JPH0658769A - Signal processing method and displacement detector using method thereof - Google Patents

Abstract

(57) [Abstract] [Purpose] To obtain a signal processing method capable of detecting displacement information of a moving object with high resolution and a displacement detection device using the same. A displacement state of a moving object is detected by a detection means, at least two signals of a sine wave signal and a cosine wave signal are obtained based on the displacement state, and the signals are input to the first signal processing means.
The first signal processing means outputs one of the two signals S
The offset component included in the signal C1 is corrected by calculating the offset component of the other signal C1 using the zero cross point of 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal processing method and a displacement detecting device using the same, and in a displacement detecting device such as a rotary encoder or a linear encoder, appropriately processes a displacement signal relating to a moving object obtained by a detecting means. By doing so, the displacement information of the moving object is detected with high resolution.

[0002]

2. Description of the Related Art Conventionally, in an optical rotary encoder, a linear encoder or the like, two sine waves (2) having different phases relating to displacement information of a moving object are detected by a detecting means.
Phase sine wave signals, in other words, sine wave and cosine wave) are obtained. Then, the displacement amount and the moving direction (displacement direction) of the moving object are detected using the two sine wave signals at this time.

In many cases, conventional encoders generate a plurality of divided pulses having a phase difference corresponding to a division unit from a sine wave signal and a cosine wave signal to improve detection resolution of displacement information regarding a moving object.

FIG. 5 is a principal block diagram showing a signal processing method of two sine wave signals in a conventional encoder.
The signal waveform in each part of the circuit in FIG. 5 is as shown by the solid line in FIG. 6, for example.

In FIG. 5, reference numerals 51 and 52 denote input terminals, which are a sine wave signal C1 (a) and a cosine wave signal S1 (b).
Is entered. That is, the signal b (cosine wave) having a phase difference of 90 degrees is input from the input terminal 52 to the signal a (sine wave) from the input terminal 51. The inverting circuit 53 obtains a signal c obtained by adding a phase difference of 180 degrees to the signal a. These three signals are appropriately weighted and added by resistors or the like, and a sine wave signal of an arbitrary angle is interpolated.

In FIG. 5, all resistors R have the same value, and signals d and e having a phase difference of 45 degrees and 135 degrees are obtained. These signals are converted into rectangular waves by the comparators 54, 55, 56 and 57, and the pulse circuit 58 obtains a two-phase rectangular wave signal having a phase difference of 90 degrees. In this way, a higher resolution signal is obtained from the sine wave signal and the cosine wave signal obtained from the light receiving means.

In addition to this, for example, in Japanese Patent Laid-Open No. 3-68812, a position measurement signal obtained by AD conversion of a two-phase sine wave signal is output as interpolation data in the memory to obtain high resolution. Proposes an interpolation method.

[0008]

In a conventional displacement detecting device such as an encoder or a laser interferometer, the method of interpolating the source signal from the phase information of the two-phase sine wave signal and improving the resolution is to offset the two-phase sine wave signal. If there is a difference in the component or the amplitude, there is a problem that the interpolation accuracy decreases.

FIGS. 7, 8 and 9 show the influence on the division accuracy when the input signal C1 has a swing error in the signal waveform in each part of the circuit of FIG. 5, and the division accuracy when there is a phase difference error. Shows the impact.

In the conventional displacement detecting device, the offset component and the amplitude are adjusted by a variable resistor in an electric circuit.
There is a problem that the offset component and amplitude / phase difference of the signal change due to the change of the laser light amount with time, the fluctuation of the encoder disk, the variation of the slit width within the disk, etc. .

According to the present invention, by appropriately processing a moving signal obtained for a moving object, it is possible to prevent the deterioration of the interpolation accuracy due to the offset or amplitude difference of the two-phase sinusoidal signal, and to obtain the moving information of the moving object with high resolution. An object of the present invention is to provide a signal processing method suitable for an encoder and a laser interference device capable of detecting, and a displacement detection device using the signal processing method.

[0012]

The signal processing method according to the present invention comprises: (a) a displacement detecting device for outputting a two-phase sine wave signal based on the displacement state of a moving object, comparing the two output signals, It is characterized in that an offset component included in at least one output signal is calculated based on the comparison result.

(B) In a displacement detection device which outputs a two-phase sine wave signal based on the displacement state of a moving object, the two output signals are compared, and the amplitudes of the two output signals are compared based on the comparison result. The feature is that the difference is calculated.

(C) In a displacement detecting device which outputs a two-phase sine wave signal based on the displacement state of a moving object, the two output signals are compared, and at least one of the two output signals is based on the comparison result. It is characterized in that the difference between the offset component of one output signal and the amplitude of the two output signals is calculated.

(D) In a displacement detecting device that outputs a two-phase sine wave signal based on the displacement state of a moving object, a formula of the sum product of triangular functions or obtained by detecting the sum and difference of two signals The two signals obtained by are regarded as a new two-phase sine wave signal, the deviation of the phase difference between the two-phase sine waves is corrected, and the amplitude of the two-phase sine wave is also corrected by comparing the new two-phase sine wave. It is characterized by that.

(E) Further, the displacement detecting device of the present invention detects displacement information of a moving object by using the above-mentioned constituent features (a), (b), (c) or (d). It has a feature.

[0017]

1 is a block diagram of the essential parts of a first embodiment showing the basic concept of a signal processing method used in a displacement detecting apparatus of the present invention.

In the figure, T1 is a detecting means, which detects a displacement state such as a moving amount or a moving direction of a moving object (not shown), and a signal corresponding to the displacement state, for example, a sine wave signal C1.
And two signals (two-phase sine wave signals) C1 and S1 having different phases of the cosine wave signal S1 are output.

FIG. 4 is an explanatory diagram of the signals C1 and S1 at this time. Reference numerals 1 and 2 are input terminals for the signals C1 and S1, respectively.

Here, P ₁ and P ₂ are two-phase sine waves C1 and S
1 is the amplitude, θ and Φ are the phases of the signals C1 and S1 at the zero point, and P ₁ cos θ and P ₂ sin Φ are the respective signals C.
Assuming the offset components of S1 and S1, the two signals C1 and
S1 is represented by the following equation.

C1 = P ₁ cos ωt−P ₁ cos θ (1) S1 = P ₂ sin ωt−P ₂ sin Φ (2) The zero points P ₁ and P ₂ in the equation (1) are ωt = ± θ, and by substituting this into (2), S1 (θ) = P ₂ sin θ−P ₂ sin Φ (3) S1 (−θ) = − P ₂ sin θ−P ₂ It becomes sin Φ ‥‥‥‥‥ (4). By adding equations (3) and (4), a value twice the offset component of the signal S1 can be obtained. That is, S1 (θ) + S1 (−θ) = − 2P ₂ sin Φ.

Then, the sample and hold circuits 7 and 8 are used to obtain the signal S1 at the _two zero points P ₁ and P ₂ of the signal C1.
Is sampled and held, and half the difference between the respective sample and hold values is subtracted from the signal S1.
Feedback to. From this, the offset component of the signal S1 is removed.

Similarly, two zero points Q ₁ ,
The signal C1 is sample-held at Q ₂ (ωt = Φ, π + Φ), and 1/1 of the difference between the respective sample-hold values
The offset component of the signal C1 is removed by feeding back to the amplifying means 3 so as to subtract 2 from the signal C1.

In FIG. 1, the signal C1 (S1) is converted into a rectangular wave by the comparator 13 (14), and the rising edge detection means 15 (16) outputs the signal C1 (S1).
A pulse is generated at the zero crossing point at the rising edge of. The sample-hold means 7 (5) samples and holds the signal S1 (C1) using this pulse.

The rising edge detecting means 17 (1
In 8), a pulse is generated at the zero crossing point of the trailing edge of the signal C1 (S1), and the sample hold timing in the sample hold means 8 (6) is given. The output of the sample hold means 7, 8 (5, 6) is added to the adding means 12
By adding in (11), a value twice the offset component of the signal S1 (C1) is obtained. This is divided by two resistors R and fed back to the amplifying means 4 (3) to give a signal S1.
The offset component of (C1) is removed and the output terminal 19 (2
It outputs from 0).

The sample and hold means 7, 8 (5,
6), the adding means 12 (11) constitutes one element of the first signal processing means.

In this embodiment, the offset component of the two-phase sine wave signals C1 and S1 is removed by the above method. At this time, the zero point of both signals C1 and S1 is phase θ = ± π / 2, Φ
= 0, π. By substituting this into the equations (3) and (4) and subtracting, twice the amplitude of the signal S1 is obtained as in the following equation.

S1 (θ) −S1 (−θ) = P ₂ sin π / 2−P ₂ sin (−π / 2) = 2P ₂ By feeding back this amplitude P ₂ to the amplification factor of the amplification means 4, The amplitude of the signal S1 can be controlled to a constant value. The same amplitude control is performed for the signal C1 so that the signals S1 and C1 have the same amplitude to eliminate the influence of the amplitude deviation in the signal interpolation.

In FIG. 1, in the subtracting means 9 (10), the difference between the sample values of the two sample and hold means 5, 6 (7, 8), that is, the difference between the peak values of the signals C1 and S1 is 2P.
1 (2P2) is obtained. By feeding this back to the amplification factor of the amplification means 3 (4), the signals C1 and S1 are
Are controlled to the same amplitude.

The sample and hold means 5, 6 and the subtraction means 9 (10) form one element of the second signal processing means.

In the present embodiment, the movement information is detected with a higher resolution than the movement signal of the moving object detected by the detecting means T1 by using the signal processing method based on each of the above elements.

FIG. 2 is a schematic view of the essential portions of the second embodiment when the digital signal processing means is applied to the signal processing method used in the displacement detecting apparatus of the present invention.

In this embodiment, the AD converter 2 has the same function as the sample and hold means (5, 6, 7, 8) of FIG.
1, 22 and memories 25-28. Source signal C
Since 1 and S1 are digitized by the AD converters 23 and 24, the CPU subtracts the offset value from the source signal, and the amplification of the signals C1 and S1 is matched by the arithmetic processing.

FIG. 3 is a block diagram of the essential parts of a third embodiment in which the signal processing method according to the present invention is combined with a phase shift correcting means utilizing the sum-product method of triangular functions.

The two-phase sine wave signals C1 and S1 output from the detecting means of the displacement detecting device such as an encoder are generally expressed by the following equation.

C1 = P ₁ cos (ωt + θ) −B ₁ (5) S1 = P ₂ sin ωt−B ₂ (6) Here, P ₁ and P ₂ are amplitudes of the two-phase sine wave. , B ₁ and B ₂ are respective offset components, and θ is the deviation of the phase difference of the two-phase sine wave signal from 90 degrees.

Signals C1 given by equations (5) and (6)
Signals C2 and S2 are output from the circuit 37 from S1.
Here, the signals C2 and S2 are C2 = P cos (ωt + θ) (7) S2 = P sinωt (8)

In FIG. 3, the output signal C from the multiplier 35
3 becomes C3 = (C2 + S2) (C2-S2) = C2 ² -S2 ² = P ² cos θ · cos (2ωt + θ) (9).

On the other hand, the output signal S3 from the multiplier 36 becomes S3 = 2C2S2 = P ² sin (2ωt + θ) -P ² cos θ (10). Behind these circuits 35 and 36, a circuit 38 similar to the circuit 37 of this embodiment is connected again. At this time, the signals C4 and S4 output from the circuit 38 are (9) and (10).
From the equation, the following equations (11) and (12) are obtained.

S4 = Pcos (2ωt + θ) (11) C4 = Psin (2ωt + θ) (12) That is, this embodiment is applied to a displacement detection device that outputs a two-phase sine wave signal such as an encoder. Reproducible amplitude difference,
It is possible to obtain a signal in which all the error factors of electrical interpolation due to the shift of the phase difference and the offset are eliminated.

The present invention can be similarly applied to a laser interference device having a plurality of detecting means for detecting displacement information of an object by utilizing light wave interference in addition to the encoder described above.

FIG. 10 is a block diagram of the essential parts of a fourth embodiment in which a signal processing method according to the present invention is combined with a phase shift correcting means utilizing addition and subtraction.

The two-phase sine wave signals C1 and S1 output from the detecting means of the displacement detecting device such as an encoder are generally expressed by the equations (5) and (6).

C1 = P ₁ cos (ωt + θ) + B ₁ (5) S1 = P ₂ sin ωt + B ₂ (6) From the signals C1 and S2 given by the equations (5) and (6), the circuit 37 From the above, two signals C2 and S2 given by the equations (7) and (8) are obtained as in the third embodiment. Here for simplicity S
If the swing of C2 and C2 is 1, C6 and S6 are (13),
The signal is given by the equation (14).

[0045]

[Equation 1] Equations (13) and (14) are 2 sin (θ / 2 + π /
8), 2cos (θ / 2 + π / 8) swing, phase 90 °
It represents the shifted signal.

Reference numeral 39 denotes the shake correction means of the present invention. By using this means, it is possible to obtain a signal with all reproducible shake difference, phase difference shift, and error factors of electrical interpolation due to offset. it can.

[0047]

As described above, according to the present invention, it is possible to prevent the deterioration of the interpolation accuracy due to the offset or the amplitude difference of the two-phase sine wave signal and to detect the displacement information with high accuracy. It is possible to achieve a signal processing method suitable for the above, and a displacement detection device using the same.

[Brief description of drawings]

FIG. 1 is a block diagram of a main part of a first embodiment of a signal processing method used in a displacement detection device of the present invention.

FIG. 2 is a block diagram of a main part of a second embodiment of a signal processing method used in the displacement detection device of the present invention.

FIG. 3 is a block diagram of a main part of a third embodiment of the signal processing method used in the displacement detection device of the present invention.

FIG. 4 is an explanatory diagram of signals C1 and S1 in FIG.

FIG. 5 is a block diagram of a main part of a signal processing method used in a conventional displacement detection device.

6 is an explanatory diagram of signal waveforms in each part of the circuit of FIG.

FIG. 7 is an explanatory diagram of conventional problems.

FIG. 8 is an explanatory diagram of conventional problems.

FIG. 9 is an explanatory diagram of conventional problems.

FIG. 10 is a block diagram of a main part of the fourth embodiment.

[Explanation of symbols]

T1 detection means 1,2 input terminal 3,4 amplification means 5,6,7,8 sample hold means 9,10 subtraction means 11,12 addition means 13,14 comparator 15,16,17,18 pulse generation means 19,20 Output terminal

Claims (6)

[Claims] 1. A displacement detection device that outputs a two-phase sine wave signal based on a displacement state of a moving object, compares the two output signals, and an offset included in at least one output signal based on the comparison result. A signal processing method characterized in that components are calculated. 2. A displacement detection device that outputs a two-phase sine wave signal based on a displacement state of a moving object, compares the two output signals, and based on the comparison result, a difference in amplitude between the two output signals. A signal processing method, characterized in that 3. A displacement detection device that outputs a two-phase sine wave signal based on a displacement state of a moving object, compares the two output signals, and based on the comparison result, at least one of the two output signals. The signal processing method is characterized in that the difference between the offset component of the output signal and the amplitude of the two output signals is calculated. 4. A displacement detection device that outputs a two-phase sinusoidal signal based on the displacement state of a moving object, which is obtained by detecting the sum and difference of two signals, or the sum / product formula of a triangular function. The two signals obtained by the above are regarded as a new two-phase sine wave, the shift of the phase difference between the two-phase sine waves is corrected, and the amplitude of the two-phase sine wave is also corrected by comparing the new two-phase sine wave. And a signal processing method. 5. A signal processing method for outputting a sine wave of three or more phases as an output of the displacement detection device, and processing the signals to convert them into a two-phase sine wave. , 3 or 4 signal processing method. 6. A displacement detecting device, wherein displacement information of the moving object is detected by using the signal processing method according to any one of claims 1 to 5.