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Bionic Arm Using EMG Processing
- 1. Bionic Arm Using EMGProcessing By Pronay Sarkar Biomedical Engineering Netaji Subhash Engineering College
- 2. Introduction Bionic arm orbioelectronic 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 isthe 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
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- 6. EMG filter The EMGfilter 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 usedin 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 INA106 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.
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- 13. Problems faced The mainproblem 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 armcan 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.