Data processing: structural design – modeling – simulation – and em – Modeling by mathematical expression
Reexamination Certificate
1999-03-08
2002-04-16
Frejd, Russell W. (Department: 2123)
Data processing: structural design, modeling, simulation, and em
Modeling by mathematical expression
C703S001000, C345S420000, C702S153000
Reexamination Certificate
active
06374198
ABSTRACT:
FIELD OF THE INVENTION
The present invention refers to the creation of numerical models representing tridimensional actual models. The invention was developed with particular reference to the creation of models of tridimensional surfaces. One particular application sector of the invention refers to the creation of numerical models of surfaces by means of the acquisition of points from a tridimensional actual model.
In particular, although not exclusively, the invention was developed to be applied to technical sectors which require computer processing of numerical or mathematical models of so-called “sculptured” surfaces, such as for example those of motor vehicle body parts, of fairings, of shaped paneling, of casings for electrical appliances, of articles in the sector of design or ornamental models, of protective guards for machines or motors, which cannot be identified as union or development of elementary or primitive surfaces.
BACKGROUND OF THE INVENTION
The known methods for the creation of numerical models of sculptured surfaces mainly use acquisition systems comprising continuous probes which explore the characteristics of the surface of a tridimensional actual model, providing an enormous mass of output data which represent the spatial coordinates of an equally high number of separate points of the surface of the model. This enormous amount of information is then processed by a computer programmed to provide output data which represent the shape of the surface of the actual model and which can be subsequently used by designers for any kind of analysis, calculation, modification or electronic processing of the characteristics of the surface itself. For example, the numerical or mathematical model of the surface can be used as input data for programs which calculate the resistance to certain types of stress, for Computer Aided Design (CAD) programs or for Computer Aided Manufacturing (CAM) programs and the like. The principle on which the above type of known systems is based is that the closer the points measured on the surface of the actual model are to each other, the more faithful the numerical reconstruction of a model with this surface will be. The utmost development of this principle has led to the production of increasingly sophisticated measuring instruments, which are able to supply the computer with the data of so-called “point clouds” to emphasize the high surface unit density.
However, the above-mentioned known systems for the creation of numerical models of sculptured surfaces encounter obvious limitations in defining numerical models of surfaces which must be subsequently processed electronically. The processing programs are in fact generally designed for the input of a much lower quantity of data than is generated by the known “point cloud” measurement systems. In many of these programs, moreover, the input points represent the same number of “nodes” of the mathematical model, on which also rather complex calculations are made and whose relative position also significantly affects the output results. This aspect is well known to expert technicians involved in structure resistance calculations, for whom the preliminary task of identifying the nodes, the so-called “meshing” phase of the model, often takes priority with respect to the actual calculation phase since an incorrect selection of the nodes can lead to totally unreliable results. A similar problem is encountered by designers who use CAD programs, who often find it difficult, if not impossible, to electronically handle surfaces identified by Incorrectly selected parameters or nodes. The modification, stretching or junction of bad numerical models of surfaces can lead to unforeseeable results, such as an unforeseen discontinuity in modified modeled surfaces, which are usually difficult to correct.
Furthermore, an additional disadvantage of the known procedures for the creation of numerical models derives from the fact that to obtain a surface model that can be easily processed by the programs used by designers, the data of the “point clouds” must be processed by the application of algorithms which provide a reduced number of numerical parameters representing the shape of the surface of the actual model. While it is fairly simple to realize at a glance that the sculptured surfaces of actual models have a generally harmonic development and are well joined together, it is extremely difficult to design a good program which can identify, select or calculate precisely those nodal points from the enormous quantity of data from the “point clouds” which can effectively represent the shape of these surfaces. Minor errors in the data of a few points of all those acquired can propagate without control in the calculation of numerical models of surfaces, without taking into account the fact that, due to the large quantity of input data, this calculation may prove to be long and costly and require calculation power that is often not available.
One radically different system with respect to the processing of point clouds for the mathematical representation of actual models is described in the document U.S. Pat. No. 4,979,224. According to this known system, the surface of the article which must be modeled is divided into one or more areas and an acquisition machine is operated to acquire the measurement of points along the boundaries of the areas with a certain degree of precision. The boundaries are mathematically modeled by means of algorithms and equations which minimize the deviation from the measured points. The surface of each area on the actual article is then measured at selected points and the values are compared to the values derived from the modeling equations at the same points and the equations are modified to minimize the deviation of the model from the measured points. The procedure is repeated by means of subsequent iterations until the required degree of surface modeling accuracy is achieved.
One disadvantage of this known system consists of the fact that there is no guarantee that the iterative procedure converges towards a mathematical surface model that, at each subsequent iteration, becomes more similar to the actual surface. Another disadvantage consists of the fact that the calculation of the minimum deviation of the model compared with the measured points implies the resolution of equation systems that, iteration after iteration, are of higher orders, meaning that the procedure must inevitably be interrupted when the available calculation power is no longer sufficient, regardless of the accuracy achieved. In addition, the complexity of the calculations necessary to model complex surfaces requires the adoption of powerful and expensive computers and the use of processing times which can be considerable.
The continuous probes used in the known type systems can be the contact type or the non-contact type, for example laser probes. These latter probes emit a beam of electromagnetic waves, in particular a beam of laser light, along a predetermined axial direction and, by means of a receiver, can detect the spatial position of a point on the surface of the object on which the electromagnetic waves are reflected.
A first known type of laser probe, which will be identified subsequently with the term “measurement band type”, transmits an analogue or digital output signal proportional to the distance of the point on the surface from the probe along the predetermined axial direction.
As shown in
FIG. 3
, in the known acquisition systems using laser probes of the above-mentioned first type, one or more probes
12
are translated along a direction X
1
at a predetermined distance from an object O whose outline is to be detected, in such a way that the furthermost Z
0
and the closest point Z
1
of the object are included in the measurement band D of the probe, which sends an analogue or digital output signal, proportional to the distance of the outline of the object O along the predetermined measurement axis Z, to a processing system.
The known type of measuring systems mentioned above using measurement
Bacoccoli Paolo
Schifa Maurizio
Frejd Russell W.
Mirai S.r.l.
Sughrue & Mion, PLLC
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