Pull wire controlled double-spherical shell serpentine robot

Abstract

A cable-controlled double-spherical shell snake robot is disclosed. This invention relates to snake robots and aims to solve the technical problems of current snake robots, such as limited degrees of freedom and poor flexibility of individual joints, the use of servo motors to drive gear transmission components to drive joint movement, complex structure, and excessively long snake segment modules between joints resulting in insufficient driving force in order to achieve complex obstacle crossing and avoidance movements. Multiple double-spherical shell ball joints are sequentially and fixedly connected end-to-end along a straight line. The control bus on the controller passes through the internal axis of the multiple double-spherical shell ball joints and connects to the snake head from the tail. The multiple ball joints move in coordination. A cover fixing seat is fixedly installed on the outer shell, and the cover is fixedly installed on the inner shell. The inner shell is tactilely connected to the outer shell via rolling supports. Multiple cable-driven components are evenly distributed radially within the inner shell. This invention belongs to the field of snake robot technology.

Description

Technical Field

[0001] This invention relates to the field of snake robot technology, specifically to a wire-controlled double-spherical-shell snake robot. Background Technology

[0002] Snake-like robots are a new type of biomimetic robot capable of mimicking the movements of a snake. They consist of multiple snake-like modules linked together, connected by joints. By changing the angles of these joints, they can achieve snake-like movements such as bending, twisting, and crawling. Their highly redundant degrees of freedom and slender body structure allow them to maneuver in confined, winding spaces, climb and traverse various obstacles, adapting to complex terrains and environments, and performing a variety of tasks. These tasks include exploration and search and rescue, construction and maintenance, medical surgery, and military reconnaissance, demonstrating broad application prospects.

[0003] Current snake-like robots mostly use single-degree-of-freedom hinges or two-degree-of-freedom perpendicularly intersecting hinges for individual joints, which can only achieve simple two-dimensional spatial movements, losing flexibility and making the robot's control algorithm complex and unsuitable for generating accurate motion trajectories. Joint drives often employ servo motors, reducers, gear sets, and other mechanisms located inside the joint, resulting in overly complex joint structures. When using head-up movements to achieve obstacle-crossing, excessively long snake segments make the snake body structure too large, leading to slightly insufficient driving force. Summary of the Invention

[0004] The purpose of this invention is to address the technical problems of current snake robots, such as limited degrees of freedom and poor flexibility of individual joints, the use of servo motors to drive gear transmission components for joint movement resulting in complex structures, and the excessive length of the snake segments between joints leading to insufficient driving force in order to achieve complex obstacle crossing and avoidance movements. This invention provides a cable-controlled double-spherical shell snake robot.

[0005] The technical solution of this invention is:

[0006] A wire-controlled double-spherical-shell snake robot includes a controller and multiple double-spherical-shell ball joints. The multiple double-spherical-shell ball joints are sequentially and fixedly connected end-to-end along a straight line. A control bus on the controller passes through the internal axis of the multiple double-spherical-shell ball joints and connects to the snake's head from the tail. The multiple ball joints move in coordination. Each double-spherical-shell ball joint includes a cover fixing seat, a cover, an inner shell, an outer shell, rolling supports, multiple wire-driven components, and multiple external supports. The cover fixing seat is fixedly mounted on the outer shell, and the cover is fixedly mounted on the inner shell. The inner shell is tactilely connected to the outer shell via rolling supports. Multiple wire-driven components are radially and evenly distributed within the inner shell. The driving end of each wire-driven component is mounted on a lower end face of the cover, and the fixed end of each wire-driven component is mounted on the upper end face of the cover fixing seat. Multiple external supports are radially and evenly distributed and fixedly mounted on the outer circumferential surface of the outer shell. The cover of each double-spherical-shell ball joint is fixedly mounted on the cover fixing seat of the adjacent double-spherical-shell ball joint.

[0007] Furthermore, each pull-wire drive assembly includes three drive motor mounts, three drive motors, three pull wires, and three pull-wire connectors; the three drive motor mounts are radially and evenly fixedly installed on the lower end face of the cover, each drive motor mount has a drive motor connected to a ball joint, the drive end of each drive motor is fixedly connected to one end of a pull wire, the other end of each pull wire is fixedly installed with a pull-wire connector, and the three pull-wire connectors are radially and evenly fixedly installed on the upper end face of the cover mounting base.

[0008] Furthermore, the drive motor is an electric linear actuator motor, and the drive end of the electric linear actuator motor is fixedly connected to one end of the pull wire.

[0009] Furthermore, the pull line is a rope, and the connector at one end of the pull line is connected to the upper end face of the cover fixing seat through a pull line connector fixing screw.

[0010] Furthermore, the controller is a microcontroller controller.

[0011] Furthermore, a protrusion is machined on the other end face of the cover, and a groove is machined on the other end face of the cover fixing seat. The protrusion of the cover on each pull-wire drive assembly is inserted into the groove of the cover fixing seat on the adjacent pull-wire drive assembly, and multiple fixing screws are inserted into the protrusion of the cover and the groove of the cover fixing seat.

[0012] Furthermore, the inner shell is a shell larger than a hemisphere, the outer shell is a shell larger than a hemisphere, multiple outer ball bearing tracks are evenly distributed on the outer circular surface of the inner shell, and multiple inner ball bearing tracks are evenly distributed on the inner circular surface of the outer shell.

[0013] Furthermore, the rolling support includes a ball cage and a plurality of balls; the plurality of balls are disposed in the ball holes of the ball cage, the ball cage is disposed between the inner housing and the outer housing, and each ball is in rolling contact with an outer ball track of the inner housing and an inner ball track of the outer housing, respectively.

[0014] Furthermore, the external support includes an external fixing frame and pulleys; multiple external fixing frames are radially fixedly installed on the outer circular surface of the outer casing, and each pulley is installed on the external fixing frame.

[0015] Furthermore, the pulley is in a locked state, and an anti-slip sleeve is fitted over the pulley.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] 1. The wire-controlled double-spherical-shell snake robot of this application is equipped with at least three wire drive components 7 for each joint. That is, the drive motor 72 drives the wires 73 to extend or shorten. Because the wires are in the form of ropes, they have the characteristic of unidirectional force. Based on the principle of "three points determine a plane," only the coordinated extension and contraction of the three wires 73 is controlled, thereby realizing the three-dimensional rotation between the two spherical shells. Multiple double-spherical-shell ball joints are connected in series to achieve more flexible three-dimensional spatial movement, thus meeting the various gait and complex action requirements of the snake robot. In this application, each joint is flexible, and the three wire joints are equivalent to three points, which determine a plane, controlling the rotation angle between the two spherical shell planes.

[0018] 2. The cable-controlled double-spherical-shell snake robot of this application increases the driving torque of the robot by increasing the number of cable drive components 7 according to the actual working load requirements. This results in a shorter transmission chain. The drive motor 72 directly drives the cable 73 to rotate the joint, replacing the servo motors, gear sets, and other transmission components of conventional snake robots, thus achieving high transmission accuracy. The reduced joint weight also lightens the overall robot weight. The hollow joint structure design further reduces friction between cables, lowering the complexity of the joint structure and reducing power consumption. This application increases the number of cables, increases the joint driving force, and features a short transmission chain and compact structure.

[0019] 3. The wire-controlled double-spherical shell snake robot of this application has multiple double-spherical shell ball joints directly connected through the cover 2 and the cover fixing seat 1, which effectively shortens the body length of the snake segment module of conventional snake robots, making the snake body easier to bend, the structure more compact, and closer to the release behavior of biological snakes. The snake segment size of this application is small, the distance between the joints is small, and the snake body is easier to bend.

[0020] 4. The wire-controlled double-spherical-shell snake robot of this application is equipped with an electric push rod 72 that detects the output of the push rod, enabling precise control of the extension and retraction of the wire, and thus precise control of the rotation angle of the rotating joints. Compared with conventional snake robots that have angle sensors installed on all joints, this significantly reduces cost and structure.

[0021] 5. The cable-controlled double-spherical-shell snake robot of this application features a reconfigurable modular design for each joint. Each joint has the same structure and working principle, allowing for flexible configuration and expansion by adjusting the snake's body length according to the specific working conditions. This facilitates easier robot construction and maintenance. Pitch and lateral rotation are both cable-driven. A controller sends signals to the motors, causing them to move and drive the cables in a reciprocating motion. This, in turn, pulls the spherical-shell joints, causing the unit modules to reciprocate. This results in the oscillation of the next module connected to the upper end cap, which, through friction with the ground, achieves forward movement in three-dimensional space, indirectly contributing to the regular oscillation of the snake robot's body. Each push rod motor is equipped with a push rod output sensor, enabling real-time and precise control of joint rotation. This modular design is low-cost and easy to maintain and expand.

[0022] 6. The snake-like robot of this application helps to improve the application technology level of snake-like robots in terms of flexibility, high energy efficiency, and sophistication, and enhances their ability to adapt to complex environments, which is of great research significance. The double-spherical shell structure design replaces the joint servo motors to reduce joint complexity and improve drive conversion efficiency; the screw connection enables flexible snake movement, easy control, and the ability to avoid obstacles of multiple complex shapes. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of the present invention.

[0024] Figure 2 This is a schematic diagram showing the connection between two adjacent pull-wire drive components 7.

[0025] Figure 3 yes Figure 1 HH view.

[0026] Figure 4 yes Figure 1 View from the center (I direction).

[0027] Figure 5 This is a simplified schematic diagram of a wire-controlled double-spherical-shell joint. Detailed Implementation

[0028] Specific implementation method one: Combining Figure 1This embodiment describes a wire-controlled double-spherical-shell snake robot, which includes a controller and multiple double-spherical-shell ball joints. The multiple double-spherical-shell ball joints are sequentially and fixedly connected end-to-end along a straight line. A control bus on the controller passes through the internal axis of the multiple double-spherical-shell ball joints and connects to the snake's head from the tail. Through the coordinated movement of the multiple ball joints, the snake robot can perform various walking gaits and complex snake-like movements. Each double-spherical-shell ball joint includes a cover fixing seat 1, a cover 2, an inner shell 3, an outer shell 4, a rolling support 5, multiple wire-driven components 7, and multiple external support components. 6; The cover fixing seat 1 is fixedly installed on the outer shell 4, the cover 2 is fixedly installed on the inner shell 3, the inner shell 3 is rolledly connected to the outer shell 4 through the rolling support 5, multiple pull-wire drive components 7 are evenly distributed radially in the inner shell 3, and the driving end of each pull-wire drive component 7 is installed on a lower end face of the cover 2, and the fixing end of each pull-wire drive component 7 is installed on the upper end face of the cover fixing seat 1, multiple external support components 6 are evenly distributed radially and fixedly installed on the outer circular surface of the outer shell 4, and the cover 2 of each double spherical joint is fixedly installed on the cover fixing seat 1 of the adjacent double spherical joint.

[0029] Specific Implementation Method Two: Combining Figure 1 This embodiment describes a pull-wire controlled double-spherical-shell snake robot. Each pull-wire drive assembly 7 includes three drive motor seats 71, three drive motors 72, three pull wires 73, and three pull wire connectors 74. The three drive motor seats 71 are radially and evenly fixedly installed on the lower end face of the cover 2. Each drive motor seat 71 is connected to a drive motor 72 via a ball joint. The drive end of each drive motor 72 is fixedly connected to one end of a pull wire 73. The other end of each pull wire 73 is fixedly installed with a pull wire connector 74. The three pull wire connectors 74 are radially and evenly fixedly installed on the upper end face of the cover fixing seat 1.

[0030] The drive motor mount 71 is a motor that drives the pull cable 73 to stretch and retract. The lengths of the three pull cables 73 are controlled by the three pull cable connectors 74 within the length traction component 7, thus controlling the position of the inner shell 3 on the outer shell 4 and achieving the overall shape of the snake-like robot. Other components and connections are the same as in Specific Embodiment 1.

[0031] Taking a single joint as an example, the two spherical shells form a spherical pair, which is driven by three pull ropes. The extension and retraction of the three pull ropes enable the two spherical shells to rotate relative to each other. The specific joint rotation angle is controlled by the extension and retraction of the three pull ropes. When all joints can rotate in coordination, the mechanical snake can achieve various walking gaits.

[0032] Specific implementation method three: Combining Figure 1This embodiment describes a wire-controlled double-spherical snake robot. The drive motor 72 is an electric push rod motor, and its drive end is fixedly connected to one end of the wire 73. Other components and connections are the same as in specific embodiment two.

[0033] Specific implementation method four: Combination Figure 1 This embodiment describes a pull-wire controlled double-spherical-shell snake robot. The pull wire 73 is a rope, and one end of the pull wire 73 is connected to the upper surface of the cover fixing base 1 via a pull wire connector fixing screw 75. Other components and connections are the same as in specific embodiment three.

[0034] Specific Implementation Method Five: Combining Figure 1 This embodiment describes a cable-controlled double-spherical-shell snake robot, with a microcontroller as the controller. Multiple cable-controlled double-spherical-shell ball joints swing in tandem, causing the snake's body to undergo S-shaped undulations, generating forward and turning power, thus enabling the snake robot to crawl on the ground. The three cable-driven components 7 of each double-spherical-shell ball joint are centrally controlled by an external controller. The control bus on the controller connects sequentially from the snake's tail to its head, passing through the inner bore of the axis of each double-spherical-shell ball joint. Other components and connections are the same as in Embodiment Two.

[0035] Specific Implementation Method Six: Combination Figure 1 This embodiment describes a pull-wire controlled double-spherical-shell snake robot. The other end face of the cover 2 is machined with a protrusion, and the other end face of the cover fixing seat 1 is machined with a groove. The protrusion of the cover 2 on each pull-wire drive assembly 7 is inserted into the groove of the cover fixing seat 1 on an adjacent pull-wire drive assembly 7, and multiple fixing screws are inserted into the protrusion of the cover 2 and the groove of the cover fixing seat 1.

[0036] The cover 2 and the cover fixing base 1 are fixedly connected by fixing screws. Other components and connections are the same as in specific embodiment two.

[0037] Specific implementation method seven: Combination Figure 1 This embodiment describes a wire-controlled double-spherical-shell snake robot. The inner shell 3 is larger than a hemisphere, and the outer shell 4 is also larger than a hemisphere. Multiple external ball bearing tracks are evenly distributed on the outer circumferential surface of the inner shell 3, and multiple internal ball bearing tracks are evenly distributed on the inner circumferential surface of the outer shell 4. Other components and connections are the same as in Specific Embodiment One.

[0038] Specific implementation method eight: Combination Figure 1This embodiment describes a wire-controlled double-spherical-shell snake robot. The rolling support 5 includes a ball retainer 51 and multiple balls 52. The balls 52 are disposed within the ball holes of the ball retainer 51, which is located between the inner shell 3 and the outer shell 4. Each ball 52 is in rolling contact with an outer ball track of the inner shell 3 and an inner ball track of the outer shell 4. Other components and connections are the same as in specific embodiment five.

[0039] Specific Implementation Method Nine: Combining Figure 1 This embodiment describes a wire-controlled double-spherical-shell snake robot. The external support 6 includes an external fixing frame 61 and pulleys 62. Multiple external fixing frames 61 are radially fixedly mounted on the outer circumferential surface of the outer shell 4, and each pulley 62 is mounted on an external fixing frame 61. Other components and connections are the same as in specific embodiment five.

[0040] Specific Implementation Method Ten: Combining Figure 1 This embodiment describes a cable-controlled double-spherical snake robot. The pulley 62 is in a locked state, and an anti-slip sleeve is fitted over the pulley 62. Other components and connections are the same as in specific embodiment five.

[0041] The mapping relationship between the change in rotation angle of the double-spherical joint controlled by the wires and the change in the length of the three wires, such as... Figure 5 As shown,

[0042] Surface M1M2M3 is a plane consisting of three points connecting the bases of the three electric actuators to the cover plate. Surface N1N2N3 is a plane consisting of the three connecting heads of the pull wires on the three electric actuators and the cover plate fixing seats. Line segments M1N1, M2N2, and M3N3 represent three independent pull wires L1, L2, and L3, respectively. Points O1 and O2 are the origins of the centers of surfaces M1M2M3 and N1N2N3, respectively. The direction perpendicular to the plane is the Z-axis, and the directions of rotation for the two degrees of freedom are the X-axis and Y-axis. Coordinate systems {1} and {2} are established. Assuming the initial distance between the origins of the coordinate systems M1M2M3 and N1N2N3 is d, then for coordinate systems {1} and {2}, when {1} rotates around its X-axis by an angle θ and translates upwards by d, O1 and O2 coincide. After rotating around the Y-axis by an angle α, it coincides with {2}. Thus, the homogeneous transformation matrix can be obtained:

[0043] (Formula 1)

[0044] Take point N on the surface N1N2N3 , ∠N O X =90°. Then, on plane M1M2M3, N... The corresponding point M There is also ∠M O X =90°, from {1} we can obtain:

[0045] (Formula 2)

[0046] In {2}:

[0047] (Formula 3)

[0048] From the previous calculations, the solution can be found for:

[0049] (Formula 4)

[0050] Therefore, further calculations yield the length L of the guy wire. for:

[0051] (Formula 5)

[0052] Similarly, we can obtain The length formula is used. By controlling the different lengths of the three tension wires, the three-dimensional angular dimensions of the ball joint can be calculated.

[0053] The wire-controlled double-spherical-shell snake robot of this application uses the Serpeniod curve proposed by Professor Hirose for control, and its curvature equation is:

[0054] (Formula 6)

[0055] In the formula, S is the displacement of the snake robot along the direction of the Serpenoid curve, L represents the total length of the snake robot's body, Kn is the number of waveforms during the undulation of the curve, and α0 is the joint angle at the start of the movement.

[0056] Discretizing Equation 6 into this snake-like robot, we can obtain the joint angle function of the snake-like robot's crawling gait: (Formula 7)

[0057] In the formula, i∈1,…,N, N is the total number of robot joints, is the amplitude of joint movement, which determines the degree of bending of the robot's body during movement; is the angular frequency of joint movement, which determines the speed of body swaying during robot movement; δ represents the angular phase difference between adjacent joints, which determines the number of robot body waves. Joint offset determines the robot's forward direction during serpentine motion. When >0, the robot turns right. When the value is less than 0, the robot turns left.

[0058] The above equation only describes the joint angle control of a planar snake robot. For the snake robot model in this application, the joints can be divided into pitch joints and yaw joints to control the posture of the snake robot separately. The control function can be expressed as:

[0059] (Formula 8)

[0060] In the formula, and Let represent the joint angles of the i-th pitch and yaw joints, respectively, i∈1,…,N / 2, where N is the total number of robot joints. and These represent the amplitudes of the pitch and yaw joints, respectively. and These are the angular frequencies of the pitch and yaw joints, respectively. and These are the angular phase differences between adjacent joints of the pitch and yaw joints, respectively. and These refer to the joint offsets of the pitch and yaw joints, respectively. The phase difference between the pitch and yaw joints is used to control the time difference between two orthogonal waveform motions.

[0061] Taking the serpentine robot's meandering motion on a plane as an example, only the yaw joint rotates, while the pitch joint angle is zero. The joint angle control function for the meandering motion is:

[0062] (Formula 9)

Claims

1. A wire-controlled double-spherical-shell snake robot, characterized in that: It includes a controller and multiple double-spherical ball joints; Multiple double-spherical joints are fixedly connected end to end in a straight line. The control bus on the controller passes through the internal axis of the multiple double-spherical joints and is connected from the tail to the head. Through the coordinated movement of multiple joints, the double-spherical joint includes a cover fixing seat (1), a cover (2), an inner shell (3), an outer shell (4), a rolling support (5), multiple pull-wire drive assemblies (7), and multiple external support members (6). The cover fixing seat (1) is fixedly installed on the outer shell (4), the cover (2) is fixedly installed on the inner shell (3), and the inner shell (3) is fixedly installed on the outer shell (4). The outer shell (4) is connected by a rolling support (5). Multiple pull-wire drive components (7) are evenly distributed radially within the inner shell (3). The drive end of each pull-wire drive component (7) is installed on a lower end face of the cover (2). The fixed end of each pull-wire drive component (7) is installed on the upper end face of the cover fixing seat (1). Multiple external support components (6) are evenly distributed radially and fixedly installed on the outer circular surface of the outer shell (4). The cover (2) of each double-spherical joint is fixedly installed on the cover fixing seat (1) of the adjacent double-spherical joint.

2. The wire-controlled double-spherical-shell snake robot according to claim 1, characterized in that: Each pull-wire drive assembly (7) includes three drive motor mounts (71), three drive motors (72), three pull wires (73), and three pull-wire connectors (74); the three drive motor mounts (71) are evenly distributed and fixedly installed on the lower end face of the cover (2) in a radial direction, and a drive motor (72) is connected to each drive motor mount (71) by a ball joint. The drive end of each drive motor (72) is fixedly connected to one end of a pull wire (73), and a pull-wire connector (74) is fixedly installed on the other end of each pull wire (73). The three pull-wire connectors (74) are evenly distributed and fixedly installed on the upper end face of the cover fixing seat (1) in a radial direction.

3. The wire-controlled double-spherical-shell snake robot according to claim 2, characterized in that: The drive motor (72) is an electric linear actuator motor, and the drive end of the electric linear actuator motor is fixedly connected to one end of the pull wire (73).

4. The wire-controlled double-spherical-shell snake robot according to claim 3, characterized in that: The pull line (73) is a rope, and the connector (74) at one end of the pull line (73) is connected to the upper surface of the cover fixing seat (1) through the pull line connector fixing screw (75).

5. The wire-controlled double-spherical-shell snake robot according to claim 2, characterized in that: The controller is a single-chip microcontroller.

6. The wire-controlled double-spherical shell snake-like robot according to claim 2, wherein: The other end face of the cover (2) is machined with a protrusion, and the other end face of the cover fixing seat (1) is machined with a groove. The protrusion of the cover (2) on each pull wire drive assembly (7) is inserted into the groove of the cover fixing seat (1) on the adjacent pull wire drive assembly (7), and multiple fixing screws are inserted into the protrusion of the cover (2) and the groove of the cover fixing seat (1).

7. The dual-spherical shell and wire controlled snake-like robot according to claim 1, wherein: The inner shell (3) is a shell larger than a hemisphere, and the outer shell (4) is a shell larger than a hemisphere. Multiple outer ball bearing tracks are evenly distributed on the outer circular surface of the inner shell (3), and multiple inner ball bearing tracks are evenly distributed on the inner circular surface of the outer shell (4).

8. A wire-controlled double-spherical-shell snake robot according to claim 5, characterized in that: The rolling support (5) includes a ball retainer (51) and a plurality of balls (52); the plurality of balls (52) are disposed in the ball holes of the ball retainer (51), the ball retainer (51) is disposed between the inner housing (3) and the outer housing (4), and each ball (52) is in rolling contact with an outer ball track of the inner housing (3) and an inner ball track of the outer housing (4).

9. A wire-controlled double-spherical-shell snake robot according to claim 5, characterized in that: The external support (6) includes an external fixing frame (61) and a pulley (62); multiple external fixing frames (61) are fixedly installed radially on the outer circular surface of the outer casing (4), and each pulley (62) is installed on the external fixing frame (61).

10. The wire controlled double-spherical shell snake-like robot according to claim 5, wherein: The pulley (62) is in a locked state, and the pulley (62) is covered with an anti-slip sleeve.

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