Abstract: A vacuum cleaner including a cleaner head defining a suction chamber and having an agitator arranged to be rotated by an agitator motor, a dirt separator, a vacuum motor arranged to draw air into the suction chamber and then into the dirt separator, and a controller. The controller is configured to monitor the electrical load of the agitator motor, compare the magnitude of the electrical load to a threshold, and selectively adjust the electrical power delivered to the vacuum motor. The controller is configured either to increase the electrical power delivered to the vacuum motor to a predetermined upper power level if the electrical load is greater than the threshold, or to decrease the electrical power delivered to the vacuum motor to a predetermined lower power level if the electrical load is smaller than the threshold.

Abstract: A device for detection of undesired objects on surfaces, for example airport runways co-ordinates sensed data from a plurality of sensor units. With radar sensors, synthetic aperture radar processing is found to be advantageous. A vehicle which is configured with a plurality of sensors may be either remotely controlled or autonomous. It may also be provided with communication equipment and debris retrieval apparatus and that includes both mobile sensing devices and fixed installations. A suitable mobile sensing device and a method for operating the debris detection system are also provided.