Tilt-rotor over-torque protection from asymmetric gust

A system includes a first mast torque transfer system, a second mast torque transfer system coupled to the first mast torque transfer system, and a torque limiting system. The torque limiting system includes a first sensor configured to determine a torque of the first mast torque transfer system, a second sensor configured to determine a torque of the second mast torque transfer system, and a processor configured to determine a differential torque between the torque of the first mast torque transfer system and the torque of the second mast torque transfer system and configured to control at least one of a torque input and a torque output to at least one of the first and second mast torque transfer systems as a function of the determined differential torque.

BACKGROUND

Field of the Invention

The present application relates to shaft driven systems. In particular, the present application relates to shaft driven systems associated with multiple rotors.

Description of Related Art

Some helicopters are configured as tiltrotor aircraft comprising multiple primary rotors. In some cases the rotors of the tiltrotor aircraft can be exposed to different environmental conditions, such as, but not limited to, asymmetrical gusts of wind. In cases where the rotors are connected to a shared gearbox, the gearbox, interconnecting shafts, and/or other rotor components can be exposed to torques in excess of working limits so that they require inspection, repair, and/or replacement.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring toFIG. 1, a tiltrotor aircraft10comprises a drive system12. The view of the aircraft10inFIG. 1is provided with some portions of the skin of the aircraft10removed to more clearly show portions of the drive system12. In addition to the drive system12, the aircraft10includes a fuselage14which carries at its rear end an empennage assembly16and at its forward end a crew cockpit18. Landing gear20,2222extend below the aircraft10. A portion of the drive system12extends through a wing assembly24that is connected to and extends transversely across the fuselage14. Fairings26,28blend the wing into the fuselage contour. The wing assembly24on each side of the fuselage14, is swept forward. The wing assembly24, as it extends outwardly from each side of the fuselage14, includes a dihedral angle. That is, the wing assembly24extends slightly upwardly toward the port wing tip30and the starboard wing tip32. Pivotally mounted on the port wing tip30is a port pylon assembly34that includes an engine36having an output shaft38that is connected to a reducing gearbox40. The gearbox40includes a propeller shaft42on which is mounted a port proprotor44. Gearbox40also includes a drive shaft46that extends downwardly into a bevel gear/pivot assembly48which serves as a pivot for the pylon34on the wing assembly24and also connects the drive shaft46with a shaft assembly50that extends across the wing24.

Similarly, a starboard pylon52is located adjacent the starboard wing tip32. The starboard pylon52includes an engine54having an engine output shaft56that extends into a gear reducer58. The gear reducer58includes an upwardly extending propeller shaft60which carries at its upper end a second or starboard proprotor62. The gear reducer58also includes a shaft64that extends downwardly into a bevel gear and pivot assembly66that is utilized to pivotally connect the starboard pylon52with the wing assembly24. The shaft assembly50extends across the wing assembly24of the aircraft10and has one end connected to the bevel gear and pivot assembly48at the port wing tip30. The other end of the shaft assembly50is connected with the bevel gear and pivot assembly66at the starboard wing tip32. The starboard engine54is connected to the starboard proprotor62through the engine output shaft56, the gear reducer58and the prop shaft60. The starboard engine54is also connected to the port proprotor44through the engine output shaft56, the gear reducer58, the drive shaft64, the bevel gear and pivot assembly and shaft assembly50. It will also be appreciated that the port engine36is similarly connected to both the port proprotor44and to the starboard proprotor62. As arranged, either engine can drive either proprotor or both proprotors and both engines operating simultaneously will drive both proprotors supplying appropriate power required to the proprotor needing the power as is required. Control system described below are provided to coordinate the speed of the engines36and54.

Referring now toFIG. 2, the drive system12is shown schematically. A main wing spar70provides support across the wing assembly24for a plurality of spaced bearings and the like to aid in supporting the shaft assembly50is also shown in phantom lines. The requirement for a plurality of bearings along the shaft assembly50is necessitated by the incremental construction of the shaft assembly50. The shaft assembly50has been divided into segments or increments for the purpose of accommodating the forward sweep of the wing assembly24as can be clearly seen inFIG. 2, to accommodate the wing dihedral angle which is not shown, and to accommodate the flexure of the wing assembly24during operation of the aircraft10. The number of increments illustrated inFIG. 2is not intended to be binding, but is shown only for purposes of illustration, the exact number of increments necessary will depend upon the amount of the sweep of the wing, the dihedral angle, also the amount of flexure in the wing assembly24. In any event, each increment or segment of the shaft assembly50is connected to the other so that the shaft assembly50rotates as a single unit. A pair of spaced structural wing ribs84and86are located in a mid-wing88portion of the wing assembly24. The ribs84and86generally coincide with the structural members of the fuselage14. Located in the mid-wing portion88aft of the main wing spar70is a mid-wing gearbox that is generally designated by the reference character90. Auxiliary shafts94and96from the bevel gear and pivot assemblies48and66, respectively. The auxiliary shafts94and96each drive, through appropriate gear mechanisms, generators98and100and hydraulic pumps102and104. In addition to the redundancy of the apparatus between the apparatus in the two pylons34and52, the previously mentioned mid-wing gearbox assembly90also provides additional generators, air compressors and hydraulic pumps.

The proprotor44and the drive system12components connecting proprotor44to the mid-wing gearbox assembly90can be referred to collectively as a first mast torque transfer system. The proprotor62and the drive system12components connecting proprotor62to the mid-wing gearbox assembly90can be referred to collectively as a second mast torque transfer system. The first mast torque transfer system comprises a sensor106configured to sense torque transmitted by one or more of the first mast torque transfer system components. The second mast torque transfer system comprises a sensor108configured to sense torque transmitted by one or more of the second mast torque transfer system components. Each of the sensors106,108can communicate with a general-purpose processor system300which is described in greater detail below.

FIG. 3illustrates a typical, general-purpose processor (e.g., electronic controller or computer) system300that includes a processing component310suitable for implementing one or more embodiments disclosed herein. In particular, the aircraft10may comprise one or more systems300. In addition to the processor310(which may be referred to as a central processor unit or CPU), the system300might include network connectivity devices320, random access memory (RAM)330, read only memory (ROM)340, secondary storage350, and input/output (I/O) devices360. In some cases, some of these components may not be present or may be combined in various combinations with one another or with other components not shown. These components might be located in a single physical entity or in more than one physical entity. Any actions described herein as being taken by the processor310might be taken by the processor310alone or by the processor310in conjunction with one or more components shown or not shown in the drawing. It will be appreciated that the data described herein can be stored in memory and/or in one or more databases.

The processor310executes instructions, codes, computer programs, or scripts that it might access from the network connectivity devices320, RAM330, ROM340, or secondary storage350(which might include various disk-based systems such as hard disk, floppy disk, optical disk, or other drive). While only one processor310is shown, multiple processors may be present. Thus, while instructions may be discussed as being executed by a processor, the instructions may be executed simultaneously, serially, or otherwise by one or multiple processors. The processor310may be implemented as one or more CPU chips.

The network connectivity devices320may take the form of modems, modem banks, Ethernet devices, universal serial bus (USB) interface devices, serial interfaces, token ring devices, fiber distributed data interface (FDDI) devices, wireless local area network (WLAN) devices, radio transceiver devices such as code division multiple access (CDMA) devices, global system for mobile communications (GSM) radio transceiver devices, worldwide interoperability for microwave access (WiMAX) devices, and/or other well-known devices for connecting to networks. These network connectivity devices320may enable the processor310to communicate with the Internet or one or more telecommunications networks or other networks from which the processor310might receive information or to which the processor310might output information.

The network connectivity devices320might also include one or more transceiver components325capable of transmitting and/or receiving data wirelessly in the form of electromagnetic waves, such as radio frequency signals or microwave frequency signals. Alternatively, the data may propagate in or on the surface of electrical conductors, in coaxial cables, in waveguides, in optical media such as optical fiber, or in other media. The transceiver component325might include separate receiving and transmitting units or a single transceiver. Information transmitted or received by the transceiver325may include data that has been processed by the processor310or instructions that are to be executed by processor310. Such information may be received from and outputted to a network in the form, for example, of a computer data baseband signal or signal embodied in a carrier wave. The data may be ordered according to different sequences as may be desirable for either processing or generating the data or transmitting or receiving the data. The baseband signal, the signal embedded in the carrier wave, or other types of signals currently used or hereafter developed may be referred to as the transmission medium and may be generated according to several methods well known to one skilled in the art.

The RAM330might be used to store volatile data and perhaps to store instructions that are executed by the processor310. The ROM340is a non-volatile memory device that typically has a smaller memory capacity than the memory capacity of the secondary storage350. ROM340might be used to store instructions and perhaps data that are read during execution of the instructions. Access to both RAM330and ROM340is typically faster than to secondary storage350. The secondary storage350is typically comprised of one or more disk drives or tape drives and might be used for non-volatile storage of data or as an over-flow data storage device if RAM330is not large enough to hold all working data. Secondary storage350may be used to store programs or instructions that are loaded into RAM330when such programs are selected for execution or information is needed.

The I/O devices360may include liquid crystal displays (LCDs), touch screen displays, keyboards, keypads, switches, dials, mice, track balls, voice recognizers, card readers, paper tape readers, printers, video monitors, transducers, sensors, or other well-known input or output devices. Also, the transceiver325might be considered to be a component of the I/O devices360instead of or in addition to being a component of the network connectivity devices320. Some or all of the I/O devices360may be substantially similar to various components disclosed herein.

During operation of the aircraft10, different amount of airflow in contact with proprotors44,62leads to different torque being transmitted through the first mast torque transfer system relative to the second mast torque transfer system. The inputs can be caused by environmental conditions, such as, but not limited to, wind gusts attributable to weather, structures near the aircraft10, and/or a position of the aircraft10relative to the ground and/or structures. The inputs can occur when the aircraft10is operating in an airplane mode, a helicopter mode, and/or when the aircraft10is transitioning between airplane mode and helicopter mode. In some cases when the inputs are uneven between the first and second mast torque transfer systems, the inputs can increase forces applied to the drive system12. In some cases, drive system12components are flagged for inspection in response to the component being loaded in torque at 150 % of the desired operating torque. In some cases, one or more gearboxes are flagged for removal and/or rebuilding in response to the gearboxes being loaded in torque at 155 % of the desired operating torque. In some cases, the rotor components are flagged for removal and/or rebuilding in response to being exposed to 165 % of the desired operating torque.

Referring now toFIG. 4, a flowchart of a method400of limiting torque is shown. The method400may begin at block402by the first mast torque transfer system receiving a torque input that is different than an input (or lack thereof) received by the second mast torque transfer system. In some cases, the difference in inputs can be caused by an asymmetrical gust input where airflow encountered by the proprotors44,62is unequal. Next, at block404, the method400may sense a first torque and a second torque, such as the torque of the first mast torque transfer system and the torque of the second mast torque transfer system. In some cases, the sensors106,108can be operated to conduct the sensing and report the sensed information to the system300. Next, at block406, the system300or another system can be utilized to determine a differential torque between the torque of the first mast torque transfer system and the torque of the second mast torque transfer system. Next, at block408, the method can continue by altering a control signal as a function of the differential torque. In some cases, the altered control signal can cause a reduction in the difference of torque of the first mast torque transfer system and the torque of the second mast torque transfer system.

Referring now toFIG. 5, a logic schematic of a system500for limiting torque using differential collective pitch is shown. The system generally comprises a mast torque (Qm) Error (in some cases, a torque differential calculator) calculation function502, a gain calculation function504, a washout function506, and a combination function508. The torque differential calculation function502can receive information provided by torque sensors to determine an error (or alternatively, a difference) in the torque of the first and second torque transfer systems. The gain calculation function504can map the error values with desired changes in differential collective pitch as measured in degrees. The washout function506can, over time, reduce the impact static and/or steady state torque differentials can have on the output of the system500. Finally, the combination function508can combine the output of the washed out gain calculation function504output with a lateral stick differential collective pitch command value and/or a roll rate to differential collective pitch value so that the output of the combination function takes into account the torque differential and causes reduction in the torque differential.

Referring now toFIG. 6, simulated performances of the system500is shown in a chart600. Line602shows performance of the system500when the gain is set to 0.5 degrees of differential collective pitch. Line604shows performance of the system500when the gain is set to 0.8 degrees of differential collective pitch. Line606shows performance of the system500when the gain is set to 1.0 degrees of differential collective pitch. Line608shows performance of the system500when the gain is set to 1.5 degrees of differential collective pitch.

Referring now toFIG. 8, a flowchart of a method800of operating the system500is shown. The method800can begin at block802by determining a differential torque or torque error. The method800can continue at block804by mapping the differential torque value to a gain value, such as by assigning a value in differential collective pitch degrees. Next, the method800can reduced the impact of the differential torque over time at block806by executing the washout function, such as washout function506. Next, the method800can combine the washed out value with at least one of a lateral stick differential collective pitch command or value and a roll rate to differential collective pitch command or value, with the result of the combination being utilized to execute a change in pitch of one or more of the rotorblades.

Referring now toFIG. 9, a logic schematic of a system900for limiting torque using governor and/or collective control. The system generally comprises a mast torque (Qm) Error (in some cases, a torque differential calculator) calculation function902, a gain calculation function904, a washout function906, and a combination function908. The torque differential calculation function902can receive information provided by torque sensors to determine an error (or alternatively, a difference) in the torque of the first and second torque transfer systems. The gain calculation function904can map the error values with desired changes in symmetrical collective reduction as measured in degrees. The washout function906can, over time, reduce the impact static and/or steady state torque differentials can have on the output of the system900. Finally, the combination function908can combine the output of the washed out gain calculation function904output with a power level command or value and/or a rotor governor signal or value so that the output of the combination function takes into account the torque differential and causes reduction in the torque differential.

Referring toFIG. 10, a logic schematic of another portion of system900is shown. Gain function910maps the Qm Error to a governor hold value that is output for use by a limit function912. The limit function generally prevents the governor from reacting to the change in rotations per minute so long as the change is 65 RPM or less. Accordingly, the normal operation of the governor will not fight against the system900for small RPM changes.

Referring now toFIG. 11, simulated performances of the system900is shown in a chart1100. Line1102shows performance of the system900when the gain is set to 0.9 degrees of symmetrical collective. Line1104shows performance of the system900when the gain is set to 0.23 degrees of symmetrical collective. Line1106shows performance of the system900when the gain is set to 0.46 degrees of symmetrical collective. Line1108shows performance of the system900when the gain is set to 0.92 degrees of symmetrical collective.

Referring now toFIG. 12, a flowchart of a method1200of operating the system900is shown. The method1200can begin at block1202by determining a differential torque or torque error. The method1200can continue at block1204by mapping the differential torque value to a gain value, such as by assigning a value in symmetrical collective reduction degrees. Next, the method1200can reduce the impact of the differential torque over time at block1206by executing the washout function, such as washout function906. Next, the method1200can combine the washed out value with at least one of a rotor governor signal or value and a power level command signal or value, with the result of the combination being utilized to execute a change in symmetrical collective pitch.

Referring now toFIG. 13, a logic schematic of a system1300for limiting torque using a torque command regulation system (TCRS). The system generally comprises a mast torque (Qm) Error (in some cases, a torque differential calculator) calculation function1302, a gain calculation function1304, a washout function1306, and a combination function1308. The torque differential calculation function1302can receive information provided by torque sensors to determine an error (or alternatively, a difference) in the torque of the first and second torque transfer systems. The gain calculation function1304can map the error values with desired changes in TCRS as measured in foot-pounds. The washout function1306can, over time, reduce the impact static and/or steady state torque differentials can have on the output of the system1300. Finally, the combination function1308can combine the output of the washed out gain calculation function1304output with a Qm (mast torque) command or value so that the output of the combination function takes into account the torque differential and causes reduction in the torque differential.

Referring now toFIG. 14, simulated performances of the system1300is shown in a chart1400. Line1402shows performance of the system1300when the gain is set to 13K ft-lbs of TCRS. Line1404shows performance of the system1300when the gain is set to 26K ft-lbs of TCRS. Line1406shows performance of the system1300when the gain is set to 52K ft-lbs of TCRS.

Referring now toFIG. 15, a flowchart of a method1500of operating the system1300is shown. The method1500can begin at block1502by determining a differential torque or torque error. The method1500can continue at block1504by mapping the differential torque value to a gain value, such as by assigning a value in ft-lbs of TCRS. Next, the method1500can reduce the impact of the differential torque over time at block1506by executing the washout function, such as washout function1306. Next, the method1500can combine the washed out value with a mast torque command or value, with the result of the combination being utilized to execute a change in TCRS.

Referring now toFIG. 16, a chart1600is provided that compares various combinations of systems500,900, and1300. Line1602shows performance of the system non-linear version of system500. Line1604shows performance of system900. Line1606shows performance of system1300. Line1608shows performance of a combination of systems500and1300. Line1610shows performance of a combination of systems500,900, and1300.