JPH0445049B2 - - Google Patents

Description

[Detailed description of the invention]

Technical field The present invention is based on a sinθ signal with a 90° phase difference and a cosθ signal with a different phase difference of 90°.
The present invention relates to improvements in encoder-type angle and length measurement circuits that measure angle or length using signals. Prior Art and its Problems Normally, encoder-type measuring or length measuring devices use two sinusoidal signals, a sin θ signal and a cos θ signal, with 90° different phases in order to discriminate directions and improve the number of divisions. Figure 3 a and b are waveforms showing sin θ signal and cos θ signal, sin θ signal a and cos θ signal b.
are binarized by a comparator or the like as shown in FIG. 3c and d, and the binarized signals c and d are
It is converted into a direction-discriminated pulse signal (this is called a 4-division pulse) by a discrimination pulse generation circuit or the like as shown in FIG. The amount of movement (this is the angle measurement value or length measurement value) is determined, and angle measurement and length measurement work is performed. In addition, in such a 4-division pulse counting method, for example, if the encoder is created so that one pulse period is 10 μm, in the case of N counts, the measurement accuracy of the measured value corresponding to the movement amount of N × 10 μm However, in order to obtain higher resolution, various methods have been proposed in which the pulse interval is further divided by interpolation processing. There is a method to obtain the interpolation angle by taking the ratio with the value of θ=tan ^-1 sinθ/cosθ. FIG. 4 is a block diagram showing a 4-division pulse counting type angle measurement and length measurement circuit equipped with the interpolation processing circuit. The sin θ signal a and the cos θ signal b output from the elements etc. are binarized via comparators 1 and 2 using, for example, the reference zero as a threshold, and the binarized waveform signals (c, d signal) is the discrimination pulse generation circuit 3
4-division pulse signal whose direction is discriminated by
The four-division pulse signal is added to the up terminal or down terminal of the counter 4 and counted to calculate the major scale value. On the other hand, the sin θ signal and cos θ signal are digitally converted by A/D converters 5 and 6, and the A/D converters 5 and 6 convert them into digital signals.
The outputs from the D converters 5 and 6 are divided into sinθ/cosθ values by the division unit 7, and the tan ^-1 calculation unit 8
By obtaining tan ^-1 , θ is obtained, and in the angle converter 9, for example, if one pulse period is 10 μm, the interpolated value as a small scale value can be obtained by obtaining 10 μm × θ/90°. . The interpolated value as the small scale value and the large scale value as the count value of the 4-division pulse are combined in the synthesis unit 10 and displayed on the display unit 11, thereby obtaining a high-resolution measurement value. . By the way, in the above angle measurement/length measurement circuit, in order to calculate the major scale value, the sin θ signal and the cos θ signal must first be converted into binary waveform signals by comparators 1 and 2. First, in order to calculate the interpolated value, the A/D converters 5 and 6 must first convert the sin θ signal and the cos θ signal into digital signals, so the comparators 1 and 2 must convert the sin θ signal and the cos θ signal into digital signals. If there is a deviation between the binary waveform signal and the digital signal converted by the A/D converters 5 and 6, for example in the reference zero point of the comparator and the A/D converter, the display will There is a possibility that a phenomenon in which the measured value displayed at 11 jumps may occur. FIG. 5 is a diagram for explaining the phenomenon of skipping, and a in FIG. 5 is a four-division pulse output from the discrimination pulse generation circuit 3, and b in FIG. 5 is a diagram for explaining the phenomenon of skipping. As mentioned above, the ideal interpolated value output from 9 is the waveform signal that is binarized by the comparators 1 and 2 and converted by the A/D converters 5 and 6. If there is a deviation between the reference zero points, etc. between the digital signal and the digital signal, the zero point of the interpolated value output from the angle converter 9 will be the pulse generation point of the 4-division pulse, as shown in Fig. 5c. In this case, the measured values synthesized in the synthesis section 10 are, for example, considering the part I in FIG. 5...18μm 19μm 10μm
A composite value of 21 μm and 22 μm is obtained, resulting in a phenomenon of numerical jumps. Various proposals have been made in the past as countermeasures against such jumps, but all of them have the drawback of complicated processing. Purpose The present invention has been made in view of these problems, and includes a four-way interpolation processing circuit that reduces the phenomenon of numerical jumps using a simple processing circuit.
The present invention aims to provide an angle measurement/length measurement circuit using a divided pulse counting method. Configuration of Embodiment 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 an encoder type angle measurement/length measurement circuit according to the present invention. Blocks similar to those in the conventional example are designated by the same reference numerals and a description thereof will be omitted. As is clear from FIG. 1, the difference in structure between the conventional example and this embodiment is that the present embodiment has comparators 1 and 2
The binarized sin θ signal and cos θ signal are taken in, and the positive and negative states of the sin θ signal and cos θ signal are determined, and the sin θ signal and cos θ signal are determined as shown in Table 1 below.

From the positive and negative relationships in [Table], as shown in Figure 2 a,
A quadrant generation unit 13 that determines which quadrant the four-divided pulse is currently in among the four-divided pulses divided into the respective quadrants, and transmits the determination result to the synthesis unit 10, the division unit 7, and tan ^-1 . Input the sinθ/cosθ value, that is, tanθ, output from the division unit 7, which is provided between the calculating unit 8 and schematically shown in FIG. 2b, and calculate the absolute value of tanθ, which is schematically shown in FIG. 2c. The difference lies in that an absolute value processing section 12 for outputting is newly provided. Effects of the Embodiment Next, the effects of the above embodiment will be explained using Fig. 2 and Table 2 below.

[Table] When sinθ and cosθ signals are input, the sinθ signal and cosθ
The signal is input to comparators 1 and 2 to be binarized to calculate a major scale value, and is also input to A/D converters 5 and 6 to be digitally converted to obtain an interpolated value. The waveform signal binarized by the comparators 1 and 2 and the A/D converter 5,
6, there is a timing shift in the initial operation of the digital signal converted by Assuming that there is a deviation in the relative relationship with a), the synthesis section 10 takes in information from the absolute value processing section 12 and the quadrant generation section 13 and performs an addition process as described below. The synthesis unit 10 checks the absolute value of tanθ output from the absolute value processing unit 12, and selects a value predetermined based on the absolute value of tanθ as an interpolation value. Here, the range of the absolute value of tanθ from which a predetermined interpolated value is selected will be explained. First, 10 μm×tan ⁻¹ |tanθ|/90° is calculated. Here, the reason why the numerator in the above formula is tan ⁻¹ |tanθ| is to set the value of this numerator within the range of 0°≦θ≦90°. Then, the value calculated by the above formula is within the range of "9" or more and less than "10", that is, 81°<tan ^-1 |tanθ|<
Find the value of θ that falls within the range of 90°, and calculate the value of θ,
81°<θ<99°, 261°<θ<289°, 441°<θ<459°
,
……, (180n+81)°＜θ＜(180n+99)°,…
...[However, θ=(180n+90)° is excluded. n=0,
1, 2, ...], let A be the absolute value of tanθ. Similarly, the value calculated by the above formula is within the range of "0" or more and less than "1", that is, 0°≦tan ^-1 |tanθ|<9°
Find the value of θ that falls within the range of , and find the value of θ, 0°≦
9°, 171°<θ<189°, 351°<θ<369°,...
(180m−9)°<θ<(180m+9)°, ...[However, within the range of m=1, 2, 3, ...]
Let B be the absolute value of tanθ. Then, tanθ output from the absolute value processing unit 12
As shown in Table 2, which shows the relationship between the absolute value of and the corresponding interpolated value assigned by the synthesis unit 10, the quadrant of the quadrant pulse is such that the absolute value of tanθ is within the range of value B. When it is, set the interpolated value to "0μm"
If the absolute value of tanθ is within the range of value A in the quadrant of the 4-part pulse, the interpolated value is set to 9 μm.
It is said that Also, when the absolute value of tanθ is within the range of value A in the quadrant of the 4-division pulse, the interpolated value is set to 0 μ
m", and when the absolute value of tan θ is within the range of value B in the quadrant of the 4-part pulse, the interpolated value is assigned as "9 μm". Therefore, in the synthesis section 10, the value of the absolute value of tanθ outputted from the absolute value processing section 12 and inputted to the synthesis section 10 via the tan ^-1 calculation section 8 and the angle conversion section 9 is read and the resulting value is calculated as the above value. If the value is A or B, the interpolated value is calculated as shown in Table 2 based on the information input from the quadrant generation unit 13, and the measurement is performed by combining the interpolated value and the major scale value. It calculates the value. In this way, such a composite value, that is, a measured value, for example, in the case shown in FIG.
The changes are limited to 31 μm, μm, and the large jumps of 19 μm, 10 μm, and 21 μm, as in the conventional example, are eliminated. Note that the areas within the dotted line in FIG. 1 are generally processed by a microcomputer or the like. Effects The present invention is configured as described above, and by adding a very simple processing circuit, the measurement value generated when combining the large scale by the 4-division pulse and the interpolated value by the interpolation process is improved. It is possible to prevent large jumps, and as a result, measurement accuracy is improved, which has an extremely large practical effect.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of an encoder type angle measurement/length measurement circuit according to the present invention, and FIG.
The figure shows the signals in the block of figure 1;
FIG. 3 is a diagram showing signals in the block of FIG. 4, FIG. 4 is a block diagram showing a conventional example, and FIG. 5 is a diagram explaining the phenomenon of skipping. 1, 2: Comparator, 3: Discrimination pulse generation circuit, 4: Counter, 5, 6: A/D converter, 7:
Division section, 8: tan ^-1 calculation section, 9: Angle conversion section, 1
0: synthesis section, 11: display section, 12: absolute value processing section, 13: quadrant generation section.

Claims (1)

[Claims] 1. A light beam output from a light receiving element that receives a light beam that has passed through a detection element that constitutes a part of the encoder device.
Binarize the sinθ signal and cosθ signal, convert the binarized signal into a 4-division pulse signal using a discrimination pulse generation circuit, etc., and calculate the major scale value by counting the pulse signal with a counter. With,
The above sin θ signal and cos θ signal are digitally converted, and the digital signals are interpolated in the division section, tan ^-1 calculation section, and angle conversion section to calculate the interpolated value, and the above major scale value and interpolated value are In the angle measurement/length measurement circuit that obtains a measured value by combining in a synthesis section, the binarized sin θ signal and cos θ signal are taken in, and the sin θ signal and cos θ signal are determined to be positive or negative,
From the positive and negative relationship between the sinθ signal and cosθ signal, the above 4.
a quadrant generation unit that determines the quadrant of the divided pulse signal and transmits the determination result to the synthesis unit; the division unit; and tan ^-1;
Provided between the calculation section and output from the division section
An absolute value processing section that outputs the absolute value of the tanθ value is provided, and the interpolation value is selected in the synthesis section based on the absolute value output from the absolute value processing section and the determination result of the quadrant generation section. An encoder type angle measurement/length measurement circuit characterized in that a measured value is obtained by combining the interpolated value with a large scale value.