“…Vacuum can be produced by using an electrical vacuum generator or by external hydraulic vacuum generator (Venturi effect) connected to the robot by flexible tubes, vacuum pump is installed on the robot that keeps the negative pressure in each cup at constant level if significant leakage occurs (See Figure 3). Examples for such robots are V-ROBO [29, 40], RIMINI [41, 42], ROMA II [43], Vacuum Lizard [30], Sky Cleaner 3 [44], RAMR1 [45], crawling robot for cleaning [46, 47].…”