An Integral System for Assisted Mobility

1. An Integral System for Assisted Mobility Manuel Mazo & the Research group of the SIAMO Project Yuchi Ming, IC LAB

2. Contents • Overview. • System Architecture • HMI(Human-Machine Interface). • Environment Perception. • Navigation and Control. • Summary

3. Overview • The SIAMO(Spanish acronym for Integral System for Assisted Mobility) project began at the end of 1996. • Motivation: Design autonomous wheelchairs as an assistance device for the disabled or the elderly. • Goal: Safety, Comfort and Modularity.

4. System Architecture

7. Human-Machine Interface • Breath expulsion • Head Movements. • Electro-oculography(EOG). • User-dependent voice recognition. • Joystick. • Display & voice synthesizer.

8. Guidance by Breath Expulsion • A differential air-flow sensor with a linear output is used, so it is possible to detect both strength and direction of breathing. • With an “easy-to use” breath code it is possible to obtain the references of linear and angular velocities and to stop the chair in case of trouble. • This driving aid allows commanding the chair in broad corridors and halls as well as crossing through doors of 1.5m wide without any other assistance or sensory system.

9. Guidance Head Movements.

10. Guidance by Electro-Oculography • This method allows one to generate simple coder for controlling the wheelchair using eye placement. • Several biopotential skin electrodes are placed on the user’s face to detect eye movement.

11. Guidance by Voice Commands • Instead of a computer, a commercial isolated word recognition chip has been used. • A set of nine voice commands are developed. Each command has an associated driving function: Stop, Forward, Back, Left, Right, Plus, Minus, Password and Track. • “Plus” and “Minus” means increase or decrease the speed. • “Password” allows switch between the voice control and normal conversation. • “Track” allows switch between voice control and Autonomous control.

12. Environment Perception • Ultrasonic sensors. • Infrared sensors. • Active laser sensors. • Passive vision system based on artificial landmarks.

13. Ultrasonic Sensors.

14. Infrared Sensors • The role of the infrared sensors is to detect floor unevenness. • The sensor makes distance reading up to a point marked on the floor 2m in front of the wheelchair

15. Active Laser Sensors • This sensor module obtains 3-D positions of obstacles. • A laser emitter projects a plane-form bean over the scene. From the image captured by the CCD camera, the points belonging to that bean are segmented. • Expensive.

16. Passive Vision System • The landmarks are simple A4 paper sheet with a black-white pattern printed on them. • Positioning is performed by measuring the landmark distortion in the captured image. • Landmarks must be located at heights over 1.5m(height of the camera, and each entrance door must be signaled with one landmark right over it.

17. Navigation and Control • Automatic Navigation strategy is incorporated in the wheelchair so that the user only need to indicate the destination point. • Automatic Navigation need a full mapping of of the environment.

18. One contactless node, equipped with a wireless drive, can be placed on the main doors and loaded with a full description of room identification, landmark location, and routing inside the building. • The wheelchair need not to store all the maps.

19. Summary The system has the characteristic of being modular, which allows it to be easily adapted to each user’s specific requirements, depending on the type and degree of disability.