Asymmetric error-constrained path-following control of a stratospheric airship with disturbances and actuator saturation

This paper addresses the asymmetric error-constrained path-following problem of a stratospheric airship with external disturbances and actuator saturation. A path-following algorithm is proposed based on the theories of tan-type barrier Lyapunov function, vector field guidance, adaptive sliding mode control, and radial basis function neural network (RBFNN). First, to satisfy the asymmetric tracking error-constrained requirements of airship position, an asymmetric error-constrained vector field (AECVF) guidance law is presented, which can navigate the stratospheric airship along the predefined path and guarantee that the tracking error is limited by the error constraints. Second, an adaptive sliding mode attitude controller is introduced to track the desired attitudes calculated using the AECVF with disturbances. Finally, an adaptive velocity controller is added to the control algorithm to maintain an appropriate velocity. Moreover, an RBFNN saturation compensator is introduced to solve the actuator saturation problem caused by the low maneuverability. Stability analysis indicates that all the signals in the closed-loop system are uniformly ultimately bounded. Meanwhile, simulation results demonstrate the effectiveness of the proposed control algorithm. (C) 2018 Elsevier Ltd. All rights reserved.