HOBOT-188 is able to imitate the human behavior to clean the window, especially let end-users make good use of removing stubborn stains on top or outside of the window. HOBOT-188 has two specially-designed cleaning wheels instead of a driving tread. It can move freely and smoothly on the window surface without any tracks left, even if the cleaning clothes are dirty. Additionally, our micro-fiber cleaning clothes on both cleaning wheels are easily replaceable and washable.