Two-time-scale tracking control of input-saturated nonaffine non-triangular systems with uncertainties

This paper presents a novel control framework for a class of nonlinear systems with nonaffine and non-triangular structures, input saturation, and uncertainties. A two-time-scale control strategy is developed, in which the input saturation, nonaffine-in-control structure, non-triangular state couplings, and uncertainties are decoupled across different time scales. Specifically, a fast subsystem with an anti-saturation compensator is constructed to simultaneously perform coordinate transformation and mitigate actuator saturation. This leads to an order-reduced slow subsystem formulated in the error coordinate, containing unknown nonlinearities and non-triangular couplings. An observer-based controller is then designed in the slow time scale to ensure accurate tracking. The stability and boundedness of all closed-loop signals are rigorously analyzed using singular perturbation theory. Theoretical analysis demonstrates that the tracking error converges to a compact set characterized by O(1/ι)+O(ε), where ι and ε are design parameters. Comparative simulation results validate the effectiveness and advantages of the proposed method.