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M. Germani et al. Methods and tools for shoes customisationprovide additional clinical variables as global footdeformity and pressures concentration level.Besides, foot motion data are used for driving 3Ddynamic foot geometry simulation. It employs data pointsfrom the foot surface measured during the gait cycle todrive corresponding data points in 3D geometric footsurface model derived from laser scanning system. Thesimulation is used to identify ideal flexion line in the shoe,foot girths values and fluctuation during motion and alsoinsole profile curves.On the other hand, non geometrical parameters, alsoreferred as clinical variables, have been identified in orderto be: user activity level, types of activities undertaken,vascular status, neuropathy status, plantar soft tissueproperties, sweat production, site and nature of skinlesions, range of joint motion, muscle shortening. Theseparameters are assessed by the orthopedic specialist andeach one ranked on a scale from 1 to 10.BiomechanicalvariablesActivity levelTypes of activitiesundertakenVascular statusNeuropathy statusPlantar soft tissuepropertiesSweat productionSite and nature of skinlesionsRange of joint motionMuscle shorteningAssessmentOrthopedicspecialistOrthopedicspecialistOrthopedicspecialistOrthopedicspecialistOrthopedicspecialistOrthopedicspecialistOrthopedicspecialistOrthopedicspecialistOrthopedicspecialistType of dataRank 1 to 10Rank 1 to 10Rank 1 to 10Rank 1 to 10Rank 1 to 10Rank 1 to 10Rank 1 to 10Rank 1 to 10Rank 1 to 10Foot geometry Foot digitizer 3D mesh modelFoot deformity Foot digitizer Rank 1 to 10Pressures map Foot digitizer Pressures mapPressures concentration Foot digitizer Rank 1 to 10Ideal flexion lineFoot girths values andfluctuationInsole profile curvesDynamicsmoduleDynamicsmoduleDynamicsmoduleNumeric valueNumeric intervalsProfile curvespractice have shown to be optimal for certain patientcategories.4.1 CAD systemThe input for designing insole and last is given by theresults of a dedicated measurement system constituted bya 3D laser scanner, baropodometric platform and a gaittool for static and dynamic analysis. Outputs of thissystems are a sequence of foot pressure maps (.bmp or.csv files) and foot geometries (.stl mesh). The pressuremaps sequence is acquired during foot scanning, sopressure distribution over time can be analyzed. In fact,during scanning time span, patient could slightly move hisbody and pressure distribution changes.Foot Pressure Viewer reads a sequence of pressuremaps and extracts that one which better represents footplantar pressure, following a specific algorithm thatmaximizes the quantity of information that is available onthe map.Pressure map is acquired in a discrete way andrepresented by a cloud of points. Only points whosepressure value is not zero are included. Map point X andY coordinate correspond to pressure sensor cell midpointwhile Z represents pressure value.An algorithm works on the point cloud in order toextract characteristic points, such as 1st and 5thmetatarsal points, most prominent points on heel area,medial metatarsal point, centre of pressure (COP) andpressure map barycentre (figure 3). Foot axis is alsocalculated, as the line that minimizes deviation amongpressure points (points are projected on XY plane). 1stand 5th metatarsal points are calculated as the mostexternal points of pressure map. Medial metatarsal pointis the midpoint for the two previous ones. Most prominentpoints are computed in a local reference system that isaligned with the foot axis. Between two possible points, ischosen that one which is more distant from medialmetatarsal point. COP is defined as midpoint betweenmost prominent and medial metatarsal ones. Barycentreis calculated as a weighted average point, where pressurevalue is used as weight.Tab. 1 Clinical and biomechanical variables.The whole clinic and biomechanical variables systemis elaborated by the knowledge based software in order toelaborate appropriate footwear components designparameters (FCDP). In particular outputs refers to lastselection, last typical measurements and girths, uppermaterials selection, shoe components options, heel heightand shape prescriptions.The software that matches biomechanical parameterswith design parameters is based on a knowledge baserepository represented by evidences from the literatureand a wide selection of real test cases. The first type ofknowledge is implemented in algorithms which basicallyfilter the possible range of design parameters on the baseof the specific patient data when explicit rules can beformulated. On the other hand real test cases are storedas a set of design solutions which experience andFig. 3: Extraction of characteristic points of a pressure mapFoot Pressure Viewer has also a functionality toautomatically align foot mesh with pressure map, sincethese data are generally expressed in different referencesystems. The transformation matrix necessary to overlappressure to geometry is calculated from an alignmentprocess of the convex-hull curve of foot sole mesh andconvex-hull curve of pressure map. This approach hasshown good reliability and efficiency. First curve isgenerated as follow: from foot mesh, a new one isgenerated from facets with vertices Z-coordinate less thana threshold value (foot scan is generally aligned along Xaxis and its sole on XY-plane). XY plane projectedJune 15th – 17th, 2011, Venice, Italy701Proceedings of the IMProVe 2011
M. Germani et al. Methods and tools for shoes customisationsilhouette of this mesh is calculated and then the convexhullof obtained curve is derived. On the other hand, thesecond curve is build from the convex hull of pressurepoint cloud.Curves alignment is based on an Iterative ClosestPoint (ICP) algorithm (figure 4). For a correct and fastresult a rough pre-alignment algorithm is used. Pressurepoints bounding box is overlapped to foot sole meshbounding box. In this phase, foot orientation isguaranteed by considering pressure map characteristicpoints. In fact, it must be avoided to overlap toe of footmesh with pressure map heel zone. ICP works on pointsclouds derived from uniform curves sampling. Eachiteration transformation is computed using a Moore–Penrose pseudoinverse matrix.accordingly to color information: point with red color havemaximum elevation, while blue points have zero elevation.As input parameters grid resolution and maximum pointselevation can be specified. Higher number of pointsmeans higher accuracy of final isobar curves whiledecreasing grid resolution curves are smoother.Fig. 6: Pressure surface from pressure map to be used forisobar curves calculation.Fig. 4: Pressure map with foot geometry alignment by ICPapplied to convex-hull curves.As alignment has been reached, pressure map isprojected on the foot sole mesh (figure 5). Result of thisoperation is a new mesh corresponding to foot sole withcolored vertices. Projection is created from a planarquadrilateral mesh, with a texture representing pressuremap applied on it. The texture is created from pressurepoint converting Z coordinates in color information. Inparticular, maximum pressure level has been converted inred, while minimum one in blue. During this phase, alsoan improvement of texture image resolution has beenperformed in order to improve final quality of projectionresult. In fact baropodometric platforms have lowresolutions, generally 2÷4 sensors for square inch.Fig. 7: Examples of isobar curves. In black feet profile from3D mesh is drawn.Once geometrical data about foot and pressure hasbeen acquired and elaborated, next step regards thedefinition of the model of a customized last. Last shapemust be drawn in order to cope with patient pathology,medical prescriptions, but also, if possible, with fashiondictates. The result of the process consists of a set ofNURBS surfaces. They are afterwards used to physicallyproduce the lasts by milling and to be unrolled to pieceswhich can be cut from leather.A set of modeling functionalities has been implementedin the Last Designer module. They cope with foot andlasts points cloud data, lasts geometry editing,modifications and exporting to milling devices and leathercutting. Figure 8 shows the sequence of operations tocarry out in order to obtain a customized last. Firstly, atriangulated mesh representing the last geometry isobtained from points cloud data. Minolta V9i laser 3Dscanner has been chosen for 3D last digitisation. Themain advantage of such system is that it can besuccessfully employed also for acquiring textures.Fig. 5: Foot pressure projected on sole foot mesh.Isobar curves have been calculated from a Nurbssurface obtained from pressure map (figure 6). Curvesare calculated slicing this surface with parallel to XY andequidistant planes (figure 7). The number of curves isspecified by user. A control points grid is defined on theXY-plane and points elevation (z-coordinate) is setFig. 8: Last Designer functionalities and flowchartThe digitization may lead to some errors in the STLmodel and some corrections must be performed: holesfilling, non manifold faces deleting, noise reduction, meshdecimation, isolated triangles deleting, etc… All theseoperations have been implemented through automatedcommands, easy in using also for non-skilled operators.June 15th – 17th, 2011, Venice, Italy702Proceedings of the IMProVe 2011
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