JPH05346322A - Position detection method - Google Patents

Abstract

PURPOSE:To shorten the processing time for interpolation position detecting process toy storing the interpolation position corresponding to combination of multi-instantaneous values of two-phase sine wave signal as an interpolation position table and calculating the address far referring to it. CONSTITUTION:The interpolation position corresponding to instantaneous values of two-phase sine wave signal detectable is stored in advance as a table, and the reference address of the table is obtained from the instantaneous values of two-phase sine wave signal detected. In short, the A/D conversion data of the instantaneous values of two-phase sine wave signal Ea and Eb detected is read out. Then a reference address X1 is calculated by substituting A/D conversion data (Ea)D and (Eb)D of the instantaneous values of two-phase sine wave signal Ea and Eb for an equation X1=X1+2<8>X(Ea)D+(Eb)rD. An interpolation position theta1 corresponding to the calculated reference address Xi is obtained by reading the interpolation position table. If an off-set value Vof contains error, the amount of it is compensated, before the address Xi is calculated, to calculate the address Xi.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting the position of a moving body by means of a two-phase sine wave signal having a phase difference of 90 ° depending on the movement of the moving body.

[0002]

2. Description of the Related Art FIG. 5 is a schematic view showing an example of a position detecting device for realizing a conventional position detecting method. A gear 2 is attached to a rotating body 1 which is a moving body, for example, a spindle of a machine tool. Magnetic sensors 3a and 3b are arranged at positions separated from the gear 2 by a certain gap. Magnetic sensor 3
In response to the rotation of the gear 2, a and 3b detect two-phase sine wave signals Ea and Eb having phases different from each other by 90 ° as shown in FIG. Each of the comparators 4a and 4b has a two-phase sine wave signal E
The pulses a and Eb are pulsed, and the pulse counter 5 counts each pulse to detect the upper digit portion of the position information, that is, the number N of teeth of the gear 2 that has passed through the magnetic sensors 3a and 3b.

On the other hand, sample / and / hold (S /
H) circuits 6a, 6b and analog / digital (A /
D) The conversion circuits 7a and 7b sample the instantaneous values of the two-phase sine wave signals Ea and Eb, perform A / D conversion, and send them to the interpolation position detector 8. The interpolation position detection unit 8 includes a CPU, a ROM,
An offset value (Vof) _D , which has a RAM or the like and is known in advance from the instantaneous values (Ea) _D and (Eb) _{D of the} two-phase sine wave signal represented by Equations 1 and 2 as shown in FIG. Subtracting them into Equations 3 and 4, and using Equation 5, the lower digit part of the position information,
That is, the position (interpolation position) θ within one tooth of the gear 2 is detected.

[0004]

[Equation 1] (Ea) _D = Vsinθ + (Vof) _D

[Equation 2] (Eb) _D = Vcos θ + (Vof) _D

[Equation 3] (Ea) _D − (Vof) _D = Vsin θ

[Equation 4] (Eb) _D − (Vof) _D = Vcos θ

Equation 5] ^{θ = tan -1 (Vsinθ / Vcosθ} ) = tan -1 {((Ea) D - (Vof) D) / ((Eb) D - (Vof) D)} adder 9 low-order portion The θ and the upper digit portion N are combined and output as a highly accurate position within one rotation of the gear 2. By the way, when detecting the interpolated position θ, t is usually stored in the ROM.
has a table of an ⁻¹ , and ((Ea) _D − (V
of) _D ) / ((Eb) _D − (Vof) _D ), the interpolation position θ is obtained by referring to this table. Since the tan ⁻¹ function is a non-linear function, it is general to use only the portion where the interpolation position θ is 0 ° to 45 ° and not the portion where the interpolation position θ is 45 ° to 90 °.

FIG. 9 is a flow chart for explaining an example of a conventional position detecting method. First, Va = (Ea) _D −
(Vof) _D and Vb = (Eb) _D- (Vof) _D are set (step S1). Then, it is determined whether Va ≧ 0 (step S2), and if Va ≧ 0, it is determined whether Vb ≧ 0 (step S3). If Vb ≧ 0 |
It is determined whether Va | ≦ | Vb | (step S
4), if | Va | ≦ | Vb |, θ ₁ = tan ⁻¹ |
Θ ₁ is calculated from Va | / | Vb | (step S5),
This θ ₁ is set as the interpolation position θ, and all the processes are ended. On the other hand, in step S4 | Va | ≦ | Vb | unless ^{_{θ 2 = tan -1 | Vb |}} / | Va | by seeking theta ₂ (step S6), and a theta interpolation position 90 ° -θ ₂ ( In step S7), all processes are finished.

On the other hand, if Vb ≧ 0 is not satisfied in step S3, it is determined whether or not | Va | ≦ | Vb | (step S8). If not | Va | ≦ | Vb |, θ ₃ = ta
θ ₃ is obtained from n ⁻¹ | Vb | / | Va | (step S9), and 90 ° + θ ₃ is set as the interpolated position θ (step S1).
0), all processing is completed. On the other hand, if | Va | ≦ | Vb | in step S8, θ ₄ = tan ⁻¹ | V
θ ₄ is obtained from a | / | Vb | (step S11),
180 ° −θ ₄ is set as the interpolated position θ (step S12),
All processing ends. On the other hand, in step S2, V
If a ≧ 0, it is determined whether Vb ≧ 0 (step S13), and if not Vb ≧ 0, it is determined whether | Va | ≦ | Vb | (step S14). | Va | ≤ |
Vb | a long if ^{_{θ 5 = tan -1 | Va |}} / | Vb | by seeking theta ₅ (step S15), and the 180 ° + θ ₅ and interpolation position theta (step S16), and ends all processing.

On the other hand, in step S14, | Va | ≦
If not | Vb |, θ ₆ = tan ⁻¹ | Vb | / | Va
Θ ₆ is obtained from | (step S17), 270 ° −θ
₆ is set as the interpolated position θ (step S18), and all the processes are ended. On the other hand, if Vb ≧ 0 in step S13, it is determined whether or not | Va | ≦ | Vb | (step S19). If | Va | ≦ | Vb |, then θ ₇ = ta
θ ₇ is obtained from n ⁻¹ | Vb | / | Va | (step S20), 270 ° + θ ₇ is set as the interpolated position θ (step S21), and all the processes are ended. On the other hand, step S1
If | Va | ≦ | Vb | in 9 then θ ₈ = tan
⁻¹ | Va | / | Vb | is used to obtain θ ₈ (step S
22) 360 ° −θ ₈ is set as the interpolated position θ (step S
23), and ends all processing. That is, as shown in FIG. 8, the interpolation position θ is divided into _eight regions θ _{1 to} θ 8 at 45 ° intervals.
Divide into parts. Then, in each region, tan ⁻¹ so that θi is 0 ° ≦ θi ≦ 45 °
| Va | / | Vb | or tan ⁻¹ | Vb | / | Va |
And then correct the position from the normal origin to obtain the interpolated position θ.

[0008]

In the above-mentioned conventional position detecting method, it is possible to judge the condition in which of the eight areas is included, to calculate | Va | / | Vb | or | Vb | / | Va | , Tan ⁻¹ table, there are many processing steps such as reference, so that there is a problem that processing time becomes long. The present invention has been made under the circumstances described above, and an object of the present invention is to provide a position detection method that requires a short processing time for detecting the interpolation position.

[0009]

The present invention relates to a method for detecting the position of a moving body by means of a two-phase sine wave signal having a 90 ° phase difference from each other according to the movement of the moving body. The purpose is to store an interpolation position corresponding to a combination of each instantaneous value of the two-phase sine wave signal as an interpolation position table, and refer to the interpolation position table by the detected instantaneous value of the two-phase sine wave signal. This is achieved by calculating the address of the and the corresponding interpolation position.

[0010]

According to the present invention, the interpolated position corresponding to the instantaneous value of the detectable two-phase sine wave signal is stored in advance as a table, and the reference address of the table is obtained from the detected instantaneous value of the two-phase sine wave signal. Since it is obtained, the interpolation position can be detected in a short time.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a flow chart for explaining an example of the position detecting method of the present invention. The configuration of the position detecting device that realizes the position detecting method of the present invention is the same as that shown in FIG. 5, and the operation of the interpolating position detecting unit 8 is different as follows. Here, the combination when the instantaneous value (Ea) of the two-phase sine wave signal subjected to A / D conversion and Eb is data of 8 bits is 2 ⁸ × 2 ⁸ or 64K, as shown in FIG. Therefore, the reference address Xi when the interpolated position θi corresponding to these combinations is made into a table can be expressed by Equation 6, and the interpolated position table is as shown in FIG.

Xi = X ₁ +2 ⁸ × (Ea) _D + (Eb) _D where X ₁ is the start address. First, the detected instantaneous values Ea and Eb of the two-phase sine wave signal are A
The / D conversion data is read (step S101). Then, the reference address Xi is calculated by substituting the A / D converted data (Ea) _D and (Eb) _D of the instantaneous values Ea and Eb of the two-phase sine wave signal into the equation 6 (step S102). The interpolated position θi corresponding to the calculated reference address Xi is read from the interpolated position table (step S103), and all the processes are completed.

Further, in the above-mentioned embodiment, the offset value Vof of the two-phase sine wave signal is treated as having no error. However, when there is an error in the offset value Vof, as shown in FIG. Reference address Xi
Before calculating, the offset value errors V ₁ and V ₂ may be corrected by the equations 7 and 8, and the reference address Xi may be calculated by the equation 9 (steps S104 and S105).

[Equation 7] _{(Ea ') D = (Ea} ) D -V 1

[Equation 8] _{(Eb ') D = (Eb} ) D -V 2

Xi = X ₁ +2 ⁸ × (Ea ′) _D + (Eb ′) _{D In the} above description, the resolution of the instantaneous value was described as 8 bits, but the present invention is not limited to this. It is clear that it can be applied even when the resolution is In addition,
The method according to the present invention can be applied to a magnetic or optical rotary encoder or a linear encoder as long as it is a position detecting device using a two-phase sinusoidal signal.

[0013]

As described above, according to the position detecting method of the present invention, the interpolation position can be detected in a short time.
For example, if it is applied to a control device used in a machine tool, control performance can be enhanced and highly accurate machining can be performed.

[Brief description of drawings]

FIG. 1 is a flowchart illustrating an example of a position detection method of the present invention.

FIG. 2 is a flowchart explaining another example of the method of the present invention.

FIG. 3 is a diagram showing an example of a combination of data used in the method of the present invention.

FIG. 4 is a diagram showing an example of an interpolation position table used in the method of the present invention.

FIG. 5 is a schematic diagram showing an example of a position detection device that realizes a conventional position detection method.

6 is a waveform diagram showing an example of a two-phase sine wave signal detected by the position detection device of FIG.

7 is a block diagram showing a detailed example of a main part of the position detection device of FIG.

FIG. 8 is a diagram for explaining an example of a conventional method.

FIG. 9 is a flowchart illustrating an example of a conventional method.

[Explanation of Codes] 8 Interpolation Position Detection Unit

Claims (2)

[Claims] 1. A method for detecting the position of a moving body using two-phase sine wave signals having different 90 ° phases according to the movement of the moving body, which corresponds to a combination of respective instantaneous values of the two-phase sine wave signal. The interpolation position is stored as an interpolation position table, an address for referring to the interpolation position table is calculated from the detected instantaneous value of the two-phase sine wave signal, and the corresponding interpolation position is obtained. Characteristic position detection method. 2. The offset value error of the two-phase sine wave signal is corrected by subtracting it from the instantaneous value of the detected two-phase sine wave signal, and the internal value is corrected by the corrected instantaneous value of the two-phase sine wave signal. The position detecting method according to claim 1, wherein an address for referring to the insertion position table is calculated to obtain a corresponding interpolation position.