THE SPECIAL CASE OF FLEXIBLE SYSTEMS

A common practice is to compute the s. s.v. p(M(ju>)) at each point of a frequency gridding ( д ( * * . * . . The robustness margin Дах is deduced as:

I—- = max u(M(M)) (1.56)

kmax *Є[1, JV]

When choosing a sufficiently fine frequency gridding, good results are obtained in many practical examples. A specific problem however arises in the context of flexible systems: indeed, narrow and high peaks may be obtained on the plot of p(M(ju>)) as a function of frequency o> (see Figure 1.17). The use of a frequency gridding is unreliable in such a case: the risk is to miss a peak on the p plot, and to overevaluate the robustness properties of the closed loop (by underevaluating the value of the maximal s. s.v. over the frequency range). In the context of this new and difficult problem, chapter 10 proposes a method for computing a reliable estimate of p{M{ju>)) as a function of u>.

THE SPECIAL CASE OF FLEXIBLE SYSTEMS

0.8

 

0.7

 

06

 

0.5

 

0.4

 

03

 

THE SPECIAL CASE OF FLEXIBLE SYSTEMS

THE SPECIAL CASE OF FLEXIBLE SYSTEMS

THE SPECIAL CASE OF FLEXIBLE SYSTEMS

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