CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to United States Provisional Application No. 61706853, which was filed on 28 September 2012, and to United States Provisional Application No. 61706383, which was filed on 27 September 2012. Both of these provisional applications are incorporated herein by reference.

BACKGROUND

[0002] This disclosure is directed toward a control system and, more particularly, to a turbomachine control system involving a Full Authority Digital Electronic Controller (FADEC).

[0003] Turbomachines, such as gas turbine engines, typically include a fan section, a compression section, a combustion section, and a turbine section. Turbomachines may employ a geared architecture connecting portions of the compression section to the fan section.

[0004] Some turbomachines are used to propel aircraft. Aircraft, as well as other vehicles, may utilize FADECs to control operation of the turbomachines. Traditional subsystem control arrangements in aerospace applications utilize FADECs to directly control an actuator. Other subsystem control arrangements in the prior art may include components having their own control and supporting electronics. Still other subsystem control arrangements are distributed control systems that utilize a digital bus. In such systems, a bus failure or controller failure can lead to an engine shut down condition due to the lack of feedback from the controlling and supporting electronics to the FADEC.

[0005] A flow of a prior art distributed control system is shown in Figure 1. The prior art system includes a FADEC 2, an actuator 4, and an effector 6. A variable vane is an example type of effector 6. When moving the effector 6 is desired, a request 8 is sent to the FADEC 2, which then sends a current-based signal to the actuator 4. The current-based signal may be an alternating current or a direct current. The actuator 4 responds to the current-based signal and moves the effector 6. Information about the effector 6 movement may be communicated back to the FADEC 2 along a path 10. Due to the current-based signal moving from the FADEC 2 to the actuator 4, direct communications from the actuator 4 to the FADEC 2 would require additional wiring, which undesirably adds weight and complexity to the system.

SUMMARY

[0006] A turbomachine control system according to an exemplary aspect of the present disclosure includes, among other things, a Full Authority Digital Electronic Controller and an actuator. The actuator is configured to adjust an effector in response to a command signal communicated from the Full Authority Digital Electronic Controller to the actuator along a communication path that is bidirectional.

[0007] In a further non- limiting embodiment of the foregoing turbomachine control system, the communication path may comprise a bus.

[0008] In a further non- limiting embodiment of either of the foregoing turbomachine control systems, the communication path may comprise a CAN bus.

[0009] In a further non- limiting embodiment of any of the foregoing turbomachine control systems, the communication path may comprise no more than two wires.

[0010] In a further non- limiting embodiment of any of the foregoing turbomachine control systems, the communication path may comprise at least one wire used to both communicate the command signal from the Full Authority Digital Electronic

Controller to the actuator, and to communicate health information from the actuator to the Full Authority Digital Electronic Controller.

[0011] In a further non- limiting embodiment of any of the foregoing turbomachine control systems, the communication path may be configured to communicate health information directly from the actuator to the Full Authority Digital Electronic Controller.

[0012] In a further non- limiting embodiment of any of the foregoing turbomachine control systems, the communication path may extend between a first transmitter- receiver and second transmitter-receiver. The first transmitter-receiver may be inside the Full Authority Digital Electronic Controller. The second transmitter-receiver may be outside the Full Authority Digital Electronic Controller.

[0013] In a further non- limiting embodiment of any of the foregoing turbomachine control systems, the actuator may comprise a motor.

[0014] In a further non- limiting embodiment of any of the foregoing turbomachine control systems, the actuator may comprise a speed controller.

[0015] In a further non- limiting embodiment of any of the foregoing turbomachine control systems, the Full Authority Digital Electronic Controller may include an exterior housing and the actuator may be outside the exterior housing.

[0016] In a further non-limiting embodiment of any of the foregoing turbomachine control systems, the effector may comprise a variable area fan nozzle.

[0017] In a further non- limiting embodiment of any of the foregoing turbomachine control systems, the effector may be within a geared gas turbine engine.

[0018] In a further non- limiting embodiment of any of the foregoing turbomachine control systems, the communication path is a digital communication path.

[0019] A method of communication within a turbomachine control system according to another exemplary aspect of the present disclosure include, among other things, communicating a first digital signal along a communication path in a first direction, manipulating an actuator of the turbomachine subsystem in response to the digital signal, and communicating a second digital signal along the communication path in a second direction that is opposite the first direction.

[0020] In a further non- limiting embodiment of the foregoing method of communication, the second signal may comprise health information.

[0021] In a further non-limiting embodiment of either of the foregoing methods of communication, the method may include manipulating the actuator to adjust an effector. [0022] In a further non- limiting embodiment of any of the foregoing methods of communication, the communication path may extend from a Full Authority Digital Electronic Controller to the actuator that is separate from the Full Authority Digital Electronic Controller.

[0023] A turbomachine control system according to another exemplary aspect of the present disclosure includes, among other things, an actuator assembly configured to adjust an effector between a first state and a different, second state in response to a digital signal communicated to the actuator assembly along a communication path. The actuator assembly is further configured to send information along the

communication path.

[0024] In a further non- limiting embodiment of the foregoing turbomachine control system, the information may comprise actuator health information.

[0025] In a further non- limiting embodiment of either of the foregoing turbomachine control systems, the communication path may be operably coupled to a Full Authority Digital Electronic Controller.

DESCRIPTION OF THE FIGURES

[0026] The various features and advantages of the disclosed examples will become apparent to those skilled in the art from the detailed description. The figures that accompany the detailed description can be briefly described as follows:

[0027] Figure 1 shows a flow of a prior art control system.

[0028] Figure 2 shows a section view of an example turbomachine.

[0029] Figure 3 shows a perspective view of an example Full Authority Digital Electronic Controller utilized to control the turbomachine of Figure 2.

[0030] Figure 4 shows the flow of an example method of communication within a turbomachine control system.

[0031] Figure 5 shows an example schematic view of a hybrid distributed control system. DETAILED DESCRIPTION

[0032] Figure 2 schematically illustrates an example turbomachine, which is a gas turbine engine 20 in this example. The gas turbine engine 20 is a two-spool turbofan gas turbine engine that generally includes a fan section 22, a compression section 24, a combustion section 26, and a turbine section 28.

[0033] Although depicted as a two-spool turbofan gas turbine engine in the disclosed non-limiting embodiment, it should be understood that the concepts described herein are not limited to use with turbofans. That is, the teachings may be applied to other types of turbomachines and turbine engines including three-spool architectures. Further, the concepts described herein could be used in environments other than a turbomachine environment and in applications other than aerospace applications.

[0034] In the example engine 20, flow moves from the fan section 22 to a bypass flowpath. Flow from the bypass flowpath generates forward thrust. The compression section 24 drives air along a core flowpath. Compressed air from the compression section 24 communicates through the combustion section 26. The products of combustion expand through the turbine section 28.

[0035] The example engine 20 generally includes a low-speed spool 30 and a highspeed spool 32 mounted for rotation about an engine central axis A. The low-speed spool 30 and the high-speed spool 32 are rotatably supported by several bearing systems 38. It should be understood that various bearing systems 38 at various locations may alternatively, or additionally, be provided.

[0036] The low-speed spool 30 generally includes a shaft 40 that interconnects a fan 42, a low-pressure compressor 44, and a low-pressure turbine 46. The shaft 40 is connected to the fan 42 through a geared architecture 48 to drive the fan 42 at a lower speed than the low-speed spool 30.

[0037] The high-speed spool 32 includes a shaft 50 that interconnects a high-pressure compressor 52 and high-pressure turbine 54. [0038] The shaft 40 and the shaft 50 are concentric and rotate via bearing systems 38 about the engine central longitudinal axis A, which is collinear with the longitudinal axes of the shaft 40 and the shaft 50.

[0039] The combustion section 26 includes a circumferentially distributed array of combustors 56 generally arranged axially between the high-pressure compressor 52 and the high-pressure turbine 54.

[0040] In some non-limiting examples, the engine 20 is a high-bypass geared aircraft engine. In a further example, the engine 20 bypass ratio is greater than about six (6 to 1).

[0041] The geared architecture 48 of the example engine 20 includes an epicyclic gear train, such as a planetary gear system or other gear system. The example epicyclic gear train has a gear reduction ratio of greater than about 2.3 (2.3 to 1).

[0042] The low-pressure turbine 46 pressure ratio is pressure measured prior to inlet of low-pressure turbine 46 as related to the pressure at the outlet of the low-pressure turbine 46 prior to an exhaust nozzle of the engine 20. In one non- limiting embodiment, the bypass ratio of the engine 20 is greater than about ten (10 to 1), the fan diameter is significantly larger than that of the low-pressure compressor 44, and the low-pressure turbine 46 has a pressure ratio that is greater than about 5 (5 to 1). The geared architecture 48 of this embodiment is an epicyclic gear train with a gear reduction ratio of greater than about 2.5 (2.5 to 1). It should be understood, however, that the above parameters are only exemplary of one embodiment of a geared architecture engine and that the present disclosure is applicable to other gas turbine engines including direct drive turbofans.

[0043] In this embodiment of the example engine 20, a significant amount of thrust is provided by the bypass flow B due to the high bypass ratio. The fan section 22 of the engine 20 is designed for a particular flight condition— typically cruise at about 0.8 Mach and about 35,000 feet. This flight condition, with the engine 20 at its best fuel consumption, is also known as "Bucket Cruise" Thrust Specific Fuel Consumption (TSFC). TSFC is an industry standard parameter of fuel consumption per unit of thrust.

[0044] Fan Pressure Ratio is the pressure ratio across a blade of the fan section 22 without the use of a Fan Exit Guide Vane system. The low Fan Pressure Ratio according to one non- limiting embodiment of the example engine 20 is less than 1.45 (1.45 to 1).

[0045] "Low Corrected Fan Tip Speed" is the actual fan tip speed in ft/sec divided by an industry standard temperature correction of [(Tram °R) / (518.7 °R)] ^A 0.5. The Temperature represents the ambient temperature in degrees Rankine. The Low Corrected Fan Tip Speed according to one non-limiting embodiment of the example engine 20 is less than about 1150 fps (351 m/s).

[0046] The engine 20 includes a Full Authority Digital Electronic Controller (FADEC) 62 that is used to control various features of the engine 20. In this example, the FADEC 62 is housed within a nacelle 64 of the engine 20. The nacelle 64 provides an outer boundary of a bypass flowpath.

[0047] At an aft end of the nacelle 64, a variable area fan nozzle 66 concentrically or coaxially surrounds core portions of the engine 20 to define a variable diameter nozzle through which bypass air B is discharged. The example variable area fan nozzle 66 includes flaps 68 that are moved by an actuator 70 between positions closer to the axis A and positions further from the axis A. The cross-sectional area available for flow discharge is changed by manipulating the positions of the flaps 68 using the actuator 70.

[0048] The flaps 68 are an example type of effector 72. Other example effectors are variable vanes of the, for example, compression section 24 of the engine 20. Bleed valves are another type of effector 72. The effector 72 essentially includes any component of the engine 20 that may be manipulated between a first state and a second state.

[0049] The FADEC 62 communicates signals to the actuator 70 to control the positioning of the flaps 68 of the variable area fan nozzle 66 and thus the effective area available for discharge. The actuator 70 in this example is motor. The position of the variable area fan nozzle 66 within the engine 20 and the associated packaging constraints may necessitate use of the motor as the actuator 70 rather than a hydraulic system, for example. A motor may fit within the packaging constraints of the engine 20 more effectively than a hydraulic system.

[0050] Referring now to Figures 3 and 4 with continuing reference to Figure 2, an example system 60 includes the FADEC 62, which communicates with the actuator 70 along a communication path 74. The example communication path 74 is digital communication path of a CAN bus. Other busses may be used in other examples.

[0051] The signals communicated from the FADEC 62 to the actuator 70 are digital signals. A transmitter/receiver 76 within the FADEC 62 and a transmitter/receiver 78 within the actuator 70 are utilized to operably couple the communication path 74 to the FADEC 62 and the actuator 70. The example communication path 74 is a bidirectional communication path meaning that the communication path 74 may be used to communicate information from the FADEC 62 to the actuator 70 and communicate information from the actuator 70 to the FADEC 62.

[0052] When changing the state of the flaps 68 is desired, a request 82 is sent to the FADEC 62. The request 82 may be pilot initiated or automatically initiated in response to a change in altitude, flight condition, etc. Other types of requests are also possible. The FADEC 62 interprets the request 82 and sends a command via the communication path 74 to the actuator 70. The flaps 68 are then moved by the actuator 70 in response to the command from the FADEC 62. The FADEC 62, due to the bidirectional communication path 74 is able to receive feedback directly from the actuator 70.

[0053] In the prior art, in part because signals from the FADEC to the actuator were current-based, the FADEC was unable to receive feedback directly from an actuator without incorporating additional architecture.

[0054] In the system 60, the communication path 74 may be include essentially only two wires, yet still provide communication from the actuator 70 to the FADEC 62. The system 60 thus includes a closed control loop between the FADEC 62 and the actuator 70, which may be particularly useful when the actuator 70 is associated with a safety critical system.

[0055] The system 60 also provides for feedback from the effector 72 to the FADEC 62 via the communication path 86 and the communication path 74. Such feedback may include measurements from position sensors.

[0056] Referring to Figure 5, an example hybrid distributed control system 100 suitable for use in the engine 20 (Figure 2), includes a FADEC 110, bus and driver electronics 120, actuators 124, and engine effectors 128. The FADEC 110 includes an engine control module 132 that uses engine control laws to determine a correct position for the actuators 124 and effectors 128. The module 132 communicates this information to respective actuator control loops 136 within the FADEC 110. The actuator control loops 136 then communicate the positional commands through a digital bus 140 to the bus and driver electronics 120 associated with the respective actuators 124 and engine effectors 128. The bus and driver electronics 120 may send analog commands along a path 148 to the actuators 124. The actuators 124 can manipulate a mechanical linkage 152 to change the position of the engine effectors 128. Feedback about the position of the engine effectors 128 is sent along analog feedback paths 156 to the FADEC 110.

[0057] Regarding the additional paths in Figure 5, path 160 represents a position request path, path 164 represents a loop closure path, and path 168 represents communications through the digital bus 140.

[0058] Features of the system 100 include a FADEC 110 that has visibility of the associated system in the event that the bus 140 fails. Another feature is that the relatively high powered bus and driver electronics 120 may be positioned away from the FADEC 110, which keeps the overall packaging of the system 100 smaller. The system 100 is highly scalable/upgradable, but still provides feedback for system, such as safety critical systems. [0059] Features of the disclosed examples include a control system providing an improved monitoring capability. Health of an actuator 70 may be directly monitored via the communication path between a FADEC and an actuator, for example. Another feature is the enhanced identification capability of faults due in part to the relatively direct two-way communication between the FADEC and the actuator. The FADEC may identify failures and disturbances in the actuator along the direct communication path as well as the effector along the communication path. The FADEC determines the position of the effector with relatively high accuracy. Another feature is utilizing relatively few wires to provide communication from the actuator to the FADEC.

[0060] The preceding description is exemplary rather than limiting in nature.

Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this disclosure. Thus, the scope of legal protection given to this disclosure can only be determined by studying the following claims.