MINIMAL STATE-SPACE MODEL REALIZATION OF A NONLINEAR HELICOPTER

The observer-Kalman filter/eigensystem realisation algorithm is applie d to the problem of generating a minimal state-space model realisation from a nonlinear helicopter model. The paper presents an interim resu lt using a 10th order linear model, discusses the implications of this and generates some general guidelines before applying the technique t o a nonlinear model. The outcome is a linear realisation which gives a better representation of the nonlinear model than obtained using smal l perturbation linearisation methods. The technique is capable of extr acting unstable plant models from closed-loop stabilised systems, even when the feedback dynamics are not known.