Study on the Optimal Design for Cavitation Reduction in the Vortex Suction Cup for Underwater Climbing Robot

In order to adhere to the wall stably in an underwater environment, a vortex suction cup that injects high-pressure water inside via two axisymmetrically side-distributed inlets to create a negative pressure area in the center is the necessary component for the underwater climbing robot (UCR). However, the suction force of this vortex suction cup is reduced and periodically unstable due to unstable cavitation. The aim of this paper is to propose a cavitation reduction optimization method for vortex suction cups and to verify the effectiveness of the optimization. Analyses of this vortex flow, including streamlines, pressure, and cavitation number fluctuations, were carried out by the introduced computational fluid dynamics (CFD) simulating methods based on the multiphase RNG k−ε model to study the periodic fluctuations of the suction force of the original suction cup and the optimized ones. Force measurement and vortex observation experiments were conducted to compare the suction force of the original vortex suction cup and the optimized suction cup, as well as the cavitation and pressure fluctuation phenomenon. Results of simulation and experiments prove the existence of the effect of vortex cavitation on the suction performance and verify the rationality of optimization as well.

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Experimental study of vortex suction unit-based wall-climbing robot on walls with various surface conditions

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/0954406218791203 ◽

2018 ◽

Vol 232 (21) ◽

pp. 3977-3991 ◽

Cited By ~ 5

Author(s):

Jianghong Zhao ◽

Xin Li ◽

Jin Bai

Keyword(s):

Vortex Flow ◽

Functional Relationship ◽

Flow Direction ◽

Vortex Chamber ◽

Wall Surface ◽

Climbing Robot ◽

Suction Force ◽

Surface Conditions ◽

Wear And Tear ◽

Suction Performance

This study presents a wall-climbing robot called Vortexbot. Vortexbot has a suction unit that uses vortex flow to generate a suction force. Unlike the traditional unit based on contact-type suction, the suction unit can maintain a suction force without any contact with the wall surface. Therefore, the suction unit can provide a climbing robot with sufficient stable suction force even on walls with very rough surfaces and raised obstacles/grooves, and there is no wear and tear. Furthermore, the compressed air vents from the gap between the suction unit and the wall surface after rotating in the vortex chamber. Hence, such kind of flow direction can avoid the effect of the dust and dropped items on the wall surface. In this paper, we first introduced the vortex suction unit principle and discuss the feasibility of its application to a wall-climbing robot. Subsequently, the mechanical structure of Vortexbot was designed. After which, we surveyed the suction properties of the suction unit on a smooth wall surface. Then the functional relationship between the percentage change in the suction force and the supply flow rate was obtained. In addition, we studied the effect of the roughness and shape (a raised obstacle and groove) of the wall surface on the suction performance of the suction unit. Finally, we experimentally verified the climbing performance of Vortexbot on several kinds of walls with different surface conditions. It was confirmed that using the suction unit improves the robot’s climbing performance.

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Theoretical and Experimental Study and Design Method of Blade Height of a Rotational-Flow Suction Unit in a Wall-Climbing Robot

Journal of Mechanisms and Robotics ◽

10.1115/1.4045652 ◽

2020 ◽

Vol 12 (4) ◽

Cited By ~ 1

Author(s):

Ningning Chen ◽

Kaige Shi ◽

Xin Li

Keyword(s):

High Speed ◽

Design Method ◽

Rotational Flow ◽

Climbing Robot ◽

Suction Force ◽

Blade Height ◽

Computational Fluid Dynamics Cfd ◽

Cfd Method ◽

Motor Operation ◽

The Relationship

Abstract 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).

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Soft Hybrid Suction Cup Capable of Sticking to Various Objects and Environments

Actuators ◽

10.3390/act10030050 ◽

2021 ◽

Vol 10 (3) ◽

pp. 50

Author(s):

Hideyuki Tsukagoshi ◽

Yuichi Osada

Keyword(s):

Vertical Direction ◽

Check Valve ◽

Adhesive Force ◽

Outer Diameter ◽

Shear Direction ◽

Concrete Walls ◽

Suction Force ◽

Suction Cup ◽

Valve Function ◽

Suction Cups

A universal suction cup that can stick to various objects expands the areas in which robots can work. However, the size, shape, and surface roughness of objects to which conventional suction cups can stick are limited. To overcome this challenge, we propose a new hybrid suction cup structure that uses the adhesive force of sticky gel and the suction force of negative pressure. In addition, a flexible and thin pneumatic balloon actuator with a check valve function is installed in the interior, enabling the controllable detachment from objects. The prototype has an outer diameter of 55 mm, a weight of 18.8 g, and generates an adsorption force of 80 N in the vertical direction and 60 N in the shear direction on porous walls where conventional suction cups struggle to adsorb. We confirmed that parts smaller than the suction cup and fragile potato chips are adsorbed by the prototype. Finally, the effectiveness of the proposed method is verified through experiments in which a drone with the prototypes can be attached to and detached from concrete walls and ceilings while flying; the possibility of adsorption to dusty and wet plates is discussed.

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Investigations of Inducers Operating With High Rotational Speed

Journal of Fluids Engineering ◽

10.1115/1.4041730 ◽

2018 ◽

Vol 141 (4) ◽

Cited By ~ 1

Author(s):

Björn Gwiasda ◽

Matthias Mohr ◽

Martin Böhle

Keyword(s):

Rotational Speed ◽

Test Bench ◽

Pressure Rise ◽

Working Fluid ◽

Cfd Simulations ◽

High Rotational Speed ◽

Rotating Speed ◽

Performance Pressure ◽

Computational Fluid Dynamics Cfd ◽

Suction Performance

Suction performance, pressure rise, and efficiency for four different inducers are examined with computational fluid dynamics (CFD) simulations and experiments performed with 18,000 rpm and 24,000 rpm. The studies originate from a research project that includes the construction of a new test bench in order to judge the design of the different inducers. This test bench allows to conduct experiments with a rotational speed of up to 40,000 rpm and high pressure ranges from 0.1 bar to 40 bar with water as working fluid. Experimental results are used to evaluate the accuracy of the simulations and to gain a better understanding of the design parameter. The influence of increasing the rotating speed from 18,000 rpm to 24,000 rpm on the performance is also shown.

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Study on Mechanism of Series-Flow of Pollutants between Consecutive Tunnels by Numerical Simulation

Applied Sciences ◽

10.3390/app9194125 ◽

2019 ◽

Vol 9 (19) ◽

pp. 4125

Author(s):

Honghu Zhang ◽

Yunge Hou ◽

Kaijie Wu ◽

Tianhang Zhang ◽

Ke Wu ◽

...

Keyword(s):

Negative Pressure ◽

Velocity Ratio ◽

Three Dimensional ◽

Wall Jet ◽

Air Velocity ◽

Pressure Area ◽

Computational Fluid Dynamics Cfd ◽

Jet Theory ◽

Jet Characteristics ◽

Tunnel Entrance

The characteristics of series-flow between two consecutive tunnels with distance ranging from 20 m to 250 m are explored by computational fluid dynamics (CFD) parametric simulations of structure and operation parameters. The research indicates that series-flow can be considered the three-dimensional wall jet diffusion of upstream tunnel pollutants under the effects of the negative pressure area of the downstream tunnel entrance. The jet characteristics are primarily related to the tunnel distance between upstream and downstream tunnels and hydraulic diameters, and only influenced by the negative pressure in the area very close to downstream entrance where the tunnel air velocity ratio, i.e., the velocity of upstream tunnel air divided by the velocity of downstream tunnel air, decides the degree of the influence. If ignoring the effects of ambient wind and traffic flow, the series-flow ratio decreases with the increasing of parameters of the normalized tunnel distance, i.e., the tunnel distance divided by tunnel hydraulic diameter, and the tunnel air velocity ratio. Based on the three-dimensional wall jet theory, a series-flow model covering all jet characteristic sections is built. The experiment results indicate that the model applies to consecutive tunnels with any spacing and exhibits higher prediction accuracy.

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A Pressing Attachment Approach for a Wall-Climbing Robot Utilizing Passive Suction Cups

Robotics ◽

10.3390/robotics9020026 ◽

2020 ◽

Vol 9 (2) ◽

pp. 26

Author(s):

Dingxin Ge ◽

Yongchen Tang ◽

Shugen Ma ◽

Takahiro Matsuno ◽

Chao Ren

Keyword(s):

Experimental Test ◽

Experimental Results ◽

Climbing Robot ◽

Guide Rail ◽

Test Bed ◽

Climbing Robots ◽

Pressing Method ◽

Suction Cup ◽

Suction Cups

This paper proposes a pressing method for wall-climbing robots to prevent them from falling. In order to realize the method, the properties of the utilized suction cup are studied experimentally. Then based on the results, a guide rail is designed to distribute the attached suction cup force and implement the pressing method. A prototype of a wall-climbing robot that utilizes passive suction cups and one motor is used to demonstrate the proposed method. An experimental test-bed is designed to measure the force changes of the suction cup when the robot climbs upwards. The experimental results validate that the suction cup can completely attach to the surface by the proposed method, and demonstrate that the robot can climb upwards without falling.

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Analysis of the Pneumatic System Parameters of the Suction Cup Integrated with the Head for Harvesting Strawberry Fruit

Sensors ◽

10.3390/s20164389 ◽

2020 ◽

Vol 20 (16) ◽

pp. 4389

Author(s):

Sławomir Kurpaska ◽

Zygmunt Sobol ◽

Norbert Pedryc ◽

Tomasz Hebda ◽

Piotr Nawara

Keyword(s):

Testing Machine ◽

Equivalent Diameter ◽

Strawberry Fruit ◽

Measurement Instruments ◽

Suction Force ◽

Practical Applications ◽

Surface Areas ◽

Suction Cup ◽

Suction Cups ◽

End Effectors

Fruit and vegetable harvest efficiency depends on the mechanization and automation of production. The available literature lacks the results of research on the applicability of pneumatic end effectors among grippers for the robotic harvesting of strawberries. To determine their practical applications, a series of tests was performed. They included the determination of the morphological indicators of the strawberry, fruit suction force, the real stress exerted by fruit suckers and the degree of fruit damage. The fruits’ morphological indicators included the relationships between the weight and geometrical dimensions of the tested fruit, the equivalent diameter, and the sphericity coefficient. The fruit suction force was determined on a stand equipped with a vacuum pump, and control and measurement instruments, as well as a MTS 2 testing machine. The necrosis caused by tissue damage to the fruits by suction cup adhesion was assessed by counting the necrosis surface areas using the LabView programme. The assessment of the necrosis was conducted immediately upon the test’s performance, after 24 and after 72h. The stress values were calculated by referring the values of the suction forces obtained to the surface of the suction cup face. The tests were carried out with three constructions of suction cups and three positions of suction cup faces on the fruits’ surface. The research shows that there is a possibility for using pneumatic suction cups in robotic picking heads. The experiments performed indicate that the types of suction cups constructions, and the zones and directions of the suction cups’ application to the fruit significantly affect the values of the suction forces and stresses affecting the fruit. The surface areas of the necrosis formed depend mainly on the time that elapses between the test and their assessment. The weight of strawberry fruit in the conducted experiment constituted from 13.6% to 23.1% of the average suction force.

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