Electromyography (EMG) signals, collected at the skin surface, have been used for the control of upper limb prosthetic devices since 1948. They provide easy and noninvasive access to physiological processes of muscle contraction. EMG signals are processed to attain parameters that are related to the muscles temporal activities. The attainment of these parameters through time constructs a unique signature for each particular gesture. At present, the process of EMG signals is the most common approach used for the control of active prosthetic hands. The EMG signals are electronically amplified, filtered and digitalized with the use of a PC and appropriate software or embedded into a microcontroller. The use of such an EMG controlled limb can be useful in a number of areas. It could be used for people who have a limited ability of movement and strength in their limbs, to still be able to move around and function in their world as they did before they lost their functionality or strength of their limb. EMG controlled limb can also be very useful when there is a need to handle and manipulate objects that are too dangerous to handle with one's own limbs.
Measuring the EMG signals from muscles.
Electromyography is a technique for detecting and recording electrical signals emanated by muscles when activated.
Surface EMG: -
- Non invasive, simple and inexpensive
- For surface muscles only
- Global pick up (whole muscle)
- Requires adequate skin preparation: removal of dirt, oil, hair etc.
Features of EMG signals
1.Typical amplitude 20-30 mV
2. Frequency 10-500Hz
3.Usable energy is from 10 HZ to 150Hz