Rigid-flexible coupling ankle exoskeleton based on multi-material fused deposition modeling and method

Abstract

The application discloses a rigid-flexible coupling ankle exoskeleton and method based on multi-material fused deposition modeling, which comprises a multi-material lining assembly, a carbon fiber load-bearing framework and an ankle joint hinge assembly, the multi-material lining assembly is detachably connected with the carbon fiber load-bearing framework, and the ankle joint hinge assembly is arranged at the lower end of the carbon fiber load-bearing framework; the multi-material lining assembly comprises a flexible region and a rigid region, the flexible region is arranged on both sides of the rigid region, the material of the flexible region is a flexible material, the material of the rigid region is a rigid short-cut fiber composite material, and a three-dimensional gradient lattice interlocking rigid-flexible material transition region is connected between the flexible region and the rigid region. The application can provide a better wearing experience, realize integrated design of rigid support, flexible buffering and drive installation, effectively buffer local stress concentration, significantly reduce stress concentration, and significantly improve structural reliability and durability.

Description

Technical Field

[0001] This invention specifically relates to a rigid-flexible coupled ankle exoskeleton and method based on multi-material fused deposition modeling. Background Technology

[0002] Exoskeletons are wearable electromechanical systems that enhance human mobility or assist in the recovery of function in restricted limbs through the coordinated movement of their mechanical structures and the human body. Existing ankle exoskeleton systems primarily use high-strength materials such as metal or carbon fiber for their rigid support components, manufactured through cutting or composite processes. While these structures possess high strength and stability, they lack flexibility, making it difficult to precisely conform to the complex curves of the human body, resulting in poor wearing comfort. To improve fit, traditional solutions typically involve attaching flexible connectors such as sewn fabric and straps to the outside of the rigid frame. This method suffers from complex processes, limited assembly precision, and low fabric plasticity and structural design freedom, making it difficult to achieve precise fit for different individuals. Furthermore, stress concentration can easily occur at the sewn and fixation points, leading to localized damage or fatigue cracking, affecting the reliability and durability of the exoskeleton system.

[0003] In recent years, the development of fused deposition modeling (FDM) technology has provided a new approach to the integrated design of complex functional structures. This technology can synergistically deposit rigid and flexible materials in the same manufacturing process, enabling structures to simultaneously possess load-bearing and cushioning functions, thus achieving a balance between lightweight and flexibility. However, existing research mainly focuses on the material interface properties, forming parameter optimization, or basic structural characteristic analysis of multi-material printed parts, lacking a systematic exploration of the overall design methods and manufacturing paths for rigid-flexible coupling mechanisms in exoskeleton systems. Especially in ankle-joint rope-driven exoskeleton structures, there is still a lack of effective solutions for achieving structural integration using multi-material synergistic forming.

[0004] Therefore, there is an urgent need for a rigid-flexible coupled rope-driven ankle exoskeleton structure based on multi-material fused deposition modeling. By achieving a rigid-flexible integrated layout in the design stage and completing the overall shaping in the manufacturing stage, the structural integration and wearing comfort can be improved, thereby overcoming the problems of complex processing, insufficient flexibility and limited assembly precision in the existing technology.

[0005] Existing ankle exoskeleton systems still have the following shortcomings in structural design and manufacturing: (1) Insufficient structural flexibility. The rigid support parts of existing exoskeletons are mostly made of metal or carbon fiber materials. Although they have high strength and rigidity, their flexibility is limited and they are difficult to conform to the complex curved shape of the human body. Wearers are easily restricted during ankle flexion, extension or rotation, which affects the naturalness of movement and wearing comfort.

[0006] (2) Complex assembly and low integration. Traditional exoskeletons are usually connected to the human body by sewing fabric or straps, which is complicated in manufacturing process and limited in assembly precision. The fabric material has low plasticity and design freedom, making it difficult to form a stable three-dimensional fit structure; at the same time, stress concentration is prone to occur at the connection points, resulting in a decrease in system durability. The assembly between the exoskeleton body and the fabric layer depends on manual operation, resulting in low overall structural integration and difficulty in ensuring performance consistency.

[0007] (3) Insufficient personalized fit. Existing processing methods make it difficult to achieve complex curved surfaces and individualized fit design while ensuring mechanical strength, resulting in poor adaptability between different users and affecting the comfort and support effect of long-term wear.

[0008] (4) Lack of rigid-flexible transition interface design. In existing exoskeleton systems, the rigid frame and flexible padding are mostly directly connected, lacking a reasonable transition structure design. Such interfaces are prone to local stress concentration, which leads to limited deformation of the flexible layer, reduced structural stability, and increases the risk of component damage or detachment during long-term use.

[0009] To address the aforementioned issues, this invention proposes a rigid-flexible coupled rope-driven ankle exoskeleton structure based on multi-material fused deposition modeling. This invention achieves integrated structural molding by synergistically depositing rigid and flexible materials in the same printing process. By designing a multi-material layered composite lining structure, a smooth flexible-rigid transition zone is formed, thus balancing structural strength, flexibility, and ergonomic fit. This solution not only achieves lightweight and highly integrated design but also significantly improves the wearing comfort and long-term reliability of the exoskeleton system, demonstrating promising application prospects and widespread value. Summary of the Invention

[0010] The purpose of this invention is to provide a rigid-flexible coupling ankle exoskeleton and method based on multi-material fused deposition modeling, which reduces the difficulty of assembly process, significantly improves assembly convenience and maintainability, provides a better wearing experience, realizes the integrated design of rigid support, flexible cushioning and drive installation, and has a high degree of overall lightweight and structural integration; effectively buffers local stress concentration, significantly reduces stress concentration, and significantly improves structural reliability and durability.

[0011] The technical solution adopted in this invention is: A rigid-flexible coupling ankle exoskeleton based on multi-material fused deposition modeling includes a multi-material liner assembly, a carbon fiber load-bearing frame, and an ankle joint hinge assembly. The multi-material liner assembly is detachably connected to the carbon fiber load-bearing frame. The ankle joint hinge assembly is located at the lower end of the carbon fiber load-bearing frame and is used to connect with footwear. A rope drive mechanism is provided on the carbon fiber load-bearing frame and is connected to the ankle joint hinge assembly. The rope drive mechanism is used to drive the ankle joint hinge assembly to move. The multi-material liner assembly is manufactured by multi-material fused deposition modeling, including flexible regions and rigid regions. The flexible regions are arranged on both sides of the rigid regions. The flexible regions are made of flexible materials, while the rigid regions are made of rigid chopped fiber composite materials. A three-dimensional gradient lattice interlocking rigid-flexible material transition zone connects the flexible regions and the rigid regions.

[0012] Preferably, the three-dimensional gradient lattice interlocking rigid-flexible material transition zone is manufactured by multi-nozzle fused deposition modeling technology. First, a three-dimensional lattice skeleton is printed with a rigid short-cut fiber composite material, and then a flexible material is used to fill and cover the internal cavity of the three-dimensional lattice skeleton to form a volumetric interlocking interface. The rigid chopped fiber composite material in the transition zone has multiple holes distributed on it, and the flexible material in the transition zone has multiple protrusions that fill and embed in the corresponding holes of the rigid chopped fiber composite material; and / or the flexible material in the transition zone has multiple holes distributed on it, and the rigid chopped fiber composite material in the transition zone has multiple protrusions that fill and embed in the corresponding holes of the flexible material. Along the transition zone from the rigid region to the flexible region, the proportion of rigid chopped fiber composite material in the transition zone gradually decreases, while the porosity of the rigid chopped fiber composite material gradually increases or the porosity of the flexible material gradually decreases.

[0013] Preferably, the ankle joint hinge assembly is hinged to the lower end of the carbon fiber load-bearing frame, and the ankle joint hinge assembly integrates an angle encoder.

[0014] Preferably, the carbon fiber load-bearing frame includes two parallel load-bearing plates, with a transverse connecting plate between the two load-bearing plates, and the two ends of the multi-material liner assembly are respectively connected to the two load-bearing plates. There are two multi-material lining components, which are arranged opposite each other on the two load-bearing plates of the carbon fiber load-bearing frame. The two multi-material lining components cover the limb from both sides, and the two ends of the two multi-material lining components are connected by a detachable connection.

[0015] Preferably, the rope drive mechanism includes a drive unit and a transmission rope. The drive unit is fixed on the carbon fiber load-bearing frame. The ankle joint hinge assembly is provided with a transmission rope connector. One end of the drive unit is connected to the transmission rope, and the other end of the transmission rope is connected to the transmission rope connector. The drive unit drives the ankle joint hinge assembly and the shoe to rotate around the hinge point through the transmission rope.

[0016] Preferably, the ankle hinge assembly includes a foot frame and an ankle hinge. The front end of the foot frame is hinged to the shoe, and an elastic rope connects the rear end of the foot frame to the shoe. The foot frame is hinged to the lower end of the carbon fiber load-bearing frame via the ankle hinge, and the transmission rope connector is located at the rear end of the foot frame.

[0017] Preferably, the foot frame includes two parallel footboards, with a transverse ankle connecting plate connected between the two footboards. The transverse ankle connecting plate is located above the rear side of the shoe, and the transmission rope connector is located on the transverse ankle connecting plate. The drive unit includes a motor and a winding wheel. The winding wheel is located on the output shaft of the motor, and the transmission rope is wound around the winding wheel.

[0018] Preferably, the rigid chopped fiber composite material is PLA-CF or PLA-GF, and the flexible material is TPU; The material of the carbon fiber load-bearing frame is replaced with glass fiber reinforced plastic or aluminum alloy; The rope drive mechanism can be replaced with a pneumatic artificial muscle or a screw sliding drive structure.

[0019] A method for manufacturing a rigid-flexible coupled ankle exoskeleton based on multi-material fused deposition modeling as described above includes the following steps: S1: Design a 3D model of a multi-material lining component based on human body 3D scanning data; S2: Using a multi-nozzle fused deposition modeling (FDM) device, rigid chopped fiber composite materials and flexible materials are deposited in tandem according to the designed three-dimensional model. First, the three-dimensional lattice skeleton of the rigid chopped fiber composite material is printed, and then the flexible material is filled to form a buffer system, thus producing a multi-material liner component. S3: Machining a carbon fiber load-bearing frame and integrating the angle encoder into the ankle joint hinge assembly; S4: Connect and assemble the multi-material inner lining components and carbon fiber load-bearing frame to form a complete exoskeleton system.

[0020] The beneficial effects of this invention are: In this invention, the carbon fiber load-bearing skeleton is worn on the human body through a multi-material lining component. The multi-material lining component and the carbon fiber load-bearing skeleton achieve a detachable rigid-flexible combination, reducing the difficulty of assembly procedures and significantly improving assembly convenience and maintainability. This invention provides a better wearing experience by having the flexible area of ​​the multi-material lining component fit the human body, while the rigid area of ​​the multi-material lining component forms a detachable connection with the carbon fiber load-bearing skeleton. Furthermore, the three-dimensional gradient lattice interlocking rigid-flexible material transition zone effectively eliminates the interface peeling and cracking problems that are prone to occur in traditional rigid-flexible layered structures. The rigid-flexible interlocking coupling is significant, and the structural coordination is significantly improved. The multi-material lining component and carbon fiber plate significantly reduce the overall weight of the exoskeleton, achieving an integrated design of rigid support, flexible buffering, and drive installation, resulting in a high degree of overall lightweighting and structural integration. The rigid area is located between the flexible area and the carbon fiber load-bearing skeleton, forming a transition, effectively buffering local stress concentration, significantly reducing stress concentration, and significantly improving structural reliability and durability. Attached Figure Description

[0021] Figure 1 This is a frontal schematic diagram of a rigid-flexible coupled ankle exoskeleton based on multi-material fused deposition modeling in an embodiment of the present invention.

[0022] Figure 2 This is a posterior view of a rigid-flexible coupled ankle exoskeleton based on multi-material fused deposition modeling in an embodiment of the present invention.

[0023] Figure 3 yes Figure 2 A partial K-view.

[0024] Figure 4 This is a schematic diagram of the structure of the multi-material liner assembly in an embodiment of the present invention.

[0025] Figure 5 This is a schematic diagram of the pre-embedding process of the Velcro in an embodiment of the present invention.

[0026] Figure 6 This is a schematic diagram of the structure of the three-dimensional gradient lattice interlocked rigid-flexible material transition region in the multi-material liner assembly of this invention.

[0027] Figure 7 yes Figure 6 A partial K-view.

[0028] In the diagram: 1-Multi-material inner lining assembly; 2-Carbon fiber load-bearing skeleton; 3-Bowden tube; 4-Drive rope; 5-Drive rope connector; 6-Drive rope seat; 7-Elastic rope; 8-Footwear; 9-Hook and loop fastener; 10-Ankle hinge; 11-Surface for contact with carbon fiber load-bearing skeleton; 12-Surface for contact with human body; 13-Flexible material; 14-Rigid chopped fiber composite material. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0030] In the description of this invention, it should be understood that if terms such as "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise" are used to indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, they are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0031] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection. They can refer to a mechanical connection or an electrical connection. They can refer to a direct connection or an indirect connection through an intermediate medium, and they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0032] Example 1 A rigid-flexible coupled ankle exoskeleton based on multi-material fused deposition modeling, such as Figures 1-7 As shown, it includes a multi-material inner lining component 1, a carbon fiber load-bearing frame 2, and an ankle joint hinge component. The multi-material inner lining component 1 and the carbon fiber load-bearing frame 2 are detachably connected (this detachable connection can be a bolt or screw connection). The multi-material inner lining component 1 is used to cover human joints or limbs and fits the human body when worn, serving as the core fitting structure. The carbon fiber load-bearing frame 2 is worn on the human body through the multi-material inner lining component 1. The ankle joint hinge component is located at the lower end of the carbon fiber load-bearing frame 2 and is used to connect with the shoe 8. The carbon fiber load-bearing frame 2 is provided with a rope drive mechanism, which is connected to the ankle joint hinge component. The multi-material liner component 1 is manufactured by multi-material melt deposition molding, including a flexible region as a buffer system and a rigid region as a supporting skeleton. The flexible region is arranged on both sides of the rigid region. The material of the flexible region is a flexible material, and the material of the rigid region is a rigid chopped fiber composite material. A three-dimensional gradient lattice interlocking rigid-flexible material transition zone connects the flexible region and the rigid region.

[0033] Furthermore, the three-dimensional gradient lattice interlocking rigid-flexible material transition zone is manufactured by multi-nozzle fused deposition modeling technology. First, a three-dimensional lattice skeleton is printed with a rigid short-cut fiber composite material, and then a flexible material is used to fill and cover the internal cavity of the three-dimensional lattice skeleton to form a volumetric interlocking interface. The rigid chopped fiber composite material in the transition zone has multiple holes distributed on it, and the flexible material in the transition zone has multiple protrusions that fill and embed in the corresponding holes of the rigid chopped fiber composite material; and / or the flexible material in the transition zone has multiple holes distributed on it, and the rigid chopped fiber composite material in the transition zone has multiple protrusions that fill and embed in the corresponding holes of the flexible material. Along the transition zone from the rigid region to the flexible region, the proportion of rigid chopped fiber composite material in the transition zone gradually decreases, while the porosity of the rigid chopped fiber composite material gradually increases or the porosity of the flexible material gradually decreases.

[0034] Furthermore, porosity includes the size of the pores and / or the number of pores per unit area. In the transition zone from the rigid region to the flexible region, the size of the pores and / or the number of pores per unit area in the rigid chopped fiber composite material gradually increases, or in the transition zone, the size of the pores and / or the number of pores per unit area in the flexible material gradually decreases.

[0035] Furthermore, the rigid area of ​​the multi-material liner assembly 1 is provided with a flange or reinforcing ring structure, and the carbon fiber load-bearing skeleton 2 is provided with mounting holes or embedding grooves that are adapted to the flange or reinforcing ring structure. The multi-material liner assembly 1 is positioned and fixedly connected with the mounting holes or embedding grooves through the flange or reinforcing ring structure, and screws or bolts are provided at the flange or reinforcing ring structure for strong connection.

[0036] Furthermore, the ankle joint hinge assembly is hinged to the lower end of the carbon fiber load-bearing frame 2, and the ankle joint hinge assembly integrates an angle encoder.

[0037] Furthermore, the carbon fiber load-bearing frame 2 is detachably connected to each component via screws or embedded fasteners, forming a rigid-flexible coupling system.

[0038] Furthermore, the carbon fiber load-bearing frame 2 includes two parallel load-bearing plates, with a transverse connecting plate between the two load-bearing plates. The two ends of the multi-material inner lining assembly 1 are respectively connected to the two load-bearing plates. A transmission rope seat 6 is provided on the transverse connecting plate, and the upper end of the transmission rope 4 is connected to the transmission rope seat 6. There are two multi-material lining components 1, which are arranged opposite to each other on the two load-bearing plates of the carbon fiber load-bearing frame 2. The two multi-material lining components 1 cover the limb from both sides, and the two ends of the two multi-material lining components 1 are connected by a detachable connection.

[0039] Furthermore, detachable connection methods include Velcro 9 or adhesive fabric materials, or quick snaps or magnetic attachments.

[0040] The flexible materials at both ends of the multi-material lining component 1 are provided with pre-embedded Velcro 9 or adhesive fabric material, which are used to fix the two ends of the multi-material lining component 1 by Velcro 9 or adhesive fabric material after the multi-material lining component 1 is wrapped around the limb.

[0041] Furthermore, the pre-embedding process for Velcro 9 or adhesive fabric material is as follows: (e.g.) Figure 5 As shown, first print the first layer of flexible material, place the hook and loop fastener 9 or adhesive fabric material on the first layer of flexible material, then print the second layer of flexible material on the first layer of flexible material. The second layer of flexible material is arranged on both sides of the hook and loop fastener 9 or adhesive fabric material, and its thickness is approximately the same as or the same as that of the hook and loop fastener 9 or adhesive fabric material. Then print the third layer of flexible material on the second layer of flexible material. The third layer of flexible material covers the edge of the hook and loop fastener 9 or adhesive fabric material, avoiding the main adhesive part of the hook and loop fastener 9 or adhesive fabric material, such as avoiding the hook side of the hook and loop fastener 9.

[0042] The rope drive mechanism includes a drive unit and a transmission rope 4. The drive unit is fixed on the carbon fiber load-bearing frame 2. The ankle joint hinge assembly is provided with a transmission rope connector 5. The drive unit is connected to one end of the transmission rope 4, and the other end of the transmission rope 4 is connected to the transmission rope connector 5. The drive unit drives the ankle joint hinge assembly and the shoe 8 to rotate around the hinge point through the transmission rope 4.

[0043] Furthermore, the guide pulley is arranged along the carbon fiber load-bearing frame 2, and the transmission rope 4 passes around the guide pulley and connects to the transmission rope joint 5.

[0044] Furthermore, the ankle hinge assembly includes a foot frame and an ankle hinge 10. The front end of the foot frame is hinged to the shoe 8, and an elastic rope 7 is connected between the rear end of the foot frame and the shoe 8. The foot frame is hinged to the lower end of the carbon fiber load-bearing frame 2 via the ankle hinge 10, and the transmission rope connector 5 is located at the rear end of the foot frame.

[0045] Furthermore, the transmission rope 4 is connected to the ankle joint via a guide pulley to achieve flexion and extension assistance, and the transmission rope 4 is provided with a Bowden tube 3.

[0046] Example 2 Based on Example 1, the ankle joint hinge assembly is further defined, resulting in Example 2 having even better performance.

[0047] The tripod includes two parallel footboards, with a transverse ankle connecting plate connecting the two footboards. The transverse ankle connecting plate is located above the rear side of the shoe 8, and the transmission rope connector 5 is located on the transverse ankle connecting plate. The drive unit includes a motor and a winding wheel. The winding wheel is located on the output shaft of the motor, and the transmission rope is wound around the winding wheel.

[0048] Furthermore, the front end of the shoe 8 is provided with a groove into which a carbon plate for the foot component is inserted. The front end of the footrest plate of the foot frame is hinged to the carbon plate for the foot component of the shoe 8. An elastic rope 7 is connected between the rear end of the shoe 8 and the ankle transverse connecting plate at the rear end of the foot frame.

[0049] The carbon plate of the foot piece is fixed to the groove of the shoe piece 8 with glue, and the elastic rope 7 is inserted into the drilled hole at the rear end of the shoe piece 8.

[0050] Furthermore, the rigid chopped fiber composite material is PLA-CF or PLA-GF, and the flexible material is TPU.

[0051] Furthermore, the transition area between the multi-material inner lining component 1 and the carbon fiber load-bearing frame 2 is provided with an external interface layer, which is a pre-embedded Velcro 9 or an adhesive fabric material, pre-set and embedded during the flexible material printing process.

[0052] Furthermore, the material of the carbon fiber load-bearing frame 2 can be replaced with glass fiber reinforced plastic or aluminum alloy; The rope drive mechanism can be replaced with a pneumatic artificial muscle or a screw sliding drive structure.

[0053] Furthermore, the rigid chopped fiber composite material can also be nylon or PETG, used in combination with TPU as a flexible material to form a multi-material liner assembly 1.

[0054] Furthermore, the multi-material inner lining component 1 is printed in a customized shape based on human body three-dimensional scan data to fit the shape of the user's calf and instep, significantly enhancing personalized fit.

[0055] A method for manufacturing a rigid-flexible coupled ankle exoskeleton based on multi-material fused deposition modeling as described above includes the following steps: S1: Design a three-dimensional model of the multi-material liner component 1 based on human body three-dimensional scanning data. The model includes a rigid short-cut fiber composite material region, a flexible material region, a three-dimensional gradient lattice interlocking rigid-flexible material transition region, and a flange or reinforcing ring structure at the edge of the rigid region. The installation position of the external interface layer is preset in the rigid-flexible transition region. S2: Using a multi-nozzle fused deposition modeling (FDM) device, rigid short-fiber composite materials and flexible materials are deposited in tandem according to the design model. First, the three-dimensional lattice skeleton of the rigid short-fiber composite material and the support skeleton with flange or reinforcing ring structure are printed. Then, the flexible material is filled to form a buffer system. At the same time, the pre-embedded external interface layer is completed to produce a multi-material inner liner component 1. S3: Process the carbon fiber load-bearing skeleton 2, and process the mounting holes, embedding grooves and ankle joint hinge module mounting structure that are adapted to the flange or reinforcing ring structure at the preset position, and integrate the angle encoder into the ankle joint hinge. S4: If a rope drive mechanism is included, the multi-material inner lining component 1, the carbon fiber load-bearing frame 2 and the rope drive mechanism are assembled and fixed by screws or embedded fasteners to form a complete exoskeleton system; if a rope drive mechanism is not included, the multi-material inner lining component 1 and the carbon fiber load-bearing frame 2 are assembled and fixed by screws or embedded fasteners to form a basic rigid-flexible coupling exoskeleton structure.

[0056] Working principle of the invention: I. Overall Structure This ankle exoskeleton mainly consists of three parts: a multi-material liner assembly, a carbon fiber load-bearing skeleton, and a cable-driven mechanism. The multi-material liner assembly is the core fitting structure, achieving a transition between rigidity and flexibility and providing localized cushioning through a flexible-rigid layered composite structure. The carbon fiber skeleton serves as the main load-bearing support frame of the system. The cable-driven mechanism assists in ankle flexion and extension. The components are assembled using screw connections or embedded fasteners to form a unified rigid-flexible coupling system. This assembly method not only ensures the reliability and maintainability of the connections but also facilitates module replacement and structural adjustments, thus achieving a detachable and highly integrated design for the system.

[0057] II. Multi-material lining components The multi-material liner assembly is manufactured through multi-material fused deposition modeling, comprising two parts: flexible materials (such as TPU) and rigid chopped fiber composites (such as PLA-CF (chopped carbon fiber reinforced polylactic acid) and PLA-GF (chopped glass fiber reinforced polylactic acid)). The flexible and rigid materials are distributed in a spatially staggered and functionally zoned manner. The rigid areas form a continuous supporting skeleton for force transmission and structural stability; the flexible areas construct an internal encapsulating cushioning system to ensure fit and comfort. By controlling the material distribution and filling density in local areas, the synergistic optimization of mechanical properties and compliance characteristics can be achieved macroscopically, enabling the liner to possess both structural load-bearing capacity and meet ergonomic flexibility requirements.

[0058] III. Structural Design of Transition Zone for Three-Dimensional Gradient Lattice Interlocking Rigid-Flexible Materials To enhance the stability and interface durability of exoskeleton devices under complex stress conditions, a multi-material rigid-flexible transition zone structure based on the principle of three-dimensional lattice interlocking was constructed. This structure utilizes multi-nozzle fused deposition modeling (FDM) technology. First, a three-dimensional lattice skeleton is printed using a rigid material (such as PLA-CF), and its topology is precisely modeled to form the main load-bearing paths. Then, based on the Boolean inversion model of the lattice, flexible materials (such as TPU) are used to fill and encapsulate the internal cavities, allowing the flexible units to form a complementary distribution with the rigid lattice in three-dimensional space. This process generates channel-level, node-level, and unit-level geometric interlocking in both the XY plane and the Z direction, forming a volumetric interlocking interface, rather than the traditional simple surface adhesion. The flexible material penetrates and encapsulates the rigid units along the lattice channels and pores, providing not only self-supporting molding conditions but also ensuring interface topological continuity, significantly suppressing interlayer delamination, void formation, and the propagation of brittle fracture in PLA.

[0059] During the printing process, the two printheads work collaboratively based on a unified coordinate system: the PLA printhead first forms a stable single-layer lattice pattern for printing, while the TPU printhead then deposits along a Boolean inversion path, allowing the flexible phase to be embedded layer by layer into the rigid framework, achieving spatial interpenetration and material coupling. Thanks to the volumetric interlocking structure formed by complementary topologies, the rigid and flexible phases remain completely continuous within their respective spatial domains, while achieving three-dimensional mechanical interlocking at the interface. Therefore, even under repeated bending, shearing, or multi-axial coupling loads, the interface maintains a highly stable bond without peeling or damage. To further optimize the interfacial mechanical behavior, a gradient design is introduced into the interlocking structure. By adjusting the porosity and wall thickness of the lattice units along the spatial direction, the structure gradually transitions from a high-density, high-stiffness lattice on the rigid side to a low-density, high-compliance topology on the flexible side, achieving continuous changes in material properties. This "interlocking + gradient" combination smooths the stress transmission path, reduces stress concentration caused by abrupt changes in material properties, and achieves a good balance between compliance and interfacial durability.

[0060] IV. Carbon Fiber Load-Bearing Frame The carbon fiber skeleton primarily serves as a rigid support frame, utilizing lightweight sheet metal cutting and screw assembly, with load-bearing areas designed according to the human lower leg. The skeleton incorporates mounting holes or recessed slots for connection to the printed inner lining components and the rope drive mechanism, enabling force transmission and drive support. The carbon fiber skeleton provides the system's main load-bearing capacity, while connecting to the footwear via elastic ropes and achieving closed-loop force transmission to the power source through a transmission rope connector, thus outputting auxiliary power to the ankle joint. This structure includes an ankle joint hinge module to limit the joint's range of motion and rotation axis, ensuring a natural biomechanical trajectory while preventing overflexion, torsion, or abnormal coupling movements. An angle encoder is integrated at the hinge to collect real-time ankle joint angle changes, forming input parameters for the drive control system, enabling dynamic response and precise tracking of the user's gait intentions. The motion data collected by the encoder can be further used for force control strategy optimization, gait prediction, and enhanced human-computer interaction immersion, transforming the drive output from passive mechanical transmission to a sensing intelligent assistance system. It is important to emphasize that in the structural system of this invention, the design focus of the carbon fiber skeleton is to provide a high-strength load-bearing frame and kinematic constraints, rather than a personalized fit to the user's limb surface. V. External Interface Layer (Taking Pre-embedded Velcro as an Example) An external interface layer is provided in the transition area between the rigid and flexible layers to expand the functionality of the exoskeleton device and improve wearing comfort. This interface layer can be made of pre-embedded Velcro or other adhesive fabric materials, pre-set and embedded according to the shape contour during the flexible layer printing and manufacturing process. This pre-embedded structure creates a re-adhesive external interface area on the device surface, facilitating the installation of attachments such as straps and protective covers. This design ensures both the overall continuity and enclosure of the flexible layer while providing an open functional expansion platform, giving the exoskeleton device greater modularity and adaptability.

[0061] VI. Connection Method The multi-material liner assembly is connected to the frame via screws or embedded fasteners. The edges of the rigid layer can be designed with flanges or reinforcing rings to improve fit with the frame and overall rigid-flexible transition stability. This detachable connection method facilitates maintenance and component replacement while ensuring the system's mechanical performance.

[0062] VII. Rope Drive Mechanism The rope-driven mechanism includes a drive unit, a transmission rope, and guide pulleys. The drive unit can adopt a motor-rope winding structure, fixed to the frame; the rope is guided by pulleys and connected to the ankle joint to achieve flexion and extension assisted movements. The pulley bracket can be made of metal or high-strength plastic and fixed with screws to ensure guiding accuracy and drive reliability.

[0063] VIII. Working Principle When the system is in operation, the carbon fiber skeleton bears the main load and provides structural strength, the flexible printed layer conforms to the curves of the human body to provide cushioning, and the rigid printed layer forms a transition zone between the flexible layer and the skeleton to achieve force transmission and fixation. The cable drive mechanism transmits driving force through the skeleton to provide ankle joint assistance. The rigid-flexible composite structure reduces the overall weight, reduces stress concentration, and improves wearing comfort and system durability.

[0064] IX. Key Innovations (1) A multi-material fused deposition modeling technology for exoskeleton systems is proposed. By integrating flexible and rigid materials in the same printing process, the overall forming and stable rigid-flexible combination of the exoskeleton support structure can be achieved. It is suitable for curved surface fitting and long-term wearing scenarios.

[0065] (2) To address the periodic bending and complex stresses experienced by the exoskeleton during movement, a lattice-based three-dimensional interlocked rigid-flexible transition zone structure was designed. Furthermore, a variable gradient lattice design was introduced to achieve continuous control of the stiffness and mechanical properties of the interface region. By maintaining a high-density, high-stiffness lattice in the joint region to bear the driving load, while gradually transitioning to a low-density, highly compliant topology in the skin-contact region, the structure effectively suppresses interface delamination, crack propagation, and stress concentration while ensuring lightweight design. This improves the reliability of the exoskeleton under dynamic conditions and the stability of driving force transmission, while also meeting the mechanical requirements of different functional areas.

[0066] (3) By using a synergistic printing method of rigid short-cut fiber reinforced material and flexible material, a local reinforcement structure suitable for the high load transmission path of exoskeleton is constructed, which not only improves the interlayer bonding ability, but also improves the fatigue durability of exoskeleton under high-frequency gait conditions.

[0067] (4) To meet the needs of wearing and quickly assembling exoskeletons, the fasteners such as Velcro are directly integrated by using additive manufacturing embedded parts, reducing the traditional sewing and bonding process, and improving the ease of wearing, structural consistency and service life.

[0068] 10. Alternative Implementation Methods The skeleton material can be replaced with glass fiber reinforced plastic or aluminum alloy, and multi-material printing materials can be selected from combinations of nylon, TPU, PETG, etc.; in addition to screws, quick snaps or magnetic adsorption can be used for connection; the rope drive mechanism can be replaced with pneumatic artificial muscle or lead screw sliding drive structure.

[0069] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0070] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A rigid-flexible coupled ankle exoskeleton based on multi-material fused deposition modeling, characterized in that: It includes a multi-material lining assembly, a carbon fiber load-bearing frame, and an ankle hinge assembly. The multi-material lining assembly is detachably connected to the carbon fiber load-bearing frame, and the ankle hinge assembly is located at the lower end of the carbon fiber load-bearing frame and is used to connect with footwear. The multi-material liner assembly is manufactured by multi-material fused deposition modeling, including flexible regions and rigid regions. The flexible regions are arranged on both sides of the rigid regions. The material of the flexible regions is flexible material, and the material of the rigid regions is rigid chopped fiber composite material. A three-dimensional gradient lattice interlocking rigid-flexible material transition region connects the flexible regions and the rigid regions. The three-dimensional gradient lattice interlocking rigid-flexible material transition zone is manufactured by multi-nozzle fused deposition modeling technology. First, a three-dimensional lattice skeleton is printed with a rigid short-cut fiber composite material, and then a flexible material is used to fill and cover the internal cavity of the three-dimensional lattice skeleton to form a volumetric interlocking interface. The rigid chopped fiber composite material in the transition zone has multiple holes distributed on it, and the flexible material in the transition zone has multiple protrusions that fill and embed in the corresponding holes of the rigid chopped fiber composite material; and / or the flexible material in the transition zone has multiple holes distributed on it, and the rigid chopped fiber composite material in the transition zone has multiple protrusions that fill and embed in the corresponding holes of the flexible material. Along the transition zone from the rigid region to the flexible region, the proportion of rigid chopped fiber composite material in the transition zone gradually decreases, while the porosity of the rigid chopped fiber composite material gradually increases or the porosity of the flexible material gradually decreases.

2. The rigid-flexible coupled ankle exoskeleton based on multi-material fused deposition modeling as described in claim 1, characterized in that: The ankle joint hinge assembly is hinged to the lower end of the carbon fiber load-bearing frame, and the ankle joint hinge assembly integrates an angle encoder.

3. The rigid-flexible coupled ankle exoskeleton based on multi-material fused deposition modeling as described in claim 1, characterized in that: The carbon fiber load-bearing frame includes two parallel load-bearing plates with a transverse connecting plate between them. The two ends of the multi-material liner assembly are connected to the two load-bearing plates respectively. There are two multi-material lining components, which are arranged opposite each other on the two load-bearing plates of the carbon fiber load-bearing frame. The two multi-material lining components cover the limb from both sides, and the two ends of the two multi-material lining components are connected by a detachable connection.

4. The rigid-flexible coupled ankle exoskeleton based on multi-material fused deposition modeling as described in claim 1, characterized in that: The carbon fiber load-bearing frame is equipped with a rope drive mechanism, which is connected to the ankle joint hinge assembly. The rope drive mechanism is used to drive the movement of the ankle joint hinge assembly. The rope-driven mechanism includes a drive unit and a transmission rope. The drive unit is fixed to the carbon fiber load-bearing frame. The ankle joint hinge assembly is provided with a transmission rope connector. The drive unit is connected to one end of the transmission rope, and the other end of the transmission rope is connected to the transmission rope connector. The drive unit drives the ankle joint hinge assembly and the shoe to rotate around the hinge point through the transmission rope.

5. The rigid-flexible coupled ankle exoskeleton based on multi-material fused deposition modeling as described in claim 4, characterized in that: The ankle hinge assembly includes a foot frame and an ankle hinge. The front end of the foot frame is hinged to the shoe, and an elastic rope connects the rear end of the foot frame to the shoe. The foot frame is hinged to the lower end of the carbon fiber load-bearing frame via the ankle hinge, and the transmission rope connector is located at the rear end of the foot frame.

6. The rigid-flexible coupled ankle exoskeleton based on multi-material fused deposition modeling as described in claim 5, characterized in that: The tripod includes two parallel footboards, with a transverse ankle connecting plate between the two footboards. The transverse ankle connecting plate is located above the rear of the shoe, and the drive rope connector is located on the transverse ankle connecting plate. The drive unit includes a motor and a winding wheel. The winding wheel is located on the output shaft of the motor, and the transmission rope is wound around the winding wheel.

7. The rigid-flexible coupled ankle exoskeleton based on multi-material fused deposition modeling as described in claim 1, characterized in that: The rigid short-cut fiber composite material is PLA-CF or PLA-GF, and the flexible material is TPU; The carbon fiber load-bearing skeleton can also be made of glass fiber reinforced plastic or aluminum alloy.

8. The rigid-flexible coupled ankle exoskeleton based on multi-material fused deposition modeling as described in claim 4, characterized in that: The rope drive mechanism can be replaced with a pneumatic artificial muscle or a screw sliding drive structure.

9. A method for manufacturing a rigid-flexible coupled ankle exoskeleton based on multi-material fused deposition modeling as described in any one of claims 1 to 8, characterized in that, Includes the following steps: S1: Design a 3D model of a multi-material lining component based on human body 3D scanning data; S2: Using a multi-nozzle fused deposition modeling (FDM) device, rigid short-fiber composite materials and flexible materials are deposited in synergistic deposition according to the designed three-dimensional model. First, the three-dimensional lattice skeleton of the rigid short-fiber composite material is printed as a support skeleton, and then the flexible material is filled to form a buffer system, thus producing a multi-material liner component. S3: Machining a carbon fiber load-bearing frame and integrating the angle encoder into the ankle joint hinge assembly; S4: Connect and assemble the multi-material inner lining components and carbon fiber load-bearing frame to form a complete exoskeleton system.

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