Cable Suspended Aerial Manipulator System and Its Working Method

Abstract

The present invention relates to a cable-suspended aerial manipulator system and a working method, which includes a plurality of steel wires and a fixing frame. A plurality of winch devices for controlling the lengths of the respective steel wires are provided on the fixing frame. A plurality of outwardly extending rotor arms are connected to the periphery of the fixing frame. A servo motor A is installed on the rotor arms, and a rotor is connected to the rotating shaft of the servo motor A. A manipulator is installed at the bottom of the fixing frame. The cable-suspended aerial manipulator system of the present invention is reasonably designed and convenient to use. It can be suspended on a helicopter or a large-rotor unmanned aerial vehicle. It only needs to interact with the environment without considering its own gravity. By controlling the lengths of the steel wires, it can complete flipping, pitching, and staying at different heights, with good stability and high safety.

Description

Technical Field

[0001] The present invention relates to the field of unmanned aerial vehicle (UAV) aerial operation, and particularly to a cable-suspended aerial manipulator system and its working method. Background Art

[0002] Aerial operation is one of the most promising directions for UAVs in contact applications. Aerial operation is applied in many scenarios, mainly including: inspection of various structures, such as bridges, wires and pipelines, decoration of high-rise buildings, and operation in dangerous fields instead of humans, such as the demolition of damaged nuclear power plants. There are mainly two branches in the field of aerial operation: one is to use specific fixtures (such as grippers) to perform specific types of aerial interaction with the environment. Another important branch is to integrate a manipulator (or multiple manipulators) into the UAV and interact with the environment by remotely controlling the manipulator.

[0003] Generally speaking, when a manipulator is integrated into a UAV, the more degrees of freedom the manipulator has, the greater the actual application range. However, this will cause the weight to be too heavy, significantly reducing the endurance of the UAV and increasing the rotor radius of the UAV. This situation is difficult and unsafe for approaching the task target and performing tasks for a long time in a complex and narrow environment. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a cable-suspended aerial manipulator system and its working method with good stability and high safety, which can be suspended on a helicopter or a large-rotor UAV, and helps to complete operations in a narrow and complex environment through the manipulator while ensuring its own safety, thereby improving the interaction ability with the environment.

[0005] The present invention is implemented as follows: A cable-suspended aerial manipulator system includes a plurality of steel wires and a fixing frame. The fixing frame is provided with a plurality of winch devices for controlling the lengths of the respective steel wires. A plurality of outstretched rotor arms are connected to the periphery of the fixing frame. A servo motor A is installed on the rotor arm, and a rotor is connected to the rotating shaft of the servo motor A. A manipulator is installed at the bottom of the fixing frame.

[0006] Further, three rotor arms distributed in a triangle are movable rotor arms that can swing up and down. The movable rotor arms are hinged to the fixing frame, and a limiting mechanism is provided at the position of each movable rotor arm close to the hinged end.

[0007] Further, the limiting mechanism includes a limiting card that swings under the control of a servo motor B. The servo motor B is fixedly connected to the movable rotor arm. A limiting plate is provided beside the movable rotor arm, and two upper and lower limiting slot buckles that are respectively clamped and matched with the limiting card when the movable rotor arm swings up and down are provided on the limiting plate.

[0008] Further, the lengths of the three movable rotor arms are longer than those of the other rotor arms. The servo motor A on the movable rotor arm is located at the middle position in the length direction of the rotor arm, and the servo motor A on the other rotor arms is located at the outer end in the length direction of the rotor arm.

[0009] Further, the winch device includes a wire rope guide frame and a winch for winding the lower end of the wire rope and driven by a DC motor to rotate. The wire rope guide frame is provided with a guide hole for the wire rope to pass through, and a fiber optic sensor for sensing the wire rope is provided on the wire rope guide frame.

[0010] Further, the fixing frame includes a top plate and a bottom plate connected together by rib plates. The robotic arm is installed on the lower side of the bottom plate and deviates from the center of the bottom plate by a certain distance; the limiting mechanism and the winch device are both located between the top plate and the bottom plate, and the upper ends of all wire ropes pass through the top plate downward and are connected together.

[0011] Another technical solution of the present invention: A working method of the cable-suspended aerial robotic arm system as described above. When working, the aerial robotic arm system is suspended on a helicopter or a large-rotor unmanned aerial vehicle as the load-bearing part and used. The load-bearing part moves the aerial robotic arm system to the target position and makes it hover in the air; the aerial robotic arm system can control the length of the wire rope through the winch device to make the aerial robotic arm system complete flipping, pitching and staying at different heights. The robotic arm starts to perform tasks and controls the rotation of the rotors at different positions to offset the reaction forces or torques in different directions generated when the robotic arm is working; when descending after completing the task, control the movable rotor arm to swing down and use it as a landing gear.

[0012] Compared with the prior art, the present invention has the following beneficial effects: The cable-suspended aerial robotic arm system of the present invention adopts a suspended design and can be suspended on a helicopter or a large-rotor unmanned aerial vehicle for use. It only needs to interact with the environment by itself without considering its own gravity, with good stability and high safety; by controlling the length of the wire rope, flipping, pitching and staying at different heights can be completed, which helps to complete operations in a narrow and complex environment through the robotic arm while ensuring its own safety, thereby improving the interaction ability with the environment.

[0013] In order to make the purpose, technical solution and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below through specific embodiments and related drawings. Description of the Drawings

[0014] Figure 1 is a schematic diagram of the use state structure of the embodiment of the present invention;

[0015] Figure 2 is a schematic structural diagram of the cable-suspended aerial robotic arm system in the embodiment of the present invention;

[0016] Figure 3 It is a schematic diagram of the operating state of the robotic arm in the embodiment of the present invention;

[0017] Figure 4 It is a schematic diagram of the structure of the robotic arm in the parking state in the embodiment of the present invention;

[0018] Figure 5 It is a simplified model of the propulsion unit in the embodiment of the present invention (1, 3, 5, 7 are forward propellers, 2, 4, 6, 8 are reverse propellers);

[0019] Figure 6 It is a structural block diagram of the cable-suspended aerial robotic arm system in the embodiment of the present invention;

[0020] Figure 7 It is a schematic diagram of the cable-suspended aerial robotic arm system in the embodiment of the present invention;

[0021] Figure 8 It is a schematic diagram of the torque of the cable-suspended aerial robotic arm system in the embodiment of the present invention;

[0022] Figure 9 It is a cascade control scheme diagram of the cable-suspended aerial robotic arm system in the embodiment of the present invention;

[0023] Description of the reference numerals in the figure: 1, steel wire rope; 2, top plate; 3, servo motor A; 4, rotor arm; 41, movable rotor arm; 5, rotor; 6, bottom plate; 7, robotic arm; 8, rib plate; 9, connection point; 10, center of mass; 11, winch; 12, DC motor; 13, fiber optic sensor; 14, steel wire rope guide frame; 15, limit slot buckle; 16, limit card; 17, servo motor B. Detailed implementation manners

[0024] It should be noted that the following detailed description is exemplary and is intended to provide further illustration of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present application belongs.

[0025] It should be noted that the terms used herein are only for describing the specific implementation manners and are not intended to limit the exemplary implementation manners according to the present application. As used herein, unless the context clearly indicates otherwise, the singular forms are also intended to include the plural forms. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of the features, steps, operations, devices, components, and / or combinations thereof.

[0026] As Figures 1 - 9As shown in the figure, a cable-suspended aerial manipulator system includes a number of steel wires 1 and a fixed frame. The fixed frame is provided with a number of winch devices for controlling the lengths of the respective steel wires 1. A number of outwardly extending rotor arms 4 are connected to the periphery of the fixed frame. A servo motor A3 is installed on the rotor arm 4, and a rotor 5 is connected to the rotating shaft of the servo motor A3. A manipulator 7 is installed at the bottom of the fixed frame. The aerial manipulator system performs aerial operations through the manipulator it carries, enabling the manipulator to execute operations in narrow and complex environments while maintaining a safe distance from obstacles. The entire aerial operation platform consists of two parts: a load-bearing part and an operation part. The cable-suspended aerial manipulator system of the present invention is the operation part. The load-bearing part provides lift to counteract gravity for the entire aerial manipulator system, enabling the aerial manipulator system to hover in the air. The aerial manipulator system is suspended on the load-bearing part by steel wires with controllable lengths and interacts with the environment. The load-bearing part can be a helicopter or a large-rotor unmanned aerial vehicle, which can provide stable lift and increase the endurance time. During operation, the load-bearing part is mainly used to move the operation part to the target position, and then its main function is to hover in the air.

[0027] The manipulator 7 is a seven-axis manipulator. The manipulator is a prior art, and its structure and principle will not be specifically described herein. This manipulator has two main states: operation and parking. During transportation and landing, the manipulator is in the parking configuration. When starting any operation task, such as picking up and placing and driving into holes, the manipulator should be in the operation configuration. The end of the manipulator can be equipped with a suitable fixture to adapt to different working conditions.

[0028] In this embodiment, three rotor arms 4 distributed in a triangle can swing up and down are movable rotor arms 41. The movable rotor arms 41 are hinged to the fixed frame, and a limit mechanism is provided at the position of each movable rotor arm 41 near the hinge end. The three movable rotor arms can rotate 60° to be used as landing gears. When the movable rotor arms swing upward, they are in a horizontal state and are used as rotor arms. When they swing downward, the included angle with the horizontal direction is 60°, and they are used as landing gears.

[0029] In this embodiment, the limiting mechanism includes a limiting card 16 that swings under the control of a servo motor B17. The servo motor B17 is fixedly connected to the movable rotor arm 41. There is a limiting plate beside the movable rotor arm 41. The limiting plate is provided with two upper and lower limiting slot buckles 15 that are respectively engaged with the limiting card when the movable rotor arm swings up and down. The limiting slot buckle 15 is made of plastic and is used to lock the movable rotor arm in these two positions. When it is necessary to switch from the rotor arm to the landing gear, it can be completed by relying on the self-gravity of the rotor arm. The conversion from the landing gear to the rotor arm is completed by the lift generated by the rotation of the rotor to drive the rotor arm to rise. During this process, some torques may be generated due to the thrust, and the thrust of the other five rotors can be controlled to compensate for these torques. Due to the switchable landing gear, there is a larger operating space for the operating part, and there is no obstruction caused by traditional landing gears (such as slides).

[0030] In this embodiment, the lengths of the three movable rotor arms are longer than those of the other rotor arms. The positions of the three movable rotor arms are distributed in an isosceles triangle. The servo motor A on the movable rotor arm is located at the middle position in the length direction of the rotor arm, and the servo motor A on the other rotor arms is located at the outer end in the length direction of the rotor arm. All the servo motor As are located on the same circumference. There are 8 rotor arms in total, and 3 of them can swing up and down. The length of the movable rotor arm is about twice that of the other rotor arms. The eight rotors constitute propulsion. Due to the existence of the load-bearing part, the propulsion unit does not need to compensate for the gravity of the operating part. The existence of the propulsion unit is to offset the reaction forces or torques in different directions generated by the robotic arm during operation. Since there is no need to compensate for gravity, the rotors of the propulsion unit are smaller.

[0031] Each propulsion unit can control the rotor to rotate around an angle α of 0-360 through the servo motor A on the rotor arm. By installing the propulsion units non-collinearly, 6 degrees of freedom of omnidirectional forces can be generated, which can compensate for the forces or torques of the robotic arm in any direction.

[0032] In this embodiment, the winch device includes a wire rope guide frame 14 and a winch 11 for winding the lower end of the wire rope and driven by a DC motor 12 to rotate. A guide hole for the wire rope 1 to pass through is provided on the wire rope guide frame 14, and an optical fiber sensor 13 for sensing the wire rope 1 is provided on the wire rope guide frame 14; the wire rope passes through the wire rope guide frame and is wound on the winch, and an optical fiber sensor is used for calibration. In the calibration configuration, the wire rope is between the light sources of the two optical fiber sensors. By sensing the interruption and reflection of the light speed, the calibration system can detect the wire rope close to the reflection optical fiber unit (light source) to ensure that the wire rope is within the track of the winch, thereby ensuring that the wire rope can be wound on the winch better. There are three wire ropes, which are respectively in an equilateral triangle. Therefore, there are also three winch systems. By controlling the length of the wire rope through the winch, the operating part can be flipped, pitched, and stay at different heights, and the center of mass of the operating part is directly below the suspension point to ensure the stability of the operating part.

[0033] In this embodiment, the fixed frame includes a top plate 2 and a bottom plate 6 connected together by rib plates. Both the top plate and the bottom plate are octagons. The robotic arm is installed on the lower side of the bottom plate and deviates from the center of the bottom plate by a certain distance, so that the center of mass of the robotic arm is on the central axis of the cable-suspended aerial robotic arm system, improving stability. The limiting mechanism and the winch device are both located between the top plate and the bottom plate. The upper ends of all wire ropes pass through the top plate downward and are connected together, that is, connected to the connection point 9.

[0034] The ground workstation controls the load-bearing part and the operating part by radio. Among them, a vision computer, a robotic arm control computer, and a flight control computer are installed on the fixed frame. The vision computer controls the cameras installed on the load-bearing part and the operating part to feed back real-time images to the operator during remote operation. The robotic arm control computer is used to control the robotic arm to adjust different forms to suit aerial operations. The flight control computer is used to control the DC motor, servo motor A, and servo motor B. By controlling the different rotational speeds and the thrust directions generated by the propulsion unit rotors, the forces or torques required by the robotic arm during operation are compensated. The main body of the operating part (i.e., the fixed frame) is mainly composed of two top plates and a bottom plate. Almost all components are installed between the two top plates and the bottom plate. Therefore, the winch device and the robotic arm are installed on the bottom plate, while other electronic components (including the battery) are either installed on the top plate or on the rib plates between the top plate and the bottom plate. Removing the top plate allows for quick and easy viewing of all electronic components.

[0035] A working method of the cable-suspended aerial manipulator system as described above. During operation, the aerial manipulator system is suspended by a steel wire rope on a helicopter or a large-rotor unmanned aerial vehicle serving as the load-bearing part. At this time, the movable rotor arm swings up to the horizontal position, and the load-bearing part moves the aerial manipulator system to the target position and makes it hover in the air. The ground workstation controls the load-bearing part and the aerial manipulator system via radio. The aerial manipulator system can control the length of the steel wire rope through a winch device to enable the aerial manipulator system to complete flipping, pitching, and staying at different heights. The manipulator starts to perform tasks and counteracts the reaction forces or torques in different directions generated by the manipulator during operation by controlling the rotation of the rotors at different positions. When descending after completing the task, the movable rotor arm is controlled to swing down 60° to be used as a landing gear.

[0036] Dynamics model of the propulsion unit:

[0037] As Figure 5 , we define a fixed coordinate system as , the origin of the coordinate system is , and the points on the coordinate axes are { }. The origin of the body coordinate system is at the mass center of the propulsion unit , and the points on the coordinate axes are , is not only the center of the airframe but also the geometric center of the eight rotors. At The position in is represented by , At The azimuth angle in is represented by the rotation matrix , Relative to The angular velocity of is represented by , then The kinematic equation of is (1)

[0038] Using , And To represent three orthogonal basis vectors, , And Are orthogonal rotation matrices in space. Define the coordinate systems of the eight rotors as ,…, , the origin of the rotor coordinate system Is the rotation center of the rotor, and the coordinates of each coordinate of the coordinate system are { , then Is equivalent to The rotation matrix of is

[0039] (2)

[0040] Among them, α is the tilt angle of the rotor, which can be adjusted by a servo motor. It means that the tilt modes of adjacent rotors are opposite.

[0041] In the coordinate system, the vector pointing to can be expressed as

[0042] (3)

[0043] Among them, l is and the distance between.

[0044] The i-th rotor rotates around as the center with an angular velocity of where is the controllable propeller rotation speed. When rotating, the propeller exerts thrust and drag torque in the along the direction. The expression in the coordinate system is (4)

[0045] (5)

[0046] Among them are the fixed parameter characteristics of different rotor types. is the magnitude of the force generated by the rotor, which can be related to the rotation rate, and the expression is (6)

[0047] is a fixed parameter related to the rotor. The existence of in formulas (2) and (5) indicates counter-rotation between adjacent rotors, avoiding the entire body from shifting due to the torque generated when the motor drives the rotor to rotate.

[0048] By adding up the thrusts generated by all rotors, the total thrust at the center of mass can be calculated. The expression in the fixed coordinate system is (8)

[0049] Among them is the correlation matrix regarding the tilt angle. When = 0, all rotors are coplanar like an octocopter. At this time .

[0050] By adding up the torques generated by all rotors, we obtain the entire thrust unit relative to The total moment of a point, in the expression in the coordinate system is (9)

[0051] Using the Newton-Euler method, it can be simply written as (10)

[0052] where J is the 3×3 inertia matrix with respect to , m is the total mass, and g is the gravitational acceleration.

[0053] Substituting equations 8 and 9 into 10, the motion equation of the propulsion unit can be obtained as

[0054] (11)

[0055] In the formula (12)

[0056] Cable-suspended aerial manipulator system model:

[0057] In the modeling, the load-bearing part hovering in the air is ignored, the wire rope is regarded as a massless rigid link, and the operating part is approximated as a uniform disk. Therefore, the mathematical expression of the cable-suspended aerial manipulator system model is: (13)

[0058] where M is the inertia matrix, C is the Coriolis force, and g is the gravitational vector. The configuration matrix q is expressed as:

[0059] (14)

[0060] As Figure 7 , 8 shown, represents the total yaw angle, and respectively represent the roll and pitch angles of the first and second joints. is the joint angle of the manipulator. The control input can be expressed as: (15)

[0061] where, and is the actual torque input of the manipulator joint, and are the torques required for the change of the manipulator joint.

[0062] The total moment of the thrust unit can be obtained from the joint change torque

[0063] (16)

[0064] Among them, the Jacobian matrix J maps the body twist angle v to the roll, pitch, and yaw (RPY) rates.

[0065] (17)

[0066] Finally, the torques required for the eight propulsion units can be obtained by finding the inverse of the distribution matrix.

[0067] Control method:

[0068] Adopt Figure 8 the cascade control scheme in [] to control the cable-suspended aerial manipulator system, where the manipulator has a high sensing and control frequency, and has a high degree of control over the yaw axis because this degree of freedom cannot be controlled only by controlling the length of the wire rope. Therefore, the manipulator and yaw control can be regarded as the inner loop of the control cascade, and a proportional coefficient for gravity compensation is added.

[0069] For any of the technical solutions disclosed by the present invention as described above, unless otherwise stated, if it discloses a numerical range, then the disclosed numerical range is a preferred numerical range. Any person skilled in the art should understand that the preferred numerical range is only the numerical values with obvious technical effects or representativeness among many feasible numerical values. Since there are too many numerical values to enumerate, the present invention only discloses some numerical values to illustrate the technical solutions of the present invention, and the above-listed numerical values should not constitute a limitation on the protection scope of the present invention.

[0070] If the present invention discloses or involves components or structural parts that are fixedly connected to each other, then, unless otherwise stated, the fixed connection can be understood as: a detachable fixed connection (for example, using bolts or screws), or it can also be understood as: a non-detachable fixed connection (for example, riveting, welding). Of course, the mutually fixed connection can also be replaced by an integral structure (for example, manufactured by integral casting) (except when it is obviously impossible to adopt the integral forming process).

[0071] In addition, for the terms used to represent the positional relationship or shape in any of the technical solutions disclosed by the present invention as described above, unless otherwise stated, their meanings include states or shapes that are approximate, similar, or close to them.

[0072] Any component provided by the present invention can either be assembled from multiple separate components or be a single component manufactured by an integral forming process.

[0073] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention in any other form. Any person skilled in the art may use the technical content disclosed above to make changes or modifications into equivalent embodiments with equivalent changes. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the technical solution content of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A cable-suspended aerial manipulator system, characterized in that: It includes a number of steel wire ropes and a fixing frame. A number of winch devices for controlling the lengths of the respective steel wire ropes are provided on the fixing frame. A number of outstretched rotor arms are connected to the periphery of the fixing frame. A servo motor A is installed on the rotor arm. A rotor is connected to the rotating shaft of the servo motor A. A robotic arm is installed at the bottom of the fixing frame. Among them, three rotor arms distributed in a triangle are movable rotor arms that can swing up and down. The movable rotor arms are hinged to the fixing frame. A limit mechanism is provided at a position near the hinge end of each movable rotor arm. The limit mechanism includes a limit card that swings under the control of a servo motor B. The servo motor B is fixedly connected to the movable rotor arm. A limit plate is provided beside the movable rotor arm. Two upper and lower limit slot buckles that are respectively clamped and matched with the limit card when the movable rotor arm swings up and down are provided on the limit plate. The lengths of the three movable rotor arms are longer than those of the other rotor arms. The servo motor A on the movable rotor arm is located at the middle position in the length direction of the rotor arm. The servo motor A on the other rotor arms is located at the outer end in the length direction of the rotor arm.

2. The cable-suspended aerial manipulator system according to claim 1, characterized in that: The winch device includes a steel wire rope guide frame and a winch for winding the lower end of the steel wire rope and driven by a DC motor to rotate. A guide hole for the steel wire rope to pass through is opened on the steel wire rope guide frame. An optical fiber sensor for sensing the steel wire rope is provided on the steel wire rope guide frame.

3. The cable-suspended aerial manipulator system according to claim 1, characterized in that: The fixing frame includes a top plate and a bottom plate connected together by rib plates. The robotic arm is installed on the lower side of the bottom plate and deviates from the center of the bottom plate by a certain distance. The limit mechanism and the winch device are both located between the top plate and the bottom plate. The upper ends of all the steel wire ropes pass downward through the top plate and are connected together.

4. A working method of the cable-suspended aerial manipulator system as described in claim 1, characterized in that: During operation, the aerial robotic arm system is suspended on a helicopter or a large rotor unmanned aerial vehicle as the load-bearing part by the steel wire ropes, and the load-bearing part moves the aerial robotic arm system to the target position and makes it hover in the air. The aerial robotic arm system can complete flipping, pitching and staying at different heights by controlling the lengths of the steel wire ropes through the winch device. The robotic arm starts to operate the task and offsets the reaction forces or torques in different directions generated by the robotic arm during operation by controlling the rotation of the rotors at different positions. When descending after completing the task, control the movable rotor arms to swing down to be used as landing gears.

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