about 20-22 kilometers above Earth. Buoyancy force is caused to long-term flights. In this paper, in order to station keeping of stratospheric airship, the integral backstepping technique based on sliding mode method in the presence of the disturbance has been developed. Firstly, the dynamic model of an airship is presented and descriptive equations are in an adequate state-space introduced for purpose of designing a controller based on backstepping strategy. Then the backstepping controller is designed. In this control strategy, the control performance due to the external disturbance is not satisfactory. Therefore, for enhancing the operation of the platform, combination sliding mode and backstepping approach is used. In this regard, by the definition of the sliding surfaces in the equations that are included the disturbance, the robustness of the system against the external disturbance has been improved. The results are indicated that the steady error has decreased also system stabilization in present of external disturbances has improved.