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We worked with the program OpenSim to model a human skeleton with certain muscles. We learned the controls and were told to maneuver the model to simulate how a human body would have to be changed.
March 24, 2025:
This was our first day working with OpenSim. We played around to figure out the controls at first. Then we were told to make the model have a knee up and its foot pointed down.
OpenSim Tutorial 1
March 26, 2025: We worked through this site (link here). We first completed section II: Musculoskeletal Model of the Lower Extremity. Below are screenshots of the work through the beginning of the section.
The picure to the left shows the display of the muscle groups. I switched to the navigation tab and opened the model's properties to get this list. Here, I selected the right knee muscle group, labeled as "R_knee_ext", right clicked, pressed display, and selected show only. The picture to the right shows this outcome.
Then I was tasked with flexing the knee fully. I changed to the coordinates tab and pulled the right knee angle slider all the way back. It is outlined in a grey box in the picture.
Below are the questions I was tasked with answering:
Degrees of freedom
a. Use the Coordinates panel to view the degrees of freedom of the model. How many degrees of freedom, in total, does the model have? List the degrees of freedom of the right leg.
Answer: 7 for one leg, 23 for the entire model. In the right leg there is: hip rotation, hip abduction, hip flexion, knee angle, ankle angle, subtalar angle, and metatarsophalangeal joints angle (mtp).
b. All models are approximations. Compare the degrees of freedom in the model to the degrees of freedom in your lower limbs. Give an example of a joint motion in the model that has been simplified. Give an example of a motion that is not included in this model.
Answer: The ankle has more degrees on motion than simply up and down because it can turn to the side.
(Skipped)
Soccer Kick Contest
March 31, 2025: For this challenge, we were tasked with optimizing the max speed for a soccer kick model, using open-source software OpenSim. I worked with Angelina Yang on this assignment (her digital portfolio is linked here). We we able to adjust parameters and the coordinates of joints in order to move the model and increase the maximum speed of the ball. Below is a list of the aspects of the model we were allowed to change. Below that is the Google Sheet we used to track the major changes we made and the results of those changes.
Parameters (0-9000N):
Hamstring muscle force
Rec Fem Muscle Force
Soleus Muscle Force
Tibialis Anterior Muscle Force
Turn Force
Coordinates:
Turn
Hip_flexion
Knee_angle
ankle_angle
Ball (x)
Ball (y)
Ball (z)
This is a view of the soccer kick model.
This is what human leg muscle groups actually look like and what the model is simulating.
In order to achieve optimal settings, we first started by changing aspects of the parameter section. We found that small adjustments worked best as any big changes often resulted in decreases of speed. Initially, we went down the list of parameters mentioned earlier to discover the most optimal force on each specific muscle. This method, though it led to an increase in ball speed, didn’t prove to be the most effective method. By changing the parameters of a few muscle groups at a time, we found that the paired changes resulted in bigger speed increases. Below is a view of the parameters window.
We then moved to changing aspects of the coordinate section. Coordinates in this case means the initial positioning of our model. We initially changed the angles of the hip, knee, and ankle. We then moved on to the turn portion, though its default setting proved to be most efficient. After changing the muscle groups to the best of our ability, we finally adjusted the positioning of the ball. This would be the initial placement of the ball. It is justified to move the ball as in a real kick, you may place the ball wherever.
As Honors students, we were finally allowed to adjust the properties of the muscle groups. We went into the navigator, opened the forces tab, and could change the muscle properties of each of the listed muscle groups. We made adjustments to the muscle properties, increasing the max_contraction_velocity for rect_fem_r to 120 and the soleus_r to 90.
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