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