JPH06167303A - Position detecting apparatus - Google Patents

Abstract

PURPOSE:To detect a connection failure by obtaining an absolute value of the output difference between a starting point and a terminal point of every constant detecting cycle wherein a connection failure is detected, and detecting whether or not the absolute value exceeds an absolute value of the output difference in the operable range at the maximum operating speed. CONSTITUTION:Interlocking with the opening/closing control of a guide vane, a sliding contact element 1b of a potentiometer 1 turns while sliding on a slide resistance 1a. The output 1A of the potentiometer 1 is input to a converter 2. A controlling power source P is connected to the converter 2, so that the input output 1A is converted to a suitable value for an opening degree indicator 2P to indicate the opening degree of the guide vane. As a result, an output 2A is generated. The output 2A is input to an adder 8 through a previous value memory circuit 7 which constitutes a detector D for detecting a connection failure of the indicator 2P and the potentiometer 1. The indicator 2P accordingly indicates the opening degree of the guide vane. The detector D is processed by software of microprocessor. The detection of a connection failure by the detector is carried out every constant preset detecting cycle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a position detecting device for detecting the position or rotation angle of an object by using a potentiometer, and more particularly to a function capable of detecting poor contact of the potentiometer. The present invention relates to a provided position detection device.

[0002]

2. Description of the Related Art It is well known that a potentiometer is frequently used for the purpose of detecting the position or the rotation angle of a subject constituting a controlled object. For example, it is used to detect the dam water level of a hydraulic power plant or the guide vane opening of a water turbine. It is detected by indicating an outside value.

FIG. 3 is a block diagram showing an example of a conventional general potentiometer abnormality detection circuit. In FIG. 3, reference numeral 1 is a potentiometer. Reference numeral 1a is a sliding resistance, reference numeral 1b is a sliding contactor, which is interlocked with the movement (linear movement or rotational movement) of a subject (not shown) and rotates while contacting the sliding resistance 1a. Both terminals of the sliding resistance 1a and the output terminal of the sliding contact 1b are respectively provided with potentiometers.
Converter 2 (hereinafter referred to as a converter). A control power source P is connected to the converter 2 and an output 1A of the potentiometer 1 corresponding to the position of the sliding contact 1b is input to the converter 2 for controlling or instructing the meter to an appropriate value (for example, an appropriate value). One rotation of the sliding contact 1b 0 to 360 degrees is 4 to 2
0mA), potentiometer converter output 2A
(Hereinafter referred to as output, 4 to 20 mA) is output. Output 2
A is input to the two comparators 4 and 5, respectively, and is compared with the reference values R1 and R2 preset in the respective comparators 4 and 5. When the input value <reference value R1, the comparator 4 compares When the input value> reference value R2, the instrument 5 outputs 4A and 5A, respectively.
Cause (The outputs 4A and 5A are not output at the same time.) These outputs 4A and 5A are input to the OR circuit 6, and when either one of the inputs is present, the OR circuit 6 produces the output 6A as an abnormality detection signal. The alarm is issued by being input to an alarm device (not shown).

The output 2A of the converter 2 shown as an example
Is 4 to 20 mA, the reference values of the comparators 4 and 5 are set to 4 mA and 20 mA, respectively. Then, in the comparator 4, the output 2A of the converter 2 is equal to the converted value 4
If it is less than the range of -20 mA and less than 4 mA, for example, this is detected and output 4A is produced. In the comparator 5, the output 2A of the converter 2 is the converted value 4 to 20 m.
If it is larger than the range of A and exceeds 20 mA, for example, it is detected and an output of 5 A is generated. The respective outputs 4A or 5A thus obtained are output as an abnormality detection signal 6A via the OR circuit 6, and the abnormality of the potentiometer 1 is detected.

By the way, in the potentiometer 1, the sliding resistance 1a has a sliding surface formed on the sliding resistance 1a while the sliding contact 1b is in contact with the sliding resistance 1a, and as the integrated value of the number of operations increases, The frequency of occurrence of poor contact of the sliding contact 1b with the sliding resistance 1a also increases. In the potentiometer in which the sliding contact 1b is controlled only in a specific narrow range on the sliding resistance 1a depending on the type of the controlled object,
This tendency becomes particularly remarkable.

The poor contact of the potentiometer 1 means that the contact itself of the sliding contact 1b with respect to the sliding resistance 1a does not become mechanically defective, but is usually the sliding surface and the sliding contact. 1b indicates a phenomenon in which the contact resistance value with 1b gradually increases. Therefore, in the conventional potentiometer abnormality detection circuit shown in FIG. 3, the abnormality output at the contact failure stage is detected within the range of the normal output 2A of the converter 2, which is generally caused by the contact failure. Since it is much larger than the deviation (2A'-2A) from the correct value 2'of ', almost none can be expected in the most range except the vicinity of both terminals of the slip resistance 1a, especially ,
In the potentiometer used in a narrow range near 180 degrees which is the middle (1/2 position) of the slip resistance 1a,
It is impossible to detect poor contact.

[0007]

The problem to be solved by the present invention is that it is almost impossible to detect an abnormality in the entire range of the sliding resistance of the potentiometer at the contact failure stage. . Therefore, it is an object of the present invention to obtain a position detecting device having an abnormality detecting function in the contact failure stage over the entire range of the sliding resistance of the potentiometer.

[0008]

In order to solve the above problems, the present invention uses a potentiometer that operates in conjunction with the movement of a subject and produces an output in response to the movement of the subject, In the position detection device for detecting the position of the subject, the potentiometers before and after the contact failure detection period of the potentiometer having a predetermined fixed period as a period. Input the output of each of the input and output the difference of these two inputs, the output of this adder is input, the absolute value circuit that outputs the absolute value of this input, and the output of this absolute value circuit Input, this input is
A comparator that produces an output when the potentiometer exceeds the absolute value of the difference between the outputs of the potentiometers before and after the range in which the potentiometer can operate at its maximum operating speed within the detection cycle; It is characterized by comprising from.

[0009]

The absolute value of the difference between the outputs of the potentiometers at the start point and the end point (front and back) of the detection cycle is calculated for each contact failure detection cycle having a predetermined fixed time cycle. The absolute value of this difference is the absolute value of the difference between the outputs of the potentiometers at the start point and end point (front and rear) of the range in which the potentiometer can operate at its maximum operating speed within the above detection cycle. It is determined whether or not the contact is exceeded, and when it is exceeded, it is determined that the contact is poor with the potentiometer, so that the contact is detected over substantially the entire range of the potentiometer. You can do it.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention, and the same parts as those in FIG. 3 are designated by the same reference numerals. FIG. 2 is a diagram showing the output waveform of each part for explaining the operation of the contact failure detector of the present invention. In FIG. 1, reference numeral 1 is a potentiometer.
1a is a sliding resistance, 1b is a sliding contact, 2 is a converter, 2A is its output, and 2P is an opening indicator of a guide vane (not shown) described later. A device surrounded by an alternate long and short dash line and entirely indicated by a symbol D is a contact failure detector for detecting a contact failure of the potentiometer 1.

The output 2A of the converter 2 is input to the previous value memory circuit 7 and the adder 8. 7A is the output of the previous value memory circuit 7, which is input to the adder 8. In the adder 8, the output 2A of the converter 2 and the output 7 of the previous value memory circuit 7 are output.
The operation of obtaining the difference from A (2A-7A) is performed to generate an output 8A, which is input to the absolute value circuit 9. The absolute value circuit 9 outputs the absolute value of the input 8A 9
The output 9A is output as A, and the output 9A is input to the comparator 10.
Although the details will be described later, the comparator 10 is input with a predetermined set value 9S, and the set value 9S and the input 9A are input.
Is compared, and the input 9A is larger than the set value 9S (9A>
At the time of 9S), it is determined that the contact of the potentiometer 1 is poor, and the poor contact detection signal 10A is output.

The above has described only the configuration of the present invention shown in the block diagram and the flow of signals between the components. Next, the potentiometer 1 is installed in, for example, a hydroelectric power plant. The operation for detecting the contact failure of the potentiometer 1 when it is used for instructing the opening of the guide vane of the water turbine will be described in detail.

Before entering into the operation of contact failure detection, the principle of contact failure detection of the potentiometer 1 according to the present invention will be described. The opening and closing control of the guide vane of the water turbine is usually
This is done using a hydraulic or electric servo motor, whichever servo
Even if the motor is used, the maximum opening / closing speed of the guide vane during opening / closing control is uniquely determined by the servo motor used. In this case, the sliding contact 1b of the potentiometer 1 that generates the opening signal of the guide vane slides on the sliding resistance 1a mechanically interlocking with the opening / closing operation of the guide vane. Therefore, the maximum moving speed of the sliding contact 1b is determined by the guide base.
It is proportional to the maximum opening / closing speed. Accordingly, the maximum change width of the opening signal of the guide vane obtained from the potentiometer 1 within a predetermined constant time also becomes a constant value.

When a poor contact occurs in the potentiometer 1, the guide vane opening signal obtained from the poor contact is usually higher than the correct value. The present invention has been made paying attention to this point, and the guide vanes at the start time point and the end time point (before and after) of this constant time are set at predetermined constant times during the opening / closing control of the guide vanes. -The difference between the two opening signals of the vane is obtained, and when the difference becomes larger than the maximum change width of the opening signal of the guide vane within the fixed time, it is determined that the potentiometer has poor contact. To do.

Next, the contact failure detection operation of the device of the present invention to which the above detection principle is applied will be described with reference to FIGS.
In FIG. 1, the sliding contact 1b of the potentiometer 1 is
Interlocked with the opening / closing control of a guide vane (not shown), the slide resistor 1a is rotated while sliding on the slide resistor 1a, and an output 1A corresponding to the opening of the guide vane is generated. A control power supply P is connected to the converter 2, and the input 1A is converted into a value suitable for instructing the opening degree indicator 2P of the guide vane to generate an output 2A. Output 2A
Are input to the previous value memory circuit 7 and the adder 8 that constitute the contact indicator D of the potentiometer 1 and the opening indicator 2P, respectively. The opening indicator 2P indicates the opening of the guide vane. To do.

The contact failure detector D is processed by software of a microprocessor (not shown), and the contact failure detection operation has a contact failure detection cycle (for example, 1 Sec as one detection cycle) which is the above-mentioned predetermined fixed time. ) Every time. In general, poor contact often occurs locally. Therefore, a case where the poor contact occurs will be described below as an example. FIG. 2 shows a contact failure detector D whose horizontal axis is the time axis.
Is a flow chart showing an example of the input and output waveforms between the respective constituent elements, and the above-mentioned one cycle is defined by the alternate long and short dash line parallel to the vertical axis.

FIG. 2A shows the output 2A of the converter 2, in which the opening control of the guide vane at a predetermined speed is started at time t1, is ended at time t3, and is near the time t2. Until then, there was no contact failure of the potentiometer 1, and local contact failure occurred mainly at time t2, and the output value was 2A.
Indicates that it has protruded. (The broken line indicates the output value 2A when the contact failure does not occur.) This output 2A is input to the previous value memory circuit 7 and is also added to the adder 8 as one input (current value) thereof.

The previous value memory circuit 7 outputs the output 2 of the converter 2 at the beginning of a contact failure detection cycle (hereinafter referred to as a cycle).
The value of A is stored, and at the end of the cycle, the stored value is transferred (output) to the adder 8 as the previous value, and the output 2A of the converter 2 at the start of the next cycle is updated. It is stored as a value, and this operation is repeated for each cycle. FIG. 2C shows the waveform of the output 7A (previous value) of the previous value memory circuit 7 described above. A new output is generated from two cycles after the start time t1 of opening control of the guide vane, and this output is the other one. It is added to the adder 8 as an input (previous value).

As described above, one input (current value) to the adder 8 is the output 2A of the converter 2 (see FIG. 2).
(A)] is added, but the value actually adopted in the calculation as the current value is the value 2A 'at the beginning of the cycle. When this value 2A' is illustrated, the waveform shown in FIG. The output becomes new one cycle after the start time t1 of the opening control of the engine. In other words, it is equivalent to the value of FIG. 2B being input to the adder 8 as the current value. Further, the output 7A of the previous value memory circuit 7 [FIG. 2 (c)] is added to the adder 8 as the other input (previous value), and (current value-previous value) is calculated. This operation will be described with reference to FIG. 2 [FIG. 2 (b) -FIG. 2 (c)], and the difference 8A between both inputs [FIG. 2 (d)] is output and input to the absolute value circuit 9.

The absolute value circuit 9 calculates the absolute value of the input 8A by 9A.
It is output as [Fig. 2 (e)], and this output 9A is output from the comparator 1
Added as input to 0. The alternate long and short dash line parallel to the horizontal axis indicates the set value 9S.

In the comparator 10, a set value 9S determined in advance as described later is set as a reference value and compared with the input 9A, and the input 9A is larger than the set value 9S (9
If A> 9S), it is determined that the contact of the potentiometer 1 is poor, and a poor contact detection signal 10A having the waveform is output in FIG. 2 (f).

Here, the value of the set value 9S is at the starting point of the range in which the potentiometer 1 can operate at its maximum operating speed within one contact failure detection period which is a predetermined fixed time. It is a value obtained by adding an appropriate margin value to the absolute value of the difference between the output 2A of the converter 2 and the output 2A of the converter 2 at the end point of the range. Since the range in which the potentiometer can operate at its maximum operating speed (in this case, the maximum opening / closing control speed of the guide vanes) is determined as described above, the set value 9S can be easily determined. Needless to say.

The set value 9S determined as described above is
The reference value is preset in the comparator 10.
Further, the comparator 10 includes the converter 2 at the starting point within the range in which the potentiometer 1 operates within one cycle of contact failure detection.
Output 2A and output 2 of converter 2 at the end of the range
The absolute value 9A of the difference from A is added as an input for each cycle of contact failure detection, and compared with the set value 9S. And
If the potentiometer 1 is normal and no contact failure occurs, the input 9A will not exceed the set value 9S. However, contact failure occurs mainly at time t2,
Equivalently, when the resistance value of the potentiometer 1 increases, the output 2A of the converter 2 also increases around time t2 as shown by the solid line in FIG. 2 (a), and the input 9A of the comparator 10 is set. Value 9
It becomes larger than S, and the comparator 10 outputs the contact failure detection signal 10A at the start time of the cycle including the time t2.

In this way, contact failure can be detected over most of the range of use of the potentiometer, and the shorter the contact failure detection period, the wider the detection range, and substantially the potentiometer. -It is possible to detect poor contact in the entire range of the data.

[0025]

As described above, the present invention has been described in detail. According to the present invention, the start point and the end point (front and back) of the detection cycle are set for each contact failure detection cycle having a predetermined fixed period. Then, the absolute value of the difference between the outputs of the potentiometers is calculated, and the absolute value of the difference is the start and end points of the range in which the potentiometer can operate at its maximum operating speed within the above detection cycle ( (Before and after) and the absolute value of the difference between the respective outputs of the potentiometer at
When it exceeds the limit, it is determined that the contact of the potentiometer is poor, so a position detecting device equipped with a function capable of detecting the poor contact over substantially the entire range of the potentiometer is provided. There are advantages to be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

2-1 and 2-2 are diagrams showing output waveforms for explaining the operation of the present invention.

FIG. 3 is a block diagram showing an example of a conventional general potentiometer abnormality detection circuit.

[Explanation of symbols]

 1 ... Potentiometer, 2 ... Potentiometer converter, 7 ... Previous value memory circuit, 8 ... Adder, 9 ... Absolute value circuit, 10 ... Comparator.

Claims (1)

[Claims] 1. A position detecting device for detecting the position of the subject by using a potentiometer which operates in association with the movement of the subject and produces an output in response to the movement of the subject. For each contact failure detection cycle of the potentiometer whose cycle is a fixed time, the output of each potentiometer before and after this detection cycle is input, and the difference between both inputs is output. And the output of this adder, the absolute value circuit that outputs the absolute value of this input, and the output of this absolute value circuit are input, and this input is
A comparator that produces an output when the potentiometer exceeds the absolute value of the difference between the outputs of the potentiometers before and after the range in which the potentiometer can operate at its maximum operating speed within the detection cycle; Position detection device.