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- In the Input pane, select "Loaded motion" and use the "ik trial" motion from the previous step.
- Check the box to filter the coordinates and set the cutoff frequency to 6 Hz.
- Set the time range to between 0.5 and 1.5 seconds.
- Specify an output directory (e.g., <YourWorkingDir>\Stance\ID).
- Select the External Loads tab and check the External Loads box.
- Edit the External Loads settings by clicking the pencil icon to the right of the textbox.
- Select leg69_stance_grf.mot as the "Force data file". This file describes the force applied at the foot's center of pressure (CoP).
- Select leg69_IK_stance.mot as the "Kinematics for external loads".
- Select "Filter kinematics" and specify a cutoff frequency of 6 Hz.
- Add the forces listed in the motion file by clicking the "Add..." button.
- Provide a name (e.g., "Right_GRF").
- Apply the force to the calcn_r body.
- Check "Applies Force" and select "Point Force".
- Force Columns: select "ground_force_vx" from the first drop-down box; "ground_force_vy" and "ground_force_vz" will be selected automatically.
- Point Columns: select "ground_force_px" from the first drop-down box; the corresponding "y" and "z" entries will again be populated automatically.
- The GRF free moment is a torque, so check "Applies Torque".
- Torque Columns: select "ground_torque_x", "ground_torque_y", and "ground_torque_z".
- The GRF and CoP are both expressed in the ground (laboratory) frame, so click OK.
- Click "Save..." and enter a filename for the External Force input (e.g., leg69_right_GRF.xml).
- Click "Save..." and enter a filename for the ID settings (e.g., leg69_Setup_ID_stance.xml).
- Run the tool, then close the Inverse Dynamics Tool window.
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- Re-run RRA with the adjusted model making sure to close and re-open the RRA Tool to ensure the most recent adjusted model is always used.
- Adjust the pelvis COM and mass in accordance with the RRA Tool output messages.
- Plot your tracking errors from the RRA/leg6dof9musc_pErr.sto file. Verify whether the errors are reported in radians or degrees by opening the file in a text editor and reading the header.
- Increase the tracking task weights for coordinates that show poor tracking in the leg69_Tracking_Tasks.xml file.
- Decrease the tracking weight for coordinates that are within 1 degree (0.017 radians), since the optimizer can use these coordinates to reduce residuals.
- Iterate until the requested change in pelvis mass is less than 1 kg and the residual forces and coordinate errors follow the suggested thresholds in the table at the bottom of the Getting Started with RRA page. (Hint: try a pelvis mass of 56kg)
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- Ensure you have loaded your final model from the previous section on RRA.
- From the Edit menu, select "File (.xml)..." and open the leg69_RRA_residuals_motors.xml file, which contains information on the residual and motor actuators necessary for CMC.
- Reduce the optimal force of the joint motors Coordinate Actuators that actuate the ankle, hip, and knee to 1 so that they are penalized during CMC and muscles are favored to generate joint moments.
- Save the edited actuators as a new file (e.g., leg69_CMC_residuals_motors.xml).
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