A Navigation System for Increasing the Autonomy and the Security of Powered Wheelchairs

1. A Navigation System for Increasing the Autonomy and the Security of Powered Wheelchairs S. Fioretti, T. Leo, and S.Longhi yhseo, AIMM lab

2. Introduction • Research Activities related to smart powered wheelchairs • VAHM project ,NavChair, The Hephaestus smart wheelchair, etc … • Design of a proper navigation system and its integration with a commercial powered wheelchair, equipped with a user interface and sensor devices • The navigation system with a set of functions to increase the autonomy and the security if persons with motor disabilities with Sonar sensors • Two levels of autonomy are implemented giving the users different degrees of control • The integration approach to the design mainly relies on the adoption of multi-modal computer integration based on M3S protocol.

3. Design Criteria for The Navigation System of A Powered Wheelchair • Considerations for the design of the powered wheelchair navigation system (based on user’s need by interviewing people with different disabilities) • Different Psychological Attitudes • Role of Information • Acceptance of Informatic Tools • System Cost • System Dimensions • System Friendliness • Physical Appearance • Extroverted Tasks • Level of Autonomy • Design Criteria • Usability, acceptability, efficiency, security and costs

4. Navigation System • Architecture • Navigation sensors : dead-reckoning and external/environmental sensors • Sonar Map of the Environment • Sensors are positions and oriented in a manner to reduce of crosstalk and to detect obstacles along the direction of movement • Improvement of Reliability and accuracy of sonar measures • data fusion in a probabilistic local map of the environment • fuzzy logic and evidence method

5. Navigation System

6. Navigation System (Cont’d) • The Autonomy Levels of the Navigation Module • First Level : a simple filtering of the user’s commands • Stop + Wait action or Stop + Invocation of User Help action • Second Level : some local corrections on the user’s commands by a simple obstacle avoidance algorithm • user can’t control but can activate the Stop action

7. Navigation System (Cont’d)

8. User Interface • The use of M3S protocol • to interface the user control devices with navigation system • reduce costs, rapid prototyping and easy to change or add • Interface based on a button and video display • video display : input action, system status, and output message areas

9. User Interface

10. Operation Details andExperimental Result • The implementation of navigation system • PC 486DX2 with PC-104 bus • PC manages the sonar and the encoder reading and connection with M3S bus to user interface

11. Operation Details andExperimental Result

12. Obstacle Avoidance • using algorithm based on the fuzzy rules • dead-lock situation have to be solved by the user

16. Conclusion • Shows the proper design of a navigation system which increase the autonomy and the security of commercial powered wheelchairs • The development of navigation module and its integration on a commercial powered wheelchair • Different level of autonomy for the navigation module have been developed and tested • A user interface with M3S interface which is simple both in commands requested and in information to the user