A knee joint cross-four-bar exoskeleton and its design method based on image registration

Abstract

The present invention belongs to the field of exoskeleton robots, and discloses a knee joint cross four-bar exoskeleton and a design method thereof based on image registration, comprising a thigh component, a calf component, a calf-high and low-calf connecting component and a driving component, wherein the thigh component and the calf component are connected through the calf-high and low-calf connecting component, and the driving component is used to drive the calf-high and low-calf connecting component to drive the thigh component and the calf component to move, and the thigh component, the calf component, the active connecting rod component, and the driven connecting plate constitute a cross-hinge four-bar mechanism, and the length of the hinge cross four-bar mechanism is designed according to the collected bone X-ray image. The exoskeleton can be well applied in scenes such as medical rehabilitation and carrying assistance, and the "J"-shaped curve prior knowledge is added in the process of solving the instantaneous center curve of the knee joint, so that the solution is fast and the degree of dependence on data is small. The four-bar mechanism schematic diagram is designed according to the characteristics of the anterior and posterior cruciate ligaments of the knee joint, and the mechanism parameters are mapped through the X-ray image, so that the designed mechanism has the function of an artificial knee joint.

Description

Technical Field

[0001] The invention belongs to the field of exoskeleton robots, and in particular relates to a knee joint cross four-bar exoskeleton and a design method thereof based on image registration. Background Art

[0002] In the face of the worsening situation of social aging, the knee joint is a part prone to problems, and it is necessary to quickly design a suitable exoskeleton for knee joint exercise rehabilitation. Knee joint exoskeletons have always been a research hotspot in the field of robotics. Knee joint rehabilitation training can be completed through knee joint exoskeletons, saving manual time.

[0003] Currently, most knee exoskeletons are heavy and are designed by collecting motion data in vitro. This method cannot observe the actual movement state inside the bones.

[0004] Chinese invention CN202110610808.1 discloses a customized high-compliance knee exoskeleton design method, which discloses the solution method of the ICR curve in the specification, solving the problem of obtaining the instantaneous center curve in Chinese utility model CN209850913U, but according to its claims and its specification, the density of the X-ray images taken is too high, which causes more radiation to the patient's body tissue, and the calculation method is too dependent on the number of angles of the patient's shooting. In addition, the patent does not perform the registration process for each angle image, which increases the error of the instantaneous center curve of the knee joint obtained, and there is no design analysis and engineering feasibility verification of the principle and structure of the mechanism. Summary of the invention

[0005] The present invention aims to provide a knee joint crossed four-bar exoskeleton and a design method thereof based on image registration to solve the above-mentioned technical problems.

[0006] In order to solve the above technical problems, the specific technical solutions of a knee joint cross four-bar exoskeleton and a design method thereof based on image registration are as follows:

[0007] A knee joint cross four-bar exoskeleton comprises a thigh component, a shank component, a shank-high and low-shank connecting component and a driving component, wherein the thigh component and the shank component are connected via the shank-high and low-shank connecting component, and the driving component is used to drive the shank-high and low-shank connecting component to drive the thigh component and the shank component to move, wherein the thigh component comprises a thigh component, and the shank component comprises a shank component, and the shank-high and low-shank connecting component comprises an active connecting rod component and a driven connecting plate, wherein the thigh component, the shank component, the active connecting rod component and the driven connecting plate constitute a cross-hinged four-bar mechanism, and the length of the cross-hinged four-bar mechanism is designed according to a collected bone X-ray image.

[0008] Furthermore, the thigh component includes a thigh baffle, a thigh component, a thigh bearing seat, a thigh connecting member, and a thigh fixing plate. The thigh baffle includes four symmetrically arranged waist holes. The thigh fixing plate is fixedly connected to the thigh baffle through the waist holes. The thigh component and the thigh baffle are fixedly connected through the thigh connecting member. The thigh bearing seat is fixed on the thigh component. The thigh fixing plate is fixed on the thigh. When installed, the thigh component is fixed relative to the thigh. The thigh component has two arc-shaped contours, namely, thigh component arc A and thigh component arc B. The thigh component arc A is tangent to the rounded corners at both ends and has a length of 80 to 120 mm. The thigh component arc B is tangent to the rounded corners at both ends and has a length of 25 to 60 mm.

[0009] Furthermore, the calf component includes a calf component, a calf baffle, a calf connecting member, a sleeve, a calf bearing seat, a calf optical axis, and a calf fixing plate. The calf baffle includes four symmetrically arranged waist holes. The calf fixing plate is fixedly connected to the calf baffle through the waist holes. The calf component and the calf baffle are fixedly connected through the calf connecting member. The calf bearing seat is fixed on the calf baffle and the calf component. The sleeve is connected to the calf bearing seat. The calf optical axis is in the middle of the calf bearing seat. The calf fixing plate is fixed on the calf. When installed, the calf component is fixed relative to the calf. The calf component has a calf component arc A and a calf component arc B with arc-shaped contours at both ends. The calf component arc A is tangent to the fillets at both ends and has a length of 30 to 50 mm. The calf component arc B is tangent to the fillets at both ends and has a length of 35 to 60 mm.

[0010] Furthermore, the thigh and calf connecting components include an active connecting rod, a driven connecting plate, and a pin shaft. One end of the active connecting rod is installed on the thigh component, and the other end is installed on the calf optical axis, and is positioned between the calf bearing seat and the sleeve. The driven connecting plate is a rounded rectangular shape with four connecting holes around it and two large holes at both ends of the midline of the long side. The driven connecting plate and the calf bearing seat are connected by a pin shaft.

[0011] Furthermore, the driving component includes a worm gear reducer and a motor, the worm gear reducer is fixed on the thigh component of the thigh component, the motor is arranged above the worm gear reducer, a rectangular slot is opened below the worm gear reducer, the active connecting rod is fixedly connected to the output shaft of the worm gear reducer through the rectangular slot, and the active connecting rod can swing periodically in the rectangular slot under the drive of the motor.

[0012] The present invention also discloses a design method of a knee joint cross four-bar exoskeleton based on image registration, comprising the following steps:

[0013] Step 1: Take X-ray images of the femur with the femur still and the tibia bent at angles of 0°, 30°, 60°, 90°, and 120° under a medical X-ray machine;

[0014] Step 2: Preprocess the acquired image data;

[0015] Step 3: Add marker points to the preprocessed image. The specific steps of step 3 are as follows: select 6 points on the femur where the curvature of the contour curve changes significantly as marker points, and select 3 points on the tibia where the curvature of the contour curve changes significantly as marker points. The point set of the i-th image is represented as S i , the coordinates of the jth point of the i-th X-ray image are Where i=1,2,3,4,5; j=1,2,3......9;

[0016] Step 4: Image registration based on the added markers;

[0017] Step 5: Calculate the instantaneous center curve of the knee joint based on the registered images;

[0018] Step 6: Calculate the length of each rod of the four-bar mechanism;

[0019] Step 7: Set the solved rod length as the parameter corresponding to the actual rod.

[0020] Furthermore, the step 2 includes the following specific steps:

[0021] Step 2.1: Use computer programming language to convert the acquired DICOM format image data into JPG format data;

[0022] Step 2.2: Use the scaling factor μ to correct the image size and use a power transformation to enhance the image contrast.

[0023] Furthermore, the step 4 includes the following specific steps:

[0024] Step 4.1: Keep the points of each image relatively unchanged and align all images to the first image;

[0025] Step 4.2: The points Pi (i = 1, 2...6) on the femur are registered, and the 0° mark point is used as the point set. The registration error is Loss, and the formula used is as follows:

[0026] in Step 4.3: Use the third point of each image as the origin to establish a coordinate system. There are three parameters in the registration process: the translation in the x-axis direction The amount of translation along the y-axis Angle of rotation around the origin θ i , expressed by a coordinate transformation matrix, each point set undergoes coordinate transformation, and the coordinate transformation matrix and coordinate transformation are as follows:

[0027]

[0028] Step 4.4: Taking the registration error Loss as the objective function, θ, t x ,t y To optimize the variables, There are 12 variables in total, and the constraints are st. The constraints used are as follows:

[0029]

[0030] Step 4.5: Select an optimization algorithm to solve the target programming problem, save the optimal variables solved and visualize the aligned point set.

[0031] Furthermore, the step 5 includes the following specific steps:

[0032] Step 5.1: Calculate P using the cubic spline interpolation method i 7 , P i 8 , P i 9 The motion trajectory L composed of (i=1,2,3,4,5) 7 , L 8 , L 9 ;

[0033] Step 5.2: Calculate the instantaneous rotation center of the femur and tibia at five moments, and calculate an instantaneous rotation center I for each image. i (x c ,y c ), points 7, 8, and 9 are combined in pairs to calculate 3 instantaneous rotation centers for each image The normal slope of points 7, 8, and 9 on the curve in the i-th image is recorded as Where jk = 78, 79, 89, and the average is taken. The specific calculation method is as follows:

[0034] Step 5.3: By I i The coordinates of the cubic curve L0 are changed to find the instantaneous center curve L of the knee joint. The curve used is a curve within a limited range, in the shape of a "J", L0: y = ax 3 +bx 2 +cx+d, where the parameter constraints and the range of the curve are as follows: in

[0035] Step 5.4: The optimization objective of the design curve L is dist represents the distance between two points, where Q iThe coordinates of in And r i for The i-th element in the r vector is the angle at which the X-ray image was taken;

[0036] Step 5.5: Select an optimization algorithm to solve the decision variable X = [a, b, c, d] to determine the equation of the curve L and solve the instantaneous center of the knee joint.

[0037] Furthermore, the step 6 includes the following specific steps:

[0038] Step 6.1: Design a cross four-bar linkage with lengths of l1, l2, l3, and l4 respectively. Set the bar length constraints. The specific constraints are as follows:

[0039] 45mm<l1<65mm

[0040] 80mm<l2<120mm

[0041] 70mm<l3<110mm

[0042] 35mm<l4<60mm

[0043]

[0044] Step 6.2: Take 10 points evenly on the knee joint instantaneous center curve L. ci (x ci ,y ci ), the instantaneous center curve of the mechanism is composed of intersection points, and the instantaneous center L of the four-bar mechanism when the angle between l2 and l1 is α ci (x ci ,y ci ), where i = 1, 2, 3...10, the value of α is Take 10 values ​​evenly, L c i (x ci ,y ci ) is solved by the six-variable linear equation system. The specific calculation method is as follows:

[0045]

[0046] Step 6.3: Define the objective function That is, the mean square error of the distance between the instantaneous center curve of the knee joint and the instantaneous center estimation of the rod calculation. The intersection of rod 1 and rod 2 is taken as the origin, and the whole mechanism rotates around the origin by γ. The decision variable is X = [γ, l1, l2, l3, l4], and the optimization algorithm is used to solve all rod lengths.

[0047] The present invention provides a cross-four-bar exoskeleton for the knee joint and a design method thereof based on image registration, which has the following advantages: The present invention provides an exoskeleton designed based on image data, which has the characteristics of fast design speed, high design accuracy, and the designed structure is lightweight and easy to maintain. It can be effectively used on patients who need rehabilitation training for their knee joints. The design method of the present invention extracts key information, has fast calculation, and the effect meets expectations. The cross-four-bar mechanism used is well in line with the characteristics of the anterior and posterior cruciate ligaments of the human body, and has high bionics. The designed exoskeleton can be combined with an intelligent control algorithm to plan the motion trajectory of the exoskeleton. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 is an overall schematic diagram of the exoskeleton described in this application;

[0049] Figure 2 It is a partial side view schematic diagram of the exoskeleton described in this application;

[0050] Figure 3 This is a partial schematic diagram of the exoskeleton calf baffle after being disassembled;

[0051] Figure 4 This is a schematic diagram of the opening slot of the exoskeleton worm gear reducer described in this application;

[0052] Figure 5 This is a schematic diagram of the exoskeleton thigh baffle described in this application;

[0053] Figure 6 This is a schematic diagram of the exoskeleton thigh component described in this application;

[0054] Figure 7 This is a schematic diagram of the exoskeleton calf baffle described in this application;

[0055] Figure 8 This is a schematic diagram of the exoskeleton calf member described in this application;

[0056] Fig. 9 This is a schematic diagram of the exoskeleton driven connecting plate described in this application;

[0057] Fig.10 This is a schematic diagram of the active link member of the exoskeleton described in this application;

[0058] Fig.11 The schematic diagram of the cross four-bar mechanism of the design method described in this application;

[0059] Fig.12 A schematic diagram of the anterior and posterior cruciate ligament distribution of the design method described in this application;

[0060] Fig.13 A flowchart of the design method described in this application;

[0061] Fig.14 This is a schematic diagram of bone image acquisition for this application;

[0062] Fig.15 This is a diagram of X-ray image point marking numbers for the design method described in this application;

[0063] Fig.16 This is an X-ray image registration effect diagram of the design method described in this application;

[0064] Fig.17 A schematic diagram of solving the instantaneous center curve of the knee joint according to the design method described in this application;

[0065] Fig.18 This is the instantaneous center curve of the knee joint designed by the method of this application.

[0066] In the figure: 1. thigh baffle; 2. thigh fixing plate; 3. active connecting rod; 4. calf baffle; 5. calf fixing plate; 6. calf connecting piece; 7. calf piece; 71. calf piece arc A; 72. calf piece arc B; 8. pin shaft; 9. driven connecting plate; 10. thigh piece; 101. thigh piece arc A; 102. thigh piece arc B; 11. worm gear reduction box; 111. rectangular notch; 12. thigh connecting piece; 13. thigh bearing; 14. bushing; 15. calf bearing seat; 16. calf optical axis; 17. motor. DETAILED DESCRIPTION

[0067] In order to better understand the purpose, structure and function of the present invention, a knee cross four-bar exoskeleton and a design method based on image registration of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0068] like Figure 1 As shown, the exoskeleton of the present invention includes a thigh component, a calf component, a calf-feet connecting component and a driving component. The thigh component and the calf component are connected by the calf-feet connecting component. The driving component is used to drive the calf-feet connecting component to drive the thigh component and the calf component to move.

[0069] like Figure 1 , Figure 2 As shown, the thigh component includes a thigh baffle 1, a thigh component 10, a thigh bearing seat 13, a thigh connecting member 12, and a thigh fixing plate 2. The thigh baffle 1 includes four symmetrically arranged waist holes, and the thigh fixing plate 2 is fixedly connected to the thigh baffle 1 through the waist holes, and the height can be adjusted along the waist hole direction. The thigh component 10 and the thigh baffle 1 are fixedly connected through the thigh connecting member 12, and the thigh bearing seat 13 is fixed on the thigh component 10. The thigh fixing plate 2 is fixed on the thigh, and the thigh component is fixed relative to the thigh during installation.

[0070] like Figure 6As shown, the thigh part 10 has two arc-shaped contours, namely, thigh part arc A101 and thigh part arc B102. The thigh part arc A101 is tangent to the rounded corners at both ends and has a length of 80 to 120 mm. The thigh part arc B102 is tangent to the rounded corners at both ends and has a length of 25 to 60 mm.

[0071] like Figure 1-3 As shown, the calf component includes a calf component 7, a calf baffle 4, a calf connector 6, a sleeve 14, a calf bearing seat 15, a calf optical axis 16, and a calf fixing plate 5. The calf baffle 4 includes four symmetrically arranged waist holes, and the calf fixing plate 5 is fixedly connected to the calf baffle 4 through the waist holes, and the height can be adjusted along the waist hole direction. The calf component 7 and the calf baffle 4 are fixedly connected through the calf connector 6, the calf bearing seat 15 is fixed on the calf baffle 4 and the calf component 7, the sleeve 14 is connected to the calf bearing seat 15, and the calf optical axis 16 is in the middle of the calf bearing seat 15. The calf fixing plate 5 is fixed on the calf, and the calf component is fixed relative to the calf during installation.

[0072] like Figure 8 As shown, the calf member 7 has a calf member arc A71 and a calf member arc B72 with arc-shaped contours at both ends. The calf member arc A71 is tangent to the rounded corners at both ends and has a length of 30 to 50 mm. The calf member arc B72 is tangent to the rounded corners at both ends and has a length of 35 to 60 mm.

[0073] The thigh and calf connection components include an active connecting rod 3, a driven connecting plate 9, and a pin 8. One end of the active connecting rod 3 is mounted on the thigh component, and the other end is mounted on the calf optical axis 16, and is positioned between the calf bearing seat 15 and the sleeve 14. The driven connecting plate 9 is a rounded rectangular shape, with four connecting holes around it and two large holes at both ends of the long side midline. The driven connecting plate 9 and the calf bearing seat 15 are connected by the pin 8.

[0074] The driving component includes a worm gear reduction box 11 and a motor 17. The worm gear reduction box 11 is fixed on the thigh member 10 of the thigh member, the motor 17 is arranged above the worm gear reduction box 11, a rectangular notch is opened below the worm gear reduction box 11, the active connecting rod 3 is fixedly connected to the output shaft of the worm gear reduction box 11 through the rectangular notch 111, and the active connecting rod 3 can be periodically swung in the rectangular notch driven by the motor 17.

[0075] Threaded holes are formed at both ends of the thigh connector 12 and the calf connector 6, and the connections between the components not described are all made by threaded or bolted connections.

[0076] The thigh member 10 in the thigh member, the calf member 7 in the calf member, the active connecting rod member 3, and the driven connecting plate 9 constitute a cross-hinged four-bar mechanism. The length of the cross-hinged four-bar mechanism is designed according to the collected bone X-ray images, and the collected images are not less than two.

[0077] When the device of the present invention is installed on the knee joint of the lower limb of the human body, the motor 17 drives the active connecting rod 3 to move through the worm gear reducer 11. Due to the movement law of the cross-hinged four-bar mechanism, the calf moves under the traction of the fixed calf, thereby achieving the purpose of assisting the patient's movement.

[0078] Figure 2 It is a side view of the whole exoskeleton. The worm gearbox 11 is fixed on the thigh member 10. The motor 17 drives the active connecting rod member 3 to swing periodically. Figure 4 The rectangular slot 111 shown provides movement space for the swinging motion.

[0079] Figure 5 , 7 It is a schematic diagram of the structure of the thigh baffle 1 and the calf baffle 4, on which the patient's thighs and calves rest when wearing them. Four small holes are provided on the thigh baffle 1 and the calf baffle 4, and the best wearing position can be determined by adjusting the thigh fixing plate 2 and the calf fixing plate 5.

[0080] Figure 6 , 8 9, 10, and 11 are the schematic diagrams of the cross-hinged four-bar mechanism and the design parameters corresponding to the actual bars. 1、 l 2、 l 3、 l4 are the distances between the center holes, Figure 8 The distance l1 in is the distance from a hole to the center hole of the bearing on the lower leg member 7, Fig.10 The distance l2 in is the distance between the center holes of the active connecting rod bearings. Figure 6 The distance l3 in is the distance between the center holes of the bearings on the thigh member 10, Fig. 9 The distance l4 in is the distance between the bearing center holes of the driven connecting plate 9.

[0081] like Fig.13 As shown, the design method is described in detail below with reference to the accompanying drawings:

[0082] Step 1: Fig.14 As shown, X-ray images were taken under a medical X-ray machine with the femur fixed and the tibia bent at angles of 0°, 30°, 60°, 90°, and 120°;

[0083] Step 2: Preprocess the acquired image data. The specific steps are as follows:

[0084] Step 2.1: Use computer programming language to convert the acquired DICOM format image data into JPG format data;

[0085] Step 2.2: Use the scale factor μ to correct the image size and use power transformation to enhance the image contrast;

[0086] Step 3: Adding marker points to the preprocessed image. The specific steps of step 3 are as follows:

[0087] Select 6 points on the femur where the curvature of the contour curve changes significantly as marking points, and select 3 points on the tibia where the curvature of the contour curve changes significantly as marking points. The marking diagram is as follows: Fig.15 As shown, the point set of the i-th picture is represented as S i , the coordinates of the jth point of the i-th X-ray image are Among them, i=1,2,3,4,5; j=1,2,3......9.

[0088] Step 4: Perform image registration based on the added markers. The specific steps are as follows:

[0089] Step 4.1: Keep the points of each image relatively unchanged and align all images to the first image.

[0090] Step 4.2: Place point P on the femur i (i=1,2……6) for registration, with the 0° mark point as the point set, the registration error is Loss, and the formula used is as follows:

[0091] in

[0092] Step 4.3: Use the third point of each image as the origin to establish a coordinate system. There are three parameters in the registration process: the translation in the x-axis direction The amount of translation along the y-axis Angle of rotation around the origin θ i , expressed by a coordinate transformation matrix, each point set undergoes coordinate transformation, and the coordinate transformation matrix and coordinate transformation are as follows:

[0093]

[0094] Step 4.4: Taking the registration error Loss as the objective function, θ i ,t x ,t y To optimize the variables, There are 12 variables in total, and the constraints are st. The constraints used are as follows:

[0095]

[0096] Step 4.5: Select an optimization algorithm to solve the target programming problem, save the optimal variables solved, and visualize the aligned point set. Fig.16 The following is the effect diagram after registration.

[0097] Step 5: Calculate the instantaneous center curve of the knee joint based on the registered image. The specific steps of step 5 are as follows:

[0098] Step 5.1: Calculate P using the cubic spline interpolation method i 7 , P i 8 , P i 9 The motion trajectory L composed of (i=1,2,3,4,5) 7 , L 8 , L 9 .

[0099] Step 5.2: Calculate the instantaneous rotation center of the femur and tibia at five moments. One instantaneous rotation center I can be calculated for each image. i (x c ,y c ), points 7, 8, and 9 can be combined in pairs to calculate 3 instantaneous rotation centers for each image The normal slope of points 7, 8, and 9 on the curve in the i-th image is recorded as Where jk = 78, 79, 89, and the average is taken. The specific calculation method is as follows:

[0100]

[0101] Step 5.3: By I i The coordinates of the cubic curve L0 are changed to find the instantaneous center curve L of the knee joint. The curve used is a curve within a limited range, in the shape of a "J", L0: y = ax 3 +bx 2 +cx+d, where the parameter constraints and the range of the curve are as follows: in

[0102] Step 5.4: The optimization objective of the design curve L is dist represents the distance between two points, where Q i The coordinates of in And r i for The i-th element in the vector r is the angle at which the X-ray image is taken, not limited to the five angles mentioned above. The schematic diagram of the optimization function is as follows: Fig.17 shown.

[0103] Step 5.5: Select an optimization algorithm to solve the decision variable X = [a, b, c, d] to determine the equation of the curve L and solve the instantaneous center result curve of the knee joint Fig.18 shown.

[0104] Step 6: Calculate the length of each rod of the four-bar mechanism. The specific steps of step 6 are as follows:

[0105] Step 6.1: Design a cross-four-bar linkage, with design inspiration as follows Fig.12 As shown, Fig.11 As shown, the lengths are l1, l2, l3, and l4 respectively. The rod length constraints are set. The specific constraints are as follows:

[0106]

[0107] Step 6.2: Take 10 points evenly on the knee joint instantaneous center curve L. ci (x ci ,y ci ), the instantaneous center curve of the mechanism is composed of intersection points, and the instantaneous center L of the four-bar mechanism when the angle between l2 and l1 is α ci (x ci ,y ci ), where i = 1, 2, 3...10, the value of α is Take 10 values ​​evenly, L ci (x ci ,y ci ) is solved by the six-variable linear equation system. The specific calculation method is as follows:

[0108]

[0109] Step 6.3: Define the objective function That is, the mean square error of the distance between the instantaneous center curve of the knee joint and the instantaneous center estimation of the rod calculation. The intersection of rod 1 and rod 2 is taken as the origin, and the whole mechanism rotates around the origin by γ. The decision variable is X = [γ, l1, l2, l3, l4], and the optimization algorithm is used to solve all rod lengths.

[0110] Step 7: Set the solved rod length as the parameter corresponding to the actual rod.

[0111] The above is only a preferred embodiment of the present invention. Under ideal conditions, the instantaneous center curve of the knee joint can be accurately obtained by taking two angle X-ray images. The present invention is shown above with appropriate examples, but it is not used to limit the invention itself. Compared with the existing exoskeleton design, the present invention is fast, has clear design parameters, is lightweight, and has reliable results.

[0112] It is to be understood that the present invention is described by some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the scope of protection of the present invention.

Claims

1. A knee joint cross four-bar exoskeleton, comprising a thigh component, a shank component, a shank-shank connecting component and a driving component, wherein the thigh component and the shank component are connected by the shank-shank connecting component, and the driving component is used to drive the shank-shank connecting component to drive the thigh component and the shank component to move, characterized in that: The thigh component comprises a thigh component (10), the calf component comprises a calf component (7), the thigh-lower leg connecting component comprises an active connecting rod component (3) and a driven connecting plate (9), the thigh component (10), the calf component (7), the active connecting rod component (3) and the driven connecting plate (9) constitute a cross-hinged four-bar mechanism, the length of which is designed according to the collected bone X-ray image; the thigh component comprises a thigh baffle (1), a thigh component (10), a thigh bearing seat (13), a thigh connecting component (12) and a thigh fixing plate (2), the thigh baffle (1) comprises four symmetrically arranged waist holes, the thigh fixing plate (2) is fixedly connected to the thigh baffle (1) via the waist holes, The thigh component (10) and the thigh baffle (1) are fixedly connected via a thigh connecting member (12); the thigh bearing seat (13) is fixed on the thigh component (10); the thigh fixing plate (2) is fixed on the thigh; during installation, the thigh component is fixed relative to the thigh; the thigh component (10) has two arc-shaped contours, namely, a thigh component arc A (101) and a thigh component arc B (102); the thigh component arc A (101) is tangent to the rounded corners at both ends and has a length of 80 to 120 mm; the thigh component arc B (102) is tangent to the rounded corners at both ends and has a length of 25 to 60 mm; the calf component comprises a calf component (7), a calf baffle (4), a calf connecting member (6), a shaft sleeve (14), and a calf bearing seat (15), a calf optical axis (16), a calf fixing plate (5), the calf baffle (4) comprising four symmetrically arranged waist holes, the calf fixing plate (5) being fixedly connected to the calf baffle (4) via the waist holes, the calf member (7) and the calf baffle (4) being fixedly connected via the calf connecting member (6), the calf bearing seat (15) being fixed on the calf baffle (4) and the calf member (7), the shaft sleeve (14) being connected to the calf bearing seat (15), the calf optical axis (16) being in the middle of the calf bearing seat (15), the calf fixing plate (5) being fixed on the calf, the calf member being fixedly fixed relative to the calf during installation, the calf member (7) having a calf member arc A ( 71) and a calf arc A (72), wherein the calf arc A (71) is tangent to the rounded corners at both ends and has a length of 30 to 50 mm, and the calf arc B (72) is tangent to the rounded corners at both ends and has a length of 35 to 60 mm; the thigh and calf connecting components include an active connecting rod (3), a driven connecting plate (9), and a pin (8), wherein one end of the active connecting rod (3) is mounted on the thigh component and the other end is mounted on the calf optical axis (16), and is positioned between the calf bearing seat (15) and the sleeve (14), wherein the driven connecting plate (9) is a rounded rectangular shape with four connecting holes formed around it and two large holes formed at both ends of the midline of the long side, and wherein the driven connecting plate (9) and the calf bearing seat (15) are connected via a pin (8).

2. The knee joint cross four-bar exoskeleton according to claim 1, characterized in that: The driving component comprises a worm gear reduction box (11) and a motor (17); the worm gear reduction box (11) is fixed on a thigh member (10) of a thigh member; the motor (17) is arranged above the worm gear reduction box (11); a rectangular notch is provided below the worm gear reduction box (11); the active connecting rod (3) is fixedly connected to an output shaft of the worm gear reduction box (11) through the rectangular notch (111); and the active connecting rod (3) can periodically swing in the rectangular notch under the drive of the motor (17).

3. A design method for a knee joint cross four-bar exoskeleton based on image registration as claimed in any one of claims 1 to 2, characterized in that: The steps include: Step 1: Take X-ray images of the femur with the femur fixed and the tibia bent at angles of 0°, 30°, 60°, 90°, and 120° under a medical X-ray machine; Step 2: Preprocess the acquired image data; Step 3: Adding marker points to the preprocessed image. The specific steps of step 3 are as follows: Six points on the femur where the curvature of the contour curve changes significantly are selected as marking points in turn, and three points on the tibia where the curvature of the contour curve changes significantly are selected as marking points in turn. The point set of the i-th image is represented as S i , the coordinates of the jth point of the i-th X-ray image are in i=1,2,3,4,5; j=1,2,3...9; Step 4: Image registration based on the added markers; Step 5: Calculate the instantaneous center curve of the knee joint based on the registered images; Step 6: Calculate the length of each rod of the four-bar mechanism; Step 7: Set the solved rod length as the parameter corresponding to the actual rod.

4. The design method based on image registration according to claim 3, characterized in that: The step 2 comprises the following specific steps: Step 2.1: Use computer programming language to convert the acquired DICOM format image data into JPG format data; Step 2.2: Use the scaling factor μ to correct the image size and use a power transformation to enhance the image contrast.

5. The design method based on image registration according to claim 3, characterized in that: The step 4 comprises the following specific steps: Step 4.1: Keep the points of each image relatively unchanged and align all images to the first image; Step 4.2: The points Pi (i = 1, 2...6) on the femur are registered, and the 0° mark point is used as the point set. The registration error is Loss, and the formula used is as follows: Step 4.3: Use the third point of each image as the origin to establish a coordinate system. There are three parameters in the registration process: the translation in the x-axis direction The amount of translation in the y-axis direction Angle of rotation around the origin θ i , expressed by a coordinate transformation matrix, each point set undergoes coordinate transformation, and the coordinate transformation matrix and coordinate transformation are as follows: Step 4.4: Taking the registration error Loss as the objective function, θ i ,t x ,t y To optimize the variables, There are 12 variables in total, and the constraints are st. The constraints used are as follows: Step 4.5: Select an optimization algorithm to solve the target programming problem, save the optimal variables solved and visualize the aligned point set.

6. The design method based on image registration according to claim 3, characterized in that: The step 5 comprises the following specific steps: Step 5.1: Use the cubic spline interpolation method to calculate The motion trajectory L composed of (i=1,2,3,4,5) 7 , L 8 , L 9 ; Step 5.2: Calculate the instantaneous rotation center of the femur and tibia at five moments, and calculate an instantaneous rotation center I for each image. i (x c ,y c ), points 7, 8, and 9 are combined in pairs to calculate 3 instantaneous rotation centers for each image The normal slope of points 7, 8, and 9 on the curve in the i-th image is recorded as Where jk = 78, 79, 89, and the average is taken. The specific calculation method is as follows: Step 5.3: By I i The coordinates of the cubic curve L0 are changed to find the instantaneous center curve L of the knee joint. The curve used is a curve within a limited range, in the shape of a "J", L0: y = ax 3 +bx 2 +cx+d, where the parameter constraints and the range of the curve are as follows: in Step 5.4: The optimization objective of the design curve L is i=1,2,3,4,5, dist represents the distance between two points, where Q i The coordinates of in And r i for The i-th element in the r vector is the angle at which the X-ray image was taken; Step 5.5: Select an optimization algorithm to solve the decision variable X = [a, b, c, d] to determine the equation of the curve L and solve the instantaneous center of the knee joint.

7. The design method based on image registration according to claim 3, characterized in that: The step 6 comprises the following specific steps: Step 6.1: Design a cross four-bar linkage with lengths of l1, l2, l3, and l4 respectively. Set the bar length constraints. The specific constraints are as follows: 45mm<l1<65mm 80mm<l2<120mm 70mm<l3<110mm 35mm<l4<60mm l2+l4≤l1+l3； Step 6.2: Take 10 points evenly on the knee joint instantaneous center curve L. ci (x ci ,y ci ), the instantaneous center curve of the mechanism is composed of intersection points, and the instantaneous center L of the four-bar mechanism when the angle between l2 and l1 is α ci (x ci ,y ci ), where i = 1, 2, 3...10, the value of α is Take 10 values ​​evenly, L ci (x ci ,y ci ) is solved by the six-variable linear equation system. The specific calculation method is as follows: Step 6.3: Define the objective function That is, the mean square error of the distance between the instantaneous center curve of the knee joint and the instantaneous center estimation of the rod calculation. The intersection of rod 1 and rod 2 is taken as the origin, and the whole mechanism rotates around the origin by γ. The decision variable is X = [γ, l1, l2, l3, l4], and the optimization algorithm is used to solve all rod lengths.

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