Vibration actuator capable of movement on magnetic substance based on new motion principle

In every country, the construction of large steel bridges, such as cable-stayed bridges, is carried out actively, and the number of bridges has been progressively increasing. In the case of large steel bridges, inspections must be carried out every five years. Because frequent inspections of such bridges are required, working robots capable of performing inspections in difficult environments would be very useful. This paper proposes a vibration actuator with a very simple structure capable of movement on a magnetic substance via the inertial force of a mass–spring model. Through theoretical analysis using the energy method, it was determined that the vibration actuator is propelled by the difference between the frictional forces acting during the forward and backward motions of the actuator. The experimental and analytical results were compared, verifying the validity of the novel motion principle. Additionally, based on the asymmetric magnetic field that arises when a copper wire is asymmetrically wound around the iron core of an electromagnet, a method of increasing the magnetic field strength at one pole of the electromagnet is newly proposed. By attaching an iron plate to the iron core of the electromagnet, the effects of the resulting asymmetric magnetic field of the electromagnet on the actuator motion were examined. The experimental results indicate that the actuator is able to climb upward while pulling a load mass of 110 g. The maximum efficiency of the actuator was 20.5 % for an actuator pulling its own weight. The efficiency of the actuator with the attached iron plate was considerably greater than that without the iron plate

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