JPH0477842B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a scale reading and counting device that electrically divides the graduations of a digital scale into multiple parts, reads them at high speed, and displays them digitally.

In known methods for reading digital scales, the number of divisions of the scale pitch (P) and the reading speed are in a contradictory relationship with each other, and when the number of divisions is increased, the reading speed is inevitably limited. The present invention provides a scale reading/counting device that does not cause reading errors even when the scale is multi-divided and the moving speed is high.

Digital scales originally generate periodic signals at regular pitches and measure the length by counting these signals, but the width of these pitches is limited by mechanical processing techniques. Therefore, in order to obtain the required minimum reading value, it is common practice to divide the pitches using electrical means.

Methods for this division include the zero-cross method, which divides a two-phase signal into four, and the resistance division method, which calculates the two-phase signal using a resistor, electrically converts it into a multi-phase signal, and generates a pulse using each zero-cross method. ,
A phase modulation division method is known in which a carrier wave is phase modulated with a scale signal and the phase difference is counted using a clock pulse. If the number of divisions is relatively small, for example 10 to 20 divisions, all pulses can be counted and displayed on a counter using any of the above methods, but for high precision measurement, the minimum When the reading value is made smaller and the number of divisions is increased, there is a limit to the processing time for division and the response speed of the counter, making it impossible to perform high-speed measurements without counting errors. In order to solve these problems, the applicant has previously proposed
We have applied for a patent regarding the scale reading method with No. 20294. This system is equipped with a precision counter that divides one pitch of the digital scale into multiple units and counts the number of pitches, and a coarse counter that counts the number of pitches. Switch and input the count signal from the counter and store it.
This method outputs and displays the measured distance based on the calculated values of both.

However, in the above invention, the coarse count is 1
Since the count is performed for each pitch, if the display is performed using a Y-base counter, the pitch of the scale will be n of Y.
If it is not a power (for example, for a decimal counter,
10 ¹ = 10, 10 ² = 100, etc.) The disadvantage was that it was not possible to accurately carry up or down the display of the upper digits of the counter.

Generally, scales with a pitch of 10 μm or 20 μm are often used. For example, with a scale of 20 μm pitch, the count value obtained in a coarse system is 2
0, 40, 60, . . . If these counted values are displayed digitally, the display may become unnatural.
That is, in the case of the above scale pitch P, 20 μm
If the diameter is less than 20 μm, it will be counted using the precision system, but if the precision system is moving at a high speed, a counting error will occur, and if the precision system is
It is not possible to correctly count the fraction below, and as a result,
The sum of the coarse count value and the fine count value is unreliable, and in particular, the digit number indicating the unit of 10 μm is also unreliable and may go up or down, which may result in an unnatural display.

The present invention solves this problem and is applicable to most of the pitches of scales used in practical use and the minimum reading values of display counters, so counting in the coarse system is not performed every pitch, Pulses are generated at points where one pitch is divided into several parts every 10 μm,
The object of the present invention is to provide a general-purpose multi-division high-speed scale reading and counting device that counts this. Examples of the present invention will be described below, but the present invention is not limited thereto.

FIG. 1 shows the basic concept of the present invention.
When measuring _length
The number of pulses M ₁ from the coarse dividing point (dividing point every 10 μm)
It is located at. The value of the number of pulses M ₁ can be determined by counting the pulses interpolated within the phase difference corresponding to the displacement using the phase modulation division method described above. Incidentally, when the scale pitch P is phase modulated and multi-divided, for example, divided into m, the displacement per one pulse is P/m.

Read and store this M ₁ at the start of the measurement.
Then, by displacing along the scale, a sin waveform scale signal is detected, and the scale pitch P
A pulse is generated each time the signal passes through a coarse dividing point obtained by dividing the image into N. This number of pulses (n) is counted and stored. At the end point (P _e ) of the measurement, the value M ₂ from the last coarse division point passed through is read using the phase modulation division method, and the measurement is completed, in the same way as at the start point.

From the count values (M ₁ , M ₂ , n) obtained in this measurement, the displacement amount X can be determined by calculating the following equation: X=nP/N+(M ₂ −M ₁ )P/m. however,
If the displacement is at a low speed that the operating speed of the phase modulation dividing circuit and the calculation processing speed described above can sufficiently handle, the calculation described above is not performed only at the end of the measurement, but is performed by following the displacement from time to time. It is also possible to calculate and display using the counts n and M ₂ of the spermatozoa.

An embodiment of the circuit configuration of the present invention is shown in FIG.
Two scale signals sin (2π/P) x, cos (2π/
P) x is added to the refined phase modulation division (m division) circuit. Here, by the phase modulation division method described above, a pulse signal proportional to the amount of displacement within one pitch of the scale signal is output every period of sinωt.
This pulse signal is passed through the next P/m division value counting circuit.
A refresh count is performed every count equivalent to 10 μm.

At the start of measurement, a measurement starting point setting signal is applied externally, and the contents of this P/m division value count are set as M ₁ ,
Stored in _M2 memory circuit. On the other hand, the output of the P/m division value counting circuit enters the carry/down pulse generation circuit, and this carry/down pulse generation circuit is activated every time the P/m division value count reaches a count value equivalent to 10 μm. , generates a pulse signal.

For example, to read 0.1 μm on a 20 μm pitch scale, divide 1 pitch of 20 μm by 200, and
A pulse is generated for each division. This is carried up as the A signal and sent to the carry down signal switching circuit.

Also, the scale signal sin(2π/P) x, cos(2π/
P)x is also added to the coarse division (P/N division) circuit of the coarse system. Here, if the scale pitch P is 20 μm as in the above example, a pulse is generated every 10 μm by dividing 20 μm into two, and sent as a carry/down signal to the pulse signal generation circuit. make a signal. As this coarse division method, any method such as the above-mentioned zero crossing method, resistance division method, phase modulation division method, etc. may be used. moreover,
The signal from the scale also enters the speed detection circuit,
The displacement speed is detected and the signal is sent to the A and B signal switching circuit. If the displacement speed is faster than the predetermined limit, the A and B signal switching circuits are set to pass the B signal, that is, the carry and carry down pulse signals from the coarse division circuit, and that signal is used as the next n pulse. Counted by a counting circuit. In the case of low speed, the precision A signal is similarly counted by the n-pulse counting circuit. In this way, the displacement amount can be determined by guiding the count value M ₁ at the start of measurement and the current count values M ₂ and n to the count calculation display circuit, performing simple addition and subtraction calculations, and displaying the results on the display section. can. However, during high-speed movement, the phase modulation division method does not indicate the correct value as described above, so the precision carry and carry-down pulse signals are unreliable, and as a result, the reading accuracy during high-speed movement is , can only be obtained in units of 10 μm, but this does not pose a practical problem as the counted value due to fine division constantly changes during high-speed movement and is impossible to read visually. Generally, when a scale is moved for measurement, even if it moves at high speed in the middle, it stops or slows down at the starting point and end point of measurement. Even if an error occurs in the carry/download signal A, the precision divided value counting circuit is a refresh counter that detects a phase difference, so when the speed becomes low at the end point,
The correct value can be shown again.

Next, a specific example of count display using the above circuit configuration will be explained. Figure 3 shows the scale pitch.
20μm, minimum reading value is 0.1μm.
P _s and P _e are the starting point and ending point of measurement, respectively. In a precision system, the 20 μm pitch scale signal shown in A in the figure can be divided into 200 parts and counted by a phase modulation division circuit as shown in B to obtain the counted values of M ₁ and M ₂ . In a coarse dividing circuit, the pitch of 20 μm is divided into two, and the carry is carried out every 10 μm.
A downshift pulse signal can be obtained. E indicates a speed detection circuit, and a switching circuit determines whether the carry up or down count signal is the B signal from the precision system or the A signal from the precision system depending on whether the speed is high or low. Therefore, select n pulses, store them, calculate X=nP/N+( _M2 - _M1 )P/m using the counted values of _M1 and _M2 , and calculate the displacement amount X. to be displayed digitally.

As another example, if the scale pitch is 20 μm and the minimum reading value is 0.5 μm, in the fine scale, divide the pitch of 20 μm into 40 to obtain a value of 0.5 μm, and count this, and in the coarse scale, divide the pitch of 20 μm into 40. Divide into 2, 10μm
By generating carry up and down pulses every time, the above scale pitch is 20μm and the minimum reading value is
This can be carried out using the same signal, counting, and arithmetic processing as in the case of 0.1 μm.

Similarly, if the scale pitch is 20 μm and the minimum reading value is 0.5 μm, a precision multi-division circuit will
Divide 25μm into 50 to obtain count values in 0.5μm increments, and in the coarse system, generate a signal by dividing the pitch of 25μm into 5, and output a carry and carry-down pulse every second of this signal. It becomes possible to read by However, in this case, two
It is necessary to add a circuit that outputs one pulse for each count input.

As detailed above, according to the present invention, when the scale pitch is other than 10 μm, for example, 20 μm,
30μm, etc., and accurate counting is possible in at least 10μm units even during high-speed movement, so 10μm
The digitally displayed numbers do not go up or down on the digits indicating the units, and the displacement amounts sequentially displayed during high-speed movement can be prevented from being displayed unnaturally digitally. In this case, there is a risk that the numbers will go up or down due to counting errors in the digits of 1 μm, but when moving at high speed, the precision counts will always fluctuate.
Visual reading is impossible and poses no practical problem.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a reading method using the apparatus of the present invention, FIG. 2 is a block diagram showing an example of the circuit configuration of the present invention, and FIG. 3 is an explanatory diagram of input/output signals in the example of the circuit configuration of the present invention.

Claims (1)

[Claims] 1. A scale signal in which the signal waveform fluctuates by one period for a displacement of scale pitch P {= 10 μm×N (N is an integer of 2 or more)} is read, and the amount of displacement X is digitally displayed. In the scale reading/counting device, means for inputting the scale signal, roughly dividing one period of the scale signal by the N, and outputting a second pulse for each division point; phase modulation dividing means for dividing one period of the scale signal into multiple parts by m{=kN (k is an integer of 2 or more)} and outputting a third pulse at each division point; and counting the third pulse signal. and a first counting means that refreshes the counted value and outputs a first pulse every time the counted value reaches the k value, and a counted value of the counting means at the starting point of displacement measurement.
a storage means for storing M ₁ ; inputting the scale signal to detect a displacement speed; and selecting the first pulse when the detected speed is less than a limit speed that can be counted by the counting means;
means for selecting the second pulse when the speed limit is exceeded; and second counting means for counting the selected first pulse or second pulse and outputting the counted value n. , a displacement amount X based on the count value _M1 stored in the storage means, the current count value _M2 of the first counting means, and the current count value n of the second counting means.
_is calculated by _the following formula: Device.