JPS62176729A - Digitalizing method for copying locus - Google Patents

Abstract

PURPOSE:To easily perform a time constant change operation in the time of high speed copying by sliding model surface position data through a low speed passage region and by automatically changing time constant of a filter according to copying speed. CONSTITUTION:A displacement signal 13 of a stylus 11 is input in a displacement signal processing part 14, transferred from an analog signal to a digital signal and input in a copying speed control part 16 as a stylus displacement signal 15. The copying speed control part 16 is composed of a loop of the stylus displacement signal 15 and a copying speed instruction signal 17, and the stylus 11 honestly copies the surface of a prototype 12. A position detecting signal 24 from a machine position detector 22 is input in a stylus center position operation part 26 after being added with a machine position counter 25. A machine position and displacement of the stylus in the center position operation part 26 is input in a copying data processing part 27 as added and copying locus data, and digitalizing is performed through a low region passage type filter after being compensated.

Description

[Detailed description of the invention] [Industrial field of application] This invention is a method for converting a model shape to an approximate trajectory N using a copying machine.
Convert to a series of C block data.

The present invention relates to a method for digitizing locus data in a device configured to perform NC processing using a processing machine using the data.

[Conventional technology]

Generally, the digitizing operation in the above-mentioned device is to perform linear approximation with a certain tolerance, cut out one block of data when the tolerance is exceeded, and repeat this procedure to create block data that approximates the model surface position. I was getting a connection.

[Problem that the invention seeks to solve]

Even if it is approximated by a straight line with a tolerance of about 10 microns.

In order to remove noise components without causing an increase in block data, a low-pass filtering operation is applied to the series of data obtained by adding the machine position and tracer head displacement signals. Dull (
There is a conventional method in which the time constant of the filter is automatically changed according to the degree of change in the model shape determined from the differential value of the displacement signal in order to prevent has the following problems.

In the first place, if we try to suppress fluctuations of several microns in the position detection system of the copying machine and noise components in the displacement signal of the tracer head to a level that can be ignored with respect to the allowable amount, it is necessary to remove the filter by inserting the filter. The time constant must be made quite large. Therefore, unless the degree of change in the model shape that changes the time constant is detected promptly, the originally intended prevention of "blurring" of the acquired trajectory cannot be achieved accurately. However, since the displacement signal used to detect the degree of change in the model shape changes from moment to moment due to two types of external disturbances, it is appropriate to perform low-pass filtering and differentiation in the first stage. You will lose your "speediness". Furthermore, if the differential time constant is shortened with the aim of quickly detecting the degree of change, it becomes vulnerable to model shapes whose shapes change slowly.

As described above, in the conventional method, it is difficult to select the time constant of the filter before the differentiator, the time constant of the differentiator, etc., and although it can be handled relatively easily when the scanning speed is low, there are problems in handling when scanning at high speed. I couldn't say no. in particular,
The above time constants are selected according to the medium tracing speed, but the true trajectory (a) as shown in Fig. 2 is blunted as shown in (b), or the disc as shown in Fig. 3. Models with gradual shape changes, such as the one shown in Figure 9, cause variations in digitizing results due to speed, as shown in Figure 9.

As mentioned above, although the demand for higher precision and higher speed in copying machining has been increasing in recent years, there has been no effective method to meet these demands. The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide a method for digitizing a tracing trajectory that enables highly accurate and high-speed tracing machining.

The configuration of the present invention achieves this object in an apparatus that copies a model using a copying machine to obtain locus data, and performs NC processing using the data.

Data obtained by adding the machine position and tracer head displacement signal at each sampling time during copying operation.

It is characterized in that it is smoothed through a low-pass filter, and the time constant of the filter is changed from the open side depending on the scanning speed.

[For production]

By increasing the time constant of the low-pass filter when the scanning speed is slow and decreasing it when the scanning speed is fast, the variation in the degree of "dullness" due to the speed difference is eliminated and accurate scanning is performed.

〔Example〕

An embodiment of the invention will be described with reference to the drawings. FIG. 1 is a block diagram of the configuration of the embodiment.

In the figure, 10 is a tracer head, 11 is a stylus of a scanning detector, 12 is a prototype, 13 is a displacement signal (for 3 axes) of the stylus 11, 14 is a displacement signal processing unit (analog-digital converter, etc.), and 15 is a Processed stylus displacement signal (for 3 axes), 16 a scanning speed control section, 17 a scanning speed command signal, 18 a digital-to-analog converter, and 19 servo amplifiers.

20 is a drive motor for the copying machine, and 21 is a speed detector.

22 is a machine position detector, 23 is a speed feedback signal, 24 is a position detection signal, 25 is a machine position counter, 26
27 is a stylus center position calculation unit, 27 is a scanning data processing unit, and 28 is a tracer head displacement signal.

Reference numeral 29 denotes a prototype shape data receiving section (for example, a memory medium or a processing machine), and 30 denotes prototype shape data to be given to the processing machine. In the figure, only one axis is shown for the servo system, but in reality, this part needs to be for three axes.

Next, the operation of this embodiment will be explained. In Figure 1,
The displacement signal 13 of the stylus 11 is transmitted to a displacement signal processing section 14.
The analog signal is converted into a digital signal and sent to the scanning speed control unit 16 as a stylus displacement signal 15.
is input to. The copying speed control section 16 forms a loop with this stylus displacement signal 15 and a copying speed command signal 17 which is an operation signal, and operates so that the stylus 11 traces the surface of the master model 120 faithfully. That is, the stylus 11-3
A speed command is given to the motor of each axis so that the normal vector ε=Vε+67+εz2 indicating the prototype shape determined from the displacements of the axes (εX, εy, ε2) becomes a certain constant value. Similarly, the position detection signal 24 from the machine position detector 22
is accumulated by the 9 machine position counter 25 and input to the stylus center position calculation section 26.

The center position calculation unit 26 calculates the machine position (X + Y + Z
) and the displacement of the stylus (εX, εy, ε2) are added to form the tracing trajectory data (X+εX, Y+ξy, Z+ε2).
) is input to the scanning data processing section 27. here,
f(X+εx) through a low-pass filter.

After correcting f(Y1εy) and f(Z+62), it becomes possible to perform digitizing to obtain an accurate stylus center position.

The error amount E of "dullness" caused by the filter shown in FIGS. 2 and 3 is proportional to the tracing speed V.

E,=, #v (k, is a constant of proportionality).

Further, the time constant T of the filter is also proportional to the error amount E2.

E2''k2 proboscis T (k2 is a proportionality constant).

Therefore, if the filter time constant is determined from the scanning speed using the relationship shown in FIG. 4, the variation in error amount can be made constant. For prototypes whose shape changes rapidly as shown in Figure 2, a separate function of the control system is used (Learning-type scanning speed control selects a low speed as the scanning speed according to the degree of shape change; Since a high speed is selected, it is possible to achieve an appropriate filtering effect in which the time constant is large in steeply changing portions and small in gently curved portions.

By doing this, we can suppress the "dullness" that conventionally occurs due to the inability to appropriately change the filtering time constant, and also enable high-speed, high-precision scanning operation that eliminates variations in trajectory due to differences in scanning speed. .

〔Effect of the invention〕

As explained above, the model surface position data obtained by adding the machine position and the displacement signal from the tracer head at each sampling time is smoothed through a low-pass filter, and the time constant of the filter is adjusted according to the scanning speed. By automatically changing the time constant, it becomes extremely easy to change the time constant, which was previously difficult to adjust, especially during high-speed copying.

Furthermore, even if the scanning speed changes, it is possible to substantially improve performance by eliminating most of the variation in trajectory data.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention. FIGS. 2 and 3 are explanatory diagrams showing the trajectory error that is a problem in the conventional method, and FIG. 4 is a characteristic diagram showing the size of the time constant with respect to the scanning speed. In the drawing. 10 is a tracer head, 11 is a stylus, 12 is a prototype, 13 is a displacement signal, 14 is a displacement signal processing section, 15 is a stylus displacement signal, 16 is a copying speed control section, 17 is a copying speed command signal, 22 is a machine position detection 24 is a position detection signal, 26 is a stylus center position calculating section, 27 is a scanning data processing section, 28 is a tracer head displacement signal, and 30 is original shape data. Figure 2 Figure 3 111111 11 tall Figure 4 Wandering 1 Beautiful tube 7 Shochu V

Claims (1)

[Claims] In a device configured to copy a model with a copying machine to obtain locus data of the model shape and perform NC machining based on the data, the copying machine position and displacement signal from the tracer head are recorded at each sampling time during copying operation. A method for digitizing a scanning trajectory, characterized in that model surface position data obtained by adding the above is smoothed through a low-pass filter, and the time constant of the filter is changed in accordance with the scanning speed.