Multi-degree-of-freedom mechanical arm for multi-rotor unmanned aerial vehicle

Abstract

The invention relates to the field of mechanical arms, and discloses a multi-degree-of-freedom mechanical arm for a multi-rotor unmanned aerial vehicle, the multi-degree-of-freedom mechanical arm comprises a planetary reducer, a parallel truss mechanism, an ankle joint mechanism and a tail end executing mechanism, the planetary reducer is composed of a straight gear pair, a planet gear and a sun gear, and power of a direct current motor is introduced through a straight gear; the parallel truss mechanism achieves position mirror image synchronization of the upper-section mechanical arm and the lower-section mechanical arm through a gear pair, and a planetary reducer provides power for the parallel truss mechanism. The ankle joint mechanism is composed of a universal joint and a screw telescopic mechanism. The tail end executing mechanism comprises an eagle claw, a transmission mechanism composed of a gear pair and a thread pair is arranged in the middle of the eagle claw, and mechanical fingers composed of multiple stages of gear pairs are arranged on the outer side of the eagle claw in a circumferential mode. Through cooperative work of the planetary reducer, the parallel-connection parallel truss mechanism, the ankle joint mechanism and the tail end executing mechanism, the mechanical arm can achieve complex movement and operation tasks, precision is high, and flexibility is good.

Description

Technical Field

[0001] The present invention relates to the field of mechanical arms, and in particular to a multi-degree-of-freedom mechanical arm for a multi-rotor unmanned aerial vehicle. Background Art

[0002] Multi-rotor drones, which have air superiority, can ignore complex terrain and have high moving speeds and better observation angles. Currently, multi-rotor drones are mostly used to carry high-definition cameras or detection equipment for aerial photography, search and rescue after earthquakes, fires, and other disasters, safety inspections of buildings such as bridges and power lines, and growth monitoring and evaluation of farmland crops. However, the application of multi-rotor drones should not stop there. In addition to completing passive tasks such as inspection, surveillance, monitoring, and remote sensing, they should also be able to perform active tasks such as grasping or manipulation.

[0003] The key is to give the UAV a manipulator, that is, a robotic arm, that is, a flexible and reliable manipulator like a human arm. Since the load of the UAV is relatively limited, the mass of the manipulator is severely limited. At the same time, the movement of the manipulator is also an external disturbance for under-actuated UAVs, and the flight control of UAVs with manipulators is also particularly important. Therefore, how to design a flexible, lightweight, and reliable robotic arm for UAVs is an urgent problem to be solved. At present, there are only a few robotic arms suitable for multi-rotor UAVs, and most of the available robotic arms are heavy and have limited degrees of freedom. This scheme combines mechanical principles and bionic design ideas to propose a multi-degree-of-freedom robotic arm system for multi-rotor UAVs. Summary of the invention

[0004] The present invention is intended to provide a multi-degree-of-freedom robotic arm for a multi-rotor UAV. Through the coordinated operation of a planetary reducer, a parallel truss mechanism, an ankle joint mechanism and an end actuator, the robotic arm can achieve complex motion and operation tasks with high precision and good flexibility.

[0005] In order to achieve the above object, the present invention adopts the following technical scheme: A multi-degree-of-freedom mechanical arm for a multi-rotor unmanned aerial vehicle, comprising a planetary reducer, a parallel truss mechanism, an ankle joint mechanism and an end actuator; The planetary reducer comprises a spur gear pair and a planetary gear and a sun gear set connected in sequence, the DC motor output shaft is fixedly connected to the spur gear pair, the planetary gear and the sun gear are connected end to end, and have the same reduction ratio; The parallel parallel truss mechanism comprises an upper mechanical arm and a lower mechanical arm, the upper mechanical arm and the lower mechanical arm are hinged to the middle connecting plate and connected through a gear pair; the power output end of the planetary reducer is fixedly connected to the upper mechanical arm through a threaded pair; The ankle joint mechanism includes a universal joint and a screw telescopic mechanism, the universal joint is connected to the lower section mechanical arm and the eagle claw respectively; the screw telescopic mechanism is also a component of the lower section mechanical arm and is connected to the eagle claw spherical hinge; The end actuator includes an eagle claw, which includes a transmission mechanism driven by an eagle claw driving motor. The transmission mechanism includes a gear pair, a thread pair and a rack and pinion pair. The eagle finger composed of a multi-stage gear pair is circumferentially arranged on the outside of the eagle claw, and the transmission mechanism drives the eagle finger to move synchronously through the rack and pinion pair.

[0006] The principle and advantages of this scheme are as follows: in actual application, the output shaft of the DC motor is fixedly connected to the spur gear pair, and the power of the DC motor is introduced through the spur gear pair. The planetary gear and the sun gear are connected end to end, and the reduction ratio is the same, forming a compact and efficient reduction structure. Through the planetary reducer, the high-speed rotation of the motor is significantly reduced and converted into a large torque output suitable for the movement of the robot arm. The upper robot arm is fixedly connected to the power output end of the planetary reducer through a threaded pair, and the power is transmitted through the gear pair, so that the upper and lower robot arms can move flexibly in multiple directions, providing a larger working space and posture adjustment ability. The universal joint allows the lower robot arm to rotate freely in multiple directions, providing flexible posture adjustment ability, and the screw telescopic mechanism adjusts the position of the eagle claw through the telescopic action, further enhancing the flexibility and adaptability of the robot arm. The transmission mechanism drives the eagle finger to move synchronously through the gear rack pair to achieve precise grasping and releasing operations. The DC motor provides power, and after multi-stage gear pair reduction, it drives the eagle finger to perform delicate operations. This scheme realizes high-precision, flexible and efficient power transmission, which not only improves the overall performance of the robot arm, but also enhances its adaptability and scalability, and has broad application prospects.

[0007] Preferably, as an improvement, the overall appearance of the planetary reducer is cylindrical, the DC motor is installed on the outside of the planetary reducer, and the axis of the DC motor is parallel to the axis of the planetary reducer.

[0008] Technical effect: The cylindrical design and the layout of the DC motor and the planetary reducer axis parallel make the entire system more compact, reduce the volume and weight, and improve the portability and applicability of the system.

[0009] Preferably, as an improvement, the spur gear pair includes a large and a small spur gear meshing with each other, wherein the smaller gear is fixedly connected to the output shaft of the DC motor via a U-shaped groove, and the larger gear is fixedly connected to the input end of a set of planetary gears and a sun gear.

[0010] Technical effect: The planetary gear train has a compact structure and can achieve a higher reduction ratio while maintaining a high transmission efficiency.

[0011] Preferably, as an improvement, the upper section of the robotic arm includes an upper transmission arm and a driven arm, the lower section of the robotic arm includes a lower transmission arm and a screw telescopic mechanism fixing seat, the upper transmission arm, the driven arm, the lower transmission arm and the screw telescopic mechanism fixing seat are all provided with a spur gear structure at one end for connecting the upper section of the robotic arm and the lower section of the robotic arm, the gears of the upper transmission arm and the lower transmission arm form a set of spur gear pairs, and the gears of the driven arm and the screw telescopic mechanism fixing seat form a set of spur gear pairs.

[0012] Technical effect: The mirror synchronization of the position movement of the upper and lower robotic arms of the parallel parallel truss mechanism is achieved through two pairs of gear pairs, thereby converting the rotation of the DC motor output shaft into the lifting and lowering movement of the multi-degree-of-freedom robotic arm.

[0013] Preferably, as an improvement, the gear axis of the spur gear pair in the parallel truss mechanism coincides with the hinge axis.

[0014] Technical effect: It can provide high-precision power transmission and stable motion control while ensuring a compact structure, meeting the requirements of drones for lightweight and high performance.

[0015] Preferably, as an improvement, the screw rod telescopic mechanism fixing seat includes a spherical hinge groove, and a spherical hinge is formed by the spherical hinge groove and the upper end ball head of the outer sleeve motor fixing seat.

[0016] Technical effect: easy to adjust angles and achieve flexible movement in multiple directions.

[0017] Preferably, as an improvement, the screw telescopic mechanism includes an outer sleeve motor fixing seat, an outer sleeve, a spiral drum, a small screw, a triangular prism push rod, an end ball head and a screw telescopic mechanism driving motor with colinear axes. The screw telescopic mechanism driving motor is installed in the outer sleeve motor fixing seat, and the output end of the screw telescopic mechanism driving motor is fixedly connected to the spiral drum through a D-shaped hole. The small screw moves axially in the spiral drum through a threaded pair. The small screw, the triangular prism push rod and the end ball head are rigidly connected, and the end of the outer sleeve is provided with a triangular opening that matches the triangular prism push rod.

[0018] Technical effect: easy to achieve precise telescopic control.

[0019] Preferably, as an improvement, the transmission mechanism adopts an eagle claw drive motor as the power input source of the gear pair, and the rotation of the output shaft of the eagle claw drive motor is converted into vertical movement of the palm lifting member and the rack through the gear pair and the thread pair.

[0020] Technical effect: The above combination achieves precise speed and torque conversion, ensuring ultimate motion accuracy.

[0021] Preferably, as an improvement, the eagle claw drive motor is connected to the transmission spur gear through a U-shaped groove, the transmission spur gear is meshed with the spur gear at the bottom of the screw gear, and is installed on the palm at the same time, and the periphery of the palm lifting piece is provided with a rack fixed by a slot.

[0022] Technical effect: It is convenient for the transmission mechanism to drive the synchronous movement of the eagle fingers through the gear rack pair of the rack, so as to realize the overall opening and closing action of the eagle claws.

[0023] Preferably, as an improvement, the eagle finger includes an eagle finger bridge, the internal gear is mounted on the eagle finger through an axial hole, the eagle finger is mounted on the eagle finger bridge through an axial hole, and the eagle finger bridge includes a gear structure.

[0024] Technical effect: The Eagle Finger is used to achieve precise grasping and object manipulation. Through the shaft-hole matching method, the internal gear directly transmits power to the Eagle Finger, reducing the energy loss and error accumulation in the intermediate links, ensuring the accuracy and stability of power transmission, and improving the overall performance of the system. The shaft-hole matching can effectively reduce the gap and vibration between components, thereby improving the system's motion accuracy and response speed, evenly distributing stress, avoiding fatigue damage caused by local stress concentration, and extending the service life of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Shown is a schematic diagram of the overall structure of an embodiment of the present invention; Figure 2 The figure shows the exploded structure diagram of the planetary reducer in the embodiment; Figure 3 Shown is a schematic structural diagram of a parallel truss mechanism in an embodiment; Figure 4 The figure shows a schematic diagram of the structure of a pair of screw telescopic mechanisms in the embodiment; Figure 5 Shown is a schematic structural diagram of the ankle joint mechanism in the embodiment; Figure 6 The figure shows an exploded structural schematic diagram of the screw telescopic mechanism in the embodiment; Figure 7 Shown is a schematic diagram of the structure of the eagle claw in the embodiment; Figure 8 The figure shows a schematic diagram of the structure of the middle transmission mechanism of the eagle claw in the embodiment; Fig. 9 The figure shows a schematic diagram of the structure of the eagle finger of the eagle claw in the embodiment; Fig.10 The figure shows a simplified model schematic diagram of the kinematic analysis of the multi-degree-of-freedom bionic eagle leg manipulator in the embodiment; Fig.11 The figure shows a schematic diagram of the mathematical model of the ankle joint mechanism motion of the multi-degree-of-freedom bionic eagle leg manipulator in the embodiment; Fig.12 The figure shows a schematic diagram of an equivalent circuit of a DC motor of a multi-degree-of-freedom bionic eagle leg robotic arm in an embodiment; Fig.13 The figure shows a mathematical model diagram of a DC motor of a multi-degree-of-freedom bionic eagle leg mechanical arm in an embodiment; Fig.14 Shown is a schematic diagram of the angular velocity and angular displacement PID controller of the multi-degree-of-freedom robotic arm in the embodiment. DETAILED DESCRIPTION

[0026] The following is further described in detail through specific implementation methods: The figure marks in the drawings of the specification include: planetary reducer 1, electronic component box 2, parallel parallel truss mechanism 3, ankle joint mechanism 4, end actuator 5, upper transmission arm 6, driven arm 7, lower transmission arm 8, intermediate connecting plate 9, screw telescopic mechanism fixing seat 10, outer sleeve motor fixing seat 11, outer sleeve 12, spiral drum 13, small screw 14, triangular column push rod 15, end ball head 16, universal joint 17, eagle claw 18, screw telescopic mechanism drive motor 19, palm connecting part 20, palm 21, eagle claw drive motor 22, screw gear 23, transmission spur gear 24, palm lifting part 25, rack 26, finger 27, fourth section internal gear 28, third section internal gear 29, second section internal gear 30, first section internal gear 31, second section eagle finger 32, first section eagle finger 33, eagle finger bridge 34.

[0027] The embodiment is basically as shown in the attached Figure 1 As shown, a multi-degree-of-freedom mechanical arm for a multi-rotor UAV includes: a planetary reducer 1, a parallel truss mechanism 3, an ankle joint mechanism 4 and an end actuator 5.

[0028] The robotic arm of the drone needs a motor or corresponding mechanism that can output a large torque to resist the gravity of the object to be picked up or the resistance of the object to be operated. According to the experience of modern industry, a motor that can output a large torque means a larger volume and a lower speed, which is not conducive to drones with limited loads. Therefore, this application uses a high-speed, low-torque, small-volume motor. The preferred model is 37GB520, with a rated voltage of 12V; the planetary reducer is designed with the help of the idea of ​​bionics.

[0029] The planetary reducer 1 includes a three-stage reduction function, the first stage is a fixed-axis gear train composed of spur gears, and the second and third stages are epicyclic gear trains composed of planetary gears and sun gears. Figure 2As shown, the planetary reducer 1 has a cylindrical overall appearance. The planetary reducer 1 includes a spur gear pair and a planetary gear and a sun gear group connected in sequence. In this embodiment, it is preferred that a group of spur gear pairs, two groups of planetary gears and a sun gear are connected in sequence. The spur gear pair is used to introduce the power of the DC motor. The spur gear pair includes a large and a small spur gear that mesh with each other, wherein the smaller gear is fixedly connected to the output shaft of the DC motor through a U-shaped groove, and the larger gear is fixedly connected to the input end of the first group of planetary gears and the sun gear of the planetary reducer 1. The power from the DC motor is transmitted through the first group of planetary gears and the sun gear. The two groups of planetary gears and the sun gear are connected end to end to realize the transmission of power, and the reduction ratio is the same. The power output end of the second group of planetary gears and the sun gear is the power output end of the planetary reducer 1. The planetary reducer 1 is provided with an installation fixing point on the outside, which is a pin hole on the two long strip connecting blocks on the outside of the planetary reducer 1. In this embodiment, there are preferably three pin holes, and holes adapted thereto are provided at corresponding positions on the drone. Hot-melt copper nuts are embedded in the holes of the drone, and then bolts are passed through the pin holes and connected to the hot-melt copper nuts to achieve the installation of the entire robotic arm on the drone. The DC motor is installed in the electronic component box 2 on the outside of the planetary reducer 1, and the axis of the DC motor is parallel to the axis of the planetary reducer. The planetary reducer 1 makes the energy utilization rate of the entire system higher and reduces energy loss. Through the above-mentioned planetary reducer, a large torque output is provided to ensure the stability and reliability of the robotic arm in complex environments.

[0030] The power output end of the planetary reducer 1 is the power input end of the parallel parallel truss mechanism 3. The parallel parallel truss mechanism includes an upper mechanical arm and a lower mechanical arm. The power output end of the planetary reducer 1 is fixedly connected to the upper mechanical arm through a threaded pair. In this embodiment, three sets of threaded pairs are preferably used to achieve fixed connection, thereby transmitting the power of the DC motor to the parallel parallel truss mechanism 3. The upper mechanical arm and the lower mechanical arm are hinged to the middle connecting plate 9. The driven arm 7 is hinged to the housing of the planetary reducer 1 and the middle connecting plate 9 respectively; the transmission arm 8 is hinged to the middle connecting plate 9, and a universal joint 17 is installed at the other end through a locating pin; the screw telescopic mechanism fixing seat 10 is hinged to the middle connecting plate 9, and is connected to another screw telescopic mechanism by a spherical hinge. In this embodiment, the hinge is used to achieve the hinge.

[0031] The parallel truss mechanism 3 is used to realize the lifting and lowering action of the multi-degree-of-freedom robot arm. Figure 3As shown, the upper segment mechanical arm and the lower segment mechanical arm are connected by a gear pair, and the mirror synchronization of the mechanical position movement of the upper segment and the lower segment is achieved by the gear pair. Specifically, the upper segment mechanical arm includes an upper transmission arm 6 and a driven arm 7, and the lower segment mechanical arm includes a lower transmission arm 8 and a screw telescopic mechanism fixing seat 10. The upper transmission arm 6, the driven arm 7, the lower transmission arm 8 and the screw telescopic mechanism fixing seat 10 are all provided with a spur gear structure at one end for connecting the upper segment mechanical arm and the lower segment mechanical arm. The gears of the upper transmission arm 6 and the lower transmission arm 8 form a set of spur gear pairs, and the gears of the driven arm 7 and the screw telescopic mechanism fixing seat 10 form a set of spur gear pairs, and the gear axis coincides with the hinge axis. The mirror synchronization of the position movement of the upper segment mechanical arm and the lower segment mechanical arm of the parallel parallel truss mechanism 3 is achieved by two pairs of gear pairs, so that the rotation of the output shaft of the DC motor is converted into the lifting and lowering movement of the multi-degree-of-freedom mechanical arm, and the spatial position of the end actuator 5 of the multi-degree-of-freedom mechanical arm is further adjusted.

[0032] The end effector 5 includes a claw 18 , which is connected to the parallel truss mechanism 3 via an ankle joint mechanism 4 .

[0033] like Figure 5 As shown, the ankle joint mechanism 4 includes a universal joint 17 and a screw telescopic mechanism. The universal joint 17 is connected to the lower transmission arm 8 and the eagle claw 18 respectively. In this embodiment, the connection is preferably completed by a positioning pin. The screw telescopic mechanism is also a component of the lower section of the mechanical arm. The screw telescopic mechanism forms a spherical hinge connection with the eagle claw 18 through the ball head at its end. Figure 4 As shown, the screw telescopic mechanism fixing seat 10 includes a spherical hinge groove, and in this embodiment, the number of spherical hinge grooves is preferably two, which form a spherical hinge with the upper end ball head of the outer sleeve motor fixing seat 11. The parallel parallel truss mechanism and the ankle joint mechanism give the robot arm flexible movement ability in multiple directions, enabling it to complete delicate operations in a small space.

[0034] like Figure 6As shown, the screw telescopic mechanism includes an outer sleeve motor fixing seat 11, an outer sleeve 12, a spiral drum 13, a small screw 14, a triangular column push rod 15, an end ball head 16 and a screw telescopic mechanism driving motor 19. The axes of all parts of the above-mentioned screw telescopic mechanism are collinear. The output shaft of the screw telescopic mechanism driving motor 19 is a D-shaped shaft. The screw telescopic mechanism driving motor 19 is installed in the outer sleeve motor fixing seat 11. The outer contour of the screw telescopic mechanism driving motor 19 is a rectangle. The interior of the outer sleeve motor fixing seat 11 is a rectangle that matches the contour of the screw telescopic mechanism driving motor 19. The screw telescopic mechanism driving motor 19 is installed therein to restrict its axial rotation; the output end of the screw telescopic mechanism driving motor 19 is fixedly connected to the spiral drum 13 through a D-shaped hole, which is convenient for the screw telescopic mechanism driving motor 19 The spiral drum 13 is driven to rotate, the outer sleeve motor fixing seat 11 and the outer sleeve 12 are fixed by bolts, and the small screw 14 is axially movable and connected in the spiral drum 13 through a threaded pair. The small screw 14, the triangular column push rod 15 and the end ball head 16 are rigidly connected. The end of the outer sleeve 12 is provided with a triangular opening matched with the triangular column push rod 15. The triangular column push rod 15 cannot rotate axially and can only make the small screw 14 produce axial linear motion through the rotation of the spiral drum 13, thereby realizing the telescopic movement of the screw telescopic mechanism.

[0035] The rotational movement of the two spiral drums 13 is controlled respectively by driving the motors 19 through two screw telescopic mechanisms. If the two screw telescopic mechanisms are extended at the same time, the connection surface of the eagle claw 18 faces forward; if the two screw telescopic mechanisms are shortened at the same time, the connection surface of the eagle claw 18 faces backward; if the screw telescopic mechanism on the left side is extended and the screw telescopic mechanism on the right side is shortened, the connection of the eagle claw 18 is tilted to the right; if the screw telescopic mechanism on the right side is extended and the screw telescopic mechanism on the left side is shortened, the connection of the eagle claw 18 is tilted to the left.

[0036] like Figure 7 As shown, the middle part of the eagle claw 18 also includes a transmission mechanism, which includes a gear pair, a thread pair and a gear rack pair. The transmission mechanism uses the eagle claw drive motor 22 as the power input source of the gear pair. The screw telescopic mechanism drive motor 19 and the eagle claw drive motor 22 are both GA12-N20, with a rated voltage of 12V. The rotation of the output shaft of the eagle claw drive motor 22 is converted into the vertical movement of the palm lifting member 25 and the rack 26 through the gear pair and the thread pair. The stability and accuracy of power transmission are guaranteed by the gear pair and the thread pair. The eagle claw enables the robot arm to perform precise grasping and releasing operations, which is suitable for a variety of application scenarios.

[0037] like Figure 8As shown, the eagle claw driving motor 22 is connected to the transmission spur gear 24 through a U-shaped groove, and the transmission spur gear 24 is meshed with the spur gear at the bottom of the screw gear 23, and is installed on the palm 21 at the same time. The palm connecting member 20 is rigidly connected to the eagle claw 18 through a threaded pair. The periphery of the palm lifting member 25 is provided with a rack 26 fixed by a slot, and a plurality of eagle fingers composed of a multi-stage gear pair are circumferentially displayed on the outside of the eagle claw 18. In this embodiment, considering the overall weight and application stability of the eagle claw 18, the preferred number of eagle fingers is 3; the first end of the first section of the eagle finger 33 is provided with a gear structure, and the rack 26 is meshed with the gear structure at the first end of the first section of the eagle finger 33. The transmission mechanism drives the synchronous movement of the eagle finger through the gear rack pair of the rack 26 to achieve the overall opening and closing action of the eagle claw 18.

[0038] like Fig. 9 As shown, the first section internal gear 31 and the second section internal gear 30 are mounted on the first section eagle finger 33 through the shaft hole, and the first section eagle finger 33 is mounted on the eagle finger bridge 34 through the shaft hole. The eagle finger bridge 34 includes a gear structure, and the first section internal gear 31 rotates under the constraint of its gear structure, converting the vertical movement of the rack into the rotation of the second section internal gear 30, and then transmitting the rotation to the second section eagle finger 32. The first end of the second section eagle finger 32 has a gear structure, and its gear structure is meshed with the second section internal gear 30. The third section internal gear 29, the fourth section internal gear 28 and the finger 27 are all mounted on the second section eagle finger 32 through the shaft hole. The third section internal gear 29, the fourth section internal gear 28 and the finger 27 are all in gear meshing relationship. The end of the first section eagle finger 33 has a gear structure, and the third section internal gear 29 rotates under the constraint of its gear structure.

[0039] In this embodiment, a position closed-loop PID control method is used for displacement control. The angular displacement of the DC motor is captured by a photoelectric encoder. The photoelectric encoder is installed at the end of the DC motor of the electronic component box 2. The encoder's code disk is fixed to the motor shaft and rotates with the motor. The actual angular displacement of the output end of the planetary reducer is obtained by the reduction ratio of the spur gear pair and the gear of the planetary reducer. The desired angular displacement and angular velocity of the output end of the planetary reducer are set, and the actual angular displacement is made to approach the desired angular displacement in combination with the PID controller, so as to further adjust the lifting degree and lifting speed of the robot arm.

[0040] The multi-degree-of-freedom motion trajectory analysis of a multi-degree-of-freedom robotic arm for a multi-rotor drone is as follows: Figure 1 The multi-degree-of-freedom robotic arm structure shown is simplified as follows Fig.10 Model shown: There is a DC motor of Part 1 at the point, which makes the robot arm rotate in the ZY plane; Point is the gear meshing joint structure, which is The relationship between the angle of motion at a point is as follows Fig.10As shown; each movement joint , , , in The motion coordinates in the coordinate system with as the origin are:

[0041]

[0042]

[0043]

[0044] express The absolute value of the coordinate of the point in the Y-axis direction; express The absolute value of the coordinate of the point in the Y-axis direction; express The absolute value of the coordinate of the point in the Y-axis direction; Indicates the connection position between the upper transmission arm 6 and the output shaft of the planetary reducer relative to the fixed position distance; Indicates the length of the upper transmission arm 6; Indicates the length of the lower transmission arm 8; Indicates the angle at which the upper transmission arm 6 is lifted.

[0045] Two screw telescopic mechanisms are used to drive the motor 19 to control the rotational movement of the two spiral drums 13 respectively. If the two spiral telescopic mechanisms are extended at the same time, the connection surface of the eagle claw 18 faces forward; if the two spiral telescopic mechanisms are shortened at the same time, the connection surface of the eagle claw 18 faces backward; if the left side is extended and the right side is shortened, the connection of the eagle claw 18 is tilted to the right; if the right side is extended and the left side is shortened, the connection of the eagle claw 18 is tilted to the left.

[0046] In order to conveniently describe its motion state, it is converted into Fig.11 The mathematical model shown: fixed point A, to A point is defined as ; The moving points B and C are symmetrical about the ZY plane. Both points are in the XY plane and move on a straight line perpendicular to the X axis. The distance between point B and point C is defined as , the motion displacement of point B is defined as , the motion displacement of point C is defined as ; Let point D be the intersection of line segment BC and the Y axis. In the coordinate system with point as the origin, the coordinates of each point are expressed as:

[0047] In the ZY plane, the pitch motion of the ankle joint mechanism is described by the angle between the direction vector of vector AD and the Z axis, and its motion angle is defined as , the movement from the positive direction of the Y axis to the positive direction of the Z axis is defined as positive movement; in the XY plane, the yaw movement of the ankle joint mechanism is described by the angle between the direction vector of the vector BC and the X axis, and its movement angle is defined as , in the YZ plane, with vector A The angle between the direction vector and the Z axis is used to describe the pitch motion of the ankle joint mechanism, and its motion angle is defined as , the movement from the positive direction of the X axis to the positive direction of the Y axis is defined as positive movement. Then the movement angle is expressed as:

[0048] In summary, the end point of the robot arm The kinematic equation is:

[0049] The PID control implementation process of the multi-degree-of-freedom robot arm is as follows: the DC motor of the multi-degree-of-freedom robot arm is simplified into a DC motor model with a real-time changing load torque at the output end. The equivalent circuit of the DC motor is as follows: Fig.12 As shown, according to Kirchhoff's law and the law of rotation of rigid body, the following equations are obtained:

[0050] Where, E is the induced electromotive force, For a given input voltage, is the motor armature current, R is the total resistance of the armature circuit, L is the total inductance of the armature circuit, is the back electromotive force constant, is the electromagnetic torque constant of the motor, is the total moment of inertia of the rotating parts converted to the motor shaft, is the electromagnetic torque, is the damping torque, D is the damping coefficient, is the angular velocity of the DC motor.

[0051] Perform Laplace transform on both sides of the equation, and we get:

[0052] and The transfer function between is:

[0053] The input of the angular velocity PID controller is the desired angular velocity, and the output control signal is the voltage acting on both ends of the motor. The input of the angular displacement PD controller is the desired angular displacement, and the output control signal is the compensation amount of the angular velocity. The angular displacement is obtained by integrating the angular velocity. The angular velocity and angular displacement PID controllers of the multi-degree-of-freedom manipulator are as follows: Fig.14 As shown, the proportional factors of the proportional link, integral link and differential link of the angular velocity PID controller are =3.4, =1.1, =0.5, the proportional factors of the proportional link, integral link and differential link of the PD controller of angular displacement are =2.9, =0, =0.9.

[0054] The above is only an embodiment of the present invention, and the common knowledge such as the known specific technical solutions and / or characteristics in the solution is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several modifications and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A multi-degree-of-freedom mechanical arm for a multi-rotor drone, characterized in that: It includes a planetary reducer, a parallel truss mechanism, an ankle joint mechanism and an end actuator; The planetary reducer comprises a spur gear pair and a planetary gear and a sun gear set connected in sequence, the DC motor output shaft is fixedly connected to the spur gear pair, the planetary gear and the sun gear are connected end to end, and have the same reduction ratio; The parallel parallel truss mechanism comprises an upper mechanical arm and a lower mechanical arm, the upper mechanical arm and the lower mechanical arm are hinged to the middle connecting plate and connected through a gear pair; the power output end of the planetary reducer is fixedly connected to the upper mechanical arm through a threaded pair; The ankle joint mechanism includes a universal joint and a screw telescopic mechanism, the universal joint is connected to the lower section mechanical arm and the eagle claw respectively; the screw telescopic mechanism is also a component of the lower section mechanical arm and is connected to the eagle claw spherical hinge; The end actuator includes an eagle claw, which includes a transmission mechanism driven by an eagle claw driving motor. The transmission mechanism includes a gear pair, a thread pair and a rack and pinion pair. The eagle finger composed of a multi-stage gear pair is circumferentially arranged on the outside of the eagle claw, and the transmission mechanism drives the eagle finger to move synchronously through the rack and pinion pair.

2. A multi-degree-of-freedom mechanical arm for a multi-rotor drone according to claim 1, characterized in that: The planetary reducer has an overall cylindrical appearance, the DC motor is installed outside the planetary reducer, and the axis of the DC motor is parallel to the axis of the planetary reducer.

3. The multi-degree-of-freedom mechanical arm for a multi-rotor drone according to claim 1, characterized in that: The spur gear pair includes a large and a small spur gear meshing with each other, wherein the smaller gear is fixedly connected to the output shaft of the DC motor through a U-shaped groove, and the larger gear is fixedly connected to the input end of a set of planetary gears and a sun gear.

4. The multi-degree-of-freedom mechanical arm for a multi-rotor drone according to claim 1, characterized in that: The upper section of the mechanical arm includes an upper transmission arm and a driven arm, and the lower section of the mechanical arm includes a lower transmission arm and a screw telescopic mechanism fixing seat. The upper transmission arm, the driven arm, the lower transmission arm and the screw telescopic mechanism fixing seat are all provided with a spur gear structure at one end for connecting the upper section of the mechanical arm and the lower section of the mechanical arm. The gears of the upper transmission arm and the lower transmission arm form a set of spur gear pairs, and the gears of the driven arm and the screw telescopic mechanism fixing seat form a set of spur gear pairs.

5. The multi-degree-of-freedom mechanical arm for a multi-rotor drone according to claim 1, characterized in that: The gear axis of the spur gear pair in the parallel truss mechanism coincides with the hinge axis.

6. The multi-degree-of-freedom mechanical arm for a multi-rotor drone according to claim 1, characterized in that: The screw rod telescopic mechanism fixing seat comprises a spherical hinge groove, and a spherical hinge is formed by the spherical hinge groove and the upper end ball head of the outer sleeve motor fixing seat.

7. The multi-degree-of-freedom mechanical arm for a multi-rotor drone according to claim 1, characterized in that: The screw telescopic mechanism includes an outer sleeve motor fixing seat with colinear axes, an outer sleeve, a spiral drum, a small screw, a triangular prism push rod, an end ball head and a screw telescopic mechanism driving motor. The screw telescopic mechanism driving motor is installed in the outer sleeve motor fixing seat. The output end of the screw telescopic mechanism driving motor is fixedly connected to the spiral drum through a D-shaped hole. The small screw moves axially in the spiral drum through a threaded pair. The small screw, the triangular prism push rod and the end ball head are rigidly connected. The end of the outer sleeve is provided with a triangular opening that matches the triangular prism push rod.

8. The multi-degree-of-freedom mechanical arm for a multi-rotor drone according to claim 1, characterized in that: The transmission mechanism adopts an eagle claw drive motor as a power input source of the gear pair, and the rotation of the output shaft of the eagle claw drive motor is converted into vertical movement of the palm lifting member and the rack through the gear pair and the thread pair.

9. The multi-degree-of-freedom mechanical arm for a multi-rotor drone according to claim 8, characterized in that: The eagle claw driving motor is connected to the transmission spur gear through a U-shaped groove, the transmission spur gear is meshed with the spur gear at the bottom of the screw gear, and is installed on the palm at the same time. The periphery of the palm lifting part is provided with a rack fixed by a slot.

10. The multi-degree-of-freedom mechanical arm for a multi-rotor drone according to claim 1, characterized in that: The eagle finger comprises an eagle finger bridge, the inner gear is mounted on the eagle finger through an axial hole, the eagle finger is mounted on the eagle finger bridge through an axial hole, and the eagle finger bridge comprises a gear structure.

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