Adaptive finitetime neural control of nonstrict feedback systems subject to output constraint, unknown control direction, and input nonlinearities Abstract   This paper addresses the finitetime controller design for a class of nonlinear systems in the nonstrict feedback form subject to unknown system dynamics and disturbances, arbitrary asymmetric timevarying output constraints, four types of input nonlinearities, and unknown control direction. Utilizing the barrier Lyapunov function (BLF) and backstepping technique, an adaptive finitetime controller has been proposed. The difficulties associating with nonstrict feedback systems have been handled using the variable separation approach. Furthermore, the unknown control direction problem has been tackled by using the Nussbaum gain function. A unified framework has been utilized for handling four types of input nonlinearities, including saturation, deadzone, backlash, and hysteresis. By applying intelligent approximators, not only the unknown functions been estimated, but also the explosion of complexity problem occurring in the backstepping technique has been avoided. To reduce the computational burden, only one adaptive law has been applied and the approximator functions are not involved in the control implementation. Under the designed controller, all closedloop signals remain semiglobally practically finitetime stable (SGPFS) and the tracking error converges to a small neighborhood of the origin in a finitetime. The effectiveness of the proposed controller has been demonstrated through a simulation example.

Output feedback finitetime stabilization for highorder planar systems with an output constraint Abstract   This paper investigates the problem of output feedback finitetime stabilization for a class of highorder planar systems with an output constraint. By developing a nonsmooth observer and revamping the technique of adding a power integrator with the introduction of a new     t  a  n    type barrier Lyapunov function as well as a skillful manipulation of sign functions, a continuous finitetime output feedback stabilizer is explicitly constructed while achieving the requirement of the output constraint. The novelty of the proposed scheme lies in the unified design that is able to simultaneously perform the output feedback finitetime stabilization for systems with and without output constraints, without the need of changing the controller structure.