In this work, a method is developed for modeling uncertainty in the frequency domain which can be used to predict, or design systems with a specified, probability of failure to meet performance objectives. The work is an application of a probability stability/performance analysis technique being developed by the authors. An example of this technique is presented using a pilot operated proportional control valve (POPCV) system. Thirty replications of the pilot stage of a proportional control valve system were obtained by the University of Missouri and tested with one main stage valve. A model of the system is developed and used in Monte Carlo simulations based on distributions of the physical variations of the pilot valve. A mixed sensitivity H-infinity control system is developed using a frequency domain uncertainty model that only bounds a fraction of specified plants. It is shown that when the controller is implemented in a closed-loop system, only the fraction of the plants bounded in the uncertainty model are able to meet specified performance objectives. This technique allows a control designer to design higher performance control systems for mass produced systems with model uncertainty at the expense of having a specified fraction of systems not achieve a performance objective.

This content is only available via PDF.
You do not currently have access to this content.