JP2014238411A - Distance measuring instrument and method for measuring distance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a distance measuring instrument and a method for enabling continuous distance measurement, easy handling and various usages by conquering defects of a dielectric sensor.SOLUTION: In the distance measuring instrument having a sensor and evaluation electronics, a method uses the distance measuring instrument in which the sensor has a resonator in the shape of a cavity resonator, and the cavity resonator.

Description

  The invention relates to a distance measuring device and a method for measuring a distance as described in the premise of claim 1.

  A conventional distance measuring device, preferably provided in the vicinity, operates under the use of inductive sensors, capacitive sensors, optical sensors or ultrasonic sensors. A calibration curve must be defined for measurement using an inductive sensor and the material of the object to be measured must be known. Furthermore, since the inductive sensor has a measurement range of 180 °, for example, the two sensors arranged side by side may affect each other, thereby changing the calibration curve of each sensor. Moreover, such sensors are only commercially available with a diameter of 4 mm (M4) or more.

  The disadvantage of measuring with inductive sensors is that the distance between the capacitor plates must be known accurately. Furthermore, the measurement is affected by air humidity, general electromagnetic compatibility or temperature. In order to be able to perform measurements regardless of these parameters, reference measurements would have to be made as needed, so that disturbing effects could be removed based on them.

  It is an object of the present invention to provide a distance measuring device and method that overcomes the above disadvantages and allows for continuous distance measurement, simple handling, and various applications.

  This object is achieved according to the invention by the technical features of the device as claimed in claim 1 and the technical features of the method as claimed in claim 21.

  In accordance with the present invention, the sensor has a resonator in the form of a cavity resonator. This measure achieves the advantage that a minimum, for example less than M4, configuration is feasible and thus the usability is increased by a factor of four. Based on the basic geometry of the cavity, the spacing between the sensors arranged in parallel can be kept small. This is because the sensor has a measuring range that is sharply limited on the sides, and therefore its measuring characteristics are not affected by sensors arranged in parallel. As an application, it is conceivable to use the distance measuring device according to the invention, for example in the direction detection of a movable object or in a space-saving assembly by parallel assembly.

  Furthermore, the sensor according to the present invention can be used as a switch that allows switching points to be changed without a new dimensional design or change of the sensor member or the addition of another electronic component. This achieves the advantage that the switching points can be adjusted to the respective needs, for example by software.

  In addition, the sensor according to the present invention can recognize an approaching object, a conductive object, or a dielectric object, and can measure the distance from the object with an accuracy in the micron range. This type of sensor can be used, for example, as a proximity switch or for continuous measurement of piston stroke or valve position at the turning points of pneumatic and hydraulic cylinders, or for measurement of pressure membrane expansion.

  In accordance with the present invention, assuming that the object is at least as large as the diameter of the cavity, the measurement distance does not depend on the object size in the case of a conductive object. In addition, it is generally possible to measure distances to conductive and dielectric objects.

  When this sensor is used as a switch, the present invention makes it possible to easily change the switching point, change the new dimension, or change the sensor member. Since the switching point can be adjusted by software, for example, it is possible to easily input a multi-switching point by appropriate software. This provides a much higher usage flexibility, for example for member dimension recognition, various machine configurations, cam rotation angle recognition, and the like. On the other hand, as described at the beginning, in an inductive sensor, a multi-switching point can be realized only at a very high cost.

  Based on the measuring method used in the distance measuring device according to the present invention, a plurality of switching points can also be coupled to each other via logic, and the measuring method functions continuously. This measuring method is advantageous, for example, when three switching points are required when querying a rotating cylinder.

  Based on a compact configuration, basic members can be used in all conventional housing configurations, for example for switch spacings of 0.6, 0.8, 1.0, 1.5, 2.0 mm or 5 mm Yes, thereby achieving cost savings and thus less logistics required.

  Other advantageous embodiments are described in the dependent claims.

  It has been found that it is advantageous if the resonator is a high-frequency resonator and the resonance frequency is preferably 1 to 100 GHz, in particular 20 to 30 GHz, depending on the object. Further, in certain uses, it is advantageous to tune the high frequency resonator at frequencies of 22-24 GHz and 24-26 GHz, or other ranges, preferably a 2 GHz bandwidth, or a bandwidth that is about 10 percent of the frequency used.

  If the distance measuring device according to the present invention is equipped with a resonator having a cylindrical shape and an open bottom surface facing the object, i.e. not metallized, the temperature dependence of the resonance frequency is eliminated.

If the cavity resonator is filled with, for example, a dielectric, preferably Al ₂ O ₃ , the entire distance measuring device can be made small.

It should be noted that in general, it is advantageous that the measurement range is as large as possible, but this means that the relative dielectric constant ε should be reduced. This is ideally achieved by not filling the cavity resonator, i.e. not being equipped with a dielectric. However, the disadvantage of this arrangement is that in this case the cavity resonator structure is large in order to achieve a large measuring range. However, when a dielectric is used, the structure of the cavity resonator is reduced in an approximately equal measurement range. However, care must be taken so that the dielectric constant of the dielectric does not become too large (preferably 10 or less). Otherwise, the loss will increase and the distance range will decrease. Further, when ceramic is used as a dielectric, it can be used at a fixed temperature up to 1000 ° C. and can be used for high dynamic pressure measurement in an internal combustion engine. Thus, the distance measuring device according to the present invention is pressure resistant and can therefore be used, for example, in a hydraulic cylinder.

  If the surface of the dielectric is covered with a thin gold film or sputtered except for the bottom facing the object, the function of temperature depends only on the temperature constant of the ceramic, for example, and the housing It has proved advantageous because it does not depend on it.

  The sensor member is made of a ceramic and a metal housing, and can be connected to the evaluation electronics via an appropriate high-frequency transmission path, for example, a hollow conductor. Based on this, the sensor member can be used for high temperature use up to about 1000 ° C., for example in an internal combustion engine.

  Regardless of the distance measurement, the distance measuring device can also be advantageously used to measure other physical values, such as pressure, force or mass, and material properties, such as loss factors of dielectric materials. In this case, the open side of the cavity resonator is closed with a test material at a fixed distance from the cavity resonator. In the case of a pressure sensor, it may be advantageous to provide a piezoelectric ceramic plate at a distance of zero. When pressure, force, or mass acts on a pressure ceramic, the piezoelectric ceramic changes its relative dielectric constant. This change in relative permittivity causes a displacement of the resonance frequency. By measuring the resonance frequency with the device technical and method technical features according to claim 1 or claim 21, the pressure, force or mass acting on the piezoelectric ceramic can be measured.

  If the dielectric is inserted into a metal housing, preferably made of Kovar or titanium, a suitable high temperature use is conceivable. In this case, the cavity resonator has high measurement accuracy even at high temperatures when not filled, and the expansion itself can be accurately controlled when filled.

  If the distance measuring device, in particular the resonator, preferably has a coplanar aperture coupler on the opposite side of the resonator object, based on this arrangement, the resonance frequency can be easily coupled at an appropriate point. Can be

  Depending on the operating mode of the distance measuring device, the coplanar aperture coupler can consist of one window each for the transmitter and receiver arranged in a circle (corresponding to the transmission mode) or coplanar aperture coupling The instrument consists of windows for transmitter and receiver (corresponding to operation in reflection mode).

  Alternatively, the distance measuring device, in particular the resonator, can have a microstrip transmission line for coupling. This microstrip transmission line is used in particular when it is advantageous to configure the evaluation electronics separately from the resonator, for example in applications where high temperatures are generated.

When the distance measuring device is operated in the H _0np mode, preferably in the H ₀₁₁ mode, the resonator can oscillate in the range of large resonance frequencies, and another mode is excited together to maintain large measurement accuracy. Never happen. Furthermore, there is an advantage that no wall flow flows along the edge between the mantle surface and the closed surface during the excitation of the H ₀₁₁ mode.

  Other advantageous configurations of the invention are described in the other dependent claims.

1 shows a cross-sectional view of a distance measuring device according to the present invention. 2 shows a rear view of the distance measuring device according to the invention shown in FIG. 1 shows a block diagram of a circuit of a distance measuring device according to the present invention. 6 shows reflection characteristics or transmission characteristics as a function of resonance frequency at various distances from the object of the distance measuring device according to the present invention. The graph of the relationship between the distance with a target object and the resonant frequency is shown. Fig. 5 shows the mode characteristics of a circular cylinder for dimensional design of a resonator of a distance measuring device according to the invention. Figure 7 shows another block diagram for another embodiment of a circuit of a distance measuring device according to the present invention. Fig. 4 shows different positionings of a special application of a distance measuring device according to the invention. Fig. 4 shows another possible application of the distance measuring device according to the invention. It shows yet another applicability of the distance measuring device according to the invention, for example for buffer inquiry. It shows the applicability for detecting the piston position in the valve. It shows another application possibility, for example pressure measurement by detection of membrane displacement. It shows another application possibility, for example pressure measurement due to change in dielectric constant due to mechanical loading. It shows another application possibility, for example pressure measurement due to change in dielectric constant due to mechanical loading. It shows another applicability of the distance measuring device according to the invention, for example in object surveying. It shows another applicability of the distance measuring device according to the invention, for example to a filling height sensor.

  Embodiments of the present invention will be described below in detail with reference to the drawings.

As shown in FIG. 1, the distance measuring device has a resonator in the form of a cavity resonator 1. The cavity resonator 1 is formed from a metal housing 5 preferably made of titanium or kovar. In this metal housing, which is preferably formed in a conical shape, a dielectric, for example in the form of a ceramic, for example Al ₂ O ₃ , or a flowable material, preferably air or an inert gas, for example a noble gas or nitrogen. Body 7 can be injected. As shown in FIG. 1, ceramics can be inserted into the housing. The dielectric 7 itself is metallized, for example gold-plated, except for the side that is open to the target. This achieves the advantage that the function of temperature depends only on the temperature constant of the dielectric 7 and not on the temperature constant of the metal housing.

  On the back side of the cavity resonator, the substrate 9, as a support for the coupling operation, for example in the form of a coplanar aperture coupler or microstrip transmission line and evaluation electronics active elements, or in the form of high frequency electronics, For example, ceramics are similarly positioned. Electromagnetic waves are coupled through this arrangement. This back side can be similarly gold plated and can support the entire high frequency electronics 11.

Based on the use of dielectric 7, the cavity resonator geometry can be reduced while maintaining equal transmission frequencies. As is generally known, the resonant frequency fr of a cylindrical Hmnp resonator is the nth zero (root) of the derivative of the Bessel function of order ε, μ, m, and the cavity resonator diameter D and It can be defined from the length L of the cavity resonator. The functional relationship between εμ (frD) ² and (D / L) ² is clearly shown in a so-called mode chart shown in FIG. Based on this so-called mode chart, a range in which other modes cannot propagate can be identified relatively easily. Another mode selection can be made by insulating the resonator cladding from the cylinder jacket corresponding to the open resonator in the H _0np mode. It has been found to be particularly advantageous if the cavity resonator is designed to be able to propagate the H _0np mode, preferably the H ₀₁₁ mode, as a wave form. This is because the wall flow does not flow along the edge between the mantle surface and the closing surface. Only the portion where the characteristic curve of the other mode does not occur around the H ₀₁₁₁ mode line shown in FIG. 5 is obtained, and other modes are also found in specific variations in mechanical resonator dimensions and frequency tuning. Not excited.

  FIG. 2 shows the back side of the cavity resonator 1 shown in FIG. Based on this figure, this figure can more clearly show the coupling of electromagnetic waves into the cavity, corresponding to coplanar aperture coupling. The back side of the cavity resonator is provided with a substrate 9, preferably ceramics. The outer surface of the substrate 9 is preferably gold-plated. Only the coupling openings 13 and 15 remain open in the cavity resonator 1. For example, an electromagnetic wave is supplied through the opening coupling portion at a location where the maximum magnetic field intensity has a half radius of the dielectric 7. The size of the joint openings 13 and 15 follows the dimensions of the dielectric 7. This size is about 0.3 mm × 0.2 mm for the diameter of the dielectric 7, for example, 6 mm. The electromagnetic wave itself is guided to the opening via a coplanar 50Ω transmission path and coupled into the opening 13 via a connection wire 17, for example, a 17.5 μm gold wire 17. In order to achieve an optimum fit, the connecting wire 17 can be closed on the opposite side by a transmission line structure.

With this arrangement, the cavity resonator 1 can be operated in both transmission mode and reflection mode. When the cavity resonator 1 is operated in the transmission mode, the electromagnetic wave is dissociated by the above-described coplanar coupler / dissociator at the second coupling portion opening 15. In the reflection mode, this exit is closed at 50Ω. As mentioned above, when the diameter of the dielectric 7 is relatively small, microstrip transmission line coupling can also be used advantageously. Similarly, on the back side, for example, an oscillator 19, for example a voltage controlled oscillator (VCO), a sensing diode 21 and a frequency divider are provided, which are connected to the evaluation electronics.

  FIG. 3 shows a schematic or block diagram of the function of an advantageous configuration of the distance measuring device according to the present application. Starting from the control and evaluation electronics, the lamp generator is operated via the lamp controller, so that the frequency of the transmission branch I is tuned. At the same time, the resonance detector connected to the detection diode, which is composed of, for example, a two-stage differentiator and a comparator provided on the second conductor via the reception branch path II, receives the video signal extracted from the reception branch path II. Is constantly monitored to see if it exhibits resonance. Resonance can be recognized by distinguishing it from steep non-resonance in the video signal of the receiving branch as the oscillator frequency increases (see FIG. 4). As soon as resonance is recognized by the control and evaluation electronics, the integrator that controls the lamp controller is stopped. The voltage adjusted in this way is held stably and the oscillator frequency divided by the frequency divider 23 is determined by a digital counter in the evaluation electronics.

  With this configuration, the resonance frequency in the cavity resonator is measured. Since the resonance frequency in the cavity resonator depends on the distance from the object (see FIG. 5), the distance can be directly estimated by defining the resonance frequency. The new resonance frequency is obtained by changing the resonance frequency until the resonance frequency and the transmission frequency match. At this point, an output depression is confirmed in the detection diode. In parallel with this, the transmission frequency is obtained at the divider outlet of the frequency divider 23. The measurement accuracy of the distance to the object depends on how fast the transmission frequency is and how much accuracy is specified. The definition of the distance with a measurement accuracy of 1 μm typically requires the accuracy of defining a frequency of at least 0.5 MHz at a frequency of 26 GHz at a distance of 0.5 mm.

  The measured values shown in FIGS. 4 and 5 serve to explain the function of the distance measuring device according to the present application.

  As can be clearly seen in FIG. 4, the reflection and transmission characteristics, shown as a function of the resonance frequency at various distances to the object, are distinct signals that occur when the resonance frequency is reached at a given distance from the object. Indicates depression. Furthermore, it is recognized again that the signal depression between the reflection characteristics and the transmission characteristics is clearly consistent.

  FIG. 5 shows the relationship between the distance and the resonance frequency. It can clearly be seen that at a relatively small distance, a clearer resonance frequency displacement occurs, which is measured in particular in an object positioned just before the cavity resonator. What is noticeable in this case is that the resonance frequency decreases as the distance to the object increases. On the other hand, in the case of a dielectric object, the resonance frequency increases as the distance from the object increases. Therefore, the change in direction of the resonance frequency depends on the relative dielectric constant of the object. This effect can be used to measure or define the physical magnitude of pressure, force and mass. The open side of the cavity resonator is preferably closed by piezoelectric ceramics. In this case, when pressure, force or mass is applied to the piezoelectric ceramic, this changes the dielectric constant accordingly. This change in relative permittivity displaces the resonant frequency of the cavity resonator. In this case, according to each dielectric constant, it moves on the y-axis (x = 0) according to FIG.

  FIG. 6 shows a general overview of the modes to be excited in a circular cylinder. An appropriate mode (TM = E field component and TE = H field component) can be selected based on this circuit diagram according to the size of the cylinder.

  For the distance definition in the micron range, another configuration of evaluation electronics can be used in the distance measuring device according to the present application, which will be described in detail on the basis of the block diagram shown in FIG.

  The essential difference from the distance measurement described above is that the divided oscillator frequency is not used directly as a result value, but in a so-called phase-locked loop (PLL) frequency and phase control loop. In this case, the target frequency is adjusted to a frequency that enters the control loop as a guide value via a direct digital synthesizer (DDS). When the video signal taken out from the reception branch path II satisfies the resonance condition, the resonance frequency and thus the distance from the target are already known in the microcontroller built in the evaluation electronics. In the microcontroller embedded in the evaluation electronics, omitting the measurement time for the oscillator frequency, for example by using a resonance sequence algorithm, the cycle time can be significantly reduced, thereby significantly increasing the measurement accuracy. it can.

  In the following, the possibility of using the distance measuring device according to the present application will be described with an example of a high-frequency proximity sensor based on some application fields.

A. FIG. 8 shows a possible sensor arrangement for querying the piston position of a linear cylinder drive by means of a high-frequency proximity sensor according to the distance measuring device according to the present application.

  FIG. 9 shows a possible sensor arrangement for querying the position of the rotary drive by means of a high-frequency proximity sensor for rotary drive. Since such a high-frequency proximity switch has a very thin structure, when there are a plurality of switching points, a plurality of positions having sensor members can be realized. In this case, the adjustment can be made, for example, via a potentiometer or teach-in logic.

B. Detecting the shock absorber piston position FIG. 10 shows a schematic structure of a shock absorber incorporating a high frequency proximity sensor.

  In general, the principles of the present invention can be applied to valves having movable mechanical members (see FIG. 11). In this case, the valve flow possibility is controlled by changing the position of the mechanical member. Conventional rotational interrogation has been realized in a pneumatic device by a magnetic field response sensor that reacts to a permanent magnet on a valve piston or ram. However, in that case, in order to obtain an inexpensive solution, it has been shown that only a discontinuous position range can be detected by a sensor that is assembled at a fixed position and calibrated to a position to be grasped. Since hydraulic devices typically use ferromagnetic materials, the potential for magnetic inquiry is limited.

C. FIG. 12 shows the possibility of various pressure measurements, that is, relative pressure measurement or differential pressure measurement. In this particular application, a film approaching or leaving the high frequency proximity sensor is detected at that distance. Compared to today's schemes, such as piezoresistive strain gauges (DMS) or silicon elements, the device according to the present application has the advantage that sensitive electronics are external to the pressure measuring cell.

D. Pressure measurement of the dielectric constant, preferably piezoelectric ceramics, due to changes in the mechanical load. Indirect regulation of pressure, for example by approaching or separating membranes via distance measurement, is a force for pressure measurement under very high pressures. This is not suitable because it occurs.

  According to this embodiment, the measurement of the physical value of distance is replaced by a pressure-dependent relative permittivity. In this case, the cavity resonator filled with the dielectric is preferably closed on the open side by piezoelectric ceramics (see FIG. 13). The piezoelectric ceramic is fixedly assembled to a sensor used in the distance measuring device according to the present application. In this case, a fixed resonance frequency is generated when the sensor is turned on. Now, when the piezoelectric ceramic is loaded with pressure P, and hence with force, on the side opposite to the sensor inside the pressure measurement cell, the relative dielectric constant of the piezoelectric ceramic changes. As a result of this change, the resonance frequency is displaced. Evaluation of this frequency change, and hence conversion to a corresponding pressure change, is performed according to the method described in connection with FIGS.

  The entire cavity of the resonator can also be filled with piezoelectric ceramics in this application (see FIG. 13b).

  The great advantage of this arrangement with a conventional DMS or capacitive pressure measuring cell is its high mechanical stability. Piezoelectric ceramics are mechanically supported by the resonator, particularly when the resonator housing extends conically and the ceramic supported on the inside provides the necessary stability for high pressure use.

  Another advantage over conventional measurement methods is that calibration or high precision is not required for assembly into the pressure measurement cell, and sensitive electronics exist outside the pressure measurement cell.

E. Object Surveying In the object surveying shown in FIG. 14, the movement of the measuring tip approaching or moving away from the high-frequency proximity sensor is measured by the object. Thereby, based on the distance measuring device according to the present application, measurement in the micron range can also be performed.

F. Filling height sensor or monitor The applicability shown in FIG. 15 relates, for example, to a filling height sensor. 15a, 15b, and 15c show various assembly positions of the high-frequency proximity sensor. In the case of FIGS. 15a and 15b, the distance of the level to be measured is measured in a separate filling tube arranged externally or internally. In the arrangement shown in FIG. 15c, a high frequency proximity sensor is used externally to monitor a corresponding level of maximum fill height. This advantageously ensures monitoring of the maximum filling height or a pre-adjusted detection range. In this case, a switch signal is displayed when the maximum filling height is below or outside the adjusted sensing range.

  On the other hand, when the high frequency proximity switch is used externally as a filling height switch, it can be indicated that it exceeds or falls below a predetermined filling height via a corresponding switch function. This external arrangement eliminates the need for expensive integration costs. The scheme shown in FIG. 14c can be used to adapt to existing maintenance equipment having a high frequency transmission shell.

  Here, the distance measuring device according to the present application can be used in any place where a distance measuring device down to the micron range is required in addition to the above-described application examples.

Claims (11)

The following configuration:
(A) a first surface facing the object to be measured, including a housing and a dielectric for detecting and generating electromagnetic waves in a space where the target conductor exists, and a metallized second surface; And (b) an electronic unit comprising a substrate attached to the resonator and suitable for coupling with electromagnetic waves generated by the resonator,
A device for measuring the distance to a target conductor. The apparatus of claim 1, wherein
The device wherein the resonator has a cylindrical shape and the first surface is at a first end of the cylindrical resonator. The apparatus of claim 1, wherein
The device wherein the resonator has a resonant frequency that is between 20 and 30 GHz. The apparatus of claim 1, wherein
The device wherein the resonator comprises a fluid material selected from the group of air and inert gas. The apparatus of claim 1, wherein
The device, wherein the resonator is a cavity resonator comprising a dielectric material suitable for changing the relative permittivity when loaded with pressure. The apparatus of claim 5, wherein
The cavity resonator includes a dielectric material having a property of changing a relative dielectric constant when loaded with pressure. The apparatus of claim 1, wherein
The second surface is a distance measuring device that is metallized with gold. The apparatus of claim 1, wherein
The electronics unit comprises a coplanar aperture coupler having a connection wire, the connection wire terminating in the housing. The apparatus of claim 1, wherein
The connecting wire and the resonator are devices that enable a H _0np mode as a wave type mode. The apparatus of claim 1, wherein
The electronics unit includes a microstrip transmission line for connecting wires, the microstrip transmission line terminating in the housing. The apparatus of claim 1, wherein
The electronics unit is a device containing a piezoelectric ceramic material.

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