A novel flight controller developed at Illinois may help reduce aircraft failures
At the end of February, CSL Prof. Naira Hovakimyan (MechSE) and her research team will travel to Edwards Air Force Base in Southern California to support flight testing of a Learjet augmented with an L1 adaptive flight control law. It will be the first time an L1 adaptive system is tested in flight on a manned aircraft -- in this case, a Learjet.
"It represents an important step towards the introduction of this technology into commercial aviation," Hovakimyan said. "The goal of this collaboration is to build trust in L1 adaptive control and provide evidence for certification of this technology."
The main objective of the study is to investigate the ability of L1 adaptive control to maintain nominal aircraft handling qualities and prevent unfavorable aircraft-pilot interactions in the presence of aircraft failures (changes in the aerodynamics, loss of control effectiveness, coupling between control channels, shifts in the center of gravity, etc). Testing will consist of one week of ground checks, followed by two weeks of extensive flight testing. In-flight testing will primarily focus on handling-qualities assessment for various tasks, including capture and offset-to-landing tasks, as well as analyzing the robustness margins of the L1 controller in terms of gain and time-delay margins.
The trials will be led by the USAF Test Pilot School (TPS) and will use Calspan’s variable stability Learjet. This aircraft implements a variable stability system (VSS) that is able to emulate changes in aircraft aerodynamics through the use of feedback loops, which are opaque to the flight control law. A total of 16 VSS configurations will be tested, with various severity levels per configuration. The tests will be performed by F-16 and B-52 pilots. Over the past several months, Hovakimyan's lab has been closely collaborating with Calspan to implement the L1 control law on the aircraft computers, and with the TPS to define the flight test plan.
These flight tests are a natural continuation of the tests performed by NASA Langley on the AirSTAR dynamically scaled Generic Transport Model research aircraft during 2009-2011 and the piloted simulation evaluations conducted by TUDelft on the SIMONA motion-based research simulator in 2011.