Magnetic Adsorption Wall Climbing Robot
Magnetic adsorption wall climbing robots are extensively used for surface inspection, maintenance, and repair of ships, large chemical storage tanks, and steel structures, thereby avoiding high-risk work and lowering the occurrence of accidents. The research status of magnetic adsorption wall climbing robots at home and abroad is summarized using the three main adsorption methods of magnetic adsorption wall climbing robots: permanent magnetic adsorption, electromagnetic adsorption, and electric permanent magnetic adsorption, and the main development trend of future magnetic adsorption wall climbing robots is given using the magnetic adsorption methods and application scenarios to provide a reference basis.
KEYWORDS: Magnetic adsorption, Wall Climbing Robot, Research Status, Detection
1 INTRODUCTION
With the growing demand for ocean transportation, the number of large and super-large tonnage ocean-going cargo ships is increasing. The surface of the large hull made of metal materials is often corroded due to the constant wind and sunshine and the erosion of seawater and the adhesion of marine microorganisms on the surface of the hull[1]. If maintenance is not carried out in time, with the deepening of corrosion, the overall structure of the hull will be further damaged, thus endangering the lives and properties of the crew[2], so the surface of the ship needs to be regularly maintained and so on. This is also true for the large chemical industry, where large storage tanks and steel structure surfaces need regular inspection and maintenance due to the constant exposure to the elements. The maintenance of large ships’ hull surfaces, large storage tanks and large steel structures in the chemical industry are mostly carried out manually, and in this operating environment, it is difficult to improve the efficiency of manual work and highly dangerous when manual work is used[3].
Permanent magnetic adsorption, electromagnetic adsorption, and electro-permanent magnetic adsorption are the three main adsorption methods of magnetic adsorption wall climbing robots at present. Permanent magnet adsorption: As the name suggests, it relies on the magnetic force of permanent magnets to adsorb the chassis on top of the wall, its structure is simple and reliable, but the magnetic force is not adjustable, applicable to a single scene.; the electromagnetic adsorption method, i.e., the source of magnetic force is generated by electricity, which can be flexibly adjusted but requires cable power supply, otherwise the range will be greatly reduced, which is not conducive to wireless operation[4]; the electro-permanent magnet adsorption method, in which permanent magnets and reversible magnets are embedded in the magnet, takes into account the simplicity and reliability of permanent magnets and the advantages of adjustable magnetic force of electromagnets.
Magnetic Adsorption Wall Climbing Robot
2 CURRENT STATUS OF RESEARCH ON MAGNETIC ADSORPTION WALL CLIMBING ROBOTS
2.1 Permanent magnetic adsorption wall climbing robot
Japan was the first to conduct research on permanent magnet wall climbing robots and to develop them, going back to the 1980s. The eight-legged magnetic adsorption wall crawler robot shown in Figure 1 was developed by Shinji Naito and Main Tax Sato of Hitachi, and the robot realized the principle of adsorption walking by the four feet of the inner and outer layers, which alternately adsorbed and slid to walk[5]. W. Fischer and F. Tache[6] of ETH Zurich, Switzerland, suggested a pair of “mother and child” wall climbing robots with magnetic wheels for adhesion that can easily cross obstacles such as welding seams to detect the inner surface of overseas ship tanks. As shown in Figure 2,the smaller robot (child) is very light and basic in construction, with no vertical steering or climbing capability. It only travels horizontally and follows the ridges on the tank’s surface as guides. The smaller robot (child) rests on the larger robot (mother). The robot (mother) never enters the extremely fragile surfaces and always remains in the thicker areas of the sheet metal. As a result, the mass of this robot can easily cope with structures in a variety of environments, thus allowing this wall-climbing robot to climb and follow its path through difficult obstacles in all gravity directions without any size limitations.
Mahmoud Tavakol[7] developed a permanent magnet wall climbing robot that can be well adapted to avoid metal with a certain curvature, as shown in Figure. 3. The robot has a relatively simple structure, but has strong mobility to move on metal walls within a certain curvature range, which is more applicable.
Adrián Peidró [8] from Miguel Hernández University, Spain, developed a gripper structure based on permanent magnets that can be used on the HyReCRo robot, as shown in Figure 4. equipped with this structure, the HyReCRo robot can be used for the inspection and maintenance of steel structures. The principle is that the gripper is designed with switchable magnets and rubber pads, both of which are switched back and forth when adsorbing and detaching from the wall, so that the gripper can sometimes adsorb on the wall and sometimes detach from the wall, combined with another gripper alternately.
Nguyen Son Thanh [9] at the University of Nevada, USA, developed a wall-climbing robot with a tank-like shape, as shown in Figure 5, which is highly adaptable for in steel structures and can be used for tasks such as inspection, maintenance, and data collection of steel structures of different sizes. Its crawling principle is based on the integration of a reciprocating device and a roller chain composed of magnets on the adsorption mechanism, so that it can crawl on steel structure surfaces of different shapes.
Yogo Takada [10] of Osaka City University, Japan, developed a two-wheel-drive wall-climbing robot that can cross right angles to address the problem that wall-climbing robots have difficulty climbing at right-angle positions on walls, as shown in Figure 6. Each spoke was equipped with a neodymium magnet. The non-driven wheels are mounted as rotatable casters at the back. The robot can be rotated in place to avoid bolts in the splice section, and its performance was verified experimentally. The findings show that the robot follows the internal right-angle path in the laboratory and in the real world, which corresponds to a bridge box girder. Manual control of the robot in the splice section is extremely difficult. The findings indicate that Yogo Takada et al.’s newly developed robot can pass through the spliced section without hitting the nut. Tsukuba University’s Wang Rui[11] and colleagues created a compact robot with four magnetic wheels for steel bridge examination, as shown in Figure 7. The principle of movement is based on a modified light magnetic wheel unit, which has a high adsorption and friction force on the metal wall surface. The main advantage of this robot is its simple, compact and lightweight mechanical structure, and thanks to the robot’s four active and two passive degrees of freedom, it can crawl on a variety of complex walls, such as vertical surfaces, top walls and 90° right-angle transition surfaces in various forms, and can withstand almost any gravitational tendency.
Park Changmin [12] of Hanyang University, Korea, developed a wall-climbing robot called R-track that can be connected in parallel, as shown in Figure 8. The robot has a modular design and can be connected several in parallel to facilitate passing through right-angle walls or other walls with a certain curvature, and the permanent magnets integrated in the tracks on both sides provide a certain adsorption force for the robot. And through actual crawling tests, it has been demonstrated that the robot can pass through the transition surfaces between walls.
On the issue of transition or curvature between walls, domestic scholars have also conducted some research work. Especially in the process of automatic cleaning of ships, it is difficult for wall climbing robots to cross the transition surface of the ship surface. Chen Jiankun [14] from the Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, developed a permanent magnetic wall crawler robot that can easily cross the transition surface of the ship surface with respect to this problem, as shown in Figure 9. and carried out bilge transition experiment, cabin top transition experiment and wall transition comprehensive experiment on this robot to verify that the robot The robot has adaptive capability. Zhao Fei [14] from Zhenjiang Higher Institute of Technology addressed the wall attachment stability of the crawler wall climbing robot equipped with a high-pressure water jet device, established the corresponding kinematic model based on the chassis structure of the designed robot, and conducted indoor horizontal walking, vertical wall climbing and 1:1 real wall climbing experiments on the constructed functional prototype, as in Figure 10, to verify the correctness of the analysis results.
Weipeng Wang [15] from Hebei University of Technology developed a wall crawling robot that can be applied to the curvature wall of wind turbine towers, as shown in Figure 11,to perform inspection work on the surface of wind turbine towers. The robot’s magnetism was verified to some extent using finite element simulation, as well as through actual crawling tests, and the results proved that the robot can be well applied to the surface of wind turbine towers. Mingqiang Wang [16] of Jiangsu University of Science and Technology et al. developed an omnidirectionally movable multi-track wall crawler robot for the reliability of permanent magnetic wall crawler robot walking on the wall, as shown in Figure. 12, which avoids the safety problems caused by the traditional crawler due to differential steering, and verified the reliable adsorption of this omnidirectionally movable permanent magnetic wall crawler robot at any angle on the wall by building a prototype.Shanqiang Wu[17] from China Institute of Metrology developed a variable adsorption force wall climbing robot based on permanent magnets, as shown in Fig. 13.The permanent magnets inside this robot are not in direct contact with the wall, and there is a certain gap between them, both by adjusting this gap, this robot achieves variable adsorption force of the permanent magnet wall climbing robot, which makes the robot more applicable scenarios and more adaptable.
2.2 Electromagnetic adsorption type wall climbing robot
Palangwatanakul Richit [18] from Mahasarakham University, Thailand, designed an adaptive electromagnetic adhesion force mechanism for a magnetic wheel type curvature surface climbing robot.The proposed magnetic wheel climbing robot is designed as a two compartment segment locomotive robot as shown in Figure 14. The electromagnetic force is controlled by a PID controller and the adhesion force is measured by a load cell. The robot’s two independent modular designs enable it to move along a curved surface with six magnetic wheels to enhance the robot’s adhesion force to the steel surface. Each wheel is made up of eight 10 x 10 mm neodymium magnets and two 75 mm outer plates. Electromagnets were used to provide the adhesive force, which could be adjusted to the required level. Each electromagnet is positioned between two axles. Between the framework and the electromagnets are three load cells. The load cells are used as force sensors to sense the electromagnets’ adhesion force.
Özgür Acar [19] from Yildiz Technical University, Turkey, et al. designed an autonomous wall climbing robot for tank inspection as shown in Figure 15. on the mechanical part Özgür Acar used Solidworks for design and simulation, and on the control part Özgür Acar et al. proposed that the electromagnetic system must provide the necessary current to control the magnetic force to be strong enough to make the robot attach to the wall. Sensor fusion and Kalman filtering are considered for position estimation solving. Simulation analysis using MATLAB for the position control and tracking performance control of the wheel demonstrates that the robot system is able to track the exact trajectory given by the defined kinematic equations.
Tsinghua University’s Wendong Zhang [20] and colleagues created a reconfigurable soft wall-climbing robot powered by electromagnets, as shown in Figure 16, capable of translational, deflective, and rotational motions while operating on an inclined ferromagnetic wall. The robot is made up of two kinds of modules that can be linked together using embedded magnets. It can be reconfigured under various working conditions and used for flaw detection, surface cleaning, and ferromagnetic structure exploration. Han Lichun[21] of Naval Engineering University et al. used the adjustable magnetic force of an electromagnet to solve the problem of a wall climbing robot’s non-adjustable adsorption force with permanent magnets as the source of adsorption force, and developed and designed an electromagnet based on the mechanical model of the wall climbing robot. The magnetic force-spacing variation between the electromagnet and permanent magnet was compared, and the analysis demonstrated that the electromagnet can meet the adsorption force requirements of the robot chassis, and the electromagnetic adsorption force can be adjusted for different use scenarios. However, the model is still in the theoretical stage, and there is no real prototype for validation.
Hong Xiaowei [22] of Nanjing Forestry University created an electromagnet-tracked wall-climbing robot by designing an electromagnet-based rotating with power-off system, as shown in Figure 17. The whole robot model was built and tested. It was also demonstrated that the wall-climbing robot constructed on this mechanism could scale the wall at any angle with various attitudes. Zhang Garun [23] from North China University of Technology proposed a wall crawling robot based on electromagnetic adsorption, and his group developed a footed wall crawling robot applied to the surface of large metal equipment mainly for rust removal, cleaning, grinding and other related operations, which benefits from high motion accuracy, light weight, and small dimension.
2.3 Electro-permanent magnet adsorption type wall climbing robot
The principle of electric permanent magnet magnetization is that there are several permanent magnets and reversible magnets arranged in a certain way inside the electric permanent magnet, and the coil is wound on the reversible magnet. When the current is passed into the reversible magnet, the magnetic inductance direction is the same as the direction of the permanent magnet, the whole piece of electric permanent magnet is magnetized, and the magnetic force still exists after power off. On the other hand, when the current in the coil makes the reversible magnet produce magnetic inductance in the opposite direction of the permanent magnet, the whole electric permanent magnet is not magnetic, i.e., demagnetized. The electric permanent magnet reverses the electromagnetic technology and permanent magnet technology, combining the advantages of electromagnet and permanent magnet in one, filling the defects of each of them [24-26].
According to the data research, there are relatively few studies on wall climbing robots for the electro-permanent magnet technology. Zhu Jiayi [27] of Shanghai Shengu Electronic Technology Co., Ltd. applied for a patent based on an electro-permanent magnet suction crawler, as shown in Figure 18, which is built on electro-permanent magnet characteristics and fixes the electro-permanent magnet to the crawler, and has an incoming and demagnetizing position, and the charging and demagnetizing controller has a charging end and a demagnetizing end. It can maintain the suction force even when the power is cut off, avoiding the robot from falling down. Kang Yang Liang of Guangdong Ocean University [28] invented an adsorption hull refinishing robot, as shown in Figure 19, including a walking track chassis and an electric permanent magnet. The electric permanent magnet is attached to the crawler chassis’s bottom surface, and the magnetic force of the electric permanent magnet provides the adsorption force on the chassis’s wall. It solves the problem of manual hull refinishing and the physical damage to personnel caused by paint. However, no real prototype of this patent’s electric permanent magnet wall climbing robot has been seen.
The rare earth permanent magnet team of Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences has modified the traditional permanent magnet tracked and footed wall climbing robots according to the electric permanent magnet technology as shown in Figure 20(a) and Figure 20(b). The original permanent magnet type crawler and foot type wall climbing robot bottom added electric permanent magnet suction cup, and the break electromagnetic force still exists the advantage of the traditional permanent magnet type chassis to improve adaptability, can be flexible in different angle wall walking. The motor load is reduced and the service life is prolonged while ensuring safe adsorption by adjusting the size of the electric permanent magnet adsorption force.
3 SUMMARY
According to the current domestic and foreign literature related to magnetic adsorption wall climbing robots, as can be seen, the majority of the study literature focuses primarily on permanent magnet adsorption chassis, with the advancement of technology in electromagnetic adsorption and electric permanent magnet adsorption methods, adsorption of magnetic particles The chassis of a wall climbing robot is also progressively evolving in the direction of electromagnetic and electric permanent magnet adsorption. Current study on magnetically adsorbed wall climbing robots at home and abroad reveals future research directions:
Adaptivity of adsorption: permanent magnetic adsorption is a single application scenario due to the immutability of the magnetic force. At present, the source of magnetic force is more in the direction of electromagnetic and electric permanent magnet development, electromagnetic and electric permanent magnet adsorption can be used according to different scenarios, the size of the active adjustment of magnetic force to apply different operating environments, the electromagnetic or electric permanent magnet adsorption technique of wall climbing robot chassis is thought to be the future growth path.
Flexible chassis structure: the chassis structure of wall climbing robots generally uses a rigid structure, resulting in the chassis can not adapt to curved surfaces, transition surfaces or other forms of curved walls, and ships or other forms of metal walls are often more complex, the rigid structure of the magnetic adsorption chassis can not adapt well to the different curvature of the wall, so the chassis needs to have a certain degree of flexibility to adapt to the different curvature of the wall, the current flexible structure in the chassis or parallel structure related research is less, so with the increase in the requirements of the applicable scenario of the chassis, the flexible chassis structure will also be a hot research direction for future magnetic adsorption wall climbing robots.
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