An Interactive Haptic Guidance System for Intuitive Programming


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An Interactive Haptic Guidance System for Intuitive Programming CNC Machine Tool

Kamil Stateczny and Karol Mia˛dlicki *

Department of Mechanical Engineering and Mechatronics, West Pomeranian University of Technology, Szczecin, al. Piastów 19, 70-310 Szczecin, Poland; [email protected] * Correspondence: [email protected]

Abstract: The human-machine interfaces in modern CNC machine tools are not very intuitive and still based on archaic input systems, i.e., switches, handwheels, and buttons. This type of solution has two major drawbacks. The pushed button activates the movement only in one direction and is insensitive to the amount of the force exerted by the operator, which makes it difficult to move the machine axes at variable speeds. The paper proposes a novel and intuitive system of manual programming of a CNC machine tool based on a control lever with strain-gauge sensors. The presented idea of manual programming is aimed at eliminating the need to create a machining program and at making it possible to move the machine intuitively, eliminating mistakes in selecting directions and speeds. The article describes the concept of the system and the principle of operation of the control levers with force sensors. The final part of the work presents the experimental validation of the proposed system and a functionality comparison with the traditional CNC control.

Citation: Stateczny, K.; Mia˛dlicki, K. An Interactive Haptic Guidance System for Intuitive Programming CNC Machine Tool. Sensors 2021, 21, 3860. https://doi.org/10.3390/ s21113860
Academic Editor: Maria Gabriella Xibilia
Received: 15 April 2021 Accepted: 1 June 2021 Published: 3 June 2021
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

Keywords: CNC control; machining assistance; operator; HMI; force control; haptic devices; programming by demonstration; force sensor; force measurements
1. Introduction
CNC designers are at a crossroad, with increasing demands for faster and flawless machining processes without increasing the skills requirements for CNC operators. Introducing too advanced and complex structures with a high level of abstraction in the CNC programming language, such as in modern, object-oriented programming languages, can cause many difficulties for the average CNC machine tool operator. There is therefore a tendency for the development of programming languages for CNC machine tools to simplify programming languages or the whole programming process for the CNC machine tool. Different types of workpiece visualizations or graphical simulations of the machining program are introduced to create easier more flexible environments. Control systems are connected to a computer network to transfer machining programs and exchange data with databases. These databases can store geometric parameters of tools located in the tool room and other data used in the technological machining process.
The complexity of solutions used in CNC machine tools is still growing new methods of surface quality improvement [1] and topographic inspection [2], and continuous miniaturization that require an accuracy range in micrometers [3]. Machining tools are also constantly being developed and extended with modern, complex systems, such as compensation of thermal errors of a ball-screw-driven [4] or cutting stability [5,6]. In addition, more advanced solutions have been proposed by Gomez-Acedo et al. [7]. The authors proposed a special method designed for the assessment of repeatability and accuracy of large machine tools, along with results for a large gantry-type milling machine, recorded in a medium-term period. For this purpose, they recorded temperatures, and a metrological frame was used along with inductive sensors in the tool tip, performing repetitive measurements. Laser solutions are also used to compensate for thermal errors in machines. In [8], the authors presented a new methodology to measure thermal distortion in large machine

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tools based on interferometers. The proposed method used a single tracking interferometer that can be used to measure thermal distortion of machines with large work volumes while maintaining a low enough measurement cadence and uncertainty. Vision systems are also developing very quickly. They are applicable for vision-based 3D scanning system for the positioning of the workpiece [9], and systems based on models for stability prediction [10] or used in advanced applications [11]. Various types of contextual software for CNC machine tools and software used to generate programs based on three-dimensional (3D) models have been introduced, which unfortunately require additional skills in modeling 3D objects and involve the need to purchase additional software. Despite the dynamic development of graphical interface systems [12], overlays for generating G-code and interactive assistants [13–15] in CNC systems, the issue of intuitive programming of a CNC machine tool is still not solved. The way CNC machines are controlled has not changed for years and is based on buttons/wheels or writing/generating G-code. Despite all of these systems, errors involved in the assembly machine can still occur. In [16], the authors proposed a methodology for the assessment of the geometrical accuracy of a multiaxis machine.
The inspiration for designing a manual programming system for a CNC machine was developed from programming industrial manipulators [17,18]. The method uses a manual programming tool to move the tip of a manipulator and then gives commands to save individual positions [19]. As a result, it is possible to quickly generate a trajectory between the saved individual points. Based on this outcome, an innovative method of programming a CNC machine tool has been developed and software has been prepared to simulate the programming process in virtual reality [20–23]. The process of programming manipulators through their manual operation is supported by various types of systems. In such a solution, the operator can intuitively grasp the manipulation system located at the end of the robot arm and move the robot arm by moving the hand [24,25]. This work was further used for manipulator control in milling processes using teach-in methods [26,27] and in the foundry industry to process small- and medium-sized series of castings. Unfortunately, in the case of CNC machine tools there are no such simple and intuitive solutions on the market.
The development of a solution appropriate for machining systems is complicated by the requirement for acquiring and maintaining a desired cutting speed to achieve smooth motion of not only one but several axes of the machine tool at the same time. When operators handle the CNC machine tool they must operate the movement of several axes at the same time. The system for manual handling of the CNC machine tool body parts should also be intuitive, like moving objects in real world—many realistic manual control tasks require human operators to control multiple degrees of freedom simultaneously [28]. As shown in research, humans perform better when controlling multiple axes simultaneously than when they control each axis independently [29,30]. Additionally, in independent axis control (as in buttons, simple joysticks or pads) a focus on one axis or a consistent prioritization has been observed, an effect referred to as axis asymmetry [31]. The sensation of force when moving objects is important for intuitive control [32].
In the literature there are efforts in which a bulk of work is centered mainly upon haptic technology [33,34] or force-feedback [35,36]. In a haptic system with force feedback, only virtual machine tools are controlled, and not physical CNC machines [37]. In [38], results were presented for a programming by demonstration (PbD) interface in augmented reality for motion planning in a three-axis CNC machine. The interface assists a human planner to effectively determine dispenser motion in a planning task. Haptic solutions are also used for the training of machine operators and path planners in virtual polishing and grinding machines. A tool-workpiece contact force model was developed to simulate resultant haptic force feedback [39]. Likewise, there are also several similar solutions in the refurbished conventional machining industry. A simplified version of point saving solutions is used in refurbished conventional machine tools additionally equipped with simple CNC systems. These systems enable manual operation, where the operator controls the machine tool with the aid of handwheels, performing the machining in real time, and

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in the teach-in mode. While in teach-in mode, the operations performed by the operator during the machining of the first workpiece are recorded. It is possible to repeat the operations and thus perform automatic machining of subsequent parts. The operatormachine interfaces in such solutions are not very intuitive as they are still based on archaic input systems, i.e., handwheels and buttons. Despite all of these achievements in the field, there is no solution for modern CNC machine tools.
In this study we propose an interactive haptic guidance system for the intuitive programming of CNC machine tools. We consider the following to be our key contributions:
• We introduce the intuitive haptic method of controlling CNC machining tools based on the natural moving of objects for simple machining operations. The proposed programming approach allows a machine tool to be programmed without writing program code or knowing specialized software. With this CMGS system, people with no experience, who are not CNC machine operators and who do not know the G-code, will be able to operate the machine.
• We conducted a user study to test proposed solutions. Tests consisted in the comparison of technological operations cloned using the traditional method and the proposed CMGS system. Results show that the proposed system does not increase programming time compared to standard program code development but is easier for the operator.
• We propose an algorithm to calibrate the CMGS system for a specific user, so as to calibrate system parameters to make the machining tool motion most comfortable for each operator.
The outline of the paper is as follows: First, the architecture is presented followed by the concept and implementation of the innovative manual guidance system for the programming of CNC machine tools directly on the machine. Section 2 presents a detailed description of the structure and assumptions of the system. Section 3 contains a description of tensometric control levers and the developed human-machine interface. The experimental validation of the proposed solution is described in Section 4 and conclusions are presented in Section 5.
2. CMGS—CNC Manual Guidance System
In this paper, the authors created an approach that relieves the operator from needing fluency in G-code or any other programming language. Therefore, the approach becomes intuitive and allows for faster training of beginner operators. The approach was inspired by the methods of programming industrial manipulators and by using the method of teachingin. The method of teaching-in stems from the field of robotics and consists in saving all traversed points and settings such that the movement track can be easily reproduced. The application of this method is presented below for the purposes of CNC machine tool operators.
Programming the motion trajectory of a CNC machine tool is a very difficult task as it requires moving two independent kinematic chains. Furthermore, another challenge is to create the process to move the machine in an intuitive way, eliminating mistakes in selecting directions and senses. This requires moving the machine in several axes simultaneously at different speeds and to be able to work closer to the working space of the machine. In order to achieve all these objectives, a new human-machine interface (HMI) had to be created, which makes it possible to enter the necessary data by the CNC operator. The idea was to develop a solution that would allow the machine to be taught by saving individual points in space and related parameters, which could then be used to generate a machining program for the machine tool control system.
The first step to programming the CNC machine tool is to enable the operator to move the body parts of the CNC machine tool to the intended positions. Since CNC machine tools are equipped with electric drives and control systems to maintain a given position, it is not possible to move, e.g., the machining table by pushing it manually. In addition, in the vast majority of cases, CNC machine tools have a lead screw, so switching off the control system and drives also does not allow free movement of the table or headstock. This is

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generate a machining program for the machine tool control system.
The first step to programming the CNC machine tool is to enable the operator to
move the body parts of the CNC machine tool to the intended positions. Since CNC ma-
chine tools are equipped with electric drives and control systems to maintain a given po-
sition, it is not possible to move, e.g., the machining table by pushing it manually. In addition, in the vast majority of cases, CNC machine tools have a lead screw, so switc4hoifn2g0
off the control system and drives also does not allow free movement of the table or
headstock. This is because the screw driven from the load side has self-locking proper-
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CNC machine tools usually have two kinematic chains, i.e., the object branch and the tool branch. In this work, the AVIA Precision Machine Tool Factory type VC760 (Fabryka Obrabiarek Precyzyjnych AVIA S.A., Warsaw, Poland) was used at the Faculty of Mechanical Engineering and Mechatronics of the West Pomeranian University of Technology in Szczecin. The levers were placed on the end element of the tool branch, which is the head and the end element of the object branch which is the table. The lever on the head is designed to handle one direction (two senses) of the axis from the Cartesian system. The data from this lever are sent to the control system, which develops the drive torque of the electric motors to map the movement of the operator’s hand. The lever mounted on the table works in two directions: X and Y. When the operator interacts with the lever to control the head, the CNC machine tool control system must be informed in real time so that it has the correct torque for the N1 drive, thus ensuring a certain speed of movement and allowing accurate positioning of the tool. The same is true for the cross-table control lever, which is responsible for the X and Y axes. The propelling moments are developed on the propelling devices N2 and N3.
System Architecture
The PXI measurement and control platform developed by National Instruments were chosen as an intermediate platform. This platform has a large selection and configuration of input/output cards and enables processing signals in real time. The PXIe-1082 housing was supplemented with a PXIe-8133 controller module equipped with a CORE i7-820QM 1.73 GHz processor. To measure signals from the strain gauges, we chose a PXIe-4330 card equipped with eight channels, enabling measurements with a resolution of 24 bits. Additionally, in order to support digital inputs and outputs, a PXI-7842R card containing an FPGA (field-programmable gate array) Virtex-5 LX50 was applied. The platform was equipped with the necessary terminals with cables and the PMA-1115 touch screen monitor. Additionally, LabVIEW was used to program the PXI platform. LabVIEW is a graphical language that was used to program the FPGA chip of the PXI-7842R card.
A block diagram of the designed system for manual programming of the CMGS is presented in Figure 2. The system consists of input elements (levers and a measurement probe), an input-output element (monitor supporting manual programming), a PXI platform for signal processing and final programming generation, and a CNC machine tool with a control system. The CMGS system is mounted on a three-axis milling machine of medium size of type VC760 produced by Fabryka Obrabiarek Precyzyjnych AVIA S.A. The body system of the machine is equipped with drives with circulating ball feeding screws. The machine has three axes, X and Y implementing the horizontal movement of the cross-table and Z axis implementing the headstock’s vertical movement.
The main control system of the VC760 machine tool drives is the O.C.E.A.N. system. The openness of the system made it possible to implement additional functionalities in order to communicate with the CMGS system. The selected PXI platform is an intermediate element between the levers and the O.C.E.A.N. open control system. The platform communicates with the open control system by exchanging information about the pre-defined position, speed, and acceleration. Based on the measured values and the ones received from the control system, a setpoint speed or position of the axis is generated, which is a setpoint value transmitted to the control system. The setpoints and configuration variables are entered via the touch screen and are used in automatic mode.
To control the cross-table assembly (X axis and Y axis), the main lever attached to the table is used. To control the position of the head (Z axis), an auxiliary lever attached to the headstock is used. The layout of the controls and both levers are shown in Figure 1B.

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amount of force to swing the handheld mouse knob, which caused large motions for the table. As the table moved, the base of the mouse also moved in the person’s hand7. Tofh2i0s behavior made it impossible to maintain a constant tilt of the mouse knob relative to its base, and thus a constant table velocity—see Figure 3A.

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rmeloavtiivnegttohtehfeinwgreirsst.relative to the wrist.
Wiitthh tthhee LLooggiitteecchh FFrreeeeddoomm™™ 22..44 CCoorrddlleessss jjooyyssttiicckk,, iitt wwaass ppoossssiibbllee ttoo cchhaannggee ssppeeeeddss seeaammlleessssllyy..TThheehhaannddwwaasssusuppporotretdedbybythtehjeoyjosytisctkichkahnadnledalenadntdhethoepeorpaetiroantionf tohfetshyestseymsdteempednedpeednodnedthoenortiheentoartieonntoatfitohneocfletnhcehceldenhcahneddohnatnhde joonystthicekj.oCyshtaicnkg.inCghathnegoinrgienthtaetioornicehnatantgioesnthcheaannggeles othf ethaensgtilcekowf itthhersetsipckecwt tioththreevsperetcitcatloatxhies. vInertthicisalcaasxei,s.thIen dthisiasdcvaasnet,atghee odfistahdisvsaonltuatgioenofisththisatsothluetimonovisemtheanttthofetmheovtaebmleenant dofththeeatdajbulsetmanedntthoef iatdsjsupsetmedenatreofnoitts dspepeeedndaernetnoont tdheeppeonsdietinotnobnutthreatphoersiotinonthbeuotrireanthtaetrioonnotfhteheorhieanntdat(iFoinguorfet3hCe)h. and (Figure 3DCu).ring our testing of the levers, we observed that using a manipulator placed directly on theDmuraicnhginoeuerlitmesitniantgesoefrrthoreslaesvseorcsi,atwede wobitshermvoevdinthgaitnuthseinwgraonmgadniripecutliaotnoarnpdlatucerdnindgiarewcatlyyfroonmththeeminatcehnidneededliimreicntiaotne.sTeersrtosrosfacsosmocmiaetrecdialwlyitahvamiloavbilnegsyisntetmhes hwarvoenaglsdoisrhecotwionn tahnadt tthuernminagniapwualaytofrrosmhotuhledinbteesntdaetidondairreyc, tpiorenf.eTraebstlsy ofifxceodmtomtehrecicaollnytraovlaleildabelleemsyesntet m(its mhauvset anlostobsehoawblne ttohamt tohveemfraeneliypurlealtaotirvsehtooutldhebme setaastuiorninagrys,ypsrteemferbabaslye)f.ixTehdertoeftohree,ctohnedtreoslilgend welaesmuepndta(tietdmanudstantohtirdbesoalbulteiotnowmaos vfaebfrriceaetleydruelsaintigvea ptoietzhoesemnesoasruhrainngdlesy(tsytepme 9b2a5s2eA). )Tmheardeefobrye,Kthisetlderes(Figignuwreas3Du)p.dated and a third solution was fabricated using a piezo sIenntshoer chaasnedolef t(htyepdee9s2ig5n2Aed) mlevaedre, ibtys hKainstdleler (pFriagcutricea3llDy)d. oes not deflect with respect to theInbathsee,cyaestethofetahpepdlieesdigfnoercdeliesvmere, aitssuhreadn.dIlneiptiraalctteisctasllhyadvoeesshnoowtndtehflaetcht iwghithstrifefsnpeescst mtoatnhiepublaasteo,ryseatlltohwe apprepcliiseedcfoonrctreoilsomf tehaesumroedve. mIneitniat lotfeCstNs Chamveacshhionwe ntotohlabtohdiyghpasrtitfsfnanesds hmaavneicpluealartloyrisndalilcoawtedptrheeciasedvcaonnttargoel ooff ltohwe smuoscveepmtiebniltitoyfmCaNnCipumlaatcohrisnwe ittohoal dbioredcyt fpoarrctes manedashuarevme ecnleta. rIlnyoirnddeircatoterdedtuhceeatdhveacnotsatgoef othfelocuwffss,utshceepcutifbfisliwtyerme adneispigunlaetdorwsitwhiathstaradinigauge system.

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Sensors 2021, 21, 3860

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rect force measurement. In order to reduce the cost of the cuffs, the cuffs were designed with a strain gauge system.
33..11.. TTeennssoommeettrriiccLLeevveerrss
TThhee ssiiggnniifificcaanntt ddeessiiggnn wwoorrkk cceenntteerreeddaarroouunnddtthheessyysstteemmwwaassttooddeessiiggnnlelevveerrsswwitithh tteennssoommeettrriiccffoorrcceemmeeaasusureremmeennt.t.TThhisissyssytsetmemcocnotnatianiendedtwtwo noencekcinkginsgosrioernietendteadt ant aanngalneogfle90o◦fto90e°actho oetahcehr, oetnhseurr,inegnspurroipnegr pprloaspteicritpylainstbicoitthy oinrthboogtohnoarltdhioregcotnioanl sd. iTrehcetinoencsk.inTghse anreecokpintigmsizaered otoptpirmoivziedde tthoeprreoqvuiidreedthsterernegqtuhirwedhisletrmenaginthtawinhinilgethmeasinpteaciinfiicnsgutshceepstpibeicliitfyic rseuqsucierpedtibfoilritcyorrreeqcut irreecdorfdoirncgoorfrethctersetcraoirndignagugoef stihgenastlsra. iTnhgealoucgaetisoingnoaf lsst.raTihneglaoucgaetisoanndof csotrnasitnrigctaiuongessisasnhdocwonnsitnriFcitgiounrse i4s. shown in Figure 4.

FFiigguurree44.. DDiissttrriibbuuttiioonn ooff ssttrraaiinnggaauuggeessaannddnneecckkiinnggss:: ((AA)) AAuuxxiilliiaarryy lleevveerr;;((BB))mmaaiinnlleevveerr. .
IInn tthheeccoonnttrroolllleevveerrss,,ssttrraaiinnggaauuggeesswweerreeppllaacceeddoonntthheelelevveerrnneecckkiinnggss,,aasssshhoowwnninin FFiigguurree44..TThheeuusseeoof fstsrtarianingaguaguegsesinina fauflul bllrbidrgidegseystyesmtemcomcopmenpseantseastfeosrftohrethinefliunefnlucenocfe eoxfterxntearlnfalctfoarcsto, srsu,cshuacshtaesmtepmerpaeturaretu. re.
33..22.. SSiiggnnaall PPrroocceessssiinngg AA ssiinnggllee cchhaannnneell oofftthheePPXXIIee--44333300mmeeaassuurriinngg ccaarrddiissuusseeddttoommeeaassuurreetthheebbeennddiningg
rraattee ooff tthhee ssttrriinngg ggaauuggee.. DDaattaaaaccqquuisisitiitoionnfrforommththeefufunnctcitoionnbbuutttotnosnsofofthtehemmaianinlelveevreirs icsacrarirerdieoduotuwt iwthitthhethPeXPI-X7I8-4728R42cRarcda.rTdh. eTchaerdcairsdeqisueipqpueipdpwedithwaitnhFaPnGFAPGsyAstesmystfeomr dfaotra dpartoacpesrsoicnegssainndg aanndalaynsiasl.yOsins.eOonf ethoef bthuettbountstoisnsthise tehme eermgeenrgceynsctyopstosipgnsiaglntaral ntrsamnsitmteidtteddidreircetclytlytotothteheCCNNCCcocnotnrotrloslyssytsetmem. U. sUinsignag caacradrdwwithithananFPFGPAGAsyssytesmtemallaolwloswtshtehuesuesretro tsoksipkipthteheapapplpiclaictaiotinonlalyaeyrerininththeePPXXIIssyysstteemm ppllaattffoorrmm.. IInn tthhiiss ccoonnfifigguurraattiioonn,, tthheessaaffeettyy ssyysstteemm iissiinnddeeppeennddeenntt oofftthheemmeeaassuurriinnggaannddpprrooggrraammmmiinnggssyysstteemm,,tthhuusssshhoorrtteenniinnggtthhee ttiimmeeooffccoommmmuunnicicaatitoionnbbetewtweeenenthtehesasfaefteytysyssytesmtemanadntdhethceonctornotlrsoylsstyemsteamndanthdertehfeorreefoinrecirnecarseiansginthgethsaefesatyfeotyf tohfetehnetiernetsiryestseymstfeomr mfoarnmuaalnpuraolgprraomgmraimngmwinitghwa iCthNaCCmNaCchminaecthoionle. Atododl.itAiodndailtlyio, nthaellyd,igthitealdiingpituatlsinofptuhtes coafrtdhewcearredawlsoeruesaeldsotouospedertaoteotpheeramteeathsuerminegapsuroribneg. probTeh. e measurement signal from strain gauge modules is digitally processed to determine the spTeheedmateawshuircehmaengtivseignnCalNfrCommascthrainine gtoaoulgbeomdoydeulelemseins tdiisgtitoalmlyopvero(cFeisgsuerdet5o).dTetheerSensors 2021, 21, x FOR PEER REVIEWfimnianlestpheeesdpdeeedpeant dwshoicnhtahegiivnepnuCt NdaCtamtaocthhineeCtMooGl bSofdroymelethmeeOnt.Cis.Eto.Am.Nov.esy(Fsitgeumrea59n)od.fT2o0hne the status of the main lever buttons. The signals for the X, Y and Z axes are processed by mfineaanl sspoefeadndaedpdeintidons aolnptohset-pinrpoucetsdsiantag taolgtohreitChmMGwShofrsoemsigthnealOs .aCre.Ed.Aep.Nic.tesdysitnemFigaunrde o6n. the status of the main lever buttons. The signals for the X, Y and Z axes are processed by means of an additional post-processing algorithm whose signals are depicted in Figure 6.

FFigiguurere55. .SSchchememeefofor rcoconnvveretritninggmmeeaasusurirninggsisgignnaalslsfrforommlelevveersrsinintotossppeeeeddvvaalulueessfoforrththeeXX, ,YYaannddZZaaxxeess. .

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Figure 5. Scheme for converting measuring signals from levers into speed values for the X, Y and Z axes.

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Figure 6. Signals at different stages of the processing algorithm (SN = 2N, WZ = 400, Fil: 4 Hz). Figure 6. Signals at different stages of the processing algorithm (SN = 2N, WZ = 400, Fil: 4 Hz).
First, the force with which the operator interacts with the lever is calculated as a function of the mFierasst,utrheed fvoorlcteagweiathndwphriecvhiothues coapleibraratotiroinn.teArnacottshewripthrotcheesslecvoenrsiisstscailnculated a using a zonfeuonfcitniosennosiftitvhietymtoeaesluimreindavteolctoamgepoanndenptsreovfimouesascuarleibmraetniot nsi.gAnanlostwheitrhpvraolcueesss consists oscillating aursoiungnda zzeornoe, roefsuinlstienngsiitnivaitycotnotienliumoiunsapterec-osmetptionngeonftsmoofvmemeaesnutresmenesnettsairggneatls with v variables (muoesmoesnctisllaotnintghearmouontodr)z.eTroh,ereaspupllticnagtiionnaocfotnhtiisnuporoucsepdruer-esemttainkgesofitmeaosviemr teont sense t move the tagbeltevalroianbgleosn(emaoxmisenotfsthone tahbelem’sotcorru)c. iTfohremapspylsitceamtio, nbeocfatuhsies pwrhoecnedmuroevminagkes it eas along one steolemctoedveatxhise tthaebrle aarleonaglwoanyesalxoiws osfigtnhaeltcaobmlep’socnreunctisfofrmomsythsteepme,rbpeecnaduisceulwarhen mov axis, whichaalroencguotnoeusteblyecttheedianxsiesntshiteirveitayrezoanlwe.aTyhseloawdvsaignntaaglecomf tphoisnseonltustfiroonmistehaesipeerrpendicu operation waixthiso,uwt hthicehnaereedctuotsowuitcbhytothseinignlsee-nasxiitsivmitoydzeo. nOen. eThderaawdbvaacnktaisgethoefpthosissisboiliutytion is eas
to have a worse representation of circular movements predetermined by the operator. In
fact, the operator is not able to perfectly reproduce the circular movement, so one of the
basic assumptions of the system is to resign from the possibility of saving the entire track of
the movement of the upper limb in favor of saving individual selected and specified points.

Sensors 2021, 21, 3860

operation without the need to switch to single-axis mode. One drawback is the possibil-
ity to have a worse representation of circular movements predetermined by the opera-
tor. In fact, the operator is not able to perfectly reproduce the circular movement, so one
of the basic assumptions of the system is to resign from the possibility of saving the entire track of the movement of the upper limb in favor of saving individual selecte1d0 oafn2d0
specified points.
At the current stage of system development, the operator can set three basic param-
etersA(StNth,eWcuZrraenntdstFaigl)e, ochf sayrastcetmeridzeinvgelothpemwenaty, tthheeompearcahtionrecatonosletmthorveeesb. aTshicepfiarrsatmoenteeriss (tShNe i,nWseZnsaitnidvitFyilz),ocnhea—raScNte.rTizhiinsgptahreamweatyerthalelomwascthhieneoptoeoral tmorotvoess.etTthhee tfihrrsetsohnoeldisutshede itnoseelnimsiitnivaitteyszmonalel—vaSlNue.sTohfisappparliaemd efoterrcea,llwowhischthaelloopwesrafotorretaosiseertgtuhiedtahnrceeshoonlda ustsreadigthot elilnime iwnahtielesmmaalklivnagluitesdoifffiacpupltliteodgfouridcee, twhheictohoalllaofwtesr fcourrveailsiineeragrumidoavnecme oennta. TsthreaiWghZt lipnaewrahmileetemraiksinregspitodnisffiibclueltfotor gthueidseigtnhaeltogoalinaflteevreclu. rTvhiliisneaallromwos vtehme eonpte.rTahtoerWtoZcphaarnagmeetthere ilsevreelspofonfosricbelethfoatr mthuesstibgenaalpgpaliiendlteovethl.e Tcuhfisf taollmowovseththeeompearcahtionrettooochl.aTnhgeelathset pleavraeml oeffteorr,ceFitlh, aist mreuspstobnesiabpleplfioerdsteotttihnegctuhfef tloowm-opvaessthfeiltmera.cShminaellteorolv.aTluheeslaasltlopwarfaomr eatelre,sFsilf,riesrqeusepnotncshibalnegfeorosfetthteinrgettuhrenlowwh-ipleasms ofivltienrg. Stmheamllearcvhainlueetsoaolll,owwhfiocrhaelliemssinfraetqeus ethnet cshyasntegme ovfibtrhaetiroentus.rn while moving the machine tool, which eliminates the system vibrations.
IInn oorrddeerr ttoo ddeetteerrmmiinnee tthhee aapppprroopprriiaattee vvaalluueess ooff tthhee ppaarraammeetteerrss ((SSNN,, WWZZ,, FFiill)) ooff tthhee pprroocceessssiinngg aalglgoorritihthmm, ,1414tetsetsstws ewreercearcraierdrieoduto. uDtu. rDinugritnhge ttehsetst,etshtes,otpheeraotoprerhaatdortohmadakteo mmoakvesminovaecscoinrdaacnccoerdwainthcethweiitmh pthoeseimd poatsteedrnp(aFtitgerunre(F7iBg;urreed7aBn;drebdluaenldinbelsuienldiniceasteintdhietcraute pthaethtroufempoattihono)f. Tmhoeticounr)r.enTthpeocsuitriroenntwpaossiintidoincawteadsbiyndailcaasteerdabttyacaheladsetor tahtteascphienddlteo htheeadsp. Tinhdelestharetaindg. Tphoesistitoanrtiwngaspionstihtieonmwidadsleinofththeemciirdcdleleanodf tmheovciermcleenatnodf tmheovciermclenwt aosf
cthloeckciwrcilsee.wTahsectleosctkswtainsde. iTs hsheotwesnt sintaFnidguisresh7Aow, tnheinprFoicgeusrseo7fAse,tthinegptrhoeceWssZo,fSsNet,tainngdtFhiel pWaZra,mSNet,earsndonFiFlipguaraem8eatnedrstohne tFeisgturreesu8latsnadrethsehtoewstnreinsuFlitgsuarreess9h–o1w1.n in Figures 9–11.

A

B

Figure 7. (A) Teesstt ssttaanndd ccoonnfifigguurraattiioonn,, ((BB)) ppaatttteerrnnuusseeddttooccaalliibbrraatteetthheessyysstteemm..

Figure 8. X, Y, Z axes motion path with fourteen different parameter sets T1–T14. Figure 8. X, Y, Z axes motion path with fourteen different parameter sets T1–T14.

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An Interactive Haptic Guidance System for Intuitive Programming