CN110353949B

CN110353949B - Active knee and ankle joint artificial limb mechanism based on metamorphic parallel mechanism

Info

Publication number: CN110353949B
Application number: CN201910728366.3A
Authority: CN
Inventors: 宋马军; 郭盛; 王向阳; 陈光荣; 曲海波; 赵福群
Original assignee: Beijing Jiaotong University
Current assignee: Beijing Jiaotong University
Priority date: 2019-08-08
Filing date: 2019-08-08
Publication date: 2020-12-01
Anticipated expiration: 2039-08-08
Also published as: CN110353949A

Abstract

An active knee ankle joint artificial limb mechanism based on metamorphic parallel mechanisms is composed of a fixed platform, an active branched chain, a metamorphic branched chain, a movable platform and an active ankle joint artificial limb mechanism, and the multi-degree-of-freedom motion characteristic of a knee ankle joint is achieved. The driving sliding pair of the driving branched chain in the metamorphic parallel mechanism is provided for the electric push rod, so that not only can the flexion and extension of the knee joint and the eversion and eversion of the ankle joint be realized, but also the extension and retraction movement of the crus skeletal muscle group can be simulated; because the internal and external rotation movement of the knee joint of the human body is activated only when the knee is bent, and the dependence on the internal and external rotation movement in life is less, the metamorphic characteristic of the metamorphic branch chain is adopted, namely when the artificial limb mechanism bends the knee, the metamorphic kinematic pair is changed into a driving revolute pair, the internal and external rotation of the knee joint is activated, and on the contrary, the metamorphic kinematic pair is a fixed pair, and the knee joint does not have the internal and external rotation movement. The artificial limb mechanism relates to a medical rehabilitation robot and has the requirements of high bearing capacity, high rigidity, simple structure, easy processing and manufacturing, low production cost and the like.

Description

Active knee and ankle joint artificial limb mechanism based on metamorphic parallel mechanism

Technical Field

The invention belongs to the field of medical rehabilitation robot technology and artificial intelligence equipment, and particularly relates to an active knee and ankle joint artificial limb mechanism based on a metamorphic parallel mechanism, which can compensate the motion function of a knee and ankle joint lost by a knee and ankle amputation patient, so that the patient can recover the multi-degree-of-freedom motion characteristic and the daily life capability of the knee and ankle joint.

Background

According to the general survey data published in 2006 for the number of the second disabled people in China, the disabled people reach 8242 thousands of people, which accounts for about 6.34% of the total population, meanwhile, the disabled patients reach 2412 thousands of people, and the lower limb amputation patients reach 160 thousands of people. In recent years, with the increase of natural disasters, traffic accidents, diseases, other accidents and other accidents, the number of amputees with different degrees is increased year by year, which not only causes the patients to lose daily life capacity and suffer from delight, but also greatly increases social burden. At present, with the inexhaustible development of scientific technology and industrial manufacturing industry, the robot technology is widely applied to various large-scale engineering fields in China. In order to compensate the lost limb of the amputation patient and enable the patient to recover the original daily living ability, the artificial limb robot belonging to the medical rehabilitation robot becomes one of the hot spots of the domestic research. However, due to the limitations of some technical development and manufacturing process levels, the prosthetic robot still has a great market prospect at home and abroad.

As amputees with a damaged knee ankle account for the largest proportion of lower limb amputees, there are a large number of knee ankle prosthetic devices products on the market. The existing artificial limb mechanism of human joint can be divided into an active artificial limb mechanism, a passive artificial limb mechanism and an active and passive mixed artificial limb mechanism according to whether a power source is provided or not. Compared with foreign artificial limb mechanisms, the research in China starts late, the technology is laggard, and the research and development of the domestic market on the lower artificial limb mechanism belong to a primary stage. At present, the research and development of domestic knee and ankle joint artificial limb mechanisms are improved from the traditional single-degree-of-freedom and single-support-rod structure form to the intelligent multi-degree-of-freedom multi-joint form, however, the artificial limb mechanisms are large in overall size, heavy in weight and poor in bearing capacity due to the fact that a plurality of components are connected in series, the mechanisms are complex, a control algorithm is unstable, the cost of the artificial limb mechanisms is high, and the intelligent artificial limb mechanisms are still not main products in the market.

Based on the metamorphic parallel mechanism, the invention designs an active type knee and ankle joint prosthetic mechanism based on the metamorphic parallel mechanism, and the prosthetic mechanism consists of a small-freedom metamorphic parallel mechanism and a single-freedom-degree rotating active type ankle joint prosthetic mechanism, wherein the small-freedom-degree metamorphic parallel mechanism is formed by configuring a fixed platform, an active branched chain, a metamorphic branched chain and a movable platform. When a fixed pair is arranged in the middle of a metamorphic kinematic pair (the joint of an upper rod and a lower rod) of the metamorphic branch chain, the metamorphic parallel mechanism can only simulate flexion and extension movement of a knee joint and internal and external turning movement of an ankle joint; when the metamorphic kinematic pair of the metamorphic branch chain is a revolute pair, the metamorphic parallel mechanism can also simulate the internal and external rotation movement of the knee joint, and the metamorphic characteristic accords with the movement characteristic that the lower limbs of the human body activate the internal and external rotation of the knee joint only in the knee bending state. In addition, the active ankle joint artificial limb mechanism rotating with single degree of freedom realizes the flexion and extension movement of the ankle joint. The artificial limb mechanism based on the parallel mechanism not only can embody the high rigidity and strong bearing capacity of the mechanism, but also can simplify the whole structure, reduce the whole size and the production cost of the mechanism and the like, and meanwhile, the simplified mechanism also has the advantages of easy control, low energy consumption and the like.

Disclosure of Invention

The invention aims to design an active knee and ankle joint artificial limb mechanism based on a metamorphic parallel mechanism, and the mechanism solves the problems of complex structure, large volume, heavy mass, high energy consumption for movement, high stability, insufficient bearing capacity and the like in the artificial limb mechanism developed previously. The metamorphic parallel mechanism adopted by the mechanism not only can realize the multi-degree-of-freedom motion characteristic of the knee ankle joint, but also has the characteristics of large bearing capacity, low motion energy consumption and the like, so that the knee ankle joint has high bionic characteristic compared with the knee ankle joint of a human body.

The invention is realized by adopting the following technical scheme:

an active knee ankle joint artificial limb mechanism based on metamorphic parallel mechanism is characterized in that: comprises a fixed platform (1), active branched chains (2.1, 2.2), a metamorphic branched chain (3), a movable platform (4) and an active ankle joint prosthesis mechanism (5).

The active branched chains (2.1, 2.2) are designed by taking knee joint flexion and ankle joint eversion of the execution prosthetic mechanism as targets, and comprise: a lower foot seat (2-1), a lower U-shaped seat (2-2), a cylinder (2-3) containing a drive, a piston rod (2-4) containing a drive, a joint (2-5), an upper U-shaped seat (2-6) and an upper foot seat (2-7);

the connection mode among the parts of the active branched chain is as follows: the lower foot seat (2-1) is connected with the fixed platform (1) through a screw to form a fixed pair; the lower foot seat (2-1) and the lower U-shaped seat (2-2) form a revolute pair, the lower U-shaped seat (2-2) and the cylindrical barrel (2-3) containing the drive form a revolute pair, and simultaneously, the two revolute pair axes are orthogonal and equivalent to a hooke pair; a cylinder (2-3) containing a drive and a piston rod (2-4) containing the drive form a drive moving pair, and the drive moving pair is provided by an electric push rod; a piston rod (2-4) containing a drive is connected with a joint (2-5) through threads to form a fixed pair; the joint (2-5) and the upper U-shaped seat (2-6) form a revolute pair, the upper U-shaped seat (2-6) and the upper foot seat (2-7) form a revolute pair, and simultaneously, the two revolute pair axes are orthogonal and equivalent to a hooke pair; the upper foot seats (2-7) and the movable platform (4) are connected into a fixed pair through screws; the active branched chains (2.1, 2.2) imitate the biomechanical characteristics of skeletal muscle groups on the surface of the tibiofibula, and the movable platform (4) can rotate around the movable platform and rotate around the space of the fixed platform by driving the expansion and contraction of the sliding pair so as to simulate the flexion and extension of the knee joint and the eversion of the ankle joint;

the metamorphic branched chain (3) is designed according to the internal and external rotation movement of the knee joint under the condition of executing necessary conditions in a prosthetic mechanism, and comprises the following components: the device comprises a lower foot seat (3-1), a large sleeve (3-2), a rotation angle limiting lower rod (3-3), a cover plate (3-4), a rotation angle limiting upper rod (3-5), a joint (3-6), a small sleeve (3-7) and an upper foot seat (3-8);

connection between parts of metamorphic branch chains: the lower foot seat (3-1) is connected with the fixed platform (1) through a screw to form a fixed pair; the lower foot seat (3-1) and the lower rod (3-3) with limited rotation angle form a rotation pair, and a large sleeve (3-2) is arranged at the gap position; the lower rotation-limiting angle rod (3-3) and the upper rotation-limiting angle rod (3-5) form a metamorphic kinematic pair which has angle limitation and avoids the generation of mechanism singularity caused by transitional rotation; when the knee and ankle joint artificial limb mechanism is in a non-knee bending state, the metamorphic kinematic pair is a fixed pair, and under the coupling constraint of the metamorphic branched chain (3) and the two driving branched chains (2.1 and 2.2), the two pure rotations of the movable platform (4) can simulate the bending and stretching movement of the knee joint and the inward and outward turning movement of the ankle joint of a human body. Although the internal and external rotation movement of the knee joint can be activated only when the lower limbs of the human body bend the knee, and the dependence of the human body movement on the internal and external rotation of the knee joint is small, medical researches show that the movement function of the internal and external rotation of the knee joint plays a certain role in the human body gait symmetry and stability. Therefore, when the knee and ankle joint artificial limb mechanism bends the knee, the metamorphic kinematic pair is changed from a fixed pair to a driving revolute pair with a rotation angle limitation, the metamorphic branched chain (3) is under the coupling constraint of the two driving branched chains (2.1 and 2.2), and the motion of the movable platform (4) is added with a rotational degree of freedom, and the rotational degree of freedom can imitate the internal and external rotation motion of the knee joint of a human body. The cover plate (3-4) penetrates through the rotation angle limiting upper rod (3-5) and is connected with the rotation angle limiting lower rod (3-3) through a screw, and in order to restrict the rotation angle limiting upper rod (3-5) to move along the direction of the branched chain; the rotation-limited angle upper rod (3-5) and the joint (3-6) are connected through threads to form a fixed pair; the joint (3-6) and the upper foot seat (3-8) form a rotating pair, and a small sleeve (3-7) is arranged at a gap position, and the sleeve is used for ensuring good centering performance of the metamorphic branch chain and ensuring flexible rotation of the mechanism;

compared with the prior art, the invention has the following beneficial effects:

the metamorphic parallel mechanism is designed and applied to a metamorphic parallel mechanism in a knee ankle joint artificial limb mechanism, can execute two-degree-of-freedom or three-degree-of-freedom pure rotation of a space, and is used for simulating the multi-degree-of-freedom motion characteristic of the knee ankle joint. When the metamorphic kinematic pair of the metamorphic branch chain is a driving revolute pair, the movable platform of the mechanism can simulate the flexion and extension movement and the internal and external rotation movement of the knee joint of the human body and the internal and external turning movement of the ankle joint. Because the internal and external rotation motions of the human knee joint do not exist all the time, the knee joint is activated only when the knee is bent, in addition, the dependence on the internal and external rotation motions in life is less, and the introduction of the metamorphic branched chain is used for better performing bionic design on the human knee joint by the artificial limb mechanism. When the metamorphic kinematic pair of the metamorphic branch chain is a fixed pair, the movable platform of the mechanism only simulates the flexion and extension movement of the knee joint and the inward and outward turning movement of the ankle joint of a human body. The artificial limb mechanism has simple structure, easy analysis of kinematics and easy processing and manufacturing of the mechanism, and the design of the mechanism can provide important reference for the design of other joint artificial limb mechanisms and even the design of precise mechanisms.

Drawings

FIG. 1 is a structural model diagram of an active knee and ankle joint prosthesis mechanism based on metamorphic parallel mechanisms;

FIG. 2 is a diagram showing a structural model of a metamorphic parallel mechanism with two-degree-of-freedom and three-degree-of-freedom pure rotation modes switched;

FIG. 3 is an exploded view of a structural model of an active branch;

FIG. 4 is an exploded view of a structural model of a metamorphic branch;

in the figure: the artificial limb mechanism comprises a fixed platform (1), active branched chains (2.1, 2.2), a metamorphic branched chain (3), a movable platform (4) and an active ankle joint artificial limb mechanism (5). The active branches (2.1, 2.2) comprise: a lower foot seat (2-1), a lower U-shaped seat (2-2), a cylinder (2-3) containing a drive, a piston rod (2-4) containing a drive, a joint (2-5), an upper U-shaped seat (2-6) and an upper foot seat (2-7); the metamorphic branch (3) comprises: the device comprises a lower foot seat (3-1), a large sleeve (3-2), a rotation angle limiting lower rod (3-3), a cover plate (3-4), a rotation angle limiting upper rod (3-5), a joint (3-6), a small sleeve (3-7) and an upper foot seat (3-8).

Detailed Description

For further understanding of the active knee and ankle joint prosthesis mechanism based on metamorphic parallel mechanism provided by the present invention, the present invention will be specifically explained with reference to the accompanying drawings and detailed embodiments.

Fig. 1 is a structural model diagram of an active knee and ankle joint prosthetic mechanism based on a metamorphic parallel mechanism, and the basic structure of the mechanism comprises a fixed platform (1), active branched chains (2.1 and 2.2), a metamorphic branched chain (3), a movable platform (4) and an active ankle joint prosthetic mechanism (5). The knee and ankle joint artificial limb mechanism can realize the motion functions of flexion and extension of the knee joint of a human body, flexion and extension of the ankle joint, internal and external rotation of the knee joint in the states of internal and external rotation and flexion of the knee joint, and the like, and the application of the metamorphic parallel mechanism can greatly simplify the complex structure of the artificial limb mechanism and reduce the design cost of the artificial limb mechanism.

Fig. 2 is a structural model diagram of a metamorphic parallel mechanism with two-degree-of-freedom and three-degree-of-freedom pure rotation mode switching provided by the invention, and comprises a fixed platform (1), active branched chains (2.1, 2.2), a metamorphic branched chain (3) and a movable platform (4); when a metamorphic kinematic pair of the metamorphic branched chain (3) is a fixed pair, the force output when the electric push rods in the two active branched chains (2.1, 2.2) are driven is the same in magnitude and direction, and the movable platform (4) is driven to rotate around the fixed platform (1) by stretching the piston rods (2-4) containing the drive, namely, the bending and stretching motion of the knee joint of a human body is simulated; the force output by the electric push rods in the two driving branched chains (2.1, 2.2) is the same in magnitude and opposite in direction, and the driving piston rods (2-4) are stretched to cause the movable platform (4) to rotate around the movable platform, namely, the inside and outside turning motion of the ankle joint of a human body is simulated; in this case, the two active branches act as the gastrocnemius and soleus muscles on the posterior surface of the human tibiofibula. Because the internal and external rotation movement of the human knee joint does not exist all the time, the internal and external rotation movement is activated only when the knee is bent, in addition, the dependency on the internal and external rotation movement in life is less, and the artificial limb mechanism can be better designed bionically for the human knee joint by the metamorphic branched chain (3). In addition, when a metamorphic kinematic pair of the metamorphic branch chain (3) is a driving revolute pair, the movable platform (4) of the mechanism can simulate the internal and external rotation motions of the human knee joint in addition to the bending and stretching motions of the human knee joint and the internal and external rotation motions of the ankle joint under the coupling driving of the driving branch chains (2.1, 2.2) and the metamorphic branch chain (3).

Fig. 3 is an exploded view of a structural model of an active branched chain provided by the present invention, which includes: a lower foot seat (2-1), a lower U-shaped seat (2-2), a cylinder (2-3) containing a drive, a piston rod (2-4) containing a drive, a joint (2-5), an upper U-shaped seat (2-6) and an upper foot seat (2-7). The lower foot seat (2-1) is connected with the fixed platform (1) through a screw to form a fixed pair; the lower foot seat (2-1) and the lower U-shaped seat (2-2) form a revolute pair, the lower U-shaped seat (2-2) and the cylindrical barrel (2-3) containing the drive form a revolute pair, and simultaneously, the two revolute pair axes are orthogonal and equivalent to a hooke pair; a cylinder (2-3) containing a drive and a piston rod (2-4) containing the drive form a drive moving pair and are provided by an electric push rod; a piston rod (2-4) containing a drive is connected with a joint (2-5) through threads to form a fixed pair; the joint (2-5) and the upper U-shaped seat (2-6) form a revolute pair, the upper U-shaped seat (2-6) and the upper foot seat (2-7) form a revolute pair, and simultaneously, the two revolute pair axes are orthogonal and equivalent to a hooke pair; the upper foot seats (2-7) and the movable platform (4) are connected into a fixed pair through screws; in the design, the active branched chains (2.1 and 2.2) are imitated to the biomechanical characteristics of skeletal muscle groups on the surface of the tibiofibula, and the two rotations of the tail end in the space and the movement along the direction of the branched chains are realized by driving the expansion and contraction of the moving pair.

FIG. 4 is an exploded view of a metamorphic branch structure model, which comprises a lower foot seat (3-1), a large sleeve (3-2), a rotation angle limiting lower rod (3-3), a cover plate (3-4), a rotation angle limiting upper rod (3-5), a joint (3-6), a small sleeve (3-7) and an upper foot seat (3-8). The lower foot seat (3-1) is connected with the fixed platform (1) through a screw to form a fixed pair; the lower foot seat (3-1) and the lower rod (3-3) with limited rotation angle form a rotation pair, and a large sleeve (3-2) is arranged at the gap position; the lower rotation-limiting angle rod (3-3) and the upper rotation-limiting angle rod (3-5) form a metamorphic kinematic pair which has angle limitation and avoids the generation of mechanism singularity caused by transitional rotation; the cover plate (3-4) penetrates through the rotation angle limiting upper rod (3-5) and is connected with the rotation angle limiting lower rod (3-3) through a screw, and in order to restrict the rotation angle limiting upper rod (3-5) to move along the direction of the branched chain; the rotation-limited angle upper rod (3-5) and the joint (3-6) are connected through threads to form a fixed pair; the joint (3-6) and the upper foot seat (3-8) form a rotating pair, and a small sleeve (3-7) is arranged at a gap position, and the sleeve is used for ensuring good centering performance of the metamorphic branch chain and ensuring flexible rotation of the mechanism; for the metamorphic kinematic pair in the branched chain, when the metamorphic kinematic pair is a fixed pair, the movable platform (4) of the mechanism can simulate the flexion and extension movement of the knee joint and the inward and outward turning movement of the ankle joint of a human body only under the driving of the driving branched chains (2.1 and 2.2). Because the internal and external rotation motion of the human knee joint does not exist all the time, the knee joint is activated only when the knee is bent, in addition, the dependence on the internal and external rotation motion in life is less, and the introduction of the metamorphic branched chain (3) is used for leading the artificial limb mechanism to carry out bionic design on the human knee joint better. When the metamorphic motion pair is a driving revolute pair, the movable platform (4) of the mechanism can simulate flexion and extension motions and internal and external rotation motions of the knee joint and the internal and external eversion motions of the ankle joint of a human body under the driving of the driving branched chains (2.1, 2.2) and the metamorphic branched chain (3).

The active knee and ankle joint artificial limb mechanism based on the metamorphic parallel mechanism not only can realize the flexion motion of the knee joint of a human body and the inward and outward turning motion of the ankle joint, but also can realize the inward and outward turning motion of the knee joint under the knee bending condition by controlling the mode switching of the metamorphic kinematic pair from the fixed pair to the driving revolute pair; in addition, the active ankle joint artificial limb mechanism (5) realizes the plantar flexion-dorsiflexion movement of the ankle joint of the human body through an independent rotating motor; the artificial limb mechanism has the characteristics of high structural rigidity, strong bearing capacity and the like, can realize the multi-degree-of-freedom motion characteristic of the knee and ankle joint of a human body, can simplify the complexity of the overall design of the mechanism to a certain extent, and is favorable for the arrangement and optimization of a subsequent control strategy.

Claims

1. An active knee-ankle joint prosthesis mechanism based on metamorphic parallel mechanism, comprising: the artificial limb robot comprises a fixed platform (1), active branched chains (2.1, 2.2), a metamorphic branched chain (3), a movable platform (4) and an active ankle joint artificial limb mechanism (5); the knee ankle joint artificial limb mechanism is formed by connecting a less-freedom-degree metamorphic parallel mechanism and a single-freedom-degree rotating active ankle joint artificial limb mechanism (5) in series, wherein the less-freedom-degree metamorphic parallel mechanism is formed by configuring a fixed platform (1), active branched chains (2.1, 2.2), a metamorphic branched chain (3) and a movable platform (4); the metamorphic parallel mechanism not only can realize the motion characteristics of knee joint flexion and extension and ankle joint eversion, but also can simulate the extension function of the crus skeletal muscle group through the forward or reverse movement of the electric push rod; because the internal and external rotation movement of the knee joint of the human body does not exist all the time, the knee joint is activated only when the knee is bent, and meanwhile, the dependence on the internal and external rotation movement in life is less, therefore, in order to enable the internal and external rotation movement function of the knee-ankle joint artificial limb mechanism to be activated when the knee is bent, a metamorphic branch chain with metamorphic characteristics is adopted; when the artificial limb mechanism is in a knee bending state, the metamorphic kinematic pair in the metamorphic branched chain is changed into a driving revolute pair, the internal rotation and the external rotation of the knee joint are activated, and when the artificial limb mechanism is in a non-knee bending state, the metamorphic kinematic pair is changed into a fixed pair, and the internal rotation and the external rotation of the knee joint are not activated; the artificial limb mechanism can effectively compensate the bionic motion characteristics of the damaged knee and ankle joints of the amputee;

the active branched chains (2.1, 2.2) are designed by taking knee joint flexion and ankle joint eversion of the execution prosthetic mechanism as targets, and comprise: a lower foot seat (2-1), a lower U-shaped seat (2-2), a cylinder (2-3) containing a drive, a piston rod (2-4) containing a drive, a joint (2-5), an upper U-shaped seat (2-6) and an upper foot seat (2-7); connection mode between each part: the lower foot seat (2-1) is connected with the fixed platform (1) through a screw to form a fixed pair; the lower foot seat (2-1) and the lower U-shaped seat (2-2) form a revolute pair, the lower U-shaped seat (2-2) and the cylindrical barrel (2-3) containing the drive form a revolute pair, and simultaneously, the two revolute pair axes are orthogonal and equivalent to a hooke pair; a cylinder (2-3) containing a drive and a piston rod (2-4) containing the drive form a drive moving pair, and the drive moving pair is provided by an electric push rod; a piston rod (2-4) containing a drive is connected with a joint (2-5) through threads to form a fixed pair; the joint (2-5) and the upper U-shaped seat (2-6) form a revolute pair, the upper U-shaped seat (2-6) and the upper foot seat (2-7) form a revolute pair, and simultaneously, the two revolute pair axes are orthogonal and equivalent to a hooke pair; the upper foot seats (2-7) and the movable platform (4) are connected into a fixed pair through screws; the active branched chains (2.1, 2.2) imitate the biomechanical characteristics of skeletal muscle groups on the surface of the tibiofibula, and the movable platform (4) can rotate around the movable platform and rotate around the space of the fixed platform by driving the expansion and contraction of the sliding pair so as to simulate the flexion and extension of the knee joint and the eversion of the ankle joint;

the metamorphic branched chain (3) is designed according to the internal and external rotation motions of the knee joint when the knee bending state is executed in the artificial limb mechanism, and comprises the following components: the device comprises a lower foot seat (3-1), a large sleeve (3-2), a rotation angle limiting lower rod (3-3), a cover plate (3-4), a rotation angle limiting upper rod (3-5), a joint (3-6), a small sleeve (3-7) and an upper foot seat (3-8); connection mode between each part: the lower foot seat (3-1) is connected with the fixed platform (1) through a screw to form a fixed pair; the lower foot seat (3-1) and the lower rod (3-3) with limited rotation angle form a rotation pair, and a large sleeve (3-2) is arranged at the gap position; the lower rotation-limited angle rod (3-3) and the upper rotation-limited angle rod (3-5) form a metamorphic kinematic pair which has angle limitation and avoids the generation of mechanism singularity due to excessive rotation; when the knee and ankle joint artificial limb mechanism is in a non-knee bending state, the metamorphic kinematic pair is a fixed pair, under the coupling constraint of the metamorphic branched chain (3) and the two driving branched chains (2.1, 2.2), the two pure rotations of the movable platform (4) can imitate the flexion and extension movements of the knee joint and the eversion movements of the ankle joint of a human body,

although the internal and external rotation movement of the knee joint can be activated only when the lower limbs of the human body bend, the dependence of the human body movement on the internal and external rotation of the knee joint is small; therefore, when the knee and ankle joint artificial limb mechanism is in a knee bending state, the metamorphic kinematic pair is changed from a fixed pair to a driving revolute pair with a limited rotation angle, the metamorphic branched chain (3) is under the coupling constraint of the two driving branched chains (2.1 and 2.2), and the motion of the movable platform (4) is added with a rotational degree of freedom, so that the internal and external rotation motion of the knee joint of a human body can be simulated; the cover plate (3-4) penetrates through the rotation angle limiting upper rod (3-5) and is connected with the rotation angle limiting lower rod (3-3) through a screw, and in order to restrict the rotation angle limiting upper rod (3-5) to move along the direction of the branched chain; the rotation-limited angle upper rod (3-5) and the joint (3-6) are connected through threads to form a fixed pair; the joint (3-6) and the upper foot seat (3-8) form a rotating pair, and a small sleeve (3-7) is arranged at the gap position, and the sleeve is used for ensuring the metamorphic branch chain to have good centering performance and ensuring the flexible rotation of the mechanism.