JPH02248816A - Interpolation processing circuit - Google Patents

Abstract

PURPOSE:To enhance the measuring accuracy of displacement during movement by making the time required in the passage of a signal through a filter constant by mixing the output of a signal means in the mixing ratio corresponding to the output of a carrier signal generating means to reduce an unnecessary higher harmonic component. CONSTITUTION:An encoder 101 outputs two-phase sine wave signals corresponding to the displacement of an object to be measured and modulators 102a, 102b modulate the carrier signal of a carrier generator 103 on the basis of the output of the encoder. Next, a mixer 104 mixes the outputs of the modulators 102a, 102b in the mixing ratio corresponding to the signal of the generator 103 to reduce the unnecessary higher harmonic components contained in said outputs. Further, an unnecessary signal component is removed by a filter 105 and this filter 105 can make the time required in the passage of a signal capable of making an amplitude characteristic gentle through the filter constant over a wide frequency range. By this method, the measuring accuracy of the displacement of the object to be measured during movement is enhanced.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention uses an encoder that outputs multi-phase signals, and can obtain relative position information finer than the pitch of the original encoder through modulation and demodulation to a carrier signal. The present invention relates to an interpolation processing circuit for an electronic scale, and particularly to an interpolation processing circuit that can accurately detect positional information of a moving object while it is moving.

Encoders are widely used as position detection means in conventional technology position control devices.If the pitch of the encoder is sufficiently fine for the positioning accuracy required for the device, the output of the encoder is converted into a two-phase rectangular wave. The position of the positioning target can be detected by combining it with a reversible counter.If even higher position detection accuracy is required, there is a limit to the fineness of the encoder pitch, so the encoder output can be converted into a two-phase A method is used in which the signal is made into a sinusoidal waveform, and the position information below the pitch of the encoder is extracted through the process of phase modulation and nine-phase demodulation.The interpolation processing circuit performs this processing.

An example of the configuration of a conventional interpolation processing circuit is shown in FIG.

301 is an encoder which outputs two-phase sinusoidal signals e, , 6b according to the movement of the object to be measured. 302a
, 302b is a modulator, which modulates the two-phase carrier signals C, , Cb output from the carrier generator 303 with the output of the encoder 301, respectively. 304 is an adder that adds the outputs of the modulators 302a and 302b. Here, a four-quadrant multiplier is used as the modulators 302a and 302b,
A case will be described in which the carrier signals ca and cb are rectangular waves.

When the displacement of the object to be measured from the reference position is represented by X, the output ea, e> of the encoder 301 is expressed as ea-E-cos (2g·x/p) ebmE-sln (2g·x/p). However, p is the pitch of the encoder, and E is the amplitude of the encoder output. The carrier signal output from the carrier generator 303 is a rectangular wave, so when expanded into a Fourier series, it becomes c, -C (cos (2tr ・t) - 1/3co
s C5-2tr-t)+・-・・・-)c, -C-(
s in (2zf - t)+1/3 s in (
3・2x r −t) +・=), so the output S of the adder 304 is 5−E−C・cot(2tr
・t-2g ・x/p)-1/3E-C/cos
(32tr - -2π・x/p) +...becomes a fist, where E and C are encoder outputs, respectively
The amplitude of the carrier signal, t, is time. If we pay attention to the phase of the first term, it can be seen that the carrier signal is phase modulated in accordance with the displacement of the object to be measured. The second term and subsequent terms are unnecessary components generated due to the use of a rectangular wave including a high frequency as a carrier signal. Therefore, if this unnecessary component is removed by the filter 305 and only the first term component is taken out and the phase difference between the first term component and the original carrier signal is detected by the 1 phase difference counter 306, the result will be less than the encoder pitch. The position of the object to be measured can be detected with high accuracy.

The interpolation magnification in this case is determined by the relationship between the frequency of the carrier signal supplied to the multipliers 302a and 302b and the frequency of the clock signal supplied to the phase difference counter 306 that demodulates the phase information of the phase-modulated signal S. (For example, Japanese Patent Publication No. 63-9164.

However, in this publication, a saturable magnetic head is used as the multiplier, a sinusoidally magnetized magnetic scale is used as the encoder, and the multiplication operation is performed using nonlinearity due to the saturation of the magnetic head, so the output of the adder is more unnecessary components appear).

Problems to be Solved by the Invention The difficulty in constructing the above-mentioned conventional interpolation processing circuit lies in the design of the filter. As described above, the filter is provided to remove unnecessary components, but the unnecessary components that cannot be removed by the filter appear as errors that degrade the measurement information of the displacement X. In other words, the filter output in which unnecessary components remain can be rewritten as follows.

smE-C-cos (2tr-L-2z・(X+ε)
/p) Here, C is a measurement error due to unnecessary components.6 Since the detection of the phase difference is performed in synchronization with the carrier signal, the error C becomes a function of the displacement It is difficult to correct.

Therefore, in order to secure the measurement information of the displacement X, it is necessary to sharpen the amplitude characteristics of the filter to increase the ability to remove unnecessary components.

By the way, when measuring the displacement of the object to be measured while it is moving, the displacement X becomes a function of time. At this time, the signal frequency of the component targeted for phase detection of the output S of the adder is shifted from the fundamental frequency f of the carrier signal. For example, when the object to be measured moves at a speed V, x = v - t, so the signal S is 5=E-c-cos (2gf-t-2x-v-t/p
) -E-C-CO3(2K Cr-v/p) ・t)-E
-C-cos (2π(f-Δf)・t), and it can be seen that the frequency of the signal S is shifted from r to (f-Δf). The width Δf by which the 0 frequency shifts is the moving speed V
Therefore, when measuring displacement during movement, it can be seen that the frequency of the signal input to the filter fluctuates up and down around the frequency of the carrier signal.

On the other hand, the phase characteristics of a filter depend on the signal frequency, and the time required for a certain signal to pass through the filter depends on the signal frequency. FIG. 7 shows, as an example, the characteristics of a fifth-order Tievisiev filter.

FIG. 7(a) shows the amplitude characteristics of the filter. The left half is the pass area, and the right half is the cut area. On the other hand, the phase characteristic is as shown in FIG. 7(b), and the time required for a signal to pass through the filter can be expressed as the value obtained by dividing the phase characteristic by the frequency. This is shown in Fig. 7 (C), and if we pay attention to the delay time in the 0 passband, which is expressed as the delay time that occurs when a signal passes through the filter, we can see that this filter changes the delay time depending on the frequency of the signal. You can see that there is a difference.

However, since time information is used to detect displacement information,
'If the time it takes to pass through a filter varies depending on the signal frequency, a signal that has the same time information before passing through the filter will change to a signal that has different time information after passing through the filter. Since the difference in signal frequency is caused by the moving speed of the object to be measured, it occurs that the measured displacement X differs depending on the moving speed of the object to be measured. The most obvious example is when the object to be measured moves toward or away from the reference position, making the measurement appear as if it were at a different position even though it is actually at the same position. be done.

This phenomenon is due to the phase characteristics of the filter, and in order to prevent this, it is necessary to make the time for the signal to pass through the filter constant in the frequency range that the signal can take. However, in order to obtain such a phase characteristic, In this case, the amplitude characteristics must be made gentler, which leads to deterioration of measurement accuracy due to unnecessary signal components.On the other hand, if the amplitude characteristics are made steeper, the phase characteristics deteriorate, and this phenomenon becomes more pronounced. Therefore, when measuring displacement during movement using the conventional method, it has not been possible to achieve both basic measurement accuracy and measurement accuracy during movement.

The present invention has been made in view of the above problems, and by using a mixing means whose mixing ratio can be changed according to the phase of the carrier signal, unnecessary signals at the input of the filter means can be reduced and the phase of the filter means can be reduced. The present invention provides an interpolation processing circuit that optimizes characteristics and can detect displacement information with high accuracy regardless of whether the object to be measured is stationary or moving.

Means for Solving the Problems In order to solve the above problems, the interpolation processing circuit of the present invention has the following features:
An encoder that outputs n-phase (n is an integer of 2 or more) phase signals that differ from each other in accordance with the motion of an object, a carrier signal generation means that outputs n-phase carrier signals that differ from each other in phase, and an output signal of the encoder. n modulating means for modulating the carrier signal output by the carrier signal generating means, a mixing means for mixing the outputs of the n modulating means at a mixing ratio according to the output of the carrier signal generating means, and an output of the mixing means. The device includes filter means for removing harmonics from the filter, and phase information demodulation means for demodulating phase information of the output signal of the filter means.

Operation The present invention can reduce unnecessary components contained in the output of the mixing means with the above configuration. Therefore, even if the filter means has a gentle amplitude characteristic, it is possible to achieve the purpose of removing unnecessary components.

Therefore, it is possible to approximate the phase characteristics of the filter means to such a characteristic that the time required for the signal to pass through the filter means is constant within the frequency range that the signal can take, thereby improving the accuracy of displacement measurement while the object to be measured is moving. be able to.

Embodiment An embodiment of the interpolation processing circuit of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the overall configuration of an embodiment of the interpolation processing circuit of the present invention.

In FIG. 1, 101 is an encoder, which generates two-phase sinusoidal signals ea+eb according to the displacement of the object to be measured.
Output. When the displacement of the object to be measured from the reference position is represented by . However, E is the amplitude of the encoder output, p
is the pitch of the encoder.

102a and 102b are modulators, and carrier generator 1
03 generated carrier signals C,,C.

are modulated by the output of the encoder 101, respectively.

Carrier signals Ca and C output from the carrier generator 103
Since i is a rectangular wave, when expanded into a Fourier series, c, = C-[cos (2zf-t) 1/a cos (3・2rt f-t) +-・
−−−−)c, =C・(s in (2πf−t)+
It is expressed as 1/3 sin (3·2πr-t)+...). However, C is the amplitude of the carrier signal, f is the frequency, and t is the time. The reason why a rectangular wave is used as a carrier signal is that signals having phases different by 90@ from each other can be easily generated in a digital circuit. Further, the configuration of the modulators 10'2a and 102b can be simplified, and the outputs of the modulators 102a and 102b are ma'! ea'Cam mb-eb'cb.

, 104 is a mixer and a modulator 102a.

The output signals ma and m'i of the carrier signal generator 102b are mixed at a mixing ratio corresponding to a signal cs for changing the mixing ratio output from the carrier signal generator 103. The output s3 of the mixer 1'04 can be expressed as follows.

s -Ka-m +Kb, -rn.

S a That is, in the mixer 1-04, the modulator 102-a.

The outputs of 102b are mixed at a ratio of Ka:Kb. The unnecessary signal component contained in the output s3 of the mixer 104 is
This mixing ratio can be reduced by dynamically changing the output of the carrier signal generating means 103, the signal C8, to 0, in other words, the output s3 of the mixer 104 is 3-. 1111e, ・Ka-ca+, e-> ・Kb
-cb, by multiplying the carrier signal by the mixing ratio coefficient, harmonics of the carrier signal that are originally included in the carrier signal and become unnecessary signal components can be reduced.

A filter 105 removes unnecessary signal components included in the output of the mixer 104.In the interpolation processing circuit of the present invention, the mixer 104 can reduce unnecessary signal components. Therefore, compared to conventional filters for similar purposes, it is possible to widen the signal passband and make the cut-off characteristics gentler, making it easier for the signal to be extracted by the filter to pass through this filter. - can be made constant over a wider frequency range. A phase difference force counter 106 detects the displacement of the object to be measured by demodulating the phase information of the signal extracted by the filter.

FIG. 2 is a circuit diagram of an embodiment of the interpolation processing circuit of the present invention.

In FIG. 2, 101 is an optical encoder 0
There is an encoder plate that blocks light between the light emitting element and the light receiving element, and it moves as the object to be measured moves. There are two pairs of light-emitting elements and light-receiving elements, which are mounted at positions spatially shifted by 90'. At the output of the encoder 101, signals ea;"e whose phases are different from each other by 90 degrees are obtained.

102a and 102b are modulators, respectively, and as shown in FIG. If 110 is on the a side, ea, if it is on the b side, -e
, becomes. Since switching of the switch 110 is performed by the carrier signal C3 outputted from the carrier signal generator 103, +1 or -1 is multiplied by the input of the modulator (here, ea) depending on the level of the carrier signal. The same goes for the modulator 102b, and the output m2 is e, d when the switch 111 is on the e side.
If it is on the side, it is 10b.

The switching of the switch 111 at this time is performed by the carrier signal C5 output from the carrier signal generator 103.

104 is a mixer, and a resistor 141 for obtaining the mixing ratio
, 142, 143, and a switch 130 for switching the mixing ratio. A signal C3 that provides timing for switching the mixing ratio is supplied from the carrier signal generator 103. When the switch 130 is on the e side, the output s8 of the mixer 104 is 53=(R2+R3)/Δ−'ma+R1,
/Δ・m.

When the switch is on the r side, s=R3/Δ·ma+(Rl+R2)/Δ'm6. Here, Δ-R1+R2+R3.

Output e8 of encoder 101. If the amplitudes of e and
1:R]+R2.

The signals outputted from the carrier signal generator 103 are shown in FIG. 4, and ca and c are rectangular waves whose phases differ by 90 degrees from each other. The cs supplied to the mixer +04 is a rectangular wave with twice the frequency of C8, C, and its changing point is equidistant from the changing point of C, . Encoder 1 in Fig. 2
FIG. 5 shows the signals of each part when sinusoidal signals ea and eb are obtained from the modulators 102a and 102b. ma, m, are obtained. Mixer 104 whose mixing ratio can be changed by carrier signal C3
A signal ss is obtained at the output of .

Signal S shown in FIG. 6 is a waveform diagram of the signal obtained at the output of the adder in FIG.

Both signal S3 and signal S contain harmonics, but
When the fundamental wave component containing the displacement information of the object to be measured is extracted by a subsequent filter, the signal S can achieve the purpose more easily than the signal S. mixer 10
If the mixing ratio at 4 is selected appropriately, the third
The iPI wave component can be reduced to zero. In this case, the harmonic component closest to the fundamental wave to be removed by the filter is the fifth harmonic, and the passband of the signal in the filter can be widened compared to the signal S including the third harmonic component.

Since the amplitude characteristics of the filter 105 may be gentle, the phase characteristics can be brought close to the desirable characteristic generally called phase linearity.For filters with 0 phase linearity characteristics, the time for the signal to pass through the filter is fixed as described above. Can be kept.

A phase difference counter 106 detects the phase difference between the output of the filter 105 and the signal from the carrier signal generator 103,
A clock for operating the 0 phase difference counter 106 for obtaining displacement information is supplied from the outside.

Note that in the above explanation, the output signals of the encoder 101 and the carrier signal generator 103 were explained as two phases.
It goes without saying that the present invention can be easily extended to cases of two or more phases.

Effects of the Invention As described above, the interpolation processing circuit of the present invention can effectively reduce unnecessary harmonic components by the mixing means that dynamically changes the mixing ratio, and by the phase characteristics of the filter. It is possible to prevent the measurement accuracy from decreasing while the object to be measured is moving.

Therefore, according to the interpolation processing circuit of the present invention, changes in the object to be measured can be accurately measured regardless of whether the object is stationary or moving.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an interpolation processing circuit in an embodiment of the present invention, Fig. 2 is a circuit diagram of an interpolation processing circuit in an embodiment of the invention, and Fig. 3 is a block diagram of a conventional interpolation processing circuit. Fig. 4 is a carry waveform diagram of Fig. 2, Fig. 6 is a waveform diagram of a signal output from the adder, which is a component of the conventional interpolation circuit shown in Fig. 3, and Fig. 7 is FIG. 3 is a characteristic diagram of a fifth-order Tievisiev filter. 101...Encoder, 102a, 102b.
...Modulator, 103...Carrier signal generator, 104...Mixer, 105...
Filter, 106...Phase difference counter.

Claims (2)

[Claims] (1) an encoder that outputs n-phase (n is an integer of 2 or more) phase signals that differ from each other in accordance with the motion of an object; a carrier signal generating means that outputs n-phase carrier signals that differ from each other in phase; n modulation means for modulating the carrier signal output from the carrier signal generation means by an output signal of an encoder; and mixing for mixing the outputs of the n modulation means at a mixing ratio according to the output of the carrier signal generation means. 1. An interpolation processing circuit comprising: a filter means for removing harmonics from the output of the mixing means; and a phase information demodulation means for demodulating phase information of the output signal of the filter means. (2) An encoder that outputs first and second signals whose phases differ by 90 degrees from each other according to the movement of an object, and a carrier signal generating means which outputs first and second carrier signals whose phases differ from each other by 90 degrees. , the first output signal of the carrier signal generating means according to the first output signal of the encoder.
a first modulating means for modulating a carrier signal of the encoder; a second modulating means for modulating a second carrier signal output from the carrier signal generating means by a second output signal of the encoder; mixing means for mixing the output of the second modulating means and the output of the second modulating means at a mixing ratio according to the output of the carrier signal generating means; filter means for removing harmonics from the output of the mixing means; and the filter means. 1. An interpolation processing circuit comprising: phase information demodulation means for demodulating phase information of an output signal.