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A Navigation System for Increasing the Autonomy
and the Security of Powered Wheelchairs
S. Fioretti, T. Leo, and S.Longhi
yhseo, AIMM lab
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.
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
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
Navigation System
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
Navigation System (Cont’d)
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
User Interface
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
Operation Details andExperimental Result
• Obstacle Avoidance
– using algorithm based on the
fuzzy rules
– dead-lock
situation have to be solved by the user
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