Simple Adaptive Control for Spacecraft Proximity Operations

What is it about?

This paper addresses the problem of adaptive output feedback control for spacecraft proximity operations under parametric uncertainties and unknown disturbances. Control laws using the simple adaptive control theory, which is based on the so-called model reference adaptive control approach, are derived. In the first control scheme, a position feedback adaptive control law employing a parallel feedforward configuration to satisfy sufficient conditions guaranteeing closed-loop stability is developed. Then, it is shown how the performance of this adaptive controller can be significantly improved by using a position-plus-velocity feedback adaptive control strategy. Simulations compare the performance of the adaptive controllers with a fixed gain proportional-derivative controller. Obtained results demonstrate that both simple adaptive control methodologies yield improved performance, regardless of an uncertainty in the spacecraft mass and an unknown external perturbation, when compared to the linear-time invariant benchmark controller. In addition, the position-plus-velocity adaptive feedback methodology is shown to greatly reduce the required control input force, making its implementation onboard nanosatellites feasible. Finally, experiments conducted at the Massachusetts Institute of Technology's Synchronized Position Hold Engage Reorient Experimental Satellites research facility are reported and discussed.

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