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An Excel file with demographic, marker, and force data can be downloaded here, and Matlab files here and here.
In this problem, we will conduct a planar analysis and use the “6 marker set,” a simple marker set that has been used in various biomechanics labs. With this marker convention, a reflective marker is placed on the iliac crest, the greater trochanter (the hip), the lateral epicondyle (the knee), the lateral malleolus (the ankle), the calcaneus (the heel), and the 5th metatarsal (bone by the little toe). The location of these markers can be seen below.
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f^{\prime\prime}(t_i) \approx \frac{f(t_i+1)-2f(t_i) +f(t_i-1)}{ ( \Delta t^2t) ^2} |
4. Numerically differentiate your knee and ankle position data to obtain the appropriate linear velocities and accelerations for these markers. You don’t need to find the velocities and accelerations for the first and last data points.
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5. The moment of inertia and center of mass of each segment is needed to perform inverse dynamic analysis. Anthropometric information from Winter (1990) can be used to calculate this information. Using the data in the table below, calculate the mass of the segment, the length of the segment, the position of the center of mass (COM) in the segment, and the moment of inertia about the center of mass for the foot, shank (tibia and fibula), thigh (femur), and HAT. Assume linear segments as shown in the figure.
Segment | Segment mass / Total mass | Segment length / Height | COM position from proximal end of segment / segment length | Radius of gyration about COM / segment length |
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Foot | 0.0145 | 0.055 | 0.500 | 0.475 |
Shank | 0.0465 | 0.246 | 0.433 | 0.302 |
Thigh | 0.1000 | 0.245 | 0.433 | 0.323 |
HAT | 0.6780 | 0.470 | 0.626 | 0.496 |
The height of the subject is 1.7526 m, and the mass of the subject is 66.7 kg.
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Moment of inertia of a segment is defined as:
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Radius of gyration should be determined from the information given.
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