Static Optimization "states" output different than input motion

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User avatar
Ryan Byrne
Posts: 28
Joined: Thu Jan 22, 2015 8:33 am

Static Optimization "states" output different than input motion

Post by Ryan Byrne » Fri Jul 07, 2017 3:12 am

Hello,

After successfully (although somewhat slowly) running Static Optimization on my model, I have realized that the generated "states" output motion is different that the input motion from Inverse Kinematics. It appears the coordinates defined with respect to time, as shown below, remain locked at their default value. However, during the execution of Static Optimization, the motion looks fine. Given that it is static optimization - with time independant results - it makes sense that this is occuring only at these joints. However, I am unsure whether my resulting forces at these coordinates are affected. Will these forces correspond to the generated "states" motion or the correct motion used as an Input from IK? I imagine a way around this could be to remove the SimmSplines from the model for the Static Optimization process, but I would like to avoid this if possible.

Any help would be appreciated.

Code: Select all


<Coordinate name="L5_S1_FE">
	<motion_type>rotational</motion_type>
	<default_value>0.31007</default_value>
	<default_speed_value>0</default_speed_value>
	<range>-2 2</range>
	<clamped>true</clamped>
	<locked>false</locked>
	<prescribed_function>
		<SimmSpline>
			<x> 0.033333 0.066667 0.1 0.133333 0.166667 0.2 0.233333 0.266667 0.3 0.333333 0.366667 0.4 0.433333 0.466667 0.5 0.533333 0.566667 0.6 0.633333 0.666667 0.7 0.733333 0.766667 0.8 0.833333 0.866667 0.9 0.933333 0.966667 1 1.03333 1.06667 1.1 1.13333 1.16667 1.2 1.23333 1.26667 1.3 1.33333 1.36667 1.4 1.43333 1.46667 1.5 1.53333 1.56667 1.6 1.63333 1.66667 1.7 1.73333 1.76667 1.8 1.83333 1.86667 1.9 1.93333 1.96667 2</x>
			<y> 0.189744 0.186954 0.186081 0.187041 0.189478 0.192876 0.196668 0.200348 0.203614 0.20637 0.208637 0.210522 0.212255 0.214124 0.216377 0.219183 0.222634 0.226695 0.231178 0.235838 0.240425 0.244672 0.248315 0.251255 0.253524 0.255173 0.256262 0.25696 0.257651 0.258816 0.260817 0.263838 0.267837 0.272567 0.277719 0.283031 0.28837 0.293675 0.298894 0.303899 0.308526 0.312739 0.316638 0.320399 0.324202 0.328203 0.332524 0.337244 0.342314 0.347604 0.353075 0.358718 0.364571 0.370687 0.377083 0.383695 0.390374 0.396936 0.403253 0.40922</y>
		</SimmSpline>
	</prescribed_function>
	<prescribed>true</prescribed>
</Coordinate>

User avatar
Emily Hubbard
Posts: 7
Joined: Sat May 06, 2017 2:17 pm

Re: Static Optimization "states" output different than input motion

Post by Emily Hubbard » Wed Jul 19, 2017 10:59 am

Hi Ryan,

I have a similar question about keeping mtp and subtalar angles locked during IK. When I unlock the coordinates, knee joint angles vary slightly, but the feet on the model appear much more abnormal. I'm wondering if it's better for realistic knee joint angles to have locked or unlocked mtps and subtalars. Did you find an answer to your question? I think any related information could help.

Emily

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