Under-actuated Stratospheric Airship Research Articles

Path‐Following Control of Underactuated Stratospheric Airship With Constraints and Disturbances Using Time‐Delay Observer

ABSTRACTThis paper investigates the path‐following control problem for an underactuated stratospheric airship with unknown dynamics, external disturbances, and constraints. A novel error‐constrained Serret–Frenet frame has been utilized to drive the underactuated airship to track the predefined path. A novel control approach that combines backstepping and time‐delay observer (TDO) has been employed for tracking the desired forward velocity and estimating unknown dynamics and disturbances without the details of the airship's dynamics. The position error and velocity constraints of the airship are handled by nonlinear mapping. The proposed control scheme can drive an underactuated airship to track the predefined path and the constraints requirements are never violated. Simulations demonstrate the effectiveness and advantages of the proposed control scheme.

Path-following control of an underactuated stratospheric airship with unknown dynamics and external disturbances using time-delay control

In this paper, the path-following problem for an underactuated stratospheric airship with unknown dynamics and external disturbances has been studied. Vector field guidance is employed to fix the underactuated issue and generate desired heading. Time-delay control (TDC) is utilised to track desired states and estimate the model uncertain and disturbances using simple delayed states. To compensate time-delay estimation (TDE) errors, terminal sliding-mode is utilised and combined with TDC. The stability of the proposed controller is provided by using Lyapunov function. A numerical simulation is demonstrated to prove the performance of the proposed control algorithm.

Neuroadaptive output-feedback trajectory tracking control for a stratospheric airship with prescribed performance

ABSTRACTIn this article, we investigate the horizontal trajectory tracking problem for an underactuated stratospheric airship subject to nonvanishing external disturbances and model uncertainties. By transforming the tracking errors into new virtual error variables, we can specify the transient and steady-state tracking performance of the resulting nonlinear system quantitatively, which means that under the proposed control scheme, the tracking errors will converge to prescribed residual sets around the origin before a preselected finite time with decay rates no less than a preassignable value. To address unknown items, minimal learning parameter (MLP) techniques for neural networks (NNs) approximation are employed, which efficaciously relax the computational burden, enhance the robustness against dynamics uncertainties and provide an improved property for disturbances rejection. A finite-time convergent observer (FTCO) is incorporated into the control framework to realise output-feedback control, ensuring that estimation errors are bounded during operation and approach zero within a finite time. Stability analysis proves that all the closed-loop signals are uniformly bounded. The effectiveness and advantages of the proposed control strategy are verified by simulation results.

Adaptive sliding-mode-backstepping trajectory tracking control of underactuated airships

The problem of trajectory tracking control for an underactuated stratospheric airship with model parameter uncertainties and wind disturbances is addressed in the paper. An adaptive backstepping sliding-mode controller is designed from the airship nonlinear dynamics model. The proposed controller has a two-level structure for trajectory guidance, tracking and stability, and the developed controller, based on nonlinear adaptive sliding-mode backstepping method, provides airship attitude and velocity control for the entire flight process. Furthermore, an active set based weighted least square algorithm is applied to find the optimal control surface inputs and the thruster commands under constraints of actuator saturation. The closed-loop system of trajectory tracking control plant is proved to be globally asymptotically stable by using Lyapunov theory. By comparing with traditional backstepping control and PID design, the results obtained demonstrate the capacity of the airship to execute a realistic trajectory tracking mission under two cases of lateral- and roll- underactuations, even in the presence of aerodynamic coefficient uncertainties, and wind disturbances.

Three-Dimensional Path-Following Backstepping Control for an Underactuated Stratospheric Airship

In this paper, a three-dimensional (3-D) path-following control design for an underactuated stratospheric airship is proposed based on the parameterized path description. The desired attitude, velocity, and the path parameter updating law are obtained by employing the guidance-based path-following principle. The resultant system possesses a cascaded structure, which consists of a guidance loop, an attitude stabilization loop, and a velocity tracking loop. The stability analysis shows that the path-following error and all states of the closed-loop system are ultimately uniformly bounded. Simulation results demonstrate the effectiveness of the proposed controller.

Station-keeping Control of an Underactuated Stratospheric Airship

This paper studies the station-keeping control of underactuated stratospheric airships in the presence of model uncertainties and wind field, and a T–S fuzzy model-based adaptive backstepping SMC (sliding mode controller) is proposed. Firstly, a fuzzy dynamics model is constructed to represent the local dynamic behaviors of the given 6-DOF nonlinear dynamics of an airship. And different from the traditional algorithm, the station-keeping control is resorted to path-following control. Then, the guidance-based path-following principle is adopted to obtain the guidance law, and the backstepping technique is used to obtain the desired velocities. In order to solve the problem of model uncertainties between T–S fuzzy model and nominal model, the sliding mode control approach is adopted. Adaptive terms are designed to estimate the upper bound of the uncertainties. Besides, a wind field observer is designed to estimate the speed and direction of the wind. The stabilization of the system is discussed using Lyapunov stability theory. Finally, numerical simulations are given to demonstrate the effectiveness of the proposed method.

Robust three-dimensional path-following control for an under-actuated stratospheric airship

This paper proposes a robust three-dimensional (3-D) path-following controller for an under-actuated stratospheric airship in the presence of uncertainties. The resultant control system exhibits an inner-outer loop control structure. In the outer control loop, the path-following error dynamics is constructed in a moving Serret-Frenet frame and a new guidance law with the sideslip and attack angle compensation is designed, which decreases the path-following steady-state error. In the inner control loop, a disturbance observer based backstepping control law is proposed to achieve the desired dynamic behavior on the path. Furthermore, a new velocity tracking control strategy is developed which aligns the resultant velocity tangent to the path. Finally, numerical simulation results are shown to verify the effectiveness of the proposed controller.

Underactuated Stratospheric Airship Trajectory Control Using an Adaptive Integral Backstepping Approach

This paper deals with trajectory tracking control for an underactuated stratospheric airship in the presence of model uncertainties and external disturbances. An adaptive integral backstepping trajectory control is designed from the underactuated airship nonlinear dynamics model. The proposed controller has a two-level structure. A low-level controller based on nonlinear adaptive integral backstepping method stabilizes the attitude and velocity of the airship, whereas a high-level controller performs guidance and trajectory tracking task. Two underactuated cases of zero lateral control force and zero roll moment input are studied. Meanwhile a control allocation component based on active set with weight least square algorithm is put into the low-level controller, to find the optimal control surfaces and thrust inputs under constraints of actuator saturation. By using Lyapunov theory the closed-loop trajectory control system is proven to be globally asymptotically stable. Finally, simulation results show that the proposed adaptive integral backstepping controller can follow the reference even in the presence of parametric uncertainties and external disturbances and time delay inputs.

Error-constrained path-following control for a stratospheric airship with actuator saturation and disturbances

ABSTRACTThis paper is concerned with the path-following control problem for an under-actuated stratospheric airship with error constraint, actuator saturation, and external disturbances. To address the tracking error-constrained requirements of airship position and attitude, novel tan-type barrier Lyapunov functions are proposed and incorporated with the guidance and attitude control schemes, which calculate the desired attitude and angular velocity. An auxiliary design system in the form of anti-windup compensator is employed to deal with actuator saturation, and the stability of the saturated control solution is verified. Nonlinear disturbance observer is developed to estimate the unknown external disturbances. Rigorous stability analysis shows that the constrained requirements on the airship position and attitude will not be violated under the proposed control method and all closed-loop signals are uniformly ultimately bounded, despite the presence of actuator saturation and disturbances. Simulation results and comparisons illustrate the effectiveness of the proposed controller.

Finite-time path following control for a stratospheric airship with input saturation and error constraint

ABSTRACTThis paper addresses the finite-time path following control problem for an under-actuated stratospheric airship with input saturation, error constraint, and external disturbances. To handle the adverse effect of input saturation, anti-windup compensators are employed and finite-time convergence of the saturated control solution is established. Error constraints of airship position and attitude are handled by incorporating a tan-type barrier Lyapunov function (TBLF) in guidance and attitude control schemes. Backstepping design is presented with the anti-windup compensators, the TBLF, and nonlinear disturbance observers which estimate the external disturbances. Stability analysis shows that the tracking errors of the airship position converge into a small set around zero within finite-time, the constrained requirements on the airship position and attitude are not violated during operation, and all closed-loop signals are guaranteed to be uniformly ultimately bounded. Compared with the conventional control scheme, simulation results illustrate that the proposed finite-time controller offers a faster convergence rate and a higher path following accuracy for the stratospheric airship.

Vectorial backstepping method–based trajectory tracking control for an under-actuated stratospheric airship

ABSTRACTA new trajectory tracking control approach for an under-actuated stratospheric airship is proposed. There is a two-level structure of the proposed controller. A low-level controller based on non-linear vectorial backstepping method, with the rigid-body dynamics expressed on vector form, stabilises the attitude and velocity of the airship, while a high-level controller performs guidance and trajectory tracking task in the three-dimensional (3D) space. Furthermore, a control allocation module based on the active set algorithm is incorporated into the low-level controller to optimise the practical control inputs under constraints of actuator saturation. The closed-loop trajectory tracking control plant is proved to be globally exponentially stable through the Lyapunov theory. Finally, simulations show that the vectorial backstepping trajectory tracking controller can achieve desired tracking performances even if the airship is affected by parametric uncertainties and exogenous disturbances.

Global path following control for underactuated stratospheric airship

This paper develops a nonlinear path following control method that drives an underactuated stratospheric airship onto a predefined planar path with a given speed profile. The dynamic model of the airship used for controller design is first introduced with kinematics and dynamics equations. In order to render good pilot behavior for the control action, a guidance controller by referring to the guidance-based path following principle is derived. Then the controller is extended to cope with the airship attitude and velocity by resorting to the backstepping and Lyapunov-based techniques. The designed control system finally possesses a cascaded structure which consists of guidance loop, attitude control loop and velocity control loop. Stability analysis shows that the controlled closed-loop system is globally asymptotically stable, and the sway velocity which cannot be directly controlled is bounded. Simulation results for the airship following typical paths are illustrated to verify effectiveness of the proposed approach.

Planar path following control for stratospheric airship

A novel planar path following control method for an underactuated stratospheric airship is presented in this study. Firstly, the Guidance-Based Path Following (GBPF) principle and the Trajectory Linearisation Control (TLC) theory are described. Then, dynamic model of the stratospheric airship is introduced with kinematics and dynamics equations. Based on this model, a path following control strategy integrated GBPF principle and TLC theory is deduced. The designed control system possesses a cascaded structure which consists of guidance law subsystem, attitude control loop and velocity control loop. Stability analysis shows that the controlled closed-loop system is asymptotically stable. Finally, simulations for the stratospheric airship and flight experimental results for a low-altitude airship to follow typical paths are illustrated to verify effectiveness of the proposed approach.

Trajectory tracking control for underactuated stratospheric airship

Stratospheric airship is a new kind of aerospace system which has attracted worldwide developing interests for its broad application prospects. Based on the trajectory linearization control (TLC) theory, a novel trajectory tracking control method for an underactuated stratospheric airship is presented in this paper. Firstly, the TLC theory is described sketchily, and the dynamic model of the stratospheric airship is introduced with kinematics and dynamics equations. Then, the trajectory tracking control strategy is deduced in detail. The designed control system possesses a cascaded structure which consists of desired attitude calculation, position control loop and attitude control loop. Two sub-loops are designed for the position and attitude control loops, respectively, including the kinematics control loop and dynamics control loop. Stability analysis shows that the controlled closed-loop system is exponentially stable. Finally, simulation results for the stratospheric airship to track typical trajectories are illustrated to verify effectiveness of the proposed approach.