HOBOT square-shaped window cleaning robot rises to the top of the glass pane and then executes right/left/down pattern followed by up/down polishing pattern. It essentially covers the surface area twice for better cleaning results. The ultrasonic water spray sprinkles fine mist of cleaning detergent or water during horizontal left/right movement. It does not spray during the vertical polish.
Two caterpillar belts allow HOBOT to move quickly at the speed of almost 1 inch per second, that's about 4 square feet per minute. These robots are best used when there is little or no wind as the mist can be blown away rather than wetting the window. It's also best to use these robotic window cleaners in low humidity environment. If you live near the coast or in high humidity climates, consider purchasing HOBOT-388 with round wheels that rotate in counter directions. It handles high humidity envirinments best.
In summary, HOBOT's square-shaped window cleaning robots are preprogrammed to work in zigzag routes first horizontally then vertically to achive best cleaning results.