Stiffness variable ankle prosthesis

Abstract

The application discloses a variable stiffness ankle prosthesis, which comprises a foot plate and a lower leg frame connected in rotation, a first elastic member on the foot plate, a movable plate connected to the foot plate in sliding, one end of the first elastic member being fixed relative to the foot plate and the other end being connected to the movable plate, and a variable stiffness mechanism for adjusting the position of the movable plate. The variable stiffness ankle prosthesis is provided to solve the problem that passive prosthesis is difficult to fully simulate the function of human ankle joint in the prior art, and to achieve the purpose that the ankle prosthesis can change stiffness under different gait cycles.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of medical devices, in particular to a variable stiffness ankle prosthesis. BACKGROUND

[0002] Ankle is an important part of the lower limbs and the most flexible part of the human body. How to improve the bionic performance and more realistically realize the function of the human ankle joint is still a challenge. At present, most ankle prostheses are passive prostheses, which only rely on one or two constant stiffness springs to realize the functions of buffering and assisting. However, the stiffness of the human ankle joint is always changing in a gait cycle, and the stiffness change rule is different in different gait cycles. In the prior art, there is little report on the application of variable stiffness driving in prostheses. SUMMARY

[0003] The present application provides a variable stiffness ankle prosthesis to solve the problem that passive prostheses in the prior art are difficult to fully simulate the function of the human ankle joint, and to achieve the purpose of enabling the ankle prosthesis to change the stiffness in different gait cycles.

[0004] The present application is achieved by the following technical solutions:

[0005] The variable stiffness ankle prosthesis comprises a foot plate and a lower leg frame connected in rotation, a first elastic member located on the foot plate, and a movable plate connected to the foot plate in sliding manner. One end of the first elastic member is fixed relative to the foot plate, and the other end is connected to the movable plate. The variable stiffness mechanism is used to adjust the position of the movable plate.

[0006] In view of the problem that passive artificial limbs in the prior art are difficult to fully simulate the function of human ankle joints, the present application provides a variable stiffness ankle joint prosthesis, a foot plate and a lower leg frame being component parts of the prosthesis and being rotatably connected with each other. The present application is provided with a first elastic member on the foot plate, one end of the first elastic member being fixedly connected with the foot plate and the other end being connected with a movable plate, the movable plate being slidingly fitted on the foot plate. The connection between the first elastic member and the movable plate can be fixed connection or abutting contact connection, as long as the elastic force of the first elastic member can always make the movable plate have a tendency to move away from the fixed end of the first elastic member. The specific sliding position of the movable plate on the foot plate is adjusted by a variable stiffness mechanism, which can temporarily limit the position of the movable plate by any means that can be realized by any person skilled in the art to resist the force applied by the first elastic member to the movable plate. Under the action of the variable stiffness mechanism, the movable plate can be located at different positions, so that the first elastic member is in different degrees of compression state and outputs different forces outward, thereby providing the patient with the relationship between the stiffness and the rotation angle of the ankle joint under different gaits, better simulating and realizing the function of the human ankle joint. When the patient needs to switch different gaits, the position of the movable plate can be adjusted by the variable stiffness mechanism.

[0007] Further, the variable stiffness mechanism includes a cam set composed of a plurality of stiffness cams, the profiles of any two stiffness cams in the cam set being different; the movable plate is located between the cam set and the first elastic member, and further includes an adjusting assembly for contacting the different stiffness cams with the movable plate.

[0008] In the present application, the cam set is used as the component directly contacting the movable plate in the variable stiffness mechanism, and the stiffness change of the ankle joint in the walking period under different gaits can be adapted by different cam profile lines, thereby generating a torque-rotation angle relationship similar to that of the human ankle joint, better restoring the function of the human ankle joint in different periods of the support phase. In addition, the cam set includes a plurality of stiffness cams with different profiles, and different stiffness cams are adapted to different gait conditions, thereby meeting the need of switching different gaits of the present application. Therefore, the structure of the cam set used in the present application can not only realize the walking demand of the present application adapting to different gaits, but also provide different stiffness curves in the corresponding walking period under different gaits, realize stiffness self-adaptation, and provide the patient with the relationship between the stiffness and the rotation angle of the ankle joint under different gaits, better simulating the function of the human ankle joint.

[0009] In the present application, the adjusting assembly can adjust the position of the cam set by any means that can be realized by any person skilled in the art, as long as it can realize the direct or indirect contact between the different stiffness cams and the movable plate.

[0010] Further, the adjusting assembly comprises an adjusting screw rod rotatably connected to the foot plate and / or the lower leg frame, an adjusting nut connected to the adjusting screw rod, and a first driving mechanism for driving the adjusting screw rod to rotate.

[0011] The adjusting assembly in the present scheme adjusts the cam set through a screw rod mechanism. Specifically, the adjusting screw rod is rotatably connected to the foot plate and / or the lower leg frame at both ends, and a first driving mechanism is used to drive the adjusting screw rod to rotate. The adjusting nut is matched with the adjusting screw rod, and the cam set is fixedly connected to the adjusting nut. Due to the limiting of the guide shaft, when the adjusting screw rod rotates, the cam set and the adjusting nut move linearly along the axial direction of the adjusting screw rod, thereby adjusting the position of the cam set and facilitating the contact between the different stiffness cams and the movable plate.

[0012] Further, the foot plate is provided with a sliding rail for the sliding of the movable plate, and the surface of the side of the movable plate facing the direction where the cam set is located is provided with a roller for contacting a stiffness cam. The axis of the roller is perpendicular to the axis of the sliding rail. In the present scheme, the movable plate is slidably connected to the foot plate through the sliding rail. Meanwhile, the roller is arranged on the side of the movable plate away from the first elastic member, and the roller necessarily protrudes out of the surface of the movable plate. Since the axis of the roller is perpendicular to the axis of the sliding rail, the rolling direction of the roller is the same as the axial direction of the sliding rail. By adjusting the overall position of the cam set in the axial direction of the roller, different stiffness cams can be brought into contact with the roller.

[0013] Further, the cam set comprises a flat ground walking cam, a stair climbing gait cam, and a stair descending gait cam.

[0014] Flat ground walking, stair climbing, and stair descending are the three most common and important gait types in daily life. After a large amount of research, the present inventors have obtained the cam profile curves corresponding to the three gait types respectively. When a user needs to switch between different types of gaits, the corresponding cam to be contacted with the movable plate can be switched through the adjusting assembly. The specific cam profiles are as follows.

[0015] The profile curve equation of the flat ground walking cam (10) is:

[0016]

[0017]

[0018]

[0019]

[0020] In the formula, xx c1 is the x coordinate of the actual profile curve equation of the flat ground walking cam, y c1 is the y coordinate of the actual profile curve equation of the flat ground walking cam, δ is the cam rotation angle, x B is the x coordinate of the theoretical profile curve equation of the cam, y B is the y coordinate of the theoretical profile curve equation of the cam, S(δ)1 is the driven motion law of the flat ground walking gait, r r is the roller radius.

[0021] The profile curve equation of the up-stairs walking cam (11) is:

[0022]

[0023]

[0024]

[0025]

[0026] wherein: x c2 is the x coordinate of the actual profile curve equation of the up-stairs walking cam, y c2 is the y coordinate of the actual profile curve equation of the up-stairs walking cam, δ is the cam rotation angle, x B is the x coordinate of the theoretical profile curve equation of the cam, y B is the y coordinate of the theoretical profile curve equation of the cam, S(δ)2 is the driven motion law of the up-stairs walking gait, r r is the roller radius.

[0027] The profile curve equation of the down-stairs walking cam (12) is:

[0028]

[0029]

[0030] wherein: x c3 is the x coordinate of the actual profile curve equation of the down-stairs walking cam, y c3 is the y coordinate of the actual profile curve equation of the down-stairs walking cam, δ is the cam rotation angle, x B is the x coordinate of the theoretical profile curve equation of the cam, y B is the y coordinate of the theoretical profile curve equation of the cam, S(δ)3 is the driven motion law of the down-stairs walking gait, r r is the roller radius.

[0031] It should be noted that the switching of different types of gait can be achieved by the user actively controlling the adjusting assembly, or can be automatically adjusted by the built-in sensors (such as gravity sensors, acceleration sensors, inclination sensors, etc.), and the specific adjusting means are not limited herein.

[0032] Further, a second elastic member is arranged on the foot plate, a lower mounting plate is arranged above the second elastic member, an upper mounting plate is arranged above the lower mounting plate, and a third elastic member is arranged at the bottom of the upper mounting plate; a second driving mechanism is arranged in the calf frame, a driving screw is driven by the second driving mechanism, a driving nut is connected to the driving screw, and a force transmission link is hinged between the driving nut and the lower mounting plate.

[0033] In the scheme, the driving screw is driven to rotate by the second driving mechanism, and under the limiting of the force transmission link, the driving nut moves linearly along the driving screw, thereby driving the lower mounting plate to move up and down, so as to adjust the elastic force of the second elastic member and the third elastic member, and further to assist the user to walk.

[0034] Specifically, when the heel is about to leave the ground, the second driving mechanism drives the driving screw to rotate, so that the driving nut moves upward, and the third elastic member is compressed in the process of upward movement. The elastic potential energy generated by the compression deformation of the third elastic member is released instantaneously, which can effectively compensate the output power of the driving mechanism, so as to provide sufficient instantaneous assist torque to drive the ankle prosthesis, which can better assist the ankle prosthesis to walk, reduce the requirement of the ankle prosthesis for driving power, thereby reducing the energy consumed by the amputee in each gait, and further reducing the output torque of the hip joint on the side of the amputee with the prosthesis, which is beneficial to the amputee to walk stably and naturally. In this process, the second elastic member plays a buffering function when the lower mounting plate is reset, and the upper mounting plate plays a mounting and positioning function for the third elastic member.

[0035] Further, a first guide column is fixed on the foot plate, the first guide column passes through the lower mounting plate and the upper mounting plate, a second guide column is fixed on the bottom surface of the upper mounting plate, a through hole matched with the second guide column is formed in the lower mounting plate, and the third elastic member is sleeved outside the second guide column.

[0036] In the scheme, the first guide column is used for guiding the lower mounting plate to stably realize the up-down movement. The second guide column can be used for more convenient installation of the third elastic member, and the through hole in the lower mounting plate can avoid interference between the second guide column and the lower mounting plate.

[0037] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0038] 1. The present invention provides a variable stiffness ankle joint prosthesis. Under the action of the variable stiffness mechanism, the movable plate can be located in different positions, thereby causing the first elastic element to be under different degrees of compression and output different forces outward. This can provide the patient with the relationship between ankle joint stiffness and rotation angle under different states, better simulating and realizing the function of the human ankle joint. When the patient needs to switch between different states, the axial position of the cam group can be adjusted.

[0039] 2. The variable stiffness ankle joint prosthesis of the present invention uses a cam assembly as the component that directly contacts the moving plate in the variable stiffness mechanism. It can adapt to the stiffness changes of the ankle joint during the walking cycle under different gait states by using different cam profiles, thereby generating a torque-angle relationship that is approximately the same as that of the human ankle joint, and better restoring the function of the human ankle joint in different periods of the support phase.

[0040] 3. The variable stiffness ankle joint prosthesis of the present invention can also provide different stiffness curves corresponding to the walking cycle under different time states, realize stiffness self-adaptation, provide patients with the relationship between ankle joint stiffness and rotation angle under different time states, and better simulate the function of human ankle joint.

[0041] 4. The present invention provides a variable stiffness ankle joint prosthesis, which provides cam profile curves for three gait types: walking on flat ground, climbing stairs, and going down stairs, filling the gap in the prior art.

[0042] 5. The variable stiffness ankle prosthesis of the present invention can provide assistance to the ankle prosthesis with a large instantaneous assist torque, which can better assist the prosthetic foot of the ankle joint to push off the ground and walk, reduce the requirement of the ankle prosthesis for drive power, thereby reducing the energy consumed by the amputee in walking in various gait states, and further reducing the output torque of the hip joint on the side of the amputee, which is conducive to enabling the amputee to maintain a stable and natural walking. Attached Figure Description

[0043] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0044] Figure 1 This is a schematic diagram of a specific embodiment of the present invention;

[0045] Figure 2 This is a schematic diagram of a specific embodiment of the present invention;

[0046] Figure 3 This is a partial structural diagram of a specific embodiment of the present invention;

[0047] Figure 4 This is a partial installation diagram of the movable plate in a specific embodiment of the present invention.

[0048] The attached diagram shows the markings and corresponding component names:

[0049] 1-Foot plate, 2-Lower leg frame, 3-First elastic element, 4-Moving plate, 5-Adjusting screw, 6-Adjusting nut, 7-Guide shaft, 8-Roller, 9-Slide rail, 10-Flat-ground walking cam, 11-Stair-climbing gait cam, 12-Stair-descending gait cam, 13-Second elastic element, 14-Lower mounting plate, 15-Upper mounting plate, 16-Third elastic element, 17-Second drive mechanism, 18-Drive screw, 19-Drive nut, 20-Force transmission link, 21-First guide post, 22-Second guide post, 23-Through hole, 24-Stiffness motor, 25-Synchronous belt transmission assembly, 26-Gear set, 27-Positioning plate. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments and accompanying drawings. The illustrative embodiments and descriptions of this invention are for explaining the invention only and are not intended to limit the invention. In the description of this application, it should be understood that the terms "front," "rear," "left," "right," "upper," "lower," "vertical," "horizontal," "high," "low," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the scope of protection of this application.

[0051] Example 1:

[0052] like Figures 1 to 3 The variable stiffness ankle prosthesis shown includes a foot plate 1 and a lower leg frame 2 rotatably connected. It is characterized by further including a first elastic element 3 located on the foot plate 1 and a movable plate 4 slidably connected to the foot plate 1; one end of the first elastic element 3 is fixed relative to the foot plate 1 and the other end is connected to the movable plate 4; it also includes a variable stiffness mechanism for adjusting the position of the movable plate 4.

[0053] The variable stiffness mechanism includes a cam group consisting of several stiffness cams, wherein any two stiffness cams in the cam group have different profiles; the movable plate 4 is located between the cam group and the first elastic element 3, and also includes an adjustment component for contacting different stiffness cams with the movable plate 4.

[0054] In this embodiment, the first elastic element 3 is a spring that is always in a compressed state, and there are two sets of them. The axis of the first elastic element 3 is along the front-back direction of the foot plate, and the sliding direction of the movable plate 4 is also along the front-back direction of the foot plate.

[0055] In a more preferable embodiment, a positioning plate 27 is fixedly installed on the foot plate 1, and is used to fixedly install the first elastic member 3.

[0056] Embodiment 2:

[0057] A variable stiffness ankle prosthesis, based on the embodiment 1, as shown in Figures 1 to 4

[0058] The adjusting assembly comprises an adjusting screw rod 5 rotatably connected to the foot plate 1 and / or the lower leg frame 2, an adjusting nut 6 connected to the adjusting screw rod 5, and a first driving mechanism used to drive the adjusting screw rod 5 to rotate; the cam assembly is fixedly connected to the adjusting nut 6, and further comprises a guide shaft 7 penetrating through the cam assembly, and the guide shaft 7 is connected to the lower leg frame 2.

[0059] The foot plate 1 is provided with a sliding rail 9 used for sliding of the movable plate 4, and a side surface of the movable plate 4 facing the direction where the cam assembly is located is provided with a roller 8 used for contacting with a stiffness cam; an axis of the roller 8 is perpendicular to an axis of the sliding rail 9.

[0060] The cam assembly comprises a walking on flat ground cam 10, a climbing stairs gait cam 11, and a descending stairs gait cam 12; the climbing stairs gait cam 11 and the descending stairs gait cam 12 are respectively located on two sides of the walking on flat ground cam 10, so as to facilitate switching of gait when the present application is used.

[0061] In the embodiment, the adjusting screw rod 5 has a light rod section at both ends, and the light rod sections at both ends are connected to the foot plate 1 and the lower leg frame 2 through deep groove ball bearings, and can realize rotatable connection between the foot plate and the lower leg frame through the light rod sections.

[0062] In the embodiment, the three cams are movably sleeved outside the adjusting screw rod 5, and the three cams are locked through bolts between the adjusting nut 6.

[0063] In a more preferable embodiment, the first driving mechanism comprises a stiffness motor 24 and a synchronous belt transmission assembly 25, wherein the stiffness motor 24 is installed in the lower leg frame 2, and the synchronous belt transmission assembly 25 is used to connect an output end of the stiffness motor 24 and the adjusting screw rod 5.

[0064] In a more preferable embodiment, the guide shaft 7 is locked on the lower leg frame 2 through threads, or is pinned on the lower leg frame 2 through a pin.

[0065] In a more preferable embodiment, a mounting seat matched with the roller 8 is further included.

[0066] Embodiment 3:

[0067] ​A variable stiffness ankle prosthesis, in this embodiment the profiles of the level walking cam 10, the stair ascent cam 11 and the stair descent cam 12 are defined based on the embodiment 2. In particular:

[0068] The profile curve equation of the level walking cam 10 is:

[0069]

[0070] wherein x c1 is the x coordinate of the actual profile curve equation of the level walking cam, y c1 is the y coordinate of the actual profile curve equation of the level walking cam, δ is the cam rotation angle, x B is the x coordinate of the theoretical profile curve equation of the cam, y B is the y coordinate of the theoretical profile curve equation of the cam, S(δ)1 is the follower motion law of the level walking gait, r r is the roller radius.

[0071] The profile curve equation of the stair ascent cam 11 is:

[0072]

[0073]

[0074]

[0075]

[0076] wherein x c2 is the x coordinate of the actual profile curve equation of the stair ascent cam, y c2 is the y coordinate of the actual profile curve equation of the stair ascent cam, δ is the cam rotation angle, x B is the x coordinate of the theoretical profile curve equation of the cam, y B is the y coordinate of the theoretical profile curve equation of the cam, S(δ)2 is the follower motion law of the stair ascent gait, r r is the roller radius.

[0077] The profile curve equation of the stair descent cam 12 is:

[0078]

[0079]

[0080]

[0081]

[0082] wherein x c3The x-coordinate and y-coordinate of the actual profile curve equation of the gait cam for going downstairs are given. c3 Here is the y-coordinate of the actual profile curve equation of the gait cam for going downstairs, δ is the cam rotation angle, and x is the x-coordinate. B Let x and y be the x-coordinates of the theoretical profile curve equation of the cam. B Let S(δ)3 be the y-coordinate of the theoretical profile curve equation of the cam, and S(δ)3 be the follower motion law of the downhill gait. r Where is the roller radius.

[0083] Example 4:

[0084] A variable stiffness ankle prosthesis, based on any of the above embodiments, such as Figure 2 As shown, it also includes a second elastic element 13 disposed on the foot plate 1, a lower mounting plate 14 located above the second elastic element 13, an upper mounting plate 15 located above the lower mounting plate 14, and a third elastic element 16 disposed at the bottom of the upper mounting plate 15; it also includes a second drive mechanism 17 installed in the lower leg frame 2, an active lead screw 18 driven by the second drive mechanism 17, an active nut 19 connected to the active lead screw 18, and a force transmission link 20 hinged between the active nut 19 and the lower mounting plate 14.

[0085] Preferably, it also includes a first guide post 21 fixed on the foot plate 1, the first guide post 21 movably passing through the lower mounting plate 14 and the upper mounting plate 15; it also includes a second guide post 22 fixed on the bottom surface of the upper mounting plate 15, the lower mounting plate 14 has a through hole 23 that matches the second guide post 22, and the third elastic member 16 is sleeved on the second guide post 22.

[0086] In this embodiment, the second drive mechanism 17 is a drive motor for the ankle prosthesis, which transmits power to the lead screw 18 via a gear set 26. The gear set 26 can function as a speed reduction mechanism as needed.

[0087] In a more preferred embodiment, the top of the first guide post 21 has a threaded section, and the upper mounting plate 15 and the first guide post 21 are fixedly connected by the upper and lower threads that cooperate with the threaded section.

[0088] In a more preferred embodiment, the upper and lower ends of the second guide post 22 are fixedly connected to the upper plate and the lower plate, respectively; the second guide post 22, the upper plate, and the lower plate together form an "I"-shaped structure; the two ends of the third elastic element 16 are respectively installed on the upper plate and the lower plate. The upper plate is welded to the bottom surface of the upper mounting plate, and the lower end of the second guide post 22 passes through the lower plate and is locked to the lower plate with a nut. This preferred embodiment solves the installation problem of the third elastic element during the actual processing of this application.

[0089] During the walking process of the amputee wearing the ankle prosthesis of the present application, one gait cycle of the ankle prosthesis is as follows:

[0090] 1) Before the heel of the foot plate 1 contacts the ground, the ankle is in a natural state.

[0091] 2) After the heel of the foot plate 1 contacts the ground, the initial stage of the support phase of walking is entered, the heel of the foot plate 1 contacts the ground and bears pressure, and the ankle gradually dorsiflexes from the plantar flexion state to the natural state.

[0092] 3) In the middle stage of the support phase of walking, the ankle continues to dorsiflex until the dorsiflexion angle reaches the maximum, and the torque of the ankle also rapidly increases. During this process, the first elastic member 3 on the foot plate is gradually compressed by the cam contour curve corresponding to the specific gait on the stiffness cam, simulating the torque curve of the human ankle at a specific gait, to prepare for the next leg lifting and leaving the ground.

[0093] 4) In the late stage of the support phase of walking, the ankle enters the plantar flexion and leg lifting state. After the foot plate 1 finishes lifting the leg, the first elastic member 3 begins to recover due to the elastic deformation of the stiffness cam contour compression. At this time, under the simultaneous driving action of the two first elastic members 3 and the third elastic member 16, the energy collected and stored in the third elastic member 16 is rapidly released during the plantar flexion and leg lifting, to compensate for the power of the driving motor, so that the driving torque of the ankle increases explosively to the maximum, so as to provide sufficient driving force for the ankle to enable normal walking of the human body until the toes completely leave the ground and the driving torque is released.

[0094] 5) After the foot plate leaves the ground in the plantar flexion state, the third elastic member 16 is compressed because the angle of the ankle is greater than 90 degrees, and the ankle prosthesis enters the swing phase of walking. When the third elastic member releases energy, the ankle is in the maximum plantar flexion state, and the second driving mechanism 17 needs to be used for position control to restore the natural state, to prepare for entering the next gait cycle.

[0095] In summary, the power ankle joint designed according to the present application compresses the first elastic member 3 installed on the foot plate through the stiffness cam with different contour curves in the cam set in the middle stage of the support phase, to generate a torque angle relationship similar to that of the human ankle, to better restore the function of the human ankle in the middle stage of the support phase. When entering the late stage of the support phase, since the foot plate 1 leaves the ground, a driving torque needs to be provided at this moment to realize the process of plantar flexion and leg lifting. The second driving mechanism 17 drives the driving screw rod 18 on the lower leg frame 2 to rotate, and then drives the driving nut 19 to compress the third elastic member 16, and then the third elastic member 16 rapidly releases energy to assist the foot plate of the ankle joint in lifting the leg, to realize the process of lifting the heel of the human ankle from the ground.

[0096] The above detailed description merely describes the specific implementation of the present application, and the purpose, technical solutions and beneficial effects of the present application are further explained. It should be understood that the above description is only a specific implementation of the present application, and is not used to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

[0097] It should be noted that the relational terms herein such as first and second and the like are used solely to distinguish one entity or action from another, without necessarily requiring or implying any such actual relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus. Furthermore, the term "connected" as used herein, without any special indication, can mean either directly connected or indirectly connected via other parts.

Claims

1. A variable stiffness ankle prosthesis, comprising a footplate (1) and a lower leg frame (2) with rotatable connection, characterized in that, It also includes a first elastic element (3) located on the foot plate (1) and a movable plate (4) slidably connected to the foot plate (1); one end of the first elastic element (3) is fixed relative to the foot plate (1) and the other end is connected to the movable plate (4); it also includes a variable stiffness mechanism for adjusting the position of the movable plate (4); The variable stiffness mechanism includes a cam group consisting of several stiffness cams, wherein any two stiffness cams in the cam group have different profiles; the movable plate (4) is located between the cam group and the first elastic element (3), and also includes an adjustment component for making different stiffness cams contact the movable plate (4); The adjustment assembly includes an adjustment screw (5) rotatably connected to the foot plate (1) and / or the calf frame (2), an adjustment nut (6) connected to the adjustment screw (5), and a first drive mechanism for driving the adjustment screw (5) to rotate; the cam group is fixedly connected to the adjustment nut (6), and also includes a guide shaft (7) passing through the cam group, the guide shaft (7) being connected to the calf frame (2); The foot plate (1) is provided with a slide rail (9) for sliding the movable plate (4). The movable plate (4) is provided with a roller (8) on the side surface facing the direction of the cam group. The roller (8) is used to contact a rigid cam. The axis of the roller (8) is perpendicular to the axis of the slide rail (9). The cam assembly includes a flat-ground walking cam (10), a stair-climbing gait cam (11), and a stair-descending gait cam (12).

2. The variable stiffness ankle prosthesis according to claim 1, characterized in that, The contour curve equation of the flat-ground walking cam (10) is as follows: In the formula: x c1 The x-coordinate and y-coordinate of the actual profile curve equation of the cam that travels on flat ground are... c1 Here is the y-coordinate of the actual profile curve equation of the cam that travels on flat ground, δ is the cam rotation angle, and x is the x-coordinate. B Let x and y be the x-coordinates of the theoretical profile curve equation of the cam. B Let S(δ)1 be the y-coordinate of the theoretical profile curve equation of the cam, and S(δ)1 be the follower motion law for walking on flat ground. r Where is the roller radius.

3. The variable stiffness ankle prosthesis according to claim 1, characterized in that, The contour curve equation of the stair-climbing gait cam (11) is as follows: In the formula: x c2 The x-coordinate and y-coordinate of the actual profile curve equation of the stair-climbing gait cam are given. c2 Here, y is the equation of the actual profile curve of the stair-climbing gait cam, δ is the cam rotation angle, and x is the y-coordinate. B Let x and y be the x-coordinates of the theoretical profile curve equation of the cam. B Let S(δ)2 be the y-coordinate of the theoretical profile curve equation of the cam, and S(δ)2 be the follower motion law of the stair-climbing gait. r Where is the roller radius.

4. The variable stiffness ankle prosthesis according to claim 1, characterized in that, The contour curve equation of the downstairs gait cam (12) is: In the formula: x c3 The x-coordinate and y-coordinate of the actual profile curve equation of the gait cam for going downstairs are given. c3 Here is the y-coordinate of the actual profile curve equation of the gait cam for going downstairs, δ is the cam rotation angle, and x is the x-coordinate. B Let x and y be the x-coordinates of the theoretical profile curve equation of the cam. B Let S(δ)3 be the y-coordinate of the theoretical profile curve equation of the cam, and S(δ)3 be the follower motion law of the downhill gait. r Where is the roller radius.

5. The variable stiffness ankle prosthesis according to claim 1, characterized in that, It also includes a second elastic element (13) disposed on the foot plate (1), a lower mounting plate (14) located above the second elastic element (13), an upper mounting plate (15) located above the lower mounting plate (14), and a third elastic element (16) disposed at the bottom of the upper mounting plate (15); it also includes a second drive mechanism (17) installed in the lower leg frame (2), an active lead screw (18) driven by the second drive mechanism (17), an active nut (19) connected to the active lead screw (18), and a force transmission link (20) hinged between the active nut (19) and the lower mounting plate (14).

6. The variable stiffness ankle prosthesis according to claim 5, characterized in that, It also includes a first guide post (21) fixed on the foot plate (1), the first guide post (21) moving through the lower mounting plate (14) and the upper mounting plate (15); it also includes a second guide post (22) fixed on the bottom surface of the upper mounting plate (15), the lower mounting plate (14) having a through hole (23) matching the second guide post (22), and the third elastic member (16) sleeved on the second guide post (22).

Images