Abstract: The present method and system for the automatic orientation and control of a robot in a space or on a surface to be worked by the robot, for example an area to be vacuum-cleaned or a lawn to be mowed, employs a plurality of distance measuring devices, which continuously and repeatedly measure distances from the robot to points or small surface areas defining the surface to be worked. Electro-optical distance measuring devices are effective in a far range. Electro-acoustical distance measuring devices are effective in a close range. Electro and/or mechanical means are effective in a contact range. The distance measuring devices continuously ascertain scalar values which by means of data processing are transformed into digital control signals for the drive means and for the tools carried by the robot, whereby the robot plans its own driving and working strategies as the result of said continuous distance measurements.

Abstract: In a method and apparatus for determining the level of liquid in a container, a vertical gas filled tube is provided in the container. The tube is surrounded by a magnetic float. A magnetic follower in the tube follows the vertical position of the magnet float, and serves as the termination point of an optical measuring path between a light source and a detector. An optical reference path also extends from the light source to a second mirror, which may be mounted at a fixed point in the container or on the opposite side of the follower. The system incorporates means for determining the difference in propagation time of light in the two optical paths.