How to Use the IMU Placer

Owned by Ayman Habib
Last updated: Mar 24, 2024 by Henry Kwong

The topics covered in this section include:


To launch the IMU Placer Tool:

Select Tools → IMU Placer from the OpenSim main menu bar.

The Settings pane is used to specify parameters related to the experimental IMU data. 

The IMU Placer Tool window, like all other OpenSim tools, operates on the current model. The name of the current model is shown in bold in the Navigator window. Any model can be made the current model by right-clicking on its name and selecting Make Current. See Opening, Closing, and Using the Navigator Window for information on opening models and making a particular model current.


The Control Panel

At the bottom of all the Tool dialog windows are four buttons, located in what we call the Control Panel.

  • The Load and Save buttons are used to load or save settings for the tool. 
  • The Run button starts execution. 
  • The Close button closes the window.
  • The Help button takes you to the relevant section of the User Guide.

The Settings Pane

The dialog contains one pane composed of two sections: Data Transformation section and the Heading Correction section, both described below:

  • IMU Orientation Data & Transformation: Typically users select an orientation file containing collected sensor orientation at the default model pose (called placement pose). This section is also used to convert orientation data from the sensor/IMU coordinate system (typically based on magnetic north and gravity) to the OpenSim default world coordinate system (Y-up, X-forward). The transformation is specified in space fixed Euler angles that are displayed in degrees (in the dialog) and can be incremented/decremented by 90 degrees using the spinners
  • Heading Correction (Optional):  The user has the option to specify a heading direction to correct for the fact that a sensor may not exactly line-up with the forward direction of the model (+X of the base segment of the model e.g. pelvis). If specified, the user selects the name of the sensor and the corresponding axis that should align with the forward heading direction. If the IMU axis is left blank (from the drop down) then no heading correction is performed.

Executing the tool using the "Run" button, results in a new model with IMUs placed on the corresponding segments. This model is added to the application and can be used to solve IMU based Inverse Kinematics.

Next: Settings file and XML Tag Definitions

Previous: How IMU Placer Works

Home: IMU Placer

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