Boots – shoes – and leggings
Patent
1992-05-01
1993-12-28
Smith, Jerry
Boots, shoes, and leggings
36447403, 318571, 318577, 318578, 318579, G06F 1546, G01B 1100, B23Q 35123
Patent
active
052745635
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a noncontact tracing control system, and more particularly, to a noncontact tracing control system with an improved tracing accuracy.
BACKGROUND ART
A recently developed noncontact tracing control system utilizing a noncontact distance detector for tracing the contour of a model uses an optical distance detector fixed at the tip end of a tracer head and detecting a distance to the model surface, for a tracing thereof. This system eliminates worry about damage to the model, and therefore, a soft material model can be used, and thus the applicability thereof in tracing machining is expected to expand.
Nevertheless, the conventional noncontact tracing control system has a problem in that the tracing accuracy is low at portions of a model where an inclination thereof is large. Namely, in such a portion, an optical measuring axis of a distance detector becomes almost parallel to the model surface, whereby a spot on the model surface is expanded and becomes an ellipsoid, and thus the resolution of the distance detector is lowered, and accordingly, the tracing accuracy also is lowered. Particularly for a trigonometrical distance detector, a measurement sometimes becomes impossible because, depending on this angle, the optical measuring axis interferes with the model surface.
To solve this problem, two detectors are used, the measurement is conducted a number of times, three optional points are selected from among the plurality of points obtained, a normal vector of a model surface is acquired from these three points, and the distance detectors are rotated in the direction of this normal vector, to thereby improve the measurement accuracy. An example of the above is disclosed in Japanese Patent Application No. Hei 1-194500.
Nevertheless, when three points are selected at random from among the plurality of points obtained, such points might be on a straight line or in the neighborhood of a straight line, and an accurate normal vector on the model surface might not be acquired; i.e., if the three points are on a straight line, a normal vector cannot be obtained. Moreover, if they are in the neighborhood of a straight line, at the portion where the rate of change of the curvature of an actual model surface is large, the surface obtained is entirely different from an approximate plane of the model surface.
DISCLOSURE OF THE INVENTION
The present invention has been made in view of the aforesaid drawbacks, and an object of the present invention is to provide a noncontact tracing control system whereby points needed for acquiring a normal vector of an accurate model surface can be selected.
To achieve the above object, in accordance with the present invention there is provided a noncontact tracing control system for tracing machining a workpiece through a tracing of the contour of a model without a contact therewith, comprising first and second noncontact distance detectors inclined by a certain angle to a predetermined straight axis, respectively, and attached to a tracer head controlled by the straight axis and a rotation axis rotated around the straight axis, to thereby measure the distance to the model surface without a contact therewith, respectively, a sampling means for sampling measured values of the above respective distance measured by the first and second noncontact distance detectors at predetermined sampling times, a memory means for storing the measured values obtained by the first noncontact distance detector and the second noncontact distance detector and sampled at a plurality of times of sampling, a point selecting means for selecting three points forming a triangle that is closest to an equilateral triangle, from the measured values, a vector calculating means for calculating a normal vector on the model surface based on the measured values of the three points selected by the point selecting means, an angle calculating means for calculating an angle of a projection of the normal vector projected onto a plane at a right angle to the straight axis,
REFERENCES:
patent: 5015130 (1991-05-01), Matsuura et al.
patent: 5019993 (1991-05-01), Montalcini et al.
patent: 5140239 (1992-08-01), Matsuura
patent: 5182714 (1993-01-01), Matsuura
Matsumoto Eiji
Matsuura Hitoshi
Fanuc Ltd.
Gordon Paul
Smith Jerry
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