Solar panels must be constantly kept clean to work in a properly and efficient way. The only economically viable way to do this is to use autonomous robots: devices that through the use of appropriate sensors can move independently on the panels, operating the cleaning systems only on the active area of the panel itself. These robots must be able to see the gap between one panel and the next one so that they can move in an appropriate manner. UK6 ultrasonic sensors represent the best solution because of their compactness: the short body allows the installation even in restricted spaces. Furthermore, the UK6 offers both digital and analogue outputs. The ultrasonic technology overcomes all the possible issues related to the external light or dusty environments.