small spacecrafts formation using potential functions

Paper number

IAC-08.C1.1.3

Author

Dr. Ahmed Badawy, Military Technical College, Egypt

Coauthor

Prof. Colin R. McInnes, University of Strathclyde, United Kingdom

Year

2008

Abstract

ABSTRACT

A group of small spacecrafts able to change its orbital formation through using the potential function is discussed. All objects are assumed to maneuver under discrete thruster effects. A hyperbolic form of attractive potential function is then used to reduce the control intervention by using the natural orbital motion for approaching goal configuration. A superquadric repulsive potential with 3D rigid object representation is then used to have more accurate mutual sensing between objects. As spacecrafts start away from their goals, the original parabolic attractive potential become inefficient as the continuous control force increases with distance linearly. The hyperbolic attractive potential offers good representation for the control force independent on the distance to goal, ensuring global stability as well. 
 

INTRODUCTION
The notion of artificial potential fields was described initially for robot motion planning and manipulators. The original overall potential field is composed of two independent functions, attractive and repulsive. As robotics technology enhances, maneuvering requirements become more demanding as well. Since then lots of modification to the original potential function were introduced in fields of dynamic environment, object real shapes, object rotations. The attractive potential reforms object configurations to those of the predefined goals, positions and orientations. Originally translation attractive potential was completely unlinked with the rotational one. This dependency is carried out through the repulsive potential which should incorporate both relative positions and orientations. The repulsive potential is defined whenever more than one maneuvering object exists in the environment. Many functions are suitable for obstacle representation like FIRAS, Superquadric deformable functions, Gaussian distributions, and Laplace functions, etc. 
In order to enhance the intelligence level of maneuvering objects, enabling them to have better choice of control action when interfered by obstacle or other maneuvering objects, discrete control approach is discussed in this paper using hyperbolic attractive potential field along with the superquadric obstacle fields. The hyperbolic attractive potential provides global stability, and maintains bounded control force even reaching zero force whenever the natural orbital motions are enough for rendering object distance to goal to zero. The superquadric model forms repulsive potential fields according to objects dimensions in 3D, hence it sense their rotation and the coupling between translation and rotation is achieved.

Abstract document

IAC-08.C1.1.3.pdf

Manuscript document

IAC-08.C1.1.3.pdf (🔒 authorized access only).

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