Smart Walker Detects Obstacles
From: Electronic Design - August 20, 2001 - page 38
By; Lisa Eccles

A research team at the University of Virginia's Medical Automation Research
Center in Charlottesville has developed a prototype "smart" walker. This
mobility aid should improve the quality of life and lengthen the duration of
independent living among the world's elderly. 

The intelligent walker improves safety through features such as obstacle
avoidance and drop-off detection. This lets users navigate traditionally
difficult situations, such as tight spaces and doorways. It also reduces the
risk of catching a wheel on an object. And, the smart walker helps users
follow a specific route through an environment. 

This prototype is considered a passive robot. Since it can only control the
orientation of its front wheel and cannot move forward on its own, it
requires a human to move it. Its control system is an intelligent agent that
provides support and navigation assistance. This agent studies the movement
of the walker frame and the sensor systems to derive a model of the user. It
then attempts to decipher where the user may be going. 

When the control agent is actively helping the user steer, the control system
and the user input control signals to the walker frame. The researchers say
that each agent learns about the other by observing the walker's resulting
motion. The agent's ability to implicitly formulate the user's goals allows
the user to employ this device in a seamless manner. When the desires of the
user and the agent differ, the user's actions take priority. 

However, the walker control agent assumes complete control when a collision
or drop-off is imminent and the brakes must be applied. The researchers say
the walker can assume a more or less active role in guiding its user
depending upon the user's abilities at any given time. The ability to alter
this degree of autonomy is an ongoing area of research. 

The prototype walker is based on a conventional three-wheeled frame from
InvaCare Corp. of Elyria, Ohio. This frame has been augmented with sensors
and actuators to control the front wheel and the brakes.  Mounted on the
front of the walker, a laser scanner provides a depth map for a 180 degree
field of view in front of the walker. IR sensors are being installed to
monitor for collisions with the back wheels. Encoders have been mounted on
all three wheels.  These devices let the smart walker determine the path
taken by the user as well as the likely direction the user will take next. 

The drive system is a belt-driven stepper motor system capable of turning the
front wheel to a given heading. Since the drive system can only control the
front wheel's orientation, the user must provide the motive force. Currently,
the prototype features hand brakes. A motorized brake system has been
designed to activate the existing brakes on the rear wheels. Thus, the walker
can be stopped conventionally by the user or halted by the control system in
the event of a dangerous situation. 

The prototype also is being outfitted with handle sensors to detect the force
planes on each handle. These sensors provide both an indication of the
movement taken by the user and detection of the user's desire prior to the
movement of the walker. 

For more information, point your browser to 
http://marc.med.virginia.edu/projectreport.asp?id=6

Photo caption: Based on a conventional three-wheeled frame, the prototype
walker has been augmented with sensors and actuators to control the front
wheel and the brakes. Pictured are walker team members (left to right) Steve
Kell, Jim Gunderson, Mike Cvetanovich, Glenn Wasson, and James Wang. 

