Improving tracking performance of composite nonlinear feedback controllers via new reset and hold feature of nonlinear functions

This paper proposes new reset and hold feature for the nonlinear functions within composite nonlinear feedback (CNF) controllers. Reset and hold feature helps closed-loop control system to accurately track e.g., step input sequences by resetting the initial value of the controlled output whenever an individual step reference changes in value. The new reset and hold feature work independently of the chosen nonlinear function for all CNF controllers. If CNF controllers are used without the revisions proposed in this paper, then the command following ability of the closed-loop control systems may significantly degrade. Furthermore, they may also use excessive amount of control authority, which may result in actuator saturation and other practical problems. The simulation and experimental results show that the closed-loop control systems designed using the refinements of this paper provide better tracking performances both in steady-state and during transients compared with the control systems without them.