Aircraft ground quasi-zero stiffness energy-absorbing and vibration-damping take-off and landing platform

Abstract

This invention discloses a near-zero stiffness energy-absorbing and vibration-damping takeoff and landing platform for aircraft, including a platform panel, an energy-absorbing and vibration-damping device, and a lower support beam. The energy-absorbing and vibration-damping device is located between the platform panel and the lower support beam. The energy-absorbing and vibration-damping device includes an upper shell, a middle shell, and a lower shell arranged sequentially along the axial direction. The upper shell and the middle shell are slidably connected at one end and elastically connected by a disc spring assembly. A damper is provided between the upper shell and the middle shell. One end of the middle shell is slidably engaged with the lower shell. A second damper is also provided between the middle shell and the lower shell. In this invention, by configuring the first and second dampers with an asymmetrical characteristic of low damping during compression and high damping during extension, soft contact is ensured at the moment of landing, and rebound oscillation is effectively suppressed, achieving high static and low dynamic characteristics. By adjusting the magnitude and direction of the current flowing through the coil, energy is further dissipated using the electromagnetic damping effect, achieving multi-dimensional high-efficiency energy dissipation.

Description

Technical Field

[0001] This invention relates to the field of vertical take-off and landing infrastructure technology, and more specifically to a near-zero stiffness energy-absorbing and vibration-damping take-off and landing platform for aircraft. Background Technology

[0002] Electric Vertical Take-Off and Landing (eVTOL) aircraft, as the core carrier of future urban air mobility (UAM), are considered a key technology for solving urban ground traffic congestion and building a three-dimensional transportation network due to their vertical take-off and landing capabilities, low noise characteristics, and zero emissions. With the accelerated commercialization of the eVTOL industry, the demand for supporting ground infrastructure, verticeports, is becoming increasingly urgent. As the main structure supporting the take-off, landing, and parking of aircraft, the vibration damping performance of the take-off and landing platform not only affects the safety of aircraft take-off and landing but also directly impacts the surrounding building environment and passenger comfort.

[0003] During the landing phase of an eVTOL aircraft, the strong downwash airflow generated by the rotor is violently coupled with the platform surface. In addition, the release of the aircraft's own gravitational potential energy and the fluctuation of its descent speed cause the take-off and landing platform to bear extremely complex transient impact loads.

[0004] Compared to traditional aircraft, eVTOL operations in urban environments are characterized by high frequency, high density, and mixed operation of multiple aircraft types. The alternating takeoffs and landings of aircraft of different tonnages result in a wide range of load conditions faced by the platform. This poses more stringent challenges to the platform's high load-bearing capacity and high-frequency shock isolation capabilities.

[0005] Currently, the relevant vibration reduction technologies have obvious limitations:

[0006] First, traditional vibration isolation technology faces the contradiction between "load-bearing" and "vibration isolation", and its stiffness is not adjustable. Existing rubber vibration isolation pads or spring structures have high static stiffness, which is difficult to cope with the high-frequency impact during eVTOL take-off and landing. Moreover, their mechanical parameters are fixed once they leave the factory and cannot be dynamically adjusted according to the different tonnage of the landing aircraft, making it difficult to meet the adaptive vibration reduction requirements under mixed operation of multiple aircraft types.

[0007] Secondly, vibration damping devices based on the tuning principle lack adaptability. For example, patent document CN120517634A discloses a TLD vibration damping platform for the take-off and landing of large UAVs, which uses a tuned liquid damper (TLD) to dissipate energy. However, the vibration damping effect of such tuned mass devices (including TMD and TLD) is highly dependent on a specific tuning frequency. During the operation of eVTOL aircraft, the effective payload fluctuates significantly due to adjustments in the number of passengers and battery pack configuration, resulting in uneven mass distribution of the system. This easily leads to tuning detuning, causing a significant decrease or even failure in vibration damping performance. In addition, TLD systems are usually bulky and mainly designed for horizontal vibration control, with limited capacity to absorb the large vertical energy impacts that eVTOLs experience during landing.

[0008] Furthermore, semi-active magnetorheological fluid (MRF) vibration damping systems suffer from limitations in adjustment dimensions and reliability. While semi-active technologies such as MRF dampers can alter damping characteristics by adjusting current, their complex systems require sensors, controllers, and uninterruptible power supplies. In the high-frequency outdoor environment of eVTOL (eVTOL) operations, these complex electronic control systems face challenges in terms of waterproofing, dustproofing, electromagnetic interference, and long-term maintenance-free operation. More importantly, existing magnetic adjustment technologies are largely limited to damping force adjustment, with limited dynamic and continuous adjustment capabilities for stiffness, especially negative stiffness. Faced with the high-energy transient impact released during aircraft landing, the response speed and control precision of such systems are often mismatched, and the high maintenance costs hinder large-scale commercial deployment.

[0009] Finally, patent document CN121701603A discloses an impact-resistant six-degree-of-freedom quasi-zero stiffness vibration isolation platform. It uses air springs to provide positive stiffness, utilizes the Lorentz force generated by an energized coil cutting magnetic field lines in the air gap of a permanent magnet to construct negative stiffness, and employs a voice coil motor for active vibration control. However, this solution is essentially designed for micro-vibration isolation in precision manufacturing equipment and cannot be directly applied to the high-frequency, high-impact, and unattended outdoor operating conditions of eVTOL take-off and landing platforms. Specifically, this solution relies on air springs and complex active control systems, such as voice coil motors, sensors, and servo valves. This not only results in a complex structure and high energy consumption but also poses a risk of single-point failure, making it difficult to meet the high reliability requirements of infrastructure. More importantly, its negative stiffness depends on the high-speed reciprocating motion of the coil cutting magnetic field lines in a strong magnetic field. During high-frequency operation, the large impact velocity of eVTOL landing will generate significant Joule heat and back electromotive force, which can easily cause thermal demagnetization of the nearby neodymium iron boron permanent magnets, leading to the failure of vibration isolation performance. In addition, this solution lacks a passive energy dissipation mechanism for platform rebound after landing impact, and cannot meet the dual requirements of "soft landing" and "anti-rebound". Therefore, it is difficult to meet the actual operational needs of urban vertical take-off and landing ports.

[0010] In summary, existing technologies generally suffer from problems such as difficulty in decoupling static and dynamic stiffness, poor adaptability to operating conditions, a lack of stiffness adjustment methods, low impact energy absorption efficiency, and inconvenient maintenance. Therefore, there is an urgent need to develop a modular energy-absorbing and vibration-damping device with "high static and low dynamic" stiffness characteristics, continuously adjustable stiffness, simple and reliable structure, and easy maintenance, to solve the vibration control problem of eVTOL take-off and landing platforms under complex operating conditions and meet the development needs of future urban air transportation infrastructure. Summary of the Invention

[0011] The technical problem to be solved by this invention is how to achieve high static and low dynamic stiffness characteristics and efficient dissipation of impact energy.

[0012] This invention solves the above-mentioned technical problems through the following technical means: a near-zero stiffness energy-absorbing and vibration-damping take-off and landing platform for aircraft, comprising a platform panel, an upper support beam, an energy-absorbing and vibration-damping device, and a lower support beam. The upper support beam, at the end opposite to the energy-absorbing and vibration-damping device, is connected to the platform panel. The energy-absorbing and vibration-damping device is located between the upper and lower support beams. The energy-absorbing and vibration-damping device includes an upper shell, a middle shell, and a lower shell arranged sequentially along the axial direction. The upper shell and the middle shell are slidably connected at one end and elastically connected by a disc spring assembly. A damper is provided between the upper shell and the middle shell. One end of the middle shell is slidably engaged with the lower shell. A second damper is also provided between the middle shell and the lower shell. The middle shell and the lower shell are respectively equipped with… There are upper and lower permanent magnets. The upper and lower permanent magnets with the same poles opposite each other can form a repulsive negative stiffness force. The disc spring assembly is configured to form a positive stiffness force that cancels out the negative stiffness force. The initial pre-compression of the disc spring assembly is changed to adjust the overall stiffness of the energy absorption and vibration damping device. Dampers one and two are used to suppress the rebound of the lower shell toward the middle shell and / or the middle shell toward the upper shell, and are configured such that the damping during compression is less than the damping during rebound. A magnetic induction coil is also provided inside the lower shell, located outside the lower permanent magnet. By adjusting the current of the magnetic induction coil, the magnetic repulsion force distribution between the upper and lower permanent magnets is changed so that the total stiffness of the system shifts in the displacement range that is close to zero at the equilibrium position.

[0013] As a preferred technical solution, a gasket is also provided between the connection ends of the middle shell and the lower shell.

[0014] As a preferred technical solution, the upper shell includes a cover plate and a pressure plate, the cover plate and the pressure plate are fixed together, the middle shell includes an upper magnetic yoke, the upper magnetic yoke includes a body and a guide shaft fixed on the top of the body, a plurality of threaded guide posts are fixedly connected to one end of the body facing the upper shell, and a nut is threadedly connected to one end of the threaded guide post that penetrates into the upper shell, and the threaded guide post and the guide shaft are both in sliding fit with the pressure plate.

[0015] As a preferred technical solution, the platform panel is fixedly connected to the cover plate via an upper support beam. One end of the upper support beam is welded and fixed to the platform panel. The upper support beam is connected and fastened to the cover plate via bolts. The cover plate has an installation hole 1 that matches the bolts. The end of the cover plate facing the lower housing has an annular protrusion 1 and an annular protrusion 2. The annular protrusion 1 is located outside the annular protrusion 2.

[0016] As a preferred technical solution, the piston rod of damper one is fixedly connected to the cover plate, the cylinder of damper one is fixedly connected to the piston rod end of damper two, the intermediate shell includes an upper magnetic yoke, the upper magnetic yoke includes a body, the body is an open-mouth structure with an open bottom and closed circumferentially, the body of the upper magnetic yoke is provided with a guide hole one that matches the piston rod end of damper two, the inner wall of the top of the body is fixedly connected with an annular protrusion three, and the upper permanent magnet is fixed between the inner wall of the body and the annular protrusion three.

[0017] As a preferred technical solution, the lower housing includes a lower magnetic yoke, and an annular protrusion four and an annular protrusion five are fixedly connected to one end of the lower magnetic yoke facing the cover plate. The annular protrusion five is located outside the annular protrusion four. The lower permanent magnet is fixedly connected between the annular protrusion four and the annular protrusion five. The annular protrusion five has a winding groove in its circumference that is compatible with the magnetic coil.

[0018] As a preferred technical solution, the damper has a threaded hole 1 at its bottom and a threaded hole 2 at the end of its piston rod. The threaded hole 2 is compatible with the internal hexagon bolt. A limit groove is provided on the inner wall of the top of the cover plate. The piston rod of the damper is fixedly connected with an annular protrusion 6 that is compatible with the limit groove.

[0019] As a preferred technical solution, the piston rod end of the damper two is provided with a threaded guide post two, and a limiting block that matches the guide hole one is fixedly connected to the piston rod of the damper two. A threaded hole three is opened at the bottom of the damper two.

[0020] As a preferred technical solution, the inner wall of the main body is provided with an annular groove, the washer is pressed into the annular groove, and a number of guide posts are fixedly connected to the annular protrusion in five directions. The upper magnetic yoke is provided with a guide groove in the circumference of the main body that matches the guide posts.

[0021] As a preferred technical solution, it is used for the take-off and landing of eVTOL aircraft.

[0022] The beneficial effects of this invention are as follows: (1) In this invention, by configuring damper one and damper two with the asymmetric characteristics of low damping during compression stroke and high damping during extension stroke, soft contact is ensured during landing and rebound oscillation is effectively suppressed, thus achieving high static and low dynamic characteristics. The negative stiffness magnetic force generated by the upper and lower permanent magnets and the positive stiffness force formed by the configuration of disc spring group cancel each other out, so that the total dynamic stiffness of the system approaches zero and has an extremely low natural frequency. This effectively isolates low-frequency micro-vibrations, solves the problem of poor vibration isolation effect of traditional vibration isolation system in the low-frequency range, and significantly prolongs the pulse period of take-off and landing impact, thus consuming vibration energy. By adjusting the magnitude and direction of the current flowing into the coil, the magnetic field distribution is dynamically changed to achieve a wide range of translation in the quasi-zero stiffness range, adapting to the landing impact of eVTOLs of different tonnages. At the same time, the electromagnetic damping effect is used to further dissipate energy, achieving multi-dimensional high-efficiency energy consumption.

[0023] (2) In this invention, by setting the washer, when the eVTOL aircraft is subjected to take-off and landing impact force exceeding the design threshold due to operational errors or strong gusts, the disc spring assembly enters the large deformation region, the positive stiffness increases sharply, and it exhibits significant hard spring characteristics, which limits the infinite expansion of displacement and prevents the equipment from hitting the bottom; as the displacement increases, the washer at the lower end of the upper magnetic yoke contacts the lower magnetic yoke and is compressed. The washer, as the last mechanical buffer barrier, uses its high damping characteristics to absorb the instantaneous huge impact kinetic energy and protect the internal components from damage. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the overall structure of the energy-absorbing and vibration-damping device provided in an embodiment of the present invention; Figure 2 This is a schematic cross-sectional view of the energy-absorbing and vibration-damping device provided in an embodiment of the present invention. Figure 3 This is a schematic diagram of the bottom structure of the cover plate provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of the top structure of the cover plate provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of the pressure plate structure provided in an embodiment of the present invention; Figure 6 This is a schematic diagram of the overall structure of the upper magnetic yoke provided in an embodiment of the present invention; Figure 7 This is a schematic diagram of the upper magnetic yoke structure viewed from below, provided in an embodiment of the present invention. Figure 8 This is a schematic diagram of the top structure of the lower magnetic yoke provided in an embodiment of the present invention; Figure 9 This is a schematic diagram of the bottom structure of the lower magnetic yoke provided in an embodiment of the present invention; Figure 10 This is a schematic diagram of a damper structure provided in an embodiment of the present invention; Figure 11This is a front view schematic diagram of the damper structure provided in an embodiment of the present invention; Figure 12 This is a schematic diagram of the two-dimensional structure of the damper provided in an embodiment of the present invention; Figure 13 This is a partial cross-sectional structural diagram of the energy-absorbing and vibration-damping take-off and landing platform provided in an embodiment of the present invention; Figure 14 This is a bottom view structural diagram of the energy-absorbing and vibration-damping take-off and landing platform provided in an embodiment of the present invention; Reference numerals: 1. Cover plate; 101. Mounting hole one; 102. Annular protrusion one; 103. Limiting groove; 104. Annular protrusion two; 105. Countersunk threaded hole one; 2. Pressure plate; 201. Mounting hole two; 202. Mounting hole three; 3. Guide sleeve; 4. Upper yoke; 401. Threaded guide post one; 402. Guide shaft; 403. Guide groove; 404. Annular protrusion three; 405. Guide hole one; 406. Annular groove; 407. Body; 5. Magnetic coil; 6. Disc spring assembly; 7. Lower yoke; 701. Winding groove; 702. Annular 703. Protrusion 4; 704. Guide post; 705. Mounting hole 4; 706. Countersunk threaded hole 2; 707. Annular protrusion 5; 8. Nut; 9. Damper 1; 907. Threaded hole 1; 908. Threaded hole 2; 909. Annular protrusion 6; 10. Washer; 11. Socket headstock bolt; 12. Damper 2; 1208. Threaded guide post 2; 1209. Threaded hole 3; 1200. Limiting block; 13. Upper permanent magnet; 14. Lower permanent magnet; 15. Platform panel; 16. Upper support beam; 17. Lower support beam; 18. Energy absorption and vibration damping device. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] See Figure 13 , Figure 14 The quasi-zero stiffness energy-absorbing and vibration-damping take-off and landing platform for aircraft includes a platform panel 15, an upper support beam 16, a lower support beam 17, and energy-absorbing and vibration-damping devices 18. One end of the upper support beam 16 is welded and fixed to the platform panel 15, and the other end is connected to the lower support beam 17 through multiple energy-absorbing and vibration-damping devices 18. See Figure 1The energy-absorbing and vibration-damping device 18 includes a cover plate 1, a pressure plate 2, an upper magnetic yoke 4, a disc spring assembly 6, and a lower magnetic yoke 7. The cover plate 1 is fixedly connected to the upper support beam 16 by bolts, and the lower magnetic yoke 7 is fixedly connected to the lower support beam 17. The end of the cover plate 1 facing the lower magnetic yoke 7 is fixedly connected to the pressure plate 2. The upper magnetic yoke 4 is slidably connected to the pressure plate 2, and the lower magnetic yoke 7 is slidably connected to the end of the upper magnetic yoke 4 away from the pressure plate 2. The pressure plate 2 is also elastically connected to the top plane of the upper magnetic yoke 4 through the disc spring assembly 6. The upper magnetic yoke 4 has a guide shaft cavity, and a damper 9 is provided in the guide shaft cavity. The piston rod of the damper 9 is fixedly connected to the cover plate 1, and the cylinder of the damper 9 is fixedly connected to the top plane of the upper magnetic yoke 4. A second damper 12 is provided between the upper magnetic yoke 4 and the lower magnetic yoke 7. The piston rod of the second damper 12 is fixedly connected to the cylinder of the first damper 9, and the cylinder of the second damper 12 is fixedly connected to the lower magnetic yoke 7. It should be noted that the disc spring assembly 6 is composed of multiple disc springs stacked together to provide positive stiffness. The cover plate 1 and the pressure plate 2 form the upper shell, the upper magnetic yoke 4 forms the middle shell, and the lower magnetic yoke 7 forms the lower shell. The upper shell, the middle shell, and the lower shell are arranged sequentially along the axial direction.

[0027] See Figure 3 , Figure 4 The cover plate 1 is the top load-bearing component of the device. The cover plate 1 has a countersunk threaded hole 105 that penetrates the cover plate 1. The cover plate 1 has multiple mounting holes 101. Bolts are installed in the mounting holes 101. The cover plate 1 is connected and fastened to the upper support beam 16 by bolts. The end of the cover plate 1 facing the lower magnetic yoke 7 has an annular protrusion 102 and an annular protrusion 204. The annular protrusion 102 is larger than the annular protrusion 204 and is located outside the annular protrusion 204. The bottom of the annular protrusion 102 and the annular protrusion 204 both abut against the upper surface of the pressure plate 2, thereby effectively transferring the vertical impact load generated during the take-off and landing of the eVTOL to the pressure plate 2 and the disc spring assembly 6 connected below the pressure plate 2.

[0028] See Figure 5 The pressure plate 2 has a mounting hole 3 202 at its center and a number of mounting holes 201 on its surface.

[0029] See Figure 6 , Figure 7The upper magnetic yoke 4 includes a body 407, a guide shaft 402 fixed to the top of the body 407, a threaded guide post 401, and an annular protrusion 404. The body 407 is an open-mouth structure with an open bottom and closed circumferentially. The annular protrusion 404 is fixedly connected to the inner wall of the top of the body 407. An upper permanent magnet 13 is fixedly connected between the inner wall of the body 407 and the annular protrusion 404. The upper permanent magnet 13 is interference-fitted with the inner wall of the body 407 and the annular protrusion 404. The guide shaft 402 is fixedly connected to the center of the top of the body 407. The threaded guide post 401... Multiple threaded guide posts 401 are provided and evenly distributed on the outside of the guide shaft 402. In this embodiment, multiple threaded guide posts 401 are distributed at equal angles on the outside of the guide shaft 402. The threaded guide post 401 is a cylinder with a threaded section. A guide sleeve 3 is fixedly connected in the mounting hole 201. The guide sleeve 3 is made of metal. The threaded section can pass through the center hole of the guide sleeve 3, and a nut 8 is threadedly connected to one end of the guide sleeve 3 through the center hole. By adjusting the locking position of the nut 8, the initial pre-compression of the disc spring assembly 6 is changed, thereby adjusting the overall stiffness of the device to adapt to vibration environments of different frequencies and achieve wide-frequency vibration reduction. The number of mounting holes 201 and threaded guide pins 401 are matched. In this embodiment, there are four threaded guide pins 401 and four mounting holes 201. The guide shaft 402 is a hollow structure with an inner cavity. The inner cavity is matched with the size of the damper 9. The top of the body 407 forms the top plane of the upper magnetic yoke 4. A guide hole 405 is provided at the center of the body 407. The guide hole 405 communicates with the inner cavity of the guide shaft. The function of the guide hole 405 is to achieve a fixed connection between the piston rod end of the damper 12 and the cylinder of the damper 9.

[0030] The inner wall of the main body 407 is provided with an annular groove 406, and a washer 10 is press-fitted in the annular groove 406. When the device is subjected to a severe impact that causes the displacement to exceed the negative stiffness adjustment threshold, the upper magnetic yoke 4 and the lower magnetic yoke 7 contact the washer 10, and the elastic deformation of the washer 10 absorbs the impact energy and provides hard stop buffer.

[0031] See Figure 8 , Figure 9 The lower magnetic yoke 7 is fixedly connected to one end of the cover plate 1 with annular protrusion 4 702 and annular protrusion 5 706. Annular protrusion 5 706 is located outside of annular protrusion 4 702. A lower permanent magnet 14 is fixedly connected between annular protrusion 4 702 and annular protrusion 5 706. The upper permanent magnet 13 and the lower permanent magnet 14 are arranged with the same pole facing each other, and the negative stiffness characteristics required by the system are provided by the principle of like poles repulsion. The annular protrusion 706 is circumferentially fixed with several guide posts 703. The body 407 of the upper magnetic yoke 4 is circumferentially provided with guide grooves 403 that are adapted to the guide posts 703. The lower end face of the lower magnetic yoke 7 is also provided with a countersunk threaded hole 705 for connecting the cylinder of the damper 12. The annular protrusion 706 is circumferentially provided with a winding groove 701. The magnetic coil 5 is embedded in the winding groove 701. Its pins are led out and electrically connected to an external controller. By adjusting the magnitude and direction of the current, the magnetic field strength and direction can be precisely controlled. The guide posts 703 prevent the upper magnetic yoke 4 and the lower magnetic yoke 7 from rotating relative to each other, thereby causing shear damage to the magnetic coil 5. The lower magnetic yoke 7 is provided with a mounting hole 704. The lower magnetic yoke 7 is fixedly connected to the lower support beam 17 by bolts. The mounting hole 704 is a bolt hole or a through hole.

[0032] See Figure 10 The piston rod of damper 2 12 is fixed to the cylinder of damper 1 9 by bolts. The bottom of the cylinder of damper 1 9 is provided with a threaded hole 901 that matches the bolt. The end of the piston rod of damper 1 9 is provided with a threaded hole 902 that matches the internal hex bolt 11. In order to prevent the piston rod of damper 1 9 from rotating relative to the cover plate 1, a limiting groove 103 is provided on the inner wall of the top of the cover plate 1. The piston rod of damper 1 9 is fixedly connected with an annular protrusion 903 that matches the limiting groove 103.

[0033] See Figure 11 , Figure 12 The piston rod end of the damper 2 12 is provided with a threaded guide post 2 1201, and a limit block 1203 is fixedly connected to the piston rod of the damper 2 12. A threaded hole 3 1202 is opened at the bottom of the damper 2 12.

[0034] Quasi-zero stiffness characteristics in static equilibrium state: When the eVTOL aircraft is parked or in static equilibrium without impact, the upper permanent magnet 13 and the lower permanent magnet 14 are opposite each other with the same pole, generating a vertically upward repulsive magnetic force and a negative stiffness force. At the same time, the disc spring assembly 6 is in a compressed state under the preload of the nut 8, generating a vertically downward elastic restoring force and a positive stiffness force. By adjusting the position of the nut 8 to change the preload of the disc spring assembly 6, the positive stiffness coefficient and the negative stiffness coefficient cancel each other out at the equilibrium position, and the total dynamic stiffness of the system approaches zero. At this time, the entire device has an extremely low natural frequency, which can effectively isolate low-frequency micro-vibrations and solve the problem of poor vibration isolation effect of traditional vibration isolation systems in the low-frequency range. Wideband vibration isolation under normal takeoff and landing conditions: When the eVTOL aircraft lands and contacts the deck, the impact force is transmitted to the cover plate 1. The cover plate 1 is pressed downward, and the pressure plate 2 is pushed down through the annular protrusion 102 and the annular protrusion 104. The pressure plate 2 compresses the disc spring assembly 6. Due to the nonlinear positive stiffness characteristics of the disc spring assembly 6, combined with the nonlinear negative stiffness characteristics of the upper permanent magnet 13 and the lower permanent magnet 14, the system can maintain a low equivalent stiffness throughout the entire stroke, significantly prolonging the pulse period of the takeoff and landing impact and consuming vibration energy. During the downward movement of the pressure plate 2, the cylinder of the damper 9 moves relative to the piston rod of the damper 9. At the same time, the upper magnetic yoke 4 drives the piston rod of the damper 12 to move relative to the cylinder of the damper 12. The dampers 9 and 12 generate a damping force that resists the movement, converting mechanical energy into heat energy for dissipation. An external current is passed through the magnetic coil 5, and the energy is further dissipated by the electromagnetic damping effect, realizing multi-dimensional energy consumption. Nonlinear stiff spring and buffer under high impact conditions: When the eVTOL aircraft experiences takeoff and landing impact forces exceeding the design threshold due to operational errors or strong gusts, the disc spring assembly 6 enters the large deformation region, and its positive stiffness increases sharply, exhibiting significant stiff spring characteristics. This limits the unlimited expansion of displacement and prevents the equipment from bottoming out. As the displacement increases, the washer 10 at the lower end of the upper magnetic yoke 4 contacts and is compressed with the lower magnetic yoke 7. The washer 10 acts as the final mechanical buffer barrier, using its high damping characteristics to absorb the instantaneous massive impact kinetic energy and protect the internal components from damage.

[0035] Anti-oscillation reset: After the impact load disappears, the disc spring assembly 6 releases its elastic potential energy, pushing the device to reset. During this process, the annular protrusion 903 at the top of damper 19 cooperates with the limiting groove 103 of the cover plate 1, and the limiting block 1203 of damper 212 cooperates with the guide hole 405 of the upper yoke 4, which restricts the circumferential rotation of the piston rod of damper 19 and the piston rod of damper 212, preventing structural loosening caused by torque accumulation. Damper 19 mainly suppresses the low-frequency large-amplitude oscillation caused by the rebound of disc spring assembly 6; damper 212 mainly suppresses the high-frequency micro-oscillation caused by the change of repulsive force between permanent magnets. The two work together to ensure that the device quickly returns to the static equilibrium state. Semi-active magnetic field control: Under special conditions of alternating takeoff and landing of aircraft of different weights, the system activates the magnetic field control mode: the external controller adjusts the magnitude or direction of the current input to the magnetic coil 5 according to the aircraft parameters and the load information transmitted by the pilot, changes the additional magnetic field generated by the coil, thereby adjusting the magnitude of the repulsive force between the upper permanent magnet 13 and the lower permanent magnet 14 in real time, that is, adjusting the strength of the negative stiffness, dynamically adjusting the equilibrium point position and equivalent stiffness of the system, so that the device always maintains the optimal vibration isolation state and adapts to variable load conditions.

[0036] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A near-zero stiffness energy-absorbing and vibration-damping takeoff and landing platform for aircraft, characterized in that, The system includes a platform panel, an energy-absorbing and vibration-damping device, an upper support beam, and a lower support beam. The energy-absorbing and vibration-damping device is located between the upper and lower support beams. The platform panel is connected to the end of the upper support beam away from the energy-absorbing and vibration-damping device. The energy-absorbing and vibration-damping device includes an upper shell, a middle shell, and a lower shell arranged sequentially along the axial direction. The upper shell and the middle shell are slidably connected at one end and elastically connected by a disc spring assembly. A damper is provided between the upper shell and the middle shell. One end of the middle shell is slidably engaged with the lower shell. A second damper is also provided between the middle shell and the lower shell. An upper permanent magnet and a lower permanent magnet are respectively installed inside the middle shell and the lower shell. The upper permanent magnets have the same pole facing each other. The lower permanent magnet and the disc spring assembly can form a repulsive negative stiffness force. The disc spring assembly is configured to form a positive stiffness force that cancels out the negative stiffness force. The initial pre-compression of the disc spring assembly is changed to adjust the overall stiffness of the energy absorption and vibration damping device. Dampers one and two are used to suppress the rebound of the lower shell toward the middle shell and / or the middle shell toward the upper shell, and are configured such that the damping during compression is less than the damping during rebound. A magnetic induction coil is also provided inside the lower shell, located outside the lower permanent magnet. By adjusting the current of the magnetic induction coil, the magnetic repulsion force distribution between the upper permanent magnet and the lower permanent magnet is changed so that the total stiffness of the system shifts within the displacement range that is close to zero at the equilibrium position.

2. The near-zero stiffness energy-absorbing and vibration-damping takeoff and landing platform for aircraft as described in claim 1, characterized in that, A gasket is also provided between the connection ends of the middle shell and the lower shell.

3. The near-zero stiffness energy-absorbing and vibration-damping takeoff and landing platform for aircraft according to claim 1, characterized in that, The upper housing includes a cover plate and a pressure plate, which are fixed together. The middle housing includes an upper magnetic yoke, which includes a body and a guide shaft fixed to the top of the body. Multiple threaded guide posts are fixedly connected to one end of the body facing the upper housing. A nut is threaded to one end of the threaded guide post that passes through the upper housing. The threaded guide post and the guide shaft are slidably engaged with the pressure plate.

4. The near-zero stiffness energy-absorbing and vibration-damping takeoff and landing platform for aircraft according to claim 3, characterized in that, One end of the upper support beam is welded and fixed to the platform panel. The upper support beam is connected and fastened to the cover plate by bolts. The cover plate has a mounting hole 1 that matches the bolts. The end of the cover plate facing the lower shell has an annular protrusion 1 and an annular protrusion 2. The annular protrusion 1 is located outside the annular protrusion 2.

5. The near-zero stiffness energy-absorbing and vibration-damping takeoff and landing platform for aircraft according to claim 3, characterized in that, The piston rod of damper one is fixedly connected to the cover plate, the cylinder of damper one is fixedly connected to the end of the piston rod of damper two, the intermediate shell includes an upper magnetic yoke, the upper magnetic yoke includes a body, the body is an open-mouth structure with an open bottom and closed circumferentially, the body of the upper magnetic yoke is provided with a guide hole one that matches the end of the piston rod of damper two, the inner wall of the top of the body is fixedly connected with an annular protrusion three, and the upper permanent magnet is fixed between the inner wall of the body and the annular protrusion three.

6. The near-zero stiffness energy-absorbing and vibration-damping takeoff and landing platform for aircraft according to claim 3, characterized in that, The lower housing includes a lower magnetic yoke. An annular protrusion four and an annular protrusion five are fixedly connected to one end of the lower magnetic yoke facing the cover plate. An annular protrusion five is located outside the annular protrusion four. The lower permanent magnet is fixedly connected between the annular protrusion four and the annular protrusion five. The annular protrusion five has a winding groove in its circumference that is compatible with the magnetic coil.

7. The near-zero stiffness energy-absorbing and vibration-damping takeoff and landing platform for aircraft according to claim 3, characterized in that, The damper has a threaded hole 1 at the bottom and a threaded hole 2 at the end of the piston rod of the damper. The threaded hole 2 is compatible with the internal hex bolt. A limit groove is provided on the inner wall of the top of the cover plate. The piston rod of the damper is fixedly connected with an annular protrusion 6 that is compatible with the limit groove.

8. The near-zero stiffness energy-absorbing and vibration-damping takeoff and landing platform for aircraft according to claim 5, characterized in that, The piston rod end of the second damper is provided with a threaded guide post 2, and a limiting block that matches the guide hole 1 is fixedly connected to the piston rod of the second damper. The bottom of the second damper is provided with a threaded hole 3.

9. The quasi-zero stiffness energy-absorbing and vibration-damping takeoff and landing platform for aircraft according to claim 6, characterized in that, The inner wall of the main body is provided with an annular groove, the washer is pressed into the annular groove, and several guide posts are fixedly connected to the annular protrusion in five directions. The upper magnetic yoke is provided with a guide groove in the circumference of the main body that matches the guide posts.

10. The quasi-zero stiffness energy-absorbing and vibration-damping takeoff and landing platform for aircraft according to claim 1, characterized in that, Used for take-off and landing of eVTOL aircraft.

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