JPS60161504A - Position detection apparatus - Google Patents

Abstract

PURPOSE:To obtain a position detection apparatus not affected by voltage of a power source and having good response and detection sensitivity, by applying voltages with inverse polarities to first and second potentiometers and allowing slide elements of both potentiometers to cooperate with the movement of one position detection probe to take out the difference of output voltages of said slide elements. CONSTITUTION:A positive DC power source 1a and a negative DC power source 1b are connected in series and voltages with inverse polarities are applied to a first potentiometer 7a and a second potentiometer 7b. A position detection probe 4 is connected to the handles of slide elements 8a, 8b in the case of linear detection and connected to the rotary shafts thereof in the case of rotary detection and said slide elements 8a, 8b are moved in cooperated relation to the movement of the probe needle 4. The difference output (amplification ratio multiplied value) of the slide elements 8a, 8b is removed through a differential amplifier 9. Said difference output is proportional to the positions of the potentiometers 7a, 7b and is not affected at all by the variation in the voltages of the power sources. By this mechanism, a position detection apparatus having good response and sensitivity is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a position detection device for a logget, a grinder, a copying control device, etc.

Conventionally, analog position detecting devices, mainly detecting devices for the purpose of zero point position detection, include a differential transformer type shown in FIG. 1 and a potentiometer type shown in FIG. 2. The differential transformer type position detection device includes a DC power supply 1, an AC oscillation circuit 2 for exciting the secondary coil, a secondary coil 3a, a position detection probe 4, a secondary coil 3b, a phase discrimination circuit 5, and a smoothing circuit 6. . In this type of detection device, the structure of the sensor section, which mainly includes the position detection probe 4, is complicated, and the zero point changes due to temperature fluctuations. There are many components, and the smoothing circuit 6 delays signals, making it unsuitable for high-speed response requirements.Furthermore, the smoothing circuit 6 is used for rotational position detection, and due to its structure, the detection range is narrow, for example, only about ±30''.

Further, as shown in FIG. 2, the potentiometer type position detection device includes a positive DC power supply 1a, a negative DC power supply 1b,
It consists of a potentiometer 7, a position detection probe 4, a slider 8, and a differential amplifier 9.

In such a position detection device, the voltage tEpcV of the positive DC power supply 1a and the voltage tEn(V
], and the total stroke of the potentiometer 7 (sliding range of the slider 8) which is the sensor part is L (am ],
The amplification factor of the differential amplifier 9 is assumed to be A. Here, the slider 8 of the potentiometer 7 is xc from the center of the stroke.
t-], the terminal voltage of the slider 8 is given by the following equation.

' (Ep-En)/2+(Ep+En) e (x/
I, Month [■] Therefore, the detected output voltage after passing through the differential amplifier 9 is as follows.

A・((Ep En)/2+(Ep+En)・(X/L
Month [V] As can be seen from this formula, the detected output voltage is.

It is only when Ep=En that the detected output voltage is completely proportional to the slider position X.

(A ・(gp10En) ・(x/L,) ) (V:
It becomes l.

However, in reality, there are few times when the voltage completely satisfies E, = E, and 5mEp and En change completely independently due to fluctuations in the ambient temperature and the supply voltage, which is a DC power supply.
A voltage of A((F, -Fn)/2(V)) is superimposed on the detection output voltage, resulting in poor accuracy.

Also, the position where the output voltage becomes zero, the so-called zero point, is Ep-
En! In the case of qO, it is the position of X shown in the following formula.

x = ((Eye-Ep)/(Ep+En))-(
L/2) (mal)As can be seen from this equation, this position is affected by fluctuations in the power supply voltage.

Also, the change in the detection output voltage with respect to the change in the slider position device is the detection sensitivity, and this sensitivity is (A・(Ep+En
)/L, ] (V/m) However, this value may be insufficient depending on the application, and it also has the disadvantage of being difficult to use.

Therefore, in view of the above-mentioned drawbacks, the present invention eliminates the disadvantages of the differential transformer type, such as the complexity of the structure, the fluctuation of the zero point, the lack of coordination, and the narrow range of rotational position, and also eliminates the disadvantages of the differential transformer type, such as the complexity of the structure, the fluctuation of the zero point, the lack of coordination, and the narrow range of rotational position. The object of the present invention is to provide a position detecting device which eliminates the disadvantages of poor detection accuracy, being easily influenced by power supply voltage fluctuations, and having poor detection sensitivity.

The basic idea of the present invention to achieve such an object is to set the voltages applied to the first potentiometer and the second potentiometer to have opposite polarities so as to control the movement of the position detection probe of each slider t-1. The two sliders are linked together to extract the difference in output voltage that appears on each slider.

The present invention will now be described in detail with reference to FIG. Note that the same parts as in FIGS. 1 and 2 are given the same reference numerals. A positive DC power supply 1a and a negative DC power supply 1b are connected in series. The positive terminal of the DC power source 1a is connected inside the sensor section, and connected to the upper terminal of the first potentiometer 7a and the lower terminal of the second potentiometer 7b in the sensor section. The negative terminal is connected to the lower terminal of the first potentiometer 7a and the upper terminal of the second potentiometer 7b in the sensor section.Therefore, the DC power supplies 1a, lb
The first potentiometer 7a and the second potentiometer 7b are connected in parallel with each other, and the applied voltages are of opposite polarity.

The first and second potentiometers 7a, 7b have sliders 8a, 8b, respectively, and the slider 8a
, 8b, the first slider 8a is connected to one terminal of the differential amplifier 9, and the second slider 8b is connected to a child terminal of the differential amplifier 9.

In addition, in the case of straight line detection, the sliders 8a and 8b have their handles
In the case of rotation detection, the position detection probe 4 is connected to the rotation axis, and similarly moves in accordance with the movement of the position detection probe 4. That is, the strokes (sliding ranges) of the sliders 8a and 8b are the same, and the positions of the sliders from the lower stroke end in the respective potentiometers 7a and 7b are always the same. are connected to each other. The output of the differential amplifier 9 is the difference between the voltages of the respective sliders 8a and 8b multiplied by the amplification factor.

In such a configuration, the voltage of the DC power supply 1a is Ep (V)
, the voltage of the DC current Jlb is En (V), and the total stroke of the first and second potentiometers 17a + 7b is L.
(m ), and the amplification factor of the differential amplifier 9 is A.The first
And the fingers 8a, 8b of the second potentiometers 7a, 7'b move from the stroke center position 1 to X [
:=) When the voltage is above, the voltage appearing on the sliders 8a and 8b is expressed by the following equation.

(Voltage of 8a) ((Ep En)/2 + (Ep+En) ・(”/
L) ) (:V] (voltage of 8b) ((Ep En)/2 (Ep"'n) ' (x/L
[■] As a result, the voltage appearing at the OU'f' terminal of the differential amplifier 9 is obtained by multiplying the difference between the voltages of the above two equations by the amplification factor A, and is expressed by the following equation.

(2・A・(Ep+En)・(vL, month [v]) In this way, the output voltage of the differential amplifier 9 is completely proportional to the position XM of the potentiometers 7a and 7b.Then, the position where the output voltage is 0, The so-called zero point is always at the position where x=Q and is completely unaffected by fluctuations in the power supply voltage'.

As explained in the embodiments above, according to the present invention, the structure is simple and can be manufactured at low cost, the zero point does not change at all with fluctuations in the power supply voltage, the response is good, and the detection sensitivity is different from that of the conventional potentiometer type. It is twice the size of the position detection device, and the rotational position range is not narrowed.

[Brief explanation of the drawing]

Figures 1 and 2 are examples of conventional position detection devices.
2 is a block diagram of a differential transformer type, FIG. 2 is a block diagram of a potentiometer type, and FIG. 3 is a block diagram showing an embodiment of the present invention. In the drawings, la and lb are DC power supplies, 4 is a position detection probe, 7a and 7b are potentiometers, 8a and 8b are sliders, and 9 is a differential amplifier. Patent Applicant: Mitsubishi Heavy Industries, Ltd. Sub-Agent Patent Attorney: Shibu Mitsuishi (and 1 other person) Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] The handles or rotating shafts of the sliders of the first potentiometer and the second potentiometer are connected to a position detection probe so that the sliders move simultaneously, and a voltage is applied to each of the first potentiometer and the second potentiometer. A position detection device in which each potentiometer is connected so that the voltage applied thereto has opposite polarity, and the difference in voltage appearing on the slider of each potentiometer is extracted.