Team Members

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Opensim Model:

Description

This project focuses on using inertial measurement units (IMUs) in the "wild," meaning using IMUs to capture state-specific data in a non-laboratory and non-controlled environment. IMUs are generally used to capture linear acceleration and angular velocity data using gyroscopes and accelerometers. Through some integration, these linear accelerations and angular velocities can then be used to determine the position of the IMU,which provides a useful way to capture biomechanical data such as joint angles and body positions. However, one of the largest issues with capturing real-time position data is the noise apparent not only in the environment, but also in the sensors themselves. Using the integration method to determine positions and joint angles introduces drift error - a systemic artifact due to the integration that causes the data to shift towards one direction. Existing studies have shown that applying a Kalman filter could ameliorate the effects of this drift. 

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Side note: The way Vasavada model works, there's a function between each joint at angles. If For example, if you adjust a joint by an angle of 1, the other one would adjuts the otehr one by another angle would adjust by different factor. To make it a two link model, you we could reduce the weight to 0. We will try to , which could limit the number of dependent variables. XSENS into XSENS model vs XSENS into Vasavada model. Independent vs dependent coordinates for angles. 

In order to input the XSens IMU data into OpenSim, we used a MATLAB script to write a .mot file that controls pitch2 and pitch1, which corresponds to the movement of the C7T1 and C1head joint in the sagittal plane respectively. We had to change the .osim file available from Vasavada to remove the constraints placed on the C1Head and C7T1 joints as the joint angles obtained from the IMUs exceeded the range of motion the model could handle, resulting in clipping. Removing these constraints removed the errors from clipping. From there, the Analyze tool was used to obtain the BodyKinematics of the OpenSim model, where we are able to obtain the positions of the skull and each cervical spine. Using the same calculations from the knee joint as stated above, we used the positions of the T1, C1, C3, C7, and skull to obtain three joint angles. The T1 was constant and used as a reference point to represent the torso, which did not move in the biomechanical model. The joint angle between T1, C1, and C3 was obtained and named C1. The joint angle between C1, C3, and C7 was obtained and named C3. The joint angle between C3, C7, and skull was obtained and named C7. 

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 Vasavada, Li, and Delp. "Influence of muscle morphometry and moment arms on the moment-generating capacity of human neck muscles." Spine, 1998.

 Young, Alexander D. "Wireless realtime motion tracking system using localised orientation estimation." (2010).

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