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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.

A wall-climbing robot that uses a rotational-flow suction unit to be non-contact-absorbed onto walls can climb rough walls and overstep obstacles. In the rotational-flow suction unit, the air driven by the blades rotates at a high speed within a chamber, thereby creating and maintaining a negative pressure distribution. This study is focused on the modeling and design of the blade height. First, a theoretical model of the rotation flow, containing two important parameters (i.e., blade height Hb and clearance h), was established and verified experimentally. Furthermore, the computational fluid dynamics (CFD) method was applied to illustrate the secondary flow relative to the blades, revealing that it gives rise to a nonlinear velocity distribution. It was found that an increase in the blade height greatly improves the F–h characteristics; in addition, the relationship between the power consumption and suction force (E˙−F curve) is mainly determined by the clearance h instead of the blade height Hb. Based on these findings, we propose a design method for determining the suitable blade height. According to the characteristic load curves of the suction units (i.e., the T–ω curves) and the motor characteristics, suitable blades can be selected to match the motor operation (i.e., nominal operating state).

Air flotation rails are widely used in semiconductor production lines for handling components such as liquid crystal glass substrates and wafers. In this study, the effects of the number and distribution radius of the orifices of the basic component (hereinafter referred to as air flotation unit) of the utilized air-suspension orbit were theoretically and experimentally investigated. The pressure distribution of the air flotation unit was first calculated using the Reynolds equation. The flotation forces and two-dimensional pressure fields of six different air flotation units with different numbers and distribution radii of the orifices were then experimentally measured. Based on the experimental data, we analyzed the effect of the inertia item of the flow, the impact of the no-flow region within the distribution circle, and the changes brought about by the number and distribution radius of orifice, etc. The findings of this study afford important theoretical and experimental references for the design of air flotation rails.