Pointing Control Accuracy and Robustness Enhancement of an Optical Payload System Using a Direct Adaptive Control Combined With an Optimal Control Modification

Abstract

Optical or laser payload control system is known as a high bandwidth and precision tracking control system (i.e., micro-rads attitude pointing error budget). This high frequency bandwidth together with the high angular rate operating region makes the optical and/ or laser payload design become even tougher (vulnerable to noise and low IRU measurement accuracy.) The combined broadband and narrow band jitters further degrade payload control system tracking and pointing capabilities. Given those compounded challenges, fixed-gain controllers are no longer suitable. Adaptive control design approaches have been identified as the viable path to the optical or laser payload control problem. However, selecting the right path among three major branches, Direct Adaptive (DAC), Indirect Adaptive (IAC), and Hybrid Adaptive, is another major challenge. The IAC path has been primarily investigated by the ALS community for more than one decade. The IAC performance seems to be overbought at a much higher price due to its implementation complexities and still far from reaching an acceptable mature technology level for an operational deployment. We propose to use the Dual Layered DAC Architecture, leveraging latest DAC algorithms combined with the Optimal Control Modification (OCM), as an alternative adaptive control to optical or laser payload control system. The Dual Layered DAC offers many upfront advantages and payoffs over the IAC (since DAC requires no onboard parameter estimator and no persistent input excitation). A Fast Steering Mirror control problem will be used as the benchmark case to evaluate this dual layered adaptive control solution.