Variant factor Technique for Tracking Control of a Class of nonlinear Systems with input saturation

A variant factor (VF) technique is developed for the control design of a class of single-input and single-output affine nonlinear systems with input saturation. The main ideas of VF are to convert an affine nonlinear system into a linear time-invariant system similar to the dynamic inversion and then to use the ideas of the composite nonlinear feedback (CNF) technique to design a control law for the converted linear system with the input saturation. A VF is introduced to guarantee the resulting closed-loop system asymptotically stable in presence of the input saturation. The VF control laws retain the similar properties of the CNF control laws. With the VF control law, the system output can asymptotically track the step reference and the resulting closed-loop system can achieve better tracking performance than that with the control law designed with the dynamic inversion.