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Safety in robotics: the Bremen Autonomous Wheelchair

Describes the development of a safety layer for an electrically driven wheelchair that is equipped with a ring of ultrasonic sensors. Designing this safety layer, which consists of software modules as well as hardware components, involved formal methods. An important outcome of the presented formal approach is a detailed set of hypotheses that specify the requirements the environment has to satisfy in order to allow the robot to behave as intended. The safety layer builds an abstraction of the real wheelchair which ensures that collisions are avoided, and guarantees that communication between software modules in a multi-PC environment takes place in real-time. As a first application on top of the safety layer, a driving wizard has been implemented. Its task is to adapt the wheelchair's speed depending on the situation of obstacles in the surrounding of the vehicle. The driver has no longer to bother with the question whether the planned trajectory will lead to a collision or not.