Spacecraft Collision Avoidance Using Coulomb Forces with Separation Distance and Rate Feedback

A two-spacecraft collision avoidance problem is discussed in this paper. The spacecraft are assumed to be floating freely in deep space. A control strategy using cluster internal coulomb forces is developed to prevent a collision of the two spacecraft. The control law is designed to keep the separation distance greater than a specified constraint value, and is also designed to keep the departure relative kinetic energy at the same level with the approach kinetic energy. Further, this strategy requires only the measurements of the separation distances and the distance rates. If the achievable spacecraft charge levels are limited, then it is not guaranteed that the collision can always be prevented. Formulating the relative motion of the charged spacecraft using the concepts of orbital mechanics allows us to analyze the conditions under which a collision can be avoided. Given an initial separation distance and distance rate, the minimum spacecraft charge limit required to guarantee collision avoidance is determined. Or, inversely, when the limitations of charges are given, the maximum approach speed at which a potential collision can be avoided is estimated. Numerical simulations illustrate the analytical results.