ELECTROOCULOGRAPHIC GUIDANCE OF A WHEEL CHAIR USING EYE MOVEMENT CODIF

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ELECTROOCULOGRAPHIC GUIDANCE OF A WHEELCHAIR USING EYE MOVEMENTS CODIFICATION :

ELECTROOCULOGRAPHIC GUIDANCE OF A WHEELCHAIR USING EYE MOVEMENTS CODIFICATION CH.SUBODH IVB.TECH ECE K.L.S.RAMI REDDY IVB.TECH ECE

INTRODUCTION:

INTRODUCTION An eye controlled based on electrooculography is designed to develop a system for assisted mobility. Assistive robotics can improve the Quality of life for disable people. Now a days , there are many help systems to control and guide autonomous mobile robots. The system consists of a standard electric wheel chair, an onboard computer, sensors and a graphical user interface. In this new era, we can see video oculography systems (VOG) or infrared oculography (IROG) based on detecting the eye position using a Camera. Our goal is the development of a robotic wheel chair system based on electrooculography

ELECTROOCULOGRAPHIC POTENTIAL(EOG) :

ELECTROOCULOGRAPHIC POTENTIAL(EOG) EOG presents a good face access, good accuracy and resolution , great range of eye displacements , works in real time and is cheap . Our discrete electro oculographic control system (DECS) is based on recording the polarization potential or corneal-retinal potential (CRP ). This potential is commonly known as an electro occulogram. The EOG ranges from 0.05 to 3.5 mV in humans and is linearly proportional eye displacement. The human eye is an electrical dipole with a negative pole at the fundus and a positive pole at the cornea .

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The analog signal form the oculographic measurements has been turned in to signal suitable for control purposes. The EOG signal changes approximately 20 micro volts for each degree of eye movement. The EOG signal is a result of a number of factors as eye ball rotations, eye movements, different sources of artifact such as EEG, electrodes placement, head movements etc., To avoid the shifting rest potential(mean value) an AC differential amplifier where a HPF with cut off 0.05Hz and relatively long time constant is used.

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EYE MODEL BASED ON EOG Our aim is to design a system capable of obtaining the gaze direction detecting the eye movements. In view of the physiology of the occulomotor system, the modeling thereof could be tackled from two main view points. a)Anatomical modeling of the gaze fixing system , describing the spatial configuration thereof and the ways the visual information is transmitted and processed. b) Modeling of the eye movements

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The filter block should be a compound for a HPF with a cut off frequency of 0.05Hz that eliminates the continuous component and therefore it’s variability. To eliminate high frequency interferences on the EOG, a LPF with a cut off frequency of 35Hz is used. To enhance the signal and to improve their characteristics an ALE_LMS ( Adaptative Line Method using Less Mean Square) algorithm based on Wiener filter is used.

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OCULAR MOVEMENTS DETECTOR BLOCK This block allows to separate saccadic and smooth eye movements using the EOG derivative When a smooth movement takes place, a speed control is used, this is, the speed, duration and direction of the movements is calculated, this is the way to calculate the displacement angle corresponding to the smooth movement. The final position (angle) is calculated as the sum of the saccadic and smooth movements.

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CONTROLLING OF THE WHEEL CHAIR The EOG signal is recorded using Ag- AgCl electrodes by means of an acquisition system are sent to an onboard PC in which they are processed to calculate the gaze direction. Then, in accordance with the guidance control strategy and the ocular movement detected , the corresponding control command is activated.

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This generates the linear and angular speed, which are sent to the low level control of the wheel chair. Visual feedback system is found which is very much useful for the user. The mechanical structure of the Wheel chair consists of a platform on two motor wheels and two idle wheels. The motor wheels, with a radius Rd = 16 cm and separated by a distance D = 54 cm,

LOW LEVEL CONTROL :

LOW LEVEL CONTROL The communication between the PC and the motor drivers of the right and left wheels is carried out by means of a PCLTA through a DDE connection. The low level control of the electronic system for controlling the DC traction motor is implemented with a PID(programmed into Neuron Chip)and its mission is to ensure that the linear speed of the right and left-hand wheels is approximately that indicated on the electronic control cards.

User interface:

User interface The guidance based on eye movements codification has different options, such as continuous guidance and on-off activation commands. The ON-OFF activation consists of detecting some ocular action and execute a guidance command associated.

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For this, we have implemented the following movement commands UP: Linear speed increase (V++) DOWN: Linear speed decrease (V–) RIGHT: Angular speed increase (Ω++) LEFT: Angular speed decrease (Ω--) This control allows to reduce the linear speed if the angular one is big and closed curved trajectories is not allowed that can be dangerous for the user. Besides, it exists alarm and stop commands for dangerous situations that permits stop (Rep) and switch off (Off) the system. The linear and angular speed selected by user are converted to linear speed of the right and left-hand wheels (wr,wl) in accordance with equation.

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STATE MACHINE DIAGRAM

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CONCLUSIONS This research project is aimed towards developing a usable, low-cost assistive robotic wheel chair system for disabled people. In this work, we present a system that can be used as a means of Control allowing the handicapped, especially those with only eye-motor coordination, to live more independent lives.

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REFERENCES [ [Akay, 94] M. Akay. “Biomedical Signal Processing”. Ed: Academic Press. 1994. Lahoud and Dixon Cleveland. "The Eye gaze Eye tracking System". LC Technologies, Inc. 4 th Annual IEEE Dual-Use Technologies and Applications Conference.

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THANK YOU VERY MUCH ANY QUERIES PLEASE!!!!!!

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