Climbing ring robot for inspection of offshore wind turbines

A rapid expansion of wind turbine farms for sustainable electric power production is planned in Europe by 2020. At least in the UK, these will largely be located offshore to meet growing concerns about the visual intrusiveness and noise generation producedby onshore based farms. The necessary structural integrity inspection of offshore wind turbine blades poses tremendous problems of access, danger to human operatives and costs in the event of blades having to be taken out of service and transported on shore forschedules inspections. For these reasons robotic in-situ blade inspection of offshore wind turbines has been proposed and micro/nano focus computed axial X ray tomography (MNCAT) has been identified as the optimal if not the only solution for identification of safety critical defects in the thickest blade sections. The weight of such an inspection system is very high, typically 200kg and typical cross sectional scanner dimensions of 1 m × 2 m to encircle as blade, clearly involve very high destabilizing moments to be countered by the deployment robot. The solution is a climbing ring robot completely encircling a turbine tower, typically 3 meter in diameter, to provide the necessary adhesion forces and anti-destabilizing force moments. Because of the size and thus development costs of such a huge robot the optimal design path is to prototype a small scale model. First results on such a model are described and from its performance the load carrying capabilities of a full scale version can be computed and the scale model can then berefined by 'reverse engineering' to guarantee that a full scale construction is able tomeet requirements. The key design innovation is that the adhesive forces between the robot and climbing surface a provided entirely by mechanical means rather than by usingthe usual methods of vacuum suction or magnetic force, making the system much cheaper andeasier to manipulate. Furthermore the design is entirely modular. Copyright © 2008 by World Scientific Publishing Co. Pte. Ltd

A robot design for wind generator support structure inspection

In recent time, the development of wind tower inspection has been very crucial for the overall performance of the wind turbine. In order to maintain, monitor and determine the life span of the tower, an investigation of robot design is discussed. It presents how to design and construct a robot that can climb the tower and rotate 360° . A ring system which is in a circular shape robot is designed that allows the device to fit in the structure of the wind generator tower. The rotational module is designed to allow the wheels to rotate and be able to go in a circular motion. Also it is designed with a suspension that allows the robot to go through any obstacle. This paper also presents the FEA spring stress analysis and Simulink control system model to find the optimal parameters that are required for the wind tower climbing robot

Design and Development of a Mobile Climbing Robot for Wind Turbine Inspection

Wind turbines (WT) have become an essential renewable energy source as the contribution of WT farms has reached megawatts scale. However, wind turbine blades (WTB) are subjected to failure due to many loading effects such as aerodynamic, gravity and centrifugal loads and operation in harsh environments such as ultraviolet (UV) radiation, ice, hail, temperature variation, dirt, and salt. As a result, the blades suffer different types of damage. Consequently, a periodic inspection process is required to detect and repair defects before a catastrophic failure happens. This thesis presents a literature review of wall climbing robots to identify the most appropriate locomotion and adhesion method to use for a WT climbing machine that can take a large payload of non-destructive testing (NDT) sensors up to a blade and deploy them with scanning arms. A review of wind turbine blade construction, various loading effects on blades and types of damage in blades is followed by a review of the NDT techniques used for inspecting WTB. The above review determines the design requirements to achieve the aim of the current research which is to design a low-cost and reliable mobile robot which will be able to climb the WT tower and subsequently scan the blade surface to perform the inspection using various sensors to identify and classify damages. This robot system should be able to access all the critical areas of the blade structure in a stable and secure way. It should be stable enough to allow the various test sensors to scan the blade structure in the shortest possible time. The thesis describes the development of a tower climbing robot that uses magnetic adhesion to adhere to the WT. As a preliminary study, a simulation model is developed using COMSOL Multiphysics to simulate the magnetic adhesion force while climbing the tower. A test rig is designed and fabricated to measure the magnetic adhesion force experimentally to validate the simulation model. The response surface methodology (RSM) using Box-Behnken design (BBD) is used to design and perform experiments to optimise different independent variables i.e. air gap, the distance between magnets in an array and backplate (yoke) thickness that affect the magnetic adhesion force. A scaled-down prototype magnetic adhesion climbing robot has been designed and constructed for wind turbine blade inspection. The robot is 0.29 m long with two 1.0 m long arms, weighs 10.0 kg and can carry a maximum 2.0 kg payload of NDT sensors. Optimum design of a magnetic adhesion mechanism has been developed for the climbing robot prototype that maximises the magnetic adhesion force. The robot is equipped with two arms that can be extended by one meter to come close to the blade for inspection. Each arm is equipped with a gripper that can hold an inspection tool of weight up to one kilogram. A scaled-down wind turbine has been modelled using SolidWorks and a portion of it constructed to experimentally test the scaled-down climbing robot. To scale up the robot prototype for operation on a normal sized wind turbine, a 100 m tall wind turbine with three 76 m long blades has been modelled and the prototype robot scaled up based on these dimensions. The scaled-up robot is 3.0 m long, weighs 1135 kg and has two 10 m long arms. Static stress analysis and flow simulation have been carried out to check the durability of the scaled-up robot while climbing the wind turbine tower. The procedure for scaling up the adhesion mechanism to achieve equilibrium of the robot has been introduced based on the reaction force concluded from the static stress and flow simulation study. As a result, the maximum payload that each arm can carry has been calculated for both the scaled-down prototype (1 kg) and the scaled-up design (50 kg). This concludes the utility and robustness of the wall climbing robot as a robotic solution for wind turbine blade inspection

Design, Build, and Control of a Climbing Robot for Irregular Surface Geometry

Climbing robots are ideal for situations were maintenance and inspection tasks can cause people to be in dangerous situations or require them to be present for extended periods of time. Applications include inspection, testing, civil construction, cleaning, transport and security. The focus of this thesis was on robots that used pneumatic means to attain adhesion and wheels for locomotion. Research objectives include designing or utilizing a pneumatic based adhesion method to allow the robot to stick to concrete, brick, glass, or other such surfaces; climb on a surface with the lowest possible coefficient of friction between it and the robot; have the ability to overcome a step-like obstacle while climbing; use a single body to passively transition through sharp surface changes while climbing; have the ability to traverse over a gap-type obstacle while climbing without loss of adhesion or mobility. To complete the objectives, a test rig was created that comprised of three surfaces that were hinged together and could be locked into place using aluminum struts at the hinge joint. Different material pallets were created and adhered to plywood that was then mounted to the test rig with screws. The robot was designed and built around laser cut and 3D printed parts. From the experiments it was found that the robot could adhere to a glass surface with a coefficient of friction of 0.43 between it and the glass. Furthermore it was able to overcome a 15mm tall speedbump while climbing without loss of adhesion as well as being able to passively transition between surfaces that had an acute angle of 80° between them and do wall to ceiling transitions. Finally the robot was able to pass over a 55mm gap that was 23mm deep while climbing on a concrete surface. It was concluded that by using thrust based adhesion the robot could handle a diverse array of surfaces and even gain greater ability to overcome obstacles while climbing. Future directions would improve on the robot by adding treads or multiple bodies to improve its base abilities

Design, Build, and Control of a Climbing Robot for Irregular Surface Geometry

Climbing robots are ideal for situations were maintenance and inspection tasks can cause people to be in dangerous situations or require them to be present for extended periods of time. Applications include inspection, testing, civil construction, cleaning, transport and security. The focus of this thesis was on robots that used pneumatic means to attain adhesion and wheels for locomotion. Research objectives include designing or utilizing a pneumatic based adhesion method to allow the robot to stick to concrete, brick, glass, or other such surfaces; climb on a surface with the lowest possible coefficient of friction between it and the robot; have the ability to overcome a step-like obstacle while climbing; use a single body to passively transition through sharp surface changes while climbing; have the ability to traverse over a gap-type obstacle while climbing without loss of adhesion or mobility. To complete the objectives, a test rig was created that comprised of three surfaces that were hinged together and could be locked into place using aluminum struts at the hinge joint. Different material pallets were created and adhered to plywood that was then mounted to the test rig with screws. The robot was designed and built around laser cut and 3D printed parts. From the experiments it was found that the robot could adhere to a glass surface with a coefficient of friction of 0.43 between it and the glass. Furthermore it was able to overcome a 15mm tall speedbump while climbing without loss of adhesion as well as being able to passively transition between surfaces that had an acute angle of 80° between them and do wall to ceiling transitions. Finally the robot was able to pass over a 55mm gap that was 23mm deep while climbing on a concrete surface. It was concluded that by using thrust based adhesion the robot could handle a diverse array of surfaces and even gain greater ability to overcome obstacles while climbing. Future directions would improve on the robot by adding treads or multiple bodies to improve its base abilities

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

Dynamic digital shearography for on-board robotic non-destructive testing of wind turbine blades

Structural integrity plays a critical role in development of infrastructural construction and support facilities. During the lifespan of most large-scale equipment, condition monitoring and periodic inspection is indispensable for ensuring structural health and evaluation of service condition. Wind turbine blades are the most important component of wind turbines and demands regular inspection to detect defects, which often occur underneath a blade surface. Current methods used to inspect wind turbine blades include to send NDT operators to climb the tower for on-site inspection of the blades’ surface or to dismantle the blades for inspection on the ground. These approaches are time-consuming, costly and pose risks of injury to human inspectors. Thus, it is necessary to develop a technological method for wind turbine blade on-site inspection of wind turbine blades. Digital shearography based on laser interferometry has demonstrated its prominent capability for inspecting composite material which is the main material used in the construction of wind turbine blades. Shearography is a ramification of holography interferometry and is more efficient to be used as a non-destructive testing (NDT) technique owing to its improved robustness and sensitivity to surface displacement. Robotic climbers, on the other hand, have recently drawn significant interest in NDT applications to replace human inspectors in extreme conditions. Thus, this thesis presents investigations into the development of a robotic NDT method using digital shearography for on-site inspection of wind turbine blades. The development of the shearography unit with correlation fringe pattern acquisition and the integration of this unit with the robotic climber adhering to wind turbine blades using vacuum generators are described in this thesis. The successful conduction of the indoor and outdoor trails for the integrated system verifies that shearography holds the ability to be used as an NDT tool for on-site wind turbine blade inspection, and that the climbing robot is able to access most areas of a wind turbine blade and stabilise itself to remove the impact on the shearography of the high frequencies from the climber’s vacuum motor and the low frequencies from the blade swing. Temporal phase shift shearography, and the fast phase map acquisition methods with less steps are evaluated in the thesis. Experiments are performed in lab with phase maps obtained using different algorithms. Apart from the conventional 4 steps and 3 steps phase shift algorithms, the modified 4+1 and 3+1 temporal phase shifting algorithms are developed for more suitability of semi-dynamic inspection by firstly calculating the correlation fringes and followed by the phase map calculations. The results of these modified methods are compared with the conventional 4 steps and 3 steps methods and are shown with equal qualities. Moreover, the reduced steps of phase shifting, i.e., 2+1 phase shifting methods are conducted for semi-dynamic phase map acquisition. It is found that the temporal phase shifting methods are not suitable for dynamic wind turbine blade inspection, however, the fast semi-dynamic temporal phase shift algorithms are able to produce phase maps with lower clarity. Pixelated spatial phase shift shearography is developed to remedy the limitation of temporal phase shift techniques. It adopts a micro-polarization sensor in the complementary metal oxide semiconductor (CMOS) camera, two linear polarizers, and a quarter waveplate as a new arrangement of optical path to replace the piezoelectric transducer stepper as the phase stepper. Three algorithms are introduced based on this novel developed system. Additionally, the site of view is enlarged for upgrading of the system. The development of the pixelated spatial phase shift shearography has mitigated the static processing limitation on temporal phase shift shearography, which caters for the demands of on-site NDT operation. At the same time, it remedies the current real-time shearography system which is not able to produce phase distributions for further quantitative analysis. The new developed pixelated spatial phase shift shearography system is thus more suitable for WTB on board inspection than both conventional and less-steps temporal phase shift shearography system. The field of view enlargement optimisation in the new developed spatial phase shift system indirectly reduces the distance for the inspection process and meanwhile enlarges the site of view, which consequently reduces the weight and structural complexity of the robotic-shearography integration system. The research addresses and resolves the difficulty of on-board wind turbine blade inspection with a novel robotic NDT approach using digital shearography. The approach is significant for real world industrial applications. Moreover, through the temporal and spatial phase shift evaluation, the research proves the feasibility of dynamically obtaining phase maps by the shearography system for further quantitative analysis without using temporal phase shift devices

The development of an autonomous robotic inspection system to detect and characterise rolling contact fatigue cracks in railway track

At present, high speed dual purpose rail/road vehicles employing fixed non-destructive testing (NDT) sensors are used to inspect rails. Due to the uncertainties in characterisation of the defects when they are detected at high speed, manual re-visiting of the defects by expert operators is required before any decision regarding track maintenance is made. This research has been driven by a desire from the rail industry for a robotic system performing faster than human operators and being capable to both detect and characterise rolling contact fatigue (RCF) cracks in rails with the aim of automating the existing manual inspection and enhancing its accuracy and reliability. This thesis combines expert systems technologies with robotic NDT to fulfil this aspiration. A great deal of effort has been spent to develop a robotic inspection trolley which can automatically detect and characterise the RCF cracks in rails using an alternating current field measurement (ACFM) sensor. It uses a rule based expert system (RBES) proposed to control the robotic trolley and more importantly process ACFM data for both detecting and sizing defects. The developed system can detect the possible presence of defects in railway tracks at high speed pass (5-20 km/h) and can automatically return to an identified defect location to perform a slower and more detailed scan (up to 20 mm/s) across a rail section to determine the size, depth and number of cracks present in that section