Climbing Robot for Ferromagnetic Surfaces with Dynamic Adjustment of the Adhesion System

This paper presents a climbing robot with wheeled locomotion and adhesion through permanent magnets, developed with the intention of being used in the inspection of different types of man-made ferromagnetic structures, such as towers for wind turbines, fuel storage tanks, and ship hulls. In this paper are presented the main considerations thought for its project, as well as several constructive aspects, among which are detailed its mechanical and electrical construction, the implemented control architecture, and the human-machine interface developed for the manual and automatic control of the vehicle while in operation. Although it can be manually controlled, the vehicle is designed to have a semiautonomous behavior, allowing a remote inspection process controlled by a technician, this way reducing the risks associated with the human inspection of tall structures and ATEX places. The distinguishing characteristic of this robot is its dynamic adjustment system of the permanent magnets in order to assure the machine adhesion to the surfaces, even when crossing slightly irregular and curved surfaces with a large radius

Construção de um robô trepador com locomoção através de rodas e adesão através de meios magnéticos

Mestrado em Engenharia Electrotécnica e de ComputadoresO interesse no desenvolvimento de robôs do tipo trepador tem vindo a crescer rapidamente nos últimos anos. Os robôs trepadores são equipamentos úteis que podem ser adoptados numa variedade de aplicações, tais como na manutenção, na construção, na inspecção e na segurança, em indústrias de processo e da construção civil. Estes sistemas são essencialmente adoptados em locais onde o acesso directo por um operador humano é demasiado caro, devido à necessidade de montagem de andaimes, ou muito perigoso, devido à presença de um ambiente hostil. As principais motivações para a sua utilização prendem-se com o aumento da necessidade de maior eficiência nas operações a realizar, através da eliminação da montagem de andaimes, ou com a necessidade de protecção da integridade física dos trabalhadores humanos na realização de tarefas consideradas perigosas. Vários robôs trepadores foram já desenvolvidos, e outros encontram-se em desenvolvimento, para aplicações que vão desde a limpeza até à inspecção de construções de difícil acesso. Um robô trepador deve, não só, ser leve mas também apresentar uma elevada capacidade de carga, de forma a reduzir as forças de adesão necessárias e conseguir transportar equipamentos e instrumentos durante a sua navegação. Estas máquinas devem ser capazes de se movimentarem em diferentes tipos de superfícies, com diferentes inclinações, e de passarem de umas superfícies para as outras. Para além disso, devem ser capazes de se adaptarem a diferentes condições ambientais e de se reconfigurarem. Até à data, já foi dedicado um esforço significativo de investigação ao desenvolvimento destas máquinas e já foram propostos diferentes tipos de modelos experimentais. Os dois aspectos principais a considerar no desenvolvimento de robôs trepadores são os seus métodos de locomoção e adesão. Relativamente ao tipo de locomoção, são geralmente considerados três tipos de robôs: com segmentos deslizantes, com rodas e com pernas. Quanto ao princípio de adesão às superfícies, os robôs devem ser capazes de produzir uma força elevada utilizando um mecanismo relativamente leve. De acordo com o método de adesão utilizado, estes tipos de equipamentos são geralmente classificados em quatro grupos: por vácuo ou sucção, os magnéticos, por preensão à superfície e através de propulsão. Recentemente têm vindo a ser propostos novos métodos para assegurar a adesão, baseados em princípios de inspiração biológica. Este trabalho apresenta um tipo específico de robô trepador, que possui rodas para locomoção e pertence ao grupo dos robôs trepadores magnéticos, relativamente ao princípio de adesão adoptado. A sua diferenciação está associada ao mecanismo utilizado para controlar o sistema magnético de adesão, cujo principal objectivo é optimizar a produção de forças elevadas, e equilibradas, sobre a superfície e minimizar os atritos, independentemente das irregularidades que as superfícies a explorar apresentem. A sua principal aplicação será a utilização com o objectivo de inspeccionar diferentes tipos de estruturas ferromagnéticas para, por exemplo, detectar fragilidades devidas à corrosão, nomeadamente em depósitos de combustível, cascos de navios, etc. O robô terá um comportamento semi-autónomo, permitindo um processo de inspecção controlado à distância por um técnico especializado, reduzindo os riscos associados às inspecções em altura e em outros locais onde existem características associadas perigosas para a inspecção directa por humanos.The interest in the development of climbing robots is growing rapidly. Climbing robots are useful devices that can be adopted in a variety of applications like maintenance, building, inspection and safety in the process and construction industries. These systems are mainly adopted in places where direct access by a human operator is very expensive, because of the need for scaffolding, or very dangerous, due to the presence of an hostile environment. The main motivations are to increase the operation efficiency, by eliminating the costly assembly of scaffolding, or to protect human health and safety in hazardous tasks. Climbing robots have already been developed, and are being developed, for applications ranging from cleaning to inspection of difficult to reach constructions. A wall climbing robot should not only be light but also have large payload, so that it may reduce excessive adhesion forces and carry instrumentations during navigation. These machines should be capable of travelling over different types of surfaces, with different inclinations, such as floors, walls, ceilings, and to walk between such surfaces. Furthermore, they should be able of adapting and reconfiguring for various environment conditions and to be self-contained. Up to now, considerable research has been devoted to these machines and various types of experimental models have already been proposed. The major two issues in the design of wall climbing robots are their locomotion and adhesion methods. With respect to the locomotion type, three types are often considered: the frame walking, the wheeled and the legged types. Regarding the adhesion to the surface, the robots should be able to produce a secure gripping force using a light-weight mechanism. According to the adhesion method, these robots are generally classified into four groups: vacuum or suction cups, magnetic, gripping to the surface and propulsion type. Recently, new methods for assuring the adhesion, based in biological findings, have been proposed. This thesis presents a specific type of climbing robot, which has wheels for locomotion, and belongs to the magnetic climbers robots, based on the principle of adhesion adopted. Its differentiation is associated with the mechanism used to control the magnetic adhesion system, whose main objective is to optimize the production of high and balanced forces on the surface and minimize friction, regardless of the irregularities that the areas to explore present. Its primary application will be to inspect different types of ferromagnetic structures to, for example, detect weakness due to corrosion, particularly in fuel tanks, ship hulls, etc. The robot will have a semi-autonomous behavior, allowing an inspection process controlled remotely by a technician, reducing the risks associated with direct inspections in height and other characteristics associated with sites where there are hazardous to humans

Design of novel adaptive magnetic adhesion mechanism for climbing robots in ferric structures

The work presented in this thesis proposes a novel adaptive magnetic adhesion mechanism that can be implemented in most locomotion mechanisms employed in climbing robots for ferric structures. This novel mechanism has the capability to switch OFF and ON its magnetic adhesion with minimal power consumption, and remain at either state after the excitation is removed. Furthermore, the proposed adhesion mechanism has the ability to adapt the strength of the adhesive force to a desired magnitude. These capabilities make the proposed adhesion mechanism a potential solution in the field of wall climbing robots. The novel contributions of the proposed mechanism include the switching of the adhesive force, selectivity of the adhesive force magnitude; determination of the parameters that have an impact in the final adhesive force. Finally, a final prototype is constructed with customised components and it is subject to a set of simulations and experiments to validate its performance

A Dynamic Single Actuator Vertical Climbing Robot

Abstract — A climbing robot mechanism is introduced, which uses dynamic movements to climb between two parallel vertical walls. This robot relies on its own internal dynamic motions to gain height, unlike previous mechanisms which are quasistatic. One benefit of dynamics is that it allows climbing with only a single actuated degree of freedom. We show with analysis, simulations and experiments that this dynamic robot is capable of climbing vertically between parallel walls. We introduce simplifications that enable us to obtain closed form approximations of the robot motion. Furthermore, this provides us with some design considerations and insights into the mechanism’s ability to climb. I