Muscle Points (Fixed, Via, and Moving)

[Connor Stapp]

I've been working with muscle points (Moving, Via, and Fixed) and to see how they work, I modified the Tug_of_War.osim model so that the block drops and is able to make contact with the floor. First, I placed the box in the "air" with simple point to point muscles without any extra points in the middle as seen in the first picture below.

Figure_2.JPG (27.37 KiB) Viewed 230 times

When the model was simulated, the box dropped and made contact with the floor as seen below. I also graphed the fiber length of each muscle to see how they changed over time, which can also be seen below.

Figure_1.JPG (26.69 KiB) Viewed 230 times

Figure1and2Graph.png (12.29 KiB) Viewed 230 times

Once I finished testing this model, I added a moving point to the muscle on the right. When I simulated the model, I got the following results:

Figure_4.JPG (27.34 KiB) Viewed 230 times

Figure3and4Graph.png (14.49 KiB) Viewed 230 times

I'm not completely sure why I'm getting different results just because of an extra point added to a muscle. Can anyone explain why I might be getting different results?

[Thomas Uchida]

I'm not completely sure why I'm getting different results just because of an extra point added to a muscle. Can anyone explain why I might be getting different results?

In general, changing a muscle's path will change its fiber length. You can find information about the muscle models on the "Muscle Model Theory and Publications" page in the Confluence documentation (http://simtk-confluence.stanford.edu:80 ... blications).