JPH05253804A - Non-contact tracer control device - Google Patents

Abstract

PURPOSE:To continue smoothly tracer control by stopping temporally tracer control for controlling a turning angle stably at a position when distance measurement can be achieved even in case losing temporally a position detecting function. CONSTITUTION:In the case of tracer processing of a workpiece 35 while tracing non-contactly the shape of a model 6, for instance after a distance measurement by using distance sensors 5a and 5b becomes impossible because of reaching a level difference of the model 6 when diplacement data La and Lb which are measured again by turning the sensors 5a and 5b are input, the displacement data La and Lb are used as displacement input for tracing after smoothing the displacement data La and Lb for a certain period. And a tracer control can be smoothly continued even at the level difference area.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-contact tracing control device, and more particularly to a non-contact tracing control device for tracing a work while tracing a model shape in a non-contact manner.

[0002]

2. Description of the Related Art Conventionally, in order to improve the accuracy of contouring, a non-contact contouring control device for contouring a workpiece while non-contacting the shape of a model has been known.
In this non-contact tracing control device, a tracer head having an optical distance detector using a semiconductor laser, a light emitting diode or the like mounted at its tip is used. Using such a tracer head, the profile control is executed by obtaining the displacement amount data from the coordinates of the spot position while performing feedback control so that the distance from the model surface becomes a constant value.

However, in the case of non-contact, generally, only one-dimensional displacement information can be obtained at the same time, so that the measurement accuracy by the tracer head is lower than that of the contact-type profile controller. In order to increase this measurement accuracy, the optical axis is mounted on the tracer head so that the optical axis can be rotated around this vertical axis while keeping the angle formed by the optical axis with respect to the vertical axis passing through the table. The rotation angle is always controlled so that the angle formed by the optical axis and the model surface is nearly vertical. However, if the shape of the model has a portion where the inclination angle changes discontinuously, such as a stepped portion, the rotation angle control of the optical distance detector may be hindered, and the contour control may not be possible.

Therefore, in order to eliminate such inconvenience, the inventors have temporarily stopped the tracing control and the angle control when the light receiving position on the model is out of the detection range of the optical distance detector during the tracing control. And apply a rotation command to the detector until it enters the detection range, then move the table based on the distance information of the detector and restart the profile control. (See the application specification of Japanese Patent Application No. 3-208814).

[0005]

However, since the angle control is once stopped after moving out of the detection range of the optical distance detector, even if the distance information is given from the detector after that, the profile control of the profile control is not performed. It is not necessarily appropriate as information for this.

That is, when the distance to the model cannot be measured at the step portion, the optical distance detector is rotated and the measurement is restarted. Immediately after that, the displacement data input due to the step difference is input. Changes rapidly. Further, generally, the measurement distance input to the tracing control device before and after the rotation control tends to be a discontinuous value. This is because the distance between the tracer head and the model surface does not change because the profile control is stopped, but the measurement point on the model changes when the optical distance detector rotates.

Due to such various causes, generally, there has been a problem that the profile control operation in the abruptly changing portion of the model shape and the rotation angle control associated therewith are still likely to be unstable.

The present invention has been made in view of such a point, and even if the position detection function is temporarily lost, the position control can be temporarily stopped and the position where the distance can be measured. Therefore, it is an object of the present invention to provide a non-contact profile control device capable of continuing smooth profile control by stably controlling the rotation angle.

[0009]

According to the present invention, in order to solve the above-mentioned problems, in a non-contact contouring control device for contouring a workpiece while non-contacting a model shape, a vertical direction passing through a table on which the model is arranged. When the distance from the tracer head to the model is opened beyond the measurable range of the distance sensor and a tracer head mounted with a distance sensor that rotates while holding a constant inclination angle with respect to the axis, Measurement control means for temporarily stopping the profile control and rotationally controlling the distance sensor to a measurable position, and a measurement distance input from the tracer head immediately after the measurement control means issues a command to restart the profile control. A tracing control means for outputting the smoothed control command to the tracer head based on the above, and restarting the tracing control. Non-contact tracing control apparatus according to claim Rukoto is provided.

[0010]

The non-contact tracing control device of the present invention, when the workpiece is processed while tracing the model shape in a non-contact manner, for example, after reaching the stepped portion of the model and the distance measurement by the distance sensor becomes impossible, When rotating and inputting the displacement data measured again, the displacement data is smoothed for a fixed time and then used as the displacement input for tracing. As a result, the smoothing control can be continued even at the step portion.

Similarly, after the distance measurement by the distance sensor becomes impossible, the tracking gain of the motor control for rotating the sensor is set low, and the tracking gain is set from the time when the measured displacement data is input again. Gradually increase to the initial set value. This stabilizes the followability of the contour control with respect to the rotation angle control.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention. Here, a schematic configuration of the non-contact profile control device 1 and the machine tool 3 which is drive-controlled by the control device 1 will be described. The machine tool 3 includes a machining head portion 36 and a work rest portion 3
It consists of 7. The machining head unit 36 is provided with a spindle motor (not shown) that drives a tool 34 such as an end mill, and a Z-axis servomotor 32z that moves the entire machining head unit 36 up and down relatively with respect to a work rest 37. There is. Further, the work placing section 37 is provided with a table 31 on which the work 35 and the model 6 are placed. The table 31 is moved in the direction of each axis by the X-axis servo motor 32x and the Y-axis servo motor 32y.

The tracer head 4 is provided on the lower surface of the machining head 36 along the vertical axis passing through the table 31 together with the tool 34. At the tip of the tracer head 4, each of the optical distance sensors 5a and 5b is
The tracer heads 4 are fixed in parallel with each other at an angle φ with respect to the optical axis of the irradiation light. Each of the optical distance sensors 5a and 5b maintains a constant angle φ with the tracer head 4 around the C axis that constitutes the central axis of the tracer head 4 by driving the C axis servo motor 32c that rotationally drives the tracer head 4. While rotating integrally,
It vertically moves integrally with the processing head unit 36.

The optical distance sensors 5a and 5b themselves are
For example, irradiation means such as a semiconductor laser or a light emitting diode and C
This is an ordinary optical distance sensor composed of a light receiving element such as a CD, and determines the distance from the sensor 5a, 5b to the light receiving position on the model 6 based on the position data of the reflected light on the light receiving element and the irradiation angle. It is what you want. Therefore, similar to the conventional product, when a model having a step portion in which the distances between the sensors 5a and 5b and the surface of the model 6 are drastically changed is used, the light receiving position on the model 6 is caused by the inclination of the irradiation light. Is significantly displaced, and it becomes impossible to detect the light receiving position on the model 6 on the light receiving element. In order to eliminate such inconvenience, in the apparatus of the embodiment of the present invention, the tracer head corresponding to the distance measurement value La of the optical distance sensor 5a when the irradiation light of the optical distance sensor 5a intersects the C axis. The distance between 4 and the surface of the model 6 is set as a prescribed value L. In the state shown in FIG. 2, the distance L in the C-axis direction from the most distal position of the tracer head 4 to the light receiving position P1 on the model 6 by the irradiation of the optical distance sensor 5a is between the model 6 and the tracer head 4. Is defined as the clearance of.

Further, the non-contact tracing control device 1 has a control means and a microprocessor 11. The microprocessor 11 stores a ROM 12 storing various system programs for performing drive control of the machine tool 3, tracing control by the tracer head 4, and distance measurement values La and Lb from the optical distance sensors 5a and 5b. A RAM 13 for temporarily storing data such as data, a nonvolatile memory 14 for storing setting data such as various parameters, tracing direction, table moving speed (tracing speed), etc., and an operation panel 2 as a data input means are attached. The interface 15 and the like are connected via the bus 10.

Servo motors 32x, 32y, 32z for respective axes of the machine tool 3 connected to the non-contact profile control device 1
Is a servo amplifier 18x for each axis according to speed commands Vx, Vy, Vz for each axis input from the microprocessor 11 via the D / A converters 17x, 17y, 17z for each axis.
It is rotationally driven by 18y and 18z. The pulse coders 33x, 33y, 33z arranged on the respective axes output feedback pulses FPx, FPy, FPz for each predetermined rotation of the respective axes to output the current position registers 19x, 19y, 19z for the respective axes.
To enter. Current position register 19x, 19 for each axis
y and 19z are current position data Xa, Ya, Za, for each axis, which are cumulatively added or subtracted from the feedback pulses FPx, FPy, FPz according to the rotation direction of each axis.
And input these values to the microprocessor 11. Further, the optical distance sensors 5a and 5b perform distance measurement in response to a measurement command input from the microprocessor 11 via the control circuits 21a and 21b at predetermined sampling intervals, and the respective distance measurement values La and Lb are A
Input to the microprocessor 11 via the / D converters 16a and 16b. Each time the measurement results La and Lb are input, the microprocessor 11 receives the values of the current position registers 19x, 19y and 19z of each axis and the current rotation position of the tracer head 4, that is, the C-axis servomotor 32c.
The values of the current position registers provided in correspondence with 1 to 1 are made to correspond one-to-one, and at least the latest two sampling results are cyclically stored in the RAM 13.

In such a structure, first, the model 6 and the work 35 are placed and fixed on the table 31, and the table 31 and the machining head 36 are set so that the tip of the tracer head 4 approaches the trace start point on the model 6. .. After that, when the machining direction key is operated by setting and inputting the tracing direction and the table moving speed (tracing speed) to the non-volatile memory 14 via the operation panel 2, the microprocessor 11 operates the machine tool 3 according to the control program stored in the ROM 12.
Follow the control of.

The microprocessor 11 which has started the profile control outputs speed commands Vx and Vy for each axis relating to the table 31 based on the profile direction and the table moving speed set in the non-volatile memory 14. By driving and controlling the servo motors 32x and 32y of the respective axes via the D / A converters 17x and 17y of the respective axes and the servo amplifiers 18x and 18y, the table 31 moves in the XY plane.
At the same time, the microprocessor 11 uses the optical distance sensor 5
The distance measurement values La and Lb by a and 5b are detected at every predetermined sampling period, and the distance measurement value of the optical distance sensor 5a is measured by the distance measurement value corresponding to the clearance L between the model 6 and the tracer head 4 and the sampling result of this time. The difference from the value La is calculated. When this value is converted into the distance in the C-axis (Z-axis) direction to calculate the position deviation related to the clearance, the speed command Vz to the Z-axis servo amplifier motor 32z is output based on this position deviation. This speed command V
The D / A converter 17z and the servo amplifier 18z are driven and controlled by z to move the machining head 36 up and down relative to the table 37. As a result, the work 35 can be cut into the same shape as the model 6 by the tool 34 while maintaining the clearance between the surface of the model 6 and the tracer head 4 at the specified value L.

At this time, in the microprocessor 11, the sampling data for the previous time and the current time stored in the RAM 13, that is, the distance measurement values La and Lb of the optical distance sensors 5a and 5b and the respective axis values are stored in the RAM 13 at predetermined sampling intervals. The value of the current position register 19x, 19y, 19z,
Further, the current rotation position of the tracer head 4 and the offset data between the optical distance sensors 5a and 5b are read, and the coordinate data of the light receiving position on the model 6 by the optical distance sensors 5a and 5b at the time of the previous sampling and the current sampling are calculated. calculate. The normal vector of the current light receiving position on the surface of the model 6 can be obtained based on the coordinate data of these light receiving positions. Microprocessor 1
1 is a rotation command Sc for rotating the tracer head 4 to a position where the normal vector is projected on the XY plane of the table 31.
To output D / A converter 17c and servo amplifier 18
The C-axis servomotor 32c is driven via c. As a result, the tracer head 4 is rotationally driven until it coincides with the projection position of the normal vector, and can be moved to a position where the optical axis of the irradiation light of the optical distance sensors 5a and 5b approximates the normal vector.

As shown in FIG. 3, for example, the table 31
Is transmitted in the positive direction of the X-axis in FIG. 1, the C-axis is at the imaginary position indicated by the chain double-dashed line in the figure, and the current light-receiving position on the model 6 by the optical distance sensors 5a and 5b is P.
an = (Xan, Yan, Zan) and Pbn = (X
bn, Ybn, Zbn). The previous light receiving position is Pa _n-1 = (Xa _n-1 , Ya _n-1 , Za
_n-1 ) and Pb _n-1 = (Xb _n-1 , Yb _n-1 , Zb
_n-1 ), the three light receiving positions Pan,
Pbn and Pa _n-1 of the data using the two surfaces vector _{Va = (Xa n-1 -Xan} , Ya n-1 -Yan, Za
_n-1 -Zan) and Vb = (Xbn-Xan, Ybn--Ya
n, Zbn-Zan) is calculated. Then, from the outer product of the surface vectors Va and Vb, the normal vector V = (Xn, Yn, Zn)
To calculate the normal vector V as XY in the table 31.
A rotation command for moving the tracer head 4 to a position projected on a plane, that is, a rotation angle from the X axis is tan ^-1 (Yn /
The rotation command Sc that is Xn) can be output.

Therefore, as the tracer head 4 is rotationally controlled, the postures of the optical distance sensors 5a and 5b are such that the optical axis of the irradiation light approximately coincides with the normal vector of the surface of the model 6. Moreover, the clearance between the surface of the model 6 and the tracer head 4 is always kept at the specified value L. Similarly, also in the next sampling cycle, the light receiving positions Pa and Pb on the model 6 by the irradiation light are kept within the range detectable by the light receiving elements of the optical distance sensors 5a and 5b, and accurate profile processing by adaptive control is performed. Can be implemented.

FIG. 4 is a diagram for explaining the principle of measurement by the non-contact sensor 5. When the stepped portion is formed on the surface of the model 6, the irradiation light from the sensor A is received at the light receiving position P.
Up to 1 can be detected by the light receiving element of the sensor A.
However, if the tracing control progresses beyond the C-axis position indicated by the broken line in the figure, the sensor A in the tilted state cannot detect the position from the surface of the model 6. That is, the sensor A exceeds the allowable value of the set measurement range and becomes incapable of measurement. In the profile control device, when the sensor A cannot be measured, the C-axis servomotor 32c
Then, a predetermined amount of rotation command is output to rotate to the position of the sensor B around the C axis.

When the distance to the surface of the model 6 can be measured again at the position of the sensor B, the tracing control is started, but the irradiation light of the sensor B is input at the point P2 of the model 6 as the light receiving position. The measured value (deviation) becomes discontinuous. Therefore, if the tracing operation is followed as it is, the tracing operation becomes extremely unstable immediately after the restart of the tracing control. This is because the non-contact sensor A is not accurately stopped at the light receiving position P1 of the irradiation light, and thus the light receiving position P2 of the irradiation light when the measurement is restarted is displaced. Alternatively, even if the restart position of the conforming control exactly matches the stop position, the stepped portion of the model 6 surface immediately after the restart causes
This is because the control cannot sufficiently follow the deviation that is input.

FIG. 5 is a diagram showing a temporal change in the measured displacement at the step portion. The vertical axis of FIG. 7A shows the size of the displacement data. The dotted line portion is the time zone when measurement is impossible. The non-contact tracing control device of the present invention controls the distance sensor to a measurable position by rotation, and immediately after a command to restart the tracing control is issued, based on the measured distances La and Lb input from the tracer head 4. 4 is a control for restarting the control by outputting a control command based on the smoothed measurement value. For example, each of the distance measurement values La and Lb is temporarily smoothed. It is realized by inputting the displacement amount to the microprocessor 11 via the A / D converters 16a and 16b. In FIG. 5 (B), the vertical axis shows the magnitude of the smoothed displacement amount, and the dotted line portion is the time zone in which measurement is impossible, as in FIG. 5 (A).

FIG. 6 is a block diagram showing an example of a method for smoothing displacement data. The displacement data from the sensor 5 is normally input to the filter F1 by the changeover switch S and processed by the microprocessor 11 via the A / D converters 16a and 16b. During profile processing, for example, when the stepped portion of the model is reached and distance measurement by the distance sensor becomes impossible, the changeover switch S is switched. As a result, when the sensor is rotated and the displacement data measured again is input, the displacement data is input to the filter F2 at the time of discontinuity. The displacement data is continuously input to the filter F2 until the smoothed displacement amount matches the input displacement data, and then switched to the filter F1 again.

As described above, when the measurement cannot be performed once, the displacement input is smoothed for a certain period of time and then used as a displacement input for tracing by the microprocessor 11. As a result, the smoothing control can be continued even at the step portion. The reason why the filter F1 smoothes to a certain extent even in normal times is to reliably remove small vibration components.

In the above description, when the smoothing control is restarted, the smoothing circuit for the displacement input is used.
Although the smoothed control command is output to the tracer head 4, a similar smoothing process is executed for the gain of the rotation command Sc to the C-axis servomotor 32c that rotates the tracer head 4. Also, the same effect can be obtained.

[0028]

As described above, according to the present invention, when a discontinuous measured displacement amount is input in the profile control, the displacement input is smoothed and converted into a smooth displacement change, and then the profile control is performed. Configured to continue. Therefore, it is possible to provide a non-contact profile control device that stabilizes the followability of profile control and enables accurate profile control.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a schematic configuration of a tracer head of the same embodiment.

FIG. 3 is a diagram illustrating an example of profile processing according to the present invention.

FIG. 4 is a diagram illustrating a measurement principle of a non-contact sensor.

FIG. 5: Measured displacement (A) and smoothed displacement amount (B)
It is a figure which shows the change of.

FIG. 6 is a block diagram showing an example of a method for smoothing displacement data.

[Explanation of symbols]

 1 Non-contact tracing control device 2 Machine tool 4 Tracer head 5a, 5b Optical distance sensor 6 Model

Claims (1)

[Claims] 1. A non-contact contour control device for contouring a workpiece while non-contacting a model shape, and rotating while maintaining a constant inclination angle with respect to a vertical axis passing through a table on which the model is arranged. When the distance from the tracer head to which the distance sensor is mounted and the distance sensor exceeds the measurable range of the distance sensor to the model, the tracing control can be temporarily stopped and the distance sensor can be measured. Measurement control means for controlling rotation to various positions, and a control command smoothed to the tracer head based on the measurement distance input from the tracer head immediately after the measurement control means instructs restart of the tracing control. A non-contact profile control device comprising: a profile control means for restarting the profile control for outputting.