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| Meeting | ACGS Committee Meeting 120 - Tukwila, WA - November 2017 | | Agenda Location | 4 GENERAL COMMITTEE TECHNICAL SESSION
4.2 Research Institutions, Industry, and University Reports
4.2.1 Research Institutions and Companies
4.2.1.3 D.K. Schmidt & Associates | | Title | D.K. Schmidt & Associates | | Presenter | Dave Schmidt | | Available Downloads* | presentation | | *Downloads are available to members who are logged in and either Active or attended this meeting. | | Abstract | An overview of a five-year NASA-funded project titled the “Performance Adaptive Aeroelastic Wing” (PAAW) is presented, followed by some recent results in the area of flight-dynamics and flutter suppression. This is a multi disciplinary, multiorganization project led by the UAV Lab at the University of Minnesota, with other team members consisting of STI, Virginia Tech, Aurora Flight Sciences, CMSoft, and Schmidt & Associates. The overall goal is to use structural flexibility to an advantage so as to actively optimize transport-aircraft wing shape over the flight envelope, minimizing fuel requirements. Aeroservoelastic modeling and active flutter suppression are key enabling technologies, novel methods such as MDAO are being applied, and extensive flight testing is being performed. Two different aircraft have been designed, developed, and are being flown as research test beds, all remotely piloted flexible flying-wing vehicles. Currently in the fourth project year, the first vehicle has been extensively flight tested, and the second vehicle is undergoing pre-flight ground testing. Due in large part to the fact that design and testing of flight hardware is a focus, the team is highly interactive and well coordinated.
The focus of this presentation is to report on the results from flight testing three flutter-suppression control systems, and on some aspects dealing with the validity of the mean-axis flight-dynamics modeling technique. Test results indicate that the three flutter suppression systems worked as designed and two significantly expanded the flutter boundary. The controller focused on in this talk was inspired be the concept of Identically Located Acceleration and Force (ILAF) put forth by John Wykes at Rockwell Corp in 1976. The ILAF concept led to the selection of the sensor/actuator pairing in the controller, which has an SISO architecture.
The mean-axis flight-dynamics modeling technique for modeling flexible aircraft typically makes the assumption that the inertia tensor is constant, and that the rigid-body and elastic degrees of freedom are inertially decoupled. Further detailed analysis of the vehicles under study have confirmed that these assumptions are valid to engineering accuracy. (Eigenvalues of the dynamic system are unaffected to three significant digits.) But the validity depends on vehicle geometry and flight condition. Hence, assessment of these assumptions is warranted in general. |
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