This article presents the results obtained in regulating complex physical systems of low time- constants-often less than a second or even a tenth of a second. Special emphasis is placed on unstable systems -or those that may become such in certain working conditions.
These systems which are difficult to regulate require special precautions in real industrial uses. Different algorithms such as controls using PID (Proportional plus Integrator plus Derivator controller) or pole placement, adaptive controls or, in some cases generalised predictive controls, have been tested and compared.
In the case of adaptive controls, special care is given to the problem of parameter initialization which is often crippling for such uses as the ones described here. A compromise between implementation and operation costs, calculation time, performance, etc, must be found.
Our application is a real industrial example: the braking system of a vehicle.