Patent ID: 7970493

Claim:
A robot-ship group for executing a work operation on sea and river, the robot-ship group comprising: at least one working robot; a first mother ship having the at least one working robot; and a second mother ship whose communication region is overlapped with a communication region of the first mother ship, wherein the at least one working robot includes: a signal strength measurement means for measuring strength of pre-defined signals transmitted from the first mother ship and the second mother ship; and a working robot control means for determining which of the first mother ship and the second mother ship the at least one working robot is to communicate with according to a comparison result of the signal strength measured in the signal strength measurement means, and controlling the at least one working robot to perform the work according to a set-up route, and wherein the first mother ship includes: a working robot preparing unit for performing a preparation work required before and after the at least one working robot performs the work; and a mother ship control unit for transmitting a pre-defined signal to the at least one working robot after said performing by the working robot preparing unit, wherein the working robot control means calculates an average value of the signal strength measured by the signal strength measurement means at a predetermined time and determines which of the first mother ship and the second mother ship the at least one working robot is to communicate with.