It is normal for the robot to touch objects. When it recognizes an obstacle, its three ultrasound sensors on the front bumper/fender cause it to slow down, so that the bumper can gently push against the obstacle. The robot then uses this contact to work out how to move around the obstacle. For this to work, the obstacle has to be heavy enough for the sensor behind the bumper to be activated. Generally speaking, you should remove light objects from the floor in order to ensure thorough cleaning.
My robot touches objects on the floor, such as shoes, and sometimes pushes them away.
