Civilian Tilt Rotor

Adaptive Nonlinear Control of a Civilian Tiltrotor

Aircraft flight control design has been dominated by classical control techniques. While this tradition has produced many highly reliable and effective control systems, recent years have seen a growing interest in applications of robust, nonlinear, and adaptive control theory. This development has been motivated in part by new possibilities offered by Active Control Technology (ACT). ACT applications include ‘fly-by-wire’ and ‘fly-bylight’ technologies, which create opportunities for new concepts in aircraft design. Some examples are low-observable and supermaneuverable tailless fighter aircraft, and aircraft capable of flight in multiple configurations. Next generation aircraft using ACT may differ even more radically from their conventional predecessors, presenting control designers with avariety of unprecedented challenges.Examples include remotely piloted and autonomous vehicles, which need not be constrained by physical limitations imposed by a human operator on board.

The desire for enhanced agility and functionality demands that the aircraft perform over an increased range of operating conditions characterized by dramatic variations in dynamic pressure and nonlinear aerodynamic phenomena. Furthermore, the use of nonlinear actuation systems increases the complexity of the control design. Therefore, there is presently a strong interest in the development of real-time adaptive control methods that are applicable to flight control problems where the aircraft characteristics are poorly understood or are rapidly changing. In high angle-of-attack (AoA) flight, the aerodynamics are poorly understood and expensive to model. Alternately, variation in dynamic response may occur due to battle damage or component failure, requiring rapid on-line reconfiguration of the control system to maintain stable flight and reasonable levels of handling qualities.

Traditional flight control designs involve linearizing the vehicle dynamics about several operating conditions throughout the flight envelope, designing linear controllers for each condition, and blending these point designs with an interpolation scheme. This ‘gain-scheduling’ approach, which tends to be rather tedious, may produce a control law that does not globally possess the desirable properties exhibited locally by its constituent point designs. Although gain-scheduling has historically proven successful in a variety of applications, future designs will benefit from more advanced methods which explicitly account for the intrinsic nonlinearities of the system.

Publications

Journal Articles

  1. Robust nonlinear adaptive flight control for consistent handling qualitiesRolf T. Rysdyk, Anthony J. CaliseIEEE Transactions on Control Systems Technology, 13(6): Robust nonlinear ad, November, 2005rysdyk:itcst:2005Keywords: adaptive control, tiltrotor
  2. Nonlinear adaptive flight control using neural networksAnthony J. Calise, Rolf T. RysdykIEEE Control Systems Magazine, 18(6):14 - 25 , December, 1998calise:csm:1998Keywords: adaptive control, tiltrotor

Conference Papers

  1. Robust adaptive control using single-hidden-layer feedforward neural networksMichael B. McFarland, Rolf T. Rysdyk, Anthony J. CaliseAmerican Control Conference, San Diego, CA, June, 1999mcfarland:acc:1999Keywords: adaptive control
  2. Robust adaptive nonlinear flight control applications using neural networksRolf T. Rysdyk, Flavio Nardi, Anthony J. CaliseAmerican Control Conference, San Diego, CA, June, 1999rysdyk:acc:1999
  3. Adaptive nonlinear control for tiltrotor aircraftRolf T. Rysdyk, Anthony J. CaliseIEEE International Conference on Control Applications , Trieste, Italy, September, 1998rysdyk:ica:1998Keywords: adaptive control, tiltrotor

Theses

  1. Adaptive Nonlinear Flight ControlRolf T. RysdykGeorgia Institute of Technology, 270 Ferst Drive, Atlanta GA 30332, U.S.A., November, 1998rysdyk:phdKeywords: adaptive control, tiltrotor