JPH07306034A - Shape measuring instrument - Google Patents

Abstract

PURPOSE:To eliminate the scattering in a measurement value speedily without increasing the amount of storage of measurement data by providing a signal smoothing part for smoothing a signal. CONSTITUTION:An output signal (a first signal) from a measurement terminal 14 is smoothed by a first signal smoothing part 34. A second signal from a position measuring instrument 15 corresponding to the relative position of the measurement terminal 14 for a reference point is fetched simultaneously with the first signal and is smoothed by a second signal smoothing part 37. The smoothed first and second signals are stored at a data storage part 33. A stored signal generation part 38 instructs the generation of the stored signal when a measurement point is reached at each of a plurality of measurement points virtually stored along the outer shape of an object to be measured. A shape error calculation part 32 calculates the shape of the object to be measured and a shape error from the smoothed output signal of a measurement terminal 14 at each measurement point stored at the data storage part 33 and the position data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shape measuring device.

[0002]

2. Description of the Related Art FIG. 7 is a block diagram functionally showing an information processing unit of a conventional shape measuring apparatus. The function of the conventional shape measuring apparatus will be described with reference to FIG. The measurement terminal 14 is moved along the measurement surface of the DUT based on the design value. At this time, the position measuring device 15 is used to measure the measuring terminal 1 with respect to the reference point.
4 detects the relative position and outputs a relative position signal. On the other hand, the measurement terminal 14 outputs a signal corresponding to the difference between the design position and the actual position. These output signals are stored in the data storage unit 43 in synchronization with the storage trigger signal generated by the storage signal generation unit 46 at every predetermined time or every distance. Input and storage of data is performed from a predetermined measurement start position to a measurement end position. Thereafter, the shape error calculation unit 42 subtracts the difference obtained by subtracting the “design value of the relative position” from the sum of the relative position signal stored in the data storage unit and the measurement terminal output signal to obtain the shape error of the measured object. Calculate as

[0003]

As described above, in the conventional shape measuring apparatus, the detected position and the output signal of the measuring terminal are input and directly stored in the data storage section. However, the measurement can be performed while moving. Since the measurement was carried out, the measurement was uneven due to the vibration of the mechanism and electric noise. Further, the shape measurement also varies depending on the surface roughness of the object to be measured. Therefore, in the conventional method, in order to remove the variation, data processing is performed on the measurement data after all the measurement data has been acquired.

However, in order to obtain the desired measurement accuracy while eliminating the variation, there is a problem that the amount of measurement data becomes large, the data storage section becomes complicated, and the processing time for eliminating the variation becomes long. It is an object of the present invention to remove variations in measured values at high speed without increasing the storage amount of measured data.

[0005]

According to the present invention, there is provided a measuring terminal for outputting a first signal corresponding to a difference between a design position and an actual position, and the measuring terminal having a design value along a measuring surface of an object to be measured. A moving mechanism for moving based on the position, a position measuring device for outputting a second signal corresponding to the relative position between the reference point and the measuring terminal, and a memory signal generating unit for generating a memory trigger signal at every predetermined time or distance. And a storage unit that stores the first signal and the second signal by the storage trigger signal, and subtract the "design value of the relative position" from the sum of the stored first signal and the second signal. In a shape measuring device comprising a shape error calculating unit that calculates the difference as a shape error of the object to be measured, an input signal generating unit that generates an input trigger signal at predetermined time intervals or distances, and the input trigger signal is synchronized. Then entered A first signal smoothing unit for smoothing one signal and outputting the smoothed first signal to the storage unit in synchronization with the storage trigger signal; and smoothing the second signal input in synchronization with the input trigger signal. And a second signal smoothing section for outputting the smoothed second signal to the storage section in synchronization with the storage trigger signal (claim 1).

The shape measuring apparatus according to claim 1, wherein the first signal smoothing section and the second signal smoothing section accumulate input signals a predetermined number of times and output an average value of the accumulated input signals. (Claim 2). The shape measuring apparatus according to claim 1, wherein the first signal smoothing unit and the second signal smoothing unit are filters that remove noise of a predetermined frequency component (Claim 3).

[0007]

In the present invention, the measuring terminal output signal (first signal) output from the measuring terminal and the relative position signal (second signal) of the measuring terminal with respect to the object to be measured which is detected and output by the position measuring device are respectively provided. Smoothing is performed by the first signal smoothing unit and the second signal smoothing unit, and then stored in the data storage unit (claim 1).

At this time, the number of inputs is set to be larger than the number of times the data is stored. That is, smoothing processing is performed in advance using two or more pieces of input data to form one piece of smooth data (claim 2). Alternatively, smooth data can be obtained by using a filter for removing noise of a predetermined frequency component in the first signal smoothing unit and the second signal smoothing unit (claim 3).

Therefore, it is possible to measure the shape without variation with a smaller data storage amount than in the conventional case where the input data is directly stored without any processing and then smoothed. Therefore, the data storage unit does not become complicated. Further, since the smoothing process is performed during the data input, it does not take a processing time to remove the variation after the data is stored. Hereinafter, the present invention will be described more specifically by way of examples with reference to the drawings, but the present invention is not limited thereto.

[0010]

FIG. 3 shows an embodiment in which the present invention is applied to a precision cutting machine (hereinafter abbreviated as a machine) 1. Processing machine 1
Is a measuring terminal 14 which is provided so as to be movable relative to the object to be measured 13 and detects the relative positional relationship of the object to be measured, and a position measurement for measuring the position of the measuring terminal 14 with reference to a predetermined origin. It has a device 15 (length measuring device 16), an information processing device 10 for processing measurement data, and a moving mechanism 2 for moving the measuring terminal 14 and the measured object (workpiece) 13.

The processing machine 1 includes, as the moving mechanism 2, a Z stage 3 on which a workpiece, which is an object to be measured 13, is placed, a Z support base 4 for movably supporting the Z stage 3, and a Z stage 3. Z stage drive device 5 for moving a required amount
An X stage 7 for supporting the tool base 6 and the measuring terminals 14, an X support base 8 for movably supporting the X stage 7, and an X stage drive device for moving the X stage 7 by a necessary amount. 9 and. In addition, the processing machine 1
It is controlled by the NC controller 11 that controls the operations of the stage driving devices 5 and 9 and the host computer 12 that is connected to the NC controller 11 and the information processing device 10. The host computer 12 creates a control program for the NC controller 11 and various parameters necessary for machining, measurement, etc., outputs the parameters, and takes in the shape measurement information from the information processing device 10 to correct it. A program, parameters, etc. are created and sent to the NC controller 11.

The measuring terminal (measuring probe) 14 is composed of, for example, a differential transformer, and outputs a signal indicating a displacement amount of ± from the center position. In this embodiment, the measuring terminal 14 is of a contact type, but may be of a non-contact type.
The position measuring device 15 is an optical length measuring device 16 in this embodiment.
Is used. That is, the Z stage 3 has a mirror 19
However, the mirror 21 is attached to the X stage 7, and the former is connected to the former through the mirrors 17 and 18,
Light rays are incident on the latter via the mirror 20. The length measuring instrument 16 of this embodiment includes mirrors 19 and 21.
The optical displacement is measured and the coordinate data based on a predetermined origin is output. In this embodiment, what is provided in the processing machine is shared, but it may be provided independently.

FIG. 2 is a block diagram showing the hardware configuration of the information processing apparatus used in this embodiment. The information processing device 10 includes a central processing unit (CPU) 101.
A first memory (ROM) 102 for storing the program of the CPU 101 and each fixed data, and a second memory (R) for storing the data read from the outside, the operation result, etc.
AM) 103 and a host computer interface 104 for connecting an external host computer 12
, The length measuring instrument interface 105 for connecting to the length measuring instrument 16, the NC interface 106, and the measuring terminal 1
4 and the A / D converter 107 which converts the output signal from 4 into a digital signal. In this embodiment, the input device, the display device and the like are provided in the host computer 12. Of course, in the information processing device 10,
The input device and the display device may be connected.

FIG. 1 is a block diagram showing various functions of the information processing apparatus. The information processing device 10 has an external communication unit 31 for exchanging data with the host computer 12. The external communication unit 31 receives the measurement command sent from the host computer 12, and receives the input signal generation unit 3
9 is instructed to fetch the position signal and fetch the output signal from the measuring terminal. The captured output signal (first signal) from the measurement terminal 14 is used as the first signal smoothing unit 34.
Smoothed by.

The second signal corresponding to the relative position of the measuring terminal 14 with respect to the reference point is measured by the measuring terminal 14 under test.
When moving along the outer shape of the first signal, the first signal is taken in at the same time as the first signal and smoothed by the second signal smoothing unit 37. The smoothed first signal and second signal are stored in the data storage unit 33. Memory signal generator 38
For each of the plurality of measurement points virtually arranged along the outer shape of the DUT 13, when the measurement point is reached, the storage signal generation is instructed. The shape error calculator 32 calculates the shape and shape error of the DUT 13 from the smoothed measurement terminal output signal and the position data of each measurement point stored in the data storage 33.

Next, the measurement operation of this embodiment will be described. FIG. 4 shows an outline of the procedure of the measurement operation. This procedure is executed by the host computer 12 and the information processing apparatus 10 that operates accordingly. In this embodiment, the shape of the DUT 13 is measured by obtaining the position of each measurement point of the DUT 13 from the output value of the length measuring device 16 and the output of the measurement terminal 14. Further, in this embodiment, the moving average is used as a method for smoothing the data, but another method may be used. For example, a desired noise component may be removed by selecting a noise frequency with a filter.

First, the host computer 12 instructs the NC controller 11 to move the measuring terminal 14 along the DUT 13 (step 501). When the measurement start point Xs is reached, the relative position of the measurement terminal 14 with respect to the DUT 13 (in this example, the Z-axis direction of the DUT 13 in the present example) is received from the input signal generating unit 39 until the measurement end point Xe. The relative movement position Zin corresponds to the relative movement position Xin of the measurement terminal 14 in the X-axis direction) from the position measuring device, and at the same time, the measurement terminal output voltage Vi from the measurement terminal 14
n is taken in (step 502).

Next, in synchronism with the data capture, the captured data is smoothed. In this example, a moving average process is performed (step 50).
3). There are two types of moving average processing depending on the number of times the data is captured. The first is as follows when the number of times of fetching is N or more: Zk = Zin / NXk = Xin / NVk = Vin / NSz = Sz-ZkN + ZkSx = Sx-XkN + Xk Sv = Sv−VkN + Vk The second case is as follows when the number of times of capturing is less than N times: Zk = Zin / N Xk = Xin / N Vk = Vin / N Sz = Sz + Zk Sx = Sx + Xk Sv = Sv + Vk In the above formula, N is the number of readings in the range of the moving average processing.

Z, X, V with the subscript kN are Zk, X
This is N times before the present of k and Vk. Sz, Sx,
Sv is set to zero at the start of measurement. Table 1 shows numerical data of Z in this example.

[0020]

[Table 1]

Next, when the commanded measurement point is reached, that is, upon receiving a command from the memory signal generator 38, Sz, Sx, Sv are stored in the data memory 13. The memory is repeated at the designated M measurement points. The stored data is array data Szj, Sxj, Svj from 1 to M (step 5).
04). Szj = Sz (j = 1 to M) Sxj = Sx (j = 1 to M) Svj = Sv (j = 1 to M) When the movement is completed, the design value shape and the actual value are stored for the data stored at each measurement point. A shape error Ej which is a difference from the shape is calculated (step 505).

The host computer 12 gives instructions such as the measurement start position Xs, the end position Xe, the number of measurements M, and the range N of moving average processing (designated by the number of input data).
The degree of smoothness varies depending on the value of N. The larger the value of N, the smoother it becomes. The smaller the value of N, the finer the change in shape can be seen. The input signal generator 39 for fetching the data and the memory signal generator 38 for storing the data will be described in detail. When the relative moving speed of the measuring terminals is 12 mm / min, the data is stored. Data acquisition every 10 msec, data storage 100 mse
For each c, the data is taken in every 2 .mu.m, the data is stored every 20 .mu.m, and the data is stored once for every 10 times the data is taken in.

When the shape measurement range is 50 mm, the number of times of data acquisition is 25,000, but the number of stored data is 2500, which is a tenth reduction. The measurement of the shape error by the measuring terminal 14 will be described. Here, the measurement principle when the differential transformer type measurement terminal is used will be described. FIG. 5A shows a state in which the DUT 13 is in the designed shape when the measurement terminal 14 is moved to the design position, that is, the DUT 13 and the measurement terminal 14 are in contact with each other at the design position. Shows. At this time, the measurement terminal is adjusted in advance so that the output voltage of the measurement terminal 14 becomes zero. In other words, the deviation between the center position of the sphere attached to the measuring terminal and the design position of the measuring terminal is zero.

FIG. 5B shows a state in which the object to be measured 13 comes into contact with the design shape position at a position having a shape error when the measuring terminal 14 is moved to the design position. That is, it indicates that the center position of the sphere attached to the measurement terminal is displaced from the design position. On the other hand, since the relationship between the output voltage of the measurement terminal and the center position of the sphere is known in advance as shown in FIG. 6, from the output voltage of the measurement terminal, from the center position of the sphere when the output voltage is zero. The amount of deviation, that is, the amount of deviation of the center position of the sphere from the design position is obtained.

Therefore, the center position of the sphere in contact with the object to be measured can be known from the amount of deviation between the position of the measuring terminal and the center position of the sphere obtained from the output voltage of the measuring terminal. Can be calculated. A method of calculating the shape of the DUT 13 will be described with reference to FIG. Point P is a spherical center position of the measuring terminal 14 read by the position measuring device 15, and is often a position slightly deviated from the design position (due to a positioning error or the like). The actual center position zero point of the sphere attached to the measuring terminal 14 deviates from the point P by the amount of deviation of the sphere obtained from the output voltage of the measuring terminal 14.

The point of intersection of the perpendicular line drawn from the center O of the sphere to the design value shape and the design value shape is defined as R point. Further, on the perpendicular, a point distant from the point O by the radius r of the sphere is designated as a point Q, and an intersection of the straight line passing through the point Q and parallel to the Z axis and the design value shape is designated as a point S. The measurement shape is a shape connecting points Q. Further, the distance between the S point and the Q point becomes the shape error of the S point.

Similarly, P of the measurement path shown in FIG.
Calculated for each measurement point from 1 to PM. At this time, the positional accuracy of the DUT 13 and the measuring terminal 14 is guaranteed by the length measuring instrument 16 used for position control of each stage (the DUT 13 and the measuring terminal 14 are attached respectively).

A specific example of the measurement result is shown in FIG. Comparing these before and after performing the smoothing process, the portion T that was not visible due to noise before the smoothing process is apparent after the smoothing process. Further, another specific example of the measurement result is shown in FIGS. 11, 12, and 13. The circles in the figure represent each measurement point. The horizontal axis represents the position of the measurement point in the X-axis direction, and the vertical axis represents the position in the Z-axis direction.

FIG. 11 shows the measured value as it is taken and the value after the smoothing process. No processing before smoothing, so ± 5μ at peak
There is a variation of m. This is the value after smoothing processing when the moving average is taken 10 times, and the peak is ±
The variation is reduced to 0.5 μm. In the present embodiment, the value after the smoothing process is taken in and stored once in 10 times, so the value of the stored data is ± 0.5 μm.
It is a smooth value within m.

On the other hand, in the conventional apparatus, since the acquisition itself is once in 10 times with respect to the result of FIG. 11, the acquired result is as shown in FIG. 12 or FIG. 13 depending on the acquisition timing, and the measurement result depends on the acquisition timing. to differ greatly. In addition, the data is ± 5μ as shown in the result of FIG.
There are cases in which there are variations in m, and there are cases in which it becomes zero as in the result of FIG.

[0031]

According to the present invention, noise-free shape measurement can be performed without increasing the amount of stored data, so that the data storage unit is not complicated and the noise removal calculation processing time can be shortened. High-precision, high-speed shape measurement is possible.

[Brief description of drawings]

FIG. 1 is a block diagram of functions of the information processing apparatus according to the present embodiment.

FIG. 2 is a hardware configuration diagram of the information processing apparatus of the present embodiment.

FIG. 3 is a conceptual diagram of an embodiment according to the present invention.

FIG. 4 is a flowchart of the measurement procedure of this embodiment.

FIG. 5 is a diagram showing a positional relationship between the measuring terminal and the object to be measured in the present embodiment.

FIG. 6 is a graph showing the relationship between the ball center of the measurement terminal and the terminal output of this embodiment.

FIG. 7 is a block diagram of functions of an information processing device according to a conventional technique.

FIG. 8 is a diagram showing the relationship between the ball center of the measuring terminal and the object to be measured.

FIG. 9 is a diagram showing a measurement path.

FIG. 10 is a graph showing a specific example of the measurement result of this example.

FIG. 11 is a graph showing a specific example of the measurement result of this example.

FIG. 12 is a graph showing an example of measurement results obtained by a conventional device.

FIG. 13 is a graph showing an example of measurement results obtained by the conventional device.

[Explanation of symbols]

1: Processing machine 2: Movement mechanism 3: Z stage 4: Z support stand 5: Z stage drive device 6: Tool stand 7: X stage 8: X support stand 9: X stage drive device 10: Information processing device 11: NC Controller 12: Host computer 13: Object to be measured 14: Measuring terminal 15: Position measuring device 16: Optical length measuring device 17-21: Mirror 22: Spindle 31, 41: External communication part 32, 42: Shape error calculating part 33, 43: data storage unit 34: measurement terminal output signal (first signal) smoothing unit 37: position signal (second signal) smoothing unit 38, 46: storage signal generating unit 39: input signal generating unit 101: central processing unit (CPU) ) 102: first memory 103: second memory 104, 105: interface 106: NC interface 10 : A / D converter or

Claims (3)

[Claims] 1. A measuring terminal that outputs a first signal corresponding to a difference between a design position and an actual position, and a moving mechanism that moves the measuring terminal along a measurement surface of an object to be measured based on a design value. The second corresponding to the relative position between the reference point and the measurement terminal
A position measuring device that outputs a signal, a storage signal generation unit that generates a storage trigger signal at predetermined time intervals or distances, and a storage unit that stores the first signal and the second signal by the storage trigger signal. A shape error calculating unit that calculates a difference obtained by subtracting the “design value of the relative position” from the stored sum of the first signal and the second signal as a shape error of the object to be measured. An input signal generator that generates an input trigger signal at predetermined time intervals or distances, smoothes the first signal input in synchronization with the input trigger signal, and smoothes the synchronization signal in synchronization with the storage trigger signal. Smoothing the first signal smoothing unit for outputting the first signal to the storage unit and the second signal input in synchronization with the input trigger signal, and smoothing in synchronization with the storage trigger signal. And a second signal smoothing unit that outputs the second signal described above to a storage unit. 2. The first signal smoothing unit and the second signal smoothing unit accumulate an input signal a predetermined number of times,
The shape measuring apparatus according to claim 1, which is an averaging unit that outputs an average value of the accumulated input signals. 3. The shape measuring apparatus according to claim 1, wherein the first signal smoothing unit and the second signal smoothing unit are filters that remove noise of a predetermined frequency component.