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ETTC'2003 - SEE

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Indeed, when the objective of the test is to determine the structure<br />

characteristics, it is difficult to have a model with genuine parameters.<br />

Besides, even if you know the parameters that characterize the tested<br />

structure, you have to take into account the fact that these parameters may vary<br />

during the test.<br />

So any control system can not be chosen to guaranty the performance.<br />

Robust control is a control system design that permits to take into account the<br />

parameters variations of the model.<br />

The part 1 of this paper introduces a robust control system design that is<br />

applied to a hydraulic test bench that will be part of the test devices of LAMEFIP-<br />

ENSAM. The test bench includes a hydraulic actuator whose cylinder is linked to<br />

the mechanical structure to be tested. The tested structure is compressed by the<br />

actuator at constant velocity in order to determine its characteristics. The control<br />

system must take into account the fact that the parameters of the tested structure<br />

are not well-known and change during the test<br />

The parts 2 & 3 of the paper introduce some other test devices that are<br />

available at ENSICA and ENSAM.<br />

1 - Benefits of robust control for test devices<br />

1.1 - What is robust control ?<br />

The design of a control law requires a model of the process to control. The<br />

model can only be imperfect. However it is used in order to design control and to<br />

guaranty stability, stability margins, precision, performance,…<br />

Thus it is legitimate to question oneself on the behaviour of the control<br />

system with respect to the model uncertainties. A property of control is said to be<br />

robust if it is maintained in spite of the model uncertainties. It is possible to check a<br />

posteriori the behaviour of the control system with respect to uncertainties but it<br />

would be a saving in time and in money to design a control system that permits to<br />

take into account the uncertainties of the model a priori. This is the objective of the<br />

robust control.<br />

Different methodologies of robust control have been developed. The<br />

methodology proposed in this article is the CRONE control system design.<br />

ETTC2003 European Test and Telemetry Conference

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