With the ultrasonic sensors, we do recognize obstacles without touch. If an unforeseen object shows up one of two things happen:

• Due to the ultrasonic sensors we are convinced that indeed there is an obstacle we have to circumvent. In this case, we won’t touch the obstacle.
• In most cases, the ultrasonic sensors are aware of a possible obstacle but we have to verify it. In this case, the S170 Navi slows down and touches the obstacles lightly.

This strategy is particularly important because we rarely have people around but usually have to deal with difficult environments like table legs, cables and the like.