DE102019118581A1 - Measuring device and method for creating a tank table - Google Patents

Abstract

The invention relates to a measuring device (11) and a corresponding method for creating a tank table (V (L)) for a product container (2). The measuring device (11) is based on a 3D camera (12) which is designed to record a matrix of distance values (dα, γ) based on one or more recordings of the lower portion of the inner wall of the container (2) and together with corresponding position data ([α; γ]) to be stored in an evaluation circuit. Using the evaluation circuit, a three-dimensional model of the corresponding sub-area (3) is generated from the distance values (dα, γ) and the corresponding position data ([α; γ]) in order to determine the tank table (V (L)) on the basis of the model create. The 3D camera (12) makes it possible according to the invention to record many distance values (dα, γ) in parallel, so that the three-dimensional model can be generated without a great deal of time. This means that a high-resolution tank table (V (L)) can be created within a short period of time. At the same time, by using a 3D camera (12), the measuring device (11) can be designed to be compact and thus, for example, as an integral part of a level measuring device (1).

Description

The invention relates to a measuring device and a method for creating a tank table.

In process automation technology, field devices are often used that are used to record or influence process variables. Appropriate sensors are used in the respective field devices to record the process variables. This enables the individual process variables such as level, flow, pressure, temperature, pH value, redox potential or conductivity to be recorded. A wide variety of such field device types are manufactured and sold by the Endress + Hauser company.

Contactless measuring methods have become established for measuring the level of products in containers, as they are robust and require little maintenance. In the context of the invention, the term “container” also includes containers that are not completely enclosed, such as basins. Another advantage of non-contact measuring methods is the ability to measure the level almost continuously. In the area of continuous level measurement, radar-based measurement methods are therefore predominantly used (in the context of this patent application, “radar” is defined as signals or electromagnetic waves with frequencies between 0.03 GHz and 300 GHz). The two common measuring principles are the pulse-transit time principle (also known under the term “pulse radar”) and the FMCW principle (“Frequency Modulated Continuous Wafe”).

A fill level measuring device that works according to the pulse transit time method is, for example, in the laid-open specification DE 10 2012 104 858 A1 described. With regard to a typical structure of FMCW-based level measuring devices, reference is made to the laid-open specification as an example DE 10 2013 108 490 A1 referenced.

Depending on the process plant, in addition to the fill level, it is primarily relevant to know the volume that the product currently occupies in the container. For example, with legal-for-trade fuel tanks, the first priority is the volume V of stored fuel of interest, and not the level of fuel in the container. To the volume V In order to be able to determine the filling level, the filling level is usually measured and converted into the stored volume of the filling material using a so-called tank table. The tank table describes ( V (L) the container geometry-dependent volume V of the filling material in the respective container depending on the filling level L. of the product in this container.

In order to create the tank table, it is necessary to find out the geometry of the tank interior. According to the state of the art, there are various possibilities for this: In the simplest case, the geometry of the container interior is known per se, so that the tank table can be calculated exclusively on the basis of the geometric relationships. For a cylindrical tank with a round base area A, the radius of which is exactly 10 m, the following tank table results according to A = π * r ² and V = A * L V (L) : Fill level L _i in meters Volume V in liters 0 0 0.01 3,141.8 0.1 31,418 0.5 157.090 1 314,800 2 628.360 5 1.5709 * 10 ⁶ ..... .....

As can be seen from this exemplary tank table, the resolution of the measurable volume depends V on the distance between the individual filling level steps between the respective table rows. The level measuring device or a higher-level unit can determine the volume accordingly on the basis of the level measured V if the associated tank table is stored there.

In practice, however, the base area A or the inner cross section of the container is not exactly known, or it deviates from the target values. In these cases, the tank table can be created approximately, for example, by measuring the outer wall of the container, the radius of the inner wall of the container being determined with the aid of the known container thickness. The tank table is created on the basis of this. Here, the diameter of the outer wall of the container is measured manually using a tape measure at various fill levels. This method, known as "strapping", is specified in the ISO 7507-4: 2010 series of standards.

The tank table can be created without contact using a laser tracker: For this purpose, the laser tracker is set up inside the container. The laser tracker then determines corresponding distance values from the laser tracker to the inner wall of the container in a predefined pattern together with corresponding angle settings.

On the basis of the measured distance values and the associated angle settings of the laser tracker, a Cartesian 3D model of at least the lower part of the inner wall of the container is created. The tank table can in turn be calculated on the basis of the 3D model. The maximum resolution with which the tank table ( V (L) ) the product volume V can reproduce depends on the number or density with which the measuring points are recorded by the laser tracker. This method of creating tank tables is defined, for example, in the series of standards ISO 7507-4: 2010 . Since the distance values are recorded serially one after the other by the laser tracker, the entire recording over the corresponding partial area of the inner wall of the container can take up to several hours, depending on the desired resolution. In addition, the container must have sufficiently large access to set up the laser tracker inside the container.

The invention is therefore based on the object of providing a measuring device and a method for the simple and rapid creation of an accurate tank table.

• - Eine 3D-Kamera, die ausgelegt ist, um
  • o zumindest von einem Teilbereich der Innenwand des Behälters eine Matrix an Distanzwerten aufzunehmen und zusammen mit korrespondierenden Positionsdaten in
• - einer Auswerte-Schaltung abzuspeichern, wobei die Auswerte-Schaltung ausgelegt ist, um
  • o aus den Distanzwerten sowie den korrespondierenden Positionsdaten ein dreidimensionales Modell von zumindest dem Teilbereich zu erstellen, und um
  • o auf Basis des dreidimensionalen Modells die Tanktabelle zu erstellen.

The invention solves this problem with a measuring device for creating a tank table for a product container, which comprises the following components:

• - A 3D camera that is designed to
  • o to record a matrix of distance values from at least a partial area of the inner wall of the container and, together with corresponding position data, in
• - To store an evaluation circuit, the evaluation circuit being designed to
  • o to create a three-dimensional model of at least the partial area from the distance values and the corresponding position data, and to
  • o create the tank table based on the three-dimensional model.

In the context of this application, the term “3D camera” basically includes any system by means of which a matrix of distance values can be recorded in a selected image area, the 3D camera storing the distance values together with position data of the respective distance value. The position can be defined, for example, as a pixel index of the distance value in the image area or as an angle coordinate in relation to the measuring device. Accordingly, so-called ToF cameras (“Time of Flight”), for example, can be used as 3D cameras, which include corresponding semiconductor-based sensors (also known as PMD sensors, “Photonic Mixing Device”). The same functionality can also be achieved, for example, by means of a LIDAR camera ("Light Detection And Ranging"). Accordingly, the 3D camera of the measuring device can be designed, for example, as a time-of-flight camera or as a LIDAR camera.

According to the invention, in contrast to laser-based distance measurement, a large number of distance values are recorded in parallel using the 3D camera, so that the creation of the three-dimensional model does not require a great deal of time. This means that a high-resolution tank table can be created within a short period of time. At the same time, by using a 3D camera, the measuring device can be designed to be overall compact and thus, for example, as an integral part of a level measuring device.

So that the three-dimensional model can be set in relation to the perpendicular and thus in relation to the product surface, the measuring device can be equipped with a corresponding inclination sensor, for example. Here, the inclination sensor is used to measure at least one angle in relation to the perpendicular at which the 3D camera records the partial area. As a result, the evaluation circuit can set the three-dimensional model in relation to the perpendicular with the aid of the at least one measured angle, if designed accordingly.

If the measuring device is arranged in such a way that the partial area of an individual receptacle does not cover the entire container bottom, the measuring device must be designed in such a way that several adjacent or overlapping partial areas are picked up, so that at least the entire container bottom and the container wall except for Height of the maximum filling level are shown. For this purpose, the measuring device can include, for example, an actuator unit, by means of which the 3D camera can be pivoted about at least one axis, in particular two axes running perpendicular to one another. As a result, several matrices from different sub-areas can be recorded at different angles. The evaluation unit is to be designed accordingly so that the three-dimensional model is created on the basis of the multiple matrices.

If the volume that the filling material occupies in the container is not to be calculated in the measuring device or level measuring device, but in a higher-level unit, the measuring device has to include a particularly wireless communication interface by means of which the three-dimensional model and / or the tank table can be sent to a higher-level unit can be transmitted.

• - Aufnahme einer Matrix an Distanzwerten von zumindest einem Teilbereich der Innenwand des Behälters,
• - Abspeichern der Distanzwerte zusammen mit korrespondierenden Positionsdaten,
• - Erstellung eines dreidimensionalen Modells des Teilbereichs aus den Distanzwerten und den korrespondierenden Positionsdaten, und
• - Erstellung der Tanktabelle auf Basis des dreidimensionalen Modells.

Corresponding to the measuring device according to the invention, the object is that of the invention is based on a method for creating a tank table of a product container by means of the measuring device according to one of the previously described embodiment variants. For this purpose, the method comprises at least the following method steps:

• - Recording of a matrix of distance values from at least a partial area of the inner wall of the container,
• - Saving the distance values together with the corresponding position data,
• - Creation of a three-dimensional model of the sub-area from the distance values and the corresponding position data, and
• - Creation of the tank table based on the three-dimensional model.

The method can be expanded to include one or more partial areas from different positions of the measuring device. This makes sense, for example, if obstacles such as agitators or inlets in a specific camera position obscure the optical path between the 3D camera and the partial area to be recorded. For this purpose, the measuring device can be designed, for example, in such a way that at least the 3D camera can be repositioned accordingly within the container.

• 1: eine schematische Darstellung eines erfindungsgemäßen Messgerätes an einem Behälter,
• 2: eine Draufsicht in das Behälter-Innere aus der Perspektive des erfindungsgemäßen Messgerätes, und
• 3: eine Detailansicht zu einer möglichen Ausgestaltungsvariante des erfindungsgemäßen Messgerätes.

The invention is explained in more detail using the following figures. It shows:

• 1 : a schematic representation of a measuring device according to the invention on a container,
• 2 : a plan view into the container interior from the perspective of the measuring device according to the invention, and
• 3 : a detailed view of a possible embodiment of the measuring device according to the invention.

For a general understanding of the measuring device according to the invention 11 is in 1 a container 2 with a filling good 3 shown. The filling material can be, for example, fuel, liquid gas or water. Where is the volume V , which the product 3 currently in the container 2 occupies to determine. A radar-based level measuring device is required for this 1 at a known installation height H above the product 3 on a flange connection 13 of the container 2 appropriate. Depending on the intended use, the container 2 be more than 100 m high.

The level measuring device 1 is like that on the container 2 aligned and attached that there is a radar signal according to the pulse time of flight method or according to the FMCW method S _R orthogonally in the direction of the product surface 3 sends out. As a result of the reflection of the radar signal S _R The level measuring device receives this at the product surface 1 the reflected radar signal S _R depending on the distance d = h - L to the product surface after a corresponding running time.

If the level meter 1 works according to the pulse radar method, it is the radar signal S _R periodically emitted radar pulses, so that based on the pulse transit time between emission of the pulse and the reflected, pulse-shaped radar signal S _R immediately the distance d and thus the level L. can be determined.

In the case of FMCW radar, the level measuring device sends 1 the radar signal S _R as a continuous signal, but with a time-defined frequency modulation. The running time and thus the distance or the filling level are accordingly L. when implementing the FMCW method on the basis of the current frequency difference between the currently received radar signal and the radar signal transmitted at the same time S _R certainly. With both radar methods it is possible according to the state of the art to determine the level L. under ideal conditions (well reflective filling material 3 , planar product surface, no obstacles such as agitators or other fixtures in the signal path of the radar signal S _R ) to be resolved with an accuracy in the sub-micrometer range.

To based on the measured level L. the volume V of the product in the container 1 can be determined in the level measuring device 1 a tank table V (L) of the container 2 deposited. The level measuring device includes 1 to create the tank table V (L) , as in 2 shown, a measuring device according to the invention 11 . From the meter 11 becomes the tank table V (L) recorded by a 3D camera 12 of the measuring device 11 when the container is empty 2 in at least one sub-area 4th the inner wall of the container 2 a matrix of distance values d _{α, γ} records. With the variant in 1 is the measuring device 11 is like this on the level measuring device 1 attached that the sub-area 4th analogous to the transmitted radar signal S _R taken from the position of the flange.

Together with the associated Position data [ α , γ ] are the corresponding distance values d _{α, γ} in an evaluation circuit of the measuring device 11 deposited. The position data [ α , γ ] are also used by the 3D camera 12 created, therefore these are in relation to the measuring device 11 Are defined. The position data will be correspondingly depending on the 3D camera used 12 for example as pixel indices of the distance value d _{α, γ} in the image area or as angle coordinates [ α , γ ] saved. Based on the position data [ α , γ ] and the distance values d _{α, γ} creates the evaluation circuit of the measuring device 11 a three-dimensional model of the inner wall of the container in at least a partial area 4th . The three-dimensional model can be based on a Cartesian or a polar coordinate system.

Because the three-dimensional model is the inner wall of the container 2 in at least one sub-area 4th the tank table can in turn based on the three-dimensional model V (L) to be created. The evaluation circuit of the measuring device 11 can implement this by calculating an associated area A (L _i ) for each discrete fill level L _i from those points of the 3D model that are each at the same fill level L _i .

Which of the points of the 3D model are located at a fill level L _i can be determined, for example, by relating the points to the perpendicular. This is possible, for example, if the measuring device 11 this is equipped with a corresponding inclination sensor.

By summing the areas A (L _i ), multiplied by the corresponding differences between the fill level levels L _i , the evaluation circuit of the measuring device 11 the volume V can be calculated, for example, or the tank table V (L _i ) can be created according to: $$V\left({\mathrm{L.}}_i\right)={\displaystyle \sum _{i=0}\mathrm{A.}\left({\mathrm{L.}}_i\right)}*\left({\mathrm{L.}}_{i+1}-{\mathrm{L.}}_i\right)$$

To create the tank table V (L) it is sufficient to only have a single matrix of distance values d _{α, γ} include when the sub-area 4th in which the distance values d _{α, γ} the entire bottom of the container 2 and the container wall fully up to the level of the maximum fill level L. covers. If this is not the case, several adjoining or overlapping partial areas 4 _{ap are to be} included, which as a whole cover the entire bottom of the container 2 and the container wall fully up to the level of the maximum fill level L. cover. This is shown in 2 from the perspective of the 3D camera 12 on the bottom of the container 2 . The 3D camera 12 of the measuring device 11 is in this case about two mutually perpendicular axes α , γ designed to pivot so that the 3D camera 12 the matrices of distance values in series in the individual sub-areas d _{α, γ} as it can in 4th is illustrated. The advantage of a swiveling design of the 3D camera 12 or the recording of several adjoining partial areas 4 _ap is that the three-dimensional model of the container inner wall and thus the tank table V (L) can potentially be created with a higher resolution.

Usually the level gauge is 1 via an interface such as "PROFIBUS", "HART" or "Wireless HART" with a higher-level unit 4th such as B. a process control system connected. The volume V of the medium in the container 2 or the level value L. be transmitted, for example, to any inflows or outflows of the container 2 to control. However, other information about the general operating state of the level measuring device can also be provided 1 be communicated.

This in 1 shown measuring device 11 to determine the tank table V (L) is part of the level measuring device 1 designed. It goes without saying, however, that the measuring device 11 in the context of the invention, as an alternative to this, not as an integral part of the level measuring device 1 , but can be designed as a stand-alone device. In this design, the measuring device 11 and the level gauge 1 or the higher-level unit 4th Equip with a suitable interface to the tank table V (L) from the measuring device 11 from transferring.

In addition, the measuring device 11 in the case of independent design, be designed in such a way that it fits to the flange connection 13 of the container 2 to which the level measuring device will later be used 1 is attached, is mountable. Thus the tank table V (L) taken from the same position from which the level meter 1 the level L. certainly.

List of reference symbols

1

Level measuring device

2

container

3

Filling material

4th

Part of the inner wall of the container

5

Parent unit

11

Measuring device for creating the tank table

12

3D camera

13

Flange connection

d

Distance to the product surface

d _{α, γ}

Distance values, determined by the 3D camera

H

Installation height

L.

Level

S _R

Radar signal

V

Volume of the product

V (L)

Tank table

α, γ

Position data in relation to the 3D camera

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102012104858 A1 [0004]
• DE 102013108490 A1 [0004]

Non-patent literature cited

• ISO 7507-4: 2010 [0010]

Claims (9)

Measuring device for creating a tank table (V (L)) of a product container (2), comprising: - A 3D camera (12) which is designed to o at least a partial area (3) of the inner wall of the container (2) to record a matrix of distance values (d _{α, γ} ) and to store it together with corresponding position data ([α; γ]) in an evaluation circuit, the evaluation circuit being designed to generate o from the distance values (d _{α, γ} ) as well as the corresponding position data ([α; γ]) to create a three-dimensional model of at least the sub-area (3), and to create the tank table (V (L)) based on the three-dimensional model. Measuring device after Claim 1 , wherein the 3D camera (12) is designed as a time-of-flight camera or as a LIDAR camera. Measuring device after Claim 1 or 2 , comprising: - An actuator unit by means of which the 3D camera (12) can be pivoted about at least one axis (a), in particular two axes (α, γ). Measuring device according to one of the preceding claims, comprising: - An inclination sensor which is designed to determine at least one angle (α, γ) at which the 3D camera (12) records the sub-area (3) in relation to the perpendicular, the evaluation circuit being designed to be three-dimensional To set the model based on the at least one angle (α, γ) in relation to the perpendicular. Measuring device according to one of the preceding claims, comprising: - A particularly wireless communication interface, by means of which the three-dimensional model and / or the tank table (V (L)) can be transmitted to a higher-level unit (4). Filling level measuring device, comprising a measuring device (11) according to one of the preceding claims. Method for creating a tank table (V (L)) of a product container (2) by means of a measuring device (11) according to one of the Claims 1 to 5 , comprising the following method steps: - recording a matrix of distance values (d _{α, γ} ) from at least a partial area (3) of the inner wall of the container (2), - storing the distance values (d _{α, γ} ) together with corresponding position data ([α, γ]), - Creation of a three-dimensional model of the sub-area (3) from the distance values (d _{α, γ} ) and the corresponding position data ([α, γ]), and - Creation of the tank table (V (L)) on the basis of the three-dimensional Model. Procedure according to Claim 3 and 7th , whereby a plurality of matrices from different partial areas (3) are recorded at different angles (α, γ), and the three-dimensional model is created on the basis of the plurality of matrices. Procedure according to Claim 7 or 8th , wherein the at least one sub-area (3) is recorded from different positions of the measuring device (11).

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