DE102023127899A1 - Method for determining an inner diameter of a fluid cylinder - Google Patents

Abstract

The invention relates to a pneumatic or hydraulic cylinder—in short, a "fluid cylinder"—which can be used, for example, as a working cylinder for driving devices. In particular, the invention relates to a computer-implemented method for determining an inner diameter of the fluid cylinder (100). The method comprises the following steps:
transmitting, by means of a radar sensor (200), radar waves (220) into a piston chamber (130) of the fluid cylinder (100);
detecting, by means of the radar sensor (200), reflected radar waves (220) as a detected echo curve (600);
comparing, by means of a classifier (520), the acquired echo curve (600) with a plurality of stored attributed echo curves (610, 620) stored in a database (530), wherein the attributes (612, 622) of the stored echo curves (610, 620) comprise an inner diameter (z) of a fluid cylinder (100);
selecting, by means of the classifier (520), that echo curve (610) from the plurality of stored attributed echo curves (610, 620) which has the highest degree of similarity to the detected echo curve (600); and
outputting the inner diameter (z) of the selected attributed echo curve (610), wherein the inner diameter (z) is one of the attributes (612) of the selected attributed echo curve (610).

Description

Field of the invention

The invention relates to a pneumatic or hydraulic cylinder—abbreviated to "fluid cylinder"—which can be used, for example, as a working cylinder for driving devices. In particular, the invention relates to a computer-implemented method for determining an inner diameter of a fluid cylinder, a cylinder measuring system, a use of a fluid cylinder, a program element, and a computer-readable medium.

background

When using pneumatic cylinders and/or hydraulic cylinders, it may be useful and/or necessary to precisely know the position of the piston and/or other parts inside the cylinder. In this case, arranging a distance sensor, particularly a radar sensor, in a piston chamber of the fluid cylinder can provide particularly high measurement accuracy. Knowing the inner diameter of the fluid cylinder and/or parameterizing the sensor with the inner diameter can contribute to increasing measurement accuracy.

Summary

The object of the invention is to provide a method that enables the determination of the inner diameter of a fluid cylinder. This object is achieved by the subject matter of the independent patent claims. Further developments of the invention will become apparent from the subclaims and the following description.

• Senden, mittels eines Radarsensors, von Radarwellen in eine Kolbenkammer des Fluidzylinders; erfassen, mittels des Radarsensors, von reflektierten Radarwellen als eine erfasste Echokurve; vergleichen, mittels eines Klassifikators, der erfassten Echokurve mit einer Vielzahl von gespeicherten attributierten Echokurven, die in einer Datenbank gespeichert sind, wobei die Attribute der gespeicherten Echokurven einen Innendurchmesser eines Fluidzylinders umfassen; auswählen, mittels des Klassifikators, derjenigen Echokurve aus der Vielzahl von gespeicherten attributierten Echokurven, welche einen höchsten Ähnlichkeitsgrad mit der erfassten Echokurve aufweist; und ausgeben des Innendurchmessers der ausgewählten attributierten Echokurve, wobei der Innendurchmesser eines der Attribute der ausgewählten attributierten Echokurve ist.

One aspect relates to a computer-implemented method for determining an inner diameter of a fluid cylinder, comprising the steps:

• Sending, by means of a radar sensor, radar waves into a piston chamber of the fluid cylinder; detecting, by means of the radar sensor, reflected radar waves as a detected echo curve; comparing, by means of a classifier, the detected echo curve with a plurality of stored attributed echo curves stored in a database, wherein the attributes of the stored echo curves include an inner diameter of a fluid cylinder; selecting, by means of the classifier, that echo curve from the plurality of stored attributed echo curves which has a highest degree of similarity to the detected echo curve; and outputting the inner diameter of the selected attributed echo curve, wherein the inner diameter is one of the attributes of the selected attributed echo curve.

The term "fluid cylinder" (or "cylinder") is used below to refer to both a pneumatic cylinder and a hydraulic cylinder. The cylinder can, for example, have a round, elliptical, rectangular, square, and/or other cross-section. The computer-implemented method can, for example, be carried out on a computing and control unit of a fluid cylinder measuring system and/or on another computing unit, e.g., on a server and/or a cloud. For this purpose, the computing unit can be connected to a radar sensor via a communication channel—e.g., via a cable or wirelessly—directly or via another device. The radar sensor is arranged in an interior space, usually at one end of a piston chamber, of the fluid cylinder. The radar sensor can, for example, be arranged in or on a base cover, e.g., in or on an opening in the base cover, of the fluid cylinder. The cylinder can, for example, have a round, elliptical, rectangular, square, and/or other cross-section. The radar sensor can be configured to transmit radar waves into a piston chamber of the fluid cylinder, e.g., from the opening in the base cover. The radar sensor can, for example, have a frequency greater than 100 GHz, greater than 200 GHz, or approximately 240 GHz. The radar waves are then reflected by elements of the piston chamber, e.g., by a piston surface of the fluid cylinder, by a microwave reflector mounted on the piston, by a surface of the piston rod, by a wall of the fluid cylinder, and/or by other elements arranged in or on the piston chamber. The reflected radar waves can, for example, be further processed in the form of a recorded echo curve. In an echo curve, the amplitudes of the reflected radar waves are essentially plotted against a distance from a radar antenna of the radar sensor. The radar sensor can use the so-called CW (Continuous Wave), FMCW (Frequency Modulated Continuous Wave), SFCW (Stepped Frequency Continuous Wave), and/or pulse radar measurement principles. The echo curve can have a large number of sampling points, e.g., several tens, several hundred, or several thousand sampling points. The number of sampling points may depend on the measurement accuracy and/or the dimensions of the cylinder.

The acquired echo curve is then compared with a number of stored attributed echo curves. The acquired echo curve and/or the stored attributed echo curves can, for example, contain a specific signal shape, specific Propagation modes, specific noise, and specific ringing behavior near the antenna. The stored attributed echo curves can be stored in a database, for example. The database can be located on a server, in a cloud, and/or in the computing and control unit of the fluid cylinder measuring system. The stored attributed echo curves can be acquired using a large number of measurements, for example, on a large number of cylinder types; the different cylinder types can differ, in particular, in their different inner diameters. Each stored echo curve can have a large number of attributes, e.g., time of measurement, position of the piston, cylinder type, measurement principle, a correction curve, etc. Each stored echo curve has an inner diameter of the fluid cylinder as an attribute. The comparison of the acquired echo curve with the large number of stored attributed echo curves is carried out using a classifier. The classifier can compare all or a selected subset of the echo curve support points. The classifier can determine a degree of similarity between the stored echo curves and the acquired echo curve.

Based on the "degree of similarity" metric, the classifier can select the echo curve from the plurality of stored attributed echo curves that has the highest degree of similarity to the acquired echo curve. The "inner diameter" attribute can be output from the stored attributed echo curve and/or a class of the stored attributed echo curves with the highest degree of similarity. In embodiments in which the class of stored attributed echo curves is considered, for example, a class membership can be determined and, according to the metric, the class that has the highest degree of similarity can be output. In this case, in at least some cases, determining the similarity to a specific echo curve can be omitted.

The inner diameter of the fluid cylinder determined and output in this way can be used for a variety of measurement applications. These measurement applications can include, for example, determining the volume of the fluid cylinder. The inner diameter can be used, alternatively or additionally, to improve the measurement accuracy of the radar sensor, for example, to provide a compensation curve or correction curve for the echo curves recorded for this cylinder type.

This method advantageously enables automated determination of the inner diameter of a fluid cylinder. This eliminates the need for error-prone and time-consuming manual input of the inner diameter. Furthermore, the method can contribute to automated parameterization of the radar sensor and/or the fluid cylinder measurement system, allowing measurements to be started very quickly and reliably upon new installation and/or replacement of the radar sensor and/or the fluid cylinder measurement system.

In some embodiments, the classifier determines the degree of similarity using an error measure. The error measure can be determined, for example, using a sum of deviations between the acquired echo curve and the stored echo curves. The sum of deviations can correspond to a simple sum, a weighted sum, a sum of squares, and/or another sum. An algorithmic classifier can advantageously be implemented by a variety of computing and control units, even by some microcontrollers. This can contribute to the method being implemented by a fluid cylinder measurement system without external connection.

In some embodiments, the classifier is a trained neural network (ANN, Artificial Neural Network) configured to assign the acquired echo curve to one of the attributed echo curve classes. The ANN can be trained, for example, using the plurality of stored attributed echo curves stored in the database. In at least some embodiments, this can result in the ANN classifier no longer comparing the acquired echo curve with individual echo curves, but merely classifying or assigning it to an echo curve class. This can contribute to a particularly fast and/or flexible determination of the highest degree of similarity. In particular, in productive operation, the neural network can reduce the number of required stored attributed echo curves—and thus the size of the database—for example, because at least some neural networks can be based on “similarity classes” rather than strict algorithmic similarities. It can be particularly advantageous that an ANN no longer requires a database with stored echo curves for operation, but rather such a database can be used solely for training the model. This makes it possible to place the classifier in or on the sensor. A classifier trained in this way would then, for example, no longer measure similarity to a specific echo curve. but rather a probability of belonging to a class with a specific inner diameter.

In some embodiments, the inner diameter of the fluid cylinder is used to parameterize the radar sensor. The parameterization may include, for example, the dimensions of the cylinder, so that, for example, a cylinder position can be determined without complex calibration and a corresponding compensation curve can be selected based on the cylinder diameter.

In some embodiments, the inner diameter of the fluid cylinder is used to improve the measurement accuracy of the radar sensor. For example, the attributes of the selected attributed echo curve can contain correction values, for example, in the form of a compensation curve for the detected echo curve—e.g., stored in the sensor. In particular, the determined inner diameter can contribute to improving the accuracy of determining the position of the piston or cylinder head. For example, the effect that the propagation speed or propagation capability of certain microwave modes in the fluid cylinder, e.g., pneumatic cylinders, can change depending on its diameter can be taken into account. Furthermore, a change in the piston position or distance from the radar sensor can lead to a change in the areas, area proportions, and/or angles illuminated by the microwave—and thus to a change in the relative amplitudes of individual echoes. Furthermore, certain piston positions can lead to an increase in the amplitude of certain radar echoes, for example, due to reflections from the piston wall. This interference of the corresponding echoes, which change in amplitude or position due to the changing piston position, with the actual piston echo can lead to a reduction in the accuracy of the piston position determination. By knowing the dimensions of the fluid cylinder, especially the inner diameter, these effects can be specifically compensated.

In some embodiments, the fluid cylinder is a fluid cylinder according to ISO 15552. This can advantageously simplify the determination of the inner diameter because fluid cylinders according to this standard have standardized inner diameters. This can significantly reduce the number of required comparisons and/or stored attributed echo curves.

In some embodiments, the radar sensor has a frequency greater than 100 GHz, greater than 200 GHz, e.g., approximately 240 GHz. Such high radar frequencies can be advantageous both for the dimensions and the achievable accuracy of the radar sensor.

In some embodiments, a piston of the fluid cylinder is positioned at a predefined position before the radar waves are transmitted. The predefined position can be specified in centimeters, for example. The predefined position can be an end position of the piston, for example. This can also be detected during dynamic operation, for example. It can be advantageous here if the radar sensor has a very high measurement repetition rate of, for example, over 100 Hz, over 200 Hz, over 500 Hz.

One aspect relates to a fluid cylinder measuring system for detecting a distance between a radar sensor and a piston surface of a fluid cylinder. The fluid cylinder measuring system comprises a fluid cylinder, the radar sensor arranged in the fluid cylinder, and a computing and control unit connected to the radar sensor and configured to perform a method as described above and/or below.

One aspect relates to a fluid cylinder having at least one radar sensor of a fluid cylinder measuring system as described above and/or below.

One aspect relates to a use of a fluid cylinder measuring system as described above and/or below for detecting and/or determining a distance between the radar sensor and a piston surface of a piston of a fluid cylinder and/or for detecting and/or determining a speed of the piston.

In some embodiments, prior to determining the distance and/or velocity of the piston, the fluid cylinder measurement system is parameterized based on a method as described above and/or below.

One aspect relates to a program element which, when executed on a computing and control unit of a fluid cylinder measuring system as described above and/or below and/or on another computing unit, instructs the computing and control unit and/or the other computing unit to carry out the method as described above and/or below.

One aspect relates to a computer-readable medium on which the program element described here is stored.

For further clarification, the invention is described with reference to embodiments illustrated in the figures. These embodiments are to be understood as examples only and not as limitations.

Short description of the characters

• 1 schematisch einen Fluidzylinder gemäß einer Ausführungsform;
• 2 schematisch ein Fluidzylindermesssystem gemäß einer Ausführungsform;
• 3a schematisch einen Fluidzylinder gemäß einer Ausführungsform;
• 3b ein Beispiel einer erfassten Echokurve gemäß einer Ausführungsform;
• 4a und 4b Beispiele von gespeicherten Echokurven gemäß einer Ausführungsform;
• 5 ein Flussdiagramm mit einem Verfahren gemäß einer Ausführungsform.

It shows:

• 1 schematically shows a fluid cylinder according to an embodiment;
• 2 schematically shows a fluid cylinder measuring system according to an embodiment;
• 3a schematically shows a fluid cylinder according to an embodiment;
• 3b an example of a detected echo curve according to an embodiment;
• 4a and 4b Examples of stored echo curves according to one embodiment;
• 5 a flowchart with a method according to an embodiment.

Detailed description of embodiments

1 schematically shows a fluid cylinder 100 according to an embodiment. The fluid cylinder 100 can be implemented, for example, as a pneumatic cylinder or hydraulic cylinder. The fluid cylinder 100 has a first piston chamber 130 (in 1 (shown to the right of the piston 110) and a second piston chamber 140. The piston chambers 130 and 140 each have a connection 135 and 145, respectively, for the introduction and/or discharge of a fluid. The fluid cylinder 100 has a piston 110, which is guided by a piston rod 120 along a cylinder wall 105. The fluid cylinder 100 has a diameter z between the cylinder walls 105. The piston 110 has, on the side of the first piston chamber 130, a piston surface 115. The piston rod 120 has, also on the side of the first piston chamber 130, a piston rod surface 117. Alternatively or additionally, the piston rod surface can be designed as a reflector 117, which is arranged on a mechanically designed device for damping at the end position - also referred to as "end position damping". The fluid cylinder 100 further comprises a base cover 180. The base cover 180 for the fluid cylinder 100 is a non-movable end of the cylinder chamber or piston chamber 130. The base cover 180 can be an integrated part of the cylinder 100, or a detachable or non-detachable component of the cylinder 100. The connection 135 can also be integrated into the base cover. The base cover 180 has an opening 182, which can be designed to match the geometric configuration of the end position damping and the reflector 117 arranged thereon, wherein the reflector 117 has an outer diameter which is smaller than the opening 182. The opening 182 is in 1 shown centrally; however, the opening 182 can also be arranged offset from the center. The base cover 180 is designed such that it is configured for the installation of the radar sensor 200. The radar sensor 200 is configured to detect a distance d between the radar sensor 200 and the piston surface 115 and/or piston rod or reflector surface 117 of the fluid cylinder 100. For this purpose, the radar sensor 200 sends radar waves 220 from an antenna 210 into the piston chamber 130 of the fluid cylinder 100. The radar waves 220 are then reflected by elements of the piston chamber 130, e.g., from the piston surface 115 of the fluid cylinder 100, from a surface 117 of the piston rod 120, from the wall 105 of the fluid cylinder 100 and/or from other elements arranged in or on the piston chamber. The reflected radar waves can be received by the antenna 210 and then forwarded, e.g. to a computing and control unit 500 (see 2 ).

2 schematically shows a fluid cylinder measuring system 102 according to an embodiment. The fluid cylinder 100 can, for example, be like the fluid cylinder 100 of 1 The measured values from the radar sensor 200, in particular a recorded echo curve 600 (see e.g. 3b) , can be transmitted via a wired or wireless connection 510, for example a cable 510, to a computing and control unit 500. The control unit 500 can comprise a display unit 550, which can have, for example, an optical, an acoustic or another type of output (e.g. printer, vibration, radio interface or communication module, etc.). The control unit 500 is configured to calculate the distance d between the radar sensor 200 and the piston surface 115 of the fluid cylinder 100 and/or to calculate values derived from the distance d. The computing and control unit 500 further comprises a classifier 520, which is configured to compare the acquired echo curve 600 with a plurality of stored attributed echo curves 610, 620 (see 4a and 4b) is set up. The stored attributed echo curves 610, 620 can be stored, for example, in a database, e.g., in the database 530 of the control unit 500. Alternatively or additionally, the database can be stored on a server, a cloud, and/or other devices. The classifier 520 can compare the acquired echo curve 600 with the plurality of stored attributed echo curves 610, 620 and, e.g., determine a degree of similarity for each of the stored echo curves 610, 620. The determination can be serial, parallel, or partially be carried out in parallel. The determination may depend on the type of classifier 520. The computing and control unit 500, or at least the classifier 520, may be implemented as a standalone module and/or integrated into the radar sensor 200, for example, in the same housing. If the classifier 520 is embodied as a neural network (ANN), then in at least some embodiments, the database 530 may be omitted in productive operation. By means of the classifier 520, the echo curve from the plurality of stored attributed echo curves 610, 620 can be selected which has the highest degree of similarity to the detected echo curve 600. The stored attributed echo curves 610, 620 have attributes, at least an inner diameter z of the fluid cylinder at which the stored echo curve was measured. The inner diameter z of the associated fluid cylinder can then be output from the stored attributed echo curve 610, which has the highest degree of similarity to the acquired echo curve 600, and thus the inner diameter can be determined. Alternatively, the classifier 520 can be an artificial neural network (ANN) that has been trained using a plurality of attributed echo curves 610, 620. The classifier 520 can be designed such that it can assign a acquired echo curve 600 to a class of attributed echo curves 610, 620. Since the information about the class membership is stored in the weights of the ANN, advantageously no storage space is required on the sensor for the plurality of attributed echo curves.

3a schematically shows a fluid cylinder 100 according to an embodiment. The same or similar components as in 1 are designated by the same reference symbol.

3b shows an example of a detected echo curve 600 according to an embodiment, which is generated by the fluid cylinder 100 of 3a The radar sensor 200 is configured to detect the distance d between the radar sensor 200 (or the antenna 210) and the piston surface 115 of the fluid cylinder 100. The distance d from 3a corresponds to the distance d of the echo curve 600. The distance d=0 on a right side of the echo curve 600 from 3b therefore corresponds to the antenna 210 of 3a The recorded echo curve 600 exhibits several maxima. Maxima 615 and 617 are particularly evident; maximum 615 corresponds to reflections from the piston surface 115, and maximum 617 corresponds to reflections from the piston rod surface 117 or from the geometric configuration of the reflector 117 of the end-position damping. Depending on the distance d of the piston from the radar sensor, the relative amplitude of these reflections can change and, due to interference and superposition of corresponding echoes, influence the accuracy of the distance determination depending on the piston diameter.

4a and 4b show examples of stored echo curves 610 and 620, respectively, according to one embodiment. The echo curves 610, 620 and further echo curves may be stored in a database, e.g., in the database 530 of the control unit 500 (see 2 ) and/or on a server. The echo curves 610 and 620 have attributes 612 and 622, respectively. The attributes 612 and 622 comprise at least one inner diameter z of the fluid cylinder at which the stored echo curve was measured. For attribute 612, an inner diameter z of one inch (1") is specified, and for attribute 622, an inner diameter z of two inches (2") is specified. Further attributes can include, for example, compensation or correction curves for the respective echo curve(s) and/or for the respective inner diameter or the distance of the piston from the radar sensor at which the respective echo curve was recorded. The classifier 520 compares the acquired echo curve 600 with the plurality of stored attributed echo curves 610, 620. It can be clearly seen that the echo curve 610 of 4a the recorded echo curve 600 of 3b is more similar than the echo curve 620 of 4b . The classifier 520 will therefore select echo curve 610 and output the attribute "z=1". Alternatively, a classifier pre-trained on a plurality of attributed echo curves can determine the affiliation of the echo curve 600 to one of the classes with a specific inner diameter. In this case, a comparison is no longer made with a specific echo curve 610 or 620, but with an echo curve class 610 or 620 (which is difficult to represent). However, the plurality of echo curve classes 610, 620 can be attributed in a similar way to the echo curves, so that the attributes of the echo curve classes 610, 620 can be used in a similar way to the attributes of the echo curves 610, 620, in particular for determining and/or outputting the inner diameter z.

5 shows a flowchart 700 with a method for determining an inner diameter z of a fluid cylinder 100 according to one embodiment. In a step 702, radar waves 220 are transmitted into a piston chamber 130 of the fluid cylinder 100 by means of a radar sensor 200. In a step 704, reflected radar waves 220 are detected as a detected echo curve 600 by means of the radar sensor 200. In a step 706, the The acquired echo curve 600 is compared with a plurality of stored attributed echo curves 610, 620. If an artificial neural network (ANN) is used as the classifier 520, the classification can be performed using a model pre-trained using a plurality of attributed echo curves. The stored attributed echo curves 610, 620 are stored in a database 530, which is not necessarily stored on the control unit. When using a trained ANN, the database 530 can be dispensed with in at least some embodiments during productive operation because it is only used for training the ANN. The comparison can then be implemented as an assignment to an attributed echo curve class 610, 620. Attributes 612, 622 of the stored echo curves 610, 620 include an inner diameter z of a fluid cylinder 100. In a step 708, a classifier 520 is used to select the echo curve 610 from the plurality of stored attributed echo curves 610, 620 that has the highest degree of similarity to the acquired echo curve 600. In a step 710, the inner diameter z of the selected attributed echo curve 610 is output, wherein the inner diameter z is one of the attributes 612 of the selected attributed echo curve 610. In an optional step 712, the inner diameter z of the fluid cylinder 100 is used to parameterize the radar sensor 200 and/or to improve a measurement accuracy of the radar sensor 200, for example by selecting and using a correction curve specific to the determined inner diameter z.

List of reference symbols

100

Fluid cylinder

102

Fluid cylinder measuring system

105

cylinder wall

110

Pistons

115

Piston surface

117

Piston rod surface

120

piston rod

130

first piston chamber

135

Connection

140

second piston chamber

145

Connection

180

floor cover

182

Opening in the bottom cover

200

radar sensor

210

antenna

220

radar waves

500

Computing and control unit

520

Classifier

530

database

550

Display unit

600

recorded echo curve

610, 620

stored attributed echo curves or echo curve classes

612, 622

Attributes of the echo curves or echo curve classes

700

flow chart

702 - 712

Steps

d

distance

z

Inner diameter of the cylinder

Claims (14)

A computer-implemented method for determining an inner diameter (z) of a fluid cylinder (100), comprising the steps of: transmitting, by means of a radar sensor (200), radar waves (220) into a piston chamber (130) of the fluid cylinder (100); detecting, by means of the radar sensor (200), reflected radar waves (220) as a detected echo curve (600); comparing, by means of a classifier (520), the detected echo curve (600) with a plurality of stored attributed echo curves (610, 620) stored in a database (530) and/or with a plurality of attributed echo curve classes (610, 620), wherein the attributes (612, 622) of the stored echo curves or echo curve classes (610, 620) comprise an inner diameter (z) of a fluid cylinder (100); selecting, by means of the classifier (520), that echo curve or echo curve class (610) from the plurality of stored attributed echo curves or echo curve classes (610, 620) which has the highest degree of similarity to the acquired echo curve (600); and outputting the inner diameter (z) of the selected attributed echo curve or echo curve class (610), wherein the inner diameter (z) is one of the attributes (612) of the selected attributed echo curve or echo curve class (610). Computer-implemented method according to Claim 1 , wherein the classifier (520) determines the degree of similarity using an error measure. Computer-implemented method according to Claim 1 or 2 , wherein the classifier (520) is a trained neural network which is used to assign the detected echo curve (600) to a the attributed echo curve classes (610, 620) is set up. Method according to one of the preceding claims, wherein the inner diameter (z) of the fluid cylinder (100) is used to parameterize the radar sensor (200). Method according to one of the preceding claims, wherein the inner diameter (z) of the fluid cylinder (100) is used to improve a measurement accuracy of the radar sensor (200). Method according to one of the preceding claims, wherein the fluid cylinder (100) is a fluid cylinder according to ISO 15552. Method according to one of the preceding claims, wherein the radar sensor (200) has a frequency of greater than 100 GHz, greater than 200 GHz, e.g. of approximately 240 GHz. Method according to one of the preceding claims, wherein a piston (110) of the fluid cylinder (100) is arranged at a predefined position before the radar waves (220) are transmitted. A fluid cylinder measuring system (102) for detecting a distance (d) between a radar sensor (200) and a piston surface (115) of a fluid cylinder (100), the fluid cylinder measuring system (102) comprising: a fluid cylinder (100); the radar sensor (200) arranged in the fluid cylinder (100); and a computing and control unit (500) connected to the radar sensor (200) and configured to perform a method according to one of the preceding claims. Fluid cylinder (100), comprising at least one radar sensor (200) of a fluid cylinder measuring system (102) according to Claim 9 . Use of a fluid cylinder measuring system (102) according to Claim 9 for detecting and/or determining a distance (d) between the radar sensor (200) and a piston surface (115) of a piston (110) of a fluid cylinder (100) and/or for detecting and/or determining a speed of the piston (110). Use according to Claim 11 , wherein before determining the distance (d) and/or the speed of the piston (110), the fluid cylinder measuring system (102) is based on a method according to one of the Claims 1 - 8 is parameterized. Program element which, when it is executed on a computing and control unit (500) of a fluid cylinder measuring system (102) according to Claim 9 and/or is executed on another computing unit, instructs the computing and control unit (500) and/or the other computing unit to carry out the method according to one of the Claims 1 - 8 to carry out. A computer-readable medium on which a program element according to the preceding claim is stored.

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