BREAKING THE ACCESSIBILITY BARRIER: DEVELOPMENT OF SPECIAL COMPUTER ACCESS

MECHANISMS FOR THE NEURO-MOTOR DISABLED IN

INDIA

Presented By

Animesh Mukherjee

IIT Kharagpur

A BRIEF INTRODUCTION

• In India, about 22 million people suffer from various kinds of disabilities.

• A large segment of the above population suffer from neuro-motor disorders.

These disorders are caused by,

• Faulty development of motor areas in the brain, or,

• Damage of these motor areas.

THE AFFECTED MOTOR AREAS OF THE BRAIN

The posterior (back) of the frontal lobe consists of the premotor and motor areas. Nerve cells that produce movement are located in the motor areas. The premotor areas serve to modify movements.

CONSEQUENCES

• Severe difficulty with fine motor tasks (like writing, stitching, using computer peripherals, and various other such tasks.)

• Severe difficulty with any kind of communication.

AAC TECHNIQUES

• This population depends on various AAC techniques for their communication needs.

• These techniques may be based

- On non-electronic communication boards

Or,

- On Computers

PROBLEMS WITH COMPUTER BASED AAC TECHNIQUES

• Any computer based AAC system needs to be equipped with special mechanisms in order to make them accessible by this group of users.

• This is since they lack the fine motor control required to operate the peripherals like mouse, keyboard etc.

PROBLEMS WITH COMPUTER BASED AAC

TECHNIQUES(CONTD …)

• Access mechanisms commercially

available are too costly for an average

Indian user.

• Usually such systems come in special

packages, the cost of which ranges

from $600 to $6000

OUR ENDEAVOR

• In response to this need we have tried to develop some AAC systems which are completely indigenous and available at an affordable price.

• In our paper we have mainly tried to discuss some of the access mechanisms tuned to these systems which are specifically meant for serving the purpose of the cerebral palsy (CP) affected users.

COMPONENTS OF THE ACCESS MECHANISM

• Software Component

- deals with making AAC systemaccessible to the user withspecial access devices

• Hardware Component

- deals with the development of special hardware devices suitable for these users.

THE SCANNING MECHANISMS

• Scanning refers to periodic focusing and defocusing of elements on a computer screen.

• The method of scanning can be broadly classified into two categories, namely:

- Co-ordinate Scanning, and,

- Matrix Scanning

CO-ORDINATE SCANNING

• Computer screen is thought of as a two-dimensional co-ordinate system.

• Each element is treated as a point.

• To get to specific point one or both the axes of the co-ordinate is made to sweep over the entire screen area.

• This movement can be either rotational or translational.

POLAR SCHEME OF COORDINATE SCAN

Direction of rotation of the axes

Direction of movement of the mouse pointer

CARTESIAN SCHEME OF COORDINATE SCAN

Direction of movement of the mouse pointer

Direction of movement of the x-coordinate selector

MATRIX SCANNING

• The computer screen is thought of as a matrix.

• Screen elements correspond to the individual cells of this matrix.

• More suitable for applications with a known set regions that need to be frequently activated.

VARIANTS OF MATRIX SCAN

• Three dimensional matrix scanning (block, row and cell levels).

• Two dimensional matrix scanning (row and cell levels).

• One dimensional matrix scanning (cell level).

MATRIX SCAN ILLUSTRATED

Row Level Scan

Cell LevelScan

Block Level Scan

STRATEGY FOR PLACEMENT OF ELEMENTS ON THE CELLS

OF THE MATRIX

A B C

D E F

G H I

0 1 2

3

432

1 2

HARDWARE DEVICES

• Once an element of interest is reached by any of the scanning mechanisms the task left is to physically select that element.

• Special hardware devices called access switches are used for this purpose.

• Among such switches we have developed

- Press switches

- Touch Switches

PRESS SWITCH

• With press switches, the modes of operation supported are,

- Single switch mode, - Two switch mode,

- Five switch mode.

TOUCH SWITCH

• The modes of operation supported are,

- Single switch mode,

- Two switch mode.

AN EXAMPLE AAC SYSTEM- THE VIRTUAL BENGALI KEYBOARSD

Coordinate Scan

MatrixScan