Design of control system for disturbance rejection of an autonomous airship and flight experiment

飞艇是一种独特的交通工具，可以实现安全、长时间的飞行和空间站保持。近年来，人们对无人驾驶飞艇的兴趣日益浓厚。许多有趣的项目正在进行中，如平流层平台项目，其中平流层飞艇被用作替代卫星的移动和低成本的高速无线通信平台。位置姿态控制是其中最重要的部件技术之一。研究了欠驱动飞艇的平面位置和姿态控制问题。欠驱动飞艇是一个独立输入少于待控制自由度的非完整系统。对于存在持续风扰动的欠驱动飞艇动力学存在有界不确定性的情况，研究了全局鲁棒镇定问题和渐近抗扰问题。利用光滑时变坐标变换将飞艇问题转化为线性系统问题。该变换与系统的初始状态无关，且是非奇异的。获得了以下优点。首先，提出了一种新的鲁棒控制器，以保证系统在任意初始状态下的指数稳定性和在存在植物不确定性的情况下对风扰动的渐近抑制。其次，基于众所周知的线性控制理论的设计方法简单明了。设计方法简单，涉及一定的代数里卡第方程。最后，通过实验验证了所提控制系统的有效性。

Airship is a unique vehicle which enables safe and long-duration flight and station keeping. Recently, the interest to unmanned airships has been increasing. Many interesting projects are in progress such as Stratospheric Platform Project, in which the stratospheric airship is utilized as a mobile and low-cost platform for high-speed wireless communication instead of satellites. The position and attitude control is one of the most important component technologies.This study deals with the problem of controlling both the planar position and orientation of an under-actuated airship, which is a nonholonomic system with fewer independent inputs than degree of freedom to be controlled. Both robust global stabilization problem and asymptotical disturbance rejection one are considered for the case where the dynamics of the underactuated airship are subjected to bounded uncertainties in the presence of a persistent wind disturbance. A smooth and time-varying coordinate transformation is utilized to reduce the problem of the airship to that of a linear system. The transformation is independent of the initial state of the system and is nonsingular. The following advantages are obtained. Firstly, a new robust controller is presented to guarantee both exponential stability of the system for any initial states and asymptotically rejection against the wind disturbance in the presence of the plant uncertainties. Secondly, the design method based on the well-known linear control theory is simple and straightforward. The design method is simple, and it involves a certain algebraic Riccati equation. Finally, experimental results show the effectiveness of the proposed control system.