This paper presents the design of an adaptive augmentation for cascaded outer-loop path and inner-loop acceleration tracking controllers. The adaptive augmentation is based on a nonlinear design plant and uses model reference adaptive control (MRAC). The outer-loop position controller is a nonlinear model predictive controller (NMPC) with velocity adjustment which incorporates the states and control input constraints. Acceleration tracking is achieved by using nonlinear dynamic inversion with dynamic thrust extension. To increase robustness to uncertainties, an adaptive augmentation scheme is proposed. In contrast to classical MRAC, where the augmentation drives the system towards a desired closed-loop behavior, the plant dynamics are driven towards a nonlinear design plant. This approach decouples baseline control and design of adaptation. Simulation results are shown to illustrate the robustness of the adaptive augmentation.
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