Nonlinear model simplification using L 2-optimal bilinearization

This contribution considers the approximation of nth order nonlinear affine input systems by bilinear systems of order higher than n to obtain simpler models for nonlinear control design. The new approach called L 2-optimal bilinearization allows us to specify beforehand a desired multivariable interval in the state space, where the resulting bilinear system is an accurate system approximation of the nonlinear plant under consideration. The accuracy of the approximation model can be determined by the approximation degree and by specifying the approximation interval. A systematic approximation procedure for applying the L 2-optimal bilinearization is provided and demonstrated via two examples.