High Performance Aircraft Controls Research
Point of Contact: Patrick C. Murphy
Objective and Strategy The overall objective of the DSCB High Performance Aircraft (HPA) team is to develop practical aircraft control law design techniques that push the state-of-the-art for advanced airframes. The strategy for meeting this objective is to pursue three research thrusts: (1) Reconfigurable Controls, (2) Advanced Controls, and (3) Modeling & System Identification. These thrusts are tightly linked since the research is focused on a common advanced experimental vehicle and a common overall objective.
Important technical areas, such as flying qualities, PIO analysis, and nonlinear controls, are not highlighted as primary research thrusts. These technical areas are recognized as very important, but cannot be pursued as independent research thrusts, due to limited resources. However, the team recognizes that capability in these areas is required and state-of-the-art knowledge must be maintained to allow appropriate application to control designs for advanced high performance airframes. As new research problems are defined that require expertise in these areas the HPA team will adapt its program to emphasize the appropriate technical areas.
Advanced-configuration high-performance aircraft with innovative control effectors will pose problems for flight control systems that have not been common on previous aircraft. For example, these aircraft probably will have highly redundant control effectors, may not have vertical tails, will be stealthy, and will operate over extended flight regimes with highly nonlinear aerodynamics. Uninhabited vehicles may be capable of very high-g maneuvers with large attitude rates. Survivability and life-cycle cost will be driving factors in the designs.
In this environment new modeling and system ID techniques may be required. Redundant controls will require advances in control allocation and at the same time will permit utilization of reconfigurable control systems which can detect a control effector failure and use a redundant effector instead. New linear design techniques with advances in gain scheduling or even nonlinear techniques may be required to allow efficacious control design in the presence of nonlinearities.
The challenge is to identify and characterize the control problems presented by advanced aircraft and to develop controls technologies to solve those problems.
The research needs for advanced configurations using innovative control effectors and sensors represent a significant development in technology for high performance aircraft. To meet these needs, three research thrusts were developed by the HPA team. These research thrusts are linked by a common objective and a common experimental vehicle to focus the technology. A central research thrust in the HPA research plan is Reconfigurable Controls. Under the Reconfigurable Controls thrust, technologies will be developed to allow design and implementation of a reconfigurable control system that will perform automatic, on-line optimization of aircraft performance in the event of damage or system failures. This thrust focuses attention on on-line identification, failure detection and isolation, and on-line control re-design. This technology should immediately improve survivability and safety of any aircraft. Complementing the Reconfigurable Controls thrust, the Advanced Controls thrust maintains a broader view by seeking an appropriate mix of control strategies for advanced aircraft. Technologies will be developed to provide proven, practical control design methodologies that can be applied to advanced high performance aircraft. Research in this thrust is performed with an interest in supporting development of technologies in the Reconfigurable Controls thrust and allow development of controls technologies that may not initially fit under the definition of reconfigurable controls. The System ID & Modeling thrust develops techniques for creating high fidelity mathematical models that will support the other two thrusts. Through these three thrusts the HPA team seeks to develop the requisite flight controls technologies that will impact the performance, efficiency/costs, and survivability of future advanced high-performance aircraft. Moreover, some of these same technologies will benefit future transports, both civil and military.