On August 5th, 2010, a team consisting of members of NASA Ames Diagnostic & Prognostic Group and U.S. Army Aero Flight Dynamics Directorate (AFDD) personnel successfully conducted the first test flight of the Flyable Electro-mechanical Actuator (FLEA) testbed on a UH-60 Black Hawk helicopter. This accomplishment was a result of close collaboration between the two organizations over a period of eighteen months.
The flight achieved a series of objectives: an electro-magnetic compatibility/interference test, a communication checkout, and a data collection of both nominal and fault-injected test actuators. The injected fault for this flight was spall — damage of the mechanical components of the actuator due to repeated metal-on-metal contact. For the purposes of this experiment, individual spalls were introduced onto the second test actuator screw surface via a precise electro-static discharge machining process. The injection of the fault was performed during the flight by switching the load path from the nominal actuator to the faulty actuator via remote command.
All subsystems of the FLEA operated as planned. The testbed executed rigorous motion sequences, matching those of the target UH-60 actuator (forward primary servo, an actuator responsible for pitch control of the main rotor blades). Dynamic load profiles executed by the FLEA’s load actuator were derived using flight conditions information (obtained from the aircraft data bus), as well as from some of the models developed by NASA’s Subsonic Rotary Wing Project under the Aeronautics Research Mission Directorate. Data collected during the flight is currently being analyzed for tuning of the diagnostic and prognostic algorithms. More test flights are to follow in September with further improvements to the FLEA’s sensor suit and software.
BACKGROUND: Electro-Mechanical Actuators (EMA) are gradually replacing more traditional hydraulic actuators in the new generation of fly-by-wire aircraft and spacecraft. Their more extensive adoption, however, is being hindered by lack of performance data in relevant environments and uncertainty on whether some of the more critical fault modes can be detected and mitigated fast enough to ensure flight safety. The objective of this work is to develop prognostic health management algorithms that help to alleviate this concern.
In order to validate such algorithms, an EMA test stand has been designed and built through a partnership between NASA Ames and California Polytechnic State University that, unlike current laboratory stands typically weighing thousands of pounds, is portable enough to be placed aboard a wide variety of aircraft. The stand allows testing of EMA health management technologies in realistic flight environments, thus substantially increasing their Technology Readiness Level (TRL) — all without the expense of dedicated flights, as the stand is designed to function as a non-intrusive secondary payload. No aircraft modifications are required and experiments can be performed during any available flight opportunity: pilot proficiency flights, ferry flights, or flights dedicated to other projects. Motion and load profiles are derived from the corresponding real-time values for one of the aircraft’s control surfaces (by interfacing with the aircraft data bus). Experimental faults are injected into the system by quickly switching profile execution from a nominal test actuator to a faulty actuator via an electro-magnetic coupling mechanism.
NASA PROGRAM FUNDING: Integrated Vehicle Health Management (IVHM) program
TEAM: Edward Balaban, Kai Goebel, Sriram Narasimhan, Ann Patterson-Hine, Indranil Roychoudhury, Abhinav Saxena, and personnel of the US Army Aero Flight Dynamics Directorate
COLLABORATORS: California State Polytechnic University: Sarah Harding, Frank Owen, Michael Koopmans (now Oregon State University), Austin Lawrence, Catlin Mattheis (Oregon State University), and Irem Tumer
Contact: Edward Balaban