Boots – shoes – and leggings
Patent
1987-02-12
1989-03-21
Smith, Jerry
Boots, shoes, and leggings
36447435, 318603, 318621, G01B 2120, G05B 1918
Patent
active
048149985
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to a digitizing method. More particularly, the invention relates to a digitizing method in which movement is effected along at least one axis under numerical control and along other axes under tracer control to obtain numerical data for specifying the three-dimensional shape of an object.
A digitizing method is available in which numerical data for specifying the three-dimensional shape of a model are obtained by moving a tracer head in the X-Y plane under numerical control, moving the tracer head along the shape of the model in the direction of the Z axis under tracer control, and sampling the present values along each axis at predetermined time intervals.
In this conventional digitizing method, a commanded position is taken as the present position with regard to the axis (numerical control axis) that is under numerical control, but the present position with regard to the axis (tracer control axis) under tracer control is obtained through a follow-up technique.
A present position monitoring method based on follow-up is one which the present position along an axis is monitored by counting a number of pulses each of which is generated whenever a motor for drive along the axis rotates a predetermined amount. The present position along the tracer control axis is the actual machine position.
With the conventional digitizing method, therefore, the present position along the numerical control axis is represented by the commanded position, the present position along the tracer control axis is represented by the machine position, and there is an error corresponding to the servo-system delay between the positions along the numerical control axis and tracer control axis. The problem that results is that highly precise digitizing cannot be performed.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a digitizing method through which the present positions along the numerical control axis and tracer control axis can both be taken as machine positions, whereby highly precise digitizing can be carried out.
The present invention relates to a digitizing method for obtaining numerical data for the purpose of specifying the three-dimensional shape of an object by effecting movement along at least one axis (X or Y axis) under numerical control and along another axis (Z axis) under tracer control and reading the present position along each axis at predetermined time intervals.
Since velocity is commanded in tracer control, commanded position does not play a role in such control. Consequently, the present position along the tracer control axis is always the machine position. In numerical control, on the other hand, a target position is commanded, so that the present position along the numerical control is a commanded position. Accordingly, with regard to the numerical control axis, the machine position is obtained by substracting the amount of servo-system delay from the commanded position, and this machine position is taken as the present position.
In this manner the present positions along all of the axes can be obtained as machine positions to make highly precise digitizing possible.
In numerical control, commanded positions Xa, Ya along the X and Y axes are obtained by performing the operation indicated by the expressions produced along the respective axes over each time interval .DELTA.T are .DELTA.X, .DELTA.Y. Further, the servo-system delays along the respective axes agree with the contents E.sub.x, E.sub.y of error registers contained in these servo-circuits.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of a system for executing digitizing processing in accordance with the present invention;
FIGS. 2(A) and (B) are explanatory views of axis control according to the present invention; and
FIG. 3 is an explanatory view of machine position sampling.
DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 is a block diagram of a system for realizing digitizing processing in accordance with the present invention, in which t
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patent: 4626756 (1986-12-01), Inaba et al.
patent: 4656405 (1987-04-01), Kiya et al.
patent: 4702652 (1987-10-01), Rokksku et al.
Fanuc Ltd.
MacDonald Allen
Smith Jerry
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