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Ivancevic_Applied-Diff-Geom

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<strong>Applied</strong> Bundle <strong>Geom</strong>etry 541This linearization method will be exact in a finite domain, rather thantangent as in the local linearization methods, which use Taylor series approximation.Nonlinear controller design using the technique is called exactfeedback linearization.Algorithm for Exact Feedback Linearization. We want to finda nonlinear compensator such that the closed–loop system is linear (seeFigure 4.3). We will consider only affine SISO systems of the type (4.44),i.e, ẋ = f(x) + g(x) u, y = h(x), and we will try to construct a control lawof the formu = p(x) + q(x) v, (4.45)where v is the setpoint, such that the closed–loop nonlinear systemẋ = f(x) + g(x) p(x) + g(x) q(x) v,y = h(x),is linear from command v to y.Fig. 4.3Feedback linearization (see text for explanation).The main idea behind the feedback linearization construction is to finda nonlinear change of coordinates which transforms the original system intoone which is linear and controllable, in particular, a chain of integrators.The difficulty is finding the output function h(x) which makes this constructionpossible.We want to design an exact nonlinear feedback controller. Given thenonlinear affine system, ẋ = f(x) + g(x), y = h(x),.we want to find thecontroller functions p(x) and q(x). The unknown functions inside our con-

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