Carey, Thomas

Johnson, Thomas

Sharrad, Clint

Watson, Simon

English

The University of Manchester - Institutional Repository

The University of Manchester ResearchAnalysing Human Operators and an Automated System inSwabbing TasksLink to publication record in Manchester Research ExplorerCitation for published version (APA):Johnson, T., Watson, S., Sharrad, C., & Carey, T. (2021). Analysing Human Operators and an Automated Systemin Swabbing Tasks.Citing this paperPlease note that where the full-text provided on Manchester Research Explorer is the Author Accepted Manuscriptor Proof version this may differ from the final Published version. If citing, it is advised that you check and use thepublisher's definitive version.General rightsCopyright and moral rights for the publications made accessible in the Research Explorer are retained by theauthors and/or other copyright owners and it is a condition of accessing publications that users recognise andabide by the legal requirements associated with these rights.Takedown policyIf you believe that this document breaches copyright please refer to the University of Manchester’s TakedownProcedures [http://man.ac.uk/04Y6Bo] or contact uml.scholarlycommunications@manchester.ac.uk providingrelevant details, so we can investigate your claim.Download date:09. Jun. 2022Analysing Human Operators and an Automated System in Swabbing TasksThomas Johnson,∗ Dr. Simon Watson,∗ Dr. Clint Sharrad,∗ and Dr. Thomas Carey †∗The University of Manchester, Oxford Road, Manchester, M13 9PL, thomas.johnson-2@manchester.ac.uk.†National Nuclear Laboratory, Chadwick House, Birchwood Park, Warrington, Cheshire, WA3 6AE.INTRODUCTIONIn order to safely operate in radioactive environments,routine monitoring and characterisation is required to assessphysical, chemical and radiological hazards. Robotic and au-tonomous systems are increasingly being used for monitoringand characterisation [1], offering increased safety, reductionsin operational costs and increased time-efficiency. One taskwhich could benefit from the use of autonomous systems couldbe sample retrieval through swabbing. This task is often partof characterisation strategies, and some attempts have alreadybeen made to use robots in this area [2].Robotic systems may offer increased swabbing perfor-mance when compared to human operators. The retrieval ofsamples is not perfectly repeatable [3] and so imposes a fun-damental limitation on the information that can be obtainedthrough swab sampling. As robots offer greater repeatabil-ity than humans, using them may facilitate the reduction ofsampling error associated with swabbing. In order to aid thedevelopment of these systems, there is a need to develop agreater understanding of the different factors which effectswabbing efficacy and repeatability.This paper provides a comparison of a human operator(the primary author) and a force-controlled swabbing systemin the execution of a single-pass swab test. Swabbing forceand mass removal data are presented.Understanding the effect of swabbing inputs (such as forceand swab speed) on pick-up factor will aid the developmentof automated swabbing systems which will provide greaterrepeatability in the swabbing process. The tests presented arecrucial in identifying the variables in swabbing input whichhave the largest effect on contaminant removal. While thispaper does not quantify the effects of these individual variables,a number of key variables are highlighted in this paper.METHODOLOGYTo ascertain variables which affect swabbing efficacy andrepeatability, a single-pass swab test was conducted ten timesfor a human operator and a force-controlled swabbing system.A diagram of the swabbing area is shown in Figure 1.The human operator aimed to produce even force-inputthrough the swabbing motion, maintaining a constant speedand aiming to swab the same area each time. It was notpossible to actively control these factors while conductingthese tests.The force-controlled swabbing system used in this paper,first presented in [4], is shown in Figure 2. The system in-cludes a spring-loaded swabbing pad that is compressed toa desired length by the linear actuator. The system providesmovement along the swabbing axis by moving the belt-drivenstage. The swabbing speed for each test with this system was18 cm8.5 cmSwabbing Bed8.5 cm5.5 cm2.75 cmArea swabbedFig. 1: A diagram of the swabbing area for these single-passtests.controlled so that each test would last 10 s.Linear ActuatorSpring-Loaded Swabbing PadBelt-Driven StageSwabbingPaperSwabbing BedFig. 2: The force-controlled swabbing system.Force data is collected using a linearised capacitive forcesensor (SingleTact CS8-100N). The position of these sensorsbeneath the swab was not fixed for these experiments. Pick-upfactors were determined by measuring masses using a massbalance (OHAUS Adventurer AX-224). Whatman 41 filterpapers (Ashless, 55mm circles) are used in swabbing exper-iments. The simulated contaminant for these experiments issand (50-70 mesh particle size, Sigma-Aldrich 274739).Swabbing forces were collected during experiments usingthe capacitive force sensors, with swabs being weighed beforeand after swabbing to determine pick-up rates. For all of theseexperiments, sand was deposited loosely on the surface andthen shook to homogenise the spatial distribution.RESULTS AND ANALYSISThe mass pick-up data, shown in Figure 3, demonstratesthat the force-controlled swabbing system provided muchgreater repeatability in these experiments. While the hu-man operator achieved a standard deviation of σ = 13.1 %,the force-controlled swabbing system achieved a much lowervalue of σ = 3.7 %. These results are consistent with previ-ous work [4].Human Force-Controlled51015202530354045Pick-Up Factor (%)n=10Fig. 3: A comparison of the pick-up factors achieved throughhuman and force-controlled swabbing.The force sensor data collected can be analysed alongsidethis pick-up data to provide some insight on to the importantvariables to control during swabbing. Table I shows a selectionof metrics collected in these experiments.The automated swabbing system offers much greater re-peatability in swab time (and consequently swab speed) whichmay be a contributor to the greater performance in swabbingtests. Aside from this metric, the values in Table I do notclearly demonstrate a large difference in performance.TABLE I: Performance metrics from swabbing experiments.Human Swabbing SystemMean Swabbing Force (N) 24.2 29.3σF (N) 3.5 4.3Mean Swab Time (s) 9.5 10.0σT (s) 2.3 0.0Pick-Up Factor (%) 23.0 32.4σPUF (%) 13.1 3.7Surprisingly the standard deviation in swabbing force forthe human operator was lower than the value for the swab-bing system. This seemingly counter-intuitive result is betterexplained with the information from Figure 4.Figure 4 shows force measurements (taken with f =10 Hz) from the middle 5 s of the intended 10s swabbing time.Aside from one large spike in force measurement (caused byan item accidentally being dropped on the desk near to theexperiment) the force measurements in Figure 4a give a moreconsistent force level through swabbing than in Figure 4b.Figure 4 shows that the increased deviation in swabbing force0 5 10 15 20 25 30 35 40 45 50Time (x0.1s)1520253035404550Force (N)(a) Force-controlled swabbing0 5 10 15 20 25 30 35 40 45 50Time (x0.1s)1520253035404550Force (N)(b) Human swabbingFig. 4: Force profiles during the middle 5s of swabbing.for the autonomous system is in fact due to the wider rangeof force measurements across all of the tests. This is thoughtto be due to inconsistencies in the position of the force sensorunder the swabbing pad.Figure 4 highlights differences between automated swab-bing and the human operator as well as raising issues that mustbe addressed in future work:1. The automated swabbing system provided more consis-tent swabbing force in individual tests, though there wasa large range of forces across different tests. It is yetto be determined whether this is a true reflection of thesystem behaviour or whether this was caused by the forcesensors.2. The force application measurements were more similarthan expected. If these results are a true reflection ofthe real swabbing inputs, then the force input duringswabbing may be less important than assumed [5, 6].CONCLUSIONS AND FURTHER WORKThe results presented demonstrate the advantages of usingforce-controlled systems for swabbing. Automated systems,such as the one used in these experiments, offer less variance inswabbing time and provide consistent force application. Thishas a clear positive impact on the removal of contamination,and it is demonstrated here that swabbing systems can providemuch less variance in the removal of contamination. Thestandard deviation in contaminant mass removal was just σ =3.7 % for the swabbing system, while the human operatorcould only achieve σ = 13.1 %.Though it is clear that automated swabbing systems canoffer more reliable contamination removal, the reasons for thisare not entirely known. Existing literature has long thoughtthat variable swabbing forces have a negative impact on the re-peatability of pick-up factors [7, 8, 9, 10], however the resultsin this paper give no strong indication that this is the case.The clearest differences between the swabbing of a hu-man operator and the swabbing system are the differences inswabbing time and a difference in the way force is applied tothe swab. While data from more operators are required beforemaking definitive statements, it seems that human operatorsstruggle to maintain constant swabbing speed and this maybe a reason for the decreased repeatability of pick-up factor.It is noteworthy that the way force was applied to the swabin these experiments was different for the different systems.The human applied force only across the three fingers usedto hold the swab, and this placement was not possible to bemade consistent across trials. The swabbing system was ableto apply force evenly across the whole swab and this may havehad a positive impact on swabbing efficacy.It is necessary for future work to determine which swab-bing input factors are most important during swabbing, andfor work to quantify the impact of these factors.ACKNOWLEDGMENTSThis work was funded and supported by UK Researchand Innovation and the Nuclear Decommissioning Authority.REFERENCES1. I. TSITSIMPELIS, C. J. TAYLOR, B. LENNOX, and M. J.JOYCE, “A review of ground-based robotic systems forthe characterization of nuclear environments,” Progressin Nuclear Energy, 111, May 2018, 109–124 (2019).2. Y. YUGUCHI, “Remote Control Technology used inthe Fukusima Daiichi Nuclear Power Plant (Toyota),” in“Waste Management Symposium 2021,” Phoenix, AZ(2021).3. C. P. LICHTENWALNER, “Evaluation of wipe samplingprocedures and elemental surface contamination,” Ameri-can Industrial Hygiene Association Journal, 53, 10, 657–659 (1992).4. T. JOHNSON, C. SHARRAD, S. WATSON, andT. CAREY, “Investigating the Effect of Force Input onthe Pick-Up Factor of Loose Contamination - 21093,” in“Waste Management Symposium,” (2021).5. D. CRISTINI, B. D. SOUZA, and R. VICENTE, “WipeSampling - Review of the Literature,” in “2011 Inter-national Nuclear Atlantic Conference,” Belo Horizonte(2011), pp. 24–28.6. C. CHAVALITNITIKUL and L. LEVIN, “A LaboratoryEvaluation of Wipe Testing Based on Lead Oxide SurfaceContamination,” American Industrial Hygiene Associa-tion Journal, 45, 5, 311–317 (1984).7. R. MITCHELL and B. EUTSLER, “A Study of Beryl-lium Surface Contamination,” in “Surface Contamination,”Tennesse (1964).8. G. ROYSTER and B. FISH, “Techniques for Assess-ing Removable Surface Contamination,” Tech. rep., OakRidge National Lab, Tenn. (1965).9. W. SAXBY and J. HOLE, “Practical Aspects of SurfaceContamination at AWRE,” in “Surface Contamination,”(1964).10. J. PRINCE and C. WANG, “A Method for EvaluatingSurface Contamination of Soft Beta Emitters,” in “SurfaceContamination,” (1968), pp. 179–183.

Analysing Human Operators and an Automated System in Swabbing Tasks

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Analysing Human Operators and an Automated System in Swabbing Tasks

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