Design of knee joint variable stiffness protector based on lower limb biomechanical characteristics

doi:10.11996/JG.j.2095-302X.2024051084

Abstract

Abstract:

In order to meet the growing demand for wearable sports protective gear products in the context of national fitness movement and to address the problems of insufficient protective performance and low matching degree of sportswear in existing prefabricated protective gears, a new method was developed to analyze the skin deformation and curvature pressure distribution of the lower limbs during movement. First of all, key technologies and methods such as reverse engineering and clothing pressure calculation theory were employed to collect and qualitatively and quantitatively analyze key parameters like skin deformation and protective gear pressure during movement. This analysis revealed the regional pattern changes in lower limb skin deformation and curvature pressure distribution, leading to the construction of a functional zoning model for human knee joint protective gear. Secondly, the design of knee joint variable stiffness brace partition structure was completed according to different partition regions. The finite element simulation method was then used to construct a finite element model of the knee joint-guard, allowing for the comparative analysis of contact pressure distribution laws under various wearing conditions of multiple groups of guards. Finally, combined with the pressure and electromyography acquisition experiments of the guards, it was verified that the knee variable stiffness guards can optimize the pressure distribution of the knee joint, improve the wearing degree of fit, and enhance the athletic performance.

Key words: knee joint, variable stiffness protector, sports biomechanics, reverse engineering

CLC Number:

TS941.727

TAN Kun, WANG Xupeng, ZHAO Jiaxin, HUANG Yuzhe, LI Xu, LI Jiachen. Design of knee joint variable stiffness protector based on lower limb biomechanical characteristics[J]. Journal of Graphics, 2024, 45(5): 1084-1095.

Figures/Tables 31

Fig. 1 Experimental action breakdown diagram

Fig. 2 Definition of experimental area and grid division ((a) Mesh division diagram of knee joint; (b) Longitudinal midpoint of knee circumference line)

Fig. 3 3D scanning of knee joint point cloud data ((a) Knee joint scanning image; (b) Knee joint marker stickers)

Fig. 4 Scanning model processing and data extraction methods ((a) Scan the model; (b) Data extraction process)

Fig. 5 Distribution map of stretching contraction grid on the skin of the right knee of the lower limb

Fig. 6 Experimental data processing process

Fig. 7 Draw tangent lines and import them into GH

Fig. 8 Extracting knee joint feature cross-sectional lines

Fig. 9 Optimization and fitting of knee joint characteristic cross-sectional lines

Fig. 10 Building knee joint protection coverage

Fig. 11 Extraction of curvature values for type value points

Fig. 12 Color scale diagram of pressure values at type points

Fig. 13 Curvature pressure distribution cloud map of models at various angles ((a) Front; (b) Outside; (c) Back; (d) Inside)

Fig. 14 Functional zoning diagram of knee joint protectors ((a) Front; (b) Back)

Table 1 Basic parameters of yarn

纱线原料	纱线细度/tex
高弹涤纶丝	16.67/96 f (150 D/96 f)
高弹氨纶丝	7.78/100 f (70D/100 f)
橡筋纱	124.44 (1 120 D)

Table 2 Knee joint protector size chart/mm

尺码	膝关节护具(宽度)			膝关节(围长)
尺码	下围	膝围	上围	小腿	膝围	大腿
M	15	14	17	36~39	30~35	41~44
L	17	16	19	40~43	36~40	45~48
XL	18	17	21	44~48	41~45	48~52
L_x	19	16	17	42	40	48

Fig. 15 Size design of knee joint protectors ((a) Positive; (b) Side view)

Fig. 16 Qualitative zoning optimization design diagram for stiffness of joint protective equipment fabric ((a) Protective gear zoning design; (b) Side support of protective gear design; (c) Design of density reduction in the popliteal fossa area)

Fig. 17 Knee joint and protective gear model ((a) Uniform knitted protective gear; (b) X pressurized protective gear; (c) Knee joint stiffness protective gear)

Table 3 Material properties of sports protective equipment

项目	材料1
成分	66%锦纶、18%聚酯纤维、16%氨纶
弹性模量/MPa	0.429 4
泊松比	0.34
密度/t·mm^-3	9.86e-10

Table 4 Materials properties of knee joint bones, muscles, and soft tissues

膝关节	弹性模量/MPa	泊松比	密度/t·mm^-3
骨骼	7 300	0.3	1.90E-10
肌肉软组织	0.15	0.45	1.10E-10

Fig. 18 Mesh model ((a) Bones; (b) Muscle and soft tissue; (c) Protective gear)

Table 5 Surface contact pressure distribution of knee joint skin/MPa

护具	压力	前侧	右侧	后侧	左侧
护具A
护具B
护具C

Table 6 Stress distribution of knee joint protectors/MPa

护具	应力	前侧	右侧	后侧	左侧
护具A
护具B
护具C

Table 7 Stress distribution of knee joint surface/MPa

护具	应力	前侧	右侧	后侧	左侧
护具A
护具B
护具C

Table 8 Surface displacement distribution of knee joint skin/mm

护具	位移	前侧	右侧	后侧	左侧
护具A
护具B
护具C

Fig. 19 Wearing effect picture of protective equipment ((a) Gear A; (b) Gear B; (c) Gear C)

Fig. 20 Experimental process diagram ((a) Location of pressure measurement points; (b) Pressure collection at protective gear measurement points)

Fig. 21 Pressure test line chart

Fig. 22 Experimental process diagram ((a) Front electrode sticking; (b) Right electrode sticking; (c) Rear electrode plate pasting; (d) Lower limb electromyographic signal acquisition)

Fig. 23 Changes in electromyographic data of lower limb muscles ((a) MAV; (b) RMS)

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