JPS5852164B2 - Heikouhenchiyoushingouno Fuheikou Savenkenshiyutsusouchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for detecting the amount of DC deviation of a balanced modulation signal, and particularly to a device for detecting the amount of DC deviation of a balanced modulation signal obtained from a magnetic head. This is suitable for use when detecting an unbalanced component of the signal and adjusting the measuring device based on this detection signal.

A magnetic scale consists of a scale base coated or plated with a magnetic medium, and a magnetic scale having a predetermined wavelength recorded on this magnetic medium.The magnetic scale of this magnetic scale is detected by a magnetic flux responsive magnetic head. It is possible to convert this into an electric signal and obtain an electric signal that is proportional to the amount of movement of the magnetic flux responsive magnetic head relative to the magnetic scale.

FIG. 1 shows a movement measuring device using an upper air magnetic scale to which the present invention can be applied.

In FIG. 1, reference numeral 1 denotes a magnetic scale on which a sine wave signal of a constant wavelength λ (for example, λ=200 μm) is recorded on a strip-shaped or bar-shaped magnetic medium.

Further, 2 is a magneto-electrical converter disposed close to the magnetic scale 1, and is (n+a)λ [where n=o.

1.2. It is composed of two flux-responsive magnetic heads 3 and 4 arranged with an interval of [...].

Excitation windings 3a and 4a and output windings 3b and 4b are wound around the saturable core portions of these magnetic heads 3 and 4, respectively.

Reference numeral 5 denotes an oscillator that generates a sine wave of, for example, 1 h, and the output from this oscillator 5 is reduced to 25 M, for example, by a frequency downgrader 6.
Hz to obtain a signal with an angular frequency of ω0/2. This signal is supplied as an excitation signal to the excitation winding 3a of one of the magnetic heads 3, and the signal with an angular frequency of ω0/2 is The phase is shifted by 7C7 by the phase shifter 7 and then supplied to the excitation winding 4a of the other magnetic head 4.

Excitation signal 11 supplied to the magnetic heads 3 and 4, respectively
°12 is expressed by the following formula.

Therefore, from the output windings 3b and 4b of the magnetic heads 3 and 4, the relative displacement amount X between the magnetic scale 1 and the magnetic heads 3 and 4
The angular frequency ω is twice that of each excitation signal 11 + i2 according to
.

A balanced modulation signal is obtained by modulating a carrier wave having .

This output signal e1. e2 is expressed by the following formula.

The balanced modulation signal e1. e2 is mixed in a mixing circuit 10 via amplifiers 8 and 9, respectively, and then added to the bandpass furnace liquid 1.
1, a phase modulation signal having a phase amount corresponding to the amount of relative displacement and having an angular frequency twice the angular frequency of the excitation signal, that is, an angular frequency ω0, is obtained at its output terminal 12.

This signal e.

is expressed by the following equation. In the measuring device shown in FIG. 1, external magnetic flux from an induction motor of, for example, a machine tool, to which the magnetic scale 1 is attached, magnetization of the cores of the magnetic heads 3 and 4, and the magnetic scale 1 The balanced modulation signal e1. The DC component of e2 is biased.

This bias will cause an error in the output of the measuring device,
In particular, when performing interpolation to measure a length shorter than one wavelength of a magnetic scale, accurate interpolation cannot be performed.

The amount of deviation of this DC component changes each time the magnetic head 3.4, magnetic scale 1, etc. are replaced.

Therefore, conventionally, a compensation circuit such as a resistance bridge is provided in the measuring device, and this compensation circuit allows the magnetic head 3 to
By passing a direct current through the magnetic scale 4 and adjusting its level and polarity, magnetic flux applied from sources other than the magnetic graduations of the magnetic scale 1 described above was canceled out.

However, with this method, adjustments must be made each time the magnetic head, magnetic scale, etc. are changed, which requires considerable effort.

The present invention is for detecting the amount of deviation when the DC component of a balanced modulation signal is deviation.The present invention detects the phase inversion position of the carrier wave of the balanced modulation signal, and synchronizes this detection signal with a signal having a carrier wave frequency. By doing so, a pulse signal that is inverted corresponding to the phase inversion position is obtained, and the average value of this pulse signal is determined.

With this configuration, for example, in a measuring device using a magnetic scale, it is possible to detect the amount of deviation of the DC component of the balanced modulation signal obtained from the magnetic head based on the above-mentioned reason.

Based on this detection signal, a correction signal for correcting the DC component deviation can be obtained.

Further, according to the present invention, it is possible to easily obtain a switching signal that corresponds to the frequency and phase of a carrier wave used when synchronously detecting a balanced modulation signal.

Embodiments of the present invention will be described below with reference to the drawings.

Generally the angular frequency ω.

When performing balanced modulation of a carrier wave having a sine wave as a modulation signal, if the modulation signal includes a DC deviation amount, the waveform of the balanced modulation signal will be as shown in FIG.

In FIG. 2, the carrier wave 21 of the balanced modulation signal 20 is located at the zero crossing point a1, a2...a of its envelope 22.
The phase is inverted by n, and the maximum amplitude E1 of the envelope 22
．． E2. That is, the maximum amplitude of the positive and negative regions of the modulation signal is between the zero cross points a1 to a2, a2 to
It changes alternately from a3 to a3 to a4.

Therefore, the ratio of the DC deviation amount Rv is given by the following equation.

On the other hand, the period T between the above zero crossing points of the envelope 22
a, Tb are also a1-a2, a2-a3, a3-a4...
...'', and the above Rv is this Ta.

It is a function of Tb.

Rv (%) = f (Ta, Tb) In other words, the periods Ta and Tb have sizes that correspond to the amount of DC deviation, and to find this amount of DC deviation, zero cross points al, a2...an All you have to do is find the amount of displacement.

FIG. 3 shows an embodiment of the DC deviation detection device.

This device can also obtain switching signals for synchronous detection depending on the phase and frequency of the carrier wave of the input balanced modulation signal.

In FIG. 3, a balanced modulation signal 20 similar to that shown in FIG. 2 as shown in FIG. 4A is applied to the input terminal 30.

This balanced modulation signal 20 is applied to a limiter amplifier 31, from which a signal 32 synchronized with the carrier wave 21 of the balanced modulation signal 20 as shown in FIG. 4B is obtained.

As shown in the figure, this signal 32 is a signal whose phase is inverted at zero cross points a2 and a3 of the balanced modulation signal 20.

This signal 32 is then applied to the D terminal of a D-type flip-flop 33.

The clock terminal CK of the D-type flip-flop 33 receives the carrier wave 2 from the carrier oscillator 34 as shown in FIG. 4C.
A signal 35 having the same frequency as 1 is added.

Therefore, from the Q terminal of the D-type flip-flop 33, the fourth
As shown in the figure, a pulse signal 36 is obtained which is inverted at a time point substantially corresponding to the zero cross point a2 + 83.

This pulse signal 36 is then applied to a level converter 37, converting the high level portion of this pulse signal 36 to voltage +■.
The low level portion is converted to a voltage -■, resulting in a signal 38 as shown in FIG. 4E.

This signal 38 passes through a low-pass filter 39 as shown in FIG.
A signal 40 as shown in FIG.

This signal 40 has a voltage of ■ as shown in the figure.

The signal 36 or 38 has a magnitude of
represents the average value of

This voltage V. is the zero cross point a1. of the balanced modulation signal 20 shown in FIGS. 2 and 4A. a2. Period Ta, T between ag
The magnitude corresponds to b, that is, the magnitude corresponds to the amount of DC deviation of the balanced modulation signal 20.

FIG. 5 shows the characteristics showing the voltage horse with respect to the difference ratio a-Tb Ta+Tb when the above +■ and -■ are set to +1 [■] and -[■], respectively.

The above output voltage V.

(signal 40) is taken out from output terminal 41.

This output voltage■. Based on this, for example, in the measuring device shown in FIG. 1, it is possible to obtain a correction voltage for canceling the magnetic flux other than the magnetic graduations of the magnetic scale 1.

Also, in a circuit system in which a general balanced modulation signal is transmitted, the balanced modulation signal obtained by modulating the carrier wave with a sine wave is passed through the circuit system, and its output is applied to the input terminal 30 in FIG. It is possible to measure the amount of DC deviation in a circuit system.

Next, in FIG. 3, the output signal 3 of the limiter amplifier 31
2 (FIG. 4B) and the Q terminal (or Wataru terminal) output pulse signal 36 (FIG. 4D) of the D-type flip-flop 33 to the exclusive OR circuit 42, the carrier wave of the balanced modulation signal 20 is A switching signal for synchronous detection whose phase and frequency match those of 21 can be obtained.

That is, by applying the switching signal which is the output of the exclusive OR circuit 42 to the synchronous detection circuit 43, by switching the balanced modulation signal 20 applied from the input terminal 30 to the synchronous detection circuit 43, a demodulated signal is generated from the output terminal 44. can be obtained.

Therefore, a synchronous detection circuit system for a balanced modulation signal can be constructed by the limiter amplifier 31, D-type flip-flop 33, carrier oscillator 34, exclusive OR circuit 42, synchronous detection circuit 43, etc. shown in FIG.

In this case, the balanced modulation signal applied to the input terminal 30 is:
A demodulated signal can be obtained by adding a balanced modulation signal of one carrier, not limited to the one shown in FIG.

The present invention includes a detection means 31 for detecting a phase inversion position of a carrier wave of a balanced modulation signal, an oscillation means 34 for oscillating a signal having a frequency equal to the frequency of the carrier wave, a detection signal obtained from the detection means and the oscillation synchronizing means 33 for obtaining a pulse signal that inverts corresponding to the phase inversion position by synchronizing the signals obtained from the means; and means 37.3 for obtaining a signal indicating the average value of the odor signal.
9, respectively, and the average value is configured to indicate a value corresponding to the unbalanced component of the balanced modulation signal.

Therefore, according to the present invention, it is possible to easily detect the unbalanced component of a balanced modulation signal, and even if there is a phase shift in the carrier wave, the frequency and phase of the carrier wave can be accurately determined by the pulse signal and the limiter output. It is possible to easily obtain a switching signal for synchronous detection that matches .

[Brief explanation of drawings]

Figure 1 is a circuit diagram of a measuring device using a magnetic scale.
FIG. 2 is a waveform diagram of a balanced modulation signal, FIG. 3 is a circuit system diagram showing an embodiment of the present invention, and FIG. 4A. B, C, D, E, and F are waveform diagrams of each part in FIG. 3, and FIG. 5 is a characteristic diagram for explaining level conversion. In the symbols used in the drawings, 20 is a balanced modulation signal, 21 is a carrier wave, 22 is an envelope, 31 is a limiter amplifier, 32 is a limiter output signal, 33 is a D-type flip-flop, 34 is a carrier oscillator, and 35 is a An output signal of a carrier oscillator, 36 an output signal of a D-type flip-flop, 37 a level converter, 39 a low-pass filter, al. a2...an is a zero crossing point.

Claims (1)

[Claims] 1: a detection means for detecting a phase inversion position of a carrier wave of a balanced modulation signal; an oscillation means for oscillating a signal having a frequency equal to the frequency of the carrier wave; and a detection signal obtained from the detection means and a signal obtained from the oscillation means. and means for obtaining a signal indicating an average value of the pulse signal, the average value being the balanced modulation. An unbalanced component detection device for a balanced modulation signal configured to indicate a value corresponding to the unbalanced component of the signal.