A non-contact laser speckle sensor for the measurement of robotic tool speed

A non-contact speckle correlation sensor for the measurement of robotic tool speed is described that is capable of measuring the in-plane relative velocities between a robot end-effector and the workplace or other surface. The sensor performance has been assessed in the laboratory with sensor accuracies of ±0.01 mm/s over a ±70 mm/s velocity range. The effect of misalignment of the sensor on the robot was assessed for variation in both working distance and angular alignment with sensor accuracy maintained to within 0.025 mm/s (<0.04%) over a working distance variation of ±5 mm from the sensor design distance and ±0.4 mm/s (0.6%) for a misalignment of 5°. The sensor precision was found to be limited by the peak fitting accuracy used in the signal processing with peak errors of ±0.34 mm/s. Finally an example of the sensor’s application to robotic manufacturing is presented where the sensor was applied to tool speed measurement for path planning in the wire and arc additive manufacturing process using a KUKA KR150 L110/2 industrial robot

Mid-IR spectroscopic instrumentation for point-of-care diagnosis using a hollow silica waveguide gas cell

Laser spectroscopy provides the basis of instrumentation developed for the diagnosis of infectious disease, via quantification of organic biomarkers that are produced by associated bacteria. The technology is centred on a multichannel pulsed quantum cascade laser system that allows multiple lasers with different wavelengths to be used simultaneously, each selected to monitor a different diagnostic biomarker. The instrument also utilizes a hollow silica waveguide (HSW) gas cell which has a very high ratio of interaction pathlength to internal volume. This allows sensitive detection of low volume gas species from small volume biological samples. The spectroscopic performance of a range of HSW gas cells with different lengths and bore diameters has been assessed using methane as a test gas and a best-case limit of detection of 0.26 ppm was determined. The response time of this cell was measured as a 1,000 sccm flow of methane passed through it and was found to be 0.75 s. These results are compared with those obtained using a multi-pass Herriot cell. A prototype instrument has been built and approved for clinical trials for detection of lung infection in acute-care patients via analysis of ventilator breath. Demonstration of the instrument for headspace gas analysis is made by monitoring the methane emission from bovine faeces. The manufacture of a hospital-ready device for monitoring biomarkers of infection in the exhaled breath of intensive care ventilator patients is also presented

Strain development in curing epoxy resin and glass fibre/epoxy composites monitored by fibre Bragg grating sensors in birefringent optical fibre

Fibre Bragg gratings (FBGs) fabricated in linearly birefringent fibres were embedded in glass fibre/epoxy composites and in the corresponding unreinforced resin to monitor the effective transverse strain development during the cure process. The optical fibres containing the FBG sensors were aligned either normal or parallel to the reinforcement fibres in unidirectional glass fibre/epoxy prepregs. The chemical cure kinetics of the epoxy resin system used were studied using differential scanning calorimetry, in order to investigate the correlation between the strain monitoring results and the evolution of the curing reaction. A non-parametric cure kinetics model was developed and validated for this purpose. The effective transverse strain measured by the FBGs demonstrated high sensitivity to the degree of cure as a result of the densification of the resin caused by the curing reaction. The effective compressive transverse strain developed during the reaction, and thus the corresponding sensitivity to chemical changes, was higher in the case of the sensing fibre aligned normal to the reinforcement fibres than in the case of the sensor fibre parallel to the reinforcement fibres. Small but measurable sensitivity to cure induced changes was observed in the case of the unreinforced resin

Development and application of optical fibre strain and pressure sensors for in-flight measurements

Fibre optic based sensors are becoming increasingly viable as replacements for traditional flight test sensors. Here we present laboratory, wind tunnel and flight test results of fibre Bragg gratings (FBG) used to measure surface strain and an extrinsic fibre Fabry–Perot interferometric (EFFPI) sensor used to measure unsteady pressure. The calibrated full scale resolution and bandwidth of the FBG and EFFPI sensors were shown to be 0.29% at 2.5 kHz up to 600 με and 0.15% at up to 10 kHz respectively up to 400 Pa. The wind tunnel tests, completed on a 30% scale model, allowed the EFFPI sensor to be developed before incorporation with the FBG system into a Bulldog aerobatic light aircraft. The aircraft was modified and certified based on Certification Standards 23 (CS-23) and flight tested with steady and dynamic manoeuvres. Aerobatic dynamic manoeuvres were performed in flight including a spin over a g-range  −1g to  +4g and demonstrated both the FBG and the EFFPI instruments to have sufficient resolution to analyse the wing strain and fuselage unsteady pressure characteristics. The steady manoeuvres from the EFFPI sensor matched the wind tunnel data to within experimental error while comparisons of the flight test and wind tunnel EFFPI results with a Kulite pressure sensor showed significant discrepancies between the two sets of data, greater than experimental error. This issue is discussed further in the paper

Mixed methods evaluation of the impact of the COVID-19 ICU Remote-Learning Rehabilitation Course (CIRLC-rehab) for frontline health professionals during the COVID-19 pandemic in the UK

© The Authors 2021. Background: Optimising outcomes for critically ill patients with COVID-19 patients requires early interdisciplinary rehabilitation. As admission numbers soared through the pandemic, the redeployed workforce needed rapid, effective training to deliver these rehabilitation interventions. Methods: The COVID-19 ICU Remote-Learning Rehab Course (CIRLC-rehab) is a one-day interdisciplinary course developed after the success of CIRLC-acute. The aim of CIRLC-rehab was to rapidly train healthcare professionals to deliver physical, nutritional and psychological rehabilitation strategies in the ICU/acute setting. The course used blended learning with interactive tutorials delivered by shielding critical care professionals. CIRLC-rehab was evaluated through a mixed-methods approach, including questionnaires, and follow-up semi-structured interviews to evaluate perceived impact on clinical practice. Quantitative data are reported as n (%) and means (SD). Inductive descriptive thematic analysis with methodological triangulation was used to analyse the qualitative data from the questionnaires and interviews. Results: 805 candidates completed CIRLC-rehab. 627 (78.8%) completed the post-course questionnaire. 95% (n = 596) found CIRLC-rehab extremely or very useful and 96.0% (n = 602) said they were very likely to recommend the course to colleagues. Overall confidence rose from 2.78/5 to 4.14/5. The course promoted holistic and humanised care, facilitated informal networks, promoted interdisciplinary working and equipped the candidates with practical rehabilitation strategies that they implemented into clinical practice. Conclusion: This pragmatic solution to educating redeployed staff during a pandemic increased candidates’ confidence in the rehabilitation of critically ill patients. There was also evidence of modifications to clinical care utilising learning from the course that subjectively facilitated holistic and humanised rehabilitation, combined with the importance of recognising the humanity, of those working in ICU settings themselves. Whilst these data are self-reported, we believe that this work demonstrates the real-term benefits of remote, scalable and rapid educational delivery

Pseudo-heterodyne signal processing scheme for interrogation of fiber Bragg grating sensor arrays

An intensity-based interrogation technique for arrays of fiber bragg grating (FBG) sensors is reported. The technique is based upon each FBG forming one mirror of a Michelson interferometer. Source wavelength modulation is combined with an unbalanced interferometer to produce a carrier signal. Carrier frequencies are characteristic of the optical path length imbalance and hence grating position within the array. The intensity of the carrier signal is directly related to the optical power reflected from the grating and hence the strain applied to the grating. Strain resolution of ∼3μm/m is demonstrated with an ∼350μm/m sensor range. Multiplexing is demonstrated and techniques to extend the range are dis

On-line monitoring of multi-component strain development in a tufting needle using optical fibre Bragg grating sensors

Dynamic loadings induced on a tufting needle during the tufting of dry carbon fibre preform via a commercial robot-controlled tufting head were investigated in situ and in real-time using optical fibre Bragg grating (FBG) sensors bonded to the needle shaft. The sensors were configured such that the axial strain and bending moments experienced by the needle could be measured. A study of the influence of thread and thread type on the strain imparted to the needle revealed axial strain profiles which had equivalent trends but different magnitudes. The mean of the maximum axial compression strains measured during the tufting of a 4-ply quasi-isotropic carbon fibre dry preform were - 499 ± 79 με, - 463 ± 51 με and - 431 ± 59 με for a needle without thread, with metal wire and with Kevlar® thread, respectively. The needle similarly exhibited bending moments of different magnitude when the different needle feeding configurations were used

Fibre grating refractometer sensors for composite process monitoring

Optimum performance from advanced composites requires careful control of the resin matrix during cure. This is to ensure there are no cure induced voids and to minimise the build up of internal stresses. Careful control of the process is also necessary to reduce wastage. Traditional resin inspection techniques are bulk or sample oriented and thus cannot provide data about critical component parts. Optical fibre based sensors however, allow for in-situ monitoring techniques to be deployed in components without effecting their structural integrity. In this work, two fibre optic grating techniques are demonstrated as process monitoring sensors and are compared with a Fresnel refractometric method. The change in refractive index of a resin has previously been used as a means for assessing the degree of cure. The central wavelength of an attenuation band of a long period grating (LPG) was monitored during the cure of a resin. In parallel the spectral resonances of a tilted fibre Bragg grating (FBG) are also monitored. The two techniques are shown to correlate well with the Fresnel based method in both detecting the resin and monitoring the state of cure, indicating the potential of the techniques for online production monitorin

Automated manufacture of 3D reinforced aerospace composite structures

Purpose- This study is part of the FP7 project ADVITAC and focuses on exploring an innovative combination of cutting edge technologies to be implemented within automated processes for composite parts manufacturing. The objective is the design of a production route for components with tailored fibre orientation and ply lay-up, with improved damage tolerance thanks to through-the-thickness reinforcement and integrated health monitoring systems based on optical fibres technology. Design/Methodology/Approach- The proposed technologies are described in detail and their compatibility and potential for integration are discussed. A set up for on-line monitoring of infusion and curing processes of carbon/epoxy laminates preformed by dry fibre placement technology is proposed, and a preliminary study of their mechanical performance is presented. The possibility of reinforcing through-the-thickness preforms manufactured with dry slit tapes automatically laid-up and consolidated by laser heating is investigated. Findings- Improved knowledge of interaction/compatibility between the discussed technologies and scope for application. Research limitations/implications- The paper reports the technical potential and practical feasibility of the proposed integrated production process. Limited quantitative evaluations on the materials performance are provided. The analysis of the technologies involved represents the early outcome of the ongoing ADVITAC project. Practical implications- This study contributes to the identification of a new generation of composite architecture which allows production cost and weight savings while retaining the level of quality suitable for demanding structural applications, with particular relevance to the aerospace field. Originality/value- This paper investigates for the first time the practical possibility of designing a single automated process involving dry fibre placement, tufting and optical fibre sensor monitoring for the production of complex composite components