GuideCane-Robotics-Based Obstacle-Avoidance System for the Blind and Visually Impaired

Contents
Mobile Robotics Technologies
Guidecane – Introduction
How Guidecane works?
GuideCane – In Detail
Recap
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Mobile Robotics Technologies for The Visually Impaired
With the development of radar and ultrasonic technology a new series of devices, known as Electronic Travel Aids (ETAs) were developed

ETAs use Obstacle avoidance Systems (OAS)

Obstacle Avoidance System comprises of
A set of ultrasonic or other sensors
Computes algorithm

GuideCane-An Introduction
GuideCane is a computerized travelling aid uses obstacle avoidance technologies.

Useful for visually impaired people

“Bioengineering for the people
with disabilities”
GuideCane
GuideCane was an invention to overcome the drawbacks of NavBelt
It is usually worn by the user like a belt around the waist

GuideCane – System Description

Servomotor
Operates under the control of the built-in computer
Can steer the wheels left and right
Wheels equipped with encoders
Determine their relative position

10 Ultrasonic Sensors
To detect obstacles

Mini joystick located at the handle
To specify a desired direction of motion


GuideCane – Functional Description
Based on the user input and the sensor data from its sensors, the computer decides where to head next

How Guide Cane Works?
Normal Operation

The user pushes the GuideCane forward with the help of the thumb-operated joy-stick

The built-in computer uses the sensor data to instantaneously determine an appropriate direction of travel

GuideCane – Functional Description
When Obstacle is encountered

The object avoidance algorithm prescribes an alternative direction that would clear the obstacle and then resume in the desired direction

Once the wheels begin to steer sideways to avoid the obstacles, the user can feel the resulting horizontal rotation of the cane

The traveller changes his orientation

GuideCane – Functional Description
Solution for downward and upward steps
How downward steps are detected?

When a down step is encountered, the wheels of the Guide Cane drop off the edge until the shock absorbing bottom hits the step

Since the user walks behind the Guide Cane, he has enough time to stop

GuideCane – Functional Description
First step is detected just like an obstacle
The additional sensor (known as the "forward-up" facing sensor) calculates R2
The difference between R2 and R1 is computed
If it meets with the pre programmed criterion of stairs, then the guide cane Identifies it as stairs
If R2 and R1 are almost equal, then the object is treated as a wall

GuideCane – Hardware Implementation
GuideCane is a fully embedded system

The two basic hardware used in
GuideCane are

Mechanical hardware and
Electronic hardware

GuideCane – Mechanical Hardware
The GuideCance consists of 3 modules

Housing
Wheelbase
Handle

GuideCane – Mechanical Hardware

Housing
Made of acrylic
Contains and protects most of the electronic component
Wheelbase
The wheelbase is steered by a servo motor & supports 2 unpowered wheels
Uses ball bearing to support two unpowered wheels

Handle
The handle is the main physical interface between user & the Guide Cane
An aluminium bar with square shape
At the level of the user’s hand, a joystick is fixed to the handle



GuideCane – Electronic Hardware
The main brain of the Guide Cane is an embedded PC/104 computer, equipped with a 486 microprocessor clocked at 33MHz

The PC/104 stack consists of 4 layers

Motherboard
Video Graphics Array (VGA)
125-MB hard disk
Micro Interface Board (MCIB)

GuideCane – Electronic Hardware
The Main interface is connected to PC’s bi-directional parallel port

preprocesses the sensor data
All communications are buffered
The preprocessing and buffering minimize
The computational burden on the PC to control the sensor’s and actuators

The main interface consists mainly of

Three MC68HC11 micro controllers
Two quadrature decoders
A FIFO buffer

GuideCane – Electronic Hardware
MC68HC11 is a 8 bit data, 16 bit address Microcontroller from Motorola

It has
In-built EEPROM
RAM
Digital I/O
Timers
A/D Converter
PWM Generator
Serial Communication Interface

GuideCane – Electronic Hardware
GuideCane– Advantages
Advantages

It allows fast walking, up to 1m/s

It can be used to travel or detect staircases

Easy to handle, and no training is needed

It rolls on wheels that are in contact with the ground, thus position estimation is easy


GuideCane-Disadvantages
Future Enhancements

It cannot detect overhanging objects like tabletops

It can be overcome by including an additional upward looking sonar’s


Recap
GuideCane is a computerized travel aid designed to help visually impaired users to travel along densely and cluttered environments



Bibiliography
Nicholas G.B., Sypros T., “Bio-Engineering For People With Disabilities”, IEEE Journal, Robotics And Automation

I.Ulrich and J.Borenstein, “ VFH: Local Obstacle Avoidance With Look Ahead Verification ”, IEEE Journal, Robotics And Automation

J. .Borenstein and Y.Koren, “The Vector Field – Fast Obstacle- Avoidance For Mobile Robots”, IEEE JOURNAL, IEEE Journal, Robotics And Automation

WWW.Google.Com


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