Improvement of trajectory tracking performance via modified composite nonlinear control

In this paper, a modified version of composite nonlinear feedback (CNF) control method is proposed to achieve fast and accurate trajectory tracking for linear systems subject to input saturation and unknown disturbances. The basic idea is to incorporate a reference generator which constructs the target state vector corresponding with the trajectory reference signal, and an extended state observer which estimates both the system states and the disturbance, into the framework of robust CNF control. The control scheme can retain the fast transient performance of CNF control, and at the same time eliminate the steady-state bias due to disturbances. Simulation studies are conducted to verify that the control method can achieve good transient performance and steady-state accuracy in various trajectory tracking tasks and is more robust against the amplitude variations of disturbance/target reference.