Improving sector-based results for systems with deadzone nonlinearities

The conservatism of sector-based results for systems consisting of an interconnection of a linear-time-invariant (LTI) system and a static, sector-bounded nonlinearity is well known. Despite this, they are widely used in control system analysis and synthesis. This paper shows how, when the sector bounded nonlinearity is a deadzone, standard sector based results can be modified to allow the synthesis of a nonlinear controller which can deliver improved performance over standard results. The appealing feature of the method is that, as the main part of the design is done using standard sector results, the computation associated with the improved controller is essentially the same as with the standard controller. An override control example is used to illustrate the potential of the results.