  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 both the control design and the 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
latter property makes the method suitable especially for high-dimensional
systems. We also design a smooth projection function for addressing system
parametric uncertainties. Numerical simulations demonstrate the efficiency of
the method.
