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Plug-and-Play Technology for Distributed Modular Propulsion Engine Controls Design

Description:

TECHNOLOGY AREA(S): Air Platform 

OBJECTIVE: To provide architectures that enable propulsion systems upgrade/change with minimal cost and effort. To design modular, and self-adapting architectures to link new and legacy propulsion systems. 

DESCRIPTION: A propulsion system consists of a source of mechanical power, and a propulsor (means of converting this power into propulsive force). When it comes to integrated propulsion systems, there's lot of work that goes into power plant and propulsor matching on a performance level, before control ever gets involved. Hence the idea of core and prop/fan modules as separate elements that could be swapped around with a plug-and-play (PnP) system would be an efficient technology. Adaptive and peak-seeking control tools integrated in a decentralized architecture could enable PnP development of entire families of propulsion systems. The research includes the software and hardware aspects of the PnP technology development for propulsion systems. In the futuristic engine control vision, engine cores and props/fans could be purchased with their onboard subordinate controllers ready for integration into a functional propulsion system, whereas the FADEC was developed independently for the integrated engine. When it comes to integrated propulsion systems, there's lot of work that goes into power plant and propulsor matching on a performance level, before control ever gets involved. Hence the idea of core and prop/fan modules as separate elements that could be swapped around with a plug and play system would be an efficient technology. Helicopters and other VTOL aircraft systems might be good candidates though, since in those cases one could consider the core power plant as a swappable module. A given helicopter with a given set of rotor blades could be made to work with various Original Engine Manufacturers (OEMs) Furthermore, the PnP technology can be implemented in automobile and marine propulsion systems. The design approach would eliminate control interfaces compatibility issues. Commercial manufacturers of gas turbine engines rarely design all new engine centerlines; the lifespan of successful engine families is decades. Many of the new engines designed in a family are based on an existing engine core, primarily due to cost and reliability concerns. The high-pressure compressor and turbine contain the highest performance, and therefore most expensive, components. Engine core designs may move from military turbojets into commercial turbo-fans and turbo-props. A similar niche is occurring in UAV development, where small gas turbines are being used to power a variety of different lift/thrust devices. UAV development programs rarely have the resources for serious engine redevelopment and therefore must select from a limited number of commercial off the shelf (COTS) engines. In the case of small gas turbines these COTS engines are generally designed for missile turbojet or power generator applications, while the UAV designer may want to use the engine core in a turbo-prop or turbofan application. Successful development of decentralized adaptive control for this class of engines would allow UAV designers to purchase engines with onboard controllers and mate them with their own proprietary fan/prop sections without having to design a new control system from scratch. For propulsion system PnP technology development, adaptive and peak-seeking control techniques can be used. Adaptive control, for fuel regulation, and a self-tuning controller, for prop/fan angle regulation, integrated in a decentralized control architecture is the general structure of this PnP technology. Using this technology, the propulsion system fan/prop with its subordinate controller can be plugged in to the various propulsion system cores with their own subordinate controllers, which also include the supervisory controller, and vice versa. With the aid of this technique, different engine cores can be matched to different props/fans, and the whole propulsion system should work without any more performance tuning. For example, in geared turbofan engine systems, physical separation of core and propulsor provides an alternative to the geared fan architecture by enabling the integration of variable pitch fans in the geared turbofan engines using PnP technology. The plug and play technology can be applied for legacy as well as new engine design. Any changes in sensors, actuators, or software in this system should be considered as a part of the modular design. For example, using existing hardware with new hardware with minimum changes in the software. Appropriate embedded system design is also a part of the PnP technology development. This PnP technology has the potential to optimize the software/hardware integration for legacy and new generation turbine engines. New design approaches are needed in unmanned aerial vehicle (UAV) development, where small gas turbines are being used to power a variety of different lift/thrust devices. UAV development programs rarely have the resources for serious engine redevelopment and therefore must select from a limited number of commercial off the shelf (COTS) engines. In the case of small gas turbines, these COTS engines are generally designed for missile-turbojet or power generator applications, while the UAV designer may want to use the engine core in a turbo-prop or turbofan application. Successful development of PnP technology for this class of engines would allow UAV designers to purchase engines with onboard controllers and mate them with their own proprietary fan/prop sections without having to design a new control system from scratch. Some of the potential examples of propulsion systems for PnP technology application are presented here. In a UAV which has a few different propulsion systems in which they have had to integrate commercial power systems into the overall propulsor, either using one fan or several fans. Another application is a UAV which has an engine attached to a lift fan; the fan is fixed pitch and the motor is internal combustion, but a turbine application would require the incorporation of a variable pitch fan system. Another example could be the Pratt and Whitney (P&W) pure power geared turbofan engines which have been developed recently. The current versions of the engines utilize fixed pitch fans, but PnP technology can enable the integration of variable pitch fans in P&W geared turbofan engines. Gas turbine engine technology is a core element of many naval operations, including airborne assets and vessels relying on gas turbine propulsion technology. This plug and play technology could optimize the software/hardware integration for legacy and new generation turbine engines. Structuring engine control in a modular fashion using PnP technology would increase compatibility between different engine manufacturers and reduce development time and cost for new engines. PnP engine control technology also offers the potential of reduced engine weight, complexity, and maintenance needs, it also increases the flexibility in engine control systems. In addition, this architecture increases the reconfigurability/upgradability of propulsion systems where the data-bus, individual sensors and actuators, as well as computers, can be replaced and, possibly, updated, without forcing the disassembly/re-assembly of many engine components. 

PHASE I: Conceptual development of the PnP technology which includes the decentralized adaptive controller with a self-tuning control loop to be used for engine core and fan/prop subsystems and numerical simulation of this technology for a small turbofan engine. This stage is mostly focused on the software and simulation aspect of PnP technology development. 

PHASE II: The outcome of the first task would then be validated on a representative turbine engine, by investigating the necessary hardware and implementing the developed PnP technology. Based on the results of this experiment, update the controller architectures as necessary. Working with turbine engine manufacturers is encouraged. 

PHASE III: Integrate the outcomes of the Phase I and II tasks in a finalized software and hardware platform and develop it as a PnP technology for modular propulsion systems. This technology can be tailored for any propulsion system in manned or unmanned aircraft such as gas turbine, hybrid-electric engine, or piston engine specifically. 

REFERENCES: 

1. Distributed Engine Control Working Group DECWG), "Transition in Gas Turbine Engine Control Systems Architecture: Modular, Distributed, Embedded," NASA Propulsion Controls and Diagnostics Workshop, Dec. 8-10, 2009.; 2. United States Air Force Chief Scientist, "Technology Horizons: A Vision for Air Force Science and Technology," AF/ST-TR-10-01-PR, Volume 1, May 2010.; 3. M. Pakmehr, “Towards Verifiable Adaptive Control of Gas Turbine Engines,” Chapter V: Plug and Play Technology Concept for Gas Turbine Engine Control System, Ph.D. Thesis, Georgia Institute of Technology, May 2013.; 4. J. Bendtsen, K. Trangbaek and J. Stoustrup, "Plug-and-Play Control—Modifying Control Systems Online," in IEEE Transactions on Control Systems Technology, Vol. 21, No. 1, pp. 79-93, January 2013.

KEYWORDS: Plug-and-Play (PnP), Modular Design, Decentralized Control Architecture, Adaptive Control, Turbine Engine, Propulsion Systems, Online Control Tuning, Reconfigurable System 

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