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Navigational assistance for disabled wheelchair users

Student thesis: Doctoral Thesis

Previous low cost systems of navigational assistance for disabled wheelchair users have provided little more than simple obstacle and collision avoidance, or follow a pre-defined fixed route defined by a white line or a buried wire.
Other research has used complex high cost multi-sensor mode systems closely
resembling industrial, military or space exploration applications. These systems used natural features or artificial beacons to produce accurate maps of the operating environments. The progress of the vehicle is monitored and corrected using multisensor techniques such as vision cameras, odometry and triangulation from beacons located in the environment. Such systems have required modification of the operating environment and have resulted in a fully autonomous vehicle providing little or no overall control by the user. Whilst proving the technical feasibilty their cost and complexity has not resulted in practical and affordable solutions for the
wheelchair user.
The purpose of the present study was to bridge the gap between these two previous areas of research and to provide navigational assistance at an affordable cost. Low cost ultrasonic sensors enabled a wheelchair to operate in an unknown (i. e. previously unmapped) environment whilst leaving the user in overall control.
Hardware modifications to a commercial powered wheelchair enabled data from
ultrasonic arrays and the user's joystick to be interrogated and mixed by a computer to provide appropriate signals for the wheelchair drive motors.
A simulation program was created to interpret the sensor signals that would be
generated from the various conditions likely to be encountered by a wheelchair and to develop the various control strategies. The simulation was able to differentiate between the various environmental conditions and select the appropriate action using the newly created control algorithms.
The sensor data interpretation modules together with the control algorithms, from the simulation, were incorporated into a practical system for controlling the wheelchair. In tests data from the sensors was used to detect and evaluate localised changes in the environment and used to determine appropriate signals for the drive wheel motors.
In the tests it was found that the wheelchair controller and the geometry of the
wheelchair resulted in a degradation of the expected wheelchair response. This was overcome in two ways: firstly by modifying the control algorithm and secondly by changing the wheelchair geometry.
Original languageEnglish
Awarding Institution
Supervisors/Advisors
Award date1999

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