Knee joint assisting exoskeleton

Abstract

The application discloses a knee joint assisting exoskeleton and belongs to the exoskeleton field. First and second inertia measurement sensors are arranged on the thigh and calf clamp mechanisms; the shell of the assisting mechanism is fixed with the thigh clamp mechanism, and two first and second racks are slidably arranged on the two sides of the shell; a motor is fixed to the shell, a first gear sleeve is arranged on the motor, a second and third gears are engaged with the first gear, a fourth and third gears are engaged, and the second and fourth gears are engaged with the first and second racks on the corresponding side; the two ends of first and second connecting rods are respectively fixed with the lower parts of the two first and second racks; the first ends of first and second curved beams are respectively sleeved with the first and second connecting rods; the two ends of a third connecting rod are fixed with the calf clamp mechanism; the second ends of the first and second curved beams are both sleeved with the third connecting rod; a foot bottom pressure sensor is arranged on the foot bottom; the first and second inertia measurement sensors, the motor and the foot bottom pressure sensor are all electrically connected with a development board. The application can realize accurate matching of the motion characteristics and rigidity requirements of the knee joint.

Description

Technical Field

[0001] This application relates to the field of exoskeleton technology, and more particularly to a knee joint assistive exoskeleton. Background Technology

[0002] Assisted exoskeletons are wearable devices that enhance human mobility through mechanical structures, sensors, and driven knee joints. Their joint structures are matched to the kinetic structures of the hip, knee, and ankle. With the continuous advancement of assisted exoskeleton technology, these devices are increasingly being used to assist movement in spinal cord injury patients, stroke rehabilitation, aging assistance, walking, weight-bearing, and other dynamic movement scenarios.

[0003] The knee joint, as a crucial component of the human musculoskeletal system and a key hub for lower limb movement, plays an irreplaceable role in supporting body weight and ensuring motor function. Due to its complex structure and functional requirements, the knee joint is susceptible to injury and degeneration, impacting daily life and athletic ability. Thanks to continuous advancements in science and technology, wearable knee exoskeletons have rapidly developed in areas such as rehabilitation medicine, muscle enhancement, and metabolic reduction, providing new treatment and assistance methods. The knee joint's support requirements not only include torque support but also involve the precise matching of knee joint stiffness across different movement patterns.

[0004] However, existing knee-assisting exoskeletons generally employ a fixed-stiffness design. While these designs can meet basic assistance needs, they lack flexible responses to dynamic motion characteristics. They cannot dynamically adjust to different exercise requirements and individual wearer differences, failing to achieve a precise match between knee joint motion characteristics and stiffness requirements. This limits their adaptability and effectiveness, resulting in poor user comfort. Especially in complex movement patterns, fixed-stiffness exoskeletons struggle to provide optimal assistance, potentially leading to increased user fatigue and reduced exercise efficiency. Summary of the Invention

[0005] This application provides a knee joint assistive exoskeleton that solves the problem that existing knee joint assistive exoskeletons cannot achieve precise matching of knee joint movement characteristics and stiffness requirements, which limits their adaptability, effectiveness, and user comfort, and may lead to increased user fatigue and reduced exercise efficiency.

[0006] To achieve the above objectives, the technical solution of this invention is as follows:

[0007] This invention provides a knee joint assistive exoskeleton, including a thigh clamping mechanism, a calf clamping mechanism, a first inertial measurement sensor, a second inertial measurement sensor, an assistive mechanism, a plantar pressure sensor, and a development board;

[0008] The first inertial measurement sensor is disposed on the thigh clamping mechanism, and the second inertial measurement sensor is disposed on the calf clamping mechanism;

[0009] The assist mechanism includes a housing, a motor, a first rack, a second rack, a first gear, a second gear, a third gear, a fourth gear, a first connecting rod, a second connecting rod, a third connecting rod, a first curved beam, and a second curved beam;

[0010] The outer shell is fixed to the thigh clamping mechanism, and the two first racks and the two second racks are slidably disposed on both sides of the outer shell, wherein the length of the teeth of the first racks is less than the length of the teeth of the second racks;

[0011] The motor is fixed to the housing, the first gear is sleeved on the output shaft of the motor, the second gear meshes with the first gear, the third gear meshes with the first gear, the fourth gear meshes with the third gear, the second gear meshes with the first rack and the second rack on the corresponding side, and the fourth gear meshes with the first rack and the second rack on the corresponding side.

[0012] The two ends of the first connecting rod are fixed to the lower parts of the two first racks, and the two ends of the second connecting rod are fixed to the lower parts of the two second racks.

[0013] The first ends of the first curved beam and the second curved beam are respectively sleeved on the first connecting rod and the second connecting rod;

[0014] The two ends of the third link are fixed to the lower leg clamping mechanism;

[0015] The second ends of both the first curved beam and the second curved beam are sleeved on the third connecting rod;

[0016] The plantar pressure sensor is located on the sole of the foot;

[0017] The first inertial measurement sensor, the second inertial measurement sensor, the motor, and the plantar pressure sensor are all electrically connected to the development board.

[0018] In one possible implementation, the plantar pressure sensor includes a flexible substrate layer, a pressure-sensitive layer, a pressure sensing unit, a conductive circuit layer, and a protective encapsulation layer.

[0019] The flexible substrate layer is made of polyester film and its surface is covered with a highly conductive metal foil;

[0020] The pressure-sensitive layer is disposed above the flexible substrate layer and is made of a pressure-sensitive composite material, which includes a conductive filler and an elastic polymer matrix, and its resistance value changes non-linearly with pressure.

[0021] The pressure sensing unit includes three units, which are respectively located in the first metatarsal region, the fourth metatarsal region, and the calcaneal region of the human foot. Each pressure sensing unit forms an isolation groove on the pressure-sensitive layer through an etching process to limit its sensing range. All units are electrically connected to the development board and are used to monitor the plantar pressure distribution data in real time and send the data to the development board for gait analysis.

[0022] The conductive circuit layer includes an independent signal transmission path corresponding to each pressure sensing unit. The common ground terminal of each path is located at the rear end of the flexible substrate layer, and the signal output terminals are respectively located at the edge of each pressure sensing unit.

[0023] The protective encapsulation layer covers the pressure-sensitive layer and the conductive circuit layer, and its surface has a curved shape adapted to the anatomical structure of the sole of the foot.

[0024] In one possible implementation, the first link, the second link, the third link, the first curved beam, and the second curved beam are all integrally formed by 3D printing of polylactic acid material.

[0025] In one possible implementation, the assist mechanism further includes a limiter;

[0026] A limiter is provided above the upper end of the teeth of both the first rack and the second rack.

[0027] In one possible implementation, the stiffness ratio of the first curved beam between the support phase and the swing phase is 5:1;

[0028] And / or, the stiffness ratio of the second curved beam between the support phase and the swing phase is 5:1.

[0029] In one possible implementation, the geometric parameters of the curved beam are optimized using a finite element analysis method; wherein the geometric parameters include at least the thickness and radius of the curved beam; the optimization objective is to provide an average stiffness of 400 N·m / rad during the support phase and an average stiffness of 60 N·m / rad during the oscillation phase of the knee exoskeleton.

[0030] In one possible implementation, optimizing the geometric parameters of the curved beam using the finite element analysis method includes:

[0031] Define the material properties of the curved beam, including Young's modulus, Poisson's ratio, and density;

[0032] A parametric model is established in the finite element analysis software, and boundary conditions are set: the bottom end of the curved beam is fixed, and a displacement load is applied to the top end;

[0033] Multiple sets of simulation analyses were conducted, with thickness and radius used as variables respectively.

[0034] Based on the stiffness calculation formula K=ΔF / Δy, the stiffness values ​​under different geometric parameters are calculated, where ΔF is the force value corresponding to the stress difference obtained from the simulation, and Δy is the displacement difference;

[0035] Based on the stiffness-thickness and stiffness-radius variation trend diagrams obtained from simulation, the optimal combination of thickness and radius is selected.

[0036] In one possible implementation, the knee-assisted exoskeleton also includes simulation and experimental verification of the performance of the combined structure of the first and second curved beams:

[0037] In the finite element software, a model of the combined structure of the first and second curved beams placed on top of each other was created, and the same material properties, mesh size and constraints were set.

[0038] By applying displacement loads, the stiffness and stress response of the combined structure of the first and second curved beams are obtained through simulation.

[0039] Post-processing analysis was used to verify whether the stiffness superposition of the combined structure of the first and second curved beams was linear.

[0040] A 3D-printed curved beam was subjected to static experiments, with vertical displacement applied and force-displacement data recorded.

[0041] By comparing the simulated stiffness ratio, the experimental stiffness ratio, and the target stiffness ratio, the design accuracy and structural effectiveness are verified.

[0042] One or more technical solutions provided in the embodiments of the present invention have at least the following technical effects or advantages:

[0043] The knee-assisted exoskeleton provided in this application embodiment, in actual use, involves wearing a thigh clamp mechanism on the thigh and a calf clamp mechanism on the calf. A first inertial measurement sensor is mounted on the thigh clamp mechanism, a second inertial measurement sensor is mounted on the calf clamp mechanism, and a plantar pressure sensor is mounted on the sole of the foot. The first and second inertial measurement sensors, the motor, and the plantar pressure sensor are all electrically connected to a development board. The first and second inertial measurement sensors measure changes in the knee joint angle and transmit the data to the development board, while the plantar pressure sensor measures the plantar pressure distribution and transmits the data to the development board. Upon receiving the data, the development board sends an execution command to the motor, which starts. The first gear is mounted on the motor's output shaft, and the motor's output shaft drives the first gear to rotate in a predetermined direction. The second and third gears mesh with the first gear, and the first gear drives the second and third gears to rotate synchronously. The fourth gear meshes with the third gear, and the third gear drives the fourth gear to rotate in the opposite direction. The second gear meshes with the corresponding first and second racks, and the fourth gear meshes with the corresponding first and second racks. The first and second racks move relative to the teeth of the second and fourth gears. The two first and two second racks are slidably mounted on both sides of the outer casing, allowing them to slide smoothly along the casing. The two ends of the first connecting rod are fixed to the lower parts of the two first racks, and the two ends of the second connecting rod are fixed to the lower parts of the two second racks. The first ends of the first and second curved beams are respectively fitted onto the first and second connecting rods. The two ends of the third connecting rod are fixed to the calf clamp mechanism. The second ends of both the first and second curved beams are fitted onto the third connecting rod. The movement of the first rack independently drives the movement of the first curved beam, and the movement of the second rack independently drives the movement of the second curved beam, then transmits the power to the calf clamp mechanism, achieving the goal of assisting the knee exoskeleton.

[0044] The core of the stiffness adjustment mechanism lies in the dynamic meshing and disengagement process between the first rack, second rack, second gear, and fourth gear. The first and second racks are arranged side by side, the second gear meshes with the corresponding first and second racks, and the fourth gear meshes with the corresponding first and second racks. At the start of the gait, the support phase requires high knee joint stiffness to maintain stability. At this time, the first and second curved beams closely mesh with the first and second racks, providing solid support to meet the stiffness requirements of the support phase during the gait cycle. When entering the swing phase, the knee joint stiffness requirement decreases. Because the upper ends of the teeth of the first and second racks are aligned, and the length of the first rack tooth is shorter than that of the second rack tooth, the meshing stroke of the first rack and second gear is deliberately shortened. At this time, the first rack, second gear, and fourth gear gradually disengage, and the second curved beam alone undertakes the auxiliary task to meet the stiffness requirements of the swing phase during the gait cycle. At the end of the swing phase, the traction of the lower leg movement causes the first rack to re-mesh with the second and fourth gears, restoring the stiffness support of the first curved beam, which then works together with the second curved beam to complete the support task. Therefore, the knee-assistive exoskeleton of this embodiment adjusts the relative positions of the second and fourth gears and the first and second racks, causing the first and second racks to reciprocate relative to the outer shell. This alters the actual stiffness of the knee-assistive exoskeleton, providing dynamic stiffness adjustment and support, and completing the corresponding auxiliary tasks. It achieves precise matching of knee joint movement characteristics and stiffness requirements, improving the adaptability, effectiveness, and user comfort of the knee-assistive exoskeleton, reducing user fatigue, and increasing exercise efficiency. Attached Figure Description

[0045] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0046] Figure 1 A schematic diagram of the structure of the knee joint assistive exoskeleton provided in the embodiments of this application. Figure 1 ;

[0047] Figure 2 A schematic diagram of the structure of the knee joint assistive exoskeleton provided in the embodiments of this application. Figure 2 ;

[0048] Figure 3 A schematic diagram of the electrical connections of the knee-assisted exoskeleton provided in an embodiment of this application;

[0049] Figure 4 This is a schematic diagram of the structure of the plantar pressure sensor provided in the embodiments of this application;

[0050] Figure 5 A schematic diagram of the structure of the knee joint assistive exoskeleton provided in the embodiments of this application. Figure 3 ;

[0051] Figure 6 A simulation diagram of the first curved beam provided in the embodiments of this application;

[0052] Figure 7 Three-dimensional stiffness-displacement diagrams of the first curved beam under different thickness conditions provided in the embodiments of this application;

[0053] Figure 8 Three-dimensional force-displacement diagrams of the first curved beam under different thickness conditions provided in the embodiments of this application;

[0054] Figure 9 Three-dimensional stiffness-displacement diagrams of the first curved beam under different radius conditions provided in the embodiments of this application;

[0055] Figure 10 Three-dimensional force-displacement diagrams of the first curved beam under different radius conditions provided in the embodiments of this application;

[0056] Figure 11 A simulation diagram of the combined structure of the first curved beam and the second curved beam provided in the embodiments of this application.

[0057] Figure 12 The stiffness-displacement variation diagrams of the first curved beam, the second curved beam, and the combined structure of the first curved beam and the second curved beam provided in the embodiments of this application, and the theoretical values.

[0058] Figure 13 Force-displacement variation diagrams of the first curved beam, the second curved beam, and the combined structure of the first curved beam and the second curved beam provided in the embodiments of this application, and theoretical values.

[0059] Reference numerals: 1-Thigh clamping mechanism; 11-Thigh clamp; 12-First strap; 13-Second strap; 14-First fixing frame; 2-Lower leg clamping mechanism; 21-Lower leg clamp; 22-Third strap; 23-Fourth strap; 24-Second fixing frame; 3-First inertial measurement sensor; 4-Second inertial measurement sensor; 5-Assist mechanism; 51-Housing shell; 52-Motor; 53-First rack; 54-Second rack; 55-First gear; 56-Second gear; 57-Third gear; 58-Fourth gear; 59-First connecting rod; 5A-Second connecting rod; 5B-Third connecting rod; 5C-First curved beam; 5D-Second curved beam; 5E-Limiter; 6-Foot pressure sensor; 61-Pressure sensing unit; 7-Development board; 8-Power supply. Detailed Implementation

[0060] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0061] In the description of the embodiments of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the embodiments of the present invention and for 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. Therefore, they should not be construed as limitations on the present invention. The terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, the terms "installed," "connected," and "linked" 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 connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of the present invention according to the specific circumstances.

[0062] Please refer to Figure 1 and Figure 2 As shown, this embodiment of the invention provides a knee joint assistive exoskeleton, including a thigh clamping mechanism 1, a calf clamping mechanism 2, a first inertial measurement sensor 3, a second inertial measurement sensor 4, an assistive mechanism 5, a plantar pressure sensor 6, and a development board 7.

[0063] like Figure 1 As shown, the thigh clamp mechanism 1 is worn on the human thigh. The thigh clamp mechanism 1 includes a thigh clamp 11, a first strap 12, a second strap 13, and a first fixing frame 14. The inner wall shape of the thigh clamp 11 is adapted to the shape of the thigh. The two ends of the first strap 12 are connected to the two ends of the top of the thigh clamp 11. The two ends of the second strap 13 are connected to the two ends of the bottom of the thigh clamp 11. One side of the first fixing frame 14 is fixed to the outer wall of the thigh clamp 11.

[0064] Continue to refer to Figure 1As shown, the calf clamp mechanism 2 is worn on the lower leg. The calf clamp mechanism 2 includes a calf clamp 21, a third strap 22, a fourth strap 23, and a second fixing frame 24. The inner wall shape of the calf clamp 21 is adapted to the shape of the lower leg. The two ends of the third strap 22 are connected to the two ends of the top of the calf clamp 21. The two ends of the fourth strap 23 are connected to the two ends of the bottom of the calf clamp 21. One side of the second fixing frame 24 is fixed to the outer wall of the calf clamp 21.

[0065] To improve the wearing comfort of the knee-assisted exoskeleton, the thigh clamp 11 and calf clamp 21 adopt a semi-enclosed design with different curvatures, and perforations are made at the locations where the thigh clamp 11 is close to the thigh muscle and the calf clamp 21 is close to the calf muscle. This not only reduces the pressure of the knee-assisted exoskeleton on the muscles and provides some room for muscle movement, but also meets the goal of lightweight knee-assisted exoskeleton. Because the anatomical structure of the thigh and calf is an irregular cylindrical shape that is wider at the top and narrower at the bottom, the inner walls of the thigh clamp 11 and calf clamp 21 adopt a tapered design to better conform to the leg contour, thereby improving wearing comfort and mechanical stability. For example, the thigh clamp 11 is 180mm long, with an inner radius of 86mm at the top and 72mm at the bottom.

[0066] The first strap 12, the second strap 13, the third strap 22, and the fourth strap 23 are 50mm wide hook and loop fasteners used in conjunction with the thigh clamp 11 and the calf clamp 21 to achieve a fixed connection between the knee joint-assisted exoskeleton and the lower limb.

[0067] The first inertial measurement sensor 3 is disposed on the thigh clamping mechanism 1, and the second inertial measurement sensor 4 is disposed on the calf clamping mechanism 2. When the human body is upright, both the first inertial measurement sensor 3 and the second inertial measurement sensor 4 remain parallel to the coronal plane of the human body. Specifically, as shown... Figure 1 As shown, the first inertial measurement sensor 3 is fixed to the middle of the second strap 13, and the second inertial measurement sensor 4 is fixed to the middle of the fourth strap 23. The coronal plane is the vertical plane that divides the human body into front and back parts. Inertial measurement sensor is abbreviated as IMU.

[0068] Combination Figure 1 and Figure 2 As shown, the power assist mechanism 5 includes a housing 51, a motor 52, a first rack 53, a second rack 54, a first gear 55, a second gear 56, a third gear 57, a fourth gear 58, a first connecting rod 59, a second connecting rod 5A, a third connecting rod 5B, a first curved beam 5C, and a second curved beam 5D.

[0069] The outer shell 51 is fixed to the thigh clamp mechanism 1. Specifically, the outer shell 51 is fixed to the side of the thigh clamp mechanism 1 opposite to the thigh clamp 11. Two first racks 53 and two second racks 54 are slidably disposed on both sides of the outer shell 51. Specifically, guide grooves are provided on both sides of the outer shell 51, and guide rails are provided on the outer sides of the first racks 53 and second racks 54. The guide rails are slidably disposed on the guide rails so that the two first racks 53 and two second racks 54 are slidably disposed on both sides of the outer shell 51. The first racks 53 and second racks 54 on the same side are arranged side by side. The upper ends of the teeth of the first racks 53 and second racks 54 are aligned, and the length of the teeth of the first rack 53 is less than the length of the teeth of the second rack 54.

[0070] Motor 52 is fixed to housing 51. In order to achieve the assistive effect of knee joint assistive exoskeleton in complex gait modes, precise motion control and rapid response are crucial. After comprehensively considering the high requirements of knee joint assistive exoskeleton for power control, precision and reliability, motor 52 uses Sigma servo motor (SG-6010H).

[0071] The Sigma servo motor utilizes a high-performance permanent magnet synchronous motor and a precision feedback-controlled knee-assisted exoskeleton. Its structure features high rigidity and low mechanical wear, effectively reducing errors and delays in dynamic response. Its built-in high-resolution encoder provides accurate real-time position feedback, ensuring high control precision and stability during rapid starts, stops, and speed changes. Furthermore, the low inertia design of the motor allows for faster response times during gait changes, making it particularly suitable for knee-assisted exoskeletons with complex gait variations.

[0072] The first gear 55 is sleeved on the output shaft of the motor 52. The second gear 56 meshes with the first gear 55, and the central axis of the second gear 56 is located below the central axis of the first gear 55. The third gear 57 meshes with the first gear 55, and the central axis of the third gear 57 is located below the first gear 55 and the second gear 56. The fourth gear 58 meshes with the third gear 57, and the central axis of the fourth gear 58 is located above the third gear 57. The second gear 56 meshes with the first rack 53 and the second rack 54 on the corresponding side, and the fourth gear 58 meshes with the first rack 53 and the second rack 54 on the corresponding side.

[0073] The two ends of the first connecting rod 59 are fixed to the lower parts of the two first racks 53, and the two ends of the second connecting rod 5A are fixed to the lower parts of the two second racks 54. The first ends of the first curved beam 5C and the second curved beam 5D are respectively sleeved on the first connecting rod 59 and the second connecting rod 5A. The two ends of the third connecting rod 5B are fixed to the calf clamping mechanism 2. Specifically, the two ends of the third connecting rod 5B are fixed to the top of the second bracket of the calf clamping mechanism 2. The second ends of the first curved beam 5C and the second curved beam 5D are both sleeved on the third connecting rod 5B, thereby connecting the calf clamping mechanism 2 with the first curved beam 5C and the second curved beam 5D, and then driving the curved beams to flex and extend the calf through the control strategy of the assist mechanism 5. The first connecting rod 59, the second connecting rod 5A, and the third connecting rod 5B are all 90mm long and 6mm in diameter.

[0074] The knee joint is the main load area that bears pressure and bending during human movement. The knee joint assist exoskeleton of this application moves the assist mechanism 5 out of the outer region of the knee joint, which not only reduces the load of the knee joint assist exoskeleton on the knee joint, but also ensures the natural range of motion of the knee joint, striving to provide interference-free assistance in dynamic movement.

[0075] The first curved beam 5C and the second curved beam 5D of the knee joint assistive exoskeleton in this embodiment of the application are 200mm in length, and the overall exoskeleton is 480.8mm.

[0076] The plantar pressure sensor 6 (FSR) is located on the sole of the foot. The first inertial measurement sensor 3, the second inertial measurement sensor 4, the motor 52, and the plantar pressure sensor 6 are all electrically connected to the development board 7.

[0077] The natural movements of the knee joint include many complex actions such as flexion, extension, and rotation. Knee-assisting exoskeletons must consider the range of knee flexion angles, flexion-extension rates, and rotation angles to ensure adaptive assistance at different stages of movement and prevent restriction of the wearer's natural movements. The first inertial measurement sensor 3 and the second inertial measurement sensor 4 are primarily used to monitor the movement state and posture changes of the lower limbs in gait information acquisition. They can collect real-time data on knee joint angle changes (angular velocity, acceleration, and spatial position data), exhibiting high sensitivity and accuracy. Their ability to independently measure movement states does not rely on external references, and they can still operate stably even under complex environmental conditions, providing dynamic and real-time data support for the knee-assisting exoskeleton's assistance strategy. The miniaturization and high integration of the IMU600 make it well-suited for knee-assisting exoskeletons, while its low power consumption ensures stable operation of the knee-assisting exoskeleton over extended periods.

[0078] Unlike common gait acquisition knee-assisted exoskeletons, the knee-assisted exoskeleton in this application employs a dual inertial measurement sensor system, consisting of a first inertial measurement sensor 3 and a second inertial measurement sensor 4. By mounting the first inertial measurement sensor 3 and the second inertial measurement sensor 4 on the anterior part of the mid-thigh and lower leg, respectively, and on the same side, when the body is upright, the first inertial measurement sensor 3 and the second inertial measurement sensor 4 are parallel to the coronal plane. The Z-axis angle between the first inertial measurement sensor 3 and the second inertial measurement sensor 4 is defined as the knee joint angle monitored by the knee-assisted exoskeleton, simultaneously monitoring the angular velocity, acceleration, and posture changes of these two locations. This configuration not only comprehensively reflects the dynamic changes of the knee joint during movement but also accurately identifies the support and swing phases in the gait cycle. Compared to a single inertial measurement sensor that can only collect local motion data, the dual inertial measurement sensor, by monitoring the relative motion relationship between the thigh and lower leg, can more clearly determine the user's current movement state, thereby effectively improving the accuracy of gait recognition. Special attention should be paid to the installation positions of the first inertial measurement sensor 3 and the second inertial measurement sensor 4 when wearing them, to ensure that the Z-axis of the first inertial measurement sensor 3 and the second inertial measurement sensor 4 are aligned, so as to ensure the accuracy of gait information acquisition.

[0079] The first inertial measurement sensor 3 and the second inertial measurement sensor 4 are equipped with Bluetooth modules, which can be paired and connected with the HC-05 Bluetooth module to transmit data to the development board 7 via Bluetooth communication. The built-in accelerometer and gyroscope can collect the acceleration and angular velocity of the wearer's legs, and provide accurate motion data to the knee joint assist exoskeleton through real-time feedback to support gait recognition and analysis.

[0080] The combination of the first inertial measurement sensor 3 and the second inertial measurement sensor 4 not only enables comprehensive monitoring of plantar pressure distribution and lower limb movement status, but also provides multi-dimensional data support for the intelligent control of the knee-assisted exoskeleton, contributing to the improvement of the overall performance and user experience of the knee-assisted exoskeleton. A gait information acquisition platform was built using the first inertial measurement sensor 3, the second inertial measurement sensor 4, and the plantar pressure sensor 6. Data visualization was achieved through VOFA+, providing support for gait feature extraction and movement status recognition.

[0081] The plantar pressure sensor 6 is installed on the sole of the wearer's foot. The resistance value is converted into a voltage signal through a voltage conversion module, which can measure the plantar pressure distribution data in real time and provide information about load and contact.

[0082] By integrating plantar pressure sensor 6 to collect plantar pressure distribution data and first inertial measurement sensor 3 and second inertial measurement sensor 4 to measure three-dimensional angle data of the knee joint (X-axis, Y-axis, and Z-axis), kinematic parameters during gait are collected collaboratively, comprehensively capturing gait characteristics and providing reliable data support for gait recognition and control logic. This allows for more accurate adjustments and adaptations in complex motion environments, ensuring optimal support for the knee-assisted exoskeleton. Simultaneously, based on the VOFA+ data visualization tool, the knee-assisted exoskeleton can display the collected multidimensional data in real time, intuitively presenting the dynamic changes in gait characteristics, thus laying the foundation for subsequent gait analysis and application research. The inertial sensors and plantar pressure sensor 6 are independent in principle, measuring different physical quantities respectively, ensuring that if one sensor malfunctions or errs, the other sensor can still provide effective data support, thereby enhancing the robustness of the entire knee-assisted exoskeleton.

[0083] To ensure the integrity of the gait cycle and the stable operation of the knee-assisted exoskeleton, plantar pressure sensors 6 are used as the trigger condition for gait cycle switching. When the signals from both plantar pressure sensors 6 become 0g and the data from the first inertial measurement sensor 3 and the second inertial measurement sensor 4 match the swing phase characteristics, the knee-assisted exoskeleton immediately triggers a reset logic, causing motor 52 to return to its initial position, ready to prepare for a new gait cycle. Through this mechanism, the exoskeleton can adjust its state in a timely manner during gait transitions, ensuring the continuity of the assistance mode and effectively reducing the occurrence of false triggers.

[0084] To enhance the stability and user experience of the knee-assisted exoskeleton, this control strategy is designed to balance real-time performance and adaptability. It utilizes angular changes from the first inertial measurement sensor 3 and the second inertial measurement sensor 4 for gait actuation. The knee-assisted exoskeleton can adjust according to the wearer's real-time movement, preventing gait deviations caused by lag and reducing overcompensation due to excessive angular errors, thereby improving the naturalness and smoothness of motion control. This gait-triggered control strategy only drives the motor 52 when necessary, avoiding unnecessary continuous output, reducing the exoskeleton's energy consumption, and improving its battery life, making it more suitable for extended wear. During gait transitions, the foot pressure sensor 6, along with data from the first and second inertial measurement sensors 3 and 4, jointly triggers the gait. This allows the knee-assisted exoskeleton to accurately determine gait changes, ensuring timely reset and adjustment, reducing control anomalies caused by data drift or minor erroneous movements, and improving the stability of gait switching.

[0085] Development board 7 can be used with the STM32F103RCT6 microcontroller, combining DMA and IDLE interrupts to efficiently receive serial port and ADC data, reducing the need for frequent CPU intervention. Whenever data is received by DMA, or after the UART / ADC completes data conversion, the IDLE interrupt triggers a relevant callback function by detecting the bus idle state. The callback function distinguishes different peripherals through the DMA handle and processes the data frame according to the length of the received data. In the callback function, the parsed attitude data is saved to the corresponding global variable. Simultaneously, to avoid additional interrupts, the DMA half-transfer interrupt is disabled. Subsequently, DMA reception is restarted, waiting to receive new data. The STM32F103RCT6 microcontroller can process data from sensors in real time and execute corresponding control instructions. During the operation of the knee-assisted exoskeleton, the STM32F103RCT6 is responsible for signal processing, sensor data acquisition, and motor 52 control. With its rich I / O interfaces and communication ports, it can efficiently connect to and process data input from multiple sensors. By interacting with different types of sensors, the STM32F103RCT6 can acquire multiple motion parameters in real time, such as gait information, plantar pressure distribution, and angle changes, providing real-time data for the dynamic adjustment of the knee-assisted exoskeleton. This real-time data processing capability enables the exoskeleton to quickly respond to the wearer's movement needs, providing a smoother experience. Development board 7 can also be an STM32 development board.

[0086] The exoskeleton not only simulates the movement of the knee joint but also senses the knee joint's angle, velocity, and mechanical state in real time, automatically adjusting its output. With the help of integrated sensors and feedback mechanisms, the knee-assisting exoskeleton of this embodiment can adaptively adjust in dynamic environments, providing appropriate support to the wearer and ensuring optimal assistance at all times and during different movement phases.

[0087] like Figure 3As shown, the knee-assisted exoskeleton also includes a power supply 8. The power supply 8 is electrically connected to the plantar pressure sensor 6, development board 7, motor 52, first inertial measurement sensor 3, and second inertial measurement sensor 4 to provide them with power. Two different power supply schemes were used in the selection of the power supply 8 for the knee-assisted exoskeleton to meet the power requirements of the development board 7 and the motor 52 respectively. The development board 7 is powered by a portable power bank, while the motor 52 uses a Gesch Ace 6S model aircraft battery (22.2V) as its driving power source. The portable power bank can provide a stable 5V voltage output, which meets the operating voltage requirements of the development board 7, and has built-in multiple protection mechanisms, such as overcharge, over-discharge, and short-circuit protection, which can effectively reduce the management risks of the power supply 8 and improve the stability of the knee-assisted exoskeleton. Furthermore, the portable power bank is small in size and light in weight, meeting the portability requirements of wearable devices and supporting long-term operation without the need for additional complex power management circuitry.

[0088] The Gestalt Ace 6S model aircraft battery provides high voltage (22.2V) and high current output, meeting the drive requirements of motor 52. Its high energy density ensures the knee-assist exoskeleton maintains excellent lightweight characteristics while ensuring long battery life. The Gestalt Ace 6S battery features low internal resistance and a high discharge rate, enabling motor 52 to respond quickly to control commands, improving real-time control accuracy during the gait cycle, and reducing power output lag or step loss caused by power supply fluctuations. Furthermore, the stable discharge characteristics of the model aircraft battery help ensure that the knee-assist exoskeleton can continuously provide sufficient driving force during highly dynamic gait changes without affecting the assistive effect due to voltage drops.

[0089] The dual power supply scheme physically isolates the power supply to development board 7 and motor 52, improving the safety and stability of the knee-assisted exoskeleton. If only the Ace 6S model aircraft battery is used, a step-down module is needed to reduce the voltage to 5V to meet the operating requirements of development board 7. However, due to the high voltage characteristics of model aircraft batteries, the step-down module may experience current surges or large ripples, potentially damaging development board 7 and affecting the overall stability of the knee-assisted exoskeleton. The independent power supply scheme not only avoids the circuit safety issues caused by high-voltage step-down but also reduces the impact of electromagnetic interference on the control of the knee-assisted exoskeleton, ensuring higher reliability and durability during complex gait control.

[0090] In the control of knee-assisted exoskeletons, the CAN bus (Controller Area Network Bus) is widely used for communication between the development board 7 and the motor 52 to ensure real-time transmission of control commands and efficient acquisition of motor 52 status data. The CAN bus has high anti-interference capability, real-time performance, and fault tolerance, making it suitable for motion control scenarios requiring precise synchronization. In the knee-assisted exoskeleton of this embodiment, the CAN bus is mainly used to transmit the target position control signal of the motor 52 generated by the development board 7 to the motor driver, while simultaneously receiving position feedback (joint angle and running status data) from the motor 52 to support the achievement of the gait tracking control strategy.

[0091] In the knee-assisted exoskeleton of this application embodiment, a CAN module is added to the development board 7 for communication configuration with the motor 52. The initialization and communication management of the CAN protocol are completed through the MX_CAN_Init function. By properly configuring the baud rate, filter, and data frame format, stable and efficient communication between the development board 7 and the motor 52 is achieved.

[0092] Gait is an important indicator for studying human walking characteristics. The gait cycle is generally divided into two parts: the stance phase and the swing phase. Taking the right foot during normal walking as an example, the stance phase is the stage where the right foot remains on the ground, accounting for 60% of the entire gait cycle. The swing phase is from the moment the right foot lifts off the ground until it touches down again, accounting for 40% of the entire gait cycle. A gait cycle begins when the right foot just touches the ground; at this point, the right heel strikes the ground while the left toes touch the ground, indicating a two-legged stance. Then, the right foot gradually lands fully, and the left toes are about to fully lift off the ground. This is the two-legged stance phase within the stance phase, accounting for 10% of the entire gait cycle. The primary supporting foot shifts from the left to the right, and the body's center of gravity shifts to the right. Next, the left toes lift off the ground, and the left leg begins to swing forward. The entire body weight is borne by the right foot. As the left foot swings forward past the right foot, the body's center of gravity gradually shifts forward, and the right heel begins to lift to maintain balance until the left heel is about to touch the ground. This phase, with the right leg supporting the body, accounts for 40% of the entire gait cycle and is the only phase in the gait cycle where the right leg is solely supported. From the moment the left heel begins to make contact with the ground until it is fully on the ground, the right heel gradually lifts off the ground until the toes are completely off the ground. This is the second two-legged support phase, which differs from the first in that the primary supporting foot changes from the right to the left, and the body's center of gravity shifts to the left foot. This phase accounts for 10% of the entire gait cycle. With the left foot fully on the ground and the right toes fully raised, the swing phase begins. The right foot swings forward, with the body weight entirely borne by the left foot. As the right foot swings forward past the left, the left heel lifts to maintain balance, and the body's center of gravity shifts forward until the right heel touches the ground again. This phase accounts for 40% of the entire gait cycle. Thus, the body has completed one full gait cycle. Throughout this cycle, the left and right feet alternately land to support the body, the center of gravity constantly shifts, and the primary supporting foot continuously changes position, repeating the movements within the gait cycle to enable walking in a specific direction.

[0093] The knee-assisted exoskeleton provided in this embodiment, in actual use, involves wearing a thigh clamp mechanism 1 on the thigh and a calf clamp mechanism 2 on the calf. A first inertial measurement sensor 3 is mounted on the thigh clamp mechanism 1, a second inertial measurement sensor 4 is mounted on the calf clamp mechanism 2, and a plantar pressure sensor 6 is mounted on the sole of the foot. The first inertial measurement sensor 3, the second inertial measurement sensor 4, the motor 52, and the plantar pressure sensor 6 are all electrically connected to a development board 7. The first inertial measurement sensor 3 and the second inertial measurement sensor 4 measure knee joint angle changes and transmit the data to the development board 7. The plantar pressure sensor 6 measures plantar pressure distribution data and transmits it to the development board 7. Upon receiving the data, the development board 7 sends an execution command to the motor 52. The motor 52 starts, and a first gear 55 is fitted onto the output shaft of the motor 52. The output shaft of the motor 52 drives the first gear 55 to rotate in a predetermined direction. The second gear 56 and the third gear 57 mesh with the first gear 55, and the first gear 55 drives the second gear 56 and the third gear 57 to rotate synchronously. The fourth gear 58 meshes with the third gear 57, and the third gear 57 drives the fourth gear 58 to rotate in opposite directions. The second gear 56 meshes with the first rack 53 and the second rack 54 on the corresponding side, and the fourth gear 58 meshes with the first rack 53 and the second rack 54 on the corresponding side. The first rack 53 and the second rack 54 move relative to the teeth of the second gear 56 and the fourth gear 58. The two first racks 53 and the two second racks 54 are slidably disposed on both sides of the outer casing 51, and thus the two first racks 53 and the two second racks 54 slide smoothly along the outer casing 51. The two ends of the first connecting rod 59 are fixed to the lower parts of the two first racks 53, and the two ends of the second connecting rod 5A are fixed to the lower parts of the two second racks 54. The first ends of the first curved beam 5C and the second curved beam 5D are respectively sleeved on the first connecting rod 59 and the second connecting rod 5A. The two ends of the third connecting rod 5B are fixed to the lower leg clamp mechanism 2. The second ends of the first curved beam 5C and the second curved beam 5D are both sleeved on the third connecting rod 5B. The movement of the first rack 53 independently drives the movement of the first curved beam 5C, and the movement of the second rack 54 independently drives the movement of the second curved beam 5D. The power is then transmitted to the lower leg clamp mechanism 2 to achieve the goal of assisting the knee joint exoskeleton.

[0094] The core of the stiffness adjustment mechanism lies in the dynamic meshing and disengagement process between the first rack 53, the second rack 54, the second gear 56, and the fourth gear 58. The first rack 53 and the second rack 54 are arranged side by side. The second gear 56 meshes with the first rack 53 and the second rack 54 on the corresponding side. The fourth gear 58 meshes with the first rack 53 and the second rack 54 on the corresponding side. The support phase at the beginning of the gait requires high knee joint stiffness to maintain stability. At this time, the first curved beam 5C and the second curved beam 5D closely mesh with the first rack 53 and the second rack 54 to provide solid support to meet the stiffness requirements of the support phase during the gait cycle. When entering the swing phase, the knee joint stiffness requirement decreases. Since the upper ends of the teeth of the first rack 53 and the second rack 54 are aligned, and the length of the tooth of the first rack 53 is shorter than that of the second rack 54, the meshing stroke of the first rack 53 and the second gear 56 is intentionally shortened. At this time, the first rack 53, the second gear 56, and the fourth gear 58 gradually separate, and the second curved beam 5D alone undertakes the auxiliary task to meet the stiffness requirements of the swing phase in the gait cycle. At the end of the swing phase, the traction of the lower leg movement causes the first rack 53 to re-mesh with the second gear 56 and the fourth gear 58. The first curved beam 5C regains its stiffness support and, together with the second curved beam 5D, completes the support task. Therefore, it can be seen that the knee joint assistive exoskeleton of this application adjusts the relative positions of the second gear 56, the fourth gear 58, the first rack 53, and the second rack 54, and the first rack 53 and the second rack 54 reciprocate relative to the outer shell 51 to change the actual stiffness of the knee joint assistive exoskeleton, provide dynamic adjustment and support of stiffness, complete the corresponding auxiliary tasks, achieve precise matching of knee joint movement characteristics and stiffness requirements, improve the adaptability, use effect and user comfort of the knee joint assistive exoskeleton, reduce user fatigue and improve exercise efficiency.

[0095] To reduce the inertial torque generated during thigh swing and alleviate fatigue caused by the shift in the center of gravity of the knee-assisted exoskeleton, the assist mechanism 5 is designed to be located close to the hip joint. The motor 52 is separately fixed to the thigh clamp mechanism 1. Its structurally separate, non-integrated design from the assist mechanism 5 helps to mitigate the transmission of vibration from the motor 52, optimizes vibration isolation performance, reduces potential interference caused by vibration, and ensures the reliability and long-term performance of the assist mechanism 5 and other components.

[0096] Compared to single-elastic-element mechanisms, the knee-assisted exoskeleton proposed in this application embodiment has significant advantages in terms of functional realization and performance. The introduction of multiple elastic elements not only provides more precise and controllable stiffness changes but also enables more compliant assistance that better meets the dynamic needs of the human body through a multi-level adjustment mechanism, improving wear comfort and human-computer interaction. However, this design typically requires more complex mechanisms and control strategies to ensure precise control of the elastic element movement. The variable stiffness assist mechanism 5 proposed in this application embodiment improves the flexibility and adaptability of the device while optimizing the complexity and weight of the mechanism. By designing the first curved beam 5C and the second curved beam 5D to bear the role of the elastic elements, the load-bearing capacity of the knee-assisted exoskeleton is strengthened. The stiffness adjustment of the knee-assisted exoskeleton is achieved by manipulating the first rack 53 and the second rack 54, optimizing the complexity of the assist mechanism 5. The variable stiffness mechanism in this application embodiment has a simple structure, few moving parts, and high reliability, effectively reducing the probability of failure and improving device stability. During the operation of the knee-assisted exoskeleton, the rotational motion of the motor 52 can be efficiently and smoothly converted into linear motion. By precisely controlling the motor 52 and gears, the key displacement variables during stiffness adjustment can be accurately adjusted, thereby providing users with auxiliary force output that meets real-time needs. The variable stiffness structure has a lower coefficient of friction and energy loss, which can effectively reduce the wear rate of the mechanism and improve the working efficiency and overall service life of the mechanical knee joint assistive exoskeleton.

[0097] Traditional crank-slider mechanisms drive a connecting rod through crank rotation, causing the slider to reciprocate along a straight line, thus achieving motion conversion. However, in the knee-assisted exoskeleton of this application embodiment, the motion of the first rack 53 (slider) relative to the outer shell 51 is used to drive the first curved beam 5C, thereby changing the stiffness of the first curved beam 5C. The motion of the second rack 54 (slider) relative to the outer shell 51 is used to drive the second curved beam 5D, thereby changing the stiffness of the second curved beam 5D. The motion of the first gear 55, the second gear 56, the third gear 57, the fourth gear 58, the first rack 53, the second rack 54, the first curved beam 5C, and the second curved beam 5D can be regarded as a "reverse bias crank-slider" mechanism. The linear motion of the first rack 53 and the second rack 54 (slider) is the input, used to drive the first curved beam 5C and the second curved beam 5D, and thus drive the exoskeleton joint. This directly transmits the efficient linear drive power to the first curved beam 5C and the second curved beam 5D, which require complex movements, avoiding the intermediate conversion links that may exist in the traditional method of using a rotary motor 52 to drive the crank, thus improving energy transfer efficiency and response speed. Linear motion is easier to measure accurately (e.g., using a linear displacement sensor) and control than rotational motion. The structural characteristics of the reverse bias crank-slider mechanism enable it to achieve the complex angular changes and stiffness characteristics required by the knee joint throughout the gait cycle. This mechanism can effectively convert the force / displacement input from the linear actuator into a varying torque output at the joint (stiffness is essentially the relationship between torque and angular displacement), meeting the differentiated needs for assist characteristics at different stages of gait (e.g., high stiffness and stability are required during the support phase, and low stiffness and flexibility are required during the swing phase). The "bias" design can typically optimize the force transmission characteristics or spatial layout of the mechanism. By combining the design of the first curved beam 5C and the second curved beam 5D, this mechanism makes it easier to place the motor 52 in non-joint parts of the exoskeleton, such as the thigh, which helps to reduce the inertia and volume of the joints and improve wearing comfort and movement flexibility.

[0098] Furthermore, such as Figure 4As shown, the plantar pressure sensor 6 includes a flexible substrate layer, a pressure-sensitive layer, pressure sensing units 61, a conductive circuit layer, and a protective encapsulation layer. The flexible substrate layer is made of polyester film with a highly conductive metal foil covering its surface. The pressure-sensitive layer, disposed above the flexible substrate layer, is made of a nanoscale pressure-sensitive composite material, including conductive fillers and an elastic polymer matrix, whose resistance changes non-linearly with pressure. Three pressure sensing units 61 are respectively located in the first metatarsal region, the fourth metatarsal region, and the calcaneus region of the human foot. Each pressure sensing unit 61 has an isolation trench formed on the pressure-sensitive layer through an etching process to limit its sensing range. All units are electrically connected to the development board 7 for real-time monitoring of plantar pressure distribution data and sending the data to the development board 7 for gait analysis. The conductive circuit layer includes an independent signal transmission path corresponding to each pressure sensing unit 61. The common ground terminal of each path is located at the rear end of the flexible substrate layer, and the signal output terminals are located at the edges of each pressure sensing unit 61. The protective encapsulation layer covers the pressure-sensitive layer and the conductive circuit layer, and its surface has a curved shape adapted to the anatomical structure of the sole of the foot.

[0099] The plantar pressure sensor 6 in this embodiment is a flexible thin-film pressure sensor with excellent mechanical properties. The wearer's sole contacts the curved protective encapsulation layer, with the curvature matching the arch shape, so that the pressure is evenly distributed across the three pressure sensing units 61. The calcaneal region bears the initial impact, the first metatarsal region supports the main weight-bearing in the middle stage, and the fourth metatarsal region maintains the stability of the arch. The pressure is transmitted sequentially through the elastic protective encapsulation layer, the pressure-sensitive layer, and the flexible base layer, avoiding local stress concentration. The plantar sensor features high sensitivity, fast response, and miniaturization. It can accurately capture minute changes in plantar pressure during gait, providing key data support for gait cycle segmentation and motion state recognition. The plantar sensor has three independent pressure sensing units 61, corresponding to key pressure points such as the first metatarsal region, the fourth metatarsal region, and the calcaneal region, respectively. Compared to multiple individual plantar sensors configured in series, the integrated design in this embodiment can collect pressure data more accurately, improve the synchronization and real-time nature of gait information, and reduce the complexity of the knee-assisted exoskeleton. Existing individual plantar sensors use a series connection, which increases wiring complexity and may affect data consistency due to differences in response time. The integrated plantar pressure sensor 6 in this application has a compact structure and is easy to install, which effectively reduces external interference, improves measurement accuracy, and enhances the reliability of the knee joint assistive exoskeleton while ensuring signal transmission stability.

[0100] Furthermore, the first connecting rod 59, the second connecting rod 5A, the third connecting rod 5B, the first curved beam 5C, and the second curved beam 5D are all integrally formed by 3D printing of polylactic acid (PLA) material.

[0101] Polylactic acid (PLA) is lightweight, possesses excellent mechanical properties, and exhibits superior processing adaptability. It can effectively reduce the weight of knee-supporting exoskeletons, alleviating the burden on wearers and improving comfort and exercise efficiency. When meeting structural strength requirements, its high tensile and yield strength ensure the normal functioning of the knee-supporting exoskeleton. PLA has excellent molding properties, supporting the rapid manufacturing of complex structures, accelerating the experimental process, and reducing costs. Furthermore, its biodegradable properties align with green and sustainable development principles, making it suitable for human-computer interaction products such as rehabilitation equipment. PLA's low cost offers high cost-effectiveness and application value.

[0102] 3D printing technology has the ability to rapidly manufacture complex structures, making the design iteration of knee exoskeleton prototypes more flexible. It also avoids the structural optimization challenges caused by limitations in processing technology inherent in traditional manufacturing methods. 3D printing materials, while lightweight, possess excellent strength properties, effectively reducing the overall weight of the knee-supporting exoskeleton and alleviating the wearer's burden. Compared to traditional metal processing, 3D printing achieves high-precision integrated molding, reducing assembly errors and improving the overall fit of the prototype and the repeatability of experiments. Other structural components in the embodiments of this application can also be manufactured using 3D printing, thereby ensuring that lightweight and structurally optimized designs can be achieved.

[0103] Optional, such as Figure 5 As shown, the assist mechanism 5 also includes a limiter 5E, which is provided above the upper ends of the teeth of the first rack 53 and the second rack 54. The limiter 5E is set at the critical value of the safe range of motion of the upper ends of the teeth of the first rack 53 and the second rack 54 to prevent further slippage, thereby avoiding reverse flexion of the knee joint. This can further prevent secondary injuries in case of accidents.

[0104] Because the angle parameters of the knee-assisted exoskeleton change continuously across different phases, the rate at which the curved beams provide stiffness to the joint differs between the support and swing phases. The first curved beam 5C has a stiffness ratio of 5:1 between the support and swing phases; and / or, the second curved beam 5D also has a stiffness ratio of 5:1 between the support and swing phases. The support phase (i.e., the weight-bearing phase) requires high stiffness to support body weight and movement impacts, which can be achieved through a 5:1 stiffness ratio for stable support. The swing phase (i.e., leg swing dynamics) reduces stiffness, decreases movement resistance, avoids hindering natural knee flexion and extension, and improves the wearer's gait coordination and energy efficiency. This 5:1 stiffness difference matches the biomechanical characteristics of the human knee joint across different phases, optimizing the synergy between the assisted exoskeleton and human kinematics.

[0105] The knee joint assistive exoskeleton provided in this application embodiment also includes a method for optimizing the structural dimensions of the knee joint assistive exoskeleton, comprising the following steps:

[0106] Step A: Gait information acquisition experiment: Select healthy subjects to stand at the starting position and walk in a straight line in a natural state under the operator's instructions. At the same time, use motion capture knee joint-assisted exoskeleton to collect the subject's gait data in real time. The gait data includes at least one of the following: three-dimensional coordinate information of the subject's lower limb joints, joint angle changes, displacement and speed.

[0107] In step A, motion capture includes any one of magnetic motion capture, mechanical motion capture, inertial motion capture, acoustic motion capture, and optical motion capture.

[0108] In step A, the real-time acquisition of the subject's gait data includes:

[0109] Step A1: Collect valid data from 10 groups of subjects walking naturally.

[0110] Step A2: Set a 3-minute rest interval after each set of data collection.

[0111] For example, in the gait information acquisition experiment: Healthy adult males without lower limb joint diseases were selected as subjects. The subjects were 25 years old, 185 cm tall, and weighed 80 kg. First, markers were applied to key areas of the subjects. Then, the subjects underwent adaptation training to familiarize themselves with the use of the exoskeleton and reduce the impact of gait changes caused by initial wear on the experimental data. After the adaptation process, under operator instructions, the subjects walked naturally at a set pace in a straight line. Simultaneously, the motion capture knee-joint assisted exoskeleton was used to collect gait data in real time. Gait data included at least one of the following: three-dimensional coordinates of the lower limb joints, joint angle changes, displacement, and velocity. To ensure data accuracy, 10 sets of valid data from natural walking were collected. A 3-minute rest interval was set after each data set. On the one hand, intermittent rest reduces the impact of muscle fatigue on gait, making the experimental data more representative. On the other hand, the plantar pressure sensor 6 may experience decreased sensitivity or drift after continuous pressure; appropriate intervals can restore the sensor's initial characteristics, maintain the stability of the measurement data, and improve the reliability of the experiment.

[0112] Step B: Experimental data processing: Obtain the raw gait data from Step A, and perform calibration, filtering, trajectory fitting, and joint angle calculation on the data to remove noise, jitter, and data loss;

[0113] In step B, experimental data processing includes performing the following sub-steps using data processing software:

[0114] Data calibration: Aligning the original 3D coordinate information with the coordinate system;

[0115] Data filtering: Applying digital filters to remove high-frequency noise;

[0116] Data trajectory fitting: reconstructing motion trajectories based on smoothed data;

[0117] Data joint angle calculation: Calculate the knee joint angle based on the coordinate changes of lower limb joint marker points.

[0118] The data processing software used was XINGYING software. Joint angle calculations were based on the identification and solution of Mark points attached to the lower limbs. To ensure the validity of the experimental data, five sets of experimental data with stable gait cycles and good data continuity were selected and averaged to reduce the impact of individual gait fluctuations on the results and obtain more representative gait characteristic curves.

[0119] Step C: Gait feature extraction: Based on the data processed in step B, extract a complete gait cycle data and solve for the gait information and the movement distance of the first rack 53 and the second rack 54;

[0120] In step C, solving for gait information includes: based on the processed data, analyzing the relationship between the knee joint angle and the gait cycle, and extracting a reliable complete gait cycle data as the output object.

[0121] Step D: Output optimization parameters: Output the gait information extracted in step C and the motion stroke of the first rack 53 and the second rack 54 as key parameters for optimizing the size of the knee joint-assisted exoskeleton structure.

[0122] Step E: Optimize geometry: Optimize the structural dimensions of the knee joint assist exoskeleton variable stiffness mechanism based on the motion stroke of the first rack 53 and the second rack 54 to achieve precise matching with the wearer's natural gait.

[0123] The knee joint assistive exoskeleton provided in this application embodiment further includes optimizing the geometric parameters of the curved beams (the curved beams include a first curved beam 5C and a second curved beam 5D) using finite element analysis. The geometric parameters include at least the thickness and radius of the curved beams. The optimization aims to provide an average stiffness of 400 N·m / rad during the support phase and 60 N·m / rad during the swing phase, to adapt to human biomechanical characteristics.

[0124] Using the finite element method, this study focuses on the influence of the thickness and radius of a curved beam on its stiffness, deformation, and force response. The thickness and radius of the curved beam are key parameters affecting its stiffness and load-bearing capacity. By adjusting these geometric parameters, the stiffness adjustment performance of the curved beam can be optimized while meeting structural strength requirements. As the design parameters change, the stiffness performance and load-bearing capacity of the curved beam will also vary, directly affecting the support effect of the exoskeleton, as well as the user's wearing comfort and athletic performance.

[0125] ANSYS Workbench can be used as the finite element analysis tool. ANSYS Workbench has powerful nonlinear structural analysis capabilities and can effectively simulate the stress distribution and deformation characteristics of curved beams under different loading conditions, thus providing a theoretical basis for optimizing curved beam design.

[0126] Furthermore, optimizing the geometric parameters of the curved beam using the finite element analysis method includes:

[0127] Define the material properties of the curved beam, including Young's modulus, Poisson's ratio, and density. Ensure the accuracy of material properties during simulation to improve the reliability of simulation results.

[0128] A parametric model is established in the finite element analysis software, and boundary conditions are set: the bottom end of the curved beam is fixed, and a displacement load is applied to the top end.

[0129] Multiple sets of simulation analyses were conducted, with thickness and radius as variables respectively.

[0130] Based on the stiffness calculation formula K=ΔF / Δy, the stiffness values ​​under different geometric parameters are calculated, where ΔF is the force value corresponding to the stress difference obtained from the simulation, and Δy is the displacement difference.

[0131] Based on the stiffness-thickness and stiffness-radius variation trend diagrams obtained from simulation, the optimal combination of thickness and radius is selected.

[0132] Example, Figure 6 This study presents an optimization analysis of the thickness of a curved beam. In this set of simulations, the radius of the curved beam remained constant, and eight different thicknesses were selected as variables to simulate and analyze stiffness, deformation, and stress characteristics. The simulation settings defined the material of the curved beam as PLA, the mesh size as 8mm, and the time step as 1 second. In the constraints, the bottom of the curved beam was designated as a fixed surface, the top as a displacement surface, and a displacement of -30mm was applied in the y-axis direction. Through simulation, the total deformation and force response data under different thickness conditions were obtained.

[0133] After processing the simulation data of the curved beam, a 3D model is created to visually demonstrate its performance. Figure 7 As can be seen, with the increase of the thickness of the curved beam, the deformation gradually decreases, while the stiffness generally increases with the increase of the thickness. Figure 8In the study, the force response of the curved beam was directly proportional to the increase in thickness, with the force value gradually increasing with thickness. These results indicate that increasing the thickness of the curved beam can significantly improve its stiffness and load-bearing capacity, thereby reducing deformation and allowing the curved beam to maintain a more stable shape under external forces. However, increasing the thickness also leads to increased weight, which may affect the flexibility of the exoskeleton and the comfort of the wearer to some extent. To achieve the best design balance, it is necessary to comprehensively consider the relationship between stiffness and weight and optimize the thickness parameters to achieve the optimal performance of the curved beam in walking assistance.

[0134] like Figure 9 As shown, the stiffness of the curved beam gradually increases with the increase of its radius. However, the stiffness begins to decrease when the radius exceeds 350 mm. This indicates that while increasing the radius can improve the stiffness of the curved beam, the stiffness will decrease when the radius is too large. Figure 10 In this study, the force value of a curved beam is directly proportional to the increase in radius, and the force value gradually increases with the increase in radius. This indicates that the load-bearing capacity and response to external loads of a curved beam can be improved by increasing the radius. Therefore, when designing the radius of a curved beam, an appropriate curved beam radius parameter should be selected within the range where stiffness changes linearly to balance the relationship between stiffness and deformation, thereby achieving the best support effect.

[0135] Preferably, curved beam A is 200mm long, has a radius of 256mm, and a thickness of 3.3mm. Curved beam B is 200mm long, has a radius of 200mm, and a thickness of 2mm.

[0136] Optionally, the knee-assisted exoskeleton also includes simulation and experimental verification of the performance of the combined structure of the first curved beam 5C and the second curved beam 5D:

[0137] A model of the combined structure of the first curved beam 5C and the second curved beam 5D placed on top of each other was created in the finite element software, and the same material properties, mesh size and constraints were set.

[0138] By applying displacement loads, the stiffness and stress response of the combined structure of the first curved beam 5C and the second curved beam 5D are obtained through simulation.

[0139] Post-processing analysis was used to verify whether the stiffness superposition of the combined structure of the first curved beam 5C and the second curved beam 5D was linear.

[0140] A 3D-printed curved beam was subjected to static experiments, with vertical displacement applied and force-displacement data recorded.

[0141] By comparing the simulated stiffness ratio, the experimental stiffness ratio, and the target stiffness ratio, the design accuracy and structural effectiveness are verified.

[0142] In practice, the first curved beam 5C and the second curved beam 5D may be superimposed on the same plane. To verify whether the superposition of stiffness and force of the combined structure of the first curved beam 5C and the second curved beam 5D is linear, and to evaluate its performance in practical applications, two curved beams with different thicknesses and radius parameters were selected for analysis. Figure 11 As shown, the simulation settings are as follows: the first curved beam 5C, the second curved beam 5D, the first connecting rod 59, the second connecting rod 5A, and the third connecting rod 5B are all defined as PLA material, the mesh size is set to 8mm, and the time step is set to 1 second. Unlike the simulation of a single curved beam, when constraining the combined structure of the first curved beam 5C and the second curved beam 5D, the fixed surface is the bottom surface of the third connecting rod 5B, the displacement surface is the top surface of the combined structure of the first curved beam 5C and the second curved beam 5D, and then a displacement of -30mm is applied along the y-axis before finally solving.

[0143] Figure 12 and Figure 13 The variation trends of stiffness, force response, and deformation of the combined structure of the first curved beam 5C and the second curved beam 5D are described. The red curve represents the first curved beam 5C, the blue curve represents the second curved beam 5D, the green curve represents the combined structure of the first curved beam 5C and the second curved beam 5D, and the purple dashed line represents the theoretical calculation values ​​of the combined structure of the first curved beam 5C and the second curved beam 5D. It can be seen that the changes in stiffness, deformation, and force response of the combined structure of the first curved beam 5C and the second curved beam 5D are highly consistent with the theoretical calculation values. Simulation results show that the stiffness and force response of the combined structure of the first curved beam 5C and the second curved beam 5D are in high agreement with the theoretical calculation values, indicating that under a reasonable design scheme, the stiffness of the knee exoskeleton can be effectively adjusted through the combination of multiple curved beams, providing a more accurate stiffness matching scheme for the knee joint assist exoskeleton.

[0144] The various embodiments in this specification are described in a progressive manner. For the same or similar parts between the various embodiments, please refer to each other. Each embodiment focuses on describing the differences from other embodiments.

[0145] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of this application.

Claims

1. A knee joint assistive exoskeleton, characterized in that, It includes a thigh clamping mechanism, a calf clamping mechanism, a first inertial measurement sensor, a second inertial measurement sensor, an assist mechanism, a plantar pressure sensor, and a development board; The first inertial measurement sensor is disposed on the thigh clamping mechanism, and the second inertial measurement sensor is disposed on the calf clamping mechanism; The assist mechanism includes a housing, a motor, a first rack, a second rack, a first gear, a second gear, a third gear, a fourth gear, a first connecting rod, a second connecting rod, a third connecting rod, a first curved beam, and a second curved beam; The outer shell is fixed to the thigh clamping mechanism, and the two first racks and the two second racks are slidably disposed on both sides of the outer shell, wherein the length of the teeth of the first racks is less than the length of the teeth of the second racks; The motor is fixed to the housing, the first gear is sleeved on the output shaft of the motor, the second gear meshes with the first gear, the third gear meshes with the first gear, the fourth gear meshes with the third gear, the second gear meshes with the first rack and the second rack on the corresponding side, and the fourth gear meshes with the first rack and the second rack on the corresponding side. The two ends of the first connecting rod are fixed to the lower parts of the two first racks, and the two ends of the second connecting rod are fixed to the lower parts of the two second racks. The first ends of the first curved beam and the second curved beam are respectively sleeved on the first connecting rod and the second connecting rod; The two ends of the third link are fixed to the lower leg clamping mechanism; The second ends of both the first curved beam and the second curved beam are sleeved on the third connecting rod; The plantar pressure sensor is located on the sole of the foot; The first inertial measurement sensor, the second inertial measurement sensor, the motor, and the plantar pressure sensor are all electrically connected to the development board.

2. The knee joint assistive exoskeleton according to claim 1, characterized in that, The plantar pressure sensor includes a flexible substrate layer, a pressure-sensitive layer, a pressure sensing unit, a conductive circuit layer, and a protective encapsulation layer. The flexible substrate layer is made of polyester film and its surface is covered with a highly conductive metal foil; The pressure-sensitive layer is disposed above the flexible substrate layer and is made of a pressure-sensitive composite material, which includes a conductive filler and an elastic polymer matrix, and its resistance value changes non-linearly with pressure. The pressure sensing unit includes three units, which are respectively located in the first metatarsal region, the fourth metatarsal region, and the calcaneal region of the human foot. Each pressure sensing unit forms an isolation groove on the pressure-sensitive layer through an etching process to limit its sensing range. All units are electrically connected to the development board and are used to monitor the plantar pressure distribution data in real time and send the data to the development board for gait analysis. The conductive circuit layer includes an independent signal transmission path corresponding to each pressure sensing unit. The common ground terminal of each path is located at the rear end of the flexible substrate layer, and the signal output terminals are respectively located at the edge of each pressure sensing unit. The protective encapsulation layer covers the pressure-sensitive layer and the conductive circuit layer, and its surface has a curved shape adapted to the anatomical structure of the sole of the foot.

3. The knee joint assistive exoskeleton according to claim 1, characterized in that, The first connecting rod, the second connecting rod, the third connecting rod, the first curved beam, and the second curved beam are all integrally formed by 3D printing of polylactic acid material.

4. The knee joint assistive exoskeleton according to claim 1, characterized in that, The assist mechanism also includes a limiter; A limiter is provided above the upper end of the teeth of both the first rack and the second rack.

5. The knee joint assistive exoskeleton according to claim 1, characterized in that, The stiffness ratio of the first curved beam between the support phase and the swing phase is 5:1; And / or, the stiffness ratio of the second curved beam between the support phase and the swing phase is 5:

1.

6. The knee joint assistive exoskeleton according to claim 1, characterized in that, The geometric parameters of the curved beam are optimized using the finite element method; wherein the geometric parameters include at least the thickness and radius of the curved beam; the optimization objective is to provide an average stiffness of 400 N·m / rad during the support phase and an average stiffness of 60 N·m / rad during the swing phase of the knee exoskeleton.

7. The knee joint assistive exoskeleton according to claim 6, characterized in that, The optimization of the geometric parameters of the curved beam using the finite element analysis method includes: Define the material properties of the curved beam, including Young's modulus, Poisson's ratio, and density; A parametric model is established in the finite element analysis software, and boundary conditions are set: the bottom end of the curved beam is fixed, and a displacement load is applied to the top end; Multiple sets of simulation analyses were conducted, with thickness and radius used as variables respectively. Based on the stiffness calculation formula K=ΔF / Δy, the stiffness values ​​under different geometric parameters are calculated, where ΔF is the force value corresponding to the stress difference obtained from the simulation, and Δy is the displacement difference; Based on the stiffness-thickness and stiffness-radius variation trend diagrams obtained from simulation, the optimal combination of thickness and radius is selected.

8. The knee joint assistive exoskeleton according to claim 1, characterized in that, It also includes simulation and experimental verification of the performance of the combined structure of the first curved beam and the second curved beam: In the finite element software, a model of the combined structure of the first and second curved beams placed on top of each other was created, and the same material properties, mesh size and constraints were set. By applying displacement loads, the stiffness and stress response of the combined structure of the first and second curved beams are obtained through simulation. Post-processing analysis was used to verify whether the stiffness superposition of the combined structure of the first and second curved beams was linear. A 3D-printed curved beam was subjected to static experiments, with vertical displacement applied and force-displacement data recorded. By comparing the simulated stiffness ratio, the experimental stiffness ratio, and the target stiffness ratio, the design accuracy and structural effectiveness are verified.

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