A slender, multi-degree-of-freedom flexible robotic arm combining local and wire-driven actuation

Abstract

This invention discloses a slender, multi-degree-of-freedom flexible robotic arm combining local drive and wire drive, comprising a system chassis, a connecting rod base, multiple connecting rods connected end-to-end, joint shafts, a self-locking module, and a drive module. The joint shaft has a polygonal segment in the middle and circular segments at both ends, forming a rotatable connection with the polygonal and circular through holes on the connecting rods. The sidewalls of the connecting rods have four drive wire through holes, and the joint shaft has corresponding through holes at both ends, forming a four-channel drive wire path. The self-locking module includes a self-locking motor, a slider, a self-locking push rod, and a self-locking gear fixed to the joint shaft. The end of the self-locking push rod has a rack structure, directly driven by the self-locking motor to engage or disengage with the self-locking gear. The drive module, mounted on the system chassis, includes four drive motors, each driving one of the four drive wires. This invention achieves independent drive of multiple joints with only four drive wires, eliminating the need for additional trigger wires or selection mechanisms, achieving control decoupling and reliable attitude maintenance.

Description

Technical Field

[0001] This invention belongs to the field of robot structure design and special operation equipment technology, specifically relating to a slender, multi-degree-of-freedom flexible robotic arm that combines local drive and wire drive. This robotic arm can be applied to confined spaces, complex obstacle environments, and special operation scenarios with certain dangers, and is particularly suitable for tasks such as nuclear power plant operation and maintenance, equipment repair in nuclear fuel processing areas, foreign object removal, and online detection. It can also serve as the support mechanism for the robotic arm body or the end effector and detection module in radiation-resistant industrial robot systems. Background Technology

[0002] Slender, multi-degree-of-freedom robotic arms, characterized by their slender structure, numerous joints, high degrees of freedom, and large end-effector workspace, are widely used in tasks such as on-orbit operation on space stations, maintenance in confined spaces, and target grasping and transfer. In recent years, such robotic arms have also shown urgent demand in civilian and industrial fields, including nuclear power plant operation and maintenance, complex equipment inspection, and confined space auxiliary operations. To adapt to attitude adjustment in complex environments and confined space operations, robotic arms need to meet requirements of lightweighting and miniaturization while possessing sufficient structural rigidity and high motion flexibility. Therefore, how to reduce the body mass, simplify the structural layout, and improve attitude maintenance capabilities while ensuring the robotic arm's motion capabilities has always been a crucial issue in the design of slender, multi-degree-of-freedom robotic arms.

[0003] In existing technologies, slender multi-degree-of-freedom robotic arms are mainly divided into two categories: locally driven and wire-driven. The locally driven approach directly arranges the drive motor, reducer, and associated transmission components near each joint, with each joint's rotation controlled by a local drive unit. The advantage of this approach is a shorter transmission chain and a relatively intuitive control relationship. However, for slender, serially driven robotic arms, as the number of joints increases, multiple drive units need to be distributed sequentially along the robotic arm body, easily leading to increased volume, concentrated mass, complex wiring at the joints, and further increasing the load requirements of upstream joints. To reduce the weight of the robotic arm body, wire-driven (or rope-driven, tendon-driven) solutions concentrate the drive source at the base or away from the joints, achieving joint movement through changes in the length of the drive wire. This helps reduce end-effector inertia and improve the structural burden of the slender robotic arm. However, as the degrees of freedom of the robotic arm gradually increase, if each joint is equipped with an independent drive wire, the number of wires will increase significantly, making wiring, tensioning, installation, and maintenance more difficult. If multiple joints share some drive wires, it can easily introduce inter-joint coupling, causing the movement of one joint to affect the posture of another, thus increasing the difficulty of control and structural design. In recent years, Harbin Institute of Technology (Shenzhen) has published a paper titled "Reconfigurable Tendon-Driven Robots: Eliminating Inter-segmental Coupling via Independently Lockable Joints" (Lin et al., hereinafter referred to as the RTR scheme), proposing a reconfigurable tendon-driven robot. This robot utilizes a set of four driving tendons running through all joints to achieve spatial bending. An execution module consisting of additional locking / unlocking trigger tendons, belt-driven tracks, selection motors, and locking / unlocking actuator motors selectively locks or releases target joints under a time-phased strategy, thereby reducing inter-segment coupling. This paper discloses a reconfigurable tendon-driven robot employing a trigger-slider locking mechanism and additional locking / unlocking tendons. The switching of its locking state relies on a dedicated selection actuator that aligns with the target pulleys one by one for triggering, representing a single-joint gating locking / unlocking structure. While this scheme can lock multiple joints at different stages through step-by-step operations, its hardware execution path is essentially serial, meaning that state switching only occurs for one selected target joint at a time.This approach offers insights into segmented drive for tendon-driven robots, but it suffers from the following drawbacks: First, each joint requires two independent trigger tendons to lock and unlock. As the number of joints increases, the total number of wires in the robot increases significantly (four drive tendons + 2N trigger tendons), which is detrimental to the internal wiring and lightweight design of slender robotic arms. Second, the locking function relies on a complex mechanical selection mechanism (including belt-driven tracks, selection motors, multiple pulleys, and microswitches). This mechanism occupies a large space and is difficult to integrate into the slender joints. Third, the entire drive system requires six motors (four for driving bending and two for locking selection and execution), resulting in high system complexity and a long control chain.

[0004] In summary, existing slender multi-DOF robotic arms, when achieving independent control of multiple joints, suffer from several drawbacks: concentrated volume and mass in local drive schemes; severe control coupling and numerous wires in pure wire drive schemes; existing locking schemes (such as RTR schemes) rely on additional trigger wires and complex selection mechanisms; and it is difficult to achieve a compact structure, low wire count, and simple drive chain while maintaining a slender structure. Therefore, there is an urgent need to propose a new slender multi-DOF spatial flexible robotic arm structure that retains the advantage of wire drive in reducing body weight, while integrating the joint axis connection structure, drive wire routing path, and locking mechanism into a single design. This allows multiple joints to be driven by a smaller number of drive wires and enables selective locking of non-target joints. This simplifies the structure, reduces the number of wires, and lowers control complexity, while also considering the extension of the robotic arm's end effector, attitude maintenance, and engineering feasibility. Summary of the Invention

[0005] The purpose of this invention is to provide a slender, multi-degree-of-freedom spatial flexible robotic arm that combines local drive and wire drive, in order to solve the problems of large mass and volume of local drive schemes, large number of wires and severe control coupling in pure wire drive schemes, existing locking schemes (such as RTR schemes) rely on additional trigger wires and complex selection mechanisms, and it is difficult to achieve a compact structure, low number of wires and simple drive links while maintaining a slender structure.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] This invention provides a slender, multi-degree-of-freedom spatial flexible robotic arm that combines local drive and wire drive, including a system chassis, a link base, N links connected end to end in sequence, a joint shaft, a drive wire, a self-locking module, and a drive module.

[0008] Where N≥2, a first joint is formed between the connecting rod base and the first connecting rod, and second to Nth joints are formed sequentially between adjacent connecting rods. A joint shaft is provided between each adjacent connecting rod, the joint shaft having a polygonal segment in the middle and circular segments at both ends; a polygonal through hole is provided on one side of the connecting rod corresponding to the polygonal segment, and a circular through hole is provided on the other side of the connecting rod corresponding to the circular segment. Through this structure, one side of the connecting rod is circumferentially fixed to the joint shaft, while the other side of the connecting rod can rotate around the joint shaft, achieving a rotatable joint connection without additional fasteners, and simultaneously providing a stable mounting base for the self-locking gear.

[0009] Four drive wires are inserted into the multiple connecting rods. Each connecting rod has four drive wire through holes spaced circumferentially on its sidewall. Each joint axis has corresponding through holes at both ends. The four drive wires pass through the drive wire through holes on each connecting rod and the through holes on each joint axis sequentially, forming a continuous four-channel drive wire path. This corresponding arrangement of the drive wire through holes and through holes ensures that when the joint rotates around its joint axis, two of the four drive wires passing through the joint axis maintain a constant length, while the lengths of the other two change. This reduces the mapping complexity of the multi-joint wire drive control and minimizes friction between the wires and the hole walls.

[0010] The self-locking module is configured for each joint and includes a self-locking motor installed in the connecting rod or connecting rod base, a slider driven by the self-locking motor, a self-locking push rod connected to the slider, and a self-locking gear fixed to the corresponding joint shaft. The end of the self-locking push rod has a rack structure. Driven by the self-locking motor, the self-locking push rod moves linearly. When the rack structure engages with the self-locking gear, the corresponding joint is locked; when the rack structure disengages from the self-locking gear, the corresponding joint is unlocked. The locking and unlocking actions of the self-locking module are directly completed by the self-locking motor at each joint, without relying on additional trigger wires, selection motors, or independent locking / unlocking execution modules.

[0011] The drive module is mounted on the system chassis and includes four drive motors, winding wheels connected to the output ends of each drive motor, and guide wheels. Each of the four drive motors drives four drive wires. The drive motors, through the winding wheels, in turn wind and unwind the drive wires, thereby driving the corresponding joints to rotate. The four drive motors of the drive module are connected to a controller, which controls the forward and reverse rotation and starts / stops of the drive motors, and coordinates with the self-locking motors at each joint.

[0012] In a preferred embodiment, the polygonal segment is a regular polygonal cross-section, the polygonal through hole is a regular polygonal through hole that mates with the regular polygonal cross-section, and a bearing is provided between the circular segment and the circular through hole to reduce rotational resistance and improve joint rotational stability.

[0013] As a preferred embodiment, the connecting rod and the connecting rod base are provided with a receiving space for installing the self-locking motor. The self-locking motor, the slider, and the self-locking push rod are all disposed in the receiving space, so that the self-locking structure can be miniaturized and integrated near the joint.

[0014] As a preferred embodiment, when N=4, the rotation axes of the first and third joints are parallel to each other, the rotation axes of the second and fourth joints are parallel to each other, and the rotation axis directions of adjacent joints are orthogonal in sequence, thereby forming two sets of parallel axis joint pairs, providing a structural basis for the decoupled driving mode that combines shared drive wire and local self-locking.

[0015] As a preferred embodiment, the last link is provided with an end connection structure, which is used to connect an end effector or continue to connect other links to increase the functionality or degrees of freedom of the robotic arm.

[0016] As a preferred embodiment, among the four drive wires, every two drive wires form a pair to drive the same joint or the same group of parallel rotating shaft joints in opposite directions of rotation, thereby establishing driving torques in opposite directions on the corresponding joints and improving the reversibility and control accuracy of joint rotation.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. High structural integration, achieving a self-locking solution without additional trigger wires: This invention sets an independent self-locking motor at each joint, directly driving the rack and pinion meshing mechanism to achieve locking and unlocking. Compared with the existing RTR solution (which relies on additional trigger tendons, belt-driven tracks, and selector motors), this invention does not require any additional trigger wires, selector mechanisms, or independent locking / unlocking execution modules. The number of drive wires in the whole machine is simplified from "four drive tendons + 2N trigger tendons" to only four drive wires, resulting in a simpler structure and easier integration into slender joints.

[0019] 2. Novel joint shaft structure, no need for additional fasteners: The present invention adopts a composite cross-section joint shaft with a polygonal segment in the middle and circular segments at both ends. It cooperates with the polygonal and circular through holes on the connecting rod to realize the function of "one side of the connecting rod is circumferentially fixed to the joint shaft, and the other side of the connecting rod rotates around the shaft". No additional fasteners such as keys, pins or screws are needed, which simplifies the joint structure, improves assembly efficiency, and provides a stable installation foundation for the self-locking gear.

[0020] 3. Optimized drive wire routing to reduce control complexity: This invention sets four drive wire through holes on the side wall of each connecting rod and corresponding through holes at both ends of the joint shaft. Through the positional correspondence design, when the joint rotates around the shaft, the lengths of two drive wires remain unchanged and the lengths of two drive wires change. This simplifies the drive mapping from "all four wires change" to "two change and two remain unchanged", reducing the mapping complexity of multi-joint wire drive control. At the same time, it reduces the friction between the wires and the hole walls, improving transmission stability and repeatability.

[0021] 4. Simplified drive system with centralized control: This invention centralizes the drive module on the system chassis, using only four drive motors to drive four drive wires. Compared to the RTR solution which requires six motors (four drive motors + two locking control motors), the number of drive motors is reduced, and complex mechanical selection mechanisms are eliminated. The drive motors work in conjunction with the self-locking motors of each joint, enabling sequential control of "non-target joint locking – target joint driving – target joint locking," simplifying the drive system while retaining independent control capabilities for multiple joints.

[0022] 5. Modular design for easy expansion: This invention adopts a modular design approach, with clear boundaries between the connecting rods, self-locking modules, drive modules, and end-effector connection structures. It is suitable for both basic four-degree-of-freedom configurations and extended applications with more degrees of freedom. The end-effector connection structure can connect to end actuators such as grippers, probes, and sensors, or continue to connect additional connecting rods, providing excellent functional expandability and platform adaptability.

[0023] 6. Supports parallel locking of multiple joints with fast response speed: Unlike the serial locking method of RTR schemes that rely on a common selection mechanism to align the target joints one by one, this invention sets an independent self-locking motor at each joint. Each self-locking module is directly driven by the self-locking motor of the corresponding joint, without relying on a common locking selection mechanism. Therefore, the system structure supports locking multiple selected joints at the same time, which is beneficial for achieving rapid posture maintenance and parallel state switching of multiple joints in slender multi-degree-of-freedom robotic arms, thereby improving work efficiency.

[0024] In summary, while retaining the advantage of wire-driven reduction of body weight, this invention achieves a compact structure, simplified drive, and decoupled control for a multi-joint slender robotic arm through the integration of a composite cross-section joint shaft, a four-channel drive wire path and wire hole corresponding arrangement, an independent motor direct drive rack-gear self-locking structure, and a base-centralized four-motor drive system. This provides a highly feasible robotic arm structure solution for fields such as nuclear power plant operation and maintenance, confined space operations, and complex environment monitoring. Attached Figure Description

[0025] Figure 1This is a schematic diagram of the overall structure of a robotic arm according to an embodiment of the present invention, showing the overall assembly relationship of the base, connecting rod base, four connecting rods, four joints, and end-effector connection structure.

[0026] Figure 2 This is a schematic diagram of a joint structure according to an embodiment of the present invention. Taking the second joint as an example, it illustrates the structure of the joint shaft connecting adjacent connecting rods, including the arrangement of polygonal through holes, circular through holes, and bearings.

[0027] Figure 3 This is a schematic diagram of a joint shaft structure according to an embodiment of the present invention, showing a composite cross-sectional structure with a polygonal segment in the middle and circular segments at both ends, as well as wire-passing holes at the ends.

[0028] Figure 4 This is a schematic diagram of the connecting rod end and drive wire through-hole arrangement according to an embodiment of the present invention, showing the positional relationship of four drive wire through-holes spaced apart along the circumferential direction at the connecting rod end.

[0029] Figure 5 This is a schematic diagram illustrating the assembly relationship between the self-locking motor and the slider in a self-locking assembly according to an embodiment of the present invention.

[0030] Figure 6 This is a schematic diagram of the structure of a self-locking push rod according to an embodiment of the present invention, showing the specific shape of the rack structure at the end of the self-locking push rod.

[0031] Figure 7 This is a schematic diagram of a self-locking gear structure according to an embodiment of the present invention, showing the shape of the self-locking gear fixed on the joint shaft.

[0032] Figure 8 This is a schematic diagram of the joint unlocking state according to an embodiment of the present invention, showing the state of the joint when the rack structure and the self-locking gear are disengaged.

[0033] Figure 9 This is a schematic diagram of the joint locking state according to an embodiment of the present invention, showing the state of the joint when the rack structure and the self-locking gear are engaged.

[0034] Figure 10 This is a schematic diagram of the drive assembly structure according to an embodiment of the present invention, showing the connection relationship between the drive motor and the winding wheel.

[0035] Figure 11 This is a schematic diagram of a guide wheel structure according to an embodiment of the present invention, showing the independent structural form of the guide wheel.

[0036] Figure 12 This is a schematic diagram of the overall layout of the drive module according to an embodiment of the present invention, showing the arrangement of four drive motors, wire winding wheels, guide wheels and controller.

[0037] Explanation of the markings on the components in the attached diagram:

[0038] 1-Base; 2-Linkage base; 3-First link; 4-Second link; 5-Third link; 6-Fourth link; 7-First joint; 8-Second joint; 9-Third joint; 10-Fourth joint; 11-Joint shaft; 12-Polygonal segment; 13-Circular segment; 14-Drive wire through hole; 15-Wire through hole; 16-Self-locking assembly; 17-Self-locking motor; 18-Slider; 19-Self-locking push rod; 20-Rack and pinion structure; 21-Self-locking gear; 22-Drive assembly; 23-Drive motor; 24-Wire winding wheel; 25-Guide wheel; 26-End connection structure. Detailed Implementation

[0039] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings. The embodiments described below are only for explaining the present invention and do not constitute a limitation on the scope of protection of the present invention. Based on their understanding of the technical solution of the present invention, those skilled in the art can combine, modify, or make equivalent substitutions to the embodiments, and all such modifications should fall within the scope of protection of the present invention.

[0040] like Figure 1 As shown, this invention provides a slender, multi-degree-of-freedom flexible robotic arm combining local drive and wire drive, comprising a base 1, a link base 2, a first link 3, a second link 4, a third link 5, and a fourth link 6. A first joint 7 is formed between the link base 2 and the first link 3; a second joint 8 is formed between the first link 3 and the second link 4; a third joint 9 is formed between the second link 4 and the third link 5; and a fourth joint 10 is formed between the third link 5 and the fourth link 6, thus constituting a four-degree-of-freedom serial slender robotic arm structure. An end-effector connection structure 26 is provided at the free end (i.e., the end effector) of the fourth link 6. This end-effector connection structure 26 can adopt a threaded connection hole, a flange connection seat, a pin connection position, or other standardized interface forms for connecting grippers, probes, sensors, detection modules, or other end effectors. It can also be used to continue connecting additional links when additional degrees of freedom are needed, further extending the length and degrees of freedom of the robotic arm. Figure 1 As shown, the base 1 serves as the mounting and support foundation for the entire machine, used to fix the drive assembly 22 and provide installation space for various electrical components. The base 1 can also be fixedly connected to an external work platform (such as a mobile trolley, fixed base, or cantilever mechanism) depending on the actual application scenario. The linkage base 2 is located at the proximal end of the robotic arm (i.e., the end closest to the base 1). Its upper part is fixedly connected to the base 1, and its lower part is rotatably connected to the first linkage 3. The interior of the linkage base 2 can also form a cavity structure to accommodate the self-locking motor 17, cables, and partial connectors, thereby achieving a compact structural layout.

[0041] Figure 2A detailed schematic diagram of the joint structure is shown. Taking the second joint 8 as an example, this joint is composed of a joint axis 11 connecting the first link 3 and the second link 4. (Combined with...) Figure 3 As shown in the structural diagram of the joint shaft 11, the middle part of the joint shaft 11 is set as a polygonal segment 12, and both ends are set as circular segments 13. The polygonal segment 12 is preferably a regular polygonal cross-section, such as a regular hexagon, to facilitate processing and assembly positioning. The upper end of the second connecting rod 4 (the part corresponding to the second joint 8) is provided with a polygonal through hole. The shape and size of the polygonal through hole are adapted to the polygonal segment 12, so that when the joint shaft 11 passes through the polygonal through hole, the second connecting rod 4 and the joint shaft 11 form a circumferential fixed connection, that is, the second connecting rod 4 and the joint shaft 11 cannot rotate relative to each other. The lower end of the first connecting rod 3 (the part corresponding to the second joint 8) is provided with a circular through hole. The shape and size of the circular through hole are adapted to the circular segment 13, so that the first connecting rod 3 can rotate freely around the joint shaft 11. A bearing can also be set between the circular segment 13 and the circular through hole to reduce the frictional resistance during rotation and improve the smoothness of joint rotation and repeatability positioning accuracy. With the above-mentioned composite section design, the present invention can achieve circumferential fixed connection between one side connecting rod and joint shaft 11 and rotational connection of the other side connecting rod around joint shaft 11 without the use of additional fasteners such as keys, pins or screws, which simplifies the joint assembly process and provides a stable installation foundation for the subsequent installation of self-locking gear 21 on joint shaft 11.

[0042] Figure 4 The arrangement of the drive wire through holes at the end of the connecting rod is shown. Taking the first connecting rod 3 as an example, four drive wire through holes 14 are arranged circumferentially on its end sidewall. These four drive wire through holes 14 are preferably evenly distributed at 90° intervals, allowing the drive wire to pass through each connecting rod along the axial direction of the robotic arm. The positions of the drive wire through holes 14 are designed to correspond to the wire through holes 15 on the joint shaft 11, forming a continuous and unobstructed wiring path. In actual assembly, the inner wall of the drive wire through holes 14 can be fitted with wear-resistant bushings or smoothed to reduce frictional loss of the drive wire during movement. The connecting rod interior can be fitted with reinforcing ribs, locally thickened areas, or end flanges as needed to enhance the bending and torsional resistance near the joint. Additionally, grooves, cavities, or partitions can be provided inside the connecting rod to accommodate the self-locking assembly 16 and to arrange the wires.

[0043] like Figure 3 and Figure 4As shown, both ends of the joint shaft 11 (i.e., the end faces of the circular segment 13) are provided with through holes 15 that correspond one-to-one with the positions of the drive wire through holes 14. When the joint shaft 11 is assembled in place, the through holes 15 are aligned with the drive wire through holes 14 on the adjacent connecting rods, so that the drive wire can pass through the drive wire through hole 14 of one connecting rod, immediately enter the through hole 15 of the joint shaft 11, and then pass through the drive wire through hole 14 of the other connecting rod, forming a continuous, closed and clearly directional four-channel drive wire path. Figure 4 The spatial correspondence between the drive wire through-hole 14 and the through-hole 15 is clearly shown, and this correspondence is one of the key technical features of the present invention. By carefully designing the relative positions of the drive wire through-hole 14 and the through-hole 15, the lengths of the two drive wires located in the rotation plane change significantly when the joint rotates around the joint axis 11, while the lengths of the two drive wires located in the direction perpendicular to the rotation plane remain basically unchanged. Specifically, in this embodiment, the four drive wire through-holes 14 are located in the upper, lower, left, and right directions of the connecting rod end face, respectively. When the joint rotates around the horizontal axis (e.g., the X-axis), the lengths of the two drive wires located in the upper and lower directions change, while the lengths of the two drive wires located in the left and right directions remain unchanged. This "two long and two short" variable length rule greatly simplifies the control mapping relationship of the multi-joint wire drive system. The drive controller only needs to focus on the drive wires whose lengths change to achieve precise joint control, while the drive wires whose lengths remain unchanged do not require complex dynamic compensation, thereby reducing the complexity and computational burden of the control system. It also reduces the sliding friction between the drive wires and the hole walls, improving transmission efficiency and repeatability.

[0044] Figures 5 to 9 The structure and working principle of the self-locking assembly 16 are shown in detail. The self-locking assembly 16 includes a self-locking motor 17, a slider 18, a self-locking push rod 19, and a self-locking gear 21. The self-locking motor 17 is installed in the receiving space inside the connecting rod or connecting rod base 2, and its output end is connected to the slider 18, which can drive the slider 18 to perform linear reciprocating motion in a predetermined direction. One end of the self-locking push rod 19 is fixedly connected to the slider 18, and the other end is provided with a rack structure 20. The self-locking gear 21 is fixed on the joint shaft 11. Specifically, the self-locking gear 21 is fitted on the polygonal segment 12 of the joint shaft 11. Since the polygonal segment 12 and the inner hole of the self-locking gear 21 form a circumferential limit, the self-locking gear 21 and the joint shaft 11 rotate synchronously. Figure 6 An enlarged view of the self-locking push rod 19 and its end rack structure 20 is shown. The rack structure 20 has a straight tooth profile, and its module and pressure angle are matched with the self-locking gear 21. Figure 7 The structure of the self-locking gear 21 is shown. The self-locking gear 21 is an external gear, and its tooth profile meshes with the rack structure 20. Figure 8 and Figure 9The relative positions of the self-locking component 16 in the unlocked and locked states are shown respectively. Figure 8 In the unlocked state shown, the self-locking motor 17 (not shown in the figure) drives the slider 18 (not shown in the figure) to move the self-locking push rod 19 backward, causing the rack structure 20 to disengage from the self-locking gear 21. At this time, the joint shaft 11 can rotate freely, and the corresponding joint is in a movable state. Figure 9 In the indicated state, the self-locking motor 17 (not shown in the figure) drives the slider 18 (not shown in the figure) to move the self-locking push rod 19 forward, causing the rack structure 20 and the self-locking gear 21 to engage. Because the linear motion of the rack structure 20 is constrained, the self-locking gear 21 cannot rotate, and consequently, the joint shaft 11 cannot rotate, thus the corresponding joint is stably locked. It is worth emphasizing that the self-locking assembly 16 of this invention is entirely driven independently by the self-locking motor 17 at each joint. The locking and unlocking actions do not rely on any additional trigger wires, selection motors, or independent locking / unlocking execution modules. This is fundamentally different from existing solutions that require additional trigger ligaments and complex selection mechanisms (such as the RTR solution). Each joint's self-locking motor 17 only undertakes the locking and unlocking tasks for that joint and does not participate in the main drive of the joint. Therefore, the self-locking motor 17 can be a small micro-motor, which is easy to integrate into the connecting rod, achieving a compact layout.

[0045] Figures 10 to 12 The specific structure of the drive assembly 22 is shown. The drive assembly 22 includes four drive motors 23, which are centrally mounted on the base 1, forming a centralized drive module. Each drive motor 23 has a winding wheel 24 connected to its output end. One end of the drive wire is fixed to the winding wheel 24, and the other end passes through a guide wheel 25 before entering the connecting rod base 2 and the interior of each stage of the connecting rod. When the drive motor 23 rotates forward, the winding wheel 24 winds the drive wire, shortening its effective working length; when the drive motor 23 rotates in reverse, the winding wheel 24 releases the drive wire, increasing its effective working length. By controlling the combination of winding and unwinding the four drive wires, different joints can be driven to produce the required rotation angle. The guide wheel 25 is used to change the direction of the drive wire, allowing it to smoothly transition from the horizontal direction of the base 1 to the vertical direction of the connecting rod base 2, thus adapting to different installation postures and spatial layouts. The guide wheel 25 may have grooves on its surface to prevent the drive wire from slipping during movement.

[0046] The four drive motors 23 of the drive module are connected to the controller, which controls the forward and reverse rotation, speed, and start / stop of the drive motors 23. Simultaneously, the self-locking motors 17 at each joint are also connected to the controller. The controller coordinates the actions of the self-locking motors 17 and the drive motors 23 according to a preset control sequence. During the drive process, the controller first activates the self-locking motors 17 at non-target joints that share the same set of drive wires as the target joint, locking these non-target joints. Then, the controller controls the drive motors 23 to retract and extend the drive wires, causing the target joint to rotate around its joint axis 11 to the target angle. Once the target joint is in position, the controller then activates the self-locking motors 17 at that target joint, locking the target joint. Through this sequential control of "non-target joint locking—target joint driving—target joint locking," this invention achieves independent driving and attitude maintenance of multiple joints using only four drive wires, fundamentally eliminating the motion coupling problem caused by multiple joints sharing drive wires. Compared with the existing technology that requires six motors and a complex mechanical selection mechanism, the drive system of the present invention is simpler and the control logic is more intuitive. At the same time, since the self-locking state of each joint does not depend on the continuous torque output of the drive motor, the drive motor 23 can stop running or maintain a low power state during the attitude holding phase, thereby reducing the system energy consumption.

[0047] In this embodiment, the four links (first link 3, second link 4, third link 5, and fourth link 6) are connected end to end in sequence, and their joint layout is as follows: Figure 1 As shown: the rotation axes of the first joint 7 and the third joint 9 are parallel to each other, and the rotation axes of the second joint 8 and the fourth joint 10 are parallel to each other. Furthermore, the rotation axes of adjacent joints are sequentially orthogonal (i.e., the rotation axis of the first joint 7 is perpendicular to the rotation axis of the second joint 8, the rotation axis of the second joint 8 is perpendicular to the rotation axis of the third joint 9, and so on). This orthogonal alternating layout enables the robotic arm to achieve multi-degree-of-freedom spatial posture adjustment capabilities, while also providing a structural basis for sharing drive wires. Specifically, the first joint 7 and the third joint 9 have parallel rotation axis directions, and they can share the same set of drive wires (e.g., two drive wires forming a pair) to achieve rotation control; similarly, the second joint 8 and the fourth joint 10 can also share another set of drive wires. During the driving process, when the first joint 7 needs to be driven to rotate, the third joint 9 is first locked, so that all the force of the drive wire is applied to the first joint 7; after the first joint 7 is in position, it is locked again, and then the third joint 9 is unlocked and driven to rotate. With this time-sharing drive strategy, four drive wires can complete the sequential control of four joints, eliminating the need to configure an independent drive wire for each joint, thus greatly reducing the number of wires.

[0048] Regarding the pairing method of the drive wires, the present invention preferably adopts a differential drive method. Of the four drive wires, every two drive wires form a pair, each used to drive the same joint or the same group of parallel rotating shaft joints in opposite directions of rotation. For example, for the first joint 7 and the third joint 9, a first drive wire and a second drive wire can be set to form a first pair. When the first drive wire is tightened and the second drive wire is released, the joint rotates in the forward direction; when the first drive wire is released and the second drive wire is tightened, the joint rotates in the reverse direction. This differential drive method can establish driving torques in opposite directions on corresponding joints, improving the reversibility and control accuracy of joint rotation. Simultaneously, since the tightening and loosening of the two drive wires are controlled synchronously, the load on the drive motor 23 is more balanced, which is beneficial to improving the dynamic response performance of the system.

[0049] In terms of manufacturing and assembly, the base 1, connecting rod base 2, and each level of connecting rod (3-6) can be formed from metal materials (such as aluminum alloy, stainless steel), high-strength engineering plastics (such as PEEK, polycarbonate), or composite materials. The specific material selection depends on the load requirements, working environment, and cost considerations of the robotic arm. The joint shaft 11 and self-locking gear 21 should preferably be made of high-strength materials (such as tool steel, alloy steel) and heat-treated to improve wear resistance and load-bearing capacity. The drive wire can be selected from stainless steel wire, tungsten wire, fiber rope (such as aramid fiber, carbon fiber composite filament), or wrapped flexible cable, depending on the required strength and flexibility. The surface of the drive wire can be coated with a wear-resistant coating to reduce friction. During assembly, the connection between the connecting rod and the joint shaft 11 can be completed first. The joint shaft 11 is inserted into the polygonal through hole and the circular through hole. If necessary, a bearing is installed between the circular segment 13 and the circular through hole. Then, the self-locking assembly 16 is installed, and the self-locking motor 17, the slider 18, and the self-locking push rod 19 are installed in the receiving space inside the connecting rod, ensuring that the self-locking gear 21 and the rack structure 20 can mesh normally. Finally, the drive wires are laid, and the four drive wires are passed through the drive wire through holes 14 on each stage of the connecting rod and the wire through holes 15 on the joint shaft 11 in sequence, and finally fixedly connected to the wire winding wheel 24 on the base 1. The modular assembly method can significantly improve the prototype debugging efficiency and facilitate later maintenance and replacement.

[0050] During control and use, the operator first positions the robotic arm in its initial extended state according to the task requirements, and then controls the movement of each joint sequentially through the controller. Taking the first joint 7 as an example, the controller first sends a locking command to the self-locking motor 17 of the third joint 9, causing the third joint 9 to enter the locked state; then the controller sends a command to the drive motor 23 to drive the corresponding drive wire to retract and extend, causing the first joint 7 to rotate to the target angle; after the first joint 7 is in position, the controller sends a locking command to the self-locking motor 17 of the first joint 7, causing the first joint 7 to maintain the current angle. For the second joint 8, the third joint 9, and the fourth joint 10, the drive can be completed in the same order. When all joints have reached the target pose, the self-locking components 16 of each joint are in the locked state, and the robotic arm can maintain the current configuration without the drive motor 23 continuously outputting holding torque. This has significant advantages for long-term posture maintenance tasks (such as fixed-point detection, online monitoring, static clamping, etc.). If it is necessary to withdraw or reset the robotic arm, the above steps can be reversed to unlock each joint sequentially and drive it back to the initial position.

[0051] As can be seen from the above description, this invention systematically integrates features such as composite cross-section joint shafts, four-channel drive wire paths and corresponding wire holes, a rack-and-pinion self-locking structure with independent motor direct drive, and a centralized four-motor drive at the base, forming a slender, multi-degree-of-freedom flexible spatial robotic arm with a compact structure, fewer wires, decoupled control, and strong posture maintenance capability. The above structural features support and synergize with each other, jointly achieving the technical effects of this invention. The technical solution of this invention is not limited to a four-degree-of-freedom implementation. When N takes other values ​​(such as N=3, N=5, N=6, etc.), it can be extended according to the same design principle, only requiring corresponding adjustments to the number of links, joint shafts, and self-locking modules, while maintaining four drive wires running through all joints in the drive module. Therefore, this invention is not only applicable to the four-degree-of-freedom robotic arm shown in this embodiment, but also to slender, multi-joint robotic arm systems with more degrees of freedom. Those skilled in the art, based on their understanding of the technical solution of this invention, can make adaptive adjustments to the number of joints, drive wire material, self-locking motor type, end-effector interface form, etc., and these adjustments do not depart from the technical concept of this invention and should be considered as falling within the protection scope of this invention.

Claims

1. A local driving and wire driving combined elongated multi-degree-of-freedom spatial flexible robot arm, characterized in that, include: System chassis; Linkage base; The first, second, third, and fourth links form a first joint between the link base and the first link, a second joint between the first and second links, a third joint between the second and third links, and a fourth joint between the third and fourth links, thus constituting a four-degree-of-freedom serial slender robotic arm structure. The rotation axes of the first and third joints are parallel to each other, the rotation axes of the second and fourth joints are parallel to each other, and the rotation axis directions of adjacent joints are orthogonal in sequence. A joint shaft is provided between each adjacent link. The middle part of the joint shaft is a polygonal segment and the two ends are circular segments. A polygonal through hole is provided on one side of the link corresponding to the polygonal segment, and a circular through hole is provided on the other side of the link corresponding to the circular segment. There are four drive wires in total. Every two drive wires form a pair. The first and third joints share the same set of drive wires to achieve rotation control, and the second and fourth joints also share another set of drive wires. During the driving process, when it is necessary to drive the first joint to rotate, the third joint is locked first, so that the force of the drive wire is applied to the first joint; when the first joint is in position, it is locked, and then the third joint is unlocked and driven to rotate. With this time-sharing drive strategy, four drive wires can complete the sequential control of four joints; The self-locking module, corresponding to each joint, includes a self-locking motor installed in the connecting rod or connecting rod base, a slider driven by the self-locking motor, a self-locking push rod connected to the slider, and a self-locking gear fixed on the corresponding joint shaft. The end of the self-locking push rod is provided with a rack structure, and the rack structure selectively engages or disengages with the self-locking gear under the direct drive of the self-locking motor. The drive module, mounted on the system chassis, includes four drive motors, a winding wheel connected to the output end of each drive motor, and a guide wheel. The four drive motors drive four drive wires respectively. The locking and unlocking actions of the self-locking module do not depend on additional trigger wires, selection motors, or independent locking / unlocking execution modules.

2. The elongate multi-degree-of-freedom spatially flexible robotic arm of claim 1, wherein, The polygonal segment is a regular polygonal cross-section, the polygonal through hole is a regular polygonal through hole that matches the regular polygonal cross-section, and a bearing is provided between the circular segment and the circular through hole.

3. The slender, multi-degree-of-freedom flexible robotic arm according to claim 1, characterized in that, Each link has four drive wire through holes spaced circumferentially on its sidewall. Each joint shaft has a wire through hole at both ends that corresponds to the drive wire through holes. The four drive wires pass through the drive wire through holes on each link and the wire through holes on each joint shaft in sequence to form a continuous four-channel drive wire path.

4. The elongate multi-degree-of-freedom spatially flexible robotic arm of claim 1, wherein, The self-locking push rod moves linearly under the drive of the self-locking motor. When the rack structure meshes with the self-locking gear, the corresponding joint is locked; when the rack structure disengages from the self-locking gear, the corresponding joint is unlocked.

5. The elongate multi-degree-of-freedom spatially flexible robotic arm of claim 1, wherein, The connecting rod and the connecting rod base have a receiving space for installing the self-locking motor. The self-locking motor, the slider, and the self-locking push rod are all located in the receiving space.

6. The elongate multi-degree-of-freedom spatially flexible robotic arm of claim 1, wherein, The four drive motors of the drive module are connected to the controller, which controls the forward and reverse rotation and start and stop of the drive motors, and cooperates with the self-locking motors at each joint.

7. The elongate multi-degree-of-freedom spatially flexible robotic arm of claim 1, wherein, The last link is provided with an end connection structure, which is used to connect an end effector or to continue connecting other links in series.

Images