Distributed Engine Control
Due to environmental and structural constraints, control systems in engines typically have a centralized framework: the controller (FADEC) is attached to the engine through a casing that protects it from the high temperatures produced during operation and is connected to each sensor or actuator through a series of wires. These wires, which transmit analog information between the transducers and FADEC, contribute to the overall weight of the engine, and the engine design must take into consideration the effects of the harness routing on the weight distribution. A distributed control system would remove some of the responsibility of the FADEC and place it “on-chip” to form a smart transducer. In particular, the signal conditioning and conversion from analog to digital would be done “locally” (rather than in a centralized location); these digital signals may then be transmitted to a centralized location for control calculations, or may be used in local loop closure algorithms to reduce or remove the need for a centralized FADEC. This may result in less weight contribution to the overall engine from the control system.
In addition to the physical design constraints placed on the controller hardware, the overall engine design process does not involve control design until late in the process, leaving little room for introducing new hardware or control techniques. The distributed engine control task is not only concerned with the design of a decentralized control scheme using smart transducers, but also in developing a hardware-in-the-loop (HIL) system that can be used to test new control algorithms with new hardware, such as smart sensors that can operate in high-temperature environments. This will allow for control design to take place earlier in the overall design process, as it is only necessary to have a computational model of the engine for simulation. The control algorithm will first be implemented as a simulation containing numerical models of the smart transducers, then, these numerical models will be replaced with actual hardware to test the response of the engine under various operating conditions. The HIL system will help advance not only control design, but also transducer technology, as it will allow for in-the-loop testing of hardware in an environment separate from the physical engine, avoiding the risks inherent when running ground tests of a closed-loop.
- Mathematical Modeling of Aerospace Components and System Performance