Transcript A Versatile and Safe Mobility Assistant*

Special Topics in Robotics
Design and Control of Devices for Human-Movement Assistance
A Versatile and Safe
Mobility Assistant*
Article review
Kim, Min-Jung
2001/6/12
*A.
Lankenau and T. Rofer, IEEE Robotics & Automation Magazine, March, 2001, pp. 29~37
Bremen Autonomous
Wheelchair project
• Covers mainly
– Spatial cognition
– Safe system
– Mobility assistant for the
handicapped
• Implements
– Obstacle avoidance + Driving
and routing assistant in a
shared-control system
Principle idea
• A shared-control system
– The wheelchair changes the dangerous
target command into a safe one.
Safety Layer (1/4)
• Local Obstacle Map
– A quadratic array of cells,
each of which encodes the
presence of an obstacle at
the corresponding position
in the environment of the
wheelchair
– The wheelchair’s current
rotational deviation to the
map is continuously
updated
Safety Layer (2/4)
• Adaptive Sonar Firing Strategy
– 27 ultrasonic sensors
– Can only fire 2 of its 27 sensors
simultaneously. It involves the risk of
overlooking relevant obstacles.
 Firing strategy is needed
Safety Layer (3/4)
• Adaptive Sonar Firing Strategy
– Determine the firing sequence from
• The wheelchair’s current movement direction,
steering angle, and the data represented in the map
A static firing strategy
The adaptive static firing strategy
Safety Layer (4/4)
• Stopping in time
– The following things must be considered
• The wheelchair’s deceleration and its
reaction time
• The travel distance to the closest obstacle
Elementary skills (1/3)
• Smooth speed control
– Early detection of obstacles can make
the wheelchair decelerate in a smooth
manner
– The user can concentrate on steering
Elementary skills (2/3)
• Obstacle avoidance
– The assistive system
infers the will of the user
whether the user moves
to right or left and
reinforce the trend
Elementary skills (3/3)
• Turning around
– Wheelchair
turning is
difficult because
of the
kinematical
restriction
– It resembles the
problem of
parking a car
The mobility assistant
• The driving assistant
– It combines above three elementary
skills for the users to concentrate on
steering
• The route assistant
– The large scale navigation is done by it
especially for the users who have
amnesia*
*amnesia:
Partial or total loss of memory, usually resulting from shock,
psychological disturbance, brain injury, or illness
Conclusion
• The Bremen Autonomous Wheelchair
is designed for the handicapped in a
shared-control manner
• Implemented safety layer and
elementary skills for the user’s safe
and comfortable navigation