This document discusses the use of electromyography (EMG) signals to control a bionic arm. EMG signals are generated by muscle contractions and detected by surface electrodes on the skin. These signals are filtered and amplified before being fed into a microprocessor programmed to control motors in the artificial arm. When the user contracts their muscles, the EMG signals are processed to trigger corresponding movements in the bionic limb. Key steps include EMG signal generation and processing, as well as addressing challenges like weak signal acquisition and filter design.

1. Bionic Arm Using
EMG Processing
By Pronay Sarkar
Biomedical Engineering
Netaji Subhash Engineering College

2. Introduction
Bionic arm or bioelectronic arm is a robotic arm which is
controlled by the action of muscle stimulation. It is basically
the combined application of electronics, mechanics and
biomedical engineering. The EMG signal generated due to the
contraction and relaxation of the muscles are guided properly
so that the artificial arm can also move accordingly. The main
procedure is to process the EMG signal. The remaining work is
done by feeding the analog EMG signal to a microprocessor
which is accordingly programmed to rotate the motors. Bionics
(also known as bionical creativity engineering) is the
application of biological methods and systems found in nature
to the study and design of engineering systems and modern
technology.

3. EMG generation
Electromyography is the process of recording the total electrical
activity of the motor nerve and muscle innervated by it on cathode ray
oscilloscope or simply the study of the action potential(AP) in human
skeletal muscle. The machine that records the electrical activity is
called electromyograph and the record is known as
electromyogram(EMG). When the motor nerve is stimulated, not only
the nerve develops the AP,but also muscle fibres develop AP. The
resulting electrical activity may be considerable and in the resultant
complex the individual APs are buried.

4. Steps in contraction
1. Discharge of motor neuron
2. Release of acetylcholine at motor end plate
3. Binding of acetylcholine to nicotine acetylcholine receptors
4. Increased Na+ and K+ conductance in end-plate membrane
5. Generation of end-plate potential
6. Generation of action potential in muscle fibres
7. Inward spread of depolarization along T tubules
8. Release of Ca2+ from terminal cisterns of sarcoplasmic reticulum (L tubules)
and diffusion to thick and thin filaments
9. Binding of Ca2+ to troponin C, uncovering myosin binding sites on actins
Formation of cross linkage between actins and myosin and sliding of thin on
thick filaments, producing shortening.
Steps in relaxation
1. Ca2+ pumped back into sarcoplasmic reticulum
2. Release of Ca2+ from troponin

5. EMG Processing

6. EMG filter
The EMG filter so used is a band pass filter which is capable of
passing signals ranging between 5Hz and 450 Hz. A band pass filter is
designed by connecting a high pass filter of low cut off frequency in
series with a low pass filter with a high cut off frequency. A R-C
coupled filter can be used to do the job. The cut off frequency of the
high pass filter should be 5Hz and the cut off frequency of the low
pass filter should be 450Hz.
High pass filter Low pass filter

7. Electrodes
The electrode used in EMG processing is surface electrodes which
is made up of silver chloride or stainless steel. Three electrodes
are placed side by side one of which is reference electrode. the
other one is for positive and the other negative. A gel type
adhesive is used which has two function. One is to keep the
electrodes attached to the skin. The other function is to provide a
low resistive path which helps the electrodes acquire the EMG
signals very easily. The input impedance of the system is very
high so. The reason is that it helps the signal to amplify very
easily. Needle type electrodes are also used for EMG acquisition.
But needle type electrodes are very costly and cannot be used so
easily in this type of experiment.

8. INA 106
The INA 106 is a monolithic Gain=10
differential amplifier consisting of a
precision op-amp and on-chip metal film
resistor. The resistors are laser trimmed
for accurate gain and high common mode
rejection. Excellent TCR tracking of the
resistors maintains gain accuracy and
common mode rejection aver temperature.
The differential amplifier is the foundation
of many commonly used circuits. The INA
106 provides this precision circuit function
without using an expensive resistor
network. The INA 106 is available in 8 pin
plastic DIP and SO-8 surface mount
packages.

10. Atmega-8

13. Problems faced
The main problem faced during doing this experiment would be the
processing of EMG signal. The signal is very weak and hence maximum
distortions occur. The input impedance of the circuit should be
properly balanced so that the signal can easily amplified. Another big
problem is the design of the EMG filter. It is also a tiresome job. The
exact value of the resistance and capacitance should be figured out to
get the exact EMG signal.
Another problem which could be faced would be the function of the
microcontroller. An frequency to voltage converter has to be used
which would convert the EMG frequency into voltage which would be
faced as input to the microcontroller. Any kind of distortion in the
process would lead to malfunctioning of the microprocessor hence,
the prosthetic arm.

14. Conclusion
The bionic arm can have many application. The prosthetic limbs can
use this technique for natural movements of the limbs. The bionic arm
increases the strength of a normal arm by almost 100. The precision of
holding any object increases a lot. If the arm is properly designed then
any microscopic thing can also be gripped which is impossible by
humans. This technique can be used in robotic surgery where the
doctor controls a robot from far distance to operate a patient by using
joystick. If the doctor can control the robot by his will which s
accordingly converted into his EMG signal them it would be beneficial
to him. Though the thought is under process but if properly worked
then this dream can come true soon. The advancement of science
helps us to get things which once was unimaginable. Maybe someday
this kind of arms would be actually in the market which will reduce
human load.