Adaptive Friction Compensation for Line-of-Sight Pointing and Stabilization

This paper presents a new and practical adaptive friction compensation (AFC) technique developed at Texas Instruments for either analog or digital implementation. AFC is designed to augment conventional stabilization rate loops for the purpose of adapting to the characteristics of friction and canceling its torque disturbances before they cause LOS jitter. Estimates of coulomb friction level (CFL) and spatial time constant (STC), a measure of the disturbance rise time, are generated in real-time using a novel algorithm with minimal computational requirements. These estimates of CFL and STC are used to update a simple friction reference model which generates commands to cancel friction disturbances using relative rate feedforward. Laboratory tests show that stabilization can be improved by 90% to 75% depending on the base rotary environment characteristics: a) single sinusoid and b) band-limited random, respectively.