Folding wing tip limiting method

Abstract

The invention relates to the field of aircraft folding wing limiting, and provides a folding wing tip limiting method, which realizes folding wing limiting through a folding wing tip limiting device, and comprises the following steps: S1, pin shaft extension: electrifying and heating to drive an SMA wire, shrinking the length, and driving the pin shaft to move or twist to a target position through a first mechanical transmission module; s2, pin shaft clamping and locking: after the pin shaft reaches a target position, driving the SMA wire to be powered off, and locking the pin shaft; the pin shaft is in an extending state, and the folding wing is opened; the SMA wire is electrified, heated and reset, the length is reduced, and the pin shaft is driven by a second mechanical transmission module to move or twist towards the initial position; and S4, resetting the pin shaft: after the pin shaft returns to the initial position, the reset SMA wire material is powered off, and the folding wing is folded. Through the intelligent response of the SMA wire, accurate angle or displacement adjustment can be achieved, different use requirements are met, and influences of environment temperature and external loads are avoided.

Description

Technical Field

[0001] The present invention relates to the field of aircraft folding wing limit, and particularly to a method for limiting the folding wing tip. Background Art

[0002] Shape memory alloy (SMA) is a kind of intelligent material with unique shape memory effect and superelasticity. When heated, SMA undergoes a phase change, resulting in deformation and force, and can be used as a driver. NiTi-based alloy is one of the most commonly used SMA materials, and its phase transition temperature and properties can be controlled by adjusting the composition and heat treatment process.

[0003] At present, SMA actuators have been applied in the aerospace field, mainly used in scenarios such as vibration reduction and large deformation recovery. Some research institutions have developed SMA-based vibration isolators, shock absorbers, etc. In addition, SMA is also used to design adaptive structures, taking advantage of its characteristic of complete recovery of large deformation.

[0004] Traditional aircraft wing folding wing tip locking structures usually adopt hydraulic or electric drive, which have problems such as complex structure, large weight, and low reliability. While SMA actuators have advantages such as simple structure, light weight, and high power-to-weight ratio, they have not been applied in aircraft latch systems yet. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies of the prior art, and provides a method for limiting the folding wing tip, which fully utilizes the shape memory effect of SMA and realizes the simplification of the structure and the improvement of performance.

[0006] The present invention adopts the following technical solutions:

[0007] A method for limiting the folding wing tip, the method realizes the folding wing limit through a folding wing tip limiting device, and the folding chair limiting device includes a driving SMA wire, a reset SMA wire, a first mechanical transmission module, a second mechanical transmission module, and a pin shaft; the driving SMA wire is connected to the pin shaft through the first mechanical transmission module, and the reset SMA wire is connected to the pin shaft through the second mechanical transmission module; the pin shaft is connected to the folding wing tip;

[0008] The method includes:

[0009] S1. The pin shaft extends out: the driving SMA wire is heated by electricity, undergoes a martensite-to-austenite phase change, contracts in length, and drives the pin shaft to displace or twist to the target position through the first mechanical transmission module;

[0010] S2. Pin Shaft Lock: After the pin shaft reaches the target position, the driving SMA wire is powered off, and austenite transforms into martensite, restoring its original length; the pin shaft is locked; at this time, the pin shaft is in the extended state and the folding wing is opened.

[0011] S3. Pin Shaft Retraction: The reset SMA wire is heated by electricity, and martensite transforms into austenite, with its length contracting. Through the second mechanical transmission module, the pin shaft is driven to displace or twist to the initial position.

[0012] S4. Pin Shaft Reset: After the pin shaft returns to the initial position, the reset SMA wire is powered off, and austenite transforms into martensite, restoring its original length; at this time, the pin shaft is in the reset state and the folding wing is folded.

[0013] In any of the above possible implementation manners, a further implementation manner is provided. Both the driving SMA wire and the reset SMA wire are selected as nickel-iron-based shape memory alloy wires with a Ni mass fraction content in the range of 50%-60%. Through training, the austenite phase transformation temperature of the wires is achieved at 80°C - 130°C.

[0014] In any of the above possible implementation manners, a further implementation manner is provided. Both the driving SMA wire and the reset SMA wire are selected as nickel-iron-based shape memory alloy wires with a Ni mass fraction content of 54.8%. Through training, the phase transformation temperature of the wires is achieved at 100°C - 107°C.

[0015] In any of the above possible implementation manners, a further implementation manner is provided. A position sensor is provided on the pin shaft for monitoring and feedback of the position of the pin shaft; in step S1, when the pin shaft fails to reach the target position, feedback information is used to power on and adjust the driving SMA wire, or check for mechanical obstructions.

[0016] In any of the above possible implementation manners, a further implementation manner is provided. In step S2, the locking of the pin shaft adopts a self-locking mechanism or a locking module.

[0017] In any of the above possible implementation manners, a further implementation manner is provided. The self-locking mechanism is a ratchet or a buckle.

[0018] In any of the above possible implementation manners, a further implementation manner is provided. The driving SMA wire forms several strands through pulleys or pulley groups. Based on the precise closed-loop control of real-time in-situ monitoring of the current, temperature, length, resistance, and stress of the driving SMA wire, the precise real-time control of the temperature and length of the SMA wire is completed.

[0019] For any of the possible implementation manners described above, a further implementation manner is provided. Both the first mechanical transmission module and the second mechanical transmission module adopt a cross structure to convert the contraction motion of the driving SMA wire and the reset SMA wire into the telescopic or torsional motion of the pin shaft.

[0020] For any of the possible implementation manners described above, a further implementation manner is provided. The reset SMA wire is replaced with a reset spring, and the pin shaft is reset by the reset spring; in step S3, by releasing the restraint force of the driving SMA wire, the reset spring drives the pin shaft to reset to the initial position; in step S4, the reset spring fixes the pin shaft in the reset state through mechanical limitation.

[0021] For any of the possible implementation manners described above, a further implementation manner is provided. Both the driving SMA wire and the reset SMA wire are controlled to be heated by direct current.

[0022] The present invention is based on an accurate closed-loop control strategy for real-time in-situ monitoring of the current-temperature-length-resistance-stress of SMA wires. By measuring the current and resistance of the wires in real time, precise control of the temperature and length is achieved. Specifically, the resistance of the SMA wire is accurately measured at both ends, which can reflect the temperature and phase change state of the wire in real time, without the need to additionally arrange temperature sensors, significantly simplifying the system structure.

[0023] First, through experimental calibration of the relationship between the resistance and temperature of the SMA wire under different currents, a mapping relationship between the resistance and temperature is established, and the resistance is monitored in real time during actual application, so as to quickly and accurately calculate the current wire temperature. Secondly, the control strategy adopts a pulse width modulation (PWM) method, and the size of the wire current is accurately controlled by dynamically adjusting the PWM duty cycle to ensure that the wire temperature is stably within the phase change temperature range and the precise adjustment of the wire length is realized. When the temperature monitored in real time is lower than the target value, the duty cycle is increased to increase the current; when it exceeds the target value, the duty cycle is decreased to reduce the current, so as to stably maintain the target temperature and length.

[0024] In specific operations, first, the SMA wire is powered on, and the resistance is monitored in real time to determine the temperature and phase change process. After the wire reaches the preset target temperature and length, it is quickly powered off and enters the cooling stage, and the mechanical self-locking mechanism is used to keep the position stable. During the cooling period, the change of the resistance is continuously monitored to confirm that the phase change of the wire drops back to the martensite phase and the initial length is restored.

[0025] Through the above closed-loop control strategy, not only the precise real-time control of the temperature and length of the SMA wire is realized, but also the system response speed and energy utilization efficiency are improved, the thermal cycle fatigue of the SMA wire is reduced, the service life is extended, and the reliability and safety of the device in the application of the aviation folding wing tip limit are improved.

[0026] The beneficial effects of the present invention are as follows:

[0027] Low power consumption: During the phase change process, the SMA material mainly relies on temperature changes to achieve shape changes without the need for complex external drive sources. By energizing and heating the SMA wire, rapid deformation and recovery of the shape memory alloy can be achieved at a relatively low power. Therefore, compared with traditional motor drives or hydraulic systems, the SMA system has lower power consumption, especially when continuous power supply is not required (such as a self-locking mechanism that does not need to be energized once in place). In addition, considering that the SMA material can directly convert thermal energy into mechanical energy during the phase change process without involving complex energy conversion processes, energy loss is reduced. This makes SMA particularly prominent in miniaturized and low-energy-consuming control systems, especially suitable for fields with strict energy efficiency requirements, such as the wingtips of civil aircraft in the present invention.

[0028] In-situ control and monitoring: The present invention establishes a closed-loop control system based on real-time resistance monitoring, current feedback regulation, and PWM precise control. By accurately calculating the wire temperature and phase change state through real-time resistance measurement, the temperature control accuracy and length control precision are significantly improved. With these sensing and control strategies, the present invention can respond quickly to external changes in real time, ensuring that the opening and closing accuracy and speed of the folding wingtip limit lock meet the design requirements each time, and meeting the strict requirements of high-precision control for civil aircraft.

[0029] Small size: The drive device of the SMA material can be much smaller than traditional mechanical systems, which is crucial for civil aircraft applications with limited space and strict weight requirements. Since SMA can directly generate sufficient torque or displacement through phase change, efficient drive can still be achieved without the use of large mechanical devices.

[0030] Lifetime and reliability: The present invention effectively reduces the fatigue damage generated by the wire during repeated phase changes by optimizing the pre-stress design of the SMA wire and clarifying the relationship between it and the fatigue performance. In addition, by means of real-time monitoring of resistance changes and implementing precise current and temperature control management, fatigue accumulation caused by overheating or overloading of the wire during operation is avoided, thus significantly extending the service life of the SMA drive device. This not only reduces the number of maintenance times and maintenance costs, but also further enhances the long-term stability and safety of the device operation, and is more suitable for the folding wingtip application field with high reliability requirements.

[0031] In summary, the folding wingtip limiting device provided by the present invention has the advantages of small size, precise control, high reliability, etc. Through the intelligent response of the SMA wire, precise angle or displacement adjustment can be achieved, adapting to different usage requirements, and being unaffected by environmental temperature and external load. Through the automatic detection and feedback mechanism, the accuracy and safety of each position adjustment are ensured. This device is widely applicable to the control of folding wingtips in fields such as aerospace. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The figure shows a schematic flow chart of a folding wingtip limiting method according to an embodiment of the present invention.

[0033] Figure 2 It is a schematic flow chart in the actual application of the method of the present invention.

[0034] Figure 3 The figure shows a schematic structural diagram of the folding wing limiting device in the embodiment.

[0035] Figure 4 The figure shows a schematic diagram when the driving SMA wire is multi-stranded in the embodiment.

[0036] Figure 5 The figure shows a schematic diagram of the pin shaft structure in the embodiment.

[0037] In the figure: 1 - driving SMA wire; 2 - pin shaft; 3 - cross structure; 4 - cross structure sliding groove; 5 - movable pulley; 6 - fixed pulley; 7 - sliding part; 10 - fixed seat; 21 - pin shaft end; 22 - pin shaft tail end flat part. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] The following will describe in detail specific embodiments of the present invention with reference to specific drawings. It should be noted that the technical features described in the following embodiments or the combination of technical features should not be considered in isolation, and they can be combined with each other to achieve better technical effects.

[0039] A folding wingtip limiting method according to an embodiment of the present invention, the method realizes folding wing limiting through a folding wingtip limiting device, and the folding chair limiting device includes a driving SMA wire 1, a reset SMA wire, a first mechanical transmission module, a second mechanical transmission module, and a pin shaft 2; the driving SMA wire 1 is connected to the pin shaft 2 through the first mechanical transmission module, and the reset SMA wire is connected to the pin shaft 2 through the second mechanical transmission module; the pin shaft 2 is connected to the folding wingtip;

[0040] As Figure 1 shown, the method includes:

[0041] S1. The pin 2 extends: The driving SMA wire 1 is electrically heated, causing a martensite-to-austenite phase transformation, with its length contracting. Through the first mechanical transmission module, the pin 2 is driven to displace or twist to the target position.

[0042] S2. The pin 2 is locked: After the pin 2 reaches the target position, the driving SMA wire 1 is powered off, causing an austenite-to-martensite phase transformation and returning to its original length; the pin 2 is locked; at this time, the pin 2 is in the extended state and the folding wing is opened.

[0043] S3. The pin 2 retracts: The reset SMA wire is electrically heated, causing a martensite-to-austenite phase transformation, with its length contracting. Through the second mechanical transmission module, the pin 2 is driven to displace or twist to the initial position.

[0044] S4. The pin 2 is reset: After the pin 2 returns to the initial position, the reset SMA wire is powered off, causing an austenite-to-martensite phase transformation and returning to its original length; at this time, the pin 2 is in the reset state and the folding wing is folded.

[0045] In a specific embodiment, the folding wing tip limiting device is as Figures 3 - 5 shown.

[0046] As Figure 5 shown, the pin 2 includes a pin end portion 21 and an adjacent pin tail flat portion 22, and two cross-shaped sliding grooves 4 perpendicular to the movement direction of the pin 2 are provided on the pin tail flat portion 22.

[0047] As Figure 4 shown, the driving SMA wire forms several strands through a pulley or a pulley group. The pulley group includes a movable pulley 5 and a fixed pulley 6. The movable pulley 5 is fixed on the sliding portion 7, and the fixed pulley 6 is fixed on the fixed seat 10.

[0048] The configuration selection of the pulley group is based on load requirements, layout space constraints, and the required driving displacement and accuracy. According to the needs of the stroke and load, the extension stroke can be increased by connecting two or more groups of pulleys in series, and the driving force can be increased by connecting pulley groups in parallel to meet the design requirements that cannot be satisfied by a single pulley group.

[0049] As Figure 3 shown, the first mechanical transmission module includes a sliding portion 7 and a cross-shaped structure 3;

[0050] The sliding portion 7 slides along the telescopic direction of the pin 2; the movable pulley 5 is arranged on the sliding portion 7;

[0051] The cross-shaped structure 3 includes two sheet-like parts or rod-like parts. One ends of the two sheet-like parts or rod-like parts are respectively arranged on the sliding part 7, and the other ends are respectively arranged in two cross-shaped structure sliding grooves 4;

[0052] When the driving SMA wire 1 is energized and heated to shrink, the moving pulley 5 slides towards the fixed seat 10, driving the two sheet-like parts or rod-like parts of the cross-shaped structure 3 to slide in the cross-shaped structure sliding grooves 4, and further driving the pin shaft 2 to move in the extending direction. The extending direction of the pin shaft 2 is opposite to the moving direction of the moving pulley 5.

[0053] It should be noted that the above folding wing tip limiting device is only an implementation manner for explaining the present invention, and is not used to limit the protection scope of the present invention. The present invention can adopt a variety of other implementation manners. For example: the movement mode of the pin shaft in the above folding wing tip limiting device is a telescopic linear movement, and the pin shaft can also achieve a rotational movement through a specifically designed first mechanical transmission module. That is, the present invention can drive the displacement or torsion of the pin shaft by heating and shrinking the driving SMA wire; based on the precise closed-loop control of the real-time in-situ monitoring of the current, temperature, length, resistance and stress of the driving SMA wire, the precise real-time control of the temperature and length of the SMA wire is completed.

[0054] In addition, the reset SMA wire and the second mechanical transmission module can refer to the transmission mode of the driving SMA wire and the first mechanical transmission module, or other known existing structures can be used to achieve the drive.

[0055] In a specific embodiment, both the driving SMA wire 1 and the reset SMA wire are selected as nickel-iron-based shape memory alloy wires with a Ni mass fraction content in the range of 50%-60%, and the austenite phase transformation temperature of the wire is achieved through training at 80°C - 130°C.

[0056] As the best implementation manner, both the driving SMA wire 1 and the reset SMA wire are selected as nickel-iron-based shape memory alloy wires with a Ni mass fraction content of 54.8%, and the phase transformation temperature of the wire is achieved through training at 100°C - 107°C.

[0057] In a specific embodiment, a position sensor is arranged on the pin shaft 2 for monitoring and feedback of the position of the pin shaft 2; in step S1, when the pin shaft 2 fails to reach the target position, the feedback information is used to energize and adjust the driving SMA wire 1, or check whether there is a mechanical obstruction.

[0058] In a specific embodiment, in step S2, the locking of the pin shaft 2 adopts a self-locking mechanism or a locking module.

[0059] In a specific embodiment, the self-locking mechanism is a pawl or a buckle.

[0060] In a specific embodiment, the reset SMA wire is replaced with a reset spring, and the pin shaft 2 is reset by the reset spring. In step S3, by releasing the restraint force of the driving SMA wire 1, the reset spring drives the pin shaft 2 to reset to the initial position; in step S4, the reset spring fixes the pin shaft 2 in the reset state through mechanical limitation.

[0061] In a specific embodiment, both the driving SMA wire 1 and the reset SMA wire are controlled for heating by direct current.

[0062] Embodiment

[0063] As Figure 2 shown, this embodiment is the specific process of the method of the present invention for cyclic control of the aircraft wing tip.

[0064] For the control of the SMA wire in S104 and S114, by controlling the energization time and current magnitude of the SMA wire, its contraction degree is accurately controlled;

[0065] For the movement limitation of the pin shaft 2 in S106 and S116, through a fixed pulley / pulley block, the contraction of the SMA wire is amplified into the displacement / rotation torque of the pin shaft 2, improving the driving efficiency. Force optimization; the pulley changes the movement direction, making the contraction force of the SMA wire more effectively used to rotate the pin shaft 2; a spring / SMA wire tension form can be selected to achieve the reset movement;

[0066] For the retention of the pin shaft 2 in S108 and S118, based on the mechanical self-locking mechanism: after the pin shaft 2 rotates in place, it is held in position by mechanical means such as a ratchet, a buckle, or friction, preventing reverse movement due to the cooling and recovery of the SMA wire. And there is no continuous energy consumption: once the pin shaft 2 is in place and self-locked, the SMA wire can be powered off, saving energy.

[0067] Specifically, it includes:

[0068] S102 Limiting the retracted state:

[0069] In this state, the pin shaft 2 is in the original position, the SMA wire is not energized and is in a relaxed state. At this time, the device is in a standby state and the pin shaft is not locked.

[0070] S104 Energizing and heating the driving SMA wire:

[0071] Energize the SMA wire to cause it to heat up. During the heating process of the SMA wire, a martensite-to-austenite phase transformation occurs, resulting in its length contraction.

[0072] S106 SMA contraction drives the movement of the pin shaft 2:

[0073] The contraction of the SMA wire transfers the driving force through a fixed pulley system, generating a displacement or torsional effect on the pin shaft 2. Under the action of this torque, the pin shaft 2 expands and contracts or rotates to accurately reach a predetermined angular position (such as the locked or unlocked state).

[0074] S108 reaches the target position and cuts off the power supply:

[0075] After the pin shaft 2 reaches the target position, the power supply of the SMA wire is cut off. The SMA wire then begins to cool, undergoing a phase transformation from austenite to martensite and returning to its original length. Due to the action of mechanical self-locking or other holding mechanisms, the pin shaft 2 remains in the new position and is not affected by the recovery of the SMA wire.

[0076] S110 Status monitoring and feedback:

[0077] The position of the pin shaft 2 is detected in real time by a sensor to ensure that it has reached the target position. If the position does not reach the predetermined value, the power can be reconnected for adjustment, or it can be checked whether there is a mechanical obstruction.

[0078] S112 Limit extension state:

[0079] At this time, the limit device is in working condition, the position of the pin shaft 2 is stable, and it waits for the next adjustment requirement for the position of the pin shaft 2.

[0080] S114 Energize and heat to reset the SMA wire:

[0081] Energize the reset SMA wire to make it heat up again, triggering a phase transformation from martensite to austenite and contracting in length.

[0082] S116 SMA contraction drives the pin shaft 2 to retract:

[0083] The contraction of the reset SMA wire drives the displacement or torsion of the pin shaft 2 through a fixed pulley system. During this process, the pin shaft 2 expands and contracts or rotates to reach the retracted target position.

[0084] S118 Reaches the retracted position and cuts off the power supply:

[0085] After the pin shaft 2 retracts to the target position, the power supply of the SMA wire is cut off. The SMA wire cools and returns to its original length, and the pin shaft 2 remains in the new position under the action of mechanical self-locking or other holding mechanisms.

[0086] S120 Status monitoring and feedback:

[0087] Confirm through the sensor that the pin shaft 2 has returned to the target position. If it does not reach the target position, the power can be reconnected for adjustment, or it can be checked whether there is a mechanical obstruction.

[0088] Step cycle:

[0089] After the completion of the recovery state, return to step S102 and wait for the next operation.

[0090] Although several embodiments of the present invention have been given in this text, those skilled in the art should understand that the embodiments in this text can be changed without departing from the spirit of the present invention. The above embodiments are only exemplary and should not be used to limit the scope of the rights of the present invention by the embodiments in this text.

Claims

1. A folding wing tip limiting method, characterized in that: The method realizes folding wing limiting by a folding wing tip limiting device, wherein the folding wing tip limiting device comprises a driving SMA wire, a resetting SMA wire, a first mechanical transmission module, a second mechanical transmission module, and a pin shaft; the driving SMA wire is connected to the pin shaft through the first mechanical transmission module, and the resetting SMA wire is connected to the pin shaft through the second mechanical transmission module; The pin is connected to the folding wing tip; The method comprises: S1, pin extension: power is applied to heat the driving SMA wire, causing a phase transformation from martensite to austenite, shrinking the length, and driving the pin to move or twist to a target position through the first mechanical transmission module; S2, pin locking: after the pin reaches the target position, the driving SMA wire is powered off, austenite to martensite phase transformation occurs, and the original length is restored; the pin is locked, at this time the pin is in an extended state, and the folding wings are opened; S3, retracting the pin: applying power to heat the reset SMA wire, causing a phase transformation from martensite to austenite, shrinking the length, and driving the pin to move or twist toward the initial position through the second mechanical transmission module; S4, pin resetting: after the pin is returned to the initial position, the reset SMA wire is powered off, undergoing austenite to martensite phase transformation, and returning to its original length; At this time, the pin shaft is in a reset state, and the folding wings are folded.

2. The folding wing tip limiting method according to claim 1, characterized in that: The driving SMA wire and the resetting SMA wire are both made of nickel-iron based memory alloy wire with a Ni mass fraction content of 50%-60%, and the austenite phase transformation temperature of the wire is 80°C-130°C through training.

3. The folding wing tip limiting method according to claim 2, characterized in that: The driving SMA wire and the resetting SMA wire are both made of nickel-iron based memory alloy wire with a Ni mass fraction of 54.8% and an austenite phase transition temperature of 100° C.-107° C.

4. The folding wing tip limiting method according to claim 1, characterized in that: The pin shaft is provided with a position sensor for monitoring and providing feedback on the position of the pin shaft. In step S1, when the pin shaft fails to reach the target position, feedback information is used to adjust the power supply of the driving SMA wire or to check whether there is any mechanical obstruction.

5. The folding wing tip limiting method according to claim 1, characterized in that: In step S2, the pin shaft is locked by a self-locking mechanism or a locking module.

6. The folding wing tip limiting method according to claim 5, characterized in that: The self-locking mechanism is a ratchet or a buckle.

7. The folding wing tip limiting method according to claim 1, characterized in that: The driving SMA wire is formed into several strands through a pulley or a pulley group, and the precise closed-loop control based on the real-time in-situ monitoring of the current, temperature, length, resistance and stress of the driving SMA wire is completed to achieve accurate real-time control of the temperature and length of the SMA wire.

8. The folding wing tip limiting method according to claim 1, characterized in that: The first mechanical transmission module and the second mechanical transmission module both adopt a cross structure to transform the contraction motion of the driving SMA wire and the resetting SMA wire into the extension or torsional motion of the pin.

9. The folding wing tip limiting method according to claim 1, characterized in that: The reset SMA wire is replaced with a reset spring, and the pin is reset by the reset spring; in step S3, the restraining force of the driving SMA wire is released so that the reset spring drives the pin to reset to the initial position; in step S4, the reset spring fixes the pin in the reset state through mechanical limit.

10. The folding wing tip limiting method according to claim 1, characterized in that: The driving SMA wire and the resetting SMA wire are both heated by direct current control.

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