Prescribed Performance Tracking for Uncertain MIMO Pure-Feedback Systems With Unknown and Partially Nonconstant Control Directions

In this article we consider designing tracking controllers for MIMO, pure-feedback systems, having unknown and partially nonconstant control directions. The proposed control scheme is static, continuous, and requires no hard calculations, analytic or numerical, to produce the control signal. Significant attribute is the enforcement of prescribed performance bounds in terms of steady-state accuracy and convergence rate. No prior knowledge regarding system nonlinearities is required and no high-order derivatives of the desired output trajectories are incorporated in the controller design. Simulation results clarify and verify the theoretical findings.