JPH0794962B2 - Absolute position detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an absolute position detection device for detecting an absolute position in a linear scale used for a positioning device or the like.

(Technical Background of the Invention and Problems Thereof) Various means are considered for the position detection unit, which is the most important element as a positioning system used for machine tools and the like. Among them, the linear scale that has been conventionally used is generally one that uses the principle of inductosyn.

FIG. 4 shows the principle structure of this linear scale. The scale 2 on the fixed side and the movable slider 3
When two wavy conductors (hereinafter, referred to as coils) are parallelly opposed to each other with a minute gap therebetween and a current is applied to the scale 2 from the AC power supply 1, a voltage is induced in the slider 3 by an electromagnetic induction action. Now, when the current Y1 flows through the scale 2, a magnetic flux FF is generated, so that the current Y2 is induced in the slider 3. The linear scale detects the position by extracting the change in the induced voltage. The magnitude of this induced voltage changes depending on the degree of electromagnetic coupling between the scale 2 and the slider 3, that is, the relative position.

5 (A) to 5 (F) and FIG. 6 show the relationship between the relative position of the scale 2 and the slider 3 and the degree of electromagnetic coupling, respectively. FIG. 5A shows a scale 2 composed of coils arranged at a pitch interval P, and FIG. 5B shows a slider 3 similarly composed of coils arranged at a pitch interval P. Then, FIGS. 6B to 6F show a process in which the slider 3 moves, and FIG. 6 shows the relationship between the moved position X and the electromagnetic coupling degree by the induced voltage IV. Here, the induced voltage IV becomes maximum at a position where the coils of the scale 2 and the slider 3 overlap each other ((B) in the same figure), and gradually decreases as the slider 3 is moved in parallel to 1/4 of the conductor pitch P. At a position deviated by a certain amount ((C) in the figure), the magnetic fluxes cancel each other and the induced voltage IV becomes zero. Furthermore, if you translate it
The P / 2 pitch (Fig. (D)) has the maximum value of the reverse characteristic compared to the case of 0 pitch in Fig. 5 (B), and the P / 3/4 pitch (Fig. (E)) has 0 and pitch P. At the moved position ((F) in the figure), the polarity becomes maximum, that is, the same state as in the case of 0 pitch. In this way, the change of the induced voltage IV draws one cycle along with the parallel movement of the slider 3 within one pitch P of the coil, and becomes as shown in FIG. 6, and the same pattern is repeated in the next one cycle. Become. The marks (B) to (F) in FIG. 6 correspond to the states in FIGS. 5 (B) to (F), respectively.

FIG. 7 shows the coil arrangement of the scale 2 and the slider 3. The slider 3 is provided with two coils, a Sin output coil 5 and a Cos output coil 6, which are offset by 1/4 pitch. When AC power source 1 is applied to
The coils 5 and 6 of the slider 3 which are deviated from each other by 1/4 pitch have an electromagnetic coupling degree of Sin and Cos as the slider 3 moves.
Two induced voltages that change in a curve are output. Therefore, since the change in the induced voltage indicating the degree of electromagnetic coupling has a unique relationship with the relative position between the two coils 5 and 6, the moving position of the slider 3 can be measured by detecting the induced voltage.

However, the above-mentioned detection device can measure the absolute position only within the range of one pitch, and the absolute position cannot be detected over the large movement range of the slider 3,
It has the drawback that it can only be detected as an incremental position.

(Object of the Invention) The present invention has been made under the circumstances described above.
An object of the present invention is to provide an absolute position detection device capable of detecting an absolute position over a wide range by varying the pitch of coils wound on a scale by a predetermined width and providing a plurality of sliders. is there.

(Summary of the Invention) The present invention is a wavy, fixed-side scale provided with a first conductor in which a pitch interval (l) of one cycle of the wave gradually increases by a predetermined width (Δl), and the first conductor. The output part for outputting a current to the first conductor has a pitch interval (l) of one cycle of the first conductor as a cycle, and is 9 l / 4 close to the fixed side scale and parallel to the major axis direction. Two movable sliders that are provided with two wavy second conductors that are displaced from each other, and that are arranged at a distance of 4l + 6Δl so as to be close to the fixed scale and parallel to the major axis direction. A phase detector for detecting the phase of the output voltage induced from the second conductor by the first conductor in correspondence with the moving distance (X) of the slider with respect to the fixed scale; and the fixed scale. Absolute position between the slider and the slider (P _n1 )
Is expressed by the following three equations (a, b, c), Where n is the number of pitches passing through the slider, S1 and S2 are the values of the phase detection signal from the phase detection unit, and the values of the phase detection signal (S1, S2) are S1> S2, the value of the phase detection signal ( S1 and S2) are substituted into the above equations (a) and (b), and when S1 <S2, the values (S1, S2) of the phase detection signal are substituted into the above equations (a) and (c) and The number of pitches (n) satisfying the two equations at the same time is obtained, and the number of pitches (n) is substituted into the equation (a) to obtain the absolute position (P _n1 ). is there.

(Embodiment of the Invention) FIG. 1 shows an embodiment of the present invention.
The coil is wound a plurality of times, and the pitch interval is sequentially changed in increments Δl, that is, the pitch interval is l,
l + Δl, l + 2 · Δl, ..., l + n · Δl. Further, in the present invention, the two sliders 3A and
3B are parallel to the scale 2A and face each other with a minute gap therebetween, the slider 3A is provided with a Sin output coil 5A and a Cos output coil 6A, and the slider 3B is provided with a Sin output coil 5B and a Cos output coil 6B. It is constructed integrally. These Sin output coils 5A and 5B and Cos output coils 6A and 6B
Is the initial pitch interval l of the coil whose pitch interval is scale 2A, and as described in FIG.
The arrangement is such that the Sin signal and the Cos signal are output according to the movement of 3B. Further, the length of the scale 2A is longer than the entire length of the sliders 3A and 3B.
The slider 3A is arranged such that its sin output coil 5A is aligned with one side end of the coil of the scale 2A having the smallest pitch l, and in the slider 3B, its Sin output coil 5B is the coil of the scale 2A. Are arranged in such a relationship that the pitch interval among them matches the start point of (l + 4 · Δl). When an alternating current is supplied from the excitation power supply 7 to the coil of the scale 2A, the moving distance X of the sliders 3A and 3B
Accordingly, the Sin output coil 5A of the slider 3A and the Cos output coil 6A outputs the Sin signal and the Cos signal as outputs V _1a and V _2a , respectively, and the Sin output coil 5 of the slider 3B
The Sin signal and the Cos signal are output as the outputs V _1b and V _2b of the B and Cos output coils 6B, respectively.

In such a configuration, first, the relationship between the output voltages V _1a , V _1b , V _2a and V _2b with respect to the moving distance X of the sliders 3A and 3B is analyzed. The output voltages output from the Sin coils 5A and 5B and the Cos output coils 6A and 6B corresponding to the moving distance X of the sliders 3A and 3B are proportional to Sin X and Cos X, respectively, as described in FIG. It becomes a voltage. Now, assuming that the moving distances of the sliders 3A and 3B from the reference position O are X1 and X2, the exciting power supply 7 is A sin ωt, and the magnetic coupling coefficients between the scale 2A and the sliders 3A and 3B are K1 and K2, respectively. The following equation holds.

These equations (1) to (4) are phase-detected, and the movement distance X1 and
When the output voltages corresponding to X2 are DS1 and DS2, the relationship between the output voltages DS1 and DS2 with respect to the movement distance X is shown in FIG. 3 and explained. Before that, the phase detection method will be described.
It will be described with reference to the drawings.

FIG. 2 shows the block configuration of the phase detection device. By applying the excitation power supply 7 to the coil of the scale 2A,
Output voltages V _1a , V _1b and V _2a , V _2b are induced from the Sin output coils 5A, 5B and Cos output coils 6A, 6B of the sliders 3A and 3B, respectively. Of these output voltages, V _1a and V _2a are input to the digital converter 10A, and the output voltages V _1b and V _2b are input to the digital converter 10B (the content of the configuration is the same as 10A and therefore omitted here). Here, the digital converter 10A will be described. The output voltages V _1a and V _2a are input to the multipliers 13A and 13B, respectively, and the Cos conversion means 11
And the output voltage of the Sin conversion means 12 are respectively multiplied.
Then, the output voltages V10 and V11 of the multipliers 13A and 13B are respectively input to the adder 14 and added, and the output voltage V12 of the adder 14 is A from the excitation power supply 7 in the phase detector 15.
・ The phase is detected based on Sinωt, and the phase detection voltage V13
Is output. The phase detection voltage V13 is integrated by the integrator 16 and then converted into a pulse train in the voltage controlled oscillator 17. This pulse train that has been converted into a pulse train is input to the up / down counter 18, which outputs the output voltage φ and the digital signal DS1 of the output voltage φ. And
The output voltage φ is input to the Cos conversion means 11 and the Sin conversion means 12, converted to Cosφ and Sinφ, respectively, and input to the multipliers 13A and 13B. On the other hand, the output voltages V _1b and V _2b are input to the digital converter 10B, subjected to the same processing as described above, and output the digital signal DS2. The digital signals DS1 and DS2 obtained as described above are input to the arithmetic processing unit 20 including a computer or the like and subjected to predetermined arithmetic processing.

In such a configuration, the operation will be analyzed. Here, the magnetic coupling coefficient K1 in the above equations (1) to (4)
Since K2 and K2 are the same in principle, K1 = K2 = K ... (5) will be explained below.

The output voltages V _1a and V _2a of the slider 3A are respectively calculated by the multiplier 13
Since it is multiplied by Cosφ and Sinφ in A and 13B, Becomes Then, the addition output V12 of the adder 14 for adding the multiplication results of the multipliers 13A and 13B is Becomes Further, when the phase detection unit 15 detects the phase by the reference signal A · Sinωt from the excitation power supply, the phase detection output V13 is Becomes Here, the multiplier loop is formed so that V13 in the equation (9) becomes zero. That is, The loop is formed so that Therefore, the moving distance
The value of X1 is obtained by an equation using the values of φ and n, and at the same time, the value of φ becomes a digital signal DS1 and is input to the arithmetic processing unit 20. Similarly, the moving distance X2 of the slider 3B
The digital signal DS2 related to is input to the arithmetic processing unit 20.

Since the digital signals DS1 and DS2 obtained here are values within the range of 1 pitch of the scale 2A, the digital signals DS1 and X2 corresponding to these X1 and X2 are described below.
A procedure for obtaining an absolute value by two signals of 1 and DS2 will be described with reference to FIG.

The value of digital signal DS1 at this time is S1
, Then Therefore, when the number of pitches is n as a general expression, the moving distance Pn1 is as follows.

Similarly, if the value of the digital signal DS2 is S2, then the moving distance P _n1 is as follows as a general expression.

Here, since Pn1 in the equations (12) and (13) is essentially the same, Becomes By the way, the expression (14) is obtained from the general expression in the state like the moving distance PS1 in FIG. 3, but in reality, there may be the state of the positional relationship like PS2. If the values of the digital signals DS1 and DS2 at this time are S3 and S4, respectively, equation (12) becomes equation (15) and equation (13) becomes (16).
Equation (14) corresponds to equation (17), and the following equation is obtained.

Then, the pitch number n is obtained by the equation (14) or the equation (17), and as the calculation method, for example, the successive substitution method is used. That is, the digital converter 10A
And the value of the phase detection voltage obtained from 10B (at this stage, S
1 and S2 or S3 and S4) and known quantities l and Δl and a tentative pitch number n, for example, the minimum pitch number 0, either of (14) or (17) On the other hand (for example, by substituting into the equation (14), it is checked whether the equation (14) is satisfied. If the equation (14) is not satisfied, the next provisional pitch number n, For example, by substituting the second smallest pitch number 1 into the equation (14) in the same manner and checking whether or not the equation is satisfied, the pitch number n is sequentially increased until the equation (14) is satisfied. Continuing the process of substituting into equation (14), find the number of pitches n when the equation holds, and substitute this number of pitches into equation (12) or equation (13) to obtain the scale 2A.
It is possible to detect the absolute value of the movement amount X of. On the other hand, if the equation does not hold even if the number of pitches determined in advance by the scale 2A, that is, any pitch number n up to the maximum pitch number n is substituted into the equation (14), the same processing as described above is performed. Continue until the other equation (Equation (17) in this example) is satisfied, find the pitch number n when the equation is satisfied, and substitute this pitch number n into Equation (15) or Equation (16). By doing so, the absolute value of the movement amount X of the scale 2A can be detected. Here, the reason why the number of pitches n (n is an integer of 0 or more) obtained by the successive substitution method is determined only by one of the equations (14) and (17) will be described. Since the coefficient of the first term on the right side of the equation (14) is greater than 1, and the second term on the right side is positive, S1> S2 (where S1, S2 ≧ 0). Also, (1
Since the second term on the right side of equation (7) is positive, S3 <S4 (where S
3, S4 ≧ 0). That is, equations (14) and (17) are
Since the application is uniquely determined by the magnitude of the phase detection voltage values S1 and S2, S3 and S4 obtained from the digital converters 10A and 10B, the pitch number n obtained by the successive substitution method is the equation (14) or (17). Only one of the expressions can be set. Note that these calculations are performed in the calculation processing section 20.

In order to facilitate understanding of the present invention, in the example of FIG. 1, the scale 2A and the sliders 3A and 3B are arranged so that their coil ends match as the start positions, but they may be arranged at any position. The above analysis results are applicable. Also, the digital signals DS1 and DS2 were analyzed here with the maximum value set to 999, but this is the number of divisions (1000 divisions) of 1 cycle (1 pitch), and can be arbitrarily selected, and 3 sliders can be selected. It is possible to further improve the accuracy by using the above.

(Effect of the Invention) As described above, according to the present invention, the absolute position can be detected within the entire length-measuring range by simply changing the scale coil pitch of the generally used linear scale, which is extremely simple. An absolute position detection device with good performance can be realized.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing an example of a phase detector, FIG. 3 is an operation analysis diagram of the present invention, and FIG. 4 is a linear diagram which is the basis of the present invention. 5A to 5F and 6 are views for explaining the degree of electromagnetic coupling of a linear scale, and FIG.
The figure shows the coil arrangement of the scale and the slider. 1 ... AC power supply, 2,2A ... Scale, 3,3A, 3B ... Slider, 5,5A, 5B ... Sin output coil, 6,6A, 6B ... Cos output coil, 7 ... Excitation power supply, 10A, 10B ... Digital converter, 11 ... Cos conversion means, 12 ... Sin conversion means, 13A,
13B: Multiplier, 14: Adder, 15: Phase detector, 16
...... Integrator, 17 ...... Voltage controlled oscillator, 18 ...... Up-down counter, 20 ...... Arithmetic processing unit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nominomi Hirota 2068-3 Ooka, Numazu-shi, Shizuoka Toshiba Machine Co., Ltd. Numazu Works (72) Inventor Kimio Suzuki 2068-3 Ooka, Numazu, Shizuoka Toshiba Machine Co., Ltd. Numazu Works (56) References JP-A-61-134604 (JP, A)

Claims (1)

[Claims] 1. A fixed-side scale having a wavy shape, in which a pitch interval (l) of one cycle of the wave gradually increases by a predetermined width (Δl), and a current is supplied to the first conductor. The output unit for outputting and the first one-cycle pitch interval (l) of the first conductor are set as a period, and are shifted by 9l / 4 so as to be close to the fixed scale and parallel to the major axis direction. Two movable conductors, each of which is provided with two corrugated second conductors, are arranged so as to be close to the fixed scale and parallel to the major axis direction by being displaced by 4l + 6Δl; A phase detector that detects the phase of the output voltage induced from the second conductor by the first conductor corresponding to the moving distance (X) of the slider with respect to the side scale; the fixed-side scale and the slider. The absolute position (P _n1 ) between , b, c), Where n is the number of pitches passing through the slider, S1 and S2 are the values of the phase detection signal from the phase detection unit, and the values of the phase detection signal (S1, S2) are S1> S2, the value of the phase detection signal ( S1 and S2) are substituted into the above equations (a) and (b), and when S1 <S2, the values (S1, S2) of the phase detection signal are substituted into the above equations (a) and (c) and An arithmetic processing unit for _obtaining a pitch number (n) that simultaneously satisfies the two expressions, and substituting the pitch number (n) into the expression (a) to obtain the absolute position (P _n1 ). Absolute position detector.