A Versatile and Safe Mobility Assistant * Kim, Min-Jung 2001/6/12 Special Topics in Robotics Design and Control of Devices for Human-Movement Assistance Article review * 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 –Automatic turning is needed

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