Parameter-Adaptive Model-Following for In-Flight Simulation

Abstract

In-flight simulat.ions are normally accomplished by using control laws which depend on accurate knowledge of the stability derivatives of the host aircraft. Degraded performance may result if the stability derivatives deviate considerably from their presumed values. Gain scheduling can compensate for parameter variations, but this form of open-loop compensation m y require extensive flight testing f o r fine tuning. This paper implements an adaptIve mntrol law to compensate for changing aircraft parameters. The step-response matrix required by 'the control law 1s identified recursively using a recently developed technique which does not requ'ire special "test" signals and which discounts old data depending on the input excitation detected. Tracking fidelity i s maintained despite parameter changes. The control design package MATRIXx is used to test the adapttve system. The performance of the resulting system i s excel lent and demonstrates the relative advantages of adaptive controlliers for in-flight simulation. I m O D u m o NAn in-flight simulator is an aircraft whose stability, feel, ancl flying characteristics can be changed to match those of another aircraft. As the pilot moves the controls, he experiences the flight motions and handling qualities of the simulated aircraft [ 13. In-f'l ight simulators are essential tools in the research and development process that provide the capabiltty to realistically and safely evaluate new or inodified aircraft and weapon systems before first-flight and before committing to production [23. They have been used in many types of generic research, especially handling qualities, and for several types of specialized training, particularly at the A i r Force and Navy Test Pilot Schools.Emerging aircraft concepts are projected to Provide substantially improved performance and simulation capabllfties, A new in-flight simulator 8. Hagglund, T., I' New Estimation Techniques for Adaptive Control," PhO Dissertation, Report LUrrO2/(~T-l025)/1-120/(