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Human-machine interface (HMI) enabled by epidermal electronics system (EES). ECE445 Senior Project Team #37: Woosik Lee, Ohjin Kwon, Nithin Reddy. Introduction. The micro/nanotechnology development has access to many types of motion sensors
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Human-machine interface (HMI) enabled by epidermal electronics system (EES) ECE445 Senior Project Team #37: Woosik Lee, Ohjin Kwon, Nithin Reddy
Introduction • The micro/nanotechnology development has access to many types of motion sensors • Human motions can be directly translated into the controlling system by directly mounting the electronic system onto skin epidermis
Features • EES that has the matching mechanics to the skin epidermis • Portable Signal Conditioning Unit • Easy programmable microcontroller
EES Electrodes Integrating Conventional to EES electrodes
Fractal Design • Def.: self-similar and recursive structure in naturethat can fill space with increasing iteration • To provide design criteria for stretchable, biomedical devices
Micro Fabrication Spincoated PR ③ ① ② Evaporated Au Spincoated PI PI PI PI PI PI PI PI Au PDMS PDMS PDMS PDMS PDMS PDMS PDMS PDMS PDMS Si Wafer Si Wafer Si Wafer Si Wafer Si Wafer Si Wafer Si Wafer Si Wafer Si Wafer Encapsulated PI Developed PR ④ Etched Au ⑤ ⑥ Au Spincoated PR Developed PR ⑦ ⑨ ⑧ Etched PI
Transferring • Pick up EES electrodes by water soluble tape • Laminate on thin ecoflex (silicon) as a substrate • ACF cable connection • Solder wires on PCB board that connects EES electrodes with amplifier REC GND REF
Verification • Measurement result 1 : Thickness less than 2µm • Thickness dependency of conformal contact on skin • Use electron beam (e-beam) evaporator and choose the right rpm & time of spinner.
Verification • Measurement result 2 : Noise to ratio • Range within -1mV to +1mV
Verification • Measurement result 3 : Detecting EMG • Bending fist makes enough EMG signal Stable Bending
Verification • Measurement result 4 : Spatial Actions • Four spatial actions can be classified as distinct motions using two EES electrodes on each forearm.
Verification • Measurement result 5 : Stretchability • Observe plasticity point about 20% of stretching by using stretcher and lock-in amplifier.
Signal Conditioning Unit • Receive the signal from E.E.S. • Detect signal & Amplify gain 10000. • Filter 10Hz ~ 500Hz (E.M.G. cut off frequency) • Filter noises
Instrumentation Amplifier • Type of amplifier that eliminates the need for input impedance matching • Increase the gain, 10000.
620 Instrumentation Amplifier • Instrumentation amplifier • Outfitted with input buffer • Main amplifier • Low power, Suitable, High open-loop gain • REF - Virtual short voltage - From 741 op amp - G = V0/(Vpin1-Vpin8)
741 Operational Amplifier • Consists of differential input, single-ended high gain stage, output buffer, one capacitor. • 741 op amp + Capacitor + Register → Low Pass Filter 1. Filtering signal from 620 amp 2. Voltage cancel (signal go into REF of 620 amp)
(Negative) Feedback • Reduce the effect of noise • Desensitize the gain • Increase filtering coefficient with extra poles • Control terminal impedances • Reduce non-linear distortion • Bandwidth extension
Band-pass Filter • Filtering ↓10 Hz & ↑500 Hz • 4th order LPF & 1st order HPF
Low-pass Filter • Attenuating above 500 Hz signal • 4th order low-pass filter
High-pass Filter • Attenuating below 10 Hz signal
Verification • PSPICE program • Low-pass filter, cut off frequency = 500Hz
Verification • PSPICE program • High-pass filter, cut off frequency = 10Hz
Power Supply • Signal Conditioning Unit • Each chip ≥4.8v • Two 5 volt batteries • Supplies to +Vs and –Vs • Microcontroller • 5v
Microcontroller • Arduino Uno was used. • Consists of a 10 bit Analog to Digital Convertor. • Analyze & Convert the signal from S.C.U. • Atmega16U2programmed as a USB-to-serial converter. • Derives power from USB. • Easily Programmable.
Microcontroller Implementation • Input is received from the S.C.U. • Reads the input signal and determines the amount of voltage generated by muscle of the user. • Transfers data to computer through USB . • Displays direction that user intends to move robot using visualization software.
Software • Arduino Software Input from the S.C.U is received on the input pin A0 and sends out voltage through COM port(USB) to computer • Processing Software The computer receives the signal from the Arduino through the USB and displays the signal on a threshold graph and prints out direction that user moves muscle.
Arduino Software • Takes in Input from the S.C.U from pin A0. • Reads the analog input . • Displays the signal on the serial monitor . • Transfers the data through COM 5 to the computer.
Processing Software • Displays received input signal on a threshold graph. • Bar on graph shifts as muscle is flexed by the user. • Program displays the action of the user based on the how far the bar moves on the graph.
Microcontroller Testing • Tested using a conventional potentiometer. • Potentiometer connected to the input pin A0. • Ran the Processing and Arduino software with this input. • Observed the graph and checked if the bar moves as we turn the knob of the potentiometer. • Observe if the program prints out a direction if the bar is within the respective ranges.
Demonstration • PCB board was burned • Reason • Was not connected with GROUND • Solution • Used conventional amplifier instead • Disadvantage • Already set up for PCB board
Challenges • Delay on manufacturing PCB board • A low yield producing EES electrodes • High noise level of EES electrodes depending on device quality
Future Work • Prepare two sets of SCU component for each arm • Develop EES RF antenna that sends EMG signal wirelessly to SCU • Small size packaging of SCU and microcontroller • Develop program that connects microcontroller and controllable machine on computer
Credits Thanks to • Professor Scott Carney • Mrs. Lydia Majure • Mr. Jamie Norton • Dr. Hong and Dr. Jeong from Rogers Research Group • Laboratory for Optical Physic and Engineering (LOPE)