A micro folding unmanned aerial vehicle

Abstract

A kind of micro folding unmanned aerial vehicle, there are landing gear springs between each landing gear and arm, and there are arm springs between arm joints and arms. The unmanned aerial vehicle has enough tension in the working state through the spring, which ensures the stability of the unmanned aerial vehicle structure and prevents damage due to excessive stretching. The optimized spring installation position makes the arm spring and landing gear spring in the folded state have small deflection, and the arm and landing gear will not deviate from the folded position due to small tension. During the unfolding process, the spring mounting column spacing increment is less than the maximum spring deflection, which will not be damaged due to excessive stretching. When the unmanned aerial vehicle is in flight, the spacing of the spring mounting column makes the torque of the tension generated by the spring on the arm shaft greater than the maximum counter-torque generated by the motor and rotor during flight, and the arm remains unfolded during work. The invention avoids the weight increase caused by complex structure; the arm and landing gear can be pulled by the spring tension in the unfolded and folded states to fix the position, so they will not shake with flight, ensuring flight stability.

Description

A miniature folding drone Technical Field

[0001] This invention relates to the field of drone technology, specifically a micro-sized folding drone. Background Technology

[0002] A drone is an unmanned aerial vehicle that flies using radio remote control or its own built-in programs. Quadcopter drones are characterized by good hovering performance, simple structure, high reliability, and simple control laws. Currently, quadcopter drones have been developed into products of various sizes and functions. Micro-miniature drones refer to remotely piloted aircraft weighing less than 0.25 kg, designed to meet the following performance requirements: a flight altitude not exceeding 50 meters, a maximum flight speed not exceeding 40 km / h, and radio transmission equipment that meets the technical requirements for low-power short-range radio transmission equipment. These types of drones are mainly used in the consumer market and scientific research and development, including aerial photography drones and racing drones.

[0003] Traditional quadcopter drones have fixed rotors, arms, and landing gear, resulting in large structural dimensions, inconvenience in carrying, susceptibility to damage during transport, and hindering portable and miniaturized design. Existing technologies offer several improvements to address these issues. Utility model patent CN210852883U uses a square duct to surround and support the motor and rotor, with the duct connected to the square fuselage via hinges for downward folding. However, this design is complex and heavy, hindering improved flight time and miniaturization; furthermore, the duct structure cannot fit snugly against the fuselage after folding, increasing the aircraft's longitudinal dimensions. Utility model patent CN218258683U features folding arms with a large rotation angle, allowing the arms to fold in the same direction as the drone, reducing the folded size. However, this design is only suitable for drones with short arms and long fuselages; otherwise, the folded arms will extend too far beyond the fuselage, significantly increasing the drone's length. In the utility model patent with announcement number CN209521858U, a design with a disc-shaped fuselage and arc-shaped folding arms is used. The arms fold to fit snugly against the fuselage, forming a disc-shaped shape. However, the arc length of the arms cannot exceed one-quarter of the fuselage circumference, limiting the drone's wheelbase to the fuselage size and making it difficult to install large rotors. Furthermore, compared to straight arms, the arc-shaped arms are structurally more complex and heavier. In the utility model patent with announcement number CN205738048U, the connection points between the arms and the fuselage are located at both ends of a flat fuselage. The arms fold to fit snugly against the sides of the fuselage. Because the folded arms are on the same plane, the arm length is limited, preventing the installation of larger rotors. Additionally, the landing gear lacks a folding function, preventing the overall height from being reduced by folding.

[0004] The patents mentioned above mostly use folding mechanisms made of metal and large-sized fuselages. At the same time, the number of foldable parts is limited, which can only achieve a small size reduction effect and fail to fully realize the folding potential of quadcopters. Furthermore, the use of a lot of metal mechanisms makes the weight large, making it difficult to apply to micro and small drones. Summary of the Invention

[0005] To overcome the problems of existing technologies, such as complex structure, large weight, limited folding degree, and difficulty in application to micro and small drones, this invention proposes a micro and small folding drone.

[0006] This invention includes a fuselage, arms, a power unit, and landing gear. Four arms are mounted on the fuselage: a left front arm, a right front arm, a left rear arm, and a right rear arm. The connecting ends of each arm are hinged to arm joints located on the fuselage. A power unit is mounted on the upper surface of the cantilever end of each arm. Landing gear is hinged to the lower surface of the cantilever end of each arm.

[0007] In this invention, the hinge coordinates of each arm joint are as follows: left front arm (41mm, -28mm, -13mm), right front arm (41mm, 28mm, -13mm), left rear arm (88mm, -28mm, 9mm), and right rear arm (88mm, 28mm, 9mm). When deployed, each of the left front arm, right front arm, left rear arm, and right rear arm points to the left front, right front, left rear, and right rear of the fuselage at 45°, respectively.

[0008] There is a spring fixing post for installing the arm spring on the arm joint and the arm respectively. The arm spring is located below the arm joint and the arm, with one end of the arm spring hooked on the arm joint spring fixing post on the lower surface of the arm joint and the other end hooked on the arm spring fixing post on the lower surface of the arm.

[0009] Each arm is slatted, with its upper and lower surfaces parallel to each other. Each arm consists of two horizontal planes and an inclined plane connecting these two horizontal planes to allow for clearance between the front and rear arms and between the arms and the landing gear during folding. One end of each arm is a hinged connection to an arm joint, and the other end is a cantilever end. Each cantilever end has a circular power unit mounting slot on its upper surface, where the power unit is installed. The lower surface of each arm at the end with the power unit mounting slot is a plane, which is the bottom surface of the arm. Each power unit mounting slot has a protrusion at its edge, adjacent to the landing gear pivot mounting hole of each arm; this protrusion serves as a landing gear deployment limiting block. The bottom surface of the arm also has protrusions, each with a landing gear pivot mounting hole, with the centerline of each landing gear pivot mounting hole spatially perpendicular to the centerline of the power unit mounting slot. Each boom has a connection hole at its connecting end, with the center line of each connection hole parallel to the center line of the power unit mounting slot. Each boom has a spring-loaded retaining post on the side where it connects to the landing gear.

[0010] There are four arm joints, symmetrically distributed in two groups on both sides of the fuselage, forming a left front arm joint, a right front arm joint, a left rear arm joint, and a right rear arm joint. The left and right front arms, located at the front of the fuselage, are positioned below the horizontal plane of the right-hand coordinate system's X-axis, while the left and right rear arms, also located at the front of the fuselage, are positioned above the horizontal plane of the right-hand coordinate system's X-axis. This allows the front and rear arms on the same side of the fuselage to fold and retract simultaneously to the side of the fuselage. The specific position coordinates of each arm joint on both sides of the fuselage satisfy the hinge coordinates of the corresponding arm.

[0011] The arm joint has a U-shaped arm mounting groove on its end face. Coaxial joint shaft mounting holes are located on the upper and lower sides of the groove, through which the arms are hinged to the arm joint. The surface of the center of the bottom of the arm mounting groove is arc-shaped, with two flat surfaces at either end. The flat surface closer to the body serves as the arm folding limiting surface, and the flat surface further away from the body serves as the arm unfolding limiting surface. A wiring groove is located on the bottom surface of the arm mounting groove to accommodate motor wires after the arm is unfolded.

[0012] A landing gear spring is located between the landing gear and the same side surface of the arm. One end of the landing gear spring is fixed to an arm spring retaining post on the arm, and the other end is fixed to a landing gear spring retaining post on the landing gear. During flight, the distance between the spring retaining post on the arm and the landing gear spring retaining post on the landing gear is 24 mm, and the landing gear spring provides a tension of 0.408 N. During deployment, as the arm extends, the maximum distance between the spring retaining post on the arm and the spring retaining post on the landing gear is 26 mm, with a deflection of 6 mm. During folding, as the arm retracts, the distance between the two spring retaining posts is 21 mm, and the landing gear spring provides a tension of 0.204 N, allowing the landing gear to be fixed in the folded position.

[0013] The landing gear spring has a circular cross-section, a wire diameter of 0.2 mm, a wire diameter of 2 mm, a length of 18 mm, 60 coils, and retaining lugs at both ends. The maximum load of this landing gear spring is 2.51 N, the maximum deflection is 31.3 mm, and the spring constant is 0.068 N / mm.

[0014] There is a spring fixing post for mounting the boom spring on both the boom joint and the boom. The distance between the spring fixing post on the boom and the mounting hole of the joint shaft is 21mm, and the distance between the spring fixing post on the boom joint and the mounting hole of the joint shaft is 10mm. The boom spring is located below the boom joint and the boom, with one end hooked onto the boom spring fixing post on the lower surface of the boom joint, and the other end hooked onto the boom spring fixing post on the lower surface of the boom.

[0015] The arm spring is a tension spring with a wire diameter of 0.4mm, a wire diameter of 4mm, a length of 20mm, and 60 coils. It is made of 304 stainless steel wire with a circular cross-section and has fixing lugs at both ends. The arm spring has a maximum load of 3.85N, a maximum deflection of 23.9mm, and a spring constant of 0.136N / mm.

[0016] There is a landing gear spring between each of the landing gears and the boom, and one end of the landing gear spring is fixed to a spring fixing post located on the boom, and the other end is fixed to a landing gear spring fixing post located on the landing gear.

[0017] The landing gear spring has a wire diameter of 0.2mm, a diameter of 2mm, and a length of 18mm.

[0018] The landing gear is slatted, with its upper and lower surfaces parallel to each other. Functionally, each landing gear has a connecting section at one end and a support section at the other. There is a 20° angle between the connecting section and the support section. Each connecting section has a landing gear pivot mounting hole at its end. The landing gear pivot passes through this hole and is inserted into the arm landing gear pivot mounting hole, thereby hinged each landing gear to the lower surface of the arm. Landing gear spring retaining posts are located on the side surface of each landing gear.

[0019] When the landing gear opens outwards, it forms a 130° angle with the bottom surface of the arm.

[0020] When the drone is in a folded state, the four arms are folded and attached to the side surface of the fuselage at their respective positions; the landing gear is folded and attached to the outside of the arms.

[0021] In this invention, arm pivot joints are arranged on the outer surfaces of the left and right sides of the fuselage; there are four arms, each mounted on one of the arm pivot joints; the power unit includes a brushless motor and a folding propeller, with each power unit mounted on the outer end of each arm; the landing gear is mounted on the outer end of each arm; the mounting device is arranged at the bottom of the fuselage and fixedly connected to the fuselage. Each arm has an arm pivot mounting hole at one end, and the upper surface of the other end is used to mount the power unit, while the lower surface has an arm landing gear pivot mounting hole; an arm spring connects the arm and the landing gear.

[0022] The proposed solution enables small, heavy-duty drones to be fully folded, resulting in a compact and portable size. It employs a simple folding design, avoiding the added weight associated with complex structures. The elimination of metal folding mechanisms further reduces the drone's weight. The arms and landing gear are held in place by spring tension in both unfolded and folded states, preventing swaying during flight and ensuring flight stability. This invention utilizes lightweight, small-sized springs and structural components to form the arm and landing gear folding mechanism, overcoming the problems of existing folding quadcopter drone designs, such as complex structures, large folded dimensions, heavy metal folding mechanisms, and difficulty in application to micro- and small drones. As shown in Figure 19, when the micro- and small folding drone is placed on the ground, the landing gear can lift it off the ground to a certain height, providing sufficient space at the bottom of the drone's mounting device to accommodate the load.

[0023] The springs selected in this invention possess appropriate spring constants and maximum deflection, providing sufficient tension to maintain structural stability of the UAV in operational mode, while preventing damage from excessive stretching during deployment. The spring mounting post positions ensure that the arm springs and landing gear springs have minimal deflection when the UAV is folded, providing minimal tension to prevent the arms and landing gear from deviating from their folded positions. During UAV deployment, the increase in the spacing between the spring mounting posts will not exceed the maximum spring deflection, preventing damage from excessive stretching. When the UAV is deployed and in flight, the spacing between the spring mounting posts ensures that the torque generated by the spring tension on the arm pivot is greater than the maximum counter-torque generated by the motor and rotor during UAV flight, allowing the UAV arms to maintain their deployed position during operation. Attached Figure Description

[0024] Figure 1 is a schematic diagram of the overall structure of the present invention in its unfolded state.

[0025] Figure 2 is a schematic diagram of the overall structure of the present invention in its folded state.

[0026] Figure 3 is a side view of the fuselage.

[0027] Figure 4 is a schematic diagram of the boom and boom joint structure when the boom is deployed.

[0028] Figure 5 is a structural schematic diagram of the boom joint; Figure 5 shows the boom joint as viewed from the left front and downward at an angle.

[0029] Figure 6 is a structural schematic diagram of the boom joint from another perspective; Figure 6 shows the boom joint as seen from the left front of the machine head at an angle.

[0030] Figure 7 is an exploded view of the machine arm joint, machine arm, machine arm spring, and machine arm shaft.

[0031] Figure 8 is an exploded view from a bottom angle of the boom joint, boom, boom spring, and boom shaft.

[0032] Figure 9 is a bottom view of the machine arm when it is folded.

[0033] Figure 10 is a bottom view of the machine arm folded to be perpendicular to the fuselage.

[0034] Figure 11 is a bottom view of the machine arm when it is extended.

[0035] Figure 12 is a schematic diagram of the landing gear and fuselage arm structure when the landing gear is deployed.

[0036] Figure 13 is a structural schematic diagram of the landing gear and fuselage arms from a bottom-up perspective when the landing gear is deployed.

[0037] Figure 14 is an exploded view of the landing gear and fuselage arms when the landing gear is deployed.

[0038] Figure 15 is an exploded view of the landing gear and fuselage arms from a low angle when the landing gear is deployed.

[0039] Figure 16 is a side view of the landing gear when folded.

[0040] Figure 17 is a side view of the landing gear when it is rotated to the maximum length of the landing gear springs.

[0041] Figure 18 is a side view of the landing gear when deployed.

[0042] Figure 19 is a side view of the present invention when a load is attached.

[0043] In the diagram: 1. Fuselage; 2. Arm; 3. Power unit; 4. Landing gear; 11. Arm joint; 111. Joint shaft mounting hole; 112. Arm mounting slot; 113. Arm folding limiting surface; 114. Arm unfolding limiting surface; 115. Cable routing groove; 12. Spring fixing post; 13. Loader; 21. Arm spring; 22. Arm shaft; 23. Inner side of arm; 24. Outer side of arm; 25. Arm shaft mounting hole; 26. Landing gear unfolding limiting block; 27. Arm landing gear shaft mounting hole; 28. Bottom surface of arm; 31. Folding rotor; 32. Motor; 41. Landing gear spring; 42. Landing gear shaft; 43. Landing gear shaft mounting hole; 44. Outer surface of landing gear; 45. Inner surface of landing gear; 51. Unmanned aerial vehicle (UAV); 52. Payload. Detailed Implementation

[0044] This embodiment describes a miniature foldable drone that can reduce its size when folded for storage and has a quick-mounting function. The drone has a symmetrical layout, with its flight direction facing forward; the two sides facing the flight direction are the left and right sides of the fuselage, respectively. The top of the drone's nose is taken as the reference point O. A right-handed coordinate system describing the drone's geometric parameters is established with this reference point O as the origin. The X-axis lies within the drone's plane of symmetry, with its positive direction pointing towards the rear of the drone along the fuselage direction. The Z-axis lies within the drone's plane of symmetry, with its positive direction perpendicular to the X-axis and pointing towards the top of the fuselage. The Y-axis is perpendicular to the XZ plane, pointing towards the right side of the drone's fuselage and satisfying the right-hand rule.

[0045] This embodiment includes a fuselage 1, arms 2, a power unit 3, and landing gear 4. Four arms 2 are mounted on the fuselage 1: a left front arm, a right front arm, a left rear arm, and a right rear arm. The connecting ends of each arm are hinged to arm joints 11 located on the fuselage. The hinge coordinates of each arm joint are as follows: left front arm (41mm, -28mm, -13mm), right front arm (41mm, 28mm, -13mm), left rear arm (88mm, -28mm, 9mm), and right rear arm (88mm, 28mm, 9mm). When deployed, the left front arm, right front arm, left rear arm, and right rear arm point 45° to the left front, 45° to the right front, 45° to the left rear, and 45° to the right rear of the fuselage, respectively.

[0046] A power unit 3 is installed on the upper surface of each cantilever end of the arm. A landing gear 4 is hinged to the lower surface of the cantilever end of each arm 2. When deployed, the landing gear 4 opens outward and forms a 130° angle with the bottom surface of the arm, which increases the contact area between the UAV and the ground and makes it more stable during takeoff and landing.

[0047] When the drone is in a folded state, the four arms 2 fold and fit against the side surfaces of the fuselage at their respective locations, and the landing gear 4 folds and fits against the outer sides of the arms 2, resulting in a significant reduction in the size of the drone when folded, as shown in Figure 2.

[0048] Each of the aforementioned arms 2 is slatted, with its upper and lower surfaces parallel to each other. Each arm consists of two horizontal planes and an inclined plane connecting the two horizontal planes to ensure mutual clearance between the front and rear arms and between the arms and the landing gear during folding. One end of each arm is a hinged connection end to the arm joint 11, and the other end is a cantilever end. A circular power unit mounting slot is located on the upper surface of the cantilever end of each arm, and the power unit 3 is embedded in this slot. The lower surface of each arm at the end with the power unit mounting slot is a plane, which is the bottom surface 28 of the arm. A protrusion is located at the edge of the lower surface of each power unit mounting slot, and each protrusion is adjacent to the landing gear pivot mounting hole of each arm; the protrusion is a landing gear deployment limiting block 26. The bottom surface of the boom also has protrusions, each with a boom landing gear shaft mounting hole 27, the center line of each boom landing gear shaft mounting hole being perpendicular to the center line of the power unit mounting slot. Each boom connection end has a connection hole, the center line of which is parallel to the center line of the power unit mounting slot. Spring-loaded retaining posts 12 are located on the side surface of each boom connecting to the landing gear 4.

[0049] There are four arm joints 11, symmetrically distributed in two groups on both sides of the fuselage, forming a left front arm joint, a right front arm joint, a left rear arm joint, and a right rear arm joint. The left and right front arms, located at the front of the fuselage, are positioned below the horizontal plane of the right-hand coordinate system's X-axis, while the left and right rear arms are positioned above the horizontal plane of the right-hand coordinate system's X-axis. This allows the front and rear arms on the same side of the fuselage to fold and retract simultaneously to the side of the fuselage. The specific position coordinates of each arm joint on both sides of the fuselage satisfy the hinge coordinates of the corresponding arm.

[0050] As shown in Figure 5, the end face of the arm connector 11 has a U-shaped arm mounting groove 112. Coaxial connector shaft mounting holes 111 are located on the upper and lower sides of the groove, allowing the arms to be hinged to the arm connector 11 via arm shafts 22. The connector shaft mounting holes 111 are used to mount the arm shafts 22, and their inner diameter is the same as the outer diameter of the arm shaft, both being 4mm. The surface of the middle part of the bottom of the arm mounting groove 112 is an arc surface, with two flat surfaces at its ends. The flat surface closer to the body is the arm folding limiting surface 113, and the flat surface further away from the body is the arm unfolding limiting surface 114. A wiring groove 115 is located on the bottom surface of the arm mounting groove to accommodate motor wires after the arm is unfolded.

[0051] A mounting frame 3 is fixed at the center of gravity of the aircraft on the lower surface of the fuselage 1, which is used to carry various mission payloads. By changing different mission payloads, the functionality of the UAV can be diversified.

[0052] Each arm has a spring fixing post 12 for mounting arm springs 21. The distance between the spring fixing post 12 on arm 2 and the joint shaft mounting hole 111 is 21mm, and the distance between the spring fixing post 12 on arm 11 and the joint shaft mounting hole 111 is 10mm. The arm spring 21 is located below the arm joint and arm 2, with one end hooked onto the arm spring fixing post 12 on the lower surface of the arm joint and the other end hooked onto the arm spring fixing post 12 on the lower surface of arm 2. Each arm has the same four arm springs. To meet the requirements of UAV flight conditions, the arm spring is a tension spring with a wire diameter of 0.4mm, a wire diameter of 4mm, a length of 20mm, and 60 coils. It is made of 304 stainless steel wire with a circular cross-section and has 3mm diameter lugs at both ends for fixing to the landing gear spring fixing posts. The arm spring has a maximum load of 3.85 N, a maximum deflection of 23.9 mm, and a spring constant of 0.136 N / mm. During flight, the torque generated by the arm spring on the arm shaft must be sufficient to counteract the counter-torque generated by the motor and rotor to maintain the arm's deployed state. Measurements show that the torque generated by the arm spring is 7.344 N·mm, while the counter-torque of the motor and rotor at maximum speed is 6.552 N·mm. This arm spring is sufficient to maintain the arm's deployment, allowing the UAV to operate normally during flight.

[0053] During operation, as the arm 2 rotates around the arm axis 22, the distance between the two arm spring fixing posts 12 first increases and then decreases, causing the length of the arm spring 21 connecting the two arm spring fixing posts to also first increase and then decrease. The arm spring is a tension spring, which is always in a stretched state after installation and provides tension. When the arm 2 is in the folded state as shown in Figure 9, the arm spring is at its minimum tension of 24mm, providing a small tension of 0.544N, making the inner side 23 of the arm 2 tightly adhere to the arm folding limiting surface 113 of the arm joint 11. Thus, the arm is fixed in the folded position under the action of the tension of the arm spring 21 and the support force provided by the arm folding limiting surface. During the outward unfolding of the arm, the arm spring will be gradually stretched; when the arm is in the position shown in Figure 10, where the arm is perpendicular to the body 1, the arm spring is at its maximum tension of 31mm, at which point the deflection is 11mm, which is less than the maximum deflection of the spring. As the arm continues to extend, under the tension of the arm spring 21, the arm 2 will rotate around the arm pivot 22 and reach the extended position shown in Figure 11. At this time, the arm spring is under moderate tension of 29mm, providing a moderate tension of 1.224N, so that the outer side 24 of the arm 2 is in close contact with the arm extension limiting surface 114 of the arm joint. Thus, the arm is fixed in the extended position under the tension of the arm spring and the support force provided by the arm extension limiting surface.

[0054] As shown in Figures 12 and 13, there are four power units 3, each including a pair of folding rotors 31 and a motor 32. The motors are mounted on the upper surface of the cantilever end of each arm; the pair of rotors are respectively mounted on each motor. After the motors are started, they drive the folding rotors to rotate, thereby generating lift and propelling the UAV into flight.

[0055] Each landing gear 4 is hinged to the arm 2 via a landing gear pivot 42. Each landing gear 4 and arm 2 has a landing gear spring fixing post 12, with both ends of the landing gear spring 41 fixed to the respective landing gear spring fixing post. The distance between the landing gear spring fixing post 12 on the arm 2 and the landing gear pivot mounting hole 27 is 9mm.

[0056] The landing gear 4 is slatted, with its upper and lower surfaces parallel to each other. Functionally, each landing gear has a connecting section at one end and a support section at the other. There is a 20° angle between the connecting section and the support section. Each connecting section has a landing gear pivot mounting hole 43 at its end. The landing gear pivot 42 passes through this mounting hole and is inserted into the arm landing gear pivot mounting hole 27, thereby hinged each landing gear to the lower surface of the arm. A landing gear spring retaining post is located on the side surface of the landing gear, 17mm away from the landing gear pivot mounting hole 43.

[0057] The landing gear spring 41 is a tension spring. In the UAV described in this invention, each landing gear is equipped with an identical landing gear spring 41, for a total of four springs. This landing gear spring is located on the side of the landing gear 4 and the arm 2, with one end fixed to a spring fixing post 12 located on the arm and the other end fixed to a spring fixing post 12 located on the landing gear. To meet the requirements of the UAV's flight conditions, the landing gear spring is made of 304 stainless steel wire with a circular cross-section, a wire diameter of 0.3mm, a wire length of 3mm, a length of 18mm, and 60 coils. Both ends have 2mm diameter lugs for fixing to the landing gear spring fixing post. The maximum load of the landing gear spring is 2.51N, the maximum deflection is 31.3mm, and the spring constant is 0.068N / mm. During flight, the distance between the two spring retaining posts used to fix the landing gear springs to the landing gear and the fuselage arm is 24mm. At this time, the landing gear springs will provide a tension of 0.408N, so that the landing gear can be fixed in the deployed position during flight. During deployment, the maximum distance between the two spring retaining posts is 26mm, and the deflection is 6mm, which is less than the maximum deflection of the landing gear springs, so the springs will not be damaged during deployment. When folded, the distance between the two spring retaining posts is 21mm. At this time, the landing gear springs will provide a tension of 0.204N, so that the landing gear can be fixed in the folded position when folded.

[0058] When the landing gear 4 is deployed, it extends outward from the fuselage under the tension of the landing gear spring 41, forming a 130° angle with the arm 2. This ensures that the outer surface 44 of the landing gear is in close contact with the landing gear deployment limiting block 26 on the arm, thus positioning the deployed landing gear 4. The landing gear deployment limiting block 26 is a protruding inclined surface at the end of the arm, serving to position the landing gear 4.

[0059] When landing gear 4 is folded, it retracts towards the fuselage side under the tension of landing gear spring 41, and the inner surface of the landing gear is pressed tightly against the bottom surface 28 of the arm on the arm 2, thereby positioning the landing gear in the folded position. At this time, the landing gear is parallel to the arm and fits against the side of the arm. The bottom surface 28 of the arm is a flat surface at the bottom of the arm, which serves to position the landing gear 4.

[0060] When the landing gear 4 is in the folded state, the distance between the two landing gear spring retaining posts is short, and the landing gear spring 41 is 21mm long, providing a moderate tension to keep the landing gear in the folded position. During landing gear deployment, the distance between the two landing gear spring retaining posts gradually increases, and the landing gear spring length also gradually increases, reaching its maximum value of 26mm at the landing gear position shown in Figure 17. After this position, the distance between the two spring retaining posts 12 gradually decreases. When the landing gear 4 reaches the landing gear position shown in Figure 18, the landing gear spring length is 24mm, providing tension to keep the landing gear in the deployed position.

Claims

1. A micro-sized folding unmanned aerial vehicle (UAV), comprising a fuselage (1), arms (2), a power unit (3), and landing gear (4); four arms are mounted on the fuselage (1), namely a left front arm, a right front arm, a left rear arm, and a right rear arm; the connecting ends of each arm are respectively hinged to arm joints (11) located on the fuselage; a power unit (3) is respectively mounted on the upper surface of the cantilever end of each arm; a landing gear (4) is mounted on the lower surface of the cantilever end of each arm by means of hinges; characterized in that, The hinge coordinates of each arm joint are as follows: left front arm (41mm, -28mm, -13mm), right front arm (41mm, 28mm, -13mm), left rear arm (88mm, -28mm, 9mm), and right rear arm (88mm, 28mm, 9mm). When deployed, each of the left front arm, right front arm, left rear arm, and right rear arm points to the fuselage at 45° to the left front, 45° to the right front, 45° to the left rear, and 45° to the right rear, respectively. A landing gear spring (41) is located between the landing gear (4) and the arm (2) on the same side surface, with one end of the landing gear spring fixed to the arm spring fixing post located on the arm, and the other end fixed to the landing gear spring fixing post located on the landing gear. On the spring fixing post; there is a spring fixing post for installing the arm spring (21) on the arm joint (11) and the arm (2), respectively. The arm spring is located below the arm joint and the arm (2), and one end of the arm spring is hooked on the arm joint spring fixing post on the lower surface of the arm joint, and the other end is hooked on the arm spring fixing post on the lower surface of the arm. Each arm (2) is slatted, and its upper and lower surfaces are parallel to each other. Each arm consists of two horizontal planes and an inclined plane connecting the two horizontal planes to meet the mutual avoidance between the front and rear arms and between the arm and the landing gear when folding. One end of each arm is a connecting end that is hinged to the arm joint (11), and the other end is a cantilever end. The upper surface of each cantilever end has a circular power unit mounting slot, and the power unit (3) is embedded in the power unit mounting slot; the lower surface of each arm with a power unit mounting slot is the bottom surface of the arm; there are protrusions at the edge of the lower surface of each power unit mounting slot, and each protrusion is adjacent to the landing gear shaft mounting hole of each arm; the protrusion is a landing gear deployment limiting block (26); there are also protrusions on the bottom surface of the arm, and each protrusion has a landing gear shaft mounting hole (27), and the center line of each landing gear shaft mounting hole is perpendicular to the center line of the power unit mounting slot; there are connecting holes at the end of each arm connection end, and the center line of each connecting hole is parallel to the power unit mounting slot. The centerline of the force device mounting groove; spring fixing posts (12) are respectively on the surface of each arm connecting to the landing gear (4); there are four arm joints (11), which are symmetrically distributed in two groups on both sides of the fuselage, forming the left front arm joint and the right front arm joint, as well as the left rear arm joint and the right rear arm joint, and the left front arm and the right front arm located at the front of the fuselage are located below the horizontal plane of the X-axis of the right-hand coordinate system, and the left rear arm and the right rear arm located at the rear of the fuselage are located above the horizontal plane of the X-axis of the right-hand coordinate system, so that the front arm and the rear arm located on the same side of the fuselage can be folded and stored on the side of the fuselage at the same time; the specific position coordinates of each arm joint on both sides of the fuselage satisfy the hinge coordinates of the corresponding arm.

2. The micro-sized folding drone as described in claim 1, characterized in that, The end face of the arm connector (11) has a U-shaped arm mounting groove (112); there are coaxial connector shaft mounting holes (111) on the upper and lower sides of the arm mounting groove, and the arm is hinged to the arm connector (11) through the arm shaft (22); the surface of the middle part of the bottom of the arm mounting groove is an arc surface, and the two ends of the arc surface are flat surfaces, and the flat surface near the body is the arm folding limiting surface (113), and the flat surface away from the body is the arm unfolding limiting surface (114); there is a wiring groove (115) on the bottom surface of the arm mounting groove, which is used to accommodate the motor wires after the arm is unfolded.

3. The micro-sized folding drone as described in claim 1, characterized in that, During flight, the distance between the arm spring retaining post on the fuselage arm and the landing gear spring retaining post on the landing gear is 24mm, and the landing gear spring provides a tension of 0.408N. During deployment, as the fuselage arm extends, the maximum distance between the spring retaining posts on the fuselage arm and the landing gear spring retaining posts is 26mm. During folding, as the fuselage arm retracts, the distance between the two spring retaining posts is 21mm, and the landing gear spring provides a tension of 0.204N, allowing the landing gear to be fixed in the folded position.

4. The micro-sized folding drone as described in claim 1, characterized in that, The distance between the spring fixing post on the arm and the joint shaft hole (111) is 21mm, and the distance between the spring fixing post (12) on the arm joint (11) and the joint shaft hole is 10mm.

5. The micro-sized folding drone as described in claim 1, characterized in that, The landing gear (4) is slatted, with its upper and lower surfaces parallel to each other. Functionally, each landing gear has a connecting section at one end and a supporting section at the other end. There is a 20° angle between the connecting section and the supporting section. At the end of each connecting section, there is a landing gear pivot mounting hole (43). The landing gear pivot (42) passes through the landing gear pivot mounting hole and is installed into the arm landing gear pivot mounting hole (27), thereby hinged each landing gear to the lower surface of the arm. There is a landing gear spring fixing post on the side surface of the landing gear.

6. The micro-sized folding drone as described in claim 1, characterized in that, When the landing gear (4) is opened to the outside, it forms an angle of 130° with the bottom surface of the arm.

7. The micro-sized folding drone as described in claim 1, characterized in that, When the UAV is in a folded state, the four arms (2) are folded and attached to the side surface of the fuselage at their respective positions; the landing gear (4) is folded and attached to the outside of the arms.

8. The micro-sized folding drone as described in claim 1, characterized in that, The landing gear spring (41) has a circular cross-section, a wire diameter of 0.2 mm, a diameter of 2 mm, a length of 18 mm, 60 coils, and fixed lugs at both ends; the maximum load of the landing gear spring is 2.51 N, the maximum deflection is 31.3 mm, and the spring constant is 0.068 N / mm; the boom spring (21) is a tension spring, with a wire diameter of 0.4 mm, a diameter of 4 mm, a length of 20 mm, 60 coils, a circular cross-section, and fixed lugs at both ends; the maximum load of the boom spring is 3.85 N, the maximum deflection is 23.9 mm, and the spring constant is 0.136 N / mm.

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