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External forces (such as ground reaction forces) in OpenSim are contained in a .mot file. The header of the selected force (.mot) file is the same as that expected by OpenSim tools (__40__Motion (.mot) Files).
For the ground reaction forces used by the gait model, the column labels are shown below (for 2 external forces force1, force2, torque1, torque2):
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The data previewer expects groups of 6 columns for a force of the form “body”_”ForceName”_{vx, vy, vz, px, py, pz}, where vi corresponds to each component of the force and pi corresponds to each component of the location of the force (e.g., center of pressure) and 3 columns for a torque of the form “body”_”TorqueName”_{x, y, z}, corresponding to each component of the applied torque. Note that this naming convention is only necessary for previewing purposes. OpenSim tools employ a new an External Loads user interface enabling you to specifiy any specify an arbitary number of forces, along with points of application, or torques to a model during any simulation or analysis.
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