I was initially tasked with calculating the kinetic energy output of gait motion, which I approached in 6 parts. I dealt with two segments, the thigh and the leg (separated by the knee), each with three energy values to obtain: translational energy, rotational kinetic energy, and potential energy. I actually started with the second type first, as I knew it would prove to be the most difficult to calculate of three.
I started with the RKE of the leg. Since the hip has very little movement throughout the walking motion, I assigned it as a fixed point in order to find the rate of angle change. I separated the motion into several cycles, and worked with each one individually. Using trigonometry, I created an "isosceles" triangle by taking the frame with the widest stance (since the two legs of the triangle are actually the length of the leg segment) and assumed that angle to be the total angle change. I did this for each cycle, plugged it into RKE after finding each trial's moment of inertia, and found the average of all the trials. The value ended up being below 1 J, which discouraged me (even though RKE is supposed to be smaller), and because of this, I decided to neglect the RKE of the thigh since it would have been much more difficult to calculate.
The next-most difficult energy to calculate was potential energy of each segment. I found the coordinates of the center of mass of each segment, and measured its potential energy at each time frame by finding the distance (or height) from the position of the COM at that time frame from the absolute minimum location of the entire motion. I took the sums of these values to obtain my total PE results for each segment.
Lastly, translational energy. This was simply mv^2, and I found the velocities of each segment by putting their distances traveled over time. This too, surprisingly, yielded pretty low values.
Looking back I definitely would have approached the calculations differently. I averaged all the RKE values from the start, when in hind sight should have done it like with the PE values: calculating the RKE at each time frame and taking the sum of all those energy values. I think that's why I may have gotten very small energy amount for RKE and TE.
After the math, I attempted to use the coordinates and values I had from using the Kinovea video analysis software in order to build a walking model on the computer. I went with Wolfram's Systemmodeler, but after a couple unsuccessful weeks, I got no where with the program. Simply put, Systemmodeler was just out of my and Max's reach and it required a very comprehensive foundation of mechanical engineering and modeling.
Luckily, Mr. Lin sent me a link to an OpenSim model developed by a Stanford researcher. I have been playing around with it for the past two days, and it is certainly far more complex and intricate than what I had envisioned. But adding parameters could allow me and Max to observe the effects which adding mass of the knee has on the gait motion and energy output.
The biggest problem is, obviously, time. Personally, I would rather just get straight into the building and wiring of the generator rather than work with computer models, and with the end of the year approaching quickly, that made be what needs to happen.
Potential Energy Calculations
Rotational Kinetic Energy Calculations
Translation Energy/Final Calculations
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