JP2532371B2 - Displacement measurement circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a phase modulation method in which a relative displacement amount between a magnetic scale and a magnetic head is electrically read and the displacement is obtained as a phase displacement of a carrier wave. The present invention relates to a displacement amount measuring circuit that measures a specific position of a phase modulation signal without measuring the periodic phase of the signal.

[Prior Art] As a method of electrically measuring a relative displacement amount between relatively moving objects in order to measure a length or an angle, a reference scale and a displacement amount sensor are provided to measure the displacement amount. There are optical scales, inductosyns, magnetic scales, and the like in the phase modulation type displacement amount conversion device for electrically reading the displacement as the phase displacement of the carrier wave.

[Problems to be Solved by the Invention] An interpolation processing method in a phase modulation type displacement amount measuring apparatus using a magnetic scale, which has been conventionally performed, sequentially measures the phases of the phase modulation signals and detects the adjacent measurement samples. The displacement amount was obtained by comparing and determining the phases.
However, this method requires a period of one cycle of the maximum phase modulation signal to measure the phase, (T is time, λ is recording wavelength, x is relative displacement, S is x _{n + 1} −x _n
The opposite sign of is shown. ) By performing the processes (1) and (2), the relative displacement amount x _t of the magnetic flux response head between the sample time t and t + 1 is obtained, and this process is sequentially performed. Is obtained, the relative movement amount of the magnetic scale and the magnetic flux response type head from the sampling period t = 0 to t = n is obtained, and this value is sent to the display device to display the movement amount. , (2), (3) processing time is lost.

In order to solve this, in the conventional method, the phase measurement is performed every cycle of the phase modulation signal, and the signal processing is performed in the next cycle. However, since the signal processing cycle is not measured, an error occurs when there is a speed fluctuation, which is not suitable for high-accuracy measurement. In order to avoid this, there is no choice but to have two systems of a gate circuit and a counter circuit, which complicates the circuit processing, and basically, from the principle of measuring a phase, a frequency divider, a phase comparator, and a gate that obtain a reference signal. It had to have a circuit and a counter circuit, which was a factor that complicates the circuit.

In addition, a method of measuring the period of the phase modulation signal is also known in the displacement measuring instrument of the phase modulation signal method, but this also
For the above reasons, it is not suitable for highly accurate displacement measurement, and has a drawback that the circuit becomes complicated.

[Means for Solving Problems] The present invention has been made to solve the above problems, and an object thereof is to perform phase measurement and period measurement in a displacement amount measuring method of a phase modulation method. The present invention provides a displacement amount measuring circuit for highly accurate measurement with a simple circuit configuration by measuring the time t without performing. That is, by detecting the relative displacement between moving objects,
The conversion means for converting this into a phase modulated signal, the reference signal generating means for obtaining a signal N times the frequency of the phase modulated signal, the N-advance timekeeping circuit for timing with the signal of this reference signal generating means, and the value of this circuit A storage circuit for storing, a storage signal generation circuit for giving a fixed position of the phase modulation signal as a storage signal to the storage circuit, a means for inputting the output of the storage circuit and the output of the storage signal generation circuit, and performing arithmetic processing, respectively. The value of the N-advance timekeeping circuit is stored in the storage circuit by the signal of the signal generation circuit in each cycle of the phase modulation signal, and the storage circuit in the cycle n in which the content of the storage circuit is taken into the arithmetic processing means in accordance with the command of the storage signal. Value of t _n and value of next cycle n + 1 value
When t _{n + 1} and the maximum displacement amount from a certain cycle n to n + 1 of the next cycle is ± N / 2 or less, when | t _{n + 1} −t _n | ≦ N / 2, When | t _{n + 1} −t _n |> N / 2, x _n = ΣΔx _n Δx _n is shown in equation (15-1) The coefficient of is attached, but in general the value is chosen to be 1. The relative displacement amount x _n is obtained by performing the discriminating calculation process.

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

In FIG. 1, the magnetic scale 20 is a rod-shaped magnetic medium on which graduations of a constant wavelength λ are recorded. This magnetic scale
20, the magnetic flux response type heads 21 and 22 are spaced (n ± 1/4) λ
(However, n is 0, 1, 2, 3 ...) In such a magnetic scale unit, the excitation winding of the magnetic flux response head 21 oscillates N times the carrier angular frequency ω ₀ of the phase modulation signal (N is the number of interpolations for interpolating the wavelength λ of the magnetic scale). Divider circuit 24 that divides the signal from oscillator 23 into N / 2
Then, the excitation signal is supplied through the power amplifier 25.
On the other hand, a signal is supplied to a power amplifier 27 that supplies an excitation signal to the magnetic flux response head 22 through a phase shifter 26 that shifts the phase by π / 4. In this way, the signal from the magnetic flux response type head 21, And a signal from the magnetic flux response type head 22, Is obtained. A ₁ and A ₂ are constants, t is time, λ is the recording wavelength, and x is the relative displacement between the magnetic scale and the magnetic head. The output voltages e ₁ and e ₂ of the above equations (4) and (5) are mixed in the mixed amplifier circuit 28 in the state of the amplitude A ₁ = A ₂ = A, and then the carrier angle is calculated from the output of the mixed amplifier circuit 28. After passing through the bandpass filter 29 that extracts only the fundamental angular frequency of the frequency ω ₀ , from Equation (4) and Equation (5), Is obtained. This signal is pulsed by the pulsing circuit 30. Up to here is the displacement conversion device using the magnetic scale. The output signal of this device is a pulse waveform e ₄ obtained by pulsing the phase modulation signal shown in equation (6).

Next, processing of the above signals will be described. First, the output (e ₅ ) of the oscillator 23 having the angular frequency of Nω ₀ is input to the clock terminal of the N-ary [N is an interpolation number (integer)] counter 31. This N-ary counter 31 is 1 of the carrier wave of the phase modulation frequency.
It becomes a counter that cycles once in a cycle. Further, the output of the N-ary counter is led to a temporary storage circuit 32 including a latch circuit and the like. The storage circuit 32 is output e ₄ of pulsing circuit to the LOAD terminal to store the output of the N-ary counter 31 at the rising or falling or the like fixed position output e ₄ of pulsing circuit 30 is derived. The pulsed signal e ₄ is used as an input signal to the LOAD terminal so that the storage operation to the storage circuit 32 can be performed stably.
It is also possible to input the output (e ₆ ) of the synchronizing circuit 33 for synchronously differentiating with the clock of the N-ary counter 31, that is, the output of the oscillator 23, and this is more preferable.

Next, the output of the memory circuit 32 is input to the arithmetic processing unit 34. The arithmetic processing unit 34 may be a microcomputer or a dedicated processing unit for processing the output of the storage circuit 32 described later. Further, the output of the synchronizing circuit 33 is connected to the arithmetic processing unit 34 so that the arithmetic processing unit 34 can be informed that the first output of the N-ary counter 31 has been stored. Further, the output of the arithmetic processing unit 34 is connected to a display unit 35 for displaying the processing result.

The operation of the above circuit configuration will be described with reference to FIGS. 1 and 2. Angular frequency of carrier wave ω
_{Since 0} = 2πf ₀ , the phase modulation signal is And However, f ₀ is the frequency of the carrier wave, the time when e becomes e _n is t _n , the magnetic scale 20 at that time and the magnetic flux response type head 21,
If the relative displacement of 22 is x _n , The output when the output e becomes the same as e _n in the next cycle is e _{n + 1}
And

Where e _n = e _{n + 1} The phase angle θ when the phase modulation signal of Expression (8) becomes e _n is generally 2πk + θ, where k is an integer and 0 ≦ θ <2π.

Further, the phase angle θ when the phase modulation signal of the equation (9) becomes e _{n + 1} = e _n is generally 2π (k + 1) + θ, where k is an integer and 0 ≦ θ <2π.

Therefore, Is represented by

(11)-(10), The period of the phase-modulated signal of e ₃ is T, the carrier (angular frequency ω ₀ )
Is T ₀ and the relative displacement between time t _n and t _{n + 1} is Δx, t _{n + 1} + t _n is t _{n + 1} −t _n = T = T ₀ + ΔT (12− 1) ΔT is the amount of change in the period T of the phase modulation signal from T ₀ x _{n + 1} −x _n = Δx (12-2) Substituting equations (12-1) and (12-2) into equation (12), Solving the above equation for Δx, From the above equation (13), the relative displacement amount at t _{n + 1} from t _n delta
x is the difference ΔT between the period of the phase modulation signal and the period of the carrier wave at that time, that is, ΔT = T− according to the equation (12-1).
It is only necessary to find T ₀ . The N-ary counter circuit 31 uses as a count clock N times the carrier frequency f ₀ (N is
It is an N-ary counter circuit which is counted by Nf ₀ , which is an interpolation number in 1, 2, 3, .... In the time chart of FIG. 3, it is assumed that the constant value of the phase modulation signal, for example, the value of the N-ary counter circuit 31 is stored in the storage circuit 32 at the rising point (a) of the pulsed phase modulation signal. If the value is t _n , t _n is N quantized by the frequency Nf ₀ as described above.
This is the value of the decimal counter circuit 31. That is, the value of the N-ary counter circuit 31 is ₀ , 1, 2, ... By the count clock Nf _0.
Counting in the order of N-1 and taking a value that returns to 0 again,
It is one of the values 0, 1, 2, ... N-1.

Next, when the value of the N-adic timing circuit 31 is stored at the next position _where e takes the same value as t _n , that is, the rising (b) position of the next cycle, the value t _{n + 1} is t _{n + 1} = It is represented by t _n + (T ₀ + ΔT). That is, the period T ₀ + Δ from the time interval t _n to t _{n + 1}
It is the sum of T _n and the time in (a). (T ₀ , T
_{n is} also quantized by Nf ₀ ).

By the way, t _{n + 1} is N quantized by Nf ₀ as described above.
Since it is measured by the decimal counter circuit 31, it cannot be larger than T ₀ and actually has the following value.

t _{n + 1} = {t _n + (T ₀ −ΔT)} MOD T ₀ = t _n + ΔT _n {t _n + (T ₀ −ΔT)} MOD T ₀ is the value of {} divided by T _0. Too much.

Therefore, when the difference between t _{n + 1} and t _n is obtained, t _{n + 1} −t _n = ΔT (14) From this equation (14), t _n and t of the N-ary counter circuit 31 are calculated.
By obtaining the difference of _{n + 1} , the difference ΔT _n with the period T ₀ of the carrier signal can be obtained. The value (13) can be used to determine the relative amount of movement [Delta] x _n in the time from t _n to t _{n + 1} by substituting the equation.

Since t _{n + 1} , t _n is the value of the N-ary counter which is counted by the count clock Nf ₀ , t _{n + 1} , t _n must be multiplied by the period 1 / Nf ₀ of the count lock for the true time. .

Therefore, equation 15 is Generally, the value of λ / N should be set to 1 in order to simplify the calculation.

In the case of, Δx = − (t _{n + 1} −t _n ) ... (15-2) Next, a concrete numerical value is put in the above circuit configuration for further explanation. The carrier frequency is f ₀ = 10 kHz, the recording wavelength λ = 200 μm. ,
Interpolation number N = 200.

Equation (15-1) is Since t _{n + 1} and t _n are values of the counter circuit, Δx _n = − (t _{n + 1} −t ₁ ).

The N-ary counter circuit 31 is a 200-ary counter circuit that counts with a clock of Nf ₀ = 2 MHz. In addition, the synchronous differentiation circuit 3
From 3 at the rising edge of the phase modulation signal by the 2 MHz synchronizing signal, a signal of 2 MHz for one pulse is pulsed and output (e ₆ ).

The 200-base counter circuit 31 starts counting from 0, 1, 2, 3, ...
After increasing to 199, when it exceeds 199, it returns to 0 and repeats thereafter. This cycle is 100 μsec with carrier frequency f ₀ = 10 kHz
be equivalent to. Under such circumstances, when the output (e ₆ ) of the synchronous differentiating circuit is supplied to the memory circuit 32 at a certain time, the output of the counter circuit 31 is taken into the memory circuit 32 at that time. If the relative movement amount of the magnetic scale 20 and the magnetic flux response type heads 21 and 22 is 0, that is, if the period of the phase modulation signal does not change, this value t _n will be the same value at the next timing. If the relative displacement between the magnetic scale 20 and the magnetic flux response type heads 21 and 22 is not 0, the value t _{n + 1} captured at the next storage timing is different from t _n . The value of t _n becomes smaller. That is, when t _{n + 1} <t _n , this direction is the positive direction. Conversely, if it moves in the opposite direction, t _{n + 1} > t _n , and this direction is negative. For example, assuming that t ₁ has a value of 10, if there is a relative displacement of 1 μm in each positive direction in each measurement synchronization, then t ₁ = 10 t ₂ = 9 t ₃ = 8 t ₄ = 7, At this time, the arithmetic processing device, for example, the microcomputer may perform the following processing. First, when t ₁ is stored, a storage command is transmitted to the microcomputer, so the value is stored in the A register of the microcomputer. Next, when t ₂ is stored, the value t ₂ is stored in the B register. B when the value is entered in the A and B registers
-Process A, and put the result in the C register. Further, in order to integrate the value of the C register, it is added to the contents of the D register containing the result of integration. That is C +
Perform D → D. Further, the contents of the B register are transferred to the A register for the next processing. When the processing is completed up to this point, the system waits until a signal that the next value has been stored arrives, and if the signal is input, the next value t ₃ is placed in the B register and the above processing is performed. If the processing is successively performed in this manner, the magnetic scale 20 is stored in the D register of the integration result.
And the relative displacement amount of the magnetic flux response type heads 21 and 22 can be obtained. If necessary, the value in the D register can be displayed on the display 35.
If sent to, the relative displacement amount is displayed.

What must be noted in the processing of B-A above is the processing when the value of t _n sequentially increases or decreases and then exceeds 0 such as 199 to 0 or 0 to 199.
For example, t ₁ = 197 t ₂ = 198 Δx ₂ = 198-197 = 1 t ₃ = 199 Δx ₃ = 199-198 = 1 t ₄ = 0 Δx ₄ = 0-199 = −199 t ₅ = 1 Δx ₅ = 1−0 = 1 In this example, Δx ₄ = −199 μm, resulting in an error. This is because the value of the N-ary counter circuit 31 measures the value of T ₄ = {T ₄ + (T ₀ −ΔT)} MOD T ₀ and overflow cannot be detected. In order to eliminate such inconvenience, the following processing may be performed. Now, _{if the} amount of movement in the time interval from t _n to t _{n + 1} is within ± N / 2, then | t _{n + 1} −t _n | ≦ N / 2 When | t _{n + 1} −t _n |> N / 2, However, S is the opposite sign of t _{n + 1} −t _n , that is, And is than may be, is x _n that sequentially accumulating the Delta] t _n obtained by the above, the current position, and x _n = ΣΔx _n.

In the displacement amount measuring circuit of the above-described embodiment, a read amount memory is used for the arithmetic processing unit, and the displacement amount measuring circuit can be configured to obtain the displacement amount by combining t _n and t _{n + 1} . Further, in the displacement amount measuring circuit of the above embodiment, by using the read-only memory and the digital comparator in the arithmetic processing unit, it is possible to detect the displacement amount with high resolution.

Furthermore, in the displacement amount measuring circuit of the above embodiment, t _n and
It is also possible to record a special pattern at a combination point where t _{n + 1} cannot be taken and detect the displacement amount as an overspeed.

[Advantages of the Invention] The present invention relates to a displacement amount measuring method using a phase modulation method,
It is possible to eliminate the inconvenience caused by the overflow of the counter for measuring the phase, and to perform highly accurate measurement with a simple circuit configuration.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention,
FIG. 2 is a timing chart of signals of the present invention, and FIG.
FIG. 4 is a timing chart for explaining a part of the operation of the present invention, and FIG. 4 is a block diagram of a conventional example. 20 …… Magnetic scale, 21,22 …… Flux response type head, 31
... N-ary counter circuit, 32 ... memory circuit, 33 ... memory signal generation circuit, 34 ... arithmetic processing circuit.

Claims (4)

(57) [Claims] [Claim 1] by detecting the relative displacement, synchronized with the input signal to the converting means and said converting means for converting a phase-modulated signal of a frequency f _0, and N times the frequency f ₀ of the phase modulation signal detecting a predetermined position of the storage circuit and a phase modulation signal for storing the value of the N-ary counter circuit and the N-ary counter circuit for counting the signal of the reference signal generating means of the frequency of the reference signal generating means and nf ₀ to obtain a signal of nf ₀ And a storage signal generating circuit for giving a storage signal to the storage circuit for storing the value of the N-ary counter circuit at that time, and an arithmetic processing means for inputting the output of the storage circuit and the output of the storage signal generation circuit. The value of the N-ary counter circuit is stored by the signal of the storage signal generation circuit for each cycle of the phase modulation signal, and the content of the storage circuit is taken into the arithmetic processing means by the command of the storage signal and the value t of the storage circuit in a certain cycle n. _n N the value of the next cycle n + 1 and t _{n + 1}
To n + 1, the maximum displacement is ± N / 2, and | t _{n + 1} −t _n | ≦ N / 2 Δx _n = t _{n + 1} −t _n | t _{n + 1} −t _n |> When N / 2, Δx _n = S {N− | t _{n + 1} −t _n |} x _n = ΣΔx _n A displacement amount measuring circuit, characterized in that the displacement amount x _n is obtained by performing the discrimination calculation process. 2. The displacement amount measuring circuit according to claim 1, wherein the displacement amount measuring circuit uses a read-only memory as an arithmetic processing unit to obtain the displacement amount by a combination of t _n and t _{n + 1} . 3. The displacement amount measuring circuit according to claim 1, wherein the displacement amount measuring circuit uses a read-only memory and a digital comparator in the arithmetic processing unit to detect the displacement amount with high resolution. 4. A displacement amount measuring circuit, wherein a special pattern is recorded at a combinational portion where t _n and t _{n + 1} cannot be taken, and the displacement amount is detected as a speed overrun.
The displacement amount measuring circuit described in the item.