A noncontact ultrasonic platform for structural inspection

Miniature robotic vehicles are receiving increasing attention for use in nondestructive testing (NDE) due to their attractiveness in terms of cost, safety, and their accessibility to areas where manual inspection is not practical. Conventional ultrasonic inspection requires the provision of a suitable coupling liquid between the probe and the structure under test. This necessitates either an on board reservoir or umbilical providing a constant flow of coupling fluid, neither of which are practical for a fleet of miniature robotic inspection vehicles. Air-coupled ultrasound offers the possibility of couplant-free ultrasonic inspection. This paper describes the sensing methodology, hardware platform and algorithms used to integrate an air-coupled ultrasonic inspection payload into a miniature robotic vehicle platform. The work takes account of the robot's inherent positional uncertainty when constructing an image of the test specimen from aggregated sensor measurements. This paper concludes with the results of an automatic inspection of a aluminium sample

Miniature mobile sensor platforms for condition monitoring of structures

In this paper, a wireless, multisensor inspection system for nondestructive evaluation (NDE) of materials is described. The sensor configuration enables two inspection modes-magnetic (flux leakage and eddy current) and noncontact ultrasound. Each is designed to function in a complementary manner, maximizing the potential for detection of both surface and internal defects. Particular emphasis is placed on the generic architecture of a novel, intelligent sensor platform, and its positioning on the structure under test. The sensor units are capable of wireless communication with a remote host computer, which controls manipulation and data interpretation. Results are presented in the form of automatic scans with different NDE sensors in a series of experiments on thin plate structures. To highlight the advantage of utilizing multiple inspection modalities, data fusion approaches are employed to combine data collected by complementary sensor systems. Fusion of data is shown to demonstrate the potential for improved inspection reliability

Simulation of ultrasonic lamb wave generation, propagation and detection for an air coupled robotic scanner

A computer simulator, to facilitate the design and assessment of a reconfigurable, air-coupled ultrasonic scanner is described and evaluated. The specific scanning system comprises a team of remote sensing agents, in the form of miniature robotic platforms that can reposition non-contact Lamb wave transducers over a plate type of structure, for the purpose of non-destructive evaluation (NDE). The overall objective is to implement reconfigurable array scanning, where transmission and reception are facilitated by different sensing agents which can be organised in a variety of pulse-echo and pitch-catch configurations, with guided waves used to generate data in the form of 2-D and 3-D images. The ability to reconfigure the scanner adaptively requires an understanding of the ultrasonic wave generation, its propagation and interaction with potential defects and boundaries. Transducer behaviour has been simulated using a linear systems approximation, with wave propagation in the structure modelled using the local interaction simulation approach (LISA). Integration of the linear systems and LISA approaches are validated for use in Lamb wave scanning by comparison with both analytic techniques and more computationally intensive commercial finite element/difference codes. Starting with fundamental dispersion data, the paper goes on to describe the simulation of wave propagation and the subsequent interaction with artificial defects and plate boundaries, before presenting a theoretical image obtained from a team of sensing agents based on the current generation of sensors and instrumentation

Safety In Service Operations: A Frontline Perspective

This paper identifies service safety as separate dimension of quality and considers the need to view safety from the frontline workers perspective. Stewarts (2003) 3 T framework is used to categorize safety training elements by task, treatment and tangibles. Results from a survey of public transit bus drivers are presented. Results show that the questions categorized as treatment and tangibles were significant predictors of perceived safety

Practical constraints on real time Bayesian filtering for NDE applications

An experimental evaluation of Bayesian positional filtering algorithms applied to mobile robots for Non-Destructive Evaluation is presented using multiple positional sensing data – a real time, on-robot implementation of an Extended Kalman and Particle filter was used to control a robot performing representative raster scanning of a sample. Both absolute and relative positioning were employed – the absolute being an indoor acoustic GPS system that required careful calibration. The performance of the tracking algorithms are compared in terms of computational cost and the accuracy of trajectory estimates. It is demonstrated that for real time NDE scanning, the Extended Kalman Filter is a more sensible choice given the high computational overhead for the Particle filter

Quantifying and improving laser range data when scanning industrial materials

This paper presents the procedure and results of a performance study of a miniature laser range scanner, along with a novel error correction calibration. Critically, the study investigates the accuracy and performance of the ranger sensor when scanning large industrial materials over a range of distances. Additionally, the study investigated the effects of small orientation angle changes of the scanner, in a similar manner to which it would experience when being deployed on a mobile robotic platform. A detailed process of error measurement and visualisation was undertaken on a number of parameters, not limited to traditional range data but also received intensity and amplifier gain. This work highlights that significant range distance errors are introduced when optically laser scanning common industrial materials, such as aluminum and stainless steel. The specular reflective nature of some materials results in large deviation in range data from the true value, with mean RMSE errors as high as 100.12 mm recorded. The correction algorithm was shown to reduce the RMSE error associated with range estimation on a planar aluminium surface from 6.48% to 1.39% of the true distance range

Robotic ultrasonic testing of AGR fuel cladding

The purpose of the presented work was to undertake experimental trials to demonstrate the potential capabilities of an in-situ robotic ultrasonic scanning technique for measuring and monitoring loss of the cladding wall thickness in fuel pins of Advanced Gas-cooled Reactors (AGR) using inactive (i.e. non-radioactive) samples. AGR fuel pins are stainless steel cylindrical ribbed pipes of length circa of 1000 mm, inner diameter of the rod being circa 15 mm and wall thickness of circa 300µm. Spent AGR fuel pins are stored in a water pond and thus may be prone to corrosion and stresscorrosion cracking under adverse conditions. An ultrasonic immersion transducer with central frequency of 25MHz was used to measure wall thickness of the AGR fuel cladding using a frequency domain technique. Cylindrical ultrasonic scan of the samples 2 was performed using industrial robotic arm KUKA KR 5 arc HW. Also, very short (2.5mm long) and shallow (100µm in depth) crack-like defects were detected using time-domain technique

Suppressor of cytokine signaling 2 (SOCS2) deletion protects bone health of mice with DSS induced inflammatory bowel disease.

Individuals with inflammatory bowel disease (IBD) often present with poor bone health. The development of targeted therapies for this bone loss requires a fuller understanding of the underlying cellular mechanisms. Although bone loss in IBD is multifactorial the altered sensitivity and secretion of growth hormone (GH) and insulin-like growth factor-1 (IGF-1) in IBD is understood to be a critical contributing mechanism. The expression of suppressor of cytokine signaling 2 (SOCS2), a well-established negative regulator of GH signaling, is stimulated by pro-inflammatory cytokines. Therefore, it is likely that SOCS2 expression represents a critical mediator through which pro-inflammatory cytokines inhibit GH/IGF-1 signaling and decrease bone quality in IBD. Utilising the DSS model of colitis we have revealed that endogenously elevated GH function in the Socs2−/− mouse protects the skeleton from osteopenia. Micro-computed tomography assessment of DSS treated wild-type mice revealed a worsened trabecular architecture compared to control mice. Specifically, DSS treated WT mice had significantly decreased bone volume (BV/TV) (41%; p<0.05), trabecular thickness (16%; p<0.05), trabecular number (30%; p<0.05), and a resulting increase in trabecular separation (19%; <0.05). In comparison, the trabecular bone of Socs2 deficient mice was partially protected from the adverse effects of DSS. The reduction in a number of parameters including BV/TV (21%; p<0.05) was less, and no changes were observed in trabecular thickness or separation. This protected phenotype was unlikely to be a consequence of improved mucosal health in the DSS treated Socs2−/− mice but rather a result of unregulated GH signaling directly on bone. These studies indicate that the absence of SOCS2 is protective against bone loss typical of IBD. This study also provides an improved understanding of the relative effects of GH/IGF-1 on bone health in experimental colitis, information that is essential before these drugs are explored as bone protective agents in children and adults with IBD