L08. Myoelectric Control of Upper Extremity Prostheses Flashcards
What are the 2 standard options for upper extremity amputees?
Body-powered and electrically-powered
Where is an EMG typically me measured
Skin surface or intramuscularly
What does 1-muscle-1-function mean
Agonist/antagonist muscles used to control opposing functions
What do electrodes do?
Amplify the difference between contacts and attenuate signals common to contacts
The better the _____, the better the electrode
Common Mode Rejection Ratio
How does electrode position impact the EMG signal?
The signal is sensitive to the position of the electrode. The closer and more central the electrode is, the stronger the signal
What is the sampling rate for a surface EMG?
1 kHz
What is the sampling rate for intramuscular EMG?
2-3 kHz
What frequency should the bandpass filter be set to? Notch filter?
Bandpass: [0 500Hz]
Notch Filter: 60Hz
What is the purpose of a low pass filter circuit
Smoothing and obtaining signal envelope
What is the lockout method for 2-site EMG Control?
First EMG signal to cross threshold gets and maintains control until it drops below threshold
What is the “Most On” method for 2-site EMG Control?
Largest EMG signal gets and maintains control
What is the pattern recognition method for 2-site EMG Control?
A specific sequence/pattern of EMG signals performs a function
What is the switch control method for 2-site EMG Control?
- Only controls one function at a time
- Contract both muscles to switch between desired function
Where are EMG’s placed for an above elbow myoelectric prosthesis
Biceps and triceps
- Biceps flex elbow and close hand
- Triceps extend elbow and open hand
For myoelectric control, what is the maximum number of threshold levels for one EMG signal?
3-5
What is pulse width modulation?
Used to control the speed of hand open/close. Motor speed is proportional to duty cycle
What is a limitation of a lot of myoelectric prosthesis?
They rely on intact musculature
What is targeted muscle reinnervation?
The idea that the patient attempting to move a missing limb segment causes parts of newly innervated muscle to contract
- some sensation can be restored
