Climbing Robot for Steel Bridge Inspection: Design Challenges

Inspection of bridges often requires high risk operations such as working at heights, in confined spaces, in hazardous environments; or sites inaccessible by humans. There is significant motivation for robotic solutions which can carry out these inspection tasks. When inspection robots are deployed in real world inspection scenarios, it is inevitable that unforeseen challenges will be encountered. Since 2011, the New South Wales Roads & Maritime Services and the Centre of Excellence for Autonomous Systems at the University of Technology, Sydney, have been working together to develop an innovative climbing robot to inspect high risk locations on the Sydney Harbour Bridge. Many engineering challenges have been faced throughout the development of several prototype climbing robots, and through field trials in the archways of the Sydney Harbour Bridge. This paper will highlight some of the key challenges faced in designing a climbing robot for inspection, and then present an inchworm inspired robot which addresses many of these challenges

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

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

Development of a Chain Climbing Robot and an Automated Ultrasound Inspection System for Mooring Chain Integrity Assessment

Mooring chains used to stabilise offshore floating platforms are often subjected to harsh environmental conditions on a daily basis, i.e. high tidal waves, storms etc. Chain breakage can lead to vessel drift and serious damage such as riser rupture, production shutdown and hydrocarbon release. Therefore, integrity assessment of chain links is vital, and regular inspection is mandatory for offshore structures. Currently, structural health monitoring of chain links is conducted using either remotely operated vehicles (ROVs), which are associated with high costs, or by manual means, which increases the risk to human operators. The development of climbing robots for mooring chain applications is still in its infancy due to the operational complexity and geometrical features of the chain. This thesis presents a Cartesian legged magnetic adhesion tracked-wheel crawler robot developed for mooring chain inspection. The crawler robot presented in this study is suitable for mooring chain climbing in air and the technique can be adapted for underwater use. The proposed robot addresses straight mooring chain climbing and a misaligned scenario that is commonly evident in in-situ conditions. The robot can be used as a platform to convey equipment, i.e. tools for non-destructive testing/evaluation applications. The application of ultrasound for in-service mooring chain inspection is still in the early stages due to lack of accessibility, in-field operational complexity and the geometrical features of mooring systems. With the advancement of robotic/automated systems (i.e. chain-climbing robotic mechanisms), interest in in-situ ultrasound inspection has increased. Currently, ultrasound inspection is confined to the weld area of the chain links. However, according to recent studies on fatigue and residual stresses, ultrasound inspection of the chain crown should be further investigated. A new automated application for ultrasonic phased-array full-matrix capture is discussed in this thesis for investigation of the chain crown. The concept of the chain-climbing robot and the inspection technique are validated with laboratory-based climbing experiments and presented in this thesis