All-electric main landing frame and unmanned aerial vehicle

Abstract

The invention provides an all-electric main landing frame and an unmanned aerial vehicle. The all-electric main landing frame comprises a self-adaptive magnetic resistance buffer, a folding inclined supporting rod, a retractable actuator, a torque arm assembly and an electric brake aircraft wheel. The damping force can be self-adjusted in real time according to the use scene condition of the unmanned aerial vehicle, the working rapidity, accuracy and stability of the unmanned aerial vehicle main landing pad are improved, and the unmanned aerial vehicle main landing pad has the advantages of being high in adaptive capacity, good in maintainability, high in integration degree and the like.

Description

Technical Field

[0001] The invention relates to a full-electric main landing gear and an unmanned aerial vehicle, belonging to the technical field of unmanned aerial vehicle structure design. Background Art

[0002] Drones have the advantages of light weight, large payload, high speed, and long endurance. They can operate in many dangerous and unknown areas and are currently widely used in battlefield reconnaissance, disaster relief and other fields. The launch and landing recovery of drones are key stages in the entire flight process. Among them, the main methods of drone recovery include wheeled taxiing landing, arresting net recovery, and parachute recovery. Considering the economy, safety and reliability, wheeled taxiing landing is generally used for drone recovery.

[0003] The main landing gear is not only an important load-bearing component of the UAV, but also one of the actuation systems with important operating characteristics. It realizes important functions such as landing gear retraction and extension, wheel braking and steering through a complex control system. At present, the main landing gear used in the field of UAVs is mostly hydraulic / pneumatic, that is, the main landing gear is driven to be retracted and deployed by hydraulic or pneumatic devices. However, hydraulic or pneumatic main landing gear usually requires the installation of power storage devices such as hydraulic pump-oil tank or air pump-air source and other auxiliary devices inside the UAV fuselage, which increases the overall weight and volume of the UAV and reduces the working efficiency and endurance of the UAV.

[0004] With the development of all-electric aircraft technology, the design of all-electric main landing gear is of great significance. Compared with the electric drive mode of all-electric UAVs, the above hydraulic or pneumatic drive modes have the risk of leakage of working medium (oil or gas), which brings hidden dangers to the normal operation of hydraulic / pneumatic systems, reduces the safety of UAVs, and is not conducive to the daily maintenance of UAVs, prolonging the maintenance inspection and preparation time before takeoff. Domestic and foreign research institutions have conducted different degrees of research on the landing gear system of all-electric aircraft. Among them, the United Kingdom has carried out the All-Electric Landing Gear Retraction (ELGEAR) project, taking the Airbus A320 aircraft landing gear as the research object and developing a fully electric design scheme; Hu Yugang and others from the Air Force Equipment Department of China briefly described the relevant research on the integration of the all-electric landing gear system in the article and proposed a preliminary design scheme; Xia Haotian and others from Nanjing University of Aeronautics and Astronautics conducted a design study on the electric turning mechanism of the front landing gear of the all-electric landing gear and optimized the swing performance of the front landing gear.

[0005] At present, the main landing gear used in the field of UAVs all adopts the traditional single-chamber oil-gas shock absorber structure to achieve the buffering and energy absorption effect. It has the advantages of simple structure and high stability. However, for UAVs, the take-off and landing scenes are varied, especially in military environments, rugged outdoor venues and large-scale impact and vibration conditions have more stringent requirements on the buffer device. In this case, the traditional oil-gas shock absorber cannot meet the use requirements of the landing gear of military UAVs in complex environments. When facing different degrees of impact and vibration, the damping force provided by the traditional oil-gas shock absorber is not much different, and the vibration amplitude fed back to the body is basically the same, which cannot play a good shock absorption effect for instantaneous large-scale impact and vibration.

[0006] Patent CN102162499A is a drum washing machine with a variable damping shock absorber, and proposes to change the fluidity of the magnetic fluid by controlling the current entering the electromagnet through a controller. Patent CN112145607A is a subway floating plate isolator based on magnetically controlled damping, and proposes to provide an excitation current to the excitation coil from the outside, and generate a corresponding magnetic field according to the magnitude of the excitation current. As the magnetic field changes, the shear yield stress of the magnetic fluid in the damping channel will change accordingly. The macroscopic manifestation is that the damping force of the subway floating plate isolator can be controlled by adjusting the magnitude of the excitation current. However, these adjustable damping forces are all based on the change of current given by the outside world. For drones, due to the changeable take-off and landing scenes, it is impossible to obtain the appropriate current in real time according to the actual situation of the drone, so as to adjust the damping force to meet the shock absorption requirements of the drone's main landing gear in the complex environment of the military field. Summary of the invention

[0007] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a fully electric main landing gear and UAV that can self-adjust the damping force in real time according to the usage scenario of the UAV, effectively improve the speed, accuracy and stability of the main landing gear system, and have strong adaptability, good maintainability and high integration.

[0008] The technical solution of the present invention is: an all-electric main landing gear, including an adaptive magnetic resistance buffer, a foldable diagonal support rod, a retractable actuator, a torque arm assembly and an electric brake wheel; The adaptive magnetic resistance buffer comprises a supporting outer cylinder, a piston rod, a machine wheel shaft, a plunger rod, a floating retaining ring, an excitation coil and a permanent magnet. The plunger rod is installed at the top of the inner cavity of the supporting outer cylinder, and the floating retaining ring is sleeved outside the plunger rod to divide the inner cavity of the supporting outer cylinder into an upper air cavity and a lower fluid cavity. An end cover with a damping hole is installed at the bottom of the inner cavity of the plunger rod, and a piston is installed on the top of the piston rod. The piston rod is sleeved outside the plunger rod from one end of the piston and can reciprocate along the plunger rod in the inner cavity of the supporting outer cylinder. A permanent magnet is arranged on the outer wall of the piston rod below the piston, and an excitation coil is arranged on the inner cavity wall of the supporting outer cylinder below the plunger rod, and an annular gap is formed between the permanent magnet and the excitation coil; the end of the piston rod away from the piston extends out of the supporting outer cylinder, and the machine wheel shaft is installed at the end of the extended end of the piston rod; the fluid cavity of the inner cavity of the supporting outer cylinder, the inner cavity of the plunger rod and the inner cavity of the piston rod are filled with magnetic fluid, and air with a certain pressure is sealed in the air cavity.

[0009] A UAV adopting any of the all-electric main landing gears, wherein the all-electric main landing gear mirror-mounted under the UAV is connected to the UAV fuselage through an adaptive magnetic resistance buffer and a foldable diagonal support rod.

[0010] The beneficial effects of the present invention compared with the prior art are as follows: (1) The present invention can self-adjust the damping force in real time according to the use scenario of the UAV, thereby improving the speed, accuracy and stability of the main landing gear of the UAV, and has the advantages of strong adaptability, good maintainability and high integration; (2) The adaptive reluctance buffer of the present invention adopts a magnetic fluid-air buffer structure. According to the difference in the external landing environment of the UAV or the intensity of the vibration during the landing process, the excitation current is adaptively adjusted to adjust the magnitude of the damping force and improve the performance of the main landing gear; (3) The present invention adopts fully electrified servo technology to control the retraction and extension of the main landing gear and the rotation speed of the wheels on both sides, and couples the adaptive magnetic resistance buffer, full electrification and UAV structure to achieve the adaptive buffering and shock absorption function of the fully electric main landing gear in complex take-off and landing conditions without changing the appearance size and function; (4) The present invention has a more compact layout, and the main components are integrated and installed on the main landing gear structure body, which can greatly save the internal space of the UAV fuselage and reduce the weight of the whole machine. The maintainability of the electric servo control is greatly improved, which can shorten the maintenance inspection and preparation time for the UAV take-off and landing, and is conducive to improving the work efficiency of the UAV. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a schematic diagram of the overall structure of a main landing gear of an all-electric UAV according to an embodiment of the present invention; Figure 2 It is a schematic diagram of the overall composition and a partial enlarged schematic diagram of an adaptive magnetoresistive buffer according to an embodiment of the present invention; FIG3 is a schematic structural diagram of a foldable diagonal brace according to an embodiment of the present invention, the left figure is before folding, and the right figure is after folding; Figure 4 This is a schematic diagram of the structure of a retractable actuator according to an embodiment of the present invention; Figure 5 This is a schematic diagram of the structure of a fully electric UAV main landing gear in a retracted state according to an embodiment of the present invention; Figure 6 This is a block diagram of the feedback regulation principle of an adaptive reluctance buffer according to an embodiment of the present invention; Among them, 1—adaptive reluctance buffer; 1-1—support outer cylinder; 1-2—piston rod; 1-3—wheel shaft; 1-4—plunger rod; 1-5—floating retaining ring; 1-6—excitation coil; 1-7—permanent magnet; 1-8—piston; 1-9—end cover; 1-10—guide seal assembly; 1-11—fluid channel; 2—foldable diagonal support rod; 2-1—connecting rod; 2-2—upper support rod; 2-3—support rod lock; 2-4—locking spring; 2-5—in-place switch; 2-6—lower support rod; 3—retractable actuator; 3-1—servo motor; 3-2—transmission and control assembly; 3-3—actuator rod; 4—torque arm assembly; 4-1—upper torque arm; 4-2—lower torque arm; 5—electric brake wheel; 5-1—wheel; 5-2—electric brake device; 6—UAV fuselage. DETAILED DESCRIPTION

[0012] The present invention is described in detail below with reference to specific examples and accompanying drawings.

[0013] The invention provides a full-electric UAV main landing frame, comprising an adaptive magnetic resistance buffer, a foldable diagonal support rod, a retractable actuator, a torque arm assembly and an electric brake wheel.

[0014] The adaptive magnetic resistance buffer comprises a supporting outer cylinder, a piston rod, a machine wheel shaft, a plunger rod, a floating retaining ring, an excitation coil and a permanent magnet. The plunger rod is installed at the top of the inner cavity of the supporting outer cylinder, and the floating retaining ring is sleeved outside the plunger rod to divide the inner cavity of the supporting outer cylinder into an upper air cavity and a lower fluid cavity. An end cover with a damping hole is installed at the bottom of the inner cavity of the plunger rod, and a piston is installed on the top of the piston rod. The piston rod is sleeved outside the plunger rod from one end of the piston and can reciprocate along the plunger rod in the inner cavity of the supporting outer cylinder. A permanent magnet is arranged on the outer wall of the piston rod below the piston, and an excitation coil is arranged on the inner cavity wall of the supporting outer cylinder below the plunger rod, and an annular gap is formed between the permanent magnet and the excitation coil; the end of the piston rod away from the piston extends out of the supporting outer cylinder, and the machine wheel shaft is installed at the end of the extended end of the piston rod; the fluid cavity of the inner cavity of the supporting outer cylinder, the inner cavity of the plunger rod and the inner cavity of the piston rod are filled with magnetic fluid, and air with a certain pressure is sealed in the air cavity.

[0015] The top end of the supporting outer cylinder shell is connected to one end of the retractable actuator, the other end of the retractable actuator is connected to the foldable diagonal support rod, the other end of the foldable diagonal support rod is connected to the bottom of the supporting outer cylinder shell, one end of the torque arm assembly is connected to the bottom of the supporting outer cylinder shell, and the other end is connected to the extended end of the piston rod. When the piston rod reciprocates, the torque arm assembly opens and closes a certain angle, and the piston rod is connected to the electric brake wheel through the wheel shaft.

[0016] Furthermore, the adaptive reluctance buffer of the present invention introduces the reciprocating speed of the piston rod into the damping force feedback. The reciprocating speed of the piston rod adaptively changes according to the landing environment. The reciprocating speed of the piston rod causes the mutual speed between the permanent magnet and the excitation coil to adaptively change, thereby changing the magnitude of the excitation current. The viscosity of the magnetic fluid adaptively changes according to the change of the excitation current, ultimately causing an adaptive change in the damping force.

[0017] Furthermore, the plunger rod of the present invention is processed with a fluid channel on the wall surface close to the end cover. Preferably, the fluid channel is an annular groove or a through hole evenly distributed in the circumferential direction of the plunger rod.

[0018] Furthermore, a guide seal assembly is installed on the outer side of the piston, and the two cooperate to complete the reciprocating motion of the piston rod in the inner cavity of the supporting outer cylinder.

[0019] Furthermore, a guide seal assembly is arranged inside the floating retaining ring, including a seal ring and a guide belt, which cooperate to enable the floating retaining ring to float freely up and down along the plunger rod in the inner cavity of the supporting outer tube. The floating retaining ring is a boundary device between the air cavity and the fluid cavity.

[0020] There are two fluid media inside the adaptive reluctance buffer of the present invention, namely air and magnetic fluid. The air is enclosed between the supporting outer cylinder and the plunger rod and above the floating retaining ring, with a certain pressure, and is used as an air spring to absorb the external large instantaneous impact load.

[0021] Furthermore, the air pressure Calculated by the following formula:

[0022] in, is the landing gear sinking load (MPa); is the pressure action area of ​​the air cavity (m 2 ), which can be calculated based on the air cavity structure. Preferably, the recommended pressure value for small and medium-sized UAVs (buffer peak load does not exceed 50kN during landing) is between 1.2 and 2MPa.

[0023] The magnetic fluid of the present invention is a uniform mixture with fluidity and magnetism obtained by suspending magnetizable solid particles in a fluid and combining multiple additives. The magnetic fluid is enclosed in the fluid cavity below the floating retaining ring, the plunger rod cavity and the piston rod cavity, and works together with the damping hole to realize the adaptive damping force adjustment function inside the buffer.

[0024] Furthermore, the diameter of the damping hole It is calculated based on the load of the UAV during landing, the viscosity of the fluid medium, etc. The calculation formula is as follows:

[0025] in, is the magnetic fluid flow rate flowing through the damping hole (m 3 / s); is the original dynamic viscosity of the magnetic fluid (pa·s); is the length of the damping hole (m); is the fluid pressure difference on both sides of the damping hole (Pa).

[0026] Furthermore, the magnetic fluid may be an oil-based fluid or a water-based fluid, and more preferably a water-based fluid.

[0027] The retractable actuator of the present invention adopts full electric control, including a servo motor, a transmission and control component and an actuating rod; the transmission and control component includes a mechanical transmission component and a position measurement feedback device, and the output end of the servo motor is transmitted to the actuating rod through the mechanical transmission component to control the actuating rod to output linear displacement and force.

[0028] The retractable actuator of the present invention can accurately output linear displacement and force through PID control under the drive of a servo motor.

[0029] Furthermore, the servo motor adopts a permanent magnet synchronous motor, the mechanical transmission component adopts a ball screw pair and a gear, and the position measurement feedback device adopts a linear potentiometer.

[0030] The linear potentiometer of the present invention measures and feeds back the position of the all-electric main landing gear to the all-electric main landing gear controller. The all-electric main landing gear controller controls the output of the servo motor. The actuator rod is the output mechanism of the retractable actuator, and outputs linear displacement and force under the joint control of the servo motor and the transmission and control components.

[0031] The foldable diagonal strut of the present invention comprises a connecting rod, an upper strut, a strut lock, a locking spring, an in-position switch and a lower strut. The foldable diagonal strut is connected to the pin shaft of the retractable actuator through the connecting rod and is connected to the pin shaft of the supporting outer cylinder of the adaptive magnetic resistance buffer through the lower strut. The upper strut is connected to the lower strut through the pin shaft, and the pin shaft can be rotated to a certain angle to realize the folding and retracting of the all-electric main landing gear. The strut lock is arranged at the connection between the upper and lower struts, and is connected to the upper strut through the pin shaft. The two ends of the locking spring are respectively connected to the upper strut and the strut lock to provide pre-tightening force for locking the strut lock. The in-position switch detects whether the foldable diagonal strut is locked in place and feeds back to the all-electric main landing gear controller.

[0032] The torque arm assembly of the present invention comprises an upper torque arm and a lower torque arm, which are connected by a pin shaft and can be opened and closed at a certain angle. The upper torque arm is connected to support the lower end of the outer cylinder shell, and the lower torque arm is connected to the output end of the piston rod to suppress the swing of the wheel.

[0033] The electric brake wheel of the present invention comprises a wheel and an electric brake device, wherein the electric brake device comprises a brake disc, an electric actuator and a wheel speed sensor, receives a signal from an aircraft controller, and feeds back the braking amount in real time to complete active braking control of the wheel.

[0034] The designs of the foldable diagonal support rod, the torque arm assembly and the electric brake wheel of the present invention can refer to the prior art.

[0035] When the present invention is working, the aircraft controller drives the retractable actuator to extend and retract to drive the diagonal support rod to fold or unfold, thereby completing the folding and unfolding action of the main landing gear. The adaptive magnetic resistance buffer can actively adjust the internal damping force according to the vibration intensity during landing, thereby reducing the impact on the UAV landing.

[0036] The present invention also provides a UAV using the above-mentioned all-electric main landing gear, wherein the all-electric main landing gear mirror-mounted under the UAV is connected to the UAV fuselage through an adaptive magnetic resistance buffer and a foldable diagonal support rod.

[0037] Furthermore, a hook is provided at the protruding end of the piston rod of the adaptive reluctance buffer, and when the all-electric main landing gear is folded, it is connected to the UAV through the hook.

[0038] Furthermore, the two wheels of the mirror-mounted all-electric main landing gear achieve the steering action of the drone through differential control.

[0039] In order to make the technical solutions and advantages of the present invention more clearly understood, the exemplary embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than an exhaustive list of all the embodiments. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0040] Figure 1, 5 The diagram schematically shows the deployment and folding of a main landing gear of an all-electric UAV according to an embodiment of the present invention, which includes an adaptive magnetic resistance buffer 1, a foldable diagonal support rod 2, a retractable actuator 3, a torque arm assembly 4, and an electric brake wheel 5.

[0041] Further, in one embodiment, if Figure 1 and 2 As shown, the adaptive reluctance buffer includes a supporting outer cylinder 1-1, a piston rod 1-2, a machine wheel shaft 1-3, a plunger rod 1-4, a floating retaining ring 1-5, an excitation coil 1-6, a permanent magnet 1-7, 1-8—a piston, 1-9—an end cover, 1-10—a guide seal assembly, and 1-11—a fluid channel.

[0042] Two pins are arranged on the top of the outer shell of the supporting outer cylinder 1-1 and connected to the UAV fuselage 6, playing a bearing role and transmitting the sinking load and speed of the UAV during landing to the adaptive magnetic resistance buffer.

[0043] The piston rod 1-2 is equipped with a piston 1-8 and a guide seal assembly 1-10. The piston rod 1-2 reciprocates in the inner cavity of the supporting outer cylinder. The fluid medium in the piston rod cavity flows to the upper plunger rod cavity through the damping hole C. In a preferred embodiment, the diameter of the damping hole C is It needs to be calculated based on the load of the drone when it lands, the viscosity of the fluid medium, etc. The calculation formula is:

[0044] in, is the magnetic fluid flow rate flowing through the damping hole (m 3 / s); is the original dynamic viscosity of the magnetic fluid (pa·s); is the length of the damping hole (m); is the fluid pressure difference on both sides of the damping hole (Pa).

[0045] In a preferred embodiment, a smaller damping hole diameter can be obtained by using the initial dynamic viscosity value of the magnetic fluid when not affected by a magnetic field as a calculation input. When the buffer is working, the fluid dynamic viscosity of the magnetic fluid gradually increases, and the damping effect can be better achieved with a smaller damping hole.

[0046] In a preferred embodiment, the top end of the plunger rod 1-4 is fixedly connected to the supporting outer tube 1-1 of the buffer, and the bottom of the plunger rod 1-4 is threadedly mounted with an end cover 1-9 with a damping hole C. The plunger rod 1-4 provides a guide for the reciprocating motion of the floating retaining ring 1-5 and the piston rod 1-2.

[0047] In a preferred embodiment, the floating retaining ring 1-5 is mounted on the plunger rod 1-4 and can float freely up and down, and is a boundary device between the air cavity and the fluid cavity. There are two fluid media inside the adaptive reluctance buffer 1, namely air A and magnetic fluid B. The air A is enclosed outside the plunger rod 1-4 and above the floating retaining ring 1-5, and is used as an air spring to absorb large external instantaneous impact loads.

[0048] Air A should have a certain pressure when injected into the buffer , the specific calculation and evaluation needs to be carried out according to the parameters such as the sinking load when the UAV lands. The calculation formula is: in, is the landing gear sinking load (MPa); is the pressure action area of ​​the air cavity (m 2 ), which can be calculated based on the air cavity structure. For small and medium-sized UAVs (the peak load of the buffer during landing does not exceed 50kN), the recommended pressure value is between 1.2 and 2MPa.

[0049] Magnetic fluid B is a uniform mixture with fluidity and magnetism obtained by suspending magnetizable solid particles in fluid and combining with various additives. It is enclosed in all cavities under the floating retaining rings 1-5 and works together with the damping hole C to realize the adaptive damping force adjustment function inside the buffer.

[0050] The magnetic fluid B is divided into two categories according to the type of fluid: oil-based fluid and water-based fluid. In a preferred embodiment, considering factors such as environmental protection and economy, a water-based magnetic fluid, i.e., a magnetic fluid composed of water + magnetic nanoparticles, is selected as the fluid medium inside the adaptive magnetic resistance buffer 1. It is recommended to use a magnetic fluid with a product code of MRF-240BS, which has an operating temperature of 0 to 70°C and a density of 3.818 g / cm 3 .

[0051] In a preferred embodiment, the excitation coil 1-6 is embedded on the inner wall of the outer cylinder below the plunger rod 1-4, and the permanent magnet 1-7 is embedded and fixed on the outside of the piston rod 1-2, forming an annular gap E between the two for excitation and conduction of the induction current.

[0052] When the piston rod 1-2 reciprocates, the permanent magnet 1-7 fixed thereon will move relative to the excitation coil 1-6, generating a self-excited excitation current, which is transmitted to the magnetic fluid B through the annular gap E. Under the action of the excitation current, the fluid dynamic viscosity of the magnetic fluid itself increases. will become larger, according to the calculation formula of the damping force inside the buffer It can be seen that if the speed v of the reciprocating motion of the piston rod 1-2 remains unchanged, The larger the size, the greater the viscous resistance coefficient b of the entire buffer damping system, and thus the damping force F provided by the buffer will increase. Based on this, when the main landing gear encounters external vibration conditions, first, the pressurized air A in the air cavity acting as a spring will be compressed to absorb part of the energy generated by the impact vibration; secondly, the magnetic fluid B inside the adaptive reluctance buffer 1 flows through the fixed-size damping hole C under the push of the piston rod 1-2. The damping force generated in this process will convert most of the impact vibration energy into internal energy and consume it. In the process of continuous reciprocating motion, the damping system will gradually consume the external vibration energy, thereby keeping the drone fuselage 6 stable. When the main landing gear encounters severe impact or vibration, the reciprocating speed of the piston rod increases, so that the permanent magnet 1-7 will increase the excitation current generated by the excitation coil 1-6, thereby increasing the dynamic viscosity of the magnetic fluid B, and then the adaptive reluctance buffer 1 can provide a greater damping force and achieve a better buffering and shock absorption effect.

[0053] The magnitude of the excitation current depends on the relative movement speed between the permanent magnet 1-7 and the excitation coil 1-6, as well as the magnetic induction intensity of the permanent magnet. When the main landing gear of the present invention is working, the excitation current generated is itself a feedback quantity, which has a certain regulating effect on the damping force of the buffer. The feedback regulation principle is as follows: Figure 6 As shown: Feedback adjustment process: When the piston rod 1-2 is subjected to strong external vibration, the relative speed between the permanent magnet 1-7 and the excitation coil 1-6 will increase, and the excitation current will also increase accordingly, so the damping force generated by it will also increase accordingly, and the vibration reduction effect of the buffer will be enhanced, which can reduce the vibration of the piston rod 1-2; conversely, when the piston rod 1-2 is subjected to weak external vibration, the relative speed between the permanent magnet 1-7 and the excitation coil 1-6 will be relatively small, and the excitation current will also be relatively small, so the damping force generated by it will also be relatively small. The buffer mainly relies on the compressibility of air A and the damping force generated by the magnetic fluid B when it flows through the fixed-size damping hole C to slow down and offset external vibrations and promote the smooth movement of the drone fuselage 6.

[0054] Based on the above principle, the excitation current in the adaptive reluctance buffer 1 plays a certain role in regulating the damping force of the buffer as a whole, and can adaptively change the shock absorption effect of the buffer according to the vibration intensity under different landing environments.

[0055] In a preferred embodiment, the foldable diagonal brace 2 is as follows Figure 3 As shown, it includes a connecting rod 2-1, an upper support rod 2-2, a support rod lock 2-3, a locking spring 2-4, an in-position switch 2-5 and a lower support rod 2-6.

[0056] The two ends of the foldable diagonal strut 2 are respectively connected to the fuselage 6 and the supporting outer cylinder 1-1 of the adaptive magnetic resistance buffer 1. The connecting rod 2-1 connects the foldable diagonal strut 2 and the retractable actuator 3 through a pin shaft; the upper strut 2-2 and the lower strut 2-6 are connected through a pin shaft to achieve rotation; the strut lock 2-3 is set at the connection between the upper and lower struts, and is connected to the upper strut 2-2 through a pin shaft; the two ends of the locking spring 2-4 are respectively connected to the upper strut 2-2 and the strut lock 2-3 to provide pre-tightening force for the locking of the diagonal strut; the in-position switch 2-5 detects whether the foldable diagonal strut 2 is locked in place through the contact voltage measurement principle and feeds back to the controller.

[0057] In order to reduce the overall weight of the main landing gear, a structural topology optimization simulation was performed on the foldable diagonal strut 2, and a lightweight design was achieved without affecting the load-bearing capacity.

[0058] In a preferred embodiment, the retractable actuator 3 is as follows Figure 4 As shown, it includes a servo motor 3-1, a transmission and control component 3-2, and an actuator rod 3-3. The servo motor 3-1 is a small permanent magnet synchronous motor; the transmission and control component 3-2 mainly includes a ball screw pair and gears for mechanical transmission, and a linear potentiometer for position measurement and feedback; the actuator rod 3-3 is the output mechanism of the retractable actuator 3, and outputs linear displacement and force under the joint control of the servo motor 3-1 and the transmission and control component 3-2.

[0059] The retractable actuator 3 is the key actuating component for the main landing gear to achieve the retracting and deploying actions, so its reliability needs to be verified. A strength check simulation analysis is performed on it to verify that its overall structure, especially the design of the actuator rod 3-3, meets the load requirements.

[0060] In a preferred embodiment, the torque arm assembly 4 is as follows Figure 1 , 5 As shown, it includes an upper torque arm 4-1 and a lower torque arm 4-2, which are connected by a pin shaft and can be opened and closed at a certain angle. The two ends are respectively connected to the supporting outer cylinder 1-1 and the protruding end of the piston rod 1-2 to suppress the wheel swing.

[0061] In a preferred embodiment, the electric brake wheel 5 is as follows Figure 1 , 5 As shown, it includes a wheel 5-1 and an electric brake device 5-2. The electric brake device 5-2 is composed of a brake disc, an electric actuator, a wheel speed sensor, etc. It can receive the signal from the drone controller and provide real-time feedback on the braking amount, thereby completing the active braking control of the wheel 5-1. The wheels on both sides of the main landing gear have normal braking, emergency braking, differential braking, differential steering, parking braking, fault self-detection and other functions.

[0062] The main landing gear of an all-electric UAV proposed in the present invention is driven and controlled by an all-electric device to realize the deployment of the main landing gear (such as Figure 1 as shown) and collapsed (as Figure 5 As shown in the figure), as well as differential steering control and braking control of the wheels; utilizing the variable magnetic resistance characteristics of the magnetic fluid, the viscosity of the magnetic fluid is changed through the self-excited current sensing device inside the buffer, and then the damping force of the buffer is adaptively adjusted, thereby improving the working characteristics of the main landing gear of the UAV under different operating conditions and improving the working efficiency of the main landing gear system.

[0063] The embodiments described above are only descriptions of the preferred implementation modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

[0064] Parts of the present invention that are not described in detail are well known to those skilled in the art.

Claims

1. An all-electric main landing gear, characterized in that: Includes adaptive reluctance buffer, folding diagonal brace, retractable actuator, torque arm assembly and electric brake wheel; The adaptive magnetic resistance buffer comprises a supporting outer cylinder, a piston rod, a wheel shaft, a plunger rod, a floating retaining ring, an excitation coil and a permanent magnet. The plunger rod is installed at the top of the inner cavity of the supporting outer cylinder, and the floating retaining ring is sleeved outside the plunger rod to divide the inner cavity of the supporting outer cylinder into an upper air cavity and a lower fluid cavity. An end cover with a damping hole is installed at the bottom of the inner cavity of the plunger rod, and a piston is installed on the top of the piston rod. The piston rod is sleeved outside the plunger rod from one end of the piston and can reciprocate along the plunger rod in the inner cavity of the supporting outer cylinder. A permanent magnet is arranged on the outer wall of the piston rod below the piston, and an excitation coil is arranged on the inner cavity wall of the supporting outer cylinder below the plunger rod, and an annular gap is formed between the permanent magnet and the excitation coil. The end of the piston rod away from the piston extends out of the supporting outer cylinder, and the end of the extended end of the piston rod is installed with a machine wheel axle; the fluid cavity of the supporting outer cylinder, the plunger rod cavity and the piston rod cavity are filled with magnetic fluid, and the air cavity is sealed with air with a certain pressure.

2. The all-electric main landing gear according to claim 1, characterized in that: The top end of the supporting outer cylinder shell is connected to one end of the retractable actuator, the other end of the retractable actuator is connected to the foldable diagonal support rod, the other end of the foldable diagonal support rod is connected to the bottom of the supporting outer cylinder shell, one end of the torque arm assembly is connected to the bottom of the supporting outer cylinder shell, and the other end is connected to the extended end of the piston rod. When the piston rod reciprocates, the torque arm assembly opens and closes a certain angle, and the piston rod is connected to the electric brake wheel through the wheel shaft.

3. The all-electric main landing gear according to claim 2, characterized in that: The retractable actuator is fully electrically controlled and includes a servo motor, a transmission and control assembly, and an actuator rod; the transmission and control assembly includes a mechanical transmission component and a position measurement feedback device, and the output end of the servo motor is transmitted to the actuator rod through the mechanical transmission component to control the actuator rod to output linear displacement and force.

4. The all-electric main landing gear according to claim 3, characterized in that: The adaptive reluctance buffer introduces the reciprocating speed of the piston rod into the damping force feedback. The reciprocating speed of the piston rod changes adaptively according to the landing environment. The reciprocating speed of the piston rod causes the mutual speed between the permanent magnet and the excitation coil to change adaptively, thereby changing the magnitude of the excitation current. The viscosity of the magnetic fluid changes adaptively according to the change of the excitation current, and finally causes the adaptive change of the damping force.

5. The all-electric main landing gear according to claim 4, characterized in that: The air pressure P 2 is calculated by the following formula, ,in, P is the landing gear sinking load, is the pressure action area of ​​the air cavity; the diameter of the damping hole The calculation formula is as follows, ,in, is the magnetic fluid flow rate flowing through the damping hole, is the original dynamic viscosity of the magnetic fluid, is the length of the damping hole, is the fluid pressure difference on both sides of the damping hole.

6. The all-electric main landing gear according to claim 5, characterized in that: The foldable diagonal strut includes a connecting rod, an upper strut, a strut lock, a locking spring, an in-place switch and a lower strut. The foldable diagonal strut is connected to the retractable actuator pin through the connecting rod and to the supporting outer cylinder pin of the adaptive magnetic resistance buffer through the lower strut. The upper strut is connected to the lower strut through a pin, and the pin can be rotated to a certain angle to realize the folding and retracting of the all-electric main landing gear. The strut lock is arranged at the connection between the upper and lower struts, and is connected to the upper strut through a pin. The two ends of the locking spring are respectively connected to the upper strut and the strut lock to provide pre-tightening force for the locking of the strut lock. The in-place switch detects whether the foldable diagonal strut is locked in place and feeds back to the all-electric main landing gear controller.

7. The all-electric main landing gear according to claim 6, characterized in that: The torque arm assembly includes an upper torque arm and a lower torque arm, which are connected by a pin shaft and can be opened and closed at a certain angle. The upper torque arm is connected to the lower end of the outer shell of the supporting outer cylinder, and the lower torque arm is connected to the output end of the piston rod; The electric brake wheel comprises a wheel and an electric brake device. The electric brake device receives a signal from an aircraft controller and feeds back the braking amount in real time to complete active brake control of the wheel.

8. The all-electric main landing gear according to claim 7, characterized in that: The plunger rod is processed with a fluid channel on the wall surface close to the end cover, a guide seal assembly is installed on the outside of the piston, and a guide seal assembly is arranged inside the floating retaining ring.

9. The all-electric main landing gear according to claim 8, characterized in that: The fluid channel is an annular groove or a through hole evenly distributed in the circumferential direction of the plunger rod.

10. An unmanned aerial vehicle using the all-electric main landing gear as described in any one of claims 1 to 9, wherein the all-electric main landing gear mirror-mounted under the unmanned aerial vehicle is connected to the unmanned aerial vehicle fuselage through an adaptive magnetic resistance buffer and a foldable diagonal support rod.

11. The drone according to claim 10, characterized in that: A hook is arranged at the extended end of the piston rod of the adaptive magnetic resistance buffer, and when the all-electric main landing gear is folded up, it is connected to the UAV through the hook.

12. The drone according to claim 10, characterized in that: The two electric brake wheels of the mirror-image-arranged all-electric main landing gear realize the steering action of the UAV through differential control.

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