Control and Sensitivity Analysis for the Solar Array Pointing System of the Space Station Freedom

This paper presents classical control algorithms design for the solar array pointing system of the Space Station Freedom (SSF). This development is based on continuous, rigid body model of the solar array beta gimbal assembly (BGA) containing both linear and nonlinear dynamics due to various friction components. Optimum sets of controller parameters were obtained based on integral performance criteria through EASY5 simulations in the time domain.

Classical sensitivity studies conducted in EASY5 indicated that the worst potential problem (possible system instability) is due to the variations in the electric motor dead-zone characteristics. After incorporation of an alternate static friction model, a Taguchi based tolerance design sensitivity study was conducted. Results indicated that the voltage variance, torque sensitivity constant and the motor resistance are the most important tolerances investigated with respect to integral square error (ISE).

It is expected that the present control algorithms will be implemented in the early stages of the deployed SSF.