JPH0386448A - Digitizing method for copying locus - Google Patents

Abstract

PURPOSE:To restrain an effect due to the fine fluctuation of a copying machine, an electric signal noise or the like, and enable the performance of high precision digitizing by feeding back copying data to a filter for setting a large fixed value of time constant in preference to operation with a time constant corresponding to a copying speed at the sharp shape change part of a model causing the bite of a copying locus. CONSTITUTION:At every sampling time by copying a model 3, the position of a tracer head 2 fitted with a stylus 1 and the variation of the stylus 1 are added, thereby obtaining copying data. This copying data is passed through the digital low pass filter 19 of a copying data processing part 17 so set as to have the smaller time constant at the larger copying speed. Also, when the variation of the stylus 1 reaches an excessive zone due to the sudden shape change of the model 3, the preliminarily determined time constant is set in the aforesaid filter 19.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is based on the approximation trajectory N of the model surface using a copying machine 1a.
This invention relates to a method of digitizing a tracing trajectory to obtain a series of C block data.

<Conventional technology> Conventionally, the digitizing zinc operation in a copying machine approximates a straight line with a certain tolerance (hereinafter referred to as tolerance), and when the tolerance is exceeded, one block is cut out.
By repeating this procedure, we obtained a series of block data that approximated the model surface shape.

In the method described above, for example, if a minute value such as 0.01 is set as the tolerance, the amount of block data will increase to a huge amount if noise-like fluctuation components are superimposed on the point sequence data. Therefore, a low-pass filter is sometimes used to remove fluctuations of several microns in the position detection system of the copying machine and noise components in the displacement signal of the tracer head.

<Problems to be Solved by the Invention> In the case of the above-mentioned conventional technology, if the time constant that determines the cut-off frequency of the low-pass filter is fixed to a constant value, as shown in FIG. 23, a center locus 24 shown by a broken line is passed through the filter to obtain a center locus 25 shown by a solid line, and this center locus 25
will be digitized.

This phenomenon becomes a problem in terms of accuracy of digitizing when the current trend toward higher speed increases.

In addition, there is a strong desire to use the above-mentioned filter to correct the biting trajectory caused by bending of the stylus on a vertically steep wall, but increasing the time constant alone has a large effect on accuracy deterioration due to rounding, making it impractical for practical use. It's not.

As described above, in the conventional methods, there was no effective method for high-speed tracing and high-precision digitizing.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to provide a method for digitizing a tracing trajectory that can obtain digitizing data of a tracing trajectory at high speed and with high precision.

<Means for Solving the Problems> In order to achieve the above object, the configuration of the present invention copies a model with a copying machine, and records the position of the tracer head to which the stylus is attached and the displacement of the stylus at each sampling time. In the digitizing process, which obtains model surface shape data as digitizing data from the scanning data obtained by adding the scanning data, the scanning data is automatically processed so that the time constant becomes smaller as the scanning speed increases. Furthermore, when the amount of stylus displacement is in an excessive range, a digital low-pass filter is configured to set a predetermined large time constant to give priority to the time constant change due to the scanning speed. It is characterized by being smoothed by passing through it.

Function: The copying machine copies the model and adds the position of the tracer head attached to the stylus and the displacement of the stylus at each sampling time to obtain copying data. This scanning data is passed through a digital low-pass filter whose time constant is set to become smaller as the scanning speed increases. Further, when the displacement amount of the stylus reaches an excessive region due to a sudden change in the shape of the model, a predetermined large time constant is set in the filter.

Example of implementation An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 1 indicates a stylus. A stylus 1 is attached to a tracer head 2 of a copying machine, and comes into contact with the surface of a model 3 to measure its shape. The tracer head 2 detects the displacement of the stylus 1 and outputs it to the displacement signal processing section 5 as a detection signal 4 which is an analog signal. The detection signal 4 is a signal for three axes: X, y, and Z axes. The displacement signal processing section 5 includes an amplifier, a multiplexer, an analog-digital converter, and the like. Detection signal 4
is converted into a digital signal by the displacement signal processing section 5, and output as a processed stylus displacement signal 6 to the tracing speed control section 7. At this time, stylus displacement signals 6 are output for three axes. The tracing speed control section 7 forms a loop with the stylus displacement signal 6 and the tracing speed command signal 8 which is an operation signal, and functions so that the stylus 1 traces the surface of the model 3 faithfully. That is, the tracing speed control unit 7 determines the normal vector ε=4 g indicating the model shape determined from the displacement of the stylus 1 on three axes (6 w j cy # ε work),
! A tracing speed command signal 8 is output to the drive motor of each axis so that +ε and '+tI are constant values. The scanning speed command signal 8 is input to a digital-to-analog converter 9,
It becomes an analog signal and is output to the servo amplifier 10.

The servo amplifier 10 is a drive motor 1 that drives the copying machine.
A speed feedback signal 12a inputted from a speed detector 12 that detects the speed of the motor 1 and a signal outputted to the drive motor 11 form a loop to perform feedback control.

Further, the mechanical position detector 13 of the drive motor 11 detects the mechanical position, which is the position of the tracer head 2, and outputs it to the position counter 15 as a position detection signal 14. The position counter 15 integrates the position detection signal 14 and outputs it to the stylus center position calculation section 16 .

Stylus center position calculation unit In one day, the machine position (X, Y
, Z) and the displacement of stylus 1 (ε8.ε2.ε2) are added, and the tracing data (X+ε8.Y+εyj z+ε
8) is output to the scanning data processing section 17. Also,
Stylus displacement signals 18 for three axes synchronized with the machine position sampling are also output to the displacement signal processing section 5 to form a control loop.

The scanning data processing section 17 is provided with a low-pass digital filter 19, as shown in Figure #I2. The time constant (cutoff frequency) of the low-pass digital filter 19 is determined by the coefficient. On the other hand, the time constant T and the scanning speed V of the digital filter 18 shown in FIG.
automatically changed so that the characteristics of

In addition, when tracing a place where the shape changes sharply, such as a vertical wall, the amount of displacement of the stylus 1 on either of the , the operation returns to the normal displacement region again. At this time, K is automatically changed so as to give a large time constant, which is a predetermined fixed value, to the digital filter 19, giving priority to changing the time constant according to the speed. This time constant is replaced by a time constant determined by the characteristics shown in FIG. 4 when the amount of displacement of the stylus 1 returns from the excessive range to the normal range.

The scanning data (X+ε8.Y+ε2.Z+ε,) is input to the digital filter 19 and corrected (X+ε8.Y+ε2.Z+ε,).
ε,)'(Y+ε,)'(Z+εwork)' is output, and is further digitized to become an accurate stylus center position trajectory, and is stored on a data storage medium as model surface shape data 20, which is NG block data. , and is output to the data receiving section 21, which is, for example, a memory medium or a CAD device.

As described above, by changing the coefficient K of the digital filter 19, smoothing is performed with a time constant normalized by the scanning speed during normal scanning, and a sufficient smoothing effect is obtained in the portion where a biting trajectory occurs. will be working.

In the figure, only the machine axes are shown in the area between the servo system, but in reality, this part requires three axes.

<Effects of the Invention> As described above, the present invention smoothes tracing data obtained by a tracing operation through a digital low-pass filter.

Normally, this filter automatically changes the time constant according to the scanning speed, and in addition, in areas where the model shape suddenly changes where the scanning trajectory is cut into, a large fixed value time constant is changed depending on the scanning speed. Set over constant operations. Therefore, it is possible to perform highly accurate digitizing that suppresses the effects of minute fluctuations in the copying machine and noise in electrical signals. Conventionally,
High-speed, high-precision data acquisition can be achieved by eliminating trajectory deviations and biting trajectories caused by the scanning speed that caused errors during high-speed scanning.

[Brief explanation of drawings]

1, 2 and 4 show an embodiment of the present invention,
Fig. 1 is a block configuration diagram, Fig. 2 is an explanatory diagram of the digital filter, Fig. 4 is a diagram showing the time constant characteristics of the digital filter, and Fig. 3 is a diagram showing the digitization trajectory when using conventional technology. It is. In the figure, 1 is the stylus, 2 is the tracer head, 3 is the model, and 4
is a detection signal, 5 is a displacement signal processing section, 6 is a stylus displacement signal, 7 is a copying speed control section, 8 is a copying speed command signal, 1
3 is a mechanical position detector, 14 is a position detection signal, 16 is a stylus center position calculation section, 17 is a scanning data processing section, 19
is a digital filter, 20 is model shape data, 21
is the data receiving section.

Claims (1)

[Claims] The model is copied using a copying machine, and at each sampling time, the position of the tracer head where the stylus is attached,
In digitizing processing, which obtains model surface shape data as digitizing data from the tracing data obtained by adding the amount of displacement of the stylus, the time constant becomes smaller as the tracing speed increases. Furthermore, when the amount of stylus displacement is in an excessive range, a large time constant is set that takes precedence over changing the time constant due to the scanning speed. A method of digitizing a tracing trajectory characterized by passing it through a bandpass filter to smooth it.