Research on a New Azimuth Control Method for Stratospheric Balloon-Borne Gondola System

Abstract

For a class of non-matching uncertain nonlinear system such as stratospheric balloon-borne gondola azimuth control system, a new robust adaptive multiple sliding mode controller is proposed. In this control method, the virtual and the practical control variables are obtained by designing the multiple sliding modes step-by-step. For avoiding the chattering problem generated by discontinuous input, the traditional sign function is replaced by hyperbolic tangent function. Meanwhile, the CMAC neural network is used to approximate the system uncertainties and the derivative of virtual control input online, which can reduce the conservation of controller parameters design. The system stability analyses show that the control method can guarantee that the output tracking error and slide modes asymptotically convergent to boundary layer. The simulation results show that the controller has higher tracking accuracy, and stronger robust to nonlinear and uncertainty of system, and it also can be applied to other similar non-matching uncertain nonlinear systems.

Modeling of stratospheric balloons and robust line-of-sight pointing control

“…To the authors knowledge, there exists no general model-based methodology for controller synthesis in the literature, and, more critically, experimental ground-based setups are not representative of the dynamics of the fully deployed system in flight (which cannot be obtained in laboratory due to the dimensions of the system), whereas flight experience proves that the lineof-sight control is essentially limited by the rejection of the natural pendulum-like modes of the flight chain [2], excited by wind disturbance. Although some more advanced control techniques were investigated (pole assignment [2,15], LQR synthesis [14], adaptive control [16], sliding mode control [21,45], Lyapunov stability theory [26]), they provide very few insight on the achievable performance. The third contribution of this paper is a general methodology to address the line-of-sight pointing control of an optical instrument onboard a stratospheric balloon as a robust structured H 2 ∕H ∞ problem.…”