Practical prescribed time tracking control with user pre-determinable precision for uncertain nonlinear systems

In this paper we present a practical prescribed time (PPT) control for a class of uncertain nonlinear systems to achieve pre-assignable precision within a finite time that can be specified in advance irrespective of initial condition or any design parameter. Specifically, by introducing a novel time-varying constraining function, we convert the original finite-time tracking control problem into one with a deferred constraint on tracking error, then by stabilizing of which, we solve the problem with the following appealing features: 1) both settling time and tracking accuracy can be explicitly specified in advance regardless of initial conditions; 2) the proposed control is based upon regular (rather than fractional power) state feedback, thus is continuous and smooth everywhere; and 3) the results are global in that the prescribed time tracking is ensured for states starting from anywhere within physically possible domain.