On control design for a class of parametric uncertain nonlinear systems

In this paper, a class of nonlinear systems with parametric uncertainties in the control inputs are taken into consideration and several control design approaches are investigated and compared by simulation studies. As for nonlinearity, one popular method is gain-scheduling, of which the main idea is to linearize the system at many operation points and then adopt linear control design. However, it could not achieve good performance in the presence of uncertainties. Augmenting the gain-scheduling controller with adaptive control law may improve the closed-loop dynamics, but another disadvantage is the large quantities of data processing in advance resulting from linearization which would be impossibly addressed once we take the gain-scheduling as control strategy. Therefore, nonlinear control technique of less dependence on the mathematical model is our best choice. ADRC (active disturbance rejection control) benefits from its ESO (extended state observer) to cope with the disturbance and uncertainties. Moreover, the nonlinear feedback control based on ESO upgrades the performance of the closed-loop system. Simulations are conducted to validate the effectiveness of ADRC, and comparison is carried out to figure out advantages and disadvantages for each control law.