CN111059994A - Displacement sensor - Google Patents
Displacement sensor Download PDFInfo
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- CN111059994A CN111059994A CN201910985095.XA CN201910985095A CN111059994A CN 111059994 A CN111059994 A CN 111059994A CN 201910985095 A CN201910985095 A CN 201910985095A CN 111059994 A CN111059994 A CN 111059994A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
- G01B7/02—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
- G01B7/02—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness
- G01B7/023—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness for measuring distance between sensor and object
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D3/00—Indicating or recording apparatus with provision for the special purposes referred to in the subgroups
- G01D3/02—Indicating or recording apparatus with provision for the special purposes referred to in the subgroups with provision for altering or correcting the law of variation
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
- G01D5/14—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage
- G01D5/20—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature
- G01D5/2006—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature by influencing the self-induction of one or more coils
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Abstract
本公开涉及一种位移传感器，提高位移信号相对于被测定物的位移的线性度。位移传感器(1)具备：线圈(2)，通过对线圈(2)提供交流电流来使线圈(2)产生交流磁场，生成与根据被测定物的位置的位移而在所述被测定物中感应出的涡流相应的输出；温度测量器(9)，其测量所述线圈(2)周边的实际温度；以及位移信号生成部(6)，其使用所述线圈(2)周边的温度为规定值时的所述线圈(2)的输出与根据所述线圈(2)的输出求出的表示被进行温度校正后的所述被测定物的位置的位移的校正位移信号之间的相关关系，输出与所述实际温度及所述线圈(2)的输出对应的校正位移信号，来作为表示所述被测定物的位置的位移的位移信号。
The present disclosure relates to a displacement sensor, which improves the linearity of the displacement of the displacement signal relative to the displacement of the measured object. The displacement sensor (1) includes a coil (2), which generates an alternating magnetic field by supplying an alternating current to the coil (2), and generates and induces a displacement according to the position of the object to be measured in the object to be measured. a temperature measuring device (9), which measures the actual temperature around the coil (2); and a displacement signal generator (6), which uses the temperature around the coil (2) as a predetermined value The correlation between the output of the coil (2) and the corrected displacement signal obtained from the output of the coil (2) and indicating the displacement of the temperature-corrected position of the object to be measured, output A corrected displacement signal corresponding to the actual temperature and the output of the coil (2) is used as a displacement signal representing the displacement of the position of the object to be measured.
Description
Technical Field
The present application is based on Japanese patent application (Japanese patent application 2018-195357, filing date: 2018/10/16) and enjoys priority benefits based on the application. The entire contents of this application are included by reference thereto.
The present invention relates to a displacement sensor for detecting a gap, which is a distance from a measurement object, in a non-contact manner.
Background
A displacement sensor using a coil includes an oscillator for causing an alternating current to flow through the coil, and a circuit for detecting a signal change caused by a change in impedance of the coil. After the oscillation signal of the oscillator is converted into a dc signal by the rectifier, a signal that linearly changes according to the gap between the objects to be measured is generated by the linearizer (see patent documents 1 and 2).
It is known that the impedance of a coil varies with temperature. Therefore, in patent document 1, the amplitude level of the oscillation signal output from the oscillator having the coil is corrected in accordance with the temperature. In addition, in patent document 2, the output of the linearizer is corrected by a correction value according to the temperature.
Documents of the prior art
Patent document
Patent document 1: japanese patent laid-open publication No. 2015-137888
Patent document 2: japanese laid-open patent publication No. 8-271204
Disclosure of Invention
Problems to be solved by the invention
In patent document 1, temperature correction is performed at a stage before rectification by a rectifier. However, the rectifier also has an offset variation due to temperature, and the electric characteristics of the linearizer may vary depending on temperature. Therefore, in the technique disclosed in patent document 1, the output signal of the displacement sensor may have a large temperature dependency.
Further, since the signal frequency on the front stage side of the rectifier is high, the influence of stray capacitance is likely to be received, and when a temperature correction circuit is provided on the front stage side of the rectifier, heat generation is likely to occur due to the high signal frequency, which may adversely affect the accuracy of temperature correction.
On the other hand, in patent document 2, the output voltage of the R-V converter is added to the output voltage of the linearizer to perform the correction process, but if only the addition process is performed, the correction process can be performed only with a specific displacement subjected to the addition process, and the wide-range input/output characteristics of the linearizer cannot be linearized.
In addition, when temperature correction is performed on the output of the linearizer as in patent document 2, a signal that is not subjected to temperature correction is input to the linearizer. Particularly in a high-temperature region, there are concerns that: since the attenuation of the signal from the rectifier circuit increases, even if the temperature correction is performed on the output of the linearizer to which such an attenuation signal is input, the temperature correction cannot be performed to such an extent that the signal attenuation amount can be compensated.
In both patent document 1 and patent document 2, it is considered that the correction processing is performed by a combination of electric components, and there is a problem that the maintenance is poor because the change of the electric characteristics due to the environmental conditions such as temperature and the deterioration with age is easily generated and the failure is easily caused.
The invention provides a displacement sensor which can reduce temperature dependence as much as possible while reducing component cost so as to improve linearity of displacement signals relative to displacement of a measured object.
Means for solving the problems
In order to solve the above-described problems, one aspect of the present invention provides a displacement sensor including: a coil that generates an alternating magnetic field by supplying an alternating current to the coil, and generates an output corresponding to an eddy current induced in a measurement object according to a displacement of a position of the measurement object;
a temperature measuring device that measures an actual temperature around the coil; and
and a displacement signal generating unit that outputs a corrected displacement signal corresponding to the actual temperature and the output of the coil as a displacement signal indicating a displacement of the position of the object, using a correlation between the output of the coil when the temperature around the coil is a predetermined value and a corrected displacement signal indicating a displacement of the position of the object after temperature correction obtained from the output of the coil.
The temperature measuring device may further include an interpolation processing unit that interpolates a correction displacement signal corresponding to the actual temperature measured by the temperature measuring device based on a correlation between the output of the coil at least one temperature and the correction displacement signal,
the displacement signal generation unit outputs a corrected displacement signal interpolated by the interpolation processing unit as the displacement signal.
The interpolation processing unit may interpolate the correlation so that the correction displacement signal changes linearly with respect to a change in the output of the coil, thereby generating a new correlation.
The interpolation processing unit may generate the correlation at an intermediate temperature between the two temperatures based on a correlation between the correction displacement signal and the output of the coil at least two temperatures different from each other.
The present invention may further include: a substrate on which the displacement signal generating unit is mounted; and
a substrate temperature measuring device that measures a temperature of the substrate,
the interpolation processing unit interpolates the correlation based on the temperature around the coil measured by the temperature measuring device and the temperature of the substrate measured by the substrate temperature measuring device.
The present invention may further include: a first correlation storage unit that stores a first correlation between the output of the coil and the correction displacement signal at a first temperature;
a second correlation storage unit that stores a second correlation between the output of the coil and the correction displacement signal at a second temperature different from the first temperature,
the interpolation processing unit generates the second correlation by interpolation processing of the first correlation while the displacement sensor performs measurement using the first correlation, and stores the second correlation in the second correlation storage unit,
the displacement signal generation unit generates the correction displacement signal based on the second correlation relationship when the temperature measured by the temperature measuring device becomes the second temperature.
The present invention may further include: a first correlation storage unit that stores a first correlation between the output of the coil and the correction displacement signal at a first temperature; and
a second correlation storage unit that stores a second correlation between the output of the coil and the correction displacement signal at a second temperature different from the first temperature,
when the temperature measured by the temperature measuring device changes from the first temperature to a second temperature while the displacement sensor performs measurement using the first correlation, the interpolation processing unit generates the second correlation by interpolation processing of the first correlation, and stores the second correlation in the second correlation storage unit.
The apparatus may further comprise a self-excited oscillation circuit that generates the alternating current by performing an oscillation operation using an impedance of the coil and outputs an oscillation signal,
the oscillation level of the self-oscillation circuit changes under the influence of a change in impedance of the coil caused by eddy currents generated in the object.
ADVANTAGEOUS EFFECTS OF INVENTION
According to the present invention, the component cost can be reduced, and the linearity of the displacement signal with respect to the displacement of the object to be measured can be improved.
Drawings
Fig. 1 is a block diagram showing a schematic configuration of a displacement sensor according to a first embodiment.
Fig. 2 is a functional block diagram showing an internal configuration of a control unit that performs the first interpolation process.
Fig. 3A is a graph showing correlation data at a temperature T1.
Fig. 3B is a graph showing correlation data at a temperature T2.
Fig. 3C shows the correlation data after the interpolation processing.
Fig. 4 is a flowchart showing a processing procedure of the first interpolation processing.
Fig. 5 is a functional block diagram showing an internal configuration of a control unit that performs the second interpolation process.
Fig. 6A is a diagram for explaining an outline of the second interpolation processing performed by the interpolation processing unit in fig. 5.
Fig. 6B is a view subsequent to fig. 6A.
Fig. 7 is a flowchart showing a processing procedure of the second interpolation processing.
Fig. 8 is a functional block diagram showing an internal configuration of a control unit that performs the third interpolation process.
Fig. 9A is a diagram for explaining an outline of the second interpolation processing performed by the interpolation processing unit in fig. 8.
Fig. 9B is a view subsequent to fig. 9A.
Fig. 10 is a flowchart showing a processing procedure of the third interpolation processing.
Fig. 11 is a flowchart illustrating an example of the processing operation by the control unit according to the first embodiment.
Detailed Description
The following describes embodiments of the present invention in detail.
(first embodiment)
Fig. 1 is a block diagram showing a schematic configuration of a displacement sensor 1 according to a first embodiment. The displacement sensor 1 shown in fig. 1 includes a coil 2, an oscillator 3, a rectifier 4, an a/D converter 5, a control unit (displacement signal generating unit) 6, a D/a converter 7, an output amplifier 8, and a temperature measuring instrument 9.
The oscillator 3 is constituted by, for example, a self-excited oscillation circuit. Compared with the independent-excitation type oscillation circuit, the self-excitation type oscillation circuit can simplify the circuit structure and reduce the installation area and the component cost. Further, since resonance of the coil is utilized, there is also an advantage that a change in the oscillation signal level accompanying a change in the distance can be increased. The specific circuit configuration of the self-excited oscillation circuit is not particularly limited, and, for example, a colpitts oscillation circuit can be applied.
The oscillator 3 incorporates a resonance circuit formed by the coil 2 and a capacitor not shown. An alternating current of a resonance frequency flows through the coil 2. As a result, the coil 2 generates a magnetic flux corresponding to the alternating current, and an eddy current is generated in the object to be measured disposed in the vicinity of the coil 2 due to the magnetic flux. When an eddy current is generated in the object to be measured, the impedance of the coil 2 changes under the influence of the eddy current, and the signal level of the oscillation signal of the oscillation circuit also changes. In this manner, an alternating current is supplied to the coil 2 to generate an alternating magnetic field in the coil 2, thereby generating an output corresponding to an eddy current induced in the object to be measured in accordance with the displacement of the position of the object to be measured.
Since eddy current is not generated when the object to be measured is an insulator, the object to be measured, which can detect displacement, that is, a gap by using the displacement sensor 1 of fig. 1, is limited to a conductor. The object to be measured may be a conductive body, and may be a non-magnetic body or a magnetic body.
The rectifier 4 rectifies the oscillation signal of the oscillator 3, i.e., the output of the coil 2, and converts the rectified signal into a direct current signal. The a/D converter 5 converts the direct current signal output from the rectifier 4 into a digital signal. The temperature measurer 9 measures the actual temperature of the periphery of the coil 2. When the displacement sensor 1 of fig. 1 is used to measure the position of the valve of the engine, for example, the temperature around the coil 2 may be high enough to exceed 100 ℃. As described above, the impedance of the coil 2 varies depending on the temperature, resulting in a variation in the output signal of the displacement sensor 1. Therefore, it is desirable to measure the temperature of a place as close to the coil 2 as possible under the usage environment of the displacement sensor 1. The temperature measuring device 9 may measure the temperature of the coil 2 itself, or may measure the temperature in the vicinity of the coil 2.
The control unit 6 outputs a corrected displacement signal corresponding to the actual temperature and the output of the coil 2 as a displacement signal indicating the displacement of the position of the object to be measured, using the correlation between the output of the coil 2 when the temperature around the coil 2 is a predetermined value and the corrected displacement signal indicating the displacement of the position of the object to be measured after temperature correction obtained from the output of the coil 2. More specifically, the control unit 6 outputs, as a displacement signal indicating the displacement of the position of the object to be measured, a corrected displacement signal corresponding to the actual temperature measured by the temperature measuring instrument 9 and the output of the coil 2 based on the correlation between the output of the coil 2 at each of the plurality of temperatures and the corrected displacement signal indicating the displacement of the position of the object to be measured after the temperature correction obtained from the output of the coil 2. The control unit 6 generates the displacement signal by software processing, and for example, reads and executes the program stored in the program storage unit 10 to perform the above-described signal processing, thereby generating the displacement signal. More specifically, the Control Unit 6 may be constituted by an MCU (Micro Control Unit: microcontroller), an MPU (Micro Processing Unit: microprocessor), or the like that executes the program.
The control unit 6 incorporates or is connected to a correlation storage unit 11 and an interpolation processing unit 12. Note that, in fig. 1, an example is shown in which the correlation storage unit 11 and the interpolation processing unit 12 are built in the control unit 6, and at least one of the correlation storage unit 11 and the interpolation processing unit 12 may be provided separately from the control unit 6. The correlation storage unit 11 stores correlation data between the digital signal corresponding to the output of the rectifier 4 and the correction displacement signal for each of the plurality of temperatures of the coil 2. When storing the correlation data in the correlation storage unit 11, the gap between the coil 2 and the object to be measured is varied in a plurality of ways in a state where the coil 2 is set at a certain temperature, digital signals corresponding to the output signals of the rectifier 4 at each gap are detected, and the correlation data between the output signal of the rectifier 4, which is the output of the coil 2, and the correction displacement signal, is generated so that the correction displacement signal at each gap linearly varies with respect to the gap. The temperature of the coil 2 is varied in a plurality of ways, and such correlation data is generated for each temperature and stored in the correlation storage unit 11.
Instead of storing the correlation data in the correlation storage unit 11, the control unit 6 may provide a functional expression indicating the correlation, and provide the functional expression with an input parameter corresponding to the output of the rectifier 4 to perform arithmetic processing to obtain a corrected displacement signal.
The interpolation processing unit 12 interpolates the correction displacement signal corresponding to the actual temperature measured by the temperature measuring instrument 9. That is, the interpolation processing unit 12 interpolates the correlation data stored in the correlation storage unit 11 based on the actual temperature measured by the temperature measuring device 9. The interpolation processing unit 12 may generate a correlation at an intermediate temperature between two temperatures based on a correlation between the correction displacement signal and the output of the coil at least two temperatures different from each other. As described later, a variety of interpolation processes can be considered by the interpolation processing unit 12. The correlation data newly generated by the interpolation processing unit 12 by performing the interpolation processing is stored in the correlation storage unit 11, for example. Alternatively, the correlation data newly generated by the interpolation processing unit 12 is stored separately from the correlation storage unit 11.
The control unit 6 outputs the correction displacement signal interpolated by the interpolation processing unit as a displacement signal. More specifically, the control unit 6 generates a correction displacement signal corresponding to the output signal of the rectifier 4 at the actual temperature measured by the temperature measuring instrument 9 based on the correlation data newly generated by the interpolation processing unit 12 through the interpolation processing. When the correlation data does not include data corresponding to the output signal of the rectifier 4, a correction displacement signal is generated by interpolation processing using data close to the output signal of the rectifier 4.
Next, the interpolation process performed by the control unit 6 will be described in detail. A variety of interpolation processes can be considered by the interpolation processing unit 12 in the control unit 6. Next, representative first to third interpolation processes will be described in order. The interpolation processing unit 12 may adopt any one of the first to third interpolation processes shown below.
Fig. 2 is a functional block diagram showing an internal configuration of the control unit 6 that performs the first interpolation process. The control unit 6 in fig. 2 includes the correlation storage unit 11, the interpolation processing unit 12, and the data output unit 14. The data output unit 14 outputs, as a displacement signal, a corrected displacement signal generated based on the correlation data obtained by the interpolation processing performed by the interpolation processing unit 12.
Fig. 3A, 3B, and 3C are diagrams illustrating an outline of the first interpolation process performed by the interpolation processing unit 12 in fig. 2. Fig. 3A and 3B show an example of the correlation data stored in advance in the correlation storage unit 11, where fig. 3A shows correlation data cor1 at a temperature T1, and fig. 3B shows correlation data cor2 at a temperature T2.
As shown in fig. 3C, the interpolation processing unit 12 performs interpolation processing for proportionally distributing the correlation data cor1 of fig. 3A and the correlation data cor2 of fig. 3B based on the temperature around the coil 2 measured by the temperature measuring instrument 9, thereby generating new correlation data cor 3.
Based on the correlation data cor3, the control unit 6 generates a correction displacement signal corresponding to the output signal of the rectifier 4 at the temperature around the coil 2 measured by the temperature measuring instrument 9.
Fig. 4 is a flowchart showing a processing procedure of the first interpolation processing. First, the correlation storage unit 11 stores correlation data between the output of the rectifier 4 and the correction displacement signal at least for two temperatures (step S1). Next, as shown in fig. 3A and 3B, two kinds of correlation data cor1 and cor2 regarding different first and second temperatures are stored in the correlation storage unit 11. In the following description, the correlation data at the first temperature is referred to as first correlation data cor1, and the correlation data at the second temperature is referred to as second correlation data cor 2.
Next, based on the first correlation data cor1 at the first temperature, a correction displacement signal corresponding to the output signal of the rectifier 4 is acquired, and based on the second correlation data cor2 at the second temperature, a correction displacement signal corresponding to the output signal of the rectifier 4 is acquired (step S2).
Here, when data corresponding to the output signal of the rectifier 4 does not exist in either the first correlation data cor1 or the second correlation data cor2, the correction displacement signal may be generated by interpolation processing using data in the vicinity of the output signal of the rectifier 4.
Next, new correlation data cor3 is generated by interpolation processing using the correction displacement signal acquired using the correlation data cor1 at the first temperature and the correction displacement signal acquired using the second correlation data cor2 at the second temperature, and a correction displacement signal corresponding to the actual temperature measured by the temperature measuring instrument 9 is generated based on the correlation data cor3 (step S3). For example, if the temperature measured by the temperature measuring instrument 9 is an intermediate temperature between the first temperature and the second temperature, the average value of the correction displacement signal obtained based on the first correlation data cor1 and the correction displacement signal obtained based on the second correlation data cor2 may be a correction displacement signal corresponding to the output signal of the rectifier 4 at the temperature measured by the temperature measuring instrument 9.
Fig. 5 is a functional block diagram showing an internal configuration of the control unit 6 that performs the second interpolation process. The control unit 6 in fig. 5 includes a correlation storage unit 11, an interpolation processing unit 12, and a data output unit 14, and the correlation storage unit 11 includes a first correlation storage unit 11a and a second correlation storage unit 11 b. The first correlation storage 11a stores a first correlation between the output of the rectifier 4 and the correction displacement signal at the first temperature. The second correlation storage unit 11b stores a second correlation between the output of the rectifier 4 and the correction displacement signal at a second temperature different from the first temperature.
While the displacement sensor 1 performs measurement using the first correlation, the interpolation processing unit 12 in fig. 5 performs interpolation processing of the first correlation to generate a second correlation, and stores the second correlation in the second correlation storage unit 11 b. When the actual temperature measured by the temperature measuring instrument 9 becomes the second temperature, the control section 6 generates a correction displacement signal based on the second correlation relationship.
Fig. 6A and 6B are diagrams for explaining an outline of the second interpolation processing performed by the interpolation processing unit 12 in fig. 5. The solid line in fig. 6A is correlation data cor4 stored in advance in the first correlation storage 11a at a predetermined temperature T3. The broken lines of fig. 6A are correlation data cor5, cor6 at a temperature slightly shifted from the prescribed temperature T3 during the displacement measurement performed by the displacement sensor 1. The solid line of fig. 6B is the correlation data cor6 after the temperature change, and the dotted line of fig. 6B is the original correlation data cor 4.
Fig. 7 is a flowchart showing a processing procedure of the second interpolation processing. First, the correlation storage unit 11 stores correlation data cor4 between the output of the rectifier 4 and the correction displacement signal at a predetermined temperature (step S11). Using the correlation data, the displacement measurement process by the displacement sensor 1 is started (step S12). While this processing is continuously executed, correlation data cor5 and cor6 at a temperature slightly shifted from the predetermined temperature are generated by interpolation processing using the correlation data cor4 stored in the correlation storage unit 11 (step S13). When the new correlation data cor5 and cor6 are completed, the data is saved in the correlation storage 11 or another storage (step S14).
Then, when the actual temperature measured by the temperature measuring instrument 9 is the temperature of the correlation data cor5 or cor6 generated in steps S13 and S14, the control unit 6 acquires a correction displacement signal corresponding to the output signal of the rectifier 4 using the correlation data. Fig. 6B shows an example of the temperature corresponding to the correlation data cor 6.
Fig. 8 is a functional block diagram showing an internal configuration of the control unit 6 that performs the third interpolation process. The control unit 6 of fig. 8 has a similar configuration to the control unit 6 of fig. 5, but the correction displacement signal read out from the first correlation storage unit 11a is input to the data output unit 14, and one type of correlation data is stored in the second correlation storage unit 11b, which is different from the control unit 6 of fig. 5.
Fig. 9A and 9B are diagrams for explaining an outline of the third interpolation processing performed by the interpolation processing unit 12 in fig. 8. The solid line in fig. 9A is correlation data cor7 stored in advance in the first correlation storage 11a at a predetermined temperature T4. The broken line in fig. 9A is correlation data cor8 obtained by performing the third interpolation process on the correlation data cor 7. The solid line of fig. 9B is the correlation data cor8, and the dotted line is the original correlation data cor 7.
Fig. 10 is a flowchart showing a processing procedure of the third interpolation processing. First, the first correlation storage unit 11a stores correlation data cor7 between the output of the rectifier 4 and the correction displacement signal at a predetermined temperature (step S21). Using the correlation data cor7, the displacement measurement process by the displacement sensor 1 is started (step S22). When the actual temperature measured by the temperature measuring device 9 changes while the process is continuously executed, correlation data cor7 stored in the first correlation storage unit 11a is used to generate correlation data cor8 at the actual temperature measured by the temperature measuring device 9 by interpolation (step S23). When the new correlation data cor8 is completed, the correlation data cor8 is saved in the second correlation storage unit 11b (step S24). Then, the control unit 6 generates a correction displacement signal corresponding to the output of the rectifier 4 using the replaced correlation data. The correlation data cor7 stored in the first correlation storage 11a may be deleted, the correlation data stored in the second correlation storage 11b may be copied to the first correlation storage 11a, and the above-described processing in step S21 and subsequent steps may be repeatedly executed.
It is desirable that the interpolation processing unit 12 performs the interpolation processing so that the correction displacement signal linearly changes with respect to a change in the output of the rectifier 4, which is the output of the coil 2, when performing the first to third interpolation processing. This enables generation of a correction displacement signal that varies linearly with respect to the output of the rectifier 4.
Fig. 11 is a flowchart illustrating an example of the processing operation by the control unit 6 according to the first embodiment. When the coil 2 of the displacement sensor 1 is disposed in the vicinity of the object to be measured, the impedance of the coil 2 changes, the signal level of the oscillation signal of the oscillator 3 changes, and accordingly, the signal level of the dc signal output from the rectifier 4 also changes. The dc signal is converted into a digital signal by the a/D converter 5 and then input to the control unit 6 (step S31).
Before and after the process of step S31, the controller 6 acquires the temperature around the coil 2 measured by the temperature measuring instrument 9 (step S32). Next, the control unit 6 generates a correction displacement signal using the correlation data generated by the interpolation processing unit 12 performing any one of the first to third interpolation processes described above, based on the temperature around the coil 2 and the digital signal output from the rectifier 4 and digitally converted by the a/D converter 5 (step S33).
In the displacement sensor 1, the components other than the coil 2 are often mounted on a common substrate, and only the coil 2 is often disposed at a position distant from the substrate. In this case, there is a possibility that a temperature difference between the temperature around the coil 2 and the temperature of the substrate becomes large. In particular, when the temperature of the object to be measured becomes a high temperature exceeding several hundreds of degrees celsius, for example, when the position of the valve of the engine is detected, the temperature difference between the temperature around the coil 2 and the temperature around the substrate tends to increase. As described above, the impedance of the coil 2 changes according to the temperature of the coil 2, but the electrical characteristics of the circuit elements in the substrate also change according to the temperature of the substrate, and influence is exerted on the signal level of the correction displacement signal.
Therefore, when there is a possibility that the temperature around the coil 2 and the temperature around the substrate are different from each other, a substrate temperature measuring instrument 13 for measuring the temperature around the substrate may be provided in addition to the temperature measuring instrument 9 for measuring the temperature around the coil 2.
In this case, the control unit 6 generates a correction displacement signal corresponding to the temperature of the coil measured by the temperature measuring device 9 and the temperature of the substrate measured by the substrate temperature measuring device 13 based on the correlation between the output of the rectifier 4 and the correction displacement signal at a plurality of temperatures.
This makes it possible to generate a correction displacement signal corresponding to the displacement of the object to be measured, taking into account the temperature around the coil 2 and the temperature around the substrate, and to further improve the linearity of the displacement signal with respect to the displacement even when the temperature of the coil 2 and the substrate and the displacement of the object to be measured change.
As described above, in the present embodiment, the correction displacement signal corresponding to the output signal of the rectifier 4 at the actual temperature measured by the temperature measuring device 9 is generated based on the correlation between the output of the rectifier 4 and the correction displacement signal at a plurality of temperatures, and the correction displacement signal can be generated with high accuracy by software processing taking into account the actual temperature measured by the temperature measuring device 9. In the present embodiment, the correlation with respect to at least one temperature is used to obtain the correlation corresponding to the actual temperature measured by the temperature measuring instrument 9 by interpolation processing, and therefore, there is no need to prepare correlations with respect to a plurality of temperatures in advance. Therefore, the displacement signal can be generated over a wide temperature range.
Further, since the control unit 6 can be configured by one MCU or MPU, the hardware configuration can be simplified, and the component cost can be reduced. Further, by variously changing the processing operation of the control unit 6 by the improvement program, it is possible to relatively easily perform processing for further improving the linearity of the displacement signal with respect to the displacement of the object to be measured without changing hardware. It is desirable that the program storage section 10 be constituted by an electrically rewritable flash memory, EEPROM, or the like so that replacement of the program can be easily performed. In particular, when the displacement sensor 1 according to the present embodiment is used at high temperatures, it is more desirable to configure the correlation storage unit 11 and the program storage unit 10 using a nonvolatile memory having high data retention performance even at high temperatures.
The technical ideas of the above embodiments can be summarized as (1) to (8) below.
(1) A displacement sensor is provided with:
a coil that generates an alternating magnetic field by supplying an alternating current to the coil, and generates an output corresponding to an eddy current induced in a measurement object according to a displacement of a position of the measurement object;
a temperature measuring device that measures an actual temperature around the coil; and
and a displacement signal generating unit that outputs a corrected displacement signal corresponding to the actual temperature and the output of the coil as a displacement signal indicating a displacement of the position of the object, using a correlation between the output of the coil when the temperature around the coil is a predetermined value and a corrected displacement signal indicating a displacement of the position of the object after temperature correction obtained from the output of the coil.
(2) The displacement sensor according to (1),
further comprising an interpolation processing unit for interpolating a correction displacement signal corresponding to the actual temperature measured by the temperature measuring device based on a correlation between the output of the coil at least one temperature and the correction displacement signal,
the displacement signal generation unit outputs a corrected displacement signal interpolated by the interpolation processing unit as the displacement signal.
(3) The displacement sensor according to (2),
the interpolation processing unit interpolates the correlation so that the correction displacement signal changes linearly with respect to a change in the output of the coil, thereby generating a new correlation.
(4) The displacement sensor according to (2) or (3),
the interpolation processing unit generates the correlation at an intermediate temperature between at least two temperatures different from each other, based on a correlation between the output of the coil and the correction displacement signal at the two temperatures.
(5) The displacement sensor according to any one of (2) to (4), further comprising:
a substrate on which the displacement signal generating unit is mounted; and
a substrate temperature measuring device that measures a temperature of the substrate,
the interpolation processing unit interpolates the correlation based on the temperature around the coil measured by the temperature measuring device and the temperature of the substrate measured by the substrate temperature measuring device.
(6) The displacement sensor according to any one of (2) to (5), further comprising:
a first correlation storage unit that stores a first correlation between the output of the coil and the correction displacement signal at a first temperature; and
a second correlation storage unit that stores a second correlation between the output of the coil and the correction displacement signal at a second temperature different from the first temperature,
the interpolation processing unit generates the second correlation by interpolation processing of the first correlation while the displacement sensor performs measurement using the first correlation, and stores the second correlation in the second correlation storage unit,
the displacement signal generation unit generates the correction displacement signal based on the second correlation relationship when the temperature measured by the temperature measuring device becomes the second temperature.
(7) The displacement sensor according to any one of (2) to (5), further comprising:
a first correlation storage unit that stores a first correlation between the output of the coil and the correction displacement signal at a first temperature; and
a second correlation storage unit that stores a second correlation between the output of the coil and the correction displacement signal at a second temperature different from the first temperature,
when the temperature measured by the temperature measuring device changes from the first temperature to a second temperature while the displacement sensor performs measurement using the first correlation, the interpolation processing unit generates the second correlation by interpolation processing of the first correlation, and stores the second correlation in the second correlation storage unit.
(8) The displacement sensor according to any one of (1) to (7),
further comprising a self-excited oscillation circuit that generates the alternating current by performing an oscillation operation using an impedance of the coil and outputs an oscillation signal,
the oscillation level of the self-oscillation circuit changes under the influence of a change in impedance of the coil caused by eddy currents generated in the object.
The embodiments of the present invention are not limited to the above-described embodiments, and include various modifications that can be conceived by those skilled in the art, and the effects of the present invention are not limited to the above-described ones. That is, various additions, modifications, and deletions can be made without departing from the concept and spirit of the present invention derived from the contents and equivalents thereof defined in the claims.
Description of the reference numerals
1: a displacement sensor; 2: a coil; 3: an oscillator; 4: a rectifier; 5: an A/D converter; 6: a control unit; 7: a D/A converter; 8: an output amplifier; 9: a temperature measurer; 10: a program storage unit; 11: a correlation storage unit; 11 b: a second correlation storage unit; 12: an interpolation processing unit; 13: a substrate temperature measuring device.
Claims (8)
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| JP2018195357A JP7260871B2 (en) | 2018-10-16 | 2018-10-16 | Displacement sensor |
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| CN116772702A (en) * | 2023-08-24 | 2023-09-19 | 河南卫华重型机械股份有限公司 | Eddy current distance acquisition circuit |
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| CN111982042A (en) * | 2020-08-25 | 2020-11-24 | 淮阴工学院 | Displacement detection device for parameter measurement |
| CN113203350B (en) * | 2021-04-19 | 2022-03-11 | 浙江大学 | Linearization Method of Eddy Current Displacement Sensor Based on Inverse Function Piecewise Correction and Eddy Current Displacement Sensor Using This Method |
| KR102865583B1 (en) * | 2023-05-03 | 2025-09-26 | 김명광 | One-body type inductive displacement sensor apparatus |
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| KR20200042864A (en) | 2020-04-24 |
| JP2020063963A (en) | 2020-04-23 |
| JP7260871B2 (en) | 2023-04-19 |
| KR102275562B1 (en) | 2021-07-09 |
| CN111059994B (en) | 2023-03-03 |
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