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Forced Based Prosthesis Controller

Weekly Meeting 13 (3/25/19)

Posted by on Monday, March 25, 2019 in Notebook.

  • SNR
    • Recalculated baseline without the co-contractions and this raised all of the values
  • Initial contraction classifier
    • Recorded raw EMG,
    • Tested using:
      • pure extensor test
      • pure flexor test
      • partial extensor/flexor
    • Tustin approximation is working well
      • Includes a discrete integral in the calculation allowing us to smooth as we go
      • Helps with the flow and speed of the code
    • Seeing good difference between muscles
    • Calculated MAV at different contraction levels
    • Can use either 3rd/4th degree polynomial or piecewise function
      • 3rd order is probably fine, but shouldn’t go higher (maybe 4th order)
      • The problem with higher degree polynomials is with the edge conditions due to curvature
    • Need more data points (currently only taking average of a few)
    • Currently using percent contraction as measurement
      • Since we’re not using resistance, percent contraction is not the same as angle
    • To open a hand, ideally the prosthetic is set so it does not use maximum contraction
      • Amputees could imagine moving to a certain angle
    • When collecting EMG signals, gravity will affect the amount of force needed, so we should have someone place their hand perpendicular to the table to eliminate gravity
  • Servo to prosthetic
    • Don’t operate in exactly the same way
    • We want to use servo as a proof of concept
      • Can demonstrate motion
    • The PID would work well for the hand, but not as well for the servo
      • Couldn’t maintain angle with contraction using PID like we could in the hand
      • Servo works based on mapping to position instead of motion
      • We will still code the PID, just comment it out when using the servo
      • The only part missing would be the actual connection to the prosthetic hand
      • We were thinking of making a MATLAB simulation to show how it would work when translated to the arm
      • Could make a second software package that uses velocity control to control servo so we can demonstrate the change in controller function
  • Ottobock arm
    • Don’t sent to Ottobock, just send back to Case after design day