Slew-induced deformation shaping

Abstract

Computed torques for pointing and tracking require compensation for slew-induced structural, forebody/aftbody, or optical train alignment deformations. Thus even if only line-of-sight variables are to be commanded, full state feedback is needed. The solution proposed is to decouple by feedforward of the line-of-sight slew dynamics into the deformation control loop. It is shown how arbitrarily few actuators are needed for such deformation shaping, at the cost of higher differentiability of the reference line-of-sight dynamics. The low-rate, single-axis case is developed in detail, and its extension to high rates and multiple axes by global feedback linearization is outlined.