JPH0361883B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a position detection device for a robot, 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 primary coil, a primary 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 fluctuates due to temperature fluctuations. There are many components, and the smoothing circuit 6 delays signals, making it unsuitable for high-speed response requirements.Furthermore, for rotational position detection, the detection range is narrow, for example, only about ±30° due to its structure.

As shown in FIG. 2, the potentiometer type position detection device includes a positive DC power supply 1a, a negative DC power supply 1b, a potentiometer 7, a position detection probe 4, a slider 8, and a differential amplifier. Consists of 9. In such a position detection device, the voltage of the positive DC power source 1a is Ep [V], and the voltage of the negative DC power source 1b is En.
[V], and the entire stroke of the potentiometer 7 (sliding range of the slider 8), which is a part of the sensor, is L.
[mm], and the amplification factor of the differential amplifier 9 is A.
Here, when the slider 8 of the potentiometer 7 is located x [mm] above the center of the stroke, the terminal voltage of the slider 8 is given by the following equation.

{(Ep-En)/2+(Ep+En) · (x/L)} [V] Therefore, the detected output voltage after passing through the differential amplifier 9 is as follows.

A. {(Ep-En)/2+(Ep+En) ・(x/L)} [V] As can be seen from this formula, the detected output voltage is
It is only when Ep = En that it is completely proportional to the slider position x, and the detected output voltage at that time is:
{A・(Ep+En)・(x/L)}[V].

However, in practice, there are few times when the voltage perfectly satisfies Ep = En, and Ep and En change completely independently due to fluctuations in the ambient temperature and the supply voltage, which is a DC power supply, so the detected output voltage has a {(Ep−
En)/2}[V] voltages are superimposed and accuracy deteriorates.

Further, the position where the output voltage becomes zero, so-called zero point, is the position of x shown in the following equation when Ep-En≠0.

x={(En−Ep)/(Ep+En)}·(L/2) [mm] As is clear 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 position of the slider is the detection sensitivity, and this sensitivity is expressed as {A・
(Ep+En)/L} [V/mm], but this value is insufficient for some applications and has the drawback 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, fluctuation of the zero point, lack of quick response, and narrow rotational position range, and also eliminates the drawbacks of the differential transformer type, such as the complexity of the structure, The object of the present invention is to provide a position detection device that eliminates the disadvantages of poor detection accuracy, susceptibility to power supply voltage fluctuations, and poor detection sensitivity.

The basic idea of the present invention to achieve this purpose is the first
The voltages applied to the potentiometer and the second potentiometer are made to have opposite polarities so that each slider is linked to the movement of one position detection probe, so that the voltage appearing on each slider is This is designed to extract the difference in output voltage.

An embodiment of the present invention will now be described 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. DC power supply 1
The positive terminal of a is connected within the sensor section, and is connected to the upper terminal of the first potentiometer 7a and the lower terminal of the second potentiometer 7b within the sensor section. On the other hand, the negative terminal of the DC power supply 1b is connected to the first potentiometer 7a in the sensor section.
and the upper terminal of the second potentiometer 7b, respectively. Therefore,
A first potentiometer 7a and a second potentiometer 7b are connected to a series body of DC power supplies 1a and 1b.
are connected in parallel to each other, and the applied voltages are of opposite polarity.

First and second potentiometers 7a, 7b
have sliders 8a and 8b, respectively. Of these sliders 8a and 8b, the first slider 8a is connected to the - terminal of the differential amplifier 9, and the second slider 8a is connected to the negative terminal of the differential amplifier 9.
b is connected to the + terminal of the differential amplifier 9. Also,
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 sliders 8a, 8
b have the same stroke (sliding range), and each potentiometer 7a, 7
The positions of the slider in b from the lower stroke end are mechanically coupled so that they are always equal. The output of the differential amplifier 9 is the difference between the voltages of the respective sliders 8a and 8b multiplied by an amplification factor.

In such a configuration, the voltage of the DC power supply 1a is
Ep [V], the voltage of the DC power supply 1b is En [V], the total stroke of the first and second potentiometers 7a, 7b is L [mm], and the amplification factor of the differential amplifier 9 is A.
shall be. First and second potentiometer 7
When the sliders 8a, 8b of a, 7b are x [mm] above the stroke center position, the sliders 8a, 8b
The voltage appearing at b is given by the following equation.

(Voltage of 8a) {(Ep-En)/2+(Ep+En) ・(x/L)} [V] (Voltage of 8b) {(Ep-En)/2-(Ep+En) ・(x/L)} [V] As a result, the voltage appearing at the OUT 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).(x/L)} [V] In this way, the output voltage of the differential amplifier 9 is completely proportional to the position x of the potentiometers 7a and 7b. The position where the output voltage is 0, the so-called zero point, is always the position where x=0 and is completely unaffected by fluctuations in the power supply voltage.

As explained above in the embodiments, 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 respect to fluctuations in the power supply voltage, and the responsiveness is good.
The detection sensitivity is also twice that of conventional potentiometer type position detection devices, and the range of rotational positions is not narrowed.

[Brief explanation of drawings]

Figures 1 and 2 show examples of conventional position detection devices, with Figure 1 being a differential transformer type configuration diagram, Figure 2 being a potentiometer type configuration diagram, and Figure 3 being an example of an embodiment of the present invention. It is a block diagram which shows an example. In the drawing, 1a and 1b are DC power supplies, 4 is a position detection probe, 7a and 7b are potentiometers, and 8a and 8
b is a slider, and 9 is a differential amplifier.

Claims (1)

[Claims] 1 Connect the handles or rotating shafts of the sliders of the first potentiometer and the second potentiometer to the position detection probe so that the sliders of the first potentiometer and the second potentiometer move simultaneously, and A position detection device in which the potentiometers are connected so that the voltages applied to each second potentiometer have opposite polarities, and the difference in voltage appearing on the slider of each potentiometer is detected.