JPH08178646A - Method for controlling profiling measurement - Google Patents

Abstract

PURPOSE: To prevent measuring efficiency from decreasing by causing a storage circuit to store the definite number of stylus coordinate values which are constantly renewed with the newest ones. CONSTITUTION: A stylus is held against a profiling probe 1 in such a way as to be able to be displaced three-dimensionally. The amounts of displacement of the stylus with respect to a probe body are detected by X-, Y-, and Z-axis displacement detectors, 11, 12, 13, respectively, and are inputted to an adder circuit 22 and a CPU 21 in a drive controller 2. The coordinate values for each axis of a three-dimensional measuring instrument 3 controlling the movement of the probe main body are measured by X-, Y- and X-axis encoders, 31, 32, 33, respectively, and are inputted to the adder circuit 22. The amounts of displacement and the coordinate values are added together by the adder circuit 22, and the results 25 are regarded as the coordinate values for the stylus. A storage circuit 23 stores the definite number of coordinate values for the stylus which are constantly renewed with the newest ones. When the amounts of displacement of the stylus with respect to the probe 1 are out of a predetermined allowable range, the probe 1 is moved to return to the definite number of coordinate values stored, and then measurements are restarted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling scanning measurement using a scanning probe in which a stylus can be displaced in three-dimensional directions with respect to a probe main body and a computer-controlled coordinate measuring machine.

[0002]

2. Description of the Related Art As a device for measuring the coordinates and shape of the surface of an object to be measured, particularly the coordinates and shape of the surface of the object to be measured having a free-form surface, a computer-driven controllable coordinate measuring machine equipped with a scanning probe is well known. is there. In this copying probe, for example, a stylus having a spherical probe on the tip of a probe body as shown in Japanese Patent Laid-Open No. 5-256640 is held so as to be displaceable in the three-dimensional direction, and a spring or the like is used. The stylus is made to constantly return to the vicinity of the center of the displaceable range, and the displacement amount of the stylus from the center in the XYZ axis directions is detected by displacement detectors such as linear encoders. There is something.

A method for scanning and measuring a free-form surface with a combination of a computer-controllable three-dimensional measuring machine and a scanning probe as described above is shown in JP-A-63-131016 and JP-A-63-131017. Like
The spherical probe at the tip of the stylus mounted on the scanning probe is moved relative to the control target trajectory while continuing to contact the surface of the object to be measured, and the center coordinate value of the spherical probe is measured at predetermined time intervals. The measured coordinate values of the surface of the object are recorded in a storage circuit in the drive control device. In addition, during scanning measurement, the stylus is always pushed into the probe body so that it can be sensed in which direction the stylus is displaced in the three-dimensional direction with respect to the probe body. Has been done. This preset constant displacement amount is hereinafter referred to as a reference displacement amount. The amount by which the stylus is pushed into the body is read by the displacement detector for each of the XYZ axes in the probe body,
The magnitude of the vector having one value as a component is always constant, that is, is controlled by the drive control device so as to match the reference displacement amount, and at the same time, the magnitude of the vector falls within a predetermined allowable range with respect to the reference displacement amount. The scanning measurement control is performed in which the relative movement is performed along the control target trajectory surface while monitoring whether or not it is present.

In the measurement of a free-form surface using a combination of a computer-controllable coordinate measuring machine, a scanning probe, and a scanning measurement control method, a probe of a touch probe that outputs a touch signal at the moment of contact with an object to be measured is used. It has an advantage that a more complicated free-form surface can be measured at high speed, as compared with a measuring method in which contact and withdrawal are repeated at each point so as to proceed along the shape of the object to be measured. For this reason, the use such as copying measurement of a mold having a free curved surface in several hundreds of sections, automatic day and night operation, etc. is gradually increasing among users of the coordinate measuring machine.

[0005]

However, the moving speed for scanning measurement set in advance in the drive control device is faster than the response speed capability of the control of the entire device including the coordinate measuring machine and the drive control device. If too much, the drive control of the probe cannot keep up with the change in the shape of the object to be measured, and the probe often separates from the object to be measured, or the stylus is often pushed too far into the probe body.
For this reason, it is not possible to accurately specify which side the object to be measured is with respect to the probe, and it becomes impossible to continue the scanning measurement thereafter, and the measurement must be interrupted.
When re-measuring, it is necessary for the operator to set the moving speed of the scanning measurement slower than the previous time. In this way, if the probe is separated from the object to be measured or the stylus is pushed too far, the subsequent measurements cannot be carried out smoothly,
This was a cause of a decrease in the efficiency of scanning measurement and the operating rate of unmanned day and night automatic driving.

The present invention has been made in view of the above circumstances, and an object thereof is to make a probe move away from the object to be measured without being able to follow the shape of the object to be measured and to move the stylus during scanning measurement. Even if the probe is pushed into the probe body beyond the allowable range, the scanning probe can be automatically returned to the normal scanning path without interrupting the measurement and reliable scanning measurement can be performed to the end. It is an object of the present invention to provide a control method that prevents the efficiency of measurement and the operating rate of unmanned day and night automatic operation from decreasing.

[0007]

In order to achieve the above-mentioned object, the present invention maintains the state in which the tip of a stylus displaceably attached to a probe is in constant contact with the surface of an object to be measured. In scanning measurement by a coordinate measuring machine that moves the probe at a predetermined speed in a preprogrammed direction and measures and records the coordinate value of the stylus tip at constant intervals, a certain number of coordinates that are constantly updated to the latest one. A value is stored, and when the displacement amount of the stylus with respect to the probe deviates from a predetermined allowable range, the probe is moved back to the stored constant number of coordinate values, and then the speed is slower than the predetermined speed. It is characterized in that the scanning measurement is restarted.

[0008]

[Operation] Stylus XYZ for the scanning probe body
By constantly monitoring whether or not the magnitude of the vector having the displacement amount of each axis as a component is within the allowable range set as the reference displacement amount, it is possible to confirm whether the scanning measurement is normally performed. If the magnitude of the vector is larger or smaller than the allowable range set for the reference displacement amount, the correct direction to move the probe cannot be specified, and there is a risk that the probe body will collide with the object to be measured. Stop scanning measurement once. The storage circuit in the drive control device always stores the latest measured coordinate values obtained by scanning measurement for a predetermined number of hundreds of points. The probe can be traced back to a fixed position. After this, reliable scanning measurements can be restarted at a slower speed.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An apparatus to which the scanning measurement control method of the present invention is applied will be described below with reference to the drawings. FIG. 1 shows a block configuration of the scanning measuring apparatus. The scanning probe 1 holds a stylus 14 having a spherical probe 15 at its tip so as to be displaceable in a three-dimensional direction with respect to the probe body. Normally, the stylus 14 is operated by a spring or the like, The displacement of each of the XYZ axes is substantially zero, that is, the displacement returns to the vicinity of the center of the displaceable range. This stylus 14
Is detected by an X-axis displacement detector 11, a Y-axis displacement detector 12 and a Z-axis displacement detector 13 built in the probe body, and the addition circuit 22 and the CP in the drive control device 2 are detected.
Input to U21.

On the other hand, the coordinate values of each axis of the coordinate measuring machine 3 for controlling the movement of the probe main body are measured by the X-axis encoder 31, the Y-axis encoder 32 and the Z-axis encoder 33 arranged on each drive axis, and drive control is performed. Adder circuit 22 in device 2
Is input to. The displacement amount of the stylus 14 with respect to the probe main body and the coordinate value of each axis of the coordinate measuring machine 3 are respectively added by an adder circuit 22 in the drive controller 2.
The result 25 is used as the coordinate value of the center of the spherical probe 15. These coordinate values are then input to the CPU 21 and subjected to necessary arithmetic processing, and then a drive command is output to the drive circuit 24 as necessary, and the X-axis drive motor 34 and the Y-axis drive motor 3 are output.
5 and the Z-axis drive motor 36 are driven, stored in the storage circuit 23, or output to the host computer 4 as a measurement result.

Next, the scanning measurement control method will be briefly described. The displacement amount of the stylus 14 with respect to the probe main body and the coordinate value of each axis of the coordinate measuring machine 3 during the scanning measurement control are sampled about 50 to 100 times per second and continuously input to the drive control device 2. The input value is subjected to addition calculation processing in the addition circuit 22, and the value 25 is CP.
Input to U21. Based on the value, the preset moving speed at the time of scanning measurement, and the preset target path for scanning measurement, the CPU determines in which direction and at what speed the scanning probe 1 should be moved next. The obtained result is input to the drive circuit 24 as a drive command. In response to the drive command, the drive circuit 24 drives the X-axis drive motor 34, the Y-axis drive motor 35, and the Z-axis drive motor 36 of the coordinate measuring machine 3 so that the surface of the DUT 5 is always brought into contact with the probe 15. It is possible to measure while scanning. The scanning measurement speed is adjusted by changing the magnitude of acceleration or the time required for acceleration. If the time required for acceleration is fixed, the scanning measurement speed is adjusted according to the magnitude of the acceleration, and conversely, if the acceleration is fixed, it is adjusted according to the time required for acceleration. Alternatively, the scanning measurement speed is adjusted by both the acceleration and the time required for the acceleration.

Next, the scanning measurement control method of the present invention will be described with reference to FIGS. A stylus 15 attached to the scanning probe along the surface of the DUT 5
When the scanning measurement is performed while continuously contacting with each other, if there is a rapid change in the curvature on the scanning measurement trajectory of the measured object as shown in FIG. 2, the tracing stylus 15 is separated from the measured object 5. Therefore, the displacement amount of the stylus 14 with respect to the probe main body of the scanning probe 1 becomes almost zero due to the action of the spring or the like in the probe main body, which exceeds a preset allowable range. As a result, the CPU 21 outputs a drive command to the drive circuit 24 to temporarily stop the drive of the coordinate measuring machine. This is because the displacement of the stylus 14 is out of the allowable range,
This is because, for example, if it becomes zero, it is not possible to identify the direction of the object to be measured with respect to the probe and the moving direction of the probe cannot be specified.

The memory circuit 23 continuously captures the measurement points, that is, the loci of the position coordinate values of the center of the probe 15, and stores the latest predetermined hundreds of points at all times. Then, next in FIG.
As shown in, the reading is performed by going back to the oldest measurement point from the latest measurement point stored in the memory circuit 23, and CP
Enter in U. The CPU controls the movement of the probe along the coordinate values of the point sequence and returns the probe to the position of the oldest measurement point stored in the storage circuit 23.

As a route for returning the probe to the position of the oldest measurement point stored in the memory circuit 23, a route which coincides with the sequence of measurement points, or a route which is away from this route by a predetermined distance from the surface of the object to be measured, etc. Can be considered. Since both routes are obtained based on the measurement point sequence, the probe can be returned safely without colliding with the object to be measured or the like.

Next, as shown in FIG. 4, the scanning measurement speed is made slower than before, and the scanning measurement is performed again. The reason why the tracing stylus 15 separates from the object to be measured 5 is that the response speed of control cannot keep up with the change in the shape of the object to be measured. Therefore, by delaying the scanning measurement speed, the response speed of control is delayed. Will be able to cover. In this way, the tracing stylus 15 can perform the scanning measurement without separating from the DUT 5.

Next, the case of the object to be measured as shown in FIGS. 5 to 7 will be described. In the case of such an object to be measured, the stylus 14 is often pushed too much into the probe body at the portion where the curvature changes abruptly. Therefore, the amount of displacement of the stylus 14 with respect to the probe body of the scanning probe 1 exceeds a preset allowable range. As a result, the CPU 21 outputs a drive command to the drive circuit 24 to temporarily stop the drive of the coordinate measuring machine. This is because the displacement amount of the stylus 14 is out of the allowable range, and it is not known in which direction the object to be measured is accurately located with respect to the probe. If the probe continues moving as it is, the probe body collides with the object to be measured and is damaged. This is because there is a risk of causing a serious accident. The operation after this is as shown in FIGS. 6 and 7, but the content of the control is exactly the same as that described with reference to FIGS.

[0017]

As described above, according to the scanning measuring apparatus to which the present invention is applied, the probe cannot be driven to follow the shape of the measured object during the scanning measurement, and the contact point of the measuring object Even if the stylus is pushed away from the probe body or the stylus is pushed too far into the probe body, the scanning probe can automatically return to the scanning path without interrupting the measurement and reliable scanning measurement can be performed to the end. It is possible to prevent the efficiency and the operating rate of unmanned day and night automatic driving from decreasing.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of a scanning measuring apparatus to which the present invention is applied.

FIG. 2 is an operation explanatory diagram of the stylus in the scanning measurement control according to the present invention.

FIG. 3 is an operation explanatory diagram of the stylus in the scanning measurement control according to the present invention.

FIG. 4 is an operation explanatory view of the stylus in the scanning measurement control according to the present invention.

FIG. 5 is a diagram for explaining the operation of the stylus in the scanning measurement control according to the present invention.

FIG. 6 is an operation explanatory view of the stylus in the scanning measurement control according to the present invention.

FIG. 7 is an operation explanatory diagram of the stylus in the scanning measurement control according to the present invention.

[Explanation of symbols]

 1 Copying probe 2 Drive controller 3 Coordinate measuring machine 4 Host computer system 5 Object to be measured 11 X-axis displacement detector 12 Y-axis displacement detector 13 Z-axis displacement detector 14 Stylus 15 Measuring element 21 CPU 22 Adder circuit 23 Memory Circuit 24 Drive circuit 25 Measured coordinate value 31 X-axis encoder 32 Y-axis encoder 33 Z-axis encoder 34 X-axis drive motor 35 X-axis drive motor 36 X-axis drive motor

Claims (2)

[Claims] 1. A probe is moved at a predetermined speed in a preprogrammed direction while keeping the tip of a stylus movably attached to the probe in contact with the surface of the object to be measured at a constant speed. In scanning measurement with a coordinate measuring machine that measures and records the coordinate value of the stylus tip at time intervals, a certain number of coordinate values that are constantly updated to the latest one are stored, and the probe drive is measured during the process. When it becomes impossible to follow the shape of an object, after moving the probe back to the stored constant number of coordinate values, the scanning measurement is restarted at a speed slower than the predetermined speed. Control method. 2. The device according to claim 1, wherein the displacement amount of the stylus with respect to the probe is constantly monitored, and when the displacement amount is out of a predetermined allowable range, the drive of the probe is made to follow the shape of the object to be measured. A method for controlling scanning measurement, which is characterized in that it is judged that it has disappeared.