FI100715B - Device for determining position - Google Patents

Description

100715

EQUIPMENT FOR LOCATION

The present invention relates to an apparatus for determining a location according to the preamble of claim 1.

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Elevator control systems require location information for many control or monitoring tasks, such as the location of an elevator car or its door. For example, when connecting a monitoring device in the area in front of the door, which optically detects the movement, to the old elevator, it is necessary to know because the door is closed so much that the door movement could cause an interfering expression. In many cases, information about the location of the door is obtained from the voltage of the "fully open" contact, which must be measured at an isolated input level that allows for the common voltage variations that occur in the control circuits of old elevators. There are also cases where it is necessary or advantageous for operation to generate a door area signal with a separate sensor that is active when the door is more open than the width of the selected light aperture. Such area-20 information has previously been formed, for example, by a magnetically memory tongue contact, in which a permanent magnet moving with the door opens or closes the contact depending on the bypass direction. However, this solution is unreliable in long-term hard use. Various known capacitive, inductive and optical proximity switches can also be used to generate door area location information.

It is an object of the present invention to provide better hardware for determining location than current solutions. In the method according to the invention, the ratio of two small capacitances is determined, on the basis of which the location can then be determined according to the characterizing part of claim 1.

Other preferred embodiments of the invention are set out in the other claims.

The solution according to the invention can have a wide range of applications, which are based either on bypassing the object in different directions or on accurately locating the object in a certain measuring range. Multiplexing can also be used, so that each pair of capacitances to be compared can be freely placed at different distances from other capacitance pairs and 5 measuring circuits. If necessary, the two comparable capacitances can also be placed separately from each other.

With the solution according to the invention, capacitive sensors can be separated from the measuring circuit even with a relatively long intermediate cable without the measurement accuracy being substantially impaired by electrical disturbances or stray capacitances of the conductors, which can be an order of magnitude larger than the capacitances to be measured.

In the following, the invention will be described in more detail by way of example with reference to the accompanying drawings, in which

Figure 1 shows an apparatus according to the invention.

Figure 2 shows the connection of the measuring circuit of the apparatus according to the invention.

Figure 3 shows an example of a measuring sensor according to the invention.

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Figure 4 shows the operation of the equipment in the operating range.

Figure 5 shows a timing diagram of an embodiment according to the invention.

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Figure 6 shows an example of multiplexing.

The apparatus according to the invention shown in Fig. 1 has two vertical sensor plates 1,2 at a distance from each other, which form a capacitive connection, described by the capacitors Cx and C2 shown in broken lines, with respect to the ground plane formed by the vertically moving, grounded metal plate 3. The sensor plates 1, 2 can be attached to the elevator car, for example, and the movable plate 3 to the elevator door.

5 The conductive planes 4 covering the background of the sensor plates 1, 2 are connected to a voltage Ur to be defined later, which prevents the measurement of capacitances in the grounded structures behind the sensor plates. The sensor plates 1, 2 are connected to the matching circuits 5 for the trouble-free transmission of the currents ilf i2. Each matching circuit has a first diode D1 # connected from its anode to the voltage Ur and its cathode to the sensor plate 1, 2, and a second diode D2 connected from its anode to the sensor plate 1, 2 and its cathode to the input i3, i2 of the measuring circuit 8. The matching circuits also have an attenuation resistor Rx between the diodes and the sensor plate 1, 2 and a capacitor C3 at the output between the anode of the diode D} and the cathode of the diode D2, which eliminates the effect of stray capacitances. The sensor plates 1, 2 are connected to the measuring circuit 8 by an intermediate cable 6. Before the measuring circuit there is a filter 7. If the stray capacitance of the conductors of the short intermediate-20 cable to the ground is small, a shield surrounding the conductors is not required. At long distances, a protective sheath is used, which is connected to the voltage Ur.

25 Capacitors and C2 pump the charge based on the fact that the voltage frame of the measuring circuit (eg +8 V and - / 8 V) co-oscillates between a zero level and a positive voltage level, eg U0 = +15 V at a certain frequency, eg f0 * 250 kHz , according to the signal from the oscillator 9. The electric charge is taken from the voltage level ör and fed to the measuring circuit 1 via diodes and D2 as average current values Ix and I2.

It is also possible to connect the oscillator 9 to the moving plate 35 3 and to ground the measuring circuit, whereby the moving plate 3 oscillates as described above. Otherwise, the circuit works accordingly. The measurement accuracy is improved because the capacitances of the ground planes farther from the moving plate 100715 4 to the sensor plates are then not included in the capacitances to be measured.

The currents Ix and I2 are 5 Ιχ ~ Οΐ Uq f0 I2 = CiUvf0

The output frequencies f2 and f2 change with respect to the currents and thus also the capacitances. In this way, the capacitances can be used to calculate the position of the moving plate 10 3 in a manner shown later, when the ratio of the capacitances is known. The sum of the frequencies is constant.

f ^ f2 = constant ± 2 ^ 2 * -2

The measuring circuit is shown in more detail in Figure 2.

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The position x of the moving plate, which shows the distance between the center line of the sensor plates 1, 2 and the center line of the moving plate 3 (both shown in broken lines) in the measuring range, is determined as follows: ^ q _ q x = ——- Ci + C2 20

In the circuit shown in Fig. 2, a constant current is supplied to the capacitor C6 through the resistor R13> and the transistor Q2, from which equal capacitors C7 and C8 pump current through the diodes D13 to D16, forming frequencies fx and f2.

The constant current is obtained from the base voltage of transistor Q1, which is based on the voltage distribution of resistors R8 and R9 and R10.

5 1CG715

The operation of the corresponding circuit in voltage measurement is described in FI publication 87402. The operation of the circuit can be described by the equations:

Uil ^ ko Ιλ 5 U ± l'12 = koll2 ^ 2 ~ ^ 2 - * 12 where the currents i ^ 'and i12' correspond to the currents ver-10 at the output frequencies. From these equations, the above relationships of frequencies, currents, and capacitances are obtained.

The sum current 122 + i12 = constant because it is generated by a constant current generator.

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The sum current in '+ i12' = in + i12 + I3 + I2 is approximately constant because the currents I3 and I2 proportional to the capacitances to be measured are an order of magnitude smaller than i31 and i12, which in this case follows with sufficient accuracy that the sum of the frequencies is constant.

The reference voltage Ur is applied to a value such that the pumping at frequencies fx + f2 is in equilibrium with the total current flowing to capacitors C7 and C8 25 i1; 1 + i12 + + I2.

In order to achieve the above operation, Fig. 2 shows an IC circuit ICa - ICf, the inputs and outputs of which are connected via diodes D17 to D20 and resistors R12 and R13 to a positive voltage of +8 V + 100 V and to the outputs fx via resistors R14 to R19 and transistors Q3 and Q4. and f2. The reference voltage Ur is connected to the voltage follower IC1.

5 By means of multiplexing, the same measuring circuit can be used, for example, as in Fig. 6, for several pairs of sensor plates. Such a multiplexing circuit can be connected between the filter 7 and the measuring circuit 8. The multiplexing is performed by generating rotating binary addresses, on the basis of which the selection signals necessary for multiplexing, S (i), i = ... n, are generated, which by means of diodes D3 to D6 alternately switch the currents of a certain sensor pair plate into input currents I3 and I2.

The solution according to the invention can be applied, for example, to determining the position of the elevator door according to Fig. 3 by means of a capacitance measurement according to the invention. It shows a sensor housing 4 'attached to the elevator car, in which the sensor plates 1' and 2 'are placed. Elevator door attached to a rectangular shape 20 panel 3 'moves the sensor plates 1', 2 · in front at an appropriate distance (so that the capacitance of a suitable magnitude, typically approx. 10 to 30 pF, when the movable plate covers the sensor board in full) of the as shown by the arrow of the door opening (left) or when closing (oi-25 kea). The sensor is connected to a measuring circuit (not shown) by an intermediate cable 6 '.

Figure 4 shows the door zone signal obtained from the measuring circuit in Figure 3 the double-headed arrow indicated in the 30-O region. The horizontal axis shows position S. The door is fully open on the left and completely closed on the right. The two curves shown in the figure illustrate the output at the minimum distance of the moving plate (curve 10) up to the value marked MIN (MIN refers to the minimum distance at capacitance 35 and the value of the curve is maximum, respectively) and at maximum distance at curve 11 only at MAX until. The figure also shows, in broken lines, the 100715 7 on and off thresholds for the applications of the following figures.

Figure 4 shows that the curves have a linear area in the middle of the sensor plates 5 on both sides, which can be used to determine the exact location in other applications. For example, for the movement of the elevator door to or from a certain area, the on and off values shown can again be used, as shown in Fig. 5.

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Figure 5 shows the on and off pulses and the operating range for the pair of sensor plates in Figure 3. As the movable plate 3 'moves to the right in the opening phase at the first plate 1', a switch-off pulse 12 is obtained which has no effect. The second sensor plate 2 # then gives a switch-on pulse 13, whereby the operating range signal indicates that the door is inside the open range (signal 14 at the top). Correspondingly, when the door begins to close, the second plate 2 'is first reached, whereby an on-20 switching pulse with no effect is obtained. Thereafter, the first plate 1 'gives a switch-off pulse, whereby information is obtained about the door moving outside the defined open range (signal 14 at the bottom), i.e. from the return to the initial situation.

It will be apparent to those skilled in the art that the various embodiments of the invention are not limited to the examples set forth above, but may vary within the scope of the claims set forth below.

Claims (4)

100715 8 An apparatus for capacitively determining the position of an object, the apparatus comprising two successive sensor plates (1,2) in the direction of movement and a moving plate (3) attached to the object at a short distance therefrom, the sensor plates and the moving plate forming a capacitor pair (ClrC2 ), and an associated measuring circuit (8), and an oscillator (9) for causing the measuring circuit (8) or the movable plate 10 (3) to oscillate at a certain frequency between specified voltage levels, whereby a capacitor pair pumps a charge in the measuring circuit. 8) controls the discharging of the capacitors of the capacitors (C1, C2) by means of directional elements (D1, D2) arranged in connection with the sensor plates (1,2) so that the charge is taken from a predetermined voltage level (Ur) and transferred to the capacitors (C7, C8) relative to the capacitances of the capacitors (Clrc2) of the currents (11, I2) which produce frequencies in the measuring circuit (8) proportional to said currents (flff2), and that the measuring circuit (8) determines the position of the object in a manner known per se by calculating the ratio of frequencies equal to that of the capacitors ( ClrC2) capacitance ratio, and by determining the position of the movable plate (3) by means of said ratio as the ratio of the difference and the sum of the capacitances of the capacitors. Apparatus according to claim 1, characterized in that the capacitances of the capacitors (¢ ^ .02) of the capacitor pair are substantially smaller than the capacitances of the capacitors (C7, C8) in the measuring circuit, said charge transfer taking place from substantially smaller capacitors of the capacitor pair (Clf2). capacitors (C7, C8) in the measuring circuit, the capacitance of which is affected by the stray capacitances 5 between the directing elements (D1 ^) and the measuring circuit (8), whereby the interference effect of said stray capacitances is not distorted on the capacitors of the capacitor pair Apparatus according to Claim 1 or 2, characterized in that the capacitors (C 1, C 2) of the capacitor pair are connected to the measuring circuit (8) by means of an intermediate cable (6). Apparatus according to Claim 1, characterized in that a multiplexing circuit (D3 to D6) is connected to the measuring circuit, which is controlled by a circulating address and by means of which the measuring circuit measures the charge of a plurality of capacitor pairs according to a predetermined time division. 100715 10