Abstract: The present invention relates to a method for controlling a self-propelled robot device, such as a robot device for mowing grass, and a control system that carries out the aforementioned method. According to the invention, the self-propelled robot device is driven by an inertial navigation system for a set time period or distance and the device is periodically stopped for rectifying the position and advancing course thereof by a satellite detection system: the periodic correction of the inertial navigation system using satellite detections thus prevents course errors from accumulating. The correction based on the satellite detection system can be possibly optimized through a further selection of the obtained values according to a statistical basis. Preferably, the control method according to the invention also provides a procedure for detecting, recording and mapping the operating region wherein the device is operated.

Abstract: A cutting head for a nylon-cord mower and the like, comprising a case housing an inner spool on which it is wound at least a length of nylon cord, elastically loaded by a helical spring, with the two ends of said nylon cord protruding through pairs of annular members mounted on said case in diametrally opposed locations. The inner spool is formed by a cylindrical body with at least two holes aligned along an axis intersecting the axis of the spool, and that can be axially aligned with the two annular members for allowing the replacement of the nylon cord without opening the cutting head.