Decentralized control of an OmniWrist laser beam tracking system

Laser communication systems developed for mobile platforms, such as satellites, aircraft, and terrain vehicles require fast wide-range beam steering devices to establish and maintain a communication link. Conventionally, the low-bandwidth, high steering range part of the beam-positioning task is performed by gimbals that inherently constitutes the system bottleneck in terms of reliability, accuracy and dynamic performance. OmniWrist, a novel robotic sensor mount capable of carrying a payload of 5 lbs and providing a full 180° hemisphere of azimuth/declination motion is known to be free of the most of deficiencies of gimbals. Provided with appropriate controls, it has the potential for becoming a new generation of gimbals systems. The approach demonstrated in this paper describes an adaptive controller enabling OmniWrist to be utilized as a part of a laser beam positioning system. It is based on a Lyapunov function that assures global asymptotic stability of the entire system while achieving high tracking accuracy. The proposed scheme is highly robust, does not require the knowledge of complex system dynamics, and facilitates independent control of each channel by full decoupling of the OmniWrist dynamics. The paper summarizes the basic algorithm and demonstrates implementation results.