VSC/QFT robust design of systems with bounded uncertainties

The primary goal of this work is to describe a new approach for robust nonlinear control system design. The new approach combines the robustness of quantitative feedback theory (QFT) while in the reaching phase and the insensitivity of variable structure control (VSC) to controller errors while in the sliding mode.; The design is based on variable structure control (VSC) for globally linearized models subject to strict bounds on the discontinuous control. A quantitative feedback theory (OFT) robustness compensator is designed to reduce the effect of parameter variations and disturbances on the system while in the reaching phase and meet design specification in spite of strict bounds on the discontinuous control.; With the new approach, the switching of the discontinuous control is reduced to an acceptable level while preserving the fast response associated with VSC. VSC errors due to disturbances in the reaching phase are minimized. The compensator tolerance to parameter errors is high as compared to OFT and the need for a prefilter is eliminated.