A system for determining the effectiveness of the filtering and maneuverability of a robot for cleaning swimming pools, the robot includes a robot propelling motor, at least one water pump having an impeller and an impeller motor, a pool water inlet leading to a filter, a filtered water outlet, and a propelling mechanism for propelling the robot along the floor and/or walls of the swimming pool, the system comprising a computer for determining and setting an initial power to be supplied to the impeller motor, a first circuit for sensing the actual power supplied to the impeller motor during its operation, a second circuit for calculating the ratio between the set power and an instantaneous power supplied to said impeller motor, and a producer connected to the second circuit for producing an indication signal when the ratio exceeds a predetermined value. A controller for controlling the at least one impeller motor in consideration of the ratio; and a sensor for sensing the inclination of the floor and/or wall on which the robot is propelled are also provided.