Mechanical device for passively reducing pulling moment of rope to rope machine cooperative unmanned aerial vehicle

Abstract

The utility model provides a mechanical device for passively reducing the pulling moment of a rope to a rope machine cooperative unmanned aerial vehicle. The mechanical device is composed of a rhombic plummer block, a mounting support, a set of pulleys, a device inner length fixing rope and a hook. Wherein the rhombic mounted bearing is mounted in the center of the bottom of the unmanned aerial vehicle body, and the unmanned aerial vehicle is connected with the whole device through the rhombic mounted bearing; the whole device rotates through the part; the mounting bracket is mounted on the rhombus mounted bearing, and the group of pulleys are mounted on the other side of the bracket; the pulley is mounted on the bracket through a screw; a fixed-length rope in the mechanical device penetrates through a gap between the pulley and the bracket and is connected end to end; the fixed-length rope in the device moves through the pulley; the hook is mounted on the fixed length rope in the device; as the fixed-length rope in the device moves through the pulley, the moving track of the hook on the plane where the fixed-length rope is located is an ellipse. The force arm of the external rope tension on the gravity center of the unmanned aerial vehicle is reduced, and therefore the disturbance torque of the external rope tension on the rope-machine cooperation unmanned aerial vehicle is further reduced.

Description

Technical Field

[0001] This utility model provides a mechanical device for a rope-assisted drone that can passively reduce rope tension. The device has a simple structure and is easy to install. Under rope tension in any direction, the device can reduce the force arm exerted by the rope on the drone, thereby further reducing rope tension. This device belongs to the field of mechanical design. Background Art

[0002] Unmanned aerial vehicles (UAVs) have developed rapidly in recent years. Multi-rotor UAVs, in particular, are capable of vertical takeoff and landing, feature simple and reliable structures, and have been widely used in a variety of fields, including aerial photography, agriculture, and transportation. Among these, tethered drones, including tethered and lifting drones, have garnered significant attention. Tethered drones are gaining traction as their use cases expand. Their defining feature is a tether that connects the drone to the ground, allowing it to remain airborne for extended periods, performing tasks such as emergency lighting and communications. Lifting drones, on the other hand, utilize a tether connecting the object being hoisted to the drone itself, allowing one or more drones to perform tasks such as transporting heavy objects.

[0003] However, because the rope tension and the center of gravity of the rope-assisted drone do not strictly coincide, such drones are highly susceptible to the disturbance torque generated by the rope tension. When the drone's rotors can provide sufficient torque, the drone's ability to resist disturbances can be improved by designing a more robust controller or employing disturbance estimation and compensation. However, when the rotor torque is insufficient to counteract the torque exerted on the drone by the rope tension, the drone's attitude angle may become uncontrolled, leading to a crash.

[0004] It's worth noting that, at present, there are relatively few mechanical device designs specifically for drone-mounted ropes. Some drones employ a universal joint design to ensure that the rope's tension is always directed toward the same point. However, this method still fails to reduce the interference torque caused by the rope's tension. The fundamental reason is that the force arm of the rope's tension remains unchanged. Furthermore, some drones have been designed with a bifurcated cable structure that allows the rope to rotate 360 degrees on a single plane. However, this design only reduces the impact and disturbance of the rope's tension on the tethered drone in one direction, which brings some limitations.

[0005] To address the above issues, the present invention utilizes the mathematical principle of ellipse to design a rope-mounting mechanical device. The device has three degrees of freedom and can effectively reduce the interference torque caused by rope tension in each direction of rope tension. Utility Model Content

[0006] The main goal of this utility model is to reduce the influence of the disturbance torque generated by the rope tension on the rope-machine cooperative UAV. A passive mechanical device (such as Figure 1 The device mainly consists of a diamond-shaped seat bearing, a mounting bracket, a set of pulleys, a fixed-length rope inside the device, and a hook.

[0007] The diamond-shaped seat bearing is installed in the center of the bottom of the drone fuselage, and the drone is connected to the entire device through this part. The entire device can be rotated through this part. The diamond-shaped seat bearing model is KFL08. Figure 5 shown.

[0008] The mounting bracket is mounted on a diamond-shaped seat bearing, and a set of pulleys is mounted on the other side of the bracket. The mounting bracket is made by 3D printing and adopts ABS material.

[0009] The pulley is mounted on the bracket by screws. The pulley is a 10mm pulley, such as Figure 6 shown.

[0010] The fixed-length rope in the device passes through the gap between the pulley and the bracket and is connected end to end. The fixed-length rope in the device can move through the pulley.

[0011] The hook is installed on the fixed length rope in the device. Since the fixed length rope in the device can move through the pulley, the moving track of the hook is an ellipse on the plane where the fixed length rope is located. The hook adopts 304 stainless steel with a ring spring buckle M4, such as Figure 7 shown.

[0012] In the aforementioned rope-assisted drone, the drone uses the aforementioned mechanical device to mount a rope, such as a tethering rope for tethering a drone, a hoisting rope for hoisting a drone, or other ropes used by rope-assisted drones. The rope should be directly connected to the hook on the drone, that is, the tension of the rope acts directly on the hook of the aforementioned device, and further acts on the drone (such as Figure 2 shown).

[0013] The mechanical device has a stable equilibrium state. According to the force analysis and the properties of the ellipse, the rope used to mount the drone on the mechanical device will reach the stable equilibrium state after the rope exerts a tension on the drone hook. When the mechanical device is in the stable equilibrium state, the direction vector of the external tension should be coplanar with the fixed length rope of the device (such as Figure 3a When the mechanical device is in the stable equilibrium state, the direction of the external pulling force should be perpendicular to the tangent of the elliptical motion trajectory of the hook in the longitudinal plane (as shown). Figure 3b shown).

[0014] To further illustrate the innovative role of this device, the following analysis is conducted in conjunction with Figure 3. Definition: In a rope-machine cooperative drone that does not use this utility model, the point of action of the rope tension is point M, which is relative to the center of gravity of the drone o b The distance is d0. In this utility model, to facilitate comparison and highlight the advantages of the utility model, the connection point between the mounting bracket and the diamond-shaped seat bearing is considered to be at point M. The fixed-length rope in the device passes through the gap between the pulley and the bracket, and the beginning and end are defined as points A and B respectively. The position of the hook in the device is defined as point o t , then click o t The sum of the distances to point A and point B is a constant. According to the definition of an ellipse, point o t The motion trajectory of is an ellipse on the longitudinal plane. Points A and B are the two foci of the motion trajectory ellipse. The major axis of the ellipse is point o. t Half the sum of the distances to point A and point B. The expression defining the elliptical locus in the longitudinal plane is:

[0015]

[0016] Where a is the length of the major axis of the elliptical trajectory, and b is the length of the minor axis of the elliptical trajectory. Assume that under any external tension, the equilibrium position of the hook is (x0, z0). Since the external tension in the longitudinal plane should be perpendicular to the tangent of the elliptical trajectory of the hook at the equilibrium point, the expression for the line on the longitudinal plane containing the external tension is:

[0017]

[0018] When x=0, we can get the external tension and the UAV o b z b The intersection of the axes is Its coordinate on the z-axis is the external tension and the UAV's o when using the mechanical device. b z b The distance from the intersection of the axes to the center of gravity of the drone. Since b < a, we can find that:

[0019]

[0020] Where, d is the rope tension after using the mechanical device and o b z b The distance between the intersection point and the center of gravity of the UAV indicates that the mechanical device plays a role in reducing the force arm of the external rope tension on the center of gravity of the UAV, thereby reducing the disturbance torque of the rope tension on the UAV by the rope machine.

[0021] The advantages and beneficial effects of this utility model lie in: utilizing the mathematical principles of ellipses to reduce the moment arm exerted by external rope tension on the drone's center of gravity, thereby further reducing the disturbance torque exerted by the external rope tension on the rope-assisted drone. First, the overall mechanical device achieves excellent results despite its simple structure and is easy to implement. Second, the device effectively improves the robustness and anti-disturbance capabilities of the rope-assisted drone. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of a mechanical device for passively reducing the pulling torque of a rope.

[0023] Figure 2 This is a schematic diagram of the rope machine and the drone mounted via a mechanical device, and the combination of the mechanical device and the drone.

[0024] Figure 3a and Figure 3b They are the top view and side view of the mechanical device when it is stable under any pulling direction.

[0025] Figure 4 It is a comparison chart of the position information of the UAV collected in the two sets of experiments and the rotor torque experimental results provided.

[0026] Figure 5 This is a schematic diagram of a diamond seat bearing.

[0027] Figure 6 It is a diagram of a pulley.

[0028] Figure 7 This is a hook diagram.

[0029] Figure 1-2 The labels in are as follows:

[0030] 1. Diamond-shaped seat bearing; 2. Mounting bracket; 3. Pulley; 4. Fixed-length rope; 5. Hook;

[0031] 6. Multi-rotor drone; 7. Rope machine: A drone that is mounted with a rope through a mechanical device.

[0032] Figure 3a and Figure 3b The symbols in are explained as follows:

[0033] o b is the center of gravity of the drone; x b is the direction of the drone's nose; z b It is the downward direction of the drone's body;

[0034] d0 is the distance between the installation position of the mechanical device and the center of gravity of the drone, and is also the distance between the rope tension and o when the mechanical device is not used. b z bThe distance between the intersection point and the center of gravity of the drone;

[0035] d is the rope tension after using the mechanical device and o b z b The distance between the intersection point and the center of gravity of the drone. DETAILED DESCRIPTION

[0036] This utility model designs a passive mechanical device that can reduce rope pulling torque. To more clearly illustrate the purpose, technical solution, and advantages of this utility model, the following comparative experiments will be conducted under the same conditions on drones with and without this mechanical device to demonstrate the advantages of this utility model.

[0037] Step 1: Assemble two multi-rotor drones with the same structure, one set has the mechanical device of the present invention installed directly below the drone, and the other set does not have the mechanical device of the present invention installed.

[0038] Step 2: Install two ropes on the two drones. Connect one end of each rope to the ground and the other end to the drone.

[0039] Step 3: Using the point where the rope connected to the ground as the origin, both drones hovered at a height of 2 meters, 4 meters and 2 meters horizontally from the origin, respectively. In both experiments, the rope was actively controlled to apply a 1.5N tension to the drones to maintain consistent variables.

[0040] Step 4: Collect the torque required by the drone to maintain attitude balance. From the torque balance, we can see that when the drone is able to hover stably, the disturbance torque of the external rope tension on the drone should be equal to the rotor torque actively provided by the drone.

[0041] According to the above steps, the experiment was carried out to collect the position information of the UAV in the two groups of experiments and the experimental results of the rotor torque provided as follows: Figure 4 The experimental results show that when the UAV is in a steady state, the UAV using the mechanical device of the present invention provides less rotor thrust than the UAV not using the mechanical device of the present invention.

Claims

1. A mechanical device for passively reducing the pulling torque of a rope on a rope machine in conjunction with an unmanned aerial vehicle, characterized by: It consists of a diamond-shaped seat bearing, a mounting bracket, a set of pulleys, a fixed-length rope inside the device and a hook; The diamond-shaped seat bearing is installed in the center of the bottom of the drone fuselage, and the drone is connected to the entire device through it; the entire device rotates through this part; The mounting bracket is mounted on a diamond-shaped seat bearing, and a set of pulleys is mounted on the other side of the bracket; The pulley is mounted on the bracket via screws; The fixed-length rope in the mechanical device passes through the gap between the pulley and the bracket and is connected end to end; the fixed-length rope in the device moves through the pulley; The hook is installed on the fixed-length rope in the device; since the fixed-length rope in the device moves through the pulley, the moving track of the hook is an ellipse on the plane where the fixed-length rope is located.

2. The mechanical device for passively reducing the pulling torque of a rope-to-rope machine in cooperation with a UAV according to claim 1, characterized in that: On a rope-machine coordinated drone, the drone uses a mechanical device to mount a rope, including a tethering rope used to tether the drone and a lifting rope used to lift the drone; the rope should be directly connected to the hook on the drone, that is, the rope tension directly acts on the hook of the mechanical device.

3. A mechanical device for passively reducing the pulling torque of a rope-to-rope machine in conjunction with a UAV according to claim 1 or 2, characterized in that: The mechanical device has a stable equilibrium state; the rope used to mount the drone through the mechanical device is obtained based on force analysis and the properties of the ellipse. After the tension acts on the hook of the drone, the mechanical device will reach a stable equilibrium state; when the mechanical device is in a stable equilibrium state, the direction vector of the external tension should be coplanar with the fixed-length rope of the mechanical device; when the mechanical device is in a stable equilibrium state, the direction of the external tension should be perpendicular to the tangent of the elliptical motion trajectory of the hook in the longitudinal plane.

4. The mechanical device for passively reducing the pulling torque of a rope-to-rope machine in conjunction with a UAV according to claim 1, characterized in that: The diamond-shaped seat bearing model is KFL08.

5. The mechanical device for passively reducing the pulling torque of a rope-to-rope machine in cooperation with a UAV according to claim 1, characterized in that: The mounting bracket is made by 3D printing and is made of ABS material.

6. The mechanical device for passively reducing the pulling torque of a rope-to-rope machine in conjunction with a UAV according to claim 1, characterized in that: The hook is made of 304 stainless steel with a ring spring buckle M4.

7. The mechanical device for passively reducing the pulling torque of a rope-to-rope machine in conjunction with a UAV according to claim 1, characterized in that: The connection point between the mounting bracket and the diamond-shaped seat bearing is at point M. The beginning and end of the fixed-length rope passing through the gap between the pulley and the bracket are defined as points A and B respectively. The position of the hook in the mechanical device is defined as point o. t , then click o t The sum of the distances to point A and point B is a constant; according to the definition of an ellipse, point o t The motion trajectory of is an ellipse on the longitudinal plane. Points A and B are the two foci of the motion trajectory ellipse. The major axis of the ellipse is point o. t Half the sum of the distances to point A and point B; the expression defining the elliptical locus in the longitudinal plane is: Where a is the length of the major axis of the ellipse, and b is the length of the minor axis of the ellipse.

8. The mechanical device for passively reducing the pulling torque of a rope-to-rope machine in conjunction with a UAV according to claim 7, characterized in that: Assume that under any external tension, the equilibrium position of the hook is (x0, z0). Since the external tension in the longitudinal plane should be perpendicular to the tangent of the elliptical trajectory of the hook's motion at the equilibrium point, the expression of the line on the longitudinal plane where the external tension is located is:

9. The mechanical device for passively reducing the pulling torque of a rope-to-rope machine in cooperation with a UAV according to claim 8, characterized in that: When x=0, the external tension and the drone o are obtained. b z b The intersection of the axes is The coordinate on the z-axis is the external tension and the coordinate of the drone when using the mechanical device. b z b The distance from the intersection of the axes to the center of gravity of the drone; since b < a, then: Where, d is the rope tension after using the mechanical device and o b z b The distance between the intersection point and the center of gravity of the UAV indicates that the mechanical device plays a role in reducing the lever arm of the external rope tension on the center of gravity of the UAV, thereby reducing the disturbance torque of the rope tension on the UAV by the rope-machine cooperative UAV.

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