NASA 1998 SBIR Phase I

PROPOSAL NUMBER: 98-1 01.04-1215

PROJECT TITLE: Globally Stable Design and Analysis Tools for Reconfigurable Systems with Saturating Acuators


When aircraft operate with effectors at their rate or position limit, thecontrol loop is opened and a number of problems can occur ranging from performance degradation to loss of stability. For this reason, most modern control laws are designed to avoid actuator saturation during normal operation. In the event of a failure, however, it may be necessary to operate with one or more actuators in saturation to achieve the required level of closed-loop performance. This research will develop global analysis techniques and design tools for linear systems subject to actuator saturation. Building upon promising results obtained using a semi-global framework this research will address robust global stabilization in the presence of matched uncertainties (e.g., actuator saturation), robust output regulation from global initial states, and disturbance decoupling with global asymptotic stability. It is expected that the techniques developed in the proposed effort will lay the groundwork from which more challenging global control problems in the presence of actuator saturation, unmatched uncertainties, and unmatched disturbances can be approached. As part of the effort, the proposers will develop a prototype MATLAB toolbox to assist engineers in applying these techniques to practical control problems in a wide range of application domains.


The proposed research will significantly advance the state-of-the-art for control of systems with saturating actuators. Because saturation is, perhaps, the most common type of nonlinearity encountered in modern control systems, the benefits of the research will be widely applicable to a variety of areas, including reconfigurable flight control. It is hoped that the research will ultimately lead to global robust control in the presence of unmatched uncertainties and disturbances. Additionally, there are currently no software products on the market that can assist with the design and analysis of controllers for systems subject to saturation nonlinearities. The proposed prototype MATLAB toolkit will benefit engineers in disciplines ranging from aerospace to chemical process control by facilitating design of improved controllers with known stability properties for systems with saturating actuators.


David G. Ward
Barron Associates, Inc.
1160 Pepsi Place, Suite 300
Charlottesville , VA 22901


Barron Associates, Inc.
1160 Pepsi Place, Suite 300
Charlottesville , VA 22901-0807