Real-Time Structural Overload Control via Control Allocation Optimization

Optimal Control Allocation for Active Load Suppression (OCAALS) is an optimal control surface allocation technique that employs real-time measurements to actively respond to and protect against damage due to structural overload. The technique utilizes load feedback to determine when a structural element is approaching its load limit. The innovation then shifts loading away from the affected element to prevent structural overload and maintain performance. The impact of this flight-tested technology is potentially significant for aircraft, rockets, and industrial robotics, as it will enable designs that do not require excessive structural margins to account for unexpected maneuver loads and damage tolerance. This optimal control surface allocation technique employs real-time measurements to actively respond to and protect against damage due to structural overload. The technique utilizes load feedback to determine when a structural element is approaching its load limit. The innovation then shifts loading away from the affected element to prevent structural overload and maintain performance. The impact of this flight-tested technology is potentially significant for aircraft, rockets, and industrial robotics, as it will enable designs that do not require excessive structural margins to account for unexpected maneuver loads and damage tolerance. Work to date: Using NASA's Full-Scale Advanced Systems Testbed (FAST) aircraft, the Armstrong team designed and carried out a three-flight experiment to test the effectiveness of an optimal control allocator with strain gauge feedback to study control and load allocation. The experiment successfully demonstrated that the technology will actively limit measured aileron hinge moments and reallocate the pilot-commanded body rates to other control surfaces, such as trailing-edge flaps and stabilators. The technique limited the imparted aileron loads but still provided pilots with the commanded vehicle response. Armstrong has filed a provisional patent for the technology. Looking ahead: The Armstrong team received a Phase I Seedling Fund award from NASA's Aeronautics Research Mission Directorate (ARMD) to further mature the technology in 2015. Future tests will employ more advanced and unique sensor technologies that will improve both the robustness of the approach as well as the ability to measure the load throughout the vehicle structure. This technology could open the door to truly novel approaches to vehicle and control system design. Benefits Effective: Identifies the optimum control surface usage for a given maneuver for both performance and structural loading Efficient: Enables lighter weight aircraft structures Automated: Monitors and adapts to numerous damage scenarios in real time Economical: Decreases the need for repairs and general maintenance Safe: Increases aircraft robustness in control-loss scenarios Applications Jet aircraft Rocket controls Industrial robotics Structural health monitoring and load alleviation More »