Dynamic foot model

Abstract

The development of footwear design is influenced by fit and comfort requirements. This involves judging a pair of shoes not only based on esthetic,but based on support, material and the matching between shoe shape and foot shape. As one of the most complicated and the most essential structure of the human body, foot shape varies widely.Hence, the foundation of making the proper shoes is to obtain enough knowledge of foot shape and its deformations. Moreover, the foot shape varies widely in dynamic situations and due to the complexity of obtaining dynamic foot shape it is mostly neglected in the footwear industry. A model of the dynamic foot shape with detailed information about deformation and range of motion could provide essential information for footwear design. The aim of this research is to develop a dynamic foot model with foot deformation to complement the footwear design and production. To obtain the relevant information two experiments are designed and conducted. First, a trial experiment with three participants each 10 trials was to observe the gait cycle was conducted. The individual trajectory for nine landmarks were presented and compared.The average motion in 2D coordinate system was also generated. Results show differences in motion pattern between foot joints while walking. The hind foot and the forefoot would rotate at different time in the swing phase.Moreover, from one heel strike to another heel strike, there is lateral medial swing in the foot as previous researchers have mentioned. Furthermore, the change in several angles was calculated while walking. Also a high-speed camera recorded the profile in the stance phase. This provides basic information for the foot shape changes. The main experiment was then conducted to find detailed foot deformation in static and simulated dynamic settings.In the second experiment, the 3D foot shape was scanned at different settings (heel height, plantarflexion-dorsiflexion,inversion-eversion,simulated walking position). The Kinect scanner was used to obtain 3D foot shape together with texture information.Fifty subjects were recruited to participate in the experiment. The analyzed parameters include the surface created by triangulated landmarks, distance between landmarks,and angles created based on landmark locations.In total 37 landmarks were extracted, and 56 triangular faces created to represent the 3D foot surface.93 edges (line between landmarks) were calculated to obtain the lengths, and 11 angles were selected to represent the foot shape in 3D. Results indicate that the inversion and eversion settings have small changes in foot shape. On the other hand,heel height, plantarflexion-dorsiflexion,and simulated walking settings all showed significant influence on foot surface deformation. Based on landmark distance analysis, the most deformed areas include the foot dorsal,the lateral of ankle and the back of Achilles tendon.Relatively, the medial side had less variation.In the simulated walking most of the surface region changed at different setting. As for the 16 angles representing the plantarflexion and dorsiflexion at the ankle joint,instep position,and forefoot position,and eversion and inversion at the ankle joint,instep position, and forefoot position were considered. For the angle change,inversion and eversion postures had less shape deformation. While the heel height elevation and the plantarflexion-dorsiflexion postures had significant influence in the angle changes and were represented by regression equations with high R2 value.The simulated walking analysis showed significant changes in angles, implying the need for dynamic shape analysis of the gait cycle.In this study the investigation on the dynamic foot was carried out.Results indicate changes in distances between landmarks and angles at different settings. Regression equation were developed to create prediction model of foot deformation. Several improvement and limitations of the study has also been discussed. In conclusion, foot shape deformation is important for design of better fitting footwear, especially for high heel shoes and sports shoes,and further research is needed to develop accurate 3D shape prediction models for dynamic foot.