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Aircraft Energy Management


OBJECTIVE: Demonstrate a subsystem control methodology to optimize aircraft power generation, distribution, utilization, and associated thermal management based upon potential tactical vehicle operational power requirements and environmental conditions. DESCRIPTION: The Integrated Vehicle Energy Technologies (INVENT) program was initiated to demonstrate the use of adaptive subsystems (robust electrical power system, adaptive power and thermal management, and high performance electric actuation) to optimize use of energy by advanced more-electric airframes across multiple mission segments. It is anticipated that this energy optimization approach can result in considerable reductions in parasitic fuel burn compared to the traditional stressing case approach used in traditional military aircraft design while ensuring that the aircraft meets performance requirements over the entire mach/altitude mission envelope. In order to accomplish these goals, it is essential that multiple vehicle systems be designed and operated in an integrated framework allowing for dynamic and on-demand energy utilization based upon varying vehicle demands. A major challenge to the implementation of adaptive aircraft subsystems is development of a robust vehicle-level control system. This master control system must monitor the overall energy use of the platform and dictate control recommendations to the lower-level subsystems necessary to maximize range based upon specific operational demands required from the aircraft (e.g., best altitude/best mach, combat-specific operations, etc.). Successful control strategies require an objective function that allows for variations based upon changing mission requirements such that energy optimization can still occur in a local environment which may be suboptimal compared to ideal mission conditions. Additionally, stressing mission cases such as the use of high energy, low-duty cycle peripherals or sustained supersonic, low-altitude operations must be accommodated. To minimize total mission energy usage for given sets of potential missions, the energy management unit must passively attempt to determine the anticipated performance desirements based upon instantaneous flight conditions. Using a known set of subsystem needs based upon the energy manager"s best guess of the pilot's desired operational mode (max range, max performance, etc), the vehicle energy manager must use its time-dependent value function to prescribe a given set of performance objectives to individual subsystems. This energy manager would then seek to minimize the energy consumption within this set of objectives and recurse in a time-step consistent with the response capability of the subsystems. It is understood that while total energy or fuel burn would be the primary value function driver, other factors such as thermal and power system capacity management, electrical power quality, subsystem priority, or other specialty considerations must be considered. A significant consideration in the development of this vehicle energy management unit relates not only to the mathematical construct of this value function, but also to the individual mathematical relationships to each subsystem. It is anticipated that each energy management/subsystem relationship may require a different mathematical construct e.g. analytical, statistical/Boltzmann, rules-based, etc. Regardless, the complexity of these mathematically interdependent relationships present considerable challenges not only to the design of potential aircraft electrical and thermal architectures, but also to the control of each of these systems. While it is understood that insufficient data is available to explicitly define these relationships, the type of mathematics expected to be used and any associated control parameters must be established based upon the relative differences in the subsystem"s time constants, gain, and relative priority. PHASE I: Demonstrate the feasibility of an energy optimization approach to develop a control methodology of a representative tactical fighter architecture allowing dynamic operation of pertinent systems with the intent of maximizing range. Demonstrate specific mathematic relationships between vehicle systems which allow for dynamic optimization of performance and assess system performance benefits. PHASE II: Utilizing either Government-provided or commercially-obtained subsystem and component dynamic toolsets, apply the control system developed under the Phase I to explore system configurations which can demonstrate improved performance against an established benchmark aircraft configuration. Perform some level of validation of this integrated modeling environment using available data sources. Provide an enhanced aircraft subsystem and control suite demonstrating viability of the control approach. PHASE III: Phase III objectives include application of the developed control approach to a next generation tactical fighter, advanced mobility, or related platforms. Commercial applications include more electric aircraft and hybrid-electric automobiles. REFERENCES: 1. K.J. Karimi, Future Aircraft Power Systems-Integration Challenges, Senior Technical Fellow, Carnegie Mellon University Press, 2007. 2. Swain, E.F.,"Aircraft Avionics Cooling,"Present And Future, Aerospace and Electronics Conference, 1998. NAECON 1998. Proceedings of the IEEE 1998 National Aerospace and Electronics Conference. 3. J. Lescot and A. Sciarretta,"On the integration of optimal energy management and thermal management of hybrid electric vehicles,"Vehicle Power and Propulsion Conference (VPPC), 2010 IEEE , Vol., No., pp.1-6, September 1-3, 2010.
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