  For systems in canonical form with nonvanishing uncertainties/disturbances,
this work presents an approach to full state regulation within prescribed time
irrespective of initial conditions. By introducing the smooth
hyperbolic-tangent-like function, a nonlinear and time-varying state feedback
control scheme is constructed, which is further extended to address output
feedback based prescribed-time regulation by invoking the prescribed-time
observer, all are applicable over the entire operational time zone. As an
alternative to full state regulation within user-assignable time interval, the
proposed method analytically bridges the divide between linear and nonlinear
feedback based prescribed-time control, and is able to achieve asymptotic
stability, exponential stability and prescribed-time stability with a unified
control structure.
