Improving Adaptation Performance For Systems With Slow Dynamics

It is often difficult to achieve good tracking performance in the presence of modeling error with the use of high adaptation gain when a system has slow modes. This leads to unnecessary high frequency control effort that can excite unmodeled dynamics. This paper introduces an adaptive control architecture that allows fast adaptation for systems with both fast and slow modes. Fast adaptation is achieved using a high bandwidth state emulator to train the adaptive element. The state emulator allows the drift part of the adaptation dynamics to be set arbitrarily. This allows a control designer to shift the adaptive process dynamics to a more favorable set and represents a new strategy for improving the adaptation process in that no modification terms need to be added to the adaptive law to improve adaptation. Though not required for system stability, the system tracking error is kept small via a low bandwidth feedback on the emulator tracking error. The usefulness of the architecture is illustrated on a nonlinear model for wing rock and a linear model of a Boeing 747.

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