Yasuaki Oishi
Department of Systems Design and Engineering, Nanzan University

and Groupe MAC, LAAS-CNRS, France

A sampled-data control system is a practically important system,
where a continuous-time plant is controlled by a discrete-time
controller. In this talk, the following two problems are
considered:
1. Analysis of passivity degradation under the sampling of a
nonlinear system;
2. Analysis and control of a sampled-data system whose sampling
interval is uncertain and variable with time.
The first problem is motivated by the well-known fact: passivity
is lost under discretization even if the original continuous-time
system is passive. Although this property has been discussed
qualitatively, a quantitative study is made here on three types
of discretization. The result can be used, for example, the
choice of the sampling interval.
The second problem has its motivation in networked control and
embedded control, where uniform sampling is not expected. In the
approach to be introduced, the problem is described in a robust
linear matrix inequality, which is a parameter-dependent linear
matrix inequality to be satisfied for all the possible parameter
values. Although the robust linear matrix inequality is
intractable directly, a tractable sufficient condition can be
obtained with the mean-value theorem and the S-procedure.
Conservatism of the approach can be reduced to any degree. This
is a joint work with Hisaya Fujioka.

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