Vacuum suction units are widely used in various manufacturing lines, climbing robots, etc. Their most difficult problem is vacuum leakage, which leads to suction failure. Vacuum leakage is traditionally prevented by blocking the flow path between the atmosphere and the vacuum zone, which is difficult for a suction unit working on a rough surface. This paper proposes using the zero pressure difference (ZPD) method, which is based on a completely different mechanism. The ZPD method eliminates the pressure difference at the boundary of the vacuum zone, so vacuum leakage can be prevented regardless of the roughness of the working surface. A new vacuum suction unit based on the ZPD method was designed, fabricated, and tested. The ZPD suction unit forms a rotating water layer on the periphery of the vacuum zone, and the resulting inertial force generates a steep pressure gradient so that a high vacuum is maintained at the center of the vacuum zone while the pressure at the boundary remains equal to the atmospheric pressure. Experiments showed that a 0.8-kg ZPD suction unit generated a suction force of over 245 N on rough surfaces with a power consumption of less than 400 W. In contrast, a traditional suction unit of the same size would need a vacuum pump consuming several kilowatts and weighing dozens of kilograms to generate a similar suction force because of severe vacuum leakage. The ZPD suction unit was then successfully applied to a robotic arm, wall-climbing robot, and spider-man wall-climbing device.

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