Spring Validation Experiment
Sensing Subsystem Validation
Requirements to fulfill:
M.P.1 Measure user’s pelvic velocity within ± 0.3 m/s
M.P.2 Measure user’s pelvic orientation within ± 10°
M.P.3 Measure user’s hip joint motion within ± 10°
Procedures:
1. Mount IMU vertically on a box. Put the box on a treadmill which is moving at a specific velocity. Record measurements from the IMU. Read velocity from the sensor data pre-processing algorithm. Determine whether the calculated velocity matches the treadmill speed.
2. Secure the aluminum prototype onto the user. Have the user walk on the ground and record measurements from the IMU. Compare the velocity captured by VICON motion system to the IMU readings.
3. Incline the exoskeleton to a certain angle, and compare the orientation reading of IMU 18
sensors to the known incline angle.
4. Rotate joint by hand to specific angles using a protractor. Verify the angle readings of the associated motor encoder. Repeat for all four motors on the exoskeleton.
Processing Algorithm Validation
Requirements to fulfill:
M.P.4 Determine the correct leg in swing 70 % of the time
M.P.5 Determine desired foot placement within 100 ms after taking off
M.P.6 Plan optimal leg trajectory within 120 ms after taking off
M.P.7 Determine compensatory torque response within 150 ms after taking off
Procedures:
1. Have a person wear the intermediate prototype of the exoskeleton and take 10 steps on the treadmill. Measure ground reaction forces with the treadmill to determine when each leg is in swing or stance. Determine if the swing leg detected by the algorithm matches the ground reaction force measurements for at least 7 out of the 10 steps.
2. Call the clock function to record the duration of each algorithm.
Actuation Subsystem Validation
Requirements to fulfill:
M.P.8 Apply torque to achieve desired trajectory with <0.2 m error between the desired and actual trajectory
Procedures:
1. Test the motors independently: Feed an input rotation angle to the motors through the com- puter and read the output rotation angle from the encoders. Match the input with the output. Repeat procedure for all four motors in the system.
Note: This experiment is not designed to completely validate the requirement, and is considered as a step towards final validation that will take place during the Fall.