GuideCane Robotics-Based Obstacle-Avoidance System for the Blind and Visually Impaired Presented by Priya GS

Contents Mobile Robotics Technologies Guidecane – Introduction How Guidecane works? GuideCane – In Detail Recap

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 Useful for visually impaired people “Bioengineering for the people with disabilities” GuideCane is a computerized travelling aid uses obstacle avoi dance technologies.

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 r ight 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

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 How Guide Cane Works?

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  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 Solution for downward and upward steps

GuideCane – Functional Description  How upward steps are detected? 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 Handle

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

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

MCIB executes the following critical tasks  Firing the sonar’s at specific times  Generating the pulse width modulation signals for the servo  Decoding the encoder data 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

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 MC68HC11

GuideCane – Electronic Hardware Connection Diagram of MC68HC11

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 They use mobile-robotics based obstacle avoidance technologies  To determine a safe path for travel and  To guide the user along that path GuideCane is fundamentally different from the existing Electronic Travel Aids, that, at best, only inform the user about the existence and location of obstacles but do not guide the user around them

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