The Moving Finger – Assistive Technologies for Differently abled

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Mahanth G N, Sachin B C, Shankar Kumar J and Vinay S N of Channabasaveshwara Institute of Technology, Karnataka, worked with Prof. Vijay P Sompur on a project related to design of prosthetic finger replacements using surface EMG signal acquisition.

“The inspiration was a personal life experience,” says Shankar. “One of our schoolmates was physically challenged, and we wanted to help people like him. Several people lose their fingers in accidents or other reasons. The basic idea in our project is to acquire surface EMG signals and use them to provide the functionality of human fingers.”

“EMG is an acronym for Electro Myogram, which is a measure of the electrical activity of the muscles,” explains Mahanth. “It is a signal generated by the brain to command a human locomotory organ such as a finger. If the finger has been severed, the surface EMG signals can still be acquired and a prosthetic finger can be made to move in response to the signal.”

“We used an extensive signal acquisition circuit based on TI’s analog components,” says Sachin. “The surface EMG signals are picked up by Ag/AgCl electrodes. The instrumentation amplifier INA114AP is used to amplify the difference signal between two EMG signals from two points. The output of the amplifier is averaged using a precision fullwave rectifier based on TL082CP. The output of the rectifier is smoothened out using the integrator based on TL082CP. The output of the integrator is amplified using another TL082CP operational amplifier to get an analog signal of sufficient strength.”

“We used the MSP430G2253 MCU from Texas Instruments to process the EMG signal. The built-in 10-bit ADC of the MCU converts the analog signal to a digital value. This value is compared to a nominal value that corresponds to the sedentary state of a finger muscle. If a difference is perceived, it is assumed that the user wishes to move the finger and a Tunigy nanoservo is activated to move the prosthetic finger.”

“We were able to demonstrate the concept successfully, although there is room for further improvement,” says Shankar. “We used Energia software on the MSP430 launchpad and this resulted in a low-cost implementation.”

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