JP6642915B2 - Electromagnetic induction type position detector - Google Patents

Description

  The present invention relates to an electromagnetic induction type position detector.

  2. Description of the Related Art Inductosin type scales, which are electromagnetic induction type position detectors, are applied to position detection in various machines such as machine tools, automobiles, and robots. There are a linear scale and a rotary scale in the scale of the inductosin system.

  The linear scale is installed on a moving body such as a table of a machine tool and detects the linear moving position of the moving body. The rotary scale is mounted on a moving body (a rotating body) such as a rotary table of a machine tool. It is installed and detects the rotational position (rotation angle) of the moving body (rotating body).

  Both the linear scale and the rotary scale detect positions by electromagnetic induction of coil patterns arranged so as to face each other in parallel. This detection principle will be described with reference to the principle diagram of FIG.

  FIG. 6A is a perspective view showing a state in which a linear scale slider and a scale are arranged so as to face each other in parallel, FIG. 6B is a schematic view showing the slider and the scale side by side, and FIG. ) Is a graph showing the degree of electromagnetic coupling between the slider and the scale.

  The detection principle of the rotary scale is the same as that of the linear scale, and the stator and rotor of the rotary scale correspond to the slider and scale of the linear scale. Each of the linear scale and the rotary scale has a detection unit and a detection control device.

  As shown in FIGS. 6A and 6B, the linear scale detection unit 100 includes a slider 101 as a primary member and a scale 102 as a secondary member.

  The slider 101 is a movable part, and has a first slider coil 103 that is a first primary coil and a second slider coil 104 that is a second primary coil. The scale 102 is a fixed part and has a scale coil 105 as a secondary coil. The coils 103, 104, and 105 are folded in a zigzag shape (having a comb-shaped pattern), and are formed so as to extend linearly as a whole.

  The slider 101 is attached to a moving body such as a table of a machine tool, and moves linearly with the moving body. The scale 102 is fixed to a fixed part such as a bed of a machine tool.

  As shown in FIG. 6A, the slider 101 (the first slider coil 103 and the second slider coil 104) and the scale 102 (the scale coil 105) maintain a predetermined gap g between them. They are arranged facing each other. As shown in FIGS. 6A and 6B, the first slider coil 103 and the second slider coil 104 are shifted by １ ／ pitch.

  In the linear scale having the above configuration, when an exciting current (AC current) is applied to the first slider coil 103 and the second slider coil 104, the slider of the first slider coil 103 and the second slider coil 104 and the scale coil 105 As shown in FIG. 6C, the degree of electromagnetic coupling between the first slider coil 103 and the second slider coil 104 and the scale coil 105 changes in accordance with the change in the relative positional relationship accompanying the movement of the 101. Change. Therefore, a periodically induced voltage is generated in the scale coil 105.

Specifically, in the detection control device of the linear scale, a current Ic shown in the following equation (1) is applied to the first slider coil 103, and a current Is shown in the following equation (2) is applied to the second slider coil 104. I do.
Ic = -Icos (kα) sin ( ω c t) ... (1)
Is = Isin (kα) sin ( ω c t) ... (2)
(However, I: magnitude of current, k: 2π / P, P: length of one pitch of the scale coil (angle in a rotary type scale), ω _c : angular frequency of AC current, t: time, α: parameter )

As a result, due to the electromagnetic induction between the first slider coil 103 and the second slider coil 104 and the scale coil 105, an induced voltage V expressed by the following equation (3) is generated in the scale coil 105.
_{V = ω c K (g)} Isin (k (X-α)) sin (ω c t) ... (3)
(However, K: coefficient depending on the gap g between the slider coil and the scale coil, X: displacement of the scale (detection position))

  The detection control device inputs the induced voltage V of the scale coil 105, calculates the value of a parameter α at which the induced voltage V becomes 0 (that is, α at which X = α), and calculates the parameter α The current Ic and the current Is are output based on the parameter α and output as the detection position X of the slider 101). That is, by controlling the parameter α to follow the position X of the moving body so that X = α and controlling the induced voltage V = 0, the position X of the moving body is detected and output.

  Patent Document 1 below discloses a technique for always performing stable and highly accurate angle detection in an angle detection device that detects the angle of a resolver.

JP 2014-122885 A

  The conventional electromagnetic induction type position detector described above has the following problems [1] to [3].

[1] When the first slider coil 103, the second slider coil 104, and the scale coil 105 become smaller, the coupling degree ω _c K (g) decreases, and the SN ratio deteriorates. Therefore, compactness is not easy.

[2] When the gap g is widened, the degree of coupling ω _c K (g) decreases and the SN ratio deteriorates. Therefore, a large gap cannot be obtained.

[3] When ω _{c is set} to a high frequency, ω _c K (g) increases and the signal can be increased. However, when a current waveform applied to the first slider coil 103 and the second slider coil 104 is generated by a DA converter, As shown in the graph of FIG. 7, the sampling frequency (period Δt) of the DA converter needs to be several tens of times ω _c (the rectangular line in the figure). Therefore, when the frequency ω _c increases, the DA converter becomes expensive. Or cannot be realized. Note that T in FIG. 7 is T = 2π / ω.

  Therefore, an object of the present invention is to provide an electromagnetic induction type position detector that can improve the degree of electromagnetic coupling between a primary coil and a secondary coil.

An electromagnetic induction type position detector according to a first invention for solving the above-mentioned problems,
A primary member having a first primary coil and a second primary coil, a secondary member having a secondary coil, and the first primary coil and the second primary coil. A signal generator for applying a signal, wherein the primary side member or the secondary side member is attached to a moving body and moves together with the moving body, and the first primary side coil and the second primary side An electromagnetic induction type position detector, wherein the coil and the secondary coil are arranged to face each other with a gap,
The signal generator applies, to the first primary member, a signal obtained by inverting the polarity at a period of 2π / ω when ω _c <ω with respect to a current Ic shown in the following equation (A). Then, for the current Is shown in the following equation (B), when ω _c <ω and the polarity is inverted at a period of 2π / ω, the signal is applied to the second primary member as the signal,
further,
A control unit that performs position detection by adjusting α so that the induced voltage generated in the secondary coil is set to 0 is provided.
Ic = -Icos (kα) sin ( ω c t) ... (A)
Is = Isin (kα) sin ( ω c t) ... (B)
However, the magnitude of I is current, k is 2 [pi / P, P is the length or angle of one pitch of the secondary side coil, omega _c is the angular frequency, t is time, alpha is the parameter

ただし、ｎは整数 An electromagnetic induction position detector according to a second invention for solving the above-mentioned problems,
In the electromagnetic induction type position detector according to the first aspect,
The signal generator inverts the polarity at a period of 2π / ω by multiplying the current Ic and the current Is by Z (t) shown in the following equation.

Where n is an integer

An electromagnetic induction position detector according to a third invention for solving the above-mentioned problems,
In the electromagnetic induction type position detector according to the first or second aspect,
further,
A low-pass filter for removing a term of n> 1 from the induced voltage;
The control unit performs position detection by adjusting the parameter α so that the output from the low-pass filter is set to 0.

  ADVANTAGE OF THE INVENTION According to the electromagnetic induction type position detector which concerns on this invention, the electromagnetic coupling of a primary side coil and a secondary side coil can be improved.

1 is a block diagram illustrating an electromagnetic induction type position detector according to a first embodiment of the present invention. It is a graph which shows Z (t). It is a graph which shows current Ic '. 4 is a graph comparing an induced voltage V by a conventional electromagnetic induction type position detector with an induced voltage Vf by an electromagnetic induction type position detector according to the first embodiment of the present invention. It is a block diagram explaining the electromagnetic induction type position detector concerning Example 2 of the present invention. It is a figure explaining the principle of position detection by the conventional electromagnetic induction type position detector. (A) is a perspective view showing a state in which a slider and a scale of a linear scale are arranged so as to face each other in parallel; It is a graph which shows a degree of electromagnetic coupling. 5 is a graph illustrating generation of a current (Ic) based on a digital signal. The vertical axis indicates intensity, and the horizontal axis indicates time.

  Hereinafter, an electromagnetic induction type position detector according to the present invention will be described with reference to the drawings using embodiments. In the following, a linear scale is described as an example, but the same applies to a rotary scale.

[Example 1]
FIG. 1 is a block diagram illustrating an electromagnetic induction type position detector according to the present embodiment. The electromagnetic induction type position detector according to the present embodiment mainly includes a detection unit 10, a signal generator 16 as a detection control device, a low-pass filter 17, and a control unit 18. The detection unit 10 is the same as the conventional detection unit 100. In FIG. 1, the slider and the scale are omitted, and only the coils (the first slider coil 13, the second slider coil 14, and the scale coil 15) are shown. ing.

The signal generator 16 applies a current Ic ′ shown in the following equation (4) to the first slider coil 13 and a current Is ′ shown in the following equation (5) to the second slider coil 14.
Ic' = -Icos (kα) sin ( ω c t) Z (t) ... (4)
Is' = Isin (kα) sin ( ω c t) Z (t) ... (5)

（ただし、ｎは整数） Z (t) is a rectangular wave (rectangular pulse waveform), and when Fourier-expanded, it is expressed by the following equation (6) and becomes a waveform shown in the graph of FIG.

(However, n is an integer)

Therefore, the current Ic 'is represented by the following equation (7') (converted from the following equation (7)), and has a waveform shown in the graph of FIG. That is, the current Ic ′ is obtained by inverting the polarity of the current Ic shown in the above equation (1) at a period of 2π / ω. Incidentally, T in FIG. 3 is a T = 2π / ω _c.

Similarly, the current Is' is expressed by the following equation (8). That is, the current Is ′ is obtained by inverting the polarity of the current Is represented by the above equation (2) at a period of 2π / ω.

By applying the currents Ic 'and Is' to the first slider coil 13 and the second slider coil 14, respectively, an induced voltage V' shown in the following equation (9) is generated in the scale coil 15.

In the electromagnetic induction type position detector, the detection position X is a parameter α such that V ′ becomes zero. However, in this embodiment, a low-pass filter 17 is provided. The low-pass filter 17 outputs a voltage Vf obtained by removing a term of n> 1 from the induced voltage V ′ generated in the scale coil 15. The voltage Vf is represented by the following equation (10 ′) (converted from the following equation (10)).

  The controller 18 adjusts the parameter α of the currents Is ′ and Ic ′ so that the voltage Vf becomes 0, and performs position detection with the position X = α.

FIG. 4 shows an increase in the degree of electromagnetic coupling according to this embodiment. FIG. 4 is a graph comparing the induced voltage V of the conventional electromagnetic induction type position detector with the induced voltage Vf of the present embodiment. FIG. 4 shows a case where ω _c = 2π × 100 kHz and ω = 2π × 4 MHz as an example.

As shown in FIG. 4, the amplitude of the induced voltage Vf of the present embodiment is greatly increased as compared with the conventional induced voltage V. That is, it can be seen that in the present embodiment, the degree of electromagnetic coupling is improved. Thus, in the present embodiment, it is possible to prevent the SN ratio from deteriorating. In particular, when the frequency ω _c is set to a high frequency of ω _c << ω, the degree of coupling is further improved. Further, when the currents Ic and Is are generated using the DA converter, it is not necessary to greatly increase the sampling frequency ω of the DA converter.

[Example 2]
FIG. 5 is a block diagram illustrating an electromagnetic induction type position detector according to the present embodiment. As shown in FIG. 5, the electromagnetic induction type position detector according to the present embodiment mainly includes a detection unit 10, a signal generator 21 as a detection control device, a first inversion circuit 22, and a second inversion circuit 23. , A low-pass filter 17 and a control unit 18.

  The detection unit 10 is the same as the conventional detection unit 100. In FIG. 5, the slider and the scale are omitted, and only the coils (the first slider coil 13, the second slider coil 14, and the scale coil 15) are shown. ing. The low-pass filter 17 and the control unit 18 are the same as in the first embodiment, and a description thereof will be omitted.

  The signal generator 21 includes a signal generator 21a that outputs the current Ic shown in the above equation (1) and the current Is shown in the above equation (2), respectively, and a first inverting circuit 22 and a second inverting circuit 23 described later. Have.

  The first inversion circuit 22 inverts the polarity of the current Ic at a period of 2π / ω, and applies the inverted current to the first slider coil 13 as a current Ic ′. The current Ic 'has a waveform similar to the current Ic' described in the first embodiment with reference to FIG.

  The second inverting circuit 23 inverts the polarity of the current Is at a period of 2π / ω and applies this to the first slider coil 13 as a current Is ′. Note that the current Is 'has a waveform similar to the current Is' described in the first embodiment.

  As described above, in the present embodiment, the waveforms of the currents applied to the first slider coil 13 and the second slider coil 14 are the same as those of the first embodiment, and the same operation and effects as those of the first embodiment can be obtained. .

  The present invention is suitable as an electromagnetic induction type position detector.

10, 100 detector 13, 103 first slider coil (first primary side coil)
14, 104 Second slider coil (second primary coil)
15,105 Scale coil (secondary coil)
16, 21 signal generator 21a signal generator 17 low-pass filter 18 controller 22 first inverting circuit 23 second inverting circuit 101 slider 102 scale

Claims (3)

A primary member having a first primary coil and a second primary coil, a secondary member having a secondary coil, and the first primary coil and the second primary coil. A signal generator for applying a signal, wherein the primary side member or the secondary side member is attached to a moving body and moves together with the moving body, and the first primary side coil and the second primary side An electromagnetic induction type position detector, wherein the coil and the secondary coil are arranged to face each other with a gap,
The signal generator applies the current Ic shown in the following formula (A), whose polarity is inverted at a period of 2π / ω when ωc <ω, to the first primary coil as the signal. A current Is shown in the following equation (B), the polarity of which is inverted at a period of 2π / ω when ωc <ω is applied to the second primary coil as the signal,
further,
An electromagnetic induction type position detector, comprising: a control unit that performs position detection by adjusting α so that an induced voltage generated in the secondary coil is set to 0.
Ic = −Icos (kα) sin (ωct) (A)
Is = Isin (kα) sin (ωct) (B)
Here, I is the magnitude of current, k is 2π / P, P is the length or angle of one pitch of the secondary coil, ωc is angular frequency, t is time, α is a parameter 2. The signal generator according to claim 1, wherein the polarity is inverted at a period of 2π / ω by multiplying the current Ic and the current Is by Z (t) shown in the following equation. 3. Electromagnetic induction type position detector.

Where n is an integer further,
A low-pass filter for removing a term of n> 1 from the induced voltage;
3. The electromagnetic induction type position detector according to claim 1, wherein the control unit performs position detection by adjusting the parameter α such that an output from the low-pass filter is set to 0. 4.

Images