Prescribed Performance Tracking of Uncertain MIMO Nonlinear Systems in the Presence of Delays

In this article, we design a low-complexity state-feedback controller for uncertain multi-input and multi-output (MIMO) nonlinear systems, capable of imposing prespecified performance attributes (in terms of maximum steady-state error and minimum convergence rate) on the output tracking errors, in the presence of time-varying delays both in the state measurement and control input signals. The state measurement delay is considered known and the control input delay unknown though bounded by some known constant. The control design does not incorporate any knowledge regarding the controlled system nonlinearities and does not require derivatives of the desired trajectories. We verify the theoretical results by simulation studies performed on a two-link robotic manipulator.