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Haptic Virtual Reality Assembly Moving Towards Real Engineering Applications

Advancesnerate designs(Ritchie) The authors feel that the benefits of VR in thesminated to the wider industrialnity and with thecheaper pcider appreciation of the capabilities of this type ofurage companies to adopt VR solutions for some of their productrocesses It is envisaged that the notion of unobtrusive logging can similarly benis chapter will describe applications of haptics in assembly demonstrating hologging can lead to the analysis of design and manufacturing tasks at a level of detail nota haptic feedback device(Phantom, Sensable Technologies, 1993)and a 3D system tonalyse and compare this technology against red user performance Througdetailed logging of tasksLic vr environment the studerstanding how virtual tasks can be mapped onto their real world equivwing how haptic process plansbe generated The chapter also investigatesgame-based approaches, the working environment can be made morTwith a viewthe authors feel that theproduct design and manufacturing should evolve in order to enable the industrialof this technology in the futureBackgroundarious researchers have investigated sense of presence measurements simulation validitypen an effort to assess the effectiveness of force-feedback vRimportant aspect of assembly

Tight tolerances between both objects involinsertion andand force control Ho and Boothroyd (1979)studied the intraposition of a peg into a holend themposition of a part with a hole onto a peg Their objective was to elicit chamferdesigns that will minimise insertion times and, hence, overall assembly times, Rosenburginsertion task through alink with force-feedback Five different haptic overlaysere tested which included virtual surfaces, virtual damping fields, virtual snap-to planesnd snap-to-lines The results indicated thatperfoparing telemanipulation to direct in-petion howeo thepresencbe restored clnatural in-person capabilities The use of 3D haptic overlays was alsoin the standard peg-insertion taskntechopen

aptic virtual reality assembly-Moving towards Real Engineering ApplicationsRed identifiesasping, holding, translation,bly operations Note: The shadowed cylinder in the middle shows the originTo visualize the data stream, large spheres are used to signify the start of an evend displacements Velocity changes are indicated by the separation of theie sparsely spaced spheres equate to higher velocity

The line joining all spheres is6 Experimental Rssembly procedure in a haptic virtual environment This experimentre challengingembly Two sets ofepared: a real world set up and a virtual reality set up where the participant is given theaptic feedback, and so athe relatact of thementioned previously, the participants were not informed about chamfers being on thetotal of 34 participants were recruited for the virtual and real world peg-in-hole task Eachsubject was randallocated to two experiments listed in Table 1 and the results chartedFigntechopen

AdvancesIoBVirtual and real world Peg- in-Hole task completion time (rCT) comparison TCT fortopChamfered Peg /Chamfered hole(CPCH): The resultate the effects of augmentevirtual environments through the use of force cues during anbly task Compstereo viewing show a gain of approximately 16 seconds on the overall task completime (TCT) Where stereo is present but not collision detection, it was observed thatparticipants took longer to al2

gn and insert the peg into the hole This is reflected in theFlat Peg Flat Hole(FPFH): This experiment also presents a similar trend to the CPCHexperiment Though less pronounced comparisons against stereo viewing again showTCTending the majority of time aligning the peg in the hole Since no force cuesn contact with the sides of thethe subjects relied heavilfactor in reducing TCT It appears that perception ofd shape, in addition to visualstimuli on haptic perception, has exposed the powerent that manualipulation of objects in virtualmentsmproves with haptic feed backntechopen

aptic virtual reality assembly-Moving towards Real Engineering Applicationsfects: In order to consider the haptic equipments actual operational influence ona manner similar to that detected by Bashir et al(2004), it was decided tots inherent damping during operation, The architecture used formeant that to apphenomena such as gravity, restitutionvided via a physics engine, which added an operationallay into the system This adds further load to the system, and in the current develof HAMMS, genedamped effectvirtual shapes; the hapticrespoTaking thseries of displacement trials were carried out to establish a damping metric( Fig 840mDisplacementFig, 8 Peg displacement test to determine haptic motion dampingtotal of 30xecuted and the average taken The procedure involvespicking up the peg, bringing it forward and placing it on a pedestal The objects are resetautomatically to their origins after each placement

The movements were carried out asquickly as possible Each cursor path was recorded by logging cursor position and systemtime whenevertic device button med by theg9 presents the results after the effects of haptic damping (approximately 2 seconds) werefrom the original TCT while the new figurworld experiment times, there is close correlation to real world assemblyThisrts the findingGiously who measured timesughly double that in the real world The results also show that the Haeusler factor)-57% chamfered peg/tes to 61% in the hapticdomain and 78% in the realprovememoryanagement anefficient rigid body dynamic algorithms could potentially improventechopen

AdvancesFig 9 Effect of virtual environment damping on task completion time (TCT) TCT for eachexperiment is indicated at the top of eachThe62 Phyical effects of haptic VR interfaceof touchhaptic modality is a correlation of tactile and kinesthetsers grasp to be translated into free motieto be calculated and returned to the user Arkspace and extensibility (Eberle et aIn an effort toe interfaces, particularly for tasks involving explorationestigate userswithin virtual environments can exhibit parallax issues whenexploring virtual geometric spaces although theyd have easily understood a similareal world (Baker et al

, 1993; Robinson et al, 2007) Researchotor coordination suggests why this effect might beple, physically walking through a complexallson to keep tracktheir position and where other key locations are with respect to their own position withinhat environment (Brooks, 1992) Similarly being able to physically touch and manipulateakes its shape and structurecontrast, haptic and kinaesthetic sensations are intrinsically three-dimensional Thusstudying how mechanical-VR interfaces can support hiexterity, and hapticwhile providing quantitative 3D precision becomes moreThehe sense of motionipulation and thebility of uto interactnically with computational artefacts via haptic VRntechopen

aptic virtual reality assembly-Moving towards Real Engineering ApplicationsFig, 10 shows thetactile feed back and how it has influenced the users intentrepresented by a series of red spheres Blue sphindicatethat the usethe shape ( touching or finding a picking location), Greenspheres indicate that theteraction with virtual objectshe peg as it passes through the hentrol lines (red spheres) Hhen force cuesthe peg through the hole, as shown in Fig 10(c) and (d) The closethis as the peg enters the hole Note also how the user has gained confidenceabout the environment (or workspace)when tactile information is available Compared to theclosely spaced red control spheres in Fig

10(b), those shown in Fig 10(c)and (d) are wellseparated, indicating that the user's motion and confidence has improve0 Peg-in-hole motion chronocyclegraphb, c and d show four successive pickand place motionshas learnt to appreciatThe effects ofvision can clearly be observed in Fig 10(d) The start (pick)event andas indicated by copickingand direction of motion With stereovision the learning process is fast tracked, as there isbetter depth perception, reducing the guesswork during pickingntechopen

Advances63 Haptic influence on motor controand mhearing, chemical(taste, smell)nd vestibular (motion and position of head) VR by and large focuses on providing visualstimuli to the user whilst trying to avoid conflict with vestibular sensations that wouldesult in dizziness or motion sickness in extuser tactileHaptic devices are used ine feedback by providing touchthe user s experience from a kinaesthetic point of viewe rich multimedia environments that seek to provide engaging inexperIUntil relatively recently the predominant focus has been on the richehicalplaynt whilsdevelopoping peripherals in orddeher than the simple joysthe last feement controlled video games"or"Exer Games" have become a commercialconsole is worth considering in this context in that games for thiscompensate for a relative lack of graphical computing power with varied and richinto players experiences show that such an approach can facilitate an engagingthout the highest possible degree of realism(Thin et al, 2009)VR overtly impliesempt to closely mimic reality However, evendirect correspondence Thethe confines of their human body in the equivalent real world and move througla virtual environment muchfreely and easily, often at speed and defying gravitationalnd anatomical constraints, a shift in focus towards considering the nature of the usersor enhancing the VE, the user would experience something that is more intuitive andesponsive to their needs and intIs

Examples of such augmentation would includep to functionality, visualpecific details and proximity awareness through the use of sound(haptic feedback dneedconfined to tactile sensations)will inR system feels This ishat a user cannot learn to usestems and approaches and fit in to them butain widespread acceptance and adoption, it is desirable to try and fit within thea given usees Psychophysiologyment techniquesould potentially provide a way to evaluate how a user is sensing and responding to a givenelectromyograhic activity of skeletal muscles(EMG), brain activity (electroholographand eye movement tracking (electrooculography, EOG) Insight into a users arousaland or stress levels could also be gained (eg heart rate, temperature, blood pressugalvanic skin response) Such physiological signals are likely to result in patternsesponses to different situations which are characteristics of certain subject responsentechopen

aptic virtual reality assembly-Moving towards Real Engineering Applicationsa preliminary investigation was undertaken in order to assess the EMG response duringons of theth theflexed and the elbowtwere made ofactivity whilst theoniometer(Fig 11) The signals were acquired using a specialised physiological recordingtem comprising a set of optically isolated analogue to digiterters under softwkHz Dataed and analysed using digital chart recordingperformed 30als at a uniform rate The real and virtual world tasksperformed in a randomised order

A screen shot from the physiological recordingperimental setup is shown on the left The right image shows the goniometer attachedFig 11 Investigating haptic influence on motor control through biometric data logging人骨氣d RMs EMG signals from biceps and triceps musclntechopen

aptic virtual reality assembly-Moving towards Real Engineering Applicationsthe mid 1990s commercial force feedback interfaceh as the phanthichstylus, Gupta et al(1997) investigated the benefits of multimodal simulation using Vtechnology for part handling and insertion comparedpresented by Boothroyd et al(2002) Their results showed that assembly task completiontime increased in proportion to the complexity of the assembly operations requiredthose required to carryrestricted to 2D simulthe insertion operation Significantlthertedthors speculate that one of the contributortion timemeans with which to measure the performance of human motor control ofFitts derived a quantitative predictor for the movem

ent time needed for theompletion of 2D targeting peg-in-hole-type tasks

Thehaptichybrid system that uses both haptic and visual interfacemotion plg queryvirtual robot attached to the phantptic device a seqhaptic probe and virtual objects, computing reaction forces, andacle-based probabilistic roadmap methodused in conjunctiona C-Spaceto filter the haptically-generated paths and generate collisthe robott al (2001)described an experimental arrangement for coperformancehole via a 6 degree of freedom magnetic levitation haptic device and visual feedbackmanipulation strategies, Their resumenses can discriminate between very fine forces and positions; however, it wathat overall task perfoth real objects is bestf haptics lends itself naturally to tasks that req(2001)conducted experiments to investigate the benefitsfeedback for VR training of assembly tasks Three groups of participantlevels of training (virtual with haptics, virtual without haptics, and ndel biplane in realnt Their rearticipants with haptic training performed significantly better than thosely procedures witdevelopiperspeenabledntechopen

Advancesly useful for applications that provide tactiletyy Instru, gn stage However, there is little evidence ofhe vein of research here is the work by Gerovichev et al(2002)on the evaluatiand haptic feedback for training needle insertion tasks in medicineresults sed thhe addititoes, along with real-time visual feedback,Yoshikawa et al(2003)presented a methodology for observing human skill in a virtualhole task and a 2D simulation was performed The virtual space incorporated dynamics andsurface friction characteristics Results indicated that stability of the haptic systemimproved with analogue circuitry so that human skills are better represented in the virtualironment Bashir et al(2004)devea svstem tothe influence equipment andvisual and augmented feedback and how this influences taskwith a sliding motion

The effects ofand clearancelered Their results indicated 45% prolonged completion times with forceofure the effectiveness of a medical therapy regimpeg-in-hole haptic assessmenas the study of choice for quantifying upper limb skills The set-up consists of a largevirtual table with two identical cylindrical holes and a cylindrical peg that was to bepeatedly inserted by alternately moving between each of the holesPhysical properties of the peg and hole such as diameter, peg weight and height,Position, velocity and reaction forces000Hz Inconclusive results were obtained but further clinical trials are beingto investigate the usefulnesthe haptic system as aRecent researchtowards developing architectures for collaborative haptic virtualvironments (CHVEs) The Collaborative Haptic Assembly Simulator (Iglesias et al, 2006reported work that investigates assembly/disassemblycomponents in a collaborative virtual environment The system has the potential to managelarge assemblies; unfortunately, they do not appear to have stored andof movements, A review on the applof hadvancement of VR and haptics(Ferreira Mavroidis, 2006)exploratory influence and the associated sensory advantages of tactile feed backteraction with VR, the optimisation of the kinestheticdesign( Fritschi et al, 2008)ntechopen

aptic virtual reality assembly-Moving towards Real Engineering Applicationswell as the human haptic perception(Bresciani et al, 2008) However there has beeninteraction hprovide force feedback and inherit the dynamics and movements of the tool they simult whether this protasks in vR and real life based on the bio-mechanicalad to a scientifically more accurate and realistic haptiWhilof the published work on VR applications with force feedback shows thenefits of haptics, they do not discuss the automatic generation of qualitative informationderived from assembly plans(syntax or semantics)d withinulations in thevirtual environment Generally, haptics remains as a facilitator in guiding spatialplanning and in more general termanufacturing information

Extrapolating the cognitive procedrelating to assemblyinteraction willde informatibetter a products dmanufacture and assembly(DFMARf dataunderlines knowledge, experience and intent By analyzing this information optimizationsle to procedural tasks and training strategies early in the development phasewhile making users aware oftask analptic vR environments is central to this work; indeed, the apanufacturing assembly processes as well as early knowledge(Ritchie et al006) Following a successful pilot study by Lim et al(2006), while statistically inconclusive,has shown that Design for Assembly (DFA)components had an impact on taskdequacies of the test bed, for example its functionality and ease of use, andactors such as the associatedive and physiological perspective of how peoplestereo andmodes, With this in mind thethe hia the use ofassessment of virtual, virtual/haptic peg-inssembly tasks against real worlomyography (EMG)d in thending of kinaesthetic responses betweenhaptic VR and the realtasksvance the state of the art and to achievete cornhaptic based systems3 Motion chregeometries to be manufactured,sembly procedures it is useful to understand the cognitive insight of the huma oan then be plotted as a time-dependent profile describing motion together with position,ntechopen

Advances in Haptics(a) Therblig SymbolsFig 1 Gilbreth's Time and Motion Study(courtesy of Johnson Ogilvie, 1972)Therbligs are a set of symbols developed by Frank Gilbreth(Price, 1990; Johnson Ogilvy1972)during the early 20th century to study assembly motions, where each symbollows the 18 therblig units represent a set of fundamental motions required to performanual operation: Search; Find; Select; Grasp: Hold; Position; Assemble; Use; Disassembaspect; Transport loaded; Transport unloaded Pre-position for next operation; Release loadUnavoidable delay; Avoidable delay; Plan; and Rest As therbligs map onto each individualoperation task, by analysing the therblig units associated with a process, unneedeeliminated to optimise and make efficient any task For example, whennumerous'delay' therbligs associated with a particular assembly operation are evident thenthe efficiency for that specific task will have to be improvedGilbreth also devised chronocyclegraphs for motion studies(Price, 1990) The methodUsing long-exposure photography of the whole assembly process, a result(b) is obtained This result displays the path, known as the chronocyclegraph, that thasinefficient movement by the user

By letting the light source flash at a known frequency, italso help determine the velocity and acceleration of the hand movementsndeed, there is much to be gained from Gilbreths seminal work on time and motion studyHowever there is no literature thathat these have been applied in any VR and/4 Experimental methodologyclassically, one of the most extensively studied manual processesaims to quantify assemblies by analysis of theof operations required to build a component Ferequired for manual insertion of a peg into a hole for various geometriesa cylindrical peg into a round hole as its baseline time(ie 100%)ntechopen

aptic virtual reality assembly-Moving towards Real Engineering Applications981)reports a German study that estimated the relative times required toetries He estimated that the insertion of a round pegs into ahole took only 57% of the time required to complete the"nominalshan Design for assembly(DFA) The diagram shows pegsFiholes with varying fes and relative assembly times( Haeusler, 1981)DFA methodologicquantified the relative times oftasks:benchmarked against previously quantified assembly times? Thisle assembly task in this study The assembly processstates: picking, placing and motionThe peg-in-hole task requires inserting a peg into a block with a hole, Participants perforhis both as a virtual 3D task where they are provided with different combinations of visuald force cues(through a haptic device)and the real world equivalent tasks

The primary objective westigate simulator fidelityd hfeedback, andthe rele and physiological performance The peg-in-hole experimentas planned as a precursor to a more challenging assembly that involved a geared pumptaskgn for the virtual task, a binaused toindicate whether collision detection and steren was switched on(1)or off (O)Therewhich are ordered such that tests adetection(C/D)and with/ without stereovision The key featurethis experimentation was that the participants were totally unaware of any geometricaldifferences within components during this experimental programmentechopen

AdvancesTable 1 Experimental designrandomly allocated to experiSubsequently each was also randomEach experiment had an equal number of participants8virtualhaptic feedbackinto a hole using the hatth the picked object onto a stationbject to expeEach participant was asked to move a peg from its starting position to the block andEach participant was then askedplete a questionnaire after the experAnalysisthe pickup of each peg until last release, Thisprovided a task completion time (ICT)in seconds for each repetitionwere uniquely defined for each participantVideo recording for each participant was taken to give more insight into both behaviourStatistical analysis was subsequently used to investigate the null hypothesis that:"Thevariability in perfbetween task pairs would be similar4

2 Real tasked to perflual peg-in-hole insertionFour different inse1 Flat Peg/Flat hole(FPFH)-Insert flat end peg into a block with a chamferless hole2 Chamfered Peg/Flat Hole(CPFH)-Insert a peg with a 45conical chamfered end intoblock with a chamferless holeChamfered Peg/Chamfer Hole(CPCH) Insert pegnto a block with a corresponding chamfered hol4 Flat Peg/Chamfer Hole(FPCH)-Insert flat end peg into a block with a 45 conicalntechopen

aptic virtual reality assembly-Moving towards Real Engineering ApplicationsEach routine was repeated six times The setup(Fig 3)ensured that the distance betweenhe peg and hefixed (at 40mm from the centre of the peg to the centre of thethe block)and that each participant was positioned according to their comfort of reach andthe left where seplaced from its he4 details the dimensions for the block andpeg used in the virtual world and for the real world experimenthe left shows the peg and the block with its cross-sectionaltest block and pegs(diameters left to right -1485 mm, 14

48 mm and 1354 mm) are shownn the rightThe Haptresponse while performing variousdevice for inwithcopic glassesMacNaughton, 2008) for stereo viewing when required The systems' hardware andarchitecture is presented in Fig 5 and comprises the following componentsntechopen

AdvancesHaptics Interface: Sensable Technologies OpenHaptics@ Toolkit (SensablGraphics Interface: The Visualization Toolkit (VTK, 1998)is usedgraphics, image processing, and visualizationAGEIA PhysXTM (AGEIA PhysX, 2008)technologyhysics engine that includes an integrated solver for fluids, particles, cloth and rigid)Hardware(b) Architecturetime State changes within the physics environment update idCentral to HAMMS is the physics engine, whichmulations in realAs haptic rendering relies on real time collision feedback fromnportant that where possibleex hulls and/oshaused to reprethe objects in the physics environment The most important issue to address is thenchronization between the haptic and physics loops Essentially, the physics loop runs atapproximately 30-60 Hz while to create realistic sensations the haptic loop requires 1000 Hz

the changing states in the physical simulation tothe forces associated with the haptic rendering The resulting events are thenHAMMS logs data for each virtual object in the scene including devices that are used feobjnumber) Fig 6 illustrates the colour-coded therblig unitsapted by HAMMS and its association to the logged data By parsing through the loggeddata text files an assembly procedure can be automatically formulatedntechopen