Ankle joint motion recognition mechanism

Abstract

This invention relates to an ankle joint motion recognition mechanism, comprising a first branch, a second branch, a third branch, a moving platform, and a fixed platform. All three branches are connected to the moving and fixed platforms, with the first and second branches symmetrical about the third branch. Each branch includes a motor and nine links, forming two parallelograms. The first branch has two encoders, and the second branch has one encoder. The mechanism has a fixed center and a moving center. The motors on the three branches control the pose of the moving platform, giving the moving center two degrees of freedom of movement around the fixed center and the moving platform three degrees of freedom of rotation around the moving center, thus achieving high-precision fitting of ankle joint motion. A human-machine motion mapping model is constructed based on the link angles measured by the encoders and the human-machine system mapping parameters. This model identifies the talus posture, effectively recognizing the talus movement patterns hidden within the ankle tissue, providing data for the design and optimization of the motion trajectory and posture transformation trajectory of subsequent ankle joint rehabilitation robots.

Description

Technical Field

[0001] This invention belongs to the field of ankle joint rehabilitation technology, and specifically relates to an ankle joint motion recognition mechanism. Background Technology

[0002] In medicine, the human ankle joint is generally defined as a generalized ball joint, composed of the tibiotalar joint and the subtalar joint. The tibiotalar joint connects the tibia and talus, while the subtalar joint connects the talus and calcaneus. The main task of ankle joint motion recognition is to identify the talus posture and obtain the relationship between the talus posture and the ankle joint posture, providing data for the design and optimization of motion trajectories for ankle rehabilitation robots. Because the talus is small and hidden within the ankle tissue, traditional visual recognition technology faces several challenges. First, it is difficult to accurately place sensors on the talus, resulting in ineffective identification of the talus posture. Second, the subjects actively provide the measured movements without constraints, making it difficult to guarantee the standardization and repeatability of the movements. Even minor muscle spasms causing tremors can significantly affect the authenticity and reliability of the motion recognition results. Therefore, traditional visual recognition technology struggles to accurately describe the ankle's foot-talar coupling motion.

[0003] To achieve ankle rehabilitation movements, the configuration and parameter design of ankle rehabilitation robots need to reference the actual physiological structure of the ankle joint. Common ankle joint fitting models include the RR model, S model, and SS model. Among them, the SS model combines the advantages of the RR and S models, achieving a high degree of matching with the ankle joint. The SS model treats both the tibiotalar joint and the subtalar joint as ball joints. Compared with the S model, the SS model fully considers the influence of the talus on ankle joint movement, reflecting its complex joint characteristics. Compared with the RR model, the SS model has a stronger degree of freedom matching capability, effectively adapting to the accompanying movements of the tibiotalar joint and the subtalar joint during ankle joint movements. However, the SS model includes a local degree of freedom for the equivalent rotational movement of the talus around the line connecting the centers of the tibiotalar joint and the subtalar joint. However, this rotational movement does not affect the overall ankle joint movement; instead, it increases the complexity of the model.

[0004] Therefore, this invention proposes an ankle joint motion recognition mechanism that can guide subjects to complete standard test movements and effectively identify the movement patterns of the talus. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the technical problem to be solved by the present invention is to provide an ankle joint motion recognition mechanism.

[0006] The technical solution adopted by the present invention to solve the aforementioned technical problem is as follows:

[0007] An ankle joint motion recognition mechanism includes a first branch, a second branch, a third branch, a moving platform, and a fixed platform; all three branches are connected to the moving platform and the fixed platform, and the first and second branches are symmetrical about the third branch; characterized in that each of the three branches includes a motor, a first link, a second link, a third link, a fourth link, a fifth link, a sixth link, a seventh link, an eighth link, and a ninth link; the motor is connected to the fixed platform, one end of the first link is connected to the output shaft of the motor, one end of the second link is rotatably connected to both the other end of the first link and one end of the fourth link, and the second... The other end of the connecting rod is rotatably connected to one end of the third connecting rod; one end of the fifth connecting rod is rotatably connected to the other end of the fourth connecting rod and one end of the seventh connecting rod; the other end of the fifth connecting rod is rotatably connected to the other end of the third connecting rod and one end of the sixth connecting rod; both ends of the eighth connecting rod are rotatably connected to the other ends of the seventh connecting rod and the other ends of the sixth connecting rod, respectively; one end of the ninth connecting rod is rotatably connected to the eighth connecting rod; the other end of the ninth connecting rod is rotatably connected to the moving platform; the second connecting rod, the fourth connecting rod, the fifth connecting rod, and the third connecting rod form a parallelogram; the fifth connecting rod, the seventh connecting rod, the eighth connecting rod, and the sixth connecting rod form a parallelogram.

[0008] The first branch chain has two encoders, used to detect the angle between the first and second links and the angle between the fourth and seventh links of the first branch chain, respectively; the second branch chain has one encoder, used to detect the angle between the first and second links of the second branch chain; the mechanism has a fixed sphere center and a moving sphere center, and the position and posture of the moving platform are controlled by motors on the three branches, so that the moving sphere center has two translational degrees of freedom around the fixed sphere center, and the moving platform has three rotational degrees of freedom around the moving sphere center;

[0009] The human-machine motion mapping model of the mechanism is shown in Equation (14). The talus posture is identified through the human-machine motion mapping model to realize ankle joint motion recognition.

[0010]

[0011]

[0012] In the formula: α T β T Let be the rotation angle of the talus about the x and y axes of a fixed coordinate system. Let α, β, and γ be the mapping functions, representing the dorsiflexion / plantarflexion, inversion / eversion, and internal / external rotation angles of the ankle joint. The angle between the first link and the second link of the first branch is denoted as . The angle between the first and second links of the second branch is given. The angle between the fourth and seventh links of the first branch is (p x ,p y ,p zLet (m1, m2, m3) be the position of the moving platform, (m4, m5, m6) be the relative position vectors between the origin of the fixed coordinate system and the origin of the tibial coordinate system, and (m4, m5, m6) be the relative position vectors between the origin of the moving coordinate system and the origin of the calcaneal coordinate system. Let l be the equivalent length of the talus. The origin of the fixed coordinate system is located at the center of the fixed sphere of the mechanism. The y-axis coincides with the angle bisector of the angle between the axes of the first and second branch motors. The z-axis is perpendicular to the axes of the first and second branch motors. The x-axis follows the right-hand rule. The origin of the moving coordinate system is located at the center of the moving sphere of the mechanism. The x-axis is parallel to the rotation axes of the eighth and seventh links of the third branch. The z-axis coincides with the rotation axes of the ninth link of the first branch and the moving platform. The y-axis follows the right-hand rule. The origin of the tibial coordinate system is located at the center of the tibiotalar joint, and its three axes are parallel to the corresponding axes of the fixed coordinate system. The origin of the calcaneal coordinate system is located at the center of the subtalar joint, and its three axes are parallel to the corresponding axes of the moving coordinate system.

[0013] Furthermore, the position of the moving platform is represented by the coordinates of the moving sphere's center in a fixed coordinate system as follows:

[0014]

[0015] In the formula: θ1 is the motor drive angle of the first branch, θ2 is the motor drive angle of the second branch, and l c It is the length of the third link of the first branch.

[0016] Furthermore, the position of the moving platform is represented by the angle between the foot posture parameters and the connecting rod:

[0017]

[0018] Wherein, parameter N expands to:

[0019]

[0020] Furthermore, the included angle between the motor axes of the first branch chain and the motor axes of the second branch chain is 90°; the motor axes of the first branch chain, the motor axes of the second branch chain, the rotation axes of the first and second links of the first branch chain, and the rotation axes of the first and second links of the second branch chain intersect at the fixed center of the mechanism; the rotation axes of the ninth and eighth links of the first branch chain, the rotation axis of the ninth link of the first branch chain and the moving platform, the rotation axes of the ninth and eighth links of the second branch chain, and the rotation axis of the ninth link of the second branch chain and the moving platform intersect at the moving center of the mechanism.

[0021] Furthermore, the fixed platform includes a U-shaped connector, a connecting column, and a support plate; the U-shaped connector and the support plate are connected by multiple connecting shafts, the U-shaped connector is located above the support plate, the moving platform is located between the U-shaped connector and the support plate, the human tibia is bound to the U-shaped connector, and the foot is bound to the moving platform.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] 1. This invention proposes an ankle joint fitting model that highly matches the actual ankle joint movement, namely the US model composed of the U-joint and the S-joint. The US model has the same motion description as the SS model and has a simpler structure. The U-joint in the US model is equivalent to the tibiotalar joint, and the S-joint is equivalent to the subtalar joint, which can more accurately match the macroscopic motion capability of the ankle joint.

[0024] 2. This institution, by accurately guiding subjects to complete the standard tested movements, effectively identifies the talus movement patterns hidden within the ankle tissue, providing data for the design and optimization of motion trajectories for ankle rehabilitation robots. By measuring joint angles through encoders, the mapping relationship between talus posture and ankle joint posture is derived, avoiding the invalidation of tested movement data due to various experimental interference factors. Attached Figure Description

[0025] Figure 1 This is an overall structural diagram of the present invention;

[0026] Figure 2 This is a structural diagram of the first branch of the present invention;

[0027] Figure 3 This is a structural diagram of the third branch of the present invention;

[0028] Figure 4 This is a structural diagram of the fixed platform of the present invention;

[0029] In the diagram: 1. First branch; 2. Second branch; 3. Third branch; 4. Moving platform; 5. Fixed platform; 6. Ankle joint fitting model;

[0030] 101. First branch motor; 102. First link of the first branch; 103. Second link of the first branch; 104. First encoder of the first branch; 105. Third link of the first branch; 106. Fourth link of the first branch; 107. Second encoder of the first branch; 108. Fifth link of the first branch; 109. Sixth link of the first branch; 110. Seventh link of the first branch; 111. Eighth link of the first branch; 112. Ninth link of the first branch;

[0031] 301. Third branch motor; 302. First link of the third branch; 303. Second link of the third branch; 304. Third link of the third branch; 305. Fourth link of the third branch; 306. Fifth link of the third branch; 307. Sixth link of the third branch; 308. Seventh link of the third branch; 309. Eighth link of the third branch;

[0032] 501. U-shaped connector; 502. Connecting column; 503. Support plate. Detailed Implementation

[0033] Specific embodiments are given below with reference to the accompanying drawings. These specific embodiments are only used to illustrate the technical solutions of the present invention in detail, and are not intended to limit the scope of protection of this application.

[0034] This invention provides an ankle joint motion recognition mechanism (hereinafter referred to as the mechanism, see below). Figures 1-4 The device includes a first branch 1, a second branch 2, a third branch 3, a moving platform 4, and a fixed platform 5. The upper end of the third branch 3 is connected to the rear end of the fixed platform 5, and the lower end of the third branch 3 is rotatably connected to the bottom of the moving platform 4. The first branch 1 and the second branch 2 are symmetrically arranged on both sides of the third branch 3. The upper ends of the first branch 1 and the second branch 2 are connected to the fixed platform 5, and the lower ends of the first branch 1 and the second branch 2 are rotatably connected to the bottom of the moving platform 4. In use, the human foot is placed on the moving platform 4, and the ankle joint is bound to the fixed platform 5.

[0035] See Figure 2The first branch 1 includes a first branch motor 101, a first branch first link 102, a first branch second link 103, a first branch first encoder 104, a first branch third link 105, a first branch fourth link 106, a first branch second encoder 107, a first branch fifth link 108, a first branch sixth link 109, a first branch seventh link 110, a first branch eighth link 111, and a first branch ninth link 112; wherein, the first branch motor 101 is fixedly connected to the fixed platform 5, and one end of the first branch first link 102 is connected to the first... The output shaft of the branch motor 101 is fixedly connected. One end of the second link 103 of the first branch is rotatably connected to the other end of the first link 102 and one end of the fourth link 106 of the first branch. The other end of the second link 103 of the first branch is rotatably connected to one end of the third link 105 of the first branch. One end of the fifth link 108 of the first branch is rotatably connected to the other end of the fourth link 106 and one end of the seventh link 110 of the first branch. The other end of the fifth link 108 of the first branch is simultaneously connected to the other end of the third link 105 and one end of the sixth link 109 of the first branch. Rotatable connections are made: the two ends of the eighth link 111 of the first branch are rotatably connected to the other ends of the seventh link 110 and the sixth link 109 of the first branch, respectively; one end of the ninth link 112 of the first branch is rotatably connected to the eighth link 111 of the first branch, and the other end of the ninth link 112 of the first branch is rotatably connected to the moving platform 4; the second link 103, the fourth link 106, the fifth link 108, and the third link 105 of the first branch form a parallelogram; the fifth link 108, the seventh link 110, and the first branch... The eighth link 111 and the sixth link 109 of the first branch form a parallelogram; the first encoder 104 of the first branch is installed at the connection between the first link 102 and the second link 103 of the first branch, and is used to detect the included angle between the first link 102 and the second link 103 of the first branch; the second encoder 107 of the first branch is installed at the connection between the fifth link 108, the fourth link 106 and the seventh link 110 of the first branch, and is used to detect the included angle between the fourth link 106 and the seventh link 110 of the first branch.

[0036] The second branch 2 has a similar structure to the first branch 1, except that the second branch 2 has only one encoder, located at the connection between the first link of the second branch and the second link of the second branch.

[0037] See Figure 3The third branch 3 includes a third branch motor 301, a third branch first link 302, a third branch second link 303, a third branch third link 304, a third branch fourth link 305, a third branch fifth link 306, a third branch sixth link 307, a third branch seventh link 308, a third branch eighth link 309, and a third branch ninth link 310; wherein, the third branch motor 301 is fixedly connected to the fixed platform 5, one end of the third branch first link 302 is fixedly connected to the output shaft of the third branch motor 301, one end of the third branch second link 303 is rotatably connected to both the other end of the third branch first link 302 and one end of the third branch fourth link 305, the other end of the third branch second link 303 is rotatably connected to one end of the third branch third link 304, and one end of the third branch fifth link 306 is simultaneously connected to the third branch fourth link 305. 5. The other end is rotatably connected to one end of the seventh link 308 of the third branch. The other end of the fifth link 306 of the third branch is simultaneously rotatably connected to the other end of the third link 304 of the third branch and one end of the sixth link 307 of the third branch. The two ends of the eighth link 309 of the third branch are rotatably connected to the other ends of the seventh link 308 and the sixth link 307 of the third branch, respectively. One end of the ninth link 310 of the third branch is rotatably connected to one end of the eighth link 309 of the third branch, and the other end of the ninth link 310 of the third branch is rotatably connected to the moving platform 4. The second link 303, the third link 304, the fifth link 306 and the fourth link 305 of the third branch form a parallelogram. The fifth link 306, the sixth link 307 and the eighth link 309 and the seventh link 308 of the third branch form a parallelogram.

[0038] The angle between the axes of the first branch motor 101 and the second branch motor is 90°. The axes of the first branch motor 101, the second branch motor, the rotation axes of the first link 102 and the second link 103, and the rotation axes of the first link and the second link intersect at a point, which is the fixed ball center O1 of the mechanism. The rotation axes of the ninth link 112 and the eighth link 111, the rotation axis of the ninth link 112 and the moving platform 4, the rotation axes of the ninth link 112 and the eighth link 111, and the rotation axis of the ninth link 112 and the moving platform 4 intersect at a point, which is the moving ball center O of the mechanism.

[0039] See Figure 4 The fixed platform 5 includes a U-shaped connector 501, a connecting column 502, and a support plate 503; the U-shaped connector 501 is connected to the support plate 503 through multiple connecting shafts 502, the U-shaped connector 501 is located above the support plate 503, and three branches are connected to the U-shaped connector 501; the human tibia is connected to the U-shaped connector 501 by binding.

[0040] This mechanism is equivalent to a US model consisting of U-joints and S-joints, possessing 3 rotational degrees of freedom and 2 translational degrees of freedom. In contrast, the human ankle joint only has 3 rotational degrees of freedom: dorsiflexion / plantarflexion, inversion / eversion, and internal / external rotation. This is because, in addition to the rigid structure composed of the tibia and subtalar joint, the ankle joint is connected to numerous complex ligaments and tendons. Under the constraints of these tissues, a significant coupling occurs between the tibiotalar joint and the subtalar joint, restricting the movement of the talus. The mechanism's motion can be viewed as a two-degree-of-freedom rotation of the movable ball's center around the fixed ball's center, with the movable platform having three degrees of freedom. In application, the fixed platform 5 is bound to the human tibia, and the movable platform 4 is bound to the foot. The U-joint corresponds to the tibiotalar joint, and the S-joint corresponds to the subtalar joint. The position and posture of the movable platform 4 are controlled by three branch motors, thereby controlling the ankle joint to move along a predetermined trajectory.

[0041] When the above mechanism is used for ankle joint recognition, a human-machine system model consisting of ankle joint fitting model 6 and the mechanism is established. In the human-machine system model, a fixed coordinate system O1-x1y1z1 is established with the fixed ball center O1 of the mechanism as the origin. The y1 axis coincides with the angle bisector of the angle between the axis of the first branch motor and the axis of the second branch motor. The z1 axis is perpendicular to both the axis of the first branch motor and the axis of the second branch motor. The x1 axis is determined by the right-hand rule. A moving coordinate system O-xyz is established with the moving ball center O of the mechanism as the origin. The x-axis is parallel to the rotation axis of the eighth link and the seventh link of the third branch. The z-axis coincides with the rotation axis of the ninth link of the first branch and the moving platform. The y-axis is determined by the right-hand rule. The tibiotalar joint center O1 is established with the fixed ball center O1 as the origin. T Establish a tibial coordinate system O with the origin. T -x T y T z T x T y T z T The axes are parallel to the x1, y1, and z1 axes of the fixed coordinate system, respectively; with a distance O from the center of the lower joint. S Establish a calcaneal coordinate system O with the origin. s -x s y s z s x s y s z s The axes are parallel to the x, y, and z axes of the moving coordinate system, respectively;

[0042] The position of the moving platform is represented by the coordinates of the center of the moving sphere in the fixed coordinate system (p). x ,p y ,p z To describe it, it can be represented as:

[0043]

[0044] In the formula: The detection angle of the first encoder in the first branch. The detection angle of the second branch encoder. Let θ1 be the detection angle of the second encoder in the first branch, θ2 be the drive angle of the first branch motor, and l be the drive angle of the second branch motor. c The length of the third link of the first branch is the same as that of the third link of the first branch, the fourth link of the first branch, the sixth link of the first branch, the seventh link of the first branch, the third link of the second branch, the fourth link of the second branch, the sixth link of the second branch, and the seventh link of the second branch.

[0045] The talus posture matrix is ​​represented as follows:

[0046] T Talus =Rot(y,β) T Rot(x,α) T (2)

[0047] In the formula: Rot(x,α) T Rot(y,β) T Let α be the rotation matrix of the talus about the x and y axes of a fixed coordinate system. T β T The rotation angle of the talus around the x and y axes of a fixed coordinate system, i.e., the dorsiflexion / plantarflexion and reversal / valgus angles of the talus;

[0048] α T and β T Defined as talus posture parameters, the ankle joint's dorsiflexion / plantarflexion, inversion / eversion, and internal / external rotation angles α, β, and γ are defined as foot posture parameters. The talus posture parameters (α...) will be used to describe... T / β T The correlation function model of the foot posture parameters (α / β / γ) and the foot position parameters (α / β / γ) is defined as the "foot-spur coupled motion model", then:

[0049]

[0050] In the formula: F α (·), F β (·) represents a relational function;

[0051] The position of the subtalar joint (S-joint) center in the ankle joint fitting model is represented as follows:

[0052] (p Tx ,p Ty ,p Tz ,1) T =Rot(y,β) T Rot(x,α) T (0,0,l,1)T (4)

[0053] In the formula: (p Tx ,p Ty ,p Tz ) represents the coordinates of the subtalar joint center; l represents the equivalent talus length, which is equal to the distance between the center of the tibiotalar joint and the center of the subtalar joint.

[0054] The rotational transformation matrix of the ankle joint is represented as follows:

[0055] T Ankle =Tran(p Tx ,p Ty ,p Tz )Rot(x,α)Rot(y,β)Rot(z,γ) (5)

[0056]

[0057] In the formula: Tran(·) is the translation matrix, and Rot(x,α), Rot(y,β), and Rot(z,γ) are the rotation matrices of the ankle joint about the three axes of the fixed coordinate system;

[0058] Due to various circumstances during use, the relative position between the mechanism and the ankle joint coordinate system is random. Therefore, the origin O1 of the fixed coordinate system and the origin O of the tibial coordinate system are fixed. T The relative position vectors between them are denoted as (m1, m2, m3), with the origin O of the moving coordinate system and the calcaneal coordinate system O... S The relative position vectors between them are denoted as (m4, m5, m6); therefore, if m1, m2, m3, m4, m5, and m6 are defined as the "mapping parameters" of the human-machine system, then the rotational transformation matrix of the ankle joint can also be expressed as:

[0059] T Ankle =Tran(m1,m2,m3)T Robot Tran(m4,m5,m6) (7)

[0060] T Robot =Tran(p x ,p y ,p z )Rot(x,α)Rot(y,β)Rot(z,γ) (8)

[0061] In the formula: T Robot Let be the rotation transformation matrix of the moving platform;

[0062] From equations (5), (7) and (8), we can obtain:

[0063]

[0064] Wherein, parameter (n) x ,n y ,n z ,o x ,o y ,o z ,a x ,a y ,a z The ankle joint rotation matrix R is formed. Ankle , can be represented as:

[0065]

[0066] Based on the analysis of equation (9), the talus posture parameters (α) T / β T ) is composed of foot posture parameters (α / β / γ) and detection angle The mapping parameters (m1, m2, m3, m4, m5, m6) between the human-machine system and the system can be represented as:

[0067]

[0068] The position of the moving platform is determined by foot posture parameters (α / β / γ) and detection angle. Represented as:

[0069]

[0070] Here, parameter N can be expanded as:

[0071]

[0072] In summary, the human-machine motion mapping model can be described as follows:

[0073]

[0074] In the formula: For mapping functions;

[0075] Therefore, the detection angle is obtained through three encoders. The mapping parameters (m1, m2, m3, m4, m5, m6) of the human-machine system are constants. The mapping relationship between the talus posture and the foot posture is obtained through equation (14), providing data for the design and optimization of the motion trajectory and posture transformation trajectory of the subsequent ankle joint rehabilitation robot. Any aspects not mentioned in this invention are applicable to the prior art.

Claims

1. An ankle joint motion recognition mechanism, comprising a first branch, a second branch, a third branch, a moving platform, and a fixed platform; all three branches are connected to the moving platform and the fixed platform, and the first and second branches are symmetrical about the third branch; characterized in that, Each of the three branches includes a motor, a first link, a second link, a third link, a fourth link, a fifth link, a sixth link, a seventh link, an eighth link, and a ninth link. The motor is connected to the fixed platform. One end of the first link is connected to the output shaft of the motor. One end of the second link is rotatably connected to both the other end of the first link and one end of the fourth link. The other end of the second link is rotatably connected to both the other end of the third link and one end of the third link. One end of the fifth link is rotatably connected to both the other end of the fourth link and one end of the seventh link. The other end of the fifth link is rotatably connected to both the other end of the third link and one end of the sixth link. Both ends of the eighth link are rotatably connected to the other ends of the seventh link and the other end of the sixth link, respectively. One end of the ninth link is rotatably connected to the eighth link, and the other end of the ninth link is rotatably connected to the moving platform. The second, fourth, fifth, and third links form a parallelogram, and the fifth, seventh, eighth, and sixth links also form a parallelogram. The first branch chain has two encoders, used to detect the angle between the first and second links and the angle between the fourth and seventh links of the first branch chain, respectively; the second branch chain has one encoder, used to detect the angle between the first and second links of the second branch chain; the mechanism has a fixed sphere center and a moving sphere center, and the position and posture of the moving platform are controlled by motors on the three branches, so that the moving sphere center has two translational degrees of freedom around the fixed sphere center, and the moving platform has three rotational degrees of freedom around the moving sphere center; The angle between the motor axes of the first branch chain and the motor axes of the second branch chain is 90°; the motor axes of the first branch chain, the motor axes of the second branch chain, the rotation axes of the first and second links of the first branch chain, and the rotation axes of the first and second links of the second branch chain intersect at a point, which is the fixed center of the mechanism; the rotation axes of the ninth and eighth links of the first branch chain, the rotation axis of the ninth link of the first branch chain and the moving platform, the rotation axes of the ninth and eighth links of the second branch chain, and the rotation axis of the ninth link of the second branch chain and the moving platform intersect at a point, which is the moving center of the mechanism; The human-machine motion mapping model of the mechanism is shown in Equation (14). The talus posture is identified through the human-machine motion mapping model to realize ankle joint motion recognition. (14) (11) In the formula: , For the talus, a fixed coordinate system is used. x , y The rotation angle of the shaft, , For mapping functions, , and These refer to the dorsiflexion / plantarflexion, inversion / eversion, and internal / external rotation angles of the ankle joint. The angle between the first link and the second link of the first branch is denoted as . The angle between the first and second links of the second branch is given. The angle between the fourth and seventh links of the first branch is [angle]. For the position of the moving platform, Let be the relative position vector between the origin of the fixed coordinate system and the origin of the tibial coordinate system. Let be the relative position vector between the origin of the moving coordinate system and the calcaneal coordinate system. The equivalent length of the talus; the origin of the coordinate system is located at the center of the fixed sphere of the mechanism. y The z-axis coincides with the angle bisector of the angle between the axis of the first branch motor and the axis of the second branch motor, and the z-axis is perpendicular to the axes of the first and second branch motors. x The axes obey the right-hand rule; the origin of the moving coordinate system is located at the center of the moving sphere of the mechanism. x The axis is parallel to the rotation axis of the eighth and seventh links of the third branch. The axis coincides with the rotation axis of the ninth link of the first branch and the moving platform. The axes follow the right-hand rule; the origin of the tibial coordinate system is located at the center of the tibiotalar joint, and its three axes are parallel to the corresponding axes of the fixed coordinate system; the origin of the calcaneal coordinate system is located at the center of the subtalar joint, and its three axes are parallel to the corresponding axes of the moving coordinate system.

2. The ankle joint motion recognition mechanism according to claim 1, characterized in that, The position of the moving platform is represented by the coordinates of the moving sphere's center in a fixed coordinate system as follows: (1) In the formula: The motor drive angle for the first branch. For the motor drive angle of the second branch, It is the length of the third link of the first branch.

3. The ankle joint motion recognition mechanism according to claim 1, characterized in that, The position of the moving platform is represented by the angle between the foot posture parameters and the connecting rod: (12) Among them, parameters N Expanded to: (13)。 4. The ankle joint motion recognition mechanism according to claim 1, characterized in that, The fixed platform includes a U-shaped connector, a connecting column, and a support plate; the U-shaped connector and the support plate are connected by multiple connecting shafts, the U-shaped connector is located above the support plate, the moving platform is located between the U-shaped connector and the support plate, the human tibia is bound to the U-shaped connector, and the foot is bound to the moving platform.

Images