Autonomous Precision Control of Satellite Formation Flight under Unknown Time-Varying Model and Environmental Uncertaint
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Autonomous Precision Control of Satellite Formation Flight under Unknown Time-Varying Model and Environmental Uncertainties Hancheol Cho 1
& Firdaus
E. Udwadia 2 & Thanapat Wanichanon 3
# The Author(s) 2020
Abstract This paper presents a new methodology for autonomous precision control of satellite formations in the presence of uncertainties and external disturbances. The methodology is developed in two steps. First, using a nominal system model that provides the best assessment of real-life uncertainties, a nonlinear controller that satisfies the formation configuration requirements is developed without making any linearizations/approximations. This closed-form control strategy is inspired by results from analytical dynamics and uses the fundamental equation of constrained motion. In the second step, an adaptive continuous robust controller is developed to compensate for model uncertainties and field disturbances to which the satellite formation may be subjected. This controller is based on a generalization of the concept of sliding mode control, and produces no chattering. The control gain is automatically updated in real time and the norm of the trajectory error is guaranteed to lie within user-provided desired bounds without a priori knowledge of the uncertainty/disturbance bounds. Since the control force is explicitly obtained, the approach is not computationally intensive, thereby making the approach ideal for on-orbit autonomous real-time satellite formation control. Numerical simulations demonstrate the effectiveness of the proposed control methodology, in which a desired formation configuration is required to be precisely and autonomously maintained despite large initial trajectory errors in the presence of uncertain satellite mass and environmental disturbances. Keywords Satellite formation flying . Time-varying uncertainties in flight environment
and satellite model . Unknown uncertainty bounds . Autonomous real-time precision control . Fundamental equation of constrained motion . Lyapunov stability
* Hancheol Cho [email protected] Extended author information available on the last page of the article
The Journal of the Astronautical Sciences
Introduction Satellite formation flying (SFF) has been in the spotlight for the last two decades because the use of multiple small satellites offers advantages such as high-resolution imaging and enhanced flexibility, efficiency, and economic benefits compared with a single large satellite [1]. However, more advanced technology is required for precision formation control mainly due to coupled dynamics between the distributed satellites and severe system uncertainties/disturbances, i.e., nonuniform gravitational potential, atmospheric drag, solar radiation pressure, and luni-solar perturbations. The SFF problem is usually explored using unperturbed, linearized equations of the real nonlinear dynamics such as Clohessy-Wiltshire equations [2] for a circular reference orbit or Tschauner-Hempel equations [3] for an elliptical reference orbit. However, contro
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