Subsystem-Based Control With Modularity for Strict-Feedback Form Nonlinear Systems

This study proposes an adaptive subsystem-based control (SBC) for systematic and straightforward nonlinear control of nth-order strict-feedback form (SFF) systems. By decomposing the SFF system to subsystems, a generic term (namely stability connector) can be created to address dynamic interactions between the subsystems. This 1) enables modular control design with global asymptotic stability, 2) such that the control design and its stability analysis can be performed locally at a subsystem level, 3) while avoiding an excessive growth of the control design complexity when the system order n increases. The abovementioned properties make the proposed method suitable especially for high-order systems. We also design a smooth projection function for the system parametric uncertainties. The efficiency of the method is demonstrated in simulations with a nonlinear fifth-order system.