Knee joint power-assisted exoskeleton

Abstract

The invention discloses a knee joint assisting exoskeleton, and belongs to the field of exoskeletons. The first and second inertial measurement sensors are arranged on the thigh and shank clamp mechanisms; a shell of the power assisting mechanism is fixed to the thigh clamp mechanism. A first rack and a second rack are arranged on the two sides of the shell in a sliding mode. The motor is fixedly arranged on the shell and sleeved with the first gear, the second gear and the third gear are meshed with the first gear, the fourth gear and the third gear are meshed, and the second gear and the fourth gear are meshed with the first rack and the second rack on the corresponding side. Two ends of the first and second connecting rods are respectively fixed with the lower parts of the two first and second racks; the first ends of the first and second curved beams are respectively sleeved on the first and second connecting rods; two ends of the third connecting rod are fixed with the shank clamp mechanism; the second ends of the first curved beam and the second curved beam sleeve the third connecting rod; the plantar pressure sensor is arranged on the plantar; the first inertial measurement sensor, the second inertial measurement sensor, the motor and the plantar pressure sensor are electrically connected with the development board. Accurate matching of knee joint motion characteristics and rigidity requirements can be achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of exoskeletons, and in particular to a knee joint assisting exoskeleton. BACKGROUND

[0002] An assisting exoskeleton is a wearable device that enhances human movement ability through mechanical structures, sensors, and driving knee joint assisting exoskeletons, and its joint structure matches the human kinematic structure of the hip, knee, and ankle. With the continuous progress of assisting exoskeleton technology, as a device that provides motion assistance for the human body, the assisting exoskeleton is gradually applied to spinal cord injury patients, stroke rehabilitation and aging assistance, walking, weight bearing and other dynamic motion scenarios.

[0003] The knee joint, as a key component of the human movement system and a key pivot of the lower limb movement of the human body, plays an irreplaceable role in supporting body weight and ensuring movement function. Due to its complex structure and functional requirements, the knee joint is prone to injury and degeneration, affecting daily life and movement ability. Thanks to the continuous progress of science and technology, wearable knee joint exoskeletons have rapidly developed in the fields of rehabilitation medicine, muscle strength enhancement, and metabolic reduction, providing new treatment and assistance means for people. The assisting requirements of the knee joint not only include torque support, but also involve precise matching of the stiffness of the knee joint under different motion modes.

[0004] However, the existing knee joint assisting exoskeletons generally adopt a fixed stiffness design, which can meet the basic assisting requirements, but due to the lack of flexible response to dynamic motion characteristics, they cannot be dynamically adjusted according to different motion requirements and individual differences of the wearer, and cannot achieve precise matching of the motion characteristics and stiffness requirements of the knee joint, limiting their adaptability and use effect, and the comfort of the user is poor. Especially in complex motion modes, fixed stiffness exoskeletons are difficult to provide optimal assisting effect, which may lead to increased fatigue and reduced motion efficiency of the user. SUMMARY

[0005] The present application provides a knee joint assisting exoskeleton, which can solve the problem that the existing knee joint assisting exoskeleton cannot achieve precise matching of the motion characteristics and stiffness requirements of the knee joint, limiting its adaptability, use effect, and comfort of the user, which may lead to increased fatigue and reduced motion efficiency of the user.

[0006] To achieve the above purpose, the technical scheme of the embodiment of the present application is:

[0007] The embodiment of the present application provides a knee joint assisting exoskeleton, which comprises a thigh clamp mechanism, a calf clamp mechanism, a first inertial measurement sensor, a second inertial measurement sensor, an assisting mechanism, a plantar pressure sensor and a development board.

[0008] The first inertia measurement sensor is arranged on the thigh clamp mechanism, and the second inertia measurement sensor is arranged on the shank clamp mechanism;

[0009] The assisting mechanism comprises a housing, a motor, first racks, second racks, a first gear, a second gear, a third gear, a fourth gear, first connecting rods, second connecting rods, a third connecting rod, a first curved beam and a second curved beam;

[0010] The housing is fixed to the thigh clamp mechanism, and the two first racks and the two second racks are slidingly arranged on the two sides of the housing, and the length of the tooth part of the first rack is less than the length of the tooth part of the second rack;

[0011] The motor is fixed to the housing, the first gear is sleeved on the output shaft of the motor, the second gear is engaged with the first gear, the third gear is engaged with the first gear, the fourth gear is engaged with the third gear, the second gear is engaged with the first rack and the second rack on the corresponding side, and the fourth gear is engaged 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 sleeved on the first connecting rod and the second connecting rod respectively;

[0014] The two ends of the third connecting rod are fixed to the shank clamp mechanism;

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

[0016] The plantar pressure sensor is arranged on the sole;

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

[0018] In a possible implementation, the plantar pressure sensor comprises a flexible base layer, a pressure-sensitive layer, a pressure sensing unit, a conductive circuit layer and a protective packaging layer;

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

[0020] The pressure-sensitive layer is arranged above the flexible base layer and is made of a pressure-sensitive composite material, the pressure-sensitive composite material comprises conductive fillers and an elastic polymer matrix, and the resistance value thereof changes nonlinearly with pressure;

[0021] The pressure sensing unit includes three, which are respectively arranged in the first metatarsal area, the fourth metatarsal area and the calcaneal area of the human foot bottom, each pressure sensing unit forms an isolation groove on the pressure sensitive layer through an etching process to define its sensing range, and is electrically connected with the development board, used for monitoring the foot bottom pressure distribution data in real time and sending 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, and the common ground end of each path is located at the rear end of the flexible substrate layer, and the signal output end is separately arranged at the edge of each pressure sensing unit.

[0023] The protective packaging layer covers the pressure sensitive layer and the conductive circuit layer, and the surface is in a curved shape suitable for the foot bottom anatomical structure.

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

[0025] In a possible implementation, the power assisting mechanism further includes a position limiter.

[0026] A position limiter is arranged above the upper end of the tooth part of the first rack and the second rack.

[0027] In a possible implementation, the rigidity ratio of the first curved beam between the support phase and the swing phase is 5:1.

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

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

[0030] In a possible implementation, the optimization of the geometric parameters of the curved beam by the finite element analysis method includes:

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

[0032] Establishing a parameterized model in a finite element analysis software and setting boundary conditions: fixing the bottom end of the curved beam and applying displacement load at the top end;

[0033] Respectively taking thickness and radius as variables to perform a plurality of simulation analyses;

[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 joint assisting exoskeleton provided by the embodiment of the application is used in practice, the thigh clamp mechanism is worn on the thigh, the lower leg clamp mechanism is worn on the lower leg, the first inertia measurement sensor is arranged on the thigh clamp mechanism, the second inertia measurement sensor is arranged on the lower leg clamp mechanism, and the foot bottom pressure sensor is arranged on the foot bottom. The first inertia measurement sensor, the second inertia measurement sensor, the motor and the foot bottom pressure sensor are electrically connected with the development board. The first inertia measurement sensor and the second inertia measurement sensor measure the knee joint angle change data and transmit the data to the development board, and the foot bottom pressure sensor measures the foot bottom pressure distribution data and transmits the data to the development board. The development board receives the data and sends an execution instruction to the motor, the motor is started, the first gear is sleeved on the output shaft of the motor, and the output shaft of the motor drives the first gear to rotate in a predetermined direction. The second gear and the third gear are engaged with the first gear, and the first gear drives the second gear and the third gear to rotate synchronously. The fourth gear is engaged with the third gear, and the third gear drives the fourth gear to rotate in opposite directions. The second gear is engaged with the first rack and the second rack on the corresponding side, and the fourth gear is engaged with the first rack and the second rack on the corresponding side. The first rack and the second rack move relative to the tooth parts of the second gear and the fourth gear, the two first racks and the two second racks are slidably arranged on the two sides of the shell, and then the two first racks and the two second racks slide along the shell stably. 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 sleeved on the first connecting rod and the second connecting rod respectively. The two ends of the third connecting rod are fixed to the lower leg clamp mechanism. The second ends of the first curved beam and the second curved beam are sleeved on the third connecting rod, the movement of the first rack independently drives the movement of the first curved beam, the movement of the second rack independently drives the movement of the second curved beam, power is further transmitted to the lower leg clamp mechanism, and the assisting target of the knee joint exoskeleton is achieved.

[0044] The core of the stiffness adjusting mechanism is the dynamic meshing and disengaging process between the first rack, the second rack and the second gear and the fourth gear. The first rack and the second rack are arranged side by side, the second gear meshes with the first rack and the second rack on the corresponding side, the fourth gear meshes with the first rack and the second rack on the corresponding side, and the support phase at the beginning of the gait requires high knee stiffness to maintain the stability of standing, at this time, the first curved beam and the second curved beam are closely meshed with the first rack and the second rack, providing firm support to adapt to the stiffness requirement of the support phase in the gait cycle. When entering the swing phase, the stiffness requirement of the knee is weakened, because the upper end of the tooth part of the first rack and the second rack is aligned, the length of the tooth part of the first rack is smaller than that of the second rack, so the meshing stroke of the first rack and the second gear is deliberately shortened, at this time, the first rack and the second gear and the fourth gear gradually disengage, and the second curved beam alone undertakes the auxiliary task to adapt to the stiffness requirement of the swing phase in the gait cycle. When entering the swing end, the first rack is re-engaged with the second gear and the fourth gear under the traction of the lower leg movement, the first curved beam re-recovers the stiffness support, and the second curved beam completes the support task together. Therefore, the knee assisting exoskeleton of the embodiment of the present application can change the actual stiffness of the knee assisting exoskeleton by adjusting the relative position of the second gear, the fourth gear and the first rack and the second rack, and the first rack and the second rack reciprocate relative to the shell, to provide dynamic adjustment and support of the stiffness, complete the corresponding auxiliary task, and accurately match the motion characteristics and stiffness requirement of the knee, thereby improving the adaptability, use effect and comfort of the user of the knee assisting exoskeleton, reducing the fatigue of the user and improving the motion efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0045] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the description of the embodiments of the present application will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0046] Figure 1 Structure diagram of the knee assisting exoskeleton provided by the embodiment of the present application Figure 1

[0047] Figure 2 Structure diagram of the knee assisting exoskeleton provided by the embodiment of the present application Figure 2

[0048] Figure 3 The electrical connection diagram of the knee assisting exoskeleton provided by the embodiment of the present application

[0049] Figure 4 Structure diagram of the plantar pressure sensor provided by the embodiment of the present application​​

[0050] Figure 5 Structure diagram of the knee joint assisting exoskeleton provided by the embodiment of the present application Figure 3 ;

[0051] Figure 6 Simulation diagram of the first curved beam provided by the embodiment of the present application

[0052] Figure 7 Stiffness-displacement three-dimensional diagram of the first curved beam under different thickness conditions provided by the embodiment of the present application

[0053] Figure 8 Force-displacement three-dimensional diagram of the first curved beam under different thickness conditions provided by the embodiment of the present application

[0054] Figure 9 Stiffness-displacement three-dimensional diagram of the first curved beam under different radius conditions provided by the embodiment of the present application

[0055] Figure 10 Force-displacement three-dimensional diagram of the first curved beam under different radius conditions provided by the embodiment of the present application

[0056] Figure 11 Simulation diagram of the combined structure of the first curved beam and the second curved beam provided by the embodiment of the present application

[0057] Figure 12 Stiffness-displacement change diagram of the first curved beam, the second curved beam, the combined structure of the first curved beam and the second curved beam, and the theoretical value provided by the embodiment of the present application

[0058] Figure 13 Force-displacement change diagram of the first curved beam, the second curved beam, the combined structure of the first curved beam and the second curved beam, and the theoretical value provided by the embodiment of the present application

[0059] Fig. 1 is a thigh clamp mechanism; 11 is a thigh clamp; 12 is a first binding belt; 13 is a second binding belt; 14 is a first fixing frame; 2 is a calf clamp mechanism; 21 is a calf clamp; 22 is a third binding belt; 23 is a fourth binding belt; 24 is a second fixing frame; 3 is a first inertial measurement sensor; 4 is a second inertial measurement sensor; 5 is an assisting mechanism; 51 is a shell; 52 is a motor; 53 is a first rack; 54 is a second rack; 55 is a first gear; 56 is a second gear; 57 is a third gear; 58 is a fourth gear; 59 is a first connecting rod; 5A is a second connecting rod; 5B is a third connecting rod; 5C is a first curved beam; 5D is a second curved beam; 5E is a position limiter; 6 is a plantar pressure sensor; 61 is a pressure sensing unit; 7 is a development board; 8 is a power supply. DETAILED DESCRIPTION

[0060] With reference to the accompanying drawings, the technical solutions in the embodiments of the present application will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of the present application.

[0061] In the description of the embodiments of the present application, it should be noted that the terms “center”, “upper”, “lower”, “left”, “right”, “vertical”, “horizontal”, “inner”, “outer” and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. The terms “first”, “second”, “third” are only for the purpose of description, and cannot be understood as indicating or implying relative importance. In addition, the terms “mounting”, “connecting”, “connecting” should be understood broadly, for example, it can be fixedly connected, or detachably connected, or integrally connected; it can be mechanically connected, or electrically connected; it can be directly connected, or indirectly connected through an intermediate medium, or the communication between two elements inside. For a person of ordinary skill in the art, the specific meaning of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0062] Please refer to Figure 1 and Figure 2 The embodiment of the present application provides a knee joint assisting exoskeleton, which comprises a thigh clamp mechanism 1, a lower leg clamp mechanism 2, a first inertial measurement sensor 3, a second inertial measurement sensor 4, an assisting mechanism 5, a plantar pressure sensor 6 and a development board 7.

[0063] As shown in Figure 1 , the thigh clamp mechanism 1 is used to be worn on the human thigh. The thigh clamp mechanism 1 comprises a thigh clamp 11, a first binding belt 12, a second binding belt 13 and a first fixing frame 14. The inner wall shape of the thigh clamp 11 is matched with the shape of the thigh. The two ends of the first binding belt 12 are connected to the two ends of the top of the thigh clamp 11. The two ends of the second binding belt 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 used to wear on the lower leg of the human body, and the calf clamp mechanism 2 includes a calf clamp 21, a third binding belt 22, a fourth binding belt 23, and a second fixing frame 24. The inner wall of the calf clamp 21 is shaped to match the shape of the calf. The two ends of the third binding belt 22 are connected to the two ends of the top of the calf clamp 21. The two ends of the fourth binding belt 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] In order to improve the wearing comfort of the knee joint assisting exoskeleton, the thigh clamp 11 and the calf clamp 21 adopt a semi-enclosed design with different radii, and holes are made in the positions of the thigh clamp 11 close to the thigh muscles and the calf clamp 21 close to the calf muscles. Not only can it reduce the pressure of the knee joint assisting exoskeleton on the muscles and provide a certain space for the muscles to move, but also meets the lightweight goal of the knee joint assisting exoskeleton. Because the anatomical structure of the thigh and the calf is a non-regular cylindrical shape with a wide top and a narrow bottom, the inner wall of the thigh clamp 11 and the calf clamp 21 adopts a tapered design to better fit the leg contour, thereby improving the comfort and mechanical stability of wearing. For example, the length of the thigh clamp 11 is 180mm, the inner radius of the top end is 86mm, and the inner radius of the bottom end is 72mm.

[0066] The first binding belt 12, the second binding belt 13, the third binding belt 22, and the fourth binding belt 23 are 50mm wide Velcro belts, which are used in cooperation with the thigh clamp 11 and the calf clamp 21 to realize the fixed connection of the knee joint assisting exoskeleton with the lower limbs.

[0067] The first inertial measurement sensor 3 is arranged on the thigh clamp mechanism 1, and the second inertial measurement sensor 4 is arranged on the calf clamp mechanism 2. When the human body is upright, the first inertial measurement sensor 3 and the second inertial measurement sensor 4 are parallel to the coronal plane of the human body. Specifically, as shown in Figure 1 The first inertial measurement sensor 3 is fixedly arranged on the middle part of the second binding belt 13, and the second inertial measurement sensor 4 is fixedly arranged on the middle part of the fourth binding belt 23. The coronal plane is a vertical plane that divides the human body into front and back parts. The inertial measurement sensor is abbreviated as IMU in English.

[0068] As shown in Figure 1 and Figure 2 The assisting 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 shell 51 is fixed with the thigh clamp mechanism 1, and specifically, the shell 51 is fixed with the first support of the thigh clamp mechanism 1 away from the side of the thigh clamp 11. Two first racks 53 and two second racks 54 are slidingly arranged on the two sides of the shell 51. Specifically, guide grooves are arranged on the two sides of the shell 51, and guide rails are arranged on the outer sides of the first racks 53 and the second racks 54, and the guide rails are slidingly arranged in the guide grooves, so that the two first racks 53 and the two second racks 54 are slidingly arranged on the two sides of the shell 51. The first rack 53 and the second rack 54 on the same side are arranged side by side. The upper ends of the tooth parts of the first rack 53 and the second rack 54 are aligned, and the length of the tooth part of the first rack 53 is less than the length of the tooth part of the second rack 54.

[0070] The motor 52 is fixedly arranged in the shell 51. In order to realize the auxiliary effect of the knee joint assisting exoskeleton in the complex gait mode, accurate motion control and fast response are very important. After comprehensively considering the high requirements of the knee joint assisting exoskeleton on power control, precision and reliability, the motor 52 uses a sigma servo motor (SG-6010H).

[0071] The sigma servo motor adopts a high-performance permanent magnet synchronous motor and a precise feedback control knee joint assisting exoskeleton. In terms of structure, it has high rigidity and low mechanical wear, can effectively reduce the error and delay in dynamic response, and the built-in high-resolution encoder can provide accurate real-time position feedback, ensuring that the motor 52 can maintain high control precision and stability during rapid start, stop and speed change. Moreover, the low inertia design of the motor 52 allows it to have a faster response speed when changing gait, which is particularly suitable for knee joint assisting exoskeletons with complex gait changes.

[0072] The first gear 55 is sleeved on the output shaft of the motor 52, the second gear 56 is engaged 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 is engaged 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 is engaged 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 is engaged with the first rack 53 and the second rack 54 on the corresponding side, and the fourth gear 58 is engaged 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 sleeved on the first connecting rod 59 and the second connecting rod 5A respectively. The two ends of the third connecting rod 5B are fixed to the calf clamp mechanism 2. Specifically, the two ends of the third connecting rod 5B are fixed to the top of the second bracket of the calf clamp mechanism 2. The second ends of the first curved beam 5C and the second curved beam 5D are sleeved on the third connecting rod 5B, so that the calf clamp mechanism 2 is connected to the first curved beam 5C and the second curved beam 5D, and then the control strategy of the power assisting mechanism 5 drives the curved beams to drive the calf to bend and stretch. The lengths of the first connecting rod 59, the second connecting rod 5A and the third connecting rod 5B are all 90 mm, and the diameters are all 6 mm.

[0074] The knee joint is the main load area of the human body in movement and is subjected to pressure and bending. The knee joint power assisting exoskeleton in the embodiment of the application moves the power assisting mechanism 5 out of the lateral region of the knee joint, thereby not only reducing the load of the knee joint power assisting exoskeleton on the knee joint, but also ensuring the natural movement range of the knee joint, and striving to provide non-interfering assistance in dynamic movement.

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

[0076] The foot pressure sensor 6 (English abbreviation: FSR) is arranged on the foot bottom. The first inertial measurement sensor 3, the second inertial measurement sensor 4, the motor 52 and the foot pressure sensor 6 are all electrically connected to the development board 7.

[0077] The natural movement of the knee joint includes bending, stretching, rotating and many other complex actions. The knee joint power assisting exoskeleton needs to consider the bending angle range, bending and stretching rate and rotating angle of the knee joint, so as to ensure that the knee joint power assisting exoskeleton can provide adaptive assistance in different movement stages and prevent the natural movement of the wearer from being limited. The first inertial measurement sensor 3 and the second inertial measurement sensor 4 are mainly used for monitoring the movement state and attitude change of the lower limbs in gait information collection, can collect the knee joint angle change data (angular velocity, acceleration and spatial position data) in real time, and have high sensitivity and accuracy. The ability of the first inertial measurement sensor 3 and the second inertial measurement sensor 4 to independently measure the movement state does not depend on external reference. Even in complex environmental conditions, the first inertial measurement sensor 3 and the second inertial measurement sensor 4 can still work stably, and provide dynamic and real-time data support for the power assisting strategy of the knee joint exoskeleton. The miniaturization and high integration of the IMU 600 enable it to be well adapted to the knee joint power assisting exoskeleton, and the low power consumption characteristic ensures the long-term stable operation of the knee joint power assisting exoskeleton.

[0078] Unlike the common gait collection knee joint assisted exoskeleton, the knee joint assisted exoskeleton of the embodiment of the application adopts double inertial measurement sensors of the first inertial measurement sensor 3 and the second inertial measurement sensor 4. By installing the first inertial measurement sensor 3 and the second inertial measurement sensor 4 at the front positions of the middle sections of the thigh and the lower leg respectively and at the same side, when the human body is upright, the first inertial measurement sensor 3 and the second inertial measurement sensor 4 keep parallel with the coronal plane, the included angle of the Z axes of the first inertial measurement sensor 3 and the second inertial measurement sensor 4 is defined as the knee joint angle monitored by the knee joint assisted exoskeleton, and the angular velocity, acceleration and attitude change of the two positions are monitored. This configuration can not only comprehensively reflect the dynamic change of the knee joint in the movement process, but also accurately identify the support period and the swing period in the gait cycle. Compared with the single inertial measurement sensor which can only collect local motion data, the double inertial measurement sensors can more clearly judge the current motion state of the user by monitoring the relative motion relationship between the thigh and the lower leg, 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, and the Z axes of the first inertial measurement sensor 3 and the second inertial measurement sensor 4 should be aligned to ensure the accuracy of gait information collection.

[0079] The first inertial measurement sensor 3 and the second inertial measurement sensor 4 carry a Bluetooth module, which can be matched and connected with the HC-05 Bluetooth module, and transmit data to the development board 7 in the form of Bluetooth communication. The built-in accelerometer and gyroscope can collect the acceleration and angular velocity of the wearer's leg, and provide accurate motion data for the knee joint assisted exoskeleton through real-time feedback to support the identification and analysis of gait.

[0080] The combination of the first inertial measurement sensor 3 and the second inertial measurement sensor 4 not only realizes comprehensive monitoring of the plantar pressure distribution and the lower limb motion state, but also provides multi-dimensional data support for the intelligent control of the knee joint assisted exoskeleton, which helps to improve the overall performance of the knee joint assisted exoskeleton and the user experience. A gait information collection platform is built by using the first inertial measurement sensor 3, the second inertial measurement sensor 4 and the plantar pressure sensor 6, and data visualization is realized through VOFA+, which provides support for gait feature extraction and motion state recognition.

[0081] The plantar pressure sensor 6 is installed at the position of the wearer's foot bottom, and 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] The foot pressure sensor 6 collects foot pressure distribution data, the first inertial measurement sensor 3 and the second inertial measurement sensor 4 measure three-dimensional angle data (X-axis, Y-axis and Z-axis) of the knee joint, and the kinematic parameters in the gait process are collected synchronously, so as to comprehensively capture the gait characteristics and provide reliable data support for gait recognition and control logic. It can make more accurate adjustment and adaptation in complex motion environment, and ensure that the exoskeleton knee joint assist exoskeleton provides the best support. At the same time, based on the VOFA+ data visualization tool, the knee joint assist exoskeleton can display the collected multi-dimensional data in real time, and intuitively present the dynamic changes of gait characteristics, thereby laying a foundation for subsequent gait analysis and application research. The inertial sensor and the foot pressure sensor 6 are independent in principle and measure based on different physical quantities, so that when one of them fails or has an error, the other can still provide effective data support, thereby enhancing the robustness of the whole knee joint assist exoskeleton.

[0083] In order to ensure the integrity of the gait cycle and the stable operation of the knee joint assist exoskeleton, the foot pressure sensor 6 is used to control the knee joint assist exoskeleton as the trigger condition for switching the gait cycle. When the signals of the two foot pressure sensors 6 both become 0g and the data of the first inertial measurement sensor 3 and the second inertial measurement sensor 4 meet the swing phase characteristics, the exoskeleton knee joint assist exoskeleton triggers the reset logic immediately, so that the motor 52 returns to the initial position and is ready to meet the new gait cycle. Through this mechanism, the exoskeleton can adjust the state in time during the gait conversion process, ensure the continuity of the assist mode, and effectively reduce the occurrence of false triggering.

[0084] In order to improve the stability of the knee joint assist exoskeleton and the use experience, the control strategy considers real-time and adaptability in design, uses the angle change amount of the first inertial measurement sensor 3 and the second inertial measurement sensor 4 to drive the gait, and the knee joint assist exoskeleton can adjust according to the real-time motion state of the wearer, prevent gait deviation caused by lag, and reduce the overcompensation phenomenon caused by large angle error, so as to improve the naturalness and fluency of motion control. The control strategy is based on gait triggering, and the motor 52 operates only when necessary, avoiding unnecessary continuous output, reducing the energy consumption of the knee joint assist exoskeleton, improving the endurance of the exoskeleton device, and making it more suitable for long-term wearing. During the gait conversion process, the foot pressure sensor 6, the first inertial measurement sensor 3 and the second inertial measurement sensor 4 are jointly triggered, the knee joint assist exoskeleton can accurately judge the gait change, ensure resetting and adjusting at the appropriate time, reduce the control abnormality caused by data drift or small amplitude misoperation, and improve the stability of gait switching.

[0085] The development board 7 can be an STM32F103RCT6 microcontroller, which combines DMA and IDLE interrupts to efficiently receive serial port data and ADC data, reducing the need for frequent CPU involvement. Whenever DMA receives data, or after UART / ADC completes data conversion, the IDLE interrupt triggers the relevant callback function by detecting the bus idle state. The callback function distinguishes between different peripherals through DMA handles and processes data frames according to the length of the received data. In the callback function, the parsed attitude data is saved to the corresponding global variable. At the same time, in order to avoid additional interrupts, the DMA half-transmission interrupt is turned off. Then, the DMA reception is restarted, waiting for new data. The STM32F103RCT6 microcontroller can process data transmitted by sensors in real time and execute corresponding control instructions. During the operation of the knee joint assist 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 and process data input from multiple sensors. Through data interaction with different types of sensors, the STM32F103RCT6 can obtain real-time gait information, plantar pressure distribution, angle change, and other motion parameters, providing real-time basis for dynamic adjustment of the knee joint assist exoskeleton. This real-time data processing capability enables the exoskeleton to quickly respond to the wearer's motion needs, providing a more smooth experience for the wearer. The development board 7 can also be an STM32 development board 7.

[0086] The exoskeleton can simulate the movement of the knee joint while also sensing the knee joint angle, speed, and mechanical state in real time, automatically adjusting the output. With integrated sensors and feedback mechanisms, the knee joint assist exoskeleton of the present application can adaptively adjust in a dynamic environment, providing appropriate support for the wearer and ensuring optimal assistance effect at different gait and motion stages.

[0087] As Figure 3As shown, the knee assist exoskeleton also includes a power supply 8. The power supply 8 is electrically connected with the plantar pressure sensor 6, the development board 7, the motor 52, the first inertia measurement sensor 3 and the second inertia measurement sensor 4 to provide them with electric energy. In the power supply 8 selection of the knee assist exoskeleton, two different power supply schemes are adopted to meet the power supply 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 Graupner Ace 6S model airplane battery (22.2V) as the driving power supply. The portable power bank can provide a stable 5V voltage output, which meets the working voltage requirement of the development board 7, and has multiple protection mechanisms built-in, such as overcharge, overdischarge, short circuit protection, etc., which can effectively reduce the risk of power supply 8 management and improve the stability of the knee assist exoskeleton. In addition, the portable power bank is small in size and light in weight, which can meet the portability requirements of wearable devices and support long-time operation without the need for additional design of complex power management circuit.

[0088] The Graupner Ace 6S model airplane battery provides high voltage (22.2V) and large current output, which can meet the driving requirements of the motor 52. Its high energy density ensures that the knee assist exoskeleton has good lightweight characteristics while ensuring endurance. The Graupner Ace 6S model airplane battery has low internal resistance and high discharge rate, which enables the motor 52 to quickly respond to control instructions, improves real-time control accuracy within the gait cycle, and reduces power output delay or out-of-step phenomenon caused by power supply fluctuations. In addition, the stable discharge characteristics of the model airplane battery help to ensure that the knee assist exoskeleton can continuously provide sufficient driving force during high dynamic gait changes without affecting the assist effect due to voltage drop.

[0089] The adoption of the dual power supply scheme physically isolates the power supply of the development board 7 and the motor 52, improving the safety and stability of the knee assist exoskeleton. If only the Graupner Ace 6S model airplane battery is used for power supply, a step-down module is needed to reduce the voltage to 5V to meet the working requirements of the development board 7. However, due to the high voltage characteristics of the model airplane battery, the step-down module may have problems such as current impact or large ripple, which can easily cause damage to the development board 7, thereby affecting the overall stability of the knee assist exoskeleton. Through the independent power supply scheme, not only can the circuit safety problem caused by high voltage step-down be avoided, but also the influence of electromagnetic interference on controlling the knee assist exoskeleton can be reduced, ensuring that the knee assist exoskeleton has higher reliability and durability in complex gait control process.

[0090] In the control of the knee joint assist exoskeleton, the CAN bus (Controller Area Network Bus) is widely used in the communication between the development board 7 and the motor 52 to ensure the real-time transmission of control commands and the efficient collection of motor 52 state data. The CAN bus has high anti-interference, real-time and fault tolerance, and is suitable for use in motion control scenarios that require precise synchronization. In the knee joint assist exoskeleton of the embodiment of the present application, the CAN bus is mainly used to transmit the motor 52 target position control signal generated by the development board 7 to the motor driver, while receiving the motor 52 position feedback (joint angle and running state data), supporting the realization of the gait tracking control strategy.

[0091] In the knee joint assist exoskeleton of the embodiment of the present application, a CAN module is added based on the development board 7 for communication configuration with the motor 52. The initialization and communication management of the CAN protocol is completed through the MX_CAN_Init function. By reasonably 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 index to study the characteristics of human walking. The gait cycle is generally divided into two parts: support phase and swing phase. Taking the right foot as an example, the support phase is the stage when the right foot is always on the ground, accounting for 60% of the entire gait cycle. The swing phase is the stage from the right foot lifting to landing again, accounting for 40% of the entire gait cycle. The right foot just lands from the right foot, which is the beginning of a gait cycle. At this time, the right heel lands, the left toe lands, and the double-leg support state is formed. Then the right foot gradually lands completely, and the left toe is about to completely lift, which is the double-leg support stage in the support phase, accounting for 10% of the entire gait cycle. The main support foot changes from the left foot to the right foot, and the body center of gravity shifts to the right. Then the left toe leaves the ground, and the left leg starts to swing forward. The weight of the entire body is borne by the right foot. When the left leg swings forward beyond the right leg, the body center of gravity gradually moves forward, and the right heel starts to lift to maintain the balance of the entire body. Until the left heel is about to land, this stage is the right leg support, accounting for 40% of the entire gait cycle, which is the only stage of single right leg support in the gait cycle. From the beginning of the left heel contacting the ground to the complete landing of the left foot, and from the beginning of the right heel leaving the ground to the complete lifting of the right toe, this stage is the second double-leg support stage. The difference between the first and second double-leg support stages is that the main support foot changes from the right foot to the left foot, and the body center of gravity shifts to the left foot. This stage accounts for 10% of the entire gait cycle. The left foot lands completely, and the right toe lifts completely, entering the swing phase. At this time, the right foot lifts and swings forward, and the weight of the body is borne by the left foot. When the right leg swings forward beyond the left leg, the left heel starts to lift to maintain the balance of the body. The body center of gravity moves forward until the right heel lands again. This stage accounts for 40% of the entire gait cycle. Thus, the human body has completed a complete gait cycle. During the entire cycle, the left and right feet alternate landing to support the body, the body center of gravity changes constantly, the main support foot changes constantly, and the gait cycle is repeated to make the body walk in a certain direction.

[0093] The knee joint assisting exoskeleton provided by the embodiment of the application is used in practice, the thigh clamp mechanism 1 is worn on the thigh, the lower leg clamp mechanism 2 is worn on the lower leg, the first inertial measurement sensor 3 is arranged on the thigh clamp mechanism 1, the second inertial measurement sensor 4 is arranged on the lower leg clamp mechanism 2, and the foot bottom pressure sensor 6 is arranged on the foot bottom. The first inertial measurement sensor 3, the second inertial measurement sensor 4, the motor 52 and the foot bottom pressure sensor 6 are electrically connected with the development board 7. The first inertial measurement sensor 3 and the second inertial measurement sensor 4 measure the knee joint angle change data and transmit the data to the development board 7, and the foot bottom pressure sensor 6 measures the foot bottom pressure distribution data and transmits the data to the development board 7. The development board 7 receives the data and sends an execution instruction to the motor 52, the motor 52 is started, the first gear 55 is sleeved on 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 are engaged with the first gear 55, the first gear 55 drives the second gear 56 and the third gear 57 to rotate synchronously. The fourth gear 58 is engaged with the third gear 57, and the third gear 57 drives the fourth gear 58 to rotate in opposite directions. The second gear 56 is engaged with the first rack 53 and the second rack 54 on the corresponding side, and the fourth gear 58 is engaged 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 tooth portions of the second gear 56 and the fourth gear 58, the two first racks 53 and the two second racks 54 are slidingly arranged on the two sides of the shell 51, and then the two first racks 53 and the two second racks 54 stably slide along the shell 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 sleeved on the first connecting rod 59 and the second connecting rod 5A respectively. 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 sleeved on the third connecting rod 5B, the movement of the first rack 53 independently drives the movement of the first curved beam 5C, the movement of the second rack 54 independently drives the movement of the second curved beam 5D, and then the power is transmitted to the lower leg clamp mechanism 2, so that the assisting target of the knee joint exoskeleton is achieved.

[0094] The core of the stiffness adjustment mechanism is the dynamic engagement and disengagement process between the first rack 53, the second rack 54 and the second gear 56, the fourth gear 58. The first rack 53 and the second rack 54 are arranged side by side, the second gear 56 is engaged with the corresponding side first rack 53 and second rack 54, the fourth gear 58 is engaged with the corresponding side first rack 53 and second rack 54. The support phase at the beginning of the gait requires high knee stiffness to maintain the stability of standing, at this time the first curved beam 5C and the second curved beam 5D are closely engaged with the first rack 53 and the second rack 54, providing firm support to meet the stiffness requirement of the support phase in the gait cycle. When entering the swing phase, the knee stiffness requirement is weakened, because the upper end of the tooth part of the first rack 53 and the second rack 54 is aligned, the length of the tooth part of the first rack 53 is less than the length of the tooth part of the second rack 54, so the engagement stroke of the first rack 53 and the second gear 56 is deliberately shortened, at this time the first rack 53 and the second gear 56, the fourth gear 58 gradually disengage, the second curved beam 5D alone undertakes the auxiliary task to meet the stiffness requirement of the swing phase in the gait cycle. When entering the swing end, the first rack 53 is re-engaged with the second gear 56 and the fourth gear 58 under the traction of the lower leg movement, the first curved beam 5C renews the stiffness support and the second curved beam 5D completes the support task together. As can be seen, the knee joint assisted exoskeleton of the embodiment of the application changes the actual stiffness of the knee joint assisted exoskeleton by adjusting the relative position of the second gear 56, the fourth gear 58 and the first rack 53, the second rack 54, the first rack 53 and the second rack 54 reciprocate relative to the shell 51, to provide dynamic adjustment and support of stiffness, complete the corresponding auxiliary task, and realize precise matching of the knee joint motion characteristics and stiffness requirement, improve the adaptability, use effect and user comfort of the knee joint assisted exoskeleton, reduce the fatigue of the user and improve the motion efficiency.

[0095] In order to reduce the inertia moment generated when the thigh swings, reduce the fatigue caused by the gravity center offset of the knee joint assisted exoskeleton, the assisting mechanism 5 is designed near the hip joint. The motor 52 is fixed on the thigh clamp mechanism 1 alone, and the non-integrated design of the motor 52 and the assisting mechanism 5 in structure helps to slow down the transmission of motor 52 vibration, optimizes the vibration isolation performance, reduces the potential interference caused by vibration, and provides protection for the reliability and long-term performance of the assisting mechanism 5 and other components.

[0096] Compared with the single elastic element mechanism, the structure of the knee joint assisting exoskeleton provided by the embodiment of the application has significant advantages in function implementation and performance. The introduction of multiple elastic elements can not only provide more precise and controllable stiffness changes, but also can realize more compliant assistance that meets the dynamic needs of the human body through a multi-stage adjustment mechanism, thereby improving the wearing comfort and human-computer interaction effect. However, this design usually requires more complex mechanisms and control strategies to ensure precise control of the movement of the elastic element. The variable stiffness assisting mechanism 5 provided by the embodiment of the application optimizes the complexity and weight of the mechanism while improving the flexibility and adaptability of the device. By designing the first curved beam 5C and the second curved beam 5D to bear the role of the elastic element, the load bearing degree of the knee joint assisting exoskeleton is strengthened. The stiffness adjustment of the knee joint assisting exoskeleton is realized by controlling the first rack 53 and the second rack 54, thereby optimizing the complexity of the assisting mechanism 5. The variable stiffness mechanism in the embodiment of the application has simple structure, few moving parts, high reliability, can effectively reduce the failure probability and improve the stability of the device. During the operation of the knee joint assisting exoskeleton, the rotary motion of the motor 52 can be efficiently and smoothly converted into linear motion. By precisely controlling the motor 52 and the gear, precise adjustment of the key displacement variable during stiffness adjustment can be realized, thereby providing the user with an assistance force output that meets the real-time needs. The variable stiffness structure has a lower friction coefficient and energy loss, which can effectively reduce the wear speed of the mechanism and improve the working efficiency and overall service life of the mechanical knee joint assisting exoskeleton.

[0097] The traditional crank-slider mechanism drives the connecting rod by the rotation of the crank, and makes the slider move along a straight line reciprocatingly, so as to realize the motion conversion. However, in the knee joint assisting exoskeleton in the embodiments of the present application, the movement of the first rack 53 (slider) relative to the shell 51 is used to drive the first curved beam 5C to move, thereby changing the rigidity of the first curved beam 5C. The movement of the second rack 54 (slider) relative to the shell 51 is used to drive the second curved beam 5D to move, thereby changing the rigidity of the second curved beam 5D. The movements 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 kind of "reverse bias crank-slider" mechanism. The linear motion of the first rack 53 and the second rack 54 (slider) is the input, which is used to drive the first curved beam 5C and the second curved beam 5D to move, thereby driving the exoskeleton joint. The high-efficiency linear driving power is directly transmitted to the first curved beam 5C and the second curved beam 5D which need complex motion, avoiding the intermediate conversion link that may exist in the traditional way that the rotary motor 52 drives the crank, and improving the energy transmission efficiency and response speed. Linear motion is easier to measure and control than rotary motion (such as using a linear displacement sensor). The structural characteristics of the reverse bias crank-slider mechanism enable it to realize the complex angle change and rigidity characteristics required by the knee joint in the whole gait cycle. The mechanism can effectively convert the force / displacement input from the linear driver into a variable torque output at the joint (rigidity is essentially the relationship between torque and angular displacement), meeting the differentiated needs of the assisting characteristics in different stages of gait (such as high rigidity stability in the support stage and low rigidity flexibility in the swing stage). The "bias" design can usually optimize the force transmission characteristics or spatial layout of the mechanism. In combination with the design of the first curved beam 5C and the second curved beam 5D, the mechanism is more convenient to arrange the motor 52 at the non-joint part of the exoskeleton, such as the thigh, which helps to reduce the inertia and volume of the joint part, and improve the wearing comfort and motion flexibility.

[0098] Further, as Figure 4As shown, the plantar pressure sensor 6 includes a flexible base layer, a pressure-sensitive layer, a pressure sensing unit 61, a conductive circuit layer, and a protective packaging layer. The flexible base layer is made of a polyester film, and the surface is covered with a highly conductive metal foil. The pressure-sensitive layer is arranged above the flexible base layer and is made of a nano-scale pressure-sensitive composite material. The pressure-sensitive composite material includes conductive fillers and an elastic polymer matrix, and its resistance value changes nonlinearly with pressure. The pressure sensing unit 61 includes three, which are arranged in the first metatarsal area, the fourth metatarsal area and the calcaneal area of the human foot bottom respectively. Each pressure sensing unit 61 forms an isolation groove on the pressure-sensitive layer by etching process to define its sensing range, and is electrically connected with 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, and the common ground of each path is located at the rear end of the flexible base layer, and the signal output end is arranged at the edge of each pressure sensing unit 61. The protective packaging layer covers the pressure-sensitive layer and the conductive circuit layer, and the surface is in a curved surface shape matching the foot bottom anatomical structure.

[0099] The plantar pressure sensor 6 of the embodiment of the present application is a flexible thin film pressure sensor with excellent mechanical properties. The wearer's foot bottom contacts the curved protective packaging layer, and the curvature matches the arch shape, so that the pressure is uniformly distributed in the three pressure sensing units 61. The calcaneal area bears the initial ground impact, the first metatarsal area supports the middle period and mainly bears the weight, and the fourth metatarsal area maintains the stability of the arch. The pressure is transmitted through the elastic protective packaging layer, the pressure-sensitive layer and the flexible base layer in stages to avoid local stress concentration. The plantar sensor has high sensitivity, fast response and small size, and it can accurately capture the small plantar pressure changes in the gait process, providing key data support for gait cycle division and motion state recognition. The plantar sensor has three independent pressure sensing units 61 corresponding to the first metatarsal area, the fourth metatarsal area and the calcaneal area, etc. Compared with the case of serial configuration of multiple separate plantar sensors, the integrated design of the embodiment of the present application can be more accurate in collecting pressure data, can improve the synchronicity and real-time of gait information, and can reduce the complexity of the knee joint assisted exoskeleton. The existing separate plantar sensor uses a serial connection method, which increases the complexity of wiring and may affect the consistency of data due to differences in response time. The integrated plantar pressure sensor 6 of the embodiment of the present application has the characteristics of compact structure and easy installation, which can effectively reduce external interference while ensuring stable signal transmission, improve measurement accuracy and reliability of the knee joint assisted exoskeleton.

[0100] Further, 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 integrally formed by 3D printing of polylactic acid material (English abbreviation: PLA).

[0101] Polylactic acid has the characteristics of lightweight, good mechanical properties, excellent processing adaptability, can effectively reduce the weight of the knee joint assist exoskeleton, relieve the burden of the wearer, improve comfort and motion efficiency. When meeting the structural strength requirements, its high tensile strength and yield strength can ensure the normal work of the knee joint assist exoskeleton. Polylactic acid has good forming performance, can support the rapid manufacturing of complex structures, speed up the experimental process and reduce the cost. Moreover, its biodegradable characteristics meet the green and sustainable development concept, are suitable for human-computer interaction products such as rehabilitation equipment, and polylactic acid has low cost, high cost performance and application value.

[0102] The 3D printing technology has the ability to quickly manufacture complex structures, which makes the design iteration of the knee joint exoskeleton experimental prototype more flexible, and can also avoid the structural optimization problem caused by the limitation of the processing technology in the traditional manufacturing method. The 3D printing material has the characteristics of lightweight and good strength performance, and can effectively reduce the overall weight of the knee joint assist exoskeleton and the additional burden of the wearer. Compared with traditional metal processing, 3D printing can achieve high-precision integrated forming, reduce assembly errors, and improve the overall matching degree of the prototype and the repeatability of the experiment. The remaining structural components of the embodiment of the application can also be manufactured by 3D printing, so as to ensure that the lightweight and structural optimization design can be realized.

[0103] Optionally, as shown in Figure 5 The limiters 5E are arranged above the upper ends of the tooth portions of the first rack 53 and the second rack 54. The limiters 5E are arranged at the critical values of the safe motion range of the upper ends of the tooth portions of the first rack 53 and the second rack 54, and are used to prevent continuous sliding, thereby avoiding reverse flexion of the knee joint. In this way, secondary injury in accidental situations can be prevented.

[0104] Since the angle parameters of the knee joint assist exoskeleton are always changing under different gait states, the achievement rate of the first curved beam 5C and the second curved beam 5D for providing stiffness to the joint is different when supporting and swinging. The stiffness ratio of the first curved beam 5C between the support phase and the swing phase is 5:1; and / or, the stiffness ratio of the second curved beam 5D between the support phase and the swing phase is 5:1. The support phase (i.e. the body weight phase) needs to provide high stiffness to bear the body weight and the impact force of movement, and stable support can be achieved through the stiffness ratio of 5:1. The swing phase (i.e. the leg swing state) reduces the stiffness to reduce the movement resistance, avoids hindering the natural flexion and extension of the knee joint, and improves the gait coordination and energy efficiency of the wearer. The stiffness difference of 5:1 matches the biomechanical characteristics of the human knee joint in different gait states, and optimizes the synergy of the assist exoskeleton and the human kinematics.

[0105] The knee joint assist exoskeleton provided by the embodiment of the application further includes an optimization method for the structural size of the knee joint assist exoskeleton, which includes the following steps:

[0106] Step A: Gait information collection experiment: Select a healthy subject to stand at the starting position, and walk along a straight line in a natural state under the instruction of the operator, while using the motion capture knee assist exoskeleton to collect the subject's gait data in real time. The gait data includes at least one of the three-dimensional coordinate information, joint angle change, displacement and speed of the subject's lower limb joints.

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

[0108] In step A, real-time collection of subject gait data includes:

[0109] Step A1: Collect 10 groups of valid data of the subject's natural walking.

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

[0111] For example, the gait information collection experiment: Select a healthy adult male without lower limb joint disease as the subject, aged 25, 185 cm tall, and 80 kg in weight. First, paste Mark points on the key parts of the subject, and then the subject undergoes wearing adaptation training to familiarize with the use of the exoskeleton and reduce the influence of gait change caused by initial wearing on experimental data. After the adaptation process is completed, the subject walks along a straight line in a natural state at a set pace under the instruction of the operator, while using the motion capture knee assist exoskeleton to collect the subject's gait data in real time. The gait data includes at least one of the three-dimensional coordinate information, joint angle change, displacement and speed of the subject's lower limb joints. To ensure the accuracy of the data, 10 groups of valid data of the subject's natural walking are collected. A 3-minute rest interval is set after each group of data collection. On the one hand, intermittent rest can reduce the influence of muscle fatigue on gait, making the experimental data more representative. On the other hand, the sensitivity of the plantar pressure sensor 6 may decrease or drift after continuous force, and appropriate intermittent rest can restore the initial characteristics of the sensor, maintain the stability of the measurement data, and improve the reliability of the experiment.

[0112] Step B: Experimental data processing: Obtain the original gait data in step A, calibrate, filter, trajectory fitting and joint angle calculation of the data to remove noise, jitter and data loss;

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

[0114] Data calibration: Align the coordinate system for the original three-dimensional coordinate information;

[0115] Data filtering: Apply a digital filter to remove high-frequency noise;

[0116] Data trajectory fitting: reconstruct the motion trajectory based on the smoothed data;

[0117] Data joint angle calculation: calculate the knee joint angle according to the coordinate change of the lower limb joint marker point.

[0118] The data processing software is XINGYING software, and the joint angle calculation is based on the recognition and solution of the Mark points pasted on the lower limbs. In order to ensure the effectiveness of the experimental data, five groups of experimental data with stable gait cycle and good data continuity are selected, and the average processing is carried out, so as to reduce the influence of individual gait fluctuation on the results and obtain more representative gait characteristic curves.

[0119] Step C: gait feature extraction: based on the data processed in step B, a complete gait cycle data is extracted, and the gait information and the motion stroke of the first rack 53 and the second rack 54 are solved;

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

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

[0122] Step E: optimize the geometric size: based on the motion stroke of the first rack 53 and the second rack 54, the structure size of the knee joint assisted exoskeleton variable stiffness mechanism is optimized, so as to realize the accurate matching of the natural gait of the wearer.

[0123] The knee joint assisted exoskeleton provided by the embodiment of the application also includes optimizing the geometric parameters of the curved beam (the curved beam includes the first curved beam 5C and the second curved beam 5D) through the finite element analysis method. The geometric parameters at least include the thickness and the radius of the curved beam. The optimization target is to make the knee joint exoskeleton 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, so as to adapt to the biomechanical characteristics of the human body.

[0124] By using the finite element analysis method, the influence of the thickness and the radius of the curved beam on the stiffness, deformation and force reaction is emphatically studied. The thickness and the radius of the curved beam are key parameters affecting the stiffness and load capacity of the curved beam. By adjusting these geometric parameters, the stiffness adjustment performance of the curved beam can be optimized under the premise of meeting the structural strength requirement. With the change of the design parameters, the stiffness performance and the load capacity of the curved beam will also be different, which is directly related to the support effect of the exoskeleton, and the wearing comfort and the motion performance of the user.

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

[0126] Further, the geometric parameters of the curved beam are optimized by the finite element analysis method, including:

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

[0128] Establish a parametric model in the finite element analysis software and set the boundary conditions: fix the bottom end of the curved beam and apply a displacement load at the top end.

[0129] Perform multiple simulation analyses with thickness and radius as variables.

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

[0131] Based on the stiffness-thickness and stiffness-radius trend relationship diagrams obtained by simulation, select the optimal thickness and radius combination.

[0132] The example, Figure 6 represents the thickness optimization analysis of the curved beam. In this simulation, the radius of the curved beam remains the same, and eight different thicknesses are selected as variables for stiffness, deformation and stress characteristics simulation analysis. The simulation is set to define the material of the curved beam as PLA, the mesh is set to 8mm, and the time step is set to 1 second. In the constraint condition, the bottom of the curved beam is set as a fixed surface, and the top end is set as a displacement surface, and a displacement of -30mm is applied in the y-axis direction. Through simulation solving, the total deformation and force reaction data under different thickness conditions are obtained.

[0133] After processing the simulation data of the curved beam, perform three-dimensional graph drawing to visually display the performance of the curved beam. From Figure 7 it can be seen that as the thickness of the curved beam increases, the deformation gradually decreases, and the stiffness generally increases with the increase of the thickness. In Figure 8In the simulation, the force response of the curved beam is proportional to the increase in thickness, and the force value gradually increases with the increase in thickness. These results show that increasing the thickness of the curved beam can significantly improve its stiffness and carrying capacity, thereby reducing deformation and allowing the curved beam to maintain a more stable form when subjected to external forces. However, the increase in thickness will also result in an increase in weight, which will affect the flexibility of the exoskeleton and the comfort of the wearer to some extent. In order to achieve the best design balance, the relationship between stiffness and weight needs to be considered comprehensively, and the thickness parameter needs to be optimized to achieve the optimal performance of the curved beam in walking assistance.

[0134] As shown in Figure 9 , with the increase in the radius of the curved beam, the stiffness also gradually increases. However, when the radius exceeds 350 mm, the stiffness begins to decrease. This indicates that although increasing the radius can improve the stiffness of the curved beam, when the radius is too large, the stiffness will decrease. In Figure 10 , the force value of the curved beam is proportional to the increase in radius, and the force value gradually increases with the increase in radius, indicating that the carrying capacity and response ability to external load of the curved beam can be improved by increasing the radius. Therefore, when designing the radius of the curved beam, a suitable curved beam radius parameter should be selected in the interval where the stiffness changes linearly to balance the relationship between stiffness and deformation, thereby achieving the best support effect.

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

[0136] Optionally, the knee joint assistance exoskeleton further includes simulating and experimentally verifying 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 is established in the finite element software, and the same material properties, mesh size, and constraint conditions are set.

[0138] A displacement load is applied, and 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] The post-processing analysis verifies whether the stiffness of the combined structure of the first curved beam 5C and the second curved beam 5D is linearly superimposed.

[0140] A 3D printed physical curved beam is subjected to a statics experiment, a vertical displacement is applied, and force-displacement data is recorded.

[0141] The simulation stiffness ratio, experimental stiffness ratio, and target stiffness ratio are compared to verify the design accuracy and structural effectiveness.

[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-assist exoskeleton, characterized by, The thigh clamp mechanism, the calf clamp mechanism, the first inertial measurement sensor, the second inertial measurement sensor, the power assisting mechanism, the plantar pressure sensor and the development board are included. The first inertial measurement sensor is arranged on the thigh clamp mechanism, and the second inertial measurement sensor is arranged on the calf clamp mechanism. The power assisting 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 housing is fixed with the thigh clamp mechanism, and two first racks and two second racks are slidingly arranged on both sides of the housing. The motor is fixed on the housing, the first gear is sleeved on the output shaft of the motor, the second gear is engaged with the first gear, the third gear is engaged with the first gear, the fourth gear is engaged with the third gear, the second gear is engaged with the first rack and the second rack on the corresponding side, and the fourth gear is engaged with the first rack and the second rack on the corresponding side. The two ends of the first connecting rod are fixed with the lower parts of the two first racks, and the two ends of the second connecting rod are fixed with 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 connecting rod are fixed with the calf clamp mechanism. The second ends of the first curved beam and the second curved beam are sleeved on the third connecting rod. The plantar pressure sensor is arranged on the plantar. The first inertial measurement sensor, the second inertial measurement sensor, the motor and the plantar pressure sensor are electrically connected with the development board.

2. The knee assist exoskeleton of claim 1, wherein, The plantar pressure sensor includes a flexible base layer, a pressure-sensitive layer, a pressure sensing unit, a conductive circuit layer and a protective packaging layer. The flexible base layer is made of polyester film, and the surface is covered with high-conductivity metal foil. The pressure-sensitive layer is arranged above the flexible base layer and is made of pressure-sensitive composite material. The pressure sensing unit includes three, which are respectively arranged in the first metatarsal area, the fourth metatarsal area and the calcaneal area of the human foot, each pressure sensing unit forms an isolation groove on the pressure-sensitive layer through etching process to define its sensing range, and is electrically connected with the development board for real-time monitoring of plantar pressure distribution data and sending 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, and the common ground end of each path is located at the rear end of the flexible base layer, and the signal output end is separately arranged at the edge of each pressure sensing unit. The protective packaging layer covers the pressure-sensitive layer and the conductive circuit layer, and the surface is in a curved shape adapted to the anatomical structure of the foot.

3. The knee-power-assisted 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 integrally formed by 3D printing of polylactic acid material.

4. The knee-power-assisted exoskeleton according to claim 1, characterized in that, The power assisting mechanism further includes a position limiter. A limiter is arranged above the upper end of the tooth part of the first rack and the second rack.

5. The knee-power-assisted 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-power-assisted exoskeleton according to claim 1, characterized in that, The geometric parameters of the curved beam are optimized by a finite element analysis method, wherein the geometric parameters at least include the thickness and the radius of the curved beam, and the optimization target is to make the knee exoskeleton 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.

7. The knee-power-assisted exoskeleton according to claim 6, characterized in that The optimization of the geometric parameters of the curved beam by the finite element analysis method comprises: defining the material properties of the curved beam, the material properties including Young's modulus, Poisson's ratio and density; establishing a parameterized model in a finite element analysis software and setting boundary conditions: fixing the bottom end of the curved beam and applying a displacement load at the top end; performing a plurality of simulation analyses with thickness and radius as variables respectively; calculating the stiffness values under different geometric parameters according to the stiffness calculation formula K = ΔF / Δy, wherein ΔF is the force value corresponding to the stress difference obtained by simulation, and Δy is the displacement difference; selecting the optimal thickness and radius combination based on the stiffness-thickness and stiffness-radius trend relationship diagrams obtained by simulation.

8. The knee-power-assisted exoskeleton according to claim 1, characterized in that, It also includes simulation and experimental verification of the performance of the first curved beam and the second curved beam combination structure: a model of the first curved beam and the second curved beam combination structure is established in a finite element software, and the same material properties, mesh size and constraint conditions are set; a displacement load is applied, and the stiffness and stress response of the first curved beam and the second curved beam combination structure are obtained by simulation; whether the stiffness superposition of the first curved beam and the second curved beam combination structure is linear is verified by post-processing analysis; a 3D printed curved beam is used for statics experiment, a vertical displacement is applied, and force-displacement data is recorded; the simulation stiffness ratio, the experimental stiffness ratio and the target stiffness ratio are compared to verify the design accuracy and the structural effectiveness.

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