Segmented variable stiffness series elastic robot joint

Abstract

The application discloses a segmented variable stiffness series elastic robot joint, which comprises a joint outer disc, a joint rotating part and a torsional spring; the joint outer disc is provided with a rotating cavity, the cavity wall of the rotating cavity is provided with a limiting groove, and the groove wall of the limiting groove is provided with an elastic force receiving part; the joint rotating part is rotatably arranged in the rotating cavity, the outer wall of the joint rotating part is provided with a limiting part, and the limiting part is arranged in the limiting groove; the torsional spring is sleeved outside the joint rotating part, one end of the torsional spring is connected with the joint outer disc, and the other end of the torsional spring is connected with the joint rotating part; in the process that the torsional spring is subjected to force from small to large, the limiting part has the following states in sequence: being separated from the elastic force receiving part, abutting against the elastic force receiving part and compressing the elastic force receiving part to a state of exhausted deformation; and the above scheme can solve the problem that the robot joint is difficult to consider different working conditions.

Description

Technical Field

[0001] This invention relates to the technical field of robot joints, and particularly to a segmented variable stiffness series elastic robot joint. Background Technology

[0002] In unstructured or high-impact environments such as gravel, steps, ditches, descending stairs, jumping, and falling, quadruped robots not only need to perform motion tracking but also require compliant contact, impact buffering, and transmission protection capabilities. Traditional high-rigidity transmission chains lack the deformation space and energy storage path of the mechanical layer under short-term impacts, making it easier for transient loads to propagate to the reducer and motor.

[0003] To address the aforementioned issues, existing technologies have developed a series elastic drive technology. This technology introduces an elastic element between the drive end and the load end, enabling the joint to undergo physical deformation and store energy. It can be used for impact buffering and torque sensing / control.

[0004] If the stiffness of the series elastic element is high, the response and position tracking during normal motion will be better, but the elastic deformation and energy storage space during impact will be limited. If the stiffness is low, it is beneficial for compliant buffering, but it may increase deformation, tracking deviation during normal motion, and load-bearing risk under large deformation conditions. That is, using a single fixed stiffness to cover both normal motion and high impact conditions presents an engineering trade-off.

[0005] Therefore, how to solve the above-mentioned dilemma has become a key research and development direction for those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide a segmented variable stiffness series elastic robot joint to solve the problem that robot joints are difficult to adapt to different working conditions.

[0007] To address the aforementioned technical problems, this invention provides a segmented variable stiffness serial elastic robot joint, comprising an outer joint disk, a rotating joint component, and a torsion spring. The outer joint disk has a rotating cavity, the cavity wall of which has a limiting groove, and the groove wall of the limiting groove has an elastic force-bearing component. The rotating joint component is rotatably mounted within the rotating cavity, and its outer wall has a limiting component located within the limiting groove. The torsion spring is sleeved around the rotating joint component, with one end connected to the outer joint disk and the other end connected to the rotating joint component. As the force on the torsion spring increases, the limiting component sequentially experiences states of separation from the elastic force-bearing component, contact with the elastic force-bearing component, and compression of the elastic force-bearing component until its deformation is exhausted.

[0008] In one embodiment, the two limiting grooves are arranged opposite to each other on opposite sides of the rotating cavity; the two limiting members are respectively disposed on opposite sides of the joint rotating member, and the two limiting members are respectively disposed in the two limiting grooves.

[0009] In one embodiment, the limiting groove is a sector-shaped groove.

[0010] In one embodiment, the elastic force-bearing component is an elastic block with a Shore hardness of 85-95.

[0011] In one embodiment, the elastic force-bearing component is a polyurethane pad.

[0012] In one embodiment, the limiting member and the joint rotating member are detachably connected, and the limiting member has a variety of different sizes available. The selection of different sizes of the limiting member is used to change the initial separation distance between the limiting member and the elastic force.

[0013] In one embodiment, the limiting member includes an interlocking rod and an abutment; the interlocking rod is plugged into and pulled into the joint rotating member; the abutment is disposed in the limiting groove, and the abutment of the limiting member has different dimensions for different sizes.

[0014] In one embodiment, the outer peripheral wall of the joint rotating member is provided with an insertion hole; a portion of the limiting member is inserted into the insertion hole, and a portion of the limiting member is disposed in the limiting groove.

[0015] In one embodiment, the torsion spring is detachably connected to the outer disk of the joint, and the torsion spring is detachably connected to the rotating component of the joint; the torsion spring has a variety of optional models with different stiffnesses, and the selection of the limiting torsion spring with different stiffnesses is used to change the ease with which the limiting component moves toward the elastic force.

[0016] In one embodiment, the outer disc of the joint is provided with a fixed spring hole; the rotating joint is provided with a fixed spring hole; one end of the torsion spring is inserted into the fixed spring hole on the disc, and the other end of the torsion spring is inserted into the fixed spring hole on the component.

[0017] The beneficial effects of this invention are as follows: 1. This invention utilizes a torsion spring and an elastic force-bearing component to form two series-connected elastic load-bearing paths, achieving segmented stiffness variations from the small deformation zone to the medium deformation zone and then to the ultimate limit in a single joint structure. Under small loads, only the torsion spring operates, ensuring the smoothness and responsiveness of joint movement; under medium loads, the elastic force-bearing component intervenes to provide progressively enhanced support, effectively improving the joint's load-bearing capacity; under ultimate loads, hard limit protection is activated to prevent excessive deformation or overload damage to the torsion spring. The entire segmented response process is automatically triggered by relative mechanical deformation, requiring no external sensors, controllers, or additional actuators. It features fast response speed, high reliability, and the protection function remains effective even in the event of power failure or control malfunction, significantly improving the joint's adaptability and safety performance under complex working conditions.

[0018] 2. By symmetrically arranging limiting grooves and limiting components on opposite sides of the rotating cavity, the joint can achieve the same degree of segmented variable stiffness control in both directions of rotation. This avoids the unidirectional stiffness imbalance problem that may occur with unilateral arrangement, ensuring the mechanical symmetry and motion consistency of the joint under bidirectional loading. Simultaneously, the limiting components on both sides share the load, halving the force on individual limiting components and elastic force-bearing components, which helps reduce local stress concentration and improves the service life and load-bearing limit of parts. The symmetrical structure also makes the overall force on the joint more balanced, reducing the additional bending moment caused by eccentric loading on rotating components and bearings, and improving the smoothness and reliability of joint operation.

[0019] 3. The limiting groove adopts a fan-shaped groove structure, whose arc-shaped extension direction perfectly matches the rotational trajectory of the joint rotating component. This allows the movement of the limiting component within the groove to naturally conform to the rotational direction, eliminating the risk of lateral compression and jamming that may occur with linear guide grooves during arc-shaped movements, and improving the smoothness of joint rotation. The fan-shaped groove provides a uniform limiting stroke along the arc direction, making the transition process from separation to contact of the limiting component smoother and reducing the impact during segmented stiffness switching. At the same time, the fan-shaped structure allows for setting the trigger angle for stiffness switching by adjusting the size of the fan angle, providing flexible parameter adjustment space for the design of stiffness segment points, and the stress distribution on the groove wall is more uniform when under force, resulting in higher structural strength.

[0020] 4. The elastic load-bearing component uses an elastic block with a Shore hardness of 85-95, possessing both sufficient elastic deformation capacity and high load-bearing stiffness. This provides adequate deformation space after the limiting component abuts to absorb impact energy, while ensuring sufficient reaction force is output before the deformation is exhausted, achieving a smooth transition from medium load to ultimate load. Compared to elastic blocks with lower hardness, this hardness range effectively reduces the ineffective angular travel between abutment and hard limiting, resulting in higher positional accuracy and faster response of the joint under heavy loads. Compared to elastic blocks with higher hardness, this hardness range retains necessary buffer deformation, preventing sudden stiffness changes from causing impact damage to the transmission system, achieving a reasonable balance between buffer energy absorption and rigid support.

[0021] 5. Using polyurethane pads as elastic load-bearing components, their excellent wear resistance and tear resistance prevent the joint from wearing or cracking under repeated compression and release cycles of the limiting components, significantly extending the joint's service life and maintenance cycle. Polyurethane material has good resistance to compressive permanent deformation, maintaining its original shape and thickness even after long-term use. This ensures that the trigger position and deformation stroke of the joint remain consistent after multiple operating cycles, improving the long-term stability of joint performance. Furthermore, polyurethane pads can be manufactured through molding, offering high dimensional accuracy and low cost, facilitating mass production and rapid replacement, thus reducing the manufacturing and maintenance costs of the joint.

[0022] 6. The detachable connection between the limiting component and the joint rotating component, along with the availability of multiple limiting component sizes, allows the same joint body to adapt to the stiffness requirements of different robots without altering its structural design. The initial clearance for stiffness switching can be adjusted simply by replacing the limiting component, significantly improving the joint's versatility and adaptability. This solution shifts the adjustment of stiffness segmentation points from the machining stage to the assembly selection stage, avoiding the need to design separate mold limiting slots or modify the overall joint structure for different trigger threshold requirements. This effectively shortens the product development cycle and reduces mold costs. The detachable connection also facilitates the replacement of worn limiting components without replacing the entire joint rotating component, improving maintainability and economy.

[0023] 7. The limiting component adopts an integrated structure where the insert rod and the abutment are interconnected, making replacement extremely simple—disassembly is completed simply by pulling the insert rod out of the joint rotating component, and installation is completed by inserting the new component. No other parts of the joint need to be disassembled, significantly reducing the time required for stiffness characteristic adjustment. Adjusting the initial separation distance by changing the abutment size rather than the insert rod size ensures that the insert rod portion of different limiting component models maintains a uniform specification. The plug-in connection structure on the joint rotating component does not need to be modified with changes in stiffness level, effectively simplifying the manufacturing process. The plug-in connection method avoids the loosening risks that may occur with threaded connections, providing higher connection reliability and anti-loosening capability under repeated impact load conditions. Furthermore, the different sizes of the abutment are visually distinct, facilitating quick on-site identification and selection.

[0024] 8. Insert holes are made on the outer peripheral wall of the joint rotating component to install the limiting component. This allows a portion of the limiting component to be embedded inside the joint rotating component, enhancing the connection stability between the limiting component and the joint rotating component. Compared to surface attachment or bolt fixing, this method is more resistant to loosening and displacement under reciprocating impact loads. The insert hole structure provides clear circumferential positioning for the limiting component, ensuring the consistent position of multiple paired limiting components in the circumferential direction, which is beneficial for the synchronous triggering of stiffness switching between the two limiting components. The insertion hole is located on the outer peripheral wall of the joint rotating component, facilitating machining and dimensional accuracy control. Furthermore, the depth can be flexibly designed to accommodate limiting components with different rod lengths, further expanding the range of selectable limiting component sizes. The insert hole connection also enables radial assembly, providing better operational convenience in robot joint installation environments with limited axial space.

[0025] 9. The detachable connection between the torsion spring, the outer joint disc, and the rotating joint components, combined with various stiffness options, expands the adjustment of the joint's stiffness characteristics from a single trigger position adjustment to the adjustment of the stiffness curve slope. Users can change the joint's compliance in the small deformation range by replacing torsion springs with different stiffnesses. Combined with the selection of limiter sizes, comprehensive calibration of the segmented stiffness curve can be achieved, greatly enhancing the joint's adaptability to different working conditions. The torsion spring, as an independent component, can be disassembled and replaced individually, facilitating fatigue checks and timely replacement during routine maintenance. This avoids the scrapping of the entire joint assembly due to torsion spring fatigue failure, significantly reducing long-term operating costs. Combinations of torsion springs with different stiffnesses and limiters of different sizes can form various stiffness characteristic configurations, allowing the same joint structure to be quickly switched to adapt to a wide range of application scenarios, from light-load, high-sensitivity to heavy-load, high-rigidity, enhancing the joint's versatility and platform development value.

[0026] 10. The insert-type connection structure of the fixed spring holes on the disc and the component provides precise circumferential positioning and a reliable torque transmission interface for both ends of the torsion spring. It is less prone to slippage or loosening under repeated alternating torsional loads, ensuring the consistency of the torsion spring's working posture and the accuracy of force transmission. The fixed spring hole structure facilitates quick installation and removal of the torsion spring. During assembly, simply insert both ends of the torsion spring into their corresponding holes; no additional fasteners or special tools are required, significantly improving assembly efficiency and maintenance convenience. The position and depth of the fixed spring holes can be matched to the end dimensions and stiffness characteristics of different torsion springs, allowing the same joint body to accommodate various specifications of torsion springs, enhancing modularity and component versatility. Under the constraint of the fixed spring holes, the torsion spring will not experience radial movement or axial displacement during operation, avoiding abnormal friction with surrounding parts, which helps reduce operating noise and extend service life. Attached Figure Description

[0027] To more clearly illustrate the technical solution of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of the structure provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the disassembly structure provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the application state provided in the embodiment of the present invention.

[0029] The attached figures are labeled as follows: 100. Joint outer disc; 110. Rotating cavity; 120. Limiting groove; 130. Elastic force-bearing component; 140. Fixed spring hole on the disc; 200. Joint rotating component; 210. Limiting component; 211. Insert rod; 212. Abutment joint; 220. Insertion hole; 230. Fixed spring hole on the component; 300. Torsion spring; 400. Bearings; 500. Mechanical Legs. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0031] When quadruped robots operate under unstructured or high-impact conditions, their joints must balance motion tracking, compliant contact, impact buffering, and transmission protection. Traditional high-stiffness drive chains lack mechanical deformation and energy storage space, making it easy for impact loads to be transmitted to reducers and motors, causing damage. Existing series elastic drive technology achieves buffering and torque control by introducing elastic elements between the drive and the load, but there is a contradiction in stiffness selection: high-stiffness elastic elements are beneficial for position tracking during normal motion but limit deformation and energy storage during impact; low-stiffness elastic elements are beneficial for compliant buffering but increase deformation and tracking deviation during normal motion and may pose a risk of load-bearing under large deformation. Therefore, using a single fixed stiffness cannot simultaneously meet the needs of normal motion and high-impact conditions, becoming a technical problem that urgently needs to be solved in this field.

[0032] To address the above problems, this invention provides a segmented variable stiffness series elastic robot joint, such as... Figure 1 and Figure 2As shown, this embodiment includes an outer joint disc 100, a joint rotating component 200, and a torsion spring 300. The outer joint disc 100 has a rotating cavity 110, and the cavity wall of the rotating cavity 110 has a limiting groove 120. The groove wall of the limiting groove 120 has an elastic force-bearing component 130. The joint rotating component 200 is rotatably installed in the rotating cavity 110. The outer wall of the joint rotating component 200 has a limiting component 210, which is located in the limiting groove 120. The torsion spring 300 is sleeved on the outside of the joint rotating component 200. One end of the torsion spring 300 is connected to the outer joint disc 100, and the other end of the torsion spring 300 is connected to the joint rotating component 200. As the force on the torsion spring 300 increases, the limiting component 210 sequentially experiences the following states: separating from the elastic force-bearing component 130, abutting against the elastic force-bearing component 130, and compressing the elastic force-bearing component 130 until its deformation is exhausted.

[0033] During operation, the joint outer disk 100 and the joint rotating component 200 rotate relative to each other under the action of external force. The torsion spring 300 deforms first under force and provides the initial elastic torque. When the external force is small, the limiting component 210 moves freely within the limiting groove 120, remaining separated from the elastic force-bearing component 130. At this time, only the torsion spring 300 bears the load, and the joint exhibits low stiffness and compliant characteristics. As the external force increases, the rotation angle of the joint rotating component 200 relative to the joint outer disk 100 increases, and the limiting component 210 moves within the limiting groove 120 to a position abutting against the elastic force-bearing component 130. Thereafter, the external force is shared by the torsion spring 300 and the elastic force-bearing component 130, and the equivalent stiffness of the joint increases. When the external force continues to increase to the limit state, the limiting member 210 completely compresses the elastic force-bearing member 130 until the deformation is exhausted, and the limiting member 210 forms a rigid abutment with the wall of the limiting groove 120, thus restricting the relative rotation between the joint rotating member 200 and the joint outer disk 100, achieving hard limiting protection.

[0034] The above-described process enables this joint to achieve segmented variable stiffness characteristics within a single mechanical structure, allowing it to adapt to different load conditions without relying on external sensors or active control. Under light loads, only the torsion spring 300 operates, ensuring smooth joint movement and responsiveness. Under medium loads, the elastic force-bearing component 130 intervenes, providing progressively enhanced support. Under extreme loads, it enters a hard limit position, effectively preventing overload damage to the torsion spring 300. The entire process is completed autonomously by the mechanical structure, resulting in fast response, high reliability, and avoiding the structural complexity and control difficulties associated with adding actuators in traditional variable stiffness solutions.

[0035] like Figure 2 As shown, in order to improve the rotational stability and smoothness of the segmented variable stiffness series elastic robot joint, a bearing 400 can be sleeved on the joint rotating component 200 to improve the rotational smoothness of the joint rotating component 200.

[0036] It should also be noted that the aforementioned segmented variable stiffness series elastic robot joint can be applied to the robot's feet, for example, from... Figure 3 It can be seen that the joint rotating component 200 can be used to connect with motors, reducers, etc. to obtain working power; while the joint outer plate 100 can be used to connect with mechanical leg 500 and other structures to meet the corresponding motion requirements.

[0037] like Figure 2 As shown, in this embodiment, two limiting grooves 120 are arranged opposite to each other on opposite sides of the rotating cavity 110; two limiting members 210 are respectively provided on opposite sides of the joint rotating member 200, and the two limiting members 210 are respectively provided in the two limiting grooves 120.

[0038] The limiting members 210 on both sides of the joint rotating component 200 are located in the limiting grooves 120 on both sides of the rotating cavity 110. When the joint rotating component 200 rotates relative to the joint outer disk 100, the two limiting members 210 move synchronously in their respective limiting grooves 120. Since the limiting grooves 120 on both sides and the elastic force-bearing component 130 are symmetrically arranged, the force conditions of the joint rotating component 200 in both directions of rotation are completely consistent: when rotating at a small angle, the limiting members 210 on both sides do not contact the elastic force-bearing component 130; after continuing to rotate to a set angle, the limiting members 210 on both sides simultaneously abut against their respective elastic force-bearing components 130; when rotating to the limit, the limiting members 210 on both sides simultaneously compress the elastic force-bearing component 130 until the deformation is exhausted. The symmetrical arrangement of the structures on both sides ensures that the stiffness response characteristics of the joint are the same in both directions of rotation, and the joint can obtain a segmented variable stiffness effect in both forward and reverse rotation.

[0039] The symmetrical arrangement on both sides of the joint enables equal segmented variable stiffness control in both directions of rotation, avoiding the unidirectional stiffness imbalance that might occur with a single-sided arrangement. This ensures the mechanical symmetry and motion consistency of the joint under bidirectional loading. Simultaneously, the load-bearing components 210 on both sides share the load, halving the load on each individual component 210 and the elastic force-bearing component 130. This helps reduce local stress concentration, improving the service life and load-bearing limit of the components. The symmetrical structure also makes the overall force distribution of the joint more balanced, reducing the additional bending moment caused by eccentric loading on the joint rotating component 200 and bearings, thus improving the smoothness and reliability of joint operation.

[0040] like Figure 2 As shown, in this embodiment, the limiting groove 120 is set as a sector-shaped groove.

[0041] In this embodiment, the limiting groove 120 is configured as a fan-shaped groove structure, and the limiting member 210 on the joint rotating member 200 is placed within this fan-shaped groove. When the joint rotating member 200 rotates relative to the joint outer disk 100, the limiting member 210 moves along the arc-shaped trajectory of the fan-shaped groove. The arc-shaped extension direction of the fan-shaped groove matches the rotational motion trajectory of the joint rotating member 200, ensuring that the movement of the limiting member 210 within the groove is always smooth and without jamming. As the relative rotation angle increases, the limiting member 210 slides arc-shaped within the fan-shaped groove from one end to the other, successively passing through the stages of separation from the elastic force-bearing member 130, contact, and exhaustion of compression deformation. Throughout the entire movement, the movement path of the limiting member 210 remains concentric with the circular motion of the joint rotating member 200, avoiding motion interference or additional friction that might be caused by a straight groove.

[0042] The arc-shaped structure of the fan-shaped groove perfectly matches the rotational motion of the joint rotating component 200, allowing the movement trajectory of the limiting component 210 within the groove to naturally conform to the rotation direction. This eliminates the risk of lateral compression and jamming that may occur with linear guide grooves during arc motion, improving the smoothness of joint rotation. Simultaneously, the fan-shaped groove provides a uniform limiting stroke along the arc direction, making the transition of the limiting component 210 from separation to engagement smoother and reducing the impact during segmented stiffness switching. The fan-shaped groove structure also facilitates setting the trigger angle for stiffness switching by adjusting the size of the fan-shaped angle, providing flexible parameter adjustment space for the design of the joint's stiffness segmentation points. Furthermore, the stress distribution on the groove wall is more uniform under load, resulting in higher structural strength.

[0043] Preferably, in this embodiment, the elastic force-bearing component 130 is an elastic block with a Shore hardness of 85-95.

[0044] In this embodiment, the elastic force-bearing member 130 disposed on the wall of the limiting groove 120 is an elastic block with a Shore hardness of 85-95. When the limiting member 210 moves with the joint rotating member 200 to abut against the elastic block, the elastic block exhibits a clear resistance to deformation within this hardness range. As the external force continues to increase, the limiting member 210 gradually compresses the elastic block. The deformation of the elastic block at this hardness has a relatively steep increasing relationship with the applied pressure, so that the elastic block can provide a gradual and relatively rigid supporting force as it is compressed to the point of exhaustion. Throughout the entire working process, the elastic block within this hardness range ensures that the limiting member 210 does not produce excessive additional displacement after abutment, thereby maintaining precise control of the joint angle when the second bearing path intervenes.

[0045] The aforementioned Shore hardness of 85-95 elastic blocks combines sufficient elastic deformation capacity with high load-bearing stiffness. This hardness range allows the elastic block to provide adequate deformation space after the limiting member 210 abuts, absorbing impact energy, while ensuring that the elastic block can output a sufficiently large reaction force before compressing to exhaust its deformation, achieving a smooth transition from medium load to ultimate load. Compared to elastic blocks with lower hardness, the Shore hardness of 85-95 effectively reduces the ineffective angular travel between abutment and hard limiting, resulting in higher positional accuracy and faster response of the joint under heavy loads. Compared to elastic blocks with higher hardness, this hardness range also retains necessary buffer deformation, avoiding impact damage to the transmission system caused by sudden stiffness changes, achieving a reasonable balance between buffer energy absorption and rigid support.

[0046] Preferably, in this embodiment, the elastic force-bearing component 130 is a polyurethane pad.

[0047] In this embodiment, the elastic force-bearing component 130 provided on the wall of the limiting groove 120 is specifically a polyurethane pad. When the limiting component 210 moves within the limiting groove 120 with the joint rotating component 200 until it contacts the polyurethane pad, the polyurethane pad begins to bear the compression effect from the limiting component 210. As the joint load gradually increases, the limiting component 210 continuously compresses the polyurethane pad. During the compression process, the polyurethane pad absorbs energy and generates a reaction force by relying on the elastic deformation of its own molecular chain structure. When the load reaches its limit, the polyurethane pad is compressed until the deformation is completely exhausted. At this time, the limiting component 210 forms a rigid contact with the wall of the limiting groove 120, realizing rotational limiting. Throughout the entire process, the polyurethane pad, as the only elastic force-bearing element, participates in the second load-bearing stage, and its degree of compression deformation directly corresponds to the current load range of the joint.

[0048] Polyurethane pads exhibit excellent wear resistance and tear resistance, resisting wear and cracking under repeated compression and release cycles from the limiting component 210, significantly extending the joint's service life and maintenance intervals. Simultaneously, polyurethane material possesses good resistance to compressive permanent deformation, maintaining its original shape and thickness even after long-term use. This ensures consistent trigger positions and deformation strokes for stiffness switching after multiple operating cycles, enhancing the long-term stability of joint performance. Furthermore, polyurethane pads can be manufactured using molds, offering high dimensional accuracy and low cost, facilitating mass production and rapid replacement, thus reducing joint manufacturing and maintenance costs.

[0049] Preferably, in this embodiment, the limiting member 210 and the joint rotating member 200 are detachably connected. The limiting member 210 has a variety of different sizes available. The selection of different sizes of the limiting member 210 is used to change the initial separation distance between the limiting member 210 and the elastic force.

[0050] In this embodiment, the limiting member 210 is detachably mounted on the joint rotating member 200, and the limiting member 210 has various selectable sizes. When different sizes of the limiting member 210 are selected, the length of the portion of the limiting member 210 extending into the limiting groove 120 changes accordingly, thereby adjusting the initial separation distance between the end of the limiting member 210 and the elastic force-bearing member 130. During operation, the joint rotating member 200 rotates relative to the joint outer disk 100, and the limiting member 210 moves with the joint rotating member 200 within the limiting groove 120. With a larger initial separation distance, the limiting member 210 needs to undergo a longer idle stroke before contacting the elastic force-bearing member 130, and the triggering time of the segmented stiffness is later; with a smaller initial separation distance, the limiting member 210 can contact the elastic force-bearing member 130 earlier, and the triggering time of the segmented stiffness is earlier. By replacing the limiters 210 of different sizes, the stiffness switching point of the joint can be preset during the assembly stage to meet the requirements of different working conditions for the timing of variable stiffness triggering.

[0051] The detachable connection and multiple size options of the limiting component 210 allow the same joint body to adapt to the stiffness requirements of different robots without changing the structural design. The initial clearance for stiffness switching can be adjusted simply by replacing the limiting component 210, significantly improving the joint's versatility and adaptability. This solution shifts the adjustment of stiffness segmentation points from the machining stage to the assembly selection stage, avoiding the cumbersome process of designing separate mold-opening limiting grooves 120 or changing the overall joint structure for different trigger threshold requirements. This effectively shortens the product development cycle and reduces mold costs. Furthermore, the detachable connection allows for the replacement of the limiting component 210 after wear without replacing the entire joint rotating component 200, improving the joint's maintainability and economy. Users can also flexibly replace the limiting component 210 with different sizes based on actual usage feedback to optimize joint performance.

[0052] like Figure 2 As shown, in this embodiment, the limiting member 210 includes an insert rod 211 and an abutment 212 that are connected to each other; the insert rod 211 is plugged into and pulled out of the joint rotating member 200; the abutment 212 is disposed in the limiting groove 120, and the abutment 212 of the limiting member 210 of different sizes has different sizes.

[0053] In this embodiment, the limiting member 210 consists of an insert rod 211 and an abutment 212 connected to each other. The insert rod 211 is inserted into the joint rotating member 200 for fixation, and the abutment 212 is located within the limiting groove 120. When different sizes of limiting members 210 are selected, the initial separation distance between the abutment 212 and the elastic force-bearing member 130 is mainly adjusted by changing the space occupied by the abutment 212 within the limiting groove 120. When the joint is working, the insert rod 211 transmits the rotational motion of the joint rotating member 200 to the abutment 212, and the abutment 212 moves along the limiting groove 120. The larger the size of the abutment 212, the larger its initial space occupied within the limiting groove 120, the smaller the initial separation distance between it and the elastic force-bearing member 130, and the earlier the stiffness switching is triggered; conversely, the smaller the size of the abutment 212, the larger the initial separation distance, and the later the triggering. Under extreme conditions, after the abutment 212 compresses the elastic force-bearing member 130 until the deformation is exhausted, the abutment 212 itself abuts against the wall of the limiting groove 120 and undertakes the hard limiting function.

[0054] The integrated design of the insert rod 211 and the abutment joint 212 makes the replacement of the limiting component 210 extremely simple—the old component can be removed simply by pulling the insert rod 211 out of the joint rotating component 200, and the new component can be inserted to complete the installation. No other parts of the joint need to be disassembled, significantly reducing the time required for stiffness characteristic adjustment. Furthermore, by changing the size of the abutment joint 212 instead of the insert rod 211, the initial separation distance can be adjusted, meaning that the insert rod 211 portion of different models of limiting components 210 can maintain a uniform specification. The plug-in connection structure on the joint rotating component 200 does not need to be modified with changes in stiffness level, effectively simplifying the manufacturing process of the joint rotating component 200. The plug-in connection method avoids the loosening risks that may arise from threaded connections, providing higher connection reliability and anti-loosening capability under repeated impact load conditions. In addition, the differentiated design of the abutment joint 212 size makes the different levels of limiting components 210 visually clear, facilitating quick on-site identification and selection, and reducing the risk of incorrect installation.

[0055] like Figure 2 As shown, in this embodiment, the outer peripheral wall of the joint rotating member 200 is provided with an insertion hole 220; a part of the limiting member 210 is inserted into the insertion hole 220, and a part of the limiting member 210 is provided in the limiting groove 120.

[0056] In this embodiment, a socket 220 is provided on the outer peripheral wall of the joint rotating member 200. A portion of the limiting member 210 is inserted into the socket 220 for fixed installation, while the other portion of the limiting member 210 extends out of the socket 220 and is located within the limiting groove 120. When the joint rotating member 200 rotates relative to the joint outer disk 100, the socket 220 rotates together with the joint rotating member 200, causing the portion of the limiting member 210 inserted therein to move synchronously, thereby allowing the portion of the limiting member 210 located within the limiting groove 120 to move along the limiting groove 120. The socket 220 provides a precise positioning reference and a reliable connection interface for the limiting member 210, ensuring that the angle and position of the limiting member 210 relative to the joint rotating member 200 remain constant during operation. When the limiting member 210 moves to contact and compress the elastic force-bearing member 130, the wall of the insertion hole 220 forms a stable support for the insertion part of the limiting member 210, so that the limiting member 210 can effectively transmit the driving force of the joint rotating member 200 to the elastic force-bearing member 130.

[0057] A socket 220 is formed on the outer peripheral wall of the joint rotating component 200 to install the limiting component 210, so that a part of the limiting component 210 is embedded inside the joint rotating component 200. This enhances the connection stability between the limiting component 210 and the joint rotating component 200, and is more resistant to loosening and displacement under reciprocating impact loads compared to surface attachment or bolt fixing. The socket 220 structure provides a clear circumferential positioning for the limiting component 210, ensuring the consistency of the position of multiple paired limiting components 210 in the circumferential direction, which is conducive to the synchronous triggering of stiffness switching of the limiting components 210 on both sides. At the same time, the socket 220 is located on the outer peripheral wall of the joint rotating component 200, which facilitates processing and dimensional accuracy control. Moreover, the depth of the socket 220 can be flexibly designed as needed to accommodate limiting components 210 with different insertion rod 211 lengths, further expanding the range of selectable sizes for the limiting component 210. In addition, the 220-type connection method enables radial assembly of the limiting member 210 and the joint rotating member 200, eliminating the need for axial pulling during assembly and disassembly, thus providing better operational convenience in robot joint installation environments with limited axial space.

[0058] Preferably, in this embodiment, the torsion spring 300 is detachably connected to the outer disk 100 of the joint, and the torsion spring 300 is detachably connected to the rotating joint 200. The torsion spring 300 has a variety of optional models with different stiffnesses. The selection of torsion springs 300 with different stiffnesses is used to change the ease with which the limiting member 210 moves towards the elastic force.

[0059] In this embodiment, the two ends of the torsion spring 300 are detachably connected to the outer joint disk 100 and the joint rotating component 200, respectively, and the torsion spring 300 is available in various models with different stiffnesses. When different stiffness models of the torsion spring 300 are selected, the resistance of the torsion spring 300 that needs to be overcome to achieve relative rotation between the joint rotating component 200 and the outer joint disk 100 changes accordingly. The torsion spring 300 with lower stiffness is more likely to deform under force, making it easier and faster for the limiting component 210 to move towards the elastic force-bearing component 130 under the same external force; the torsion spring 300 with higher stiffness provides stronger initial resistance, making it necessary for the limiting component 210 to be driven by a greater external force to move towards the elastic force-bearing component 130. When the joint is working, the torsion spring 300 first bears the load and deforms. Its stiffness directly determines the ease with which the limiting component 210 moves from the initial separation position to abut against the elastic force-bearing component 130, thereby affecting the response sensitivity and trigger load threshold of the segmented stiffness switching.

[0060] The detachable connection and multiple stiffness selection options of the torsion spring 300 expand the adjustment dimension of the joint's stiffness characteristics from a single trigger position adjustment to the adjustment of the stiffness curve slope. Users can change the compliance of the joint in the small deformation region by replacing the torsion spring 300 with different stiffnesses. Simultaneously, by selecting the size of the limiting component 210, comprehensive adjustment of the segmented stiffness curve can be achieved, greatly enhancing the joint's adaptability to different working conditions. In this solution, the torsion spring 300, as an independent component, can be disassembled and replaced separately, facilitating the inspection of its fatigue state during routine maintenance and timely replacement. This avoids the scrapping of the entire joint assembly due to fatigue failure of the torsion spring 300, significantly reducing long-term operating costs. Furthermore, the combination of torsion springs 300 with different sizes of limiting components 210 can form multiple stiffness characteristic configurations, allowing the same joint structure to be quickly switched to adapt to a wide range of application scenarios, from light loads with high sensitivity to heavy loads with high rigidity, further enhancing the joint's versatility and platform development value.

[0061] like Figure 2 As shown, in this embodiment, the outer disc 100 of the joint is provided with a fixed spring hole 140; the rotating part 200 of the joint is provided with a fixed spring hole 230; one end of the torsion spring 300 is inserted into the fixed spring hole 140 of the disc, and the other end of the torsion spring 300 is inserted into the fixed spring hole 230 of the part.

[0062] In this embodiment, a fixed spring hole 140 is provided on the outer joint disk 100, and a fixed spring hole 230 is provided on the rotating joint component 200. Both ends of the torsion spring 300 are respectively inserted into these two fixed spring holes. During operation, the rotating joint component 200 rotates relative to the outer joint disk 100. One end of the torsion spring 300 is fixed to the outer joint disk 100 through the fixed spring hole 140 and remains stationary, while the other end rotates synchronously with the rotating joint component 200 through the fixed spring hole 230. Thus, the torsion spring 300 undergoes elastic deformation under the relative torsional action between its two ends. As the joint load increases, the torsion angle of the torsion spring 300 gradually increases, and the resulting reaction force acts on the rotating joint component 200 through the fixed spring hole 230 and on the outer joint disk 100 through the fixed spring hole 140, achieving torque transmission and balance. Throughout the entire operation, the two fixed spring holes always circumferentially limit the two ends of the torsion spring 300, ensuring that the deformation of the torsion spring 300 always revolves around its own axis, and the torque transmission path is clear and stable.

[0063] The insert-type connection structure of the fixed spring hole 140 on the disc and the fixed spring hole 230 on the component provides precise circumferential positioning and a reliable torque transmission interface for both ends of the torsion spring 300. Compared with clamping or bonding methods, the insert structure is less prone to slippage or loosening when subjected to repeated alternating torsional loads, ensuring the consistency of the torsion spring 300's working posture and the accuracy of force transmission. The fixed spring hole structure also facilitates the quick installation and disassembly of the torsion spring 300. During assembly, simply insert both ends of the torsion spring 300 into the corresponding holes to complete the installation, without the need for additional fasteners or special tools, greatly improving assembly efficiency and maintenance convenience. At the same time, the position and depth of the fixed spring holes can be matched and designed according to the end dimensions and stiffness characteristics of different torsion springs 300, allowing the same joint body to accommodate multiple specifications of torsion springs 300, further enhancing the modularity of the joint and the versatility of its components. In addition, under the constraint of the fixed spring hole, the torsion spring 300 will not undergo radial movement or axial displacement during operation, which avoids abnormal friction between the torsion spring 300 and surrounding parts, and helps to reduce joint running noise and extend the service life of the torsion spring 300.

[0064] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A segmented variable stiffness serial elastic robot joint, characterized in that, Includes the outer joint disc, joint rotating parts, and torsion spring; The outer disc of the joint is provided with a rotating cavity, the cavity wall of the rotating cavity is provided with a limiting groove, and the groove wall of the limiting groove is provided with an elastic force-bearing member; The joint rotating component is rotatably mounted in the rotating cavity, and the outer wall of the joint rotating component is provided with a limiting component, which is disposed in the limiting groove. The torsion spring is sleeved on the outside of the joint rotating component, one end of the torsion spring is connected to the outer disk of the joint, and the other end of the torsion spring is connected to the joint rotating component. As the force on the torsion spring increases, the limiting member sequentially separates from the elastic force-bearing member, abuts against the elastic force-bearing member, and compresses the elastic force-bearing member until its deformation is exhausted.

2. The segmented variable stiffness serial elastic robot joint according to claim 1, characterized in that, The two limiting grooves are arranged opposite each other on opposite sides of the rotating cavity; The two limiting members are respectively disposed on opposite sides of the joint rotating member, and the two limiting members are respectively disposed in the two limiting grooves.

3. The segmented variable stiffness serial elastic robot joint according to any one of claims 1 or 2, characterized in that, The limiting groove is a sector-shaped groove.

4. The segmented variable stiffness serial elastic robot joint according to claim 1, characterized in that, The elastic force-bearing component is an elastic block with a Shore hardness of 85-95.

5. The segmented variable stiffness serial elastic robot joint according to any one of claims 1 or 4, characterized in that, The elastic force-bearing component is a polyurethane pad.

6. The segmented variable stiffness serial elastic robot joint according to claim 1, characterized in that, The limiting member and the joint rotating member are detachably connected. The limiting member has a variety of different sizes available. The selection of different sizes of the limiting member is used to change the initial separation distance between the limiting member and the elastic force.

7. The segmented variable stiffness serial elastic robot joint according to claim 6, characterized in that, The limiting component includes an interlocking rod and an abutment; The insertion rod is plugged into and pulled into the joint rotating component; The abutment is located within the limiting groove, and the abutment size varies for different sizes of the limiting member.

8. The segmented variable stiffness serial elastic robot joint according to any one of claims 1, 6, or 7, characterized in that, The outer peripheral wall of the joint rotating component is provided with an insertion hole; A portion of the limiting member is inserted into the insertion hole, and a portion of the limiting member is disposed within the limiting groove.

9. The segmented variable stiffness serial elastic robot joint according to claim 1, characterized in that, The torsion spring is detachably connected to the outer disk of the joint, and the torsion spring is detachably connected to the rotating part of the joint. The torsion spring is available in various models with different stiffnesses. The selection of torsion springs with different stiffnesses is used to change the ease with which the limiting member moves toward the elastic force.

10. The segmented variable stiffness serial elastic robot joint according to any one of claims 1 or 9, characterized in that, The outer disc of the joint is provided with a disc-mounted spring hole; The joint rotating component is provided with a fixed spring hole; One end of the torsion spring is inserted into the fixed spring hole on the disc, and the other end of the torsion spring is inserted into the fixed spring hole on the component.

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