Monitoring retraction system

Abstract

The invention relates to the monitoring of a retraction system (100). In particular, the invention relates to a device (10) for monitoring a retraction system (100) having at least one spring (12), a retraction system (100) having a device (10) of this type, a robot having a device (10) of this type or a retraction system (100) of this type, and a method for monitoring a retraction system (100) of this type. One embodiment of the device (10) has at least one capacitor (14) which is interconnected with the at least one spring (12) in such a way that the interconnection of the at least one spring (12) and the at least one capacitor (14) forms an oscillation circuit (16), a frequency determination component (20) which is designed to determine information about the frequency of the oscillation circuit (16), and an evaluation unit (30) which is designed to derive information about the length of the at least one spring (12) from the information about the frequency of the oscillation circuit (16).

Description

TECHNICAL FIELD

[0001] The present invention generally relates to monitoring of retraction systems. In particular, the present invention relates to a device for monitoring a retraction system having at least one spring, to such a retraction system having such a device, to a robot having such a device or such a retraction system, and to a method for monitoring such a retraction system. BACKGROUND

[0002] With the increasing diversity of automated production technology, the demand for energy supply systems also increases. More and more often, it is necessary to guide robots, such as, for example, industrial robots and manufacturing robots, not only electrical and pneumatic lines, but also, for example, supply hoses for bolts, rivets and screws. That is to say, in addition to guiding energy, data and media lines, industrial robots nowadays also frequently guide, for example, supply hoses for rivets or screws. The various lines are usually combined together in line assemblies and are often also referred to as hose assemblies. The movement of the robot, in particular of an industrial robot, is complex depending on the application. For example, industrial robots in the automotive industry work with high rotations and fast movements to install vehicle parts. In order to guide the lines for data, pneumatics and energy supply to the robot as safely as possible, manufacturers and / or users use line guides, for example energy chains.

[0003] In the multi-axis industrial robots conventionally used today, a plurality of individual lines for supplying tools arranged on the robot hand, for example welding tools, are supplied to the robot arm, which is also referred to as robot hand, at the front by means of a supply device, for example a hose assembly. The individual lines are, for example, power supply cables, electrical control cables, data cables and media guides for gases or liquids. These individual lines are usually combined, for example, in a common supply device such as a hose assembly and surrounded by a tubular protective sheath. Such hose assemblies are subjected to high stresses, on the one hand because of the movement of the robot arms relative to one another and, in particular, because of the often adverse environmental conditions (high temperatures, aggressive media, such as welding spatter, etc.).

[0004] The more the robot arms of a robot move and rotate, the greater the required component length in the lines. With minimal movement, no additional component length is required and can hang down from the robot. A retraction system ensures that the lines, such as, for example, a hose assembly, are guided close to the robot during each movement. In other words, the retraction system serves to keep the lines as compact as possible on the robot arm.

[0005] In other words, in the field of application of industrial robots, such line guiding devices and / or retraction systems are used to tension at least one supply device guided along a robot arm of an industrial robot and to adjust the length of the supply device after a movement of the robot arm. Such a line guiding device is known from EP 1 848 571 B1. Therein, a line guiding device for guiding a supply line, in particular for guiding a hose assembly of an industrial robot, is described. Another line guiding device in an industrial robot can be found, for example, in DE 201 137 42 U1.

[0006] DE 10 2018 204 184 A1 describes a method for monitoring a supply system of a robot. The robot has a robot arm and a robot hand movable relative to the robot arm, wherein the supply system has a supply chain, in particular a hose assembly, and a guide for the supply chain, and the supply chain is guided along the robot arm to supply the robot hand. The supply system also has a plurality of sensors for monitoring at least one state variable of the supply system, wherein the functional capability of the supply system is derived from the values of the state variables determined by the sensors. The described system can also be referred to as a retraction system of a robot. The retraction system has a sensor system that detects the movement (tension, acceleration, speed, quantity, etc.) of the adjustment mechanism. It is problematic to install additional sensors of such a sensor system, such as cable tension sensors, on the retraction system in view of the available installation space and in particular can pose a risk of sensor defects. SUMMARY

[0007] Therefore, there is a need for a device for monitoring a retraction system that ensures integration into the existing installation space of the retraction system in as simple a manner as possible. In particular, it is desirable that the device, for example a sensor system, is robust and failsafe and allows to perform sufficiently precise error-free measurements with as few additional costs as possible. The device, for example a sensor system, ideally can be used for different retraction systems.

[0008] According to a first aspect of the present application, a device for monitoring a retraction system is presented. The retraction system has at least one spring. The device has at least one capacitor connected or interconnected with the at least one spring. The at least one capacitor is connected or interconnected with the at least one spring such that the connection or interconnection of the at least one spring and the at least one capacitor forms an oscillation circuit. The device has a frequency determination component. The frequency determination component is configured to determine information related / concerning a frequency of the oscillation circuit. The device has an evaluation unit. The evaluation unit is configured to derive information related / concerning a length of the at least one spring from the information related / concerning the frequency of the oscillation circuit. The information related / concerning the length of the at least one spring can be indicative of the length of the at least one spring. The length of the at least one spring can be derived from the information related / concerning the length of the at least one spring.

[0009] The retraction system can be a retraction system of a robot, in particular of an industrial robot. The retraction system can be part of a line guiding device or a supply device of a robot, in particular of an industrial robot. Separate lines for supplying a robot can be combined in a common supply device such as a hose assembly. For example, the separate lines can be, for example, power supply cables, electrical control cables, data cables and medium guides or supply hoses for gases, liquids, bolts, rivets and screws.

[0010] An oscillation circuit, also called electric oscillation circuit or resonance circuit, is a circuit which is able to resonate, which has a coil and a capacitor and which is able to perform an electric oscillation. In the oscillation circuit, energy is periodically exchanged between the magnetic field of the coil and the electric field of the capacitor, whereby a high current intensity or a high voltage alternately exists. In the device according to the first aspect, the at least one spring is used as a coil.

[0011] In other words, if a coil (inductance) and a capacitor (capacitance) are interconnected, an oscillation circuit is formed. The interconnection can take place in series or in parallel. If, for example, a voltage is applied to such a circuit for a short time, the capacitor charges to the maximum value of the voltage of the voltage source. If the voltage is switched off again, the capacitor discharges again via the coil. With the aid of the coil, the capacitor charges again with the opposite polarity. This process is repeated several times, wherein the voltage level is reduced over time due to the effective resistance in the oscillation circuit. In this way, a damped oscillation is obtained. In contrast, in the ideal case of an undamped oscillation, the voltage value does not decrease.

[0012] The at least one spring and the at least one capacitor can in each case be connected to each other in parallel, that is to say at least one parallel oscillation circuit can be formed. The at least one spring and the at least one capacitor can in each case be connected to each other in series, that is to say at least one series oscillation circuit can be formed.

[0013] The evaluation unit can be configured to derive information about a length change of the at least one spring from the information about the frequency of the oscillation circuit as the information about the length of the at least one spring. The length of the at least one spring can be derived or determined from the information about the length change. For example, the length of the at least one spring can be derived or determined from the information about the length change, taking into account a starting length before the length change. From the information about the length or the length change of the at least one spring, a stroke or a distance of movement of an associated system, for example a retraction system, can be determined.

[0014] A spring changes its length when loaded. As a result, the coupling factor of the individual windings changes. This in turn changes its inductance. In the case of a compression spring, the individual windings are (more) closely adjacent and better coupled to one another, so the inductance increases. On the other hand, in the case of a tension spring, the windings are far (further) apart and less well coupled, so the inductance decreases. By measuring the inductance, the length of the spring can be determined, and thus indirectly the stroke of an associated system with the spring. The inductance and the frequency of the oscillation circuit are interdependent. As a result, when the inductance of the at least one spring changes, the frequency of the oscillation circuit changes.

[0015] Such an oscillation circuit has a capacitor and a coil. For example, the oscillation circuit can consist of a capacitor and a coil / spring. The capacitor is initially in a charged state (for example charged by a current / voltage source). If the current source is switched off (for example, the system consists only of the capacitor and the coil), the oscillation circuit is / is established. The electric field of the capacitor causes a current, which discharges the capacitor. The current flowing through the coil thus induces a magnetic field. The growing magnetic field in turn induces a current, which opposes the discharging current of the capacitor. As soon as the capacitor is sufficiently discharged, this current becomes greater than the discharging current, and the current is reversed. As a result, the capacitor is charged again, and the magnetic field is weakened until the starting configuration is reached again. The entire cycle has / is completed. Therefore, the cycle starts again - the oscillation is ongoing.

[0016] The frequency determination component can be configured as a digital frequency determination component or can have a digital frequency determination component. The digital frequency determination component is configured to determine the number of pulses occurring in the oscillation circuit during a predetermined time period as the information about the frequency of the oscillation circuit. The predetermined time period can correspond to at least a portion of a period of the oscillation circuit, for example half a period of the oscillation circuit. The predetermined time period can correspond to an entire period of the oscillation circuit.

[0017] The frequency determination component can be configured to determine the information about the voltage of the oscillation circuit taking into account the information about the frequency of the reference oscillation circuit.

[0018] The apparatus can have a digital-to-analog converter (D / A converter). The digital-to-analog converter can be configured to convert the information about the frequency of the oscillation circuit into a voltage value.

[0019] The digital-to-analog converter can be configured to emit a voltage value to the evaluation unit. The evaluation unit can be configured to derive information about the length of the at least one spring from the emitted voltage value.

[0020] According to a first exemplary embodiment, the evaluation unit can receive information about the frequency of the oscillation circuit, e.g. from the frequency determination component, and can determine information about the length of the at least one spring, e.g. directly from the information about the frequency of the oscillation circuit.

[0021] According to a second exemplary embodiment, the evaluation unit can receive a voltage value, e.g. from the digital-to-analog converter, and can determine information about the length of the at least one spring, e.g. directly from the voltage value, and thus indirectly from the information about the frequency of the oscillation circuit.

[0022] The device can further have a magnet and a sensor component for detecting the magnet.

[0023] The evaluation unit can be configured to compare, when the sensor component detects the magnet, information about the length of the at least one spring determined at the time of the detection with previously known information about the length of the at least one spring and to determine, by means of the comparison, information about a deviation (between the determined information and the previously known information).

[0024] In this way, an occurring interference field can be taken into account. When the sensor passes the magnet or the sensor approaches the magnet, the previously known position can be compared with the determined position. By means of the determined difference, a deviation occurring in the signal can be eliminated or taken into account accordingly. Thus, the positions of the sensor component and the magnet relative to each other can be chosen such that, in each cycle, the magnet is detected by the sensor component, e.g. the magnet passes the sensor component, or vice versa. As a result, in each cycle, any deviation due to an interference field is taken into account or eliminated.

[0025] The sensor component can have a Hall sensor or can be configured as a Hall sensor.

[0026] According to a second aspect, a retraction system is proposed. The retraction system has at least one spring. The retraction system has at least one slider connected to the at least one spring. The retraction system has at least one guide. The guide is configured to guide the at least one slider. The slider can move on the guide. In other words, the slider can perform a translational movement on the guide. The retraction system has a device as already described herein.

[0027] The spring is tensioned or relaxed, e.g. due to a movement of the slider on the guide. The slider can be moved out of its starting position under the action of an external force. When the external force is removed, the slider can move on the guide back to the starting position. The spring can be configured as a tension spring or a compression spring.

[0028] The sensor component can be arranged on the at least one slider, and the magnet can be arranged on the at least one guide. Alternatively, the magnet can be arranged on the at least one slider, and the sensor component can be arranged on the at least one guide. Thus, the positions of the sensor component and the magnet relative to each other can be chosen such that, in each cycle, the magnet is detected by the sensor component, e.g. the magnet passes the sensor component, or vice versa. As a result, in each cycle, any deviation due to an interfering field is taken into account or eliminated.

[0029] According to a third aspect, a robot, in particular an industrial robot, is presented. The robot has an apparatus as already described herein. Additionally or alternatively, the apparatus has a retraction system as already described herein.

[0030] According to a fourth aspect, a method for monitoring a retraction system is presented. The retraction system has at least one spring. At least one capacitor is connected or interconnected with the at least one spring such that the connection or interconnection of the at least one spring and the at least one capacitor forms an oscillating circuit. The method comprises determining information related to a frequency of the oscillating circuit. The method comprises deriving information related to a length of the at least one spring from the information related to the frequency of the oscillating circuit.

[0031] Although some aspects described above have been described with respect to an apparatus, these aspects can also be implemented in a corresponding manner in a retraction system, a robot, and / or a method. BRIEF DESCRIPTION OF DRAWINGS

[0032] The present disclosure will be further explained with reference to the drawings. These drawings show schematically:

[0033] Figure 1 Block diagram of an apparatus according to possible exemplary embodiments;

[0034] Figure 2 Flow chart of a method according to exemplary embodiments;

[0035] Figure 3 Retraction system having an apparatus according to possible exemplary embodiments;

[0036] Figure 4a , 4b Spring in different states; and

[0037] Figure 5 Possible evaluation of a plurality of springs. DETAILED DESCRIPTION

[0038] In the following, specific details are set forth in order to provide a thorough understanding of the present disclosure. However, persons of ordinary skill in the art will realize that the present disclosure can be practiced without some or all of the specific details. For example, specific configurations and forms are described in the following text, which should not be considered limiting.

[0039] Figure 1 A device 10 for monitoring a retraction system is schematically shown. Figure 1 The retraction system is not shown in. The device 10 has a spring 12. The spring 12 is part of the retraction system. In the device 10, the spring 12 is used as a coil. The device 10 further has a capacitor 14. The capacitor 14 and the spring / coil 12 are connected / interconnected to each other such that an oscillation circuit 16, more specifically an LC oscillation circuit, is formed by the connection / interconnection. L here denotes the inductance of the spring / coil 12. C here denotes the capacitance of the capacitor 14. In Figure 1 In, the capacitor 14 is connected in series with the spring / coil 12, for example. Thus, Figure 1 The oscillation circuit 16 in is configured as a series oscillation circuit, for example. Alternatively, the capacitor 14 and the spring / coil 12 can be connected in parallel to each other. In this case, the oscillation circuit 16 is configured as a parallel oscillation circuit. In Figure 1 In, for simplicity and clarity, only the spring / coil 12 and the capacitor 14 as part of the oscillation circuit 16 are shown. However, the oscillation circuit 16 can have further elements, which can be neglected for explaining the function of the oscillation circuit 16. For example, the oscillation circuit 16 can further have one or more resistors and one or more current / voltage sources. Although, for the sake of clarity, Figure 1 In is shown only one spring / coil 12 and only one capacitor 14, but the device 10 is not limited to this number. The device 10 can have more than one spring / coil 12 and / or more than one capacitor 14.

[0040] The device 10 further has a frequency determination component 20. The frequency determination component 20 is connected or coupled with the oscillation circuit 16 such that the frequency determination component 20 is able to determine information about / related to the frequency of the oscillation circuit 16. The device 10 further has an evaluation unit 30. The evaluation unit 30 is connected / couplable to the frequency determination component 20. The evaluation unit 30 is connected / couplable to the frequency determination unit 20 such that the evaluation unit 30 can receive information about / related to the frequency of the oscillation circuit 16 from the frequency determination circuit 20 or information derived from the information about / related to the frequency of the oscillation circuit 16.

[0041] Reference will now be made to Figure 2The flowchart of Fig. 1 outlines the basic working principle of the device 10. In step S202, the frequency determining component 20 determines information related / concerning the frequency of the oscillation circuit 16. In step S204, the evaluation unit 30 derives information related / concerning the length of the at least one spring / coil 12 from the information related / concerning the frequency of the oscillation circuit 16.

[0042] Further possible details and modifications of the exemplary embodiments of Figures 3 to 5 will now be described in connection with Figure 1 and Figure 2 .

[0043] Figure 3 A retraction system 100 is schematically shown. The retraction system 100 can be used / in industrial robots. The retraction system 100 can be part of a line guiding device or a supply device for an industrial robot, or can form a line guiding device or a supply device. The retraction system 100 has a spring 12. The retraction system 100 further has a slider 110 and a guide 120. The slider 110 is arranged on the guide 120 and guided by the guide 120. The guide can have e.g. one or more guide rails, which are engaged into the slider 110 or vice versa. The slider 110 can perform a translational movement on the guide 120. The slider 110 is connected to the spring 12. In Figure 3 , the spring 12 is configured as e.g. a tension spring. Alternatively, it can also be configured as a different type of spring 12, e.g. a compression spring. In Figure 3 , the starting position of the spring 12 and the slider 110 is shown by way of example. If the slider 110 is translated on the guide 120 under the effect of an external force from this starting position in a direction opposite to the spring 12 and opposite to the pulling force of the spring 12, the spring 12 is deflected. If the external force on the slider 110, which caused the translational movement of the slider 110, is removed, the slider 110 moves automatically back to its starting position due to the pulling force of the spring 12. The spring 12 contracts and relaxes again.

[0044] In the case of a compression spring as the spring 12, the spring 12 is compressed in its starting position, stretched under the effect of an external force, and compressed again when the external force is removed. That is, the spring 12 will change its length when loaded. Thus, the coupling factor of the individual windings changes. This in turn changes its inductance. In the case of a compression spring (see Figure 4a ), the individual windings are closely adjacent and better coupled to each other, so the inductance increases. On the other hand, in the case of a tension spring ( Figure 4b ), the windings are further apart and worse coupled, so the inductance decreases. Thus, by measuring the inductance, the length of the spring 12, and thus indirectly the travel of the slider 110 connected to the spring 12, can be determined.

[0045] The spring 12 is not only shown in Figure 3 as part of the retraction system 100, but also in the right part of the figure as part of an electric circuit. In this electric circuit, the spring 12 is used as a coil, and is therefore referred to in the following as spring / coil 12. As Figure 1 indicated, the spring / coil 12 is connected to a capacitor, and forms together with the capacitor (and if necessary other elements) an oscillation circuit. This oscillation circuit is shown in Figure 3 for example as an oscillator 18 or as part thereof. The oscillator 18 is an oscillator with variable frequency. The frequency of the oscillator 18 can thus be changed depending on the stretching and compression, i.e. the length, of the spring / coil 12. By way of example only, a frequency range of 280 to 400 kHz for the oscillator 18 can be mentioned here. In Figure 3 , the spring / coil 12 is shown separately from the oscillator 18, but the spring / coil is in fact part of the oscillation circuit, and is therefore also part of the oscillator 18. In order to emphasize the importance of the spring / coil 12 in both the retraction system 100 and the electric circuit, the spring / coil 12 is shown separately from the oscillator 18 in the figure.

[0046] The device 10 also has an amplifier 22 and a pick-up 24.

[0047] The device 10 also has a reference oscillator or reference circuit. In Figure 3 , the reference oscillator or reference circuit is for example configured as a piezoelectric oscillator. The piezoelectric oscillator has a piezoelectric resonator 42, for example configured as a piezoelectric crystal, and an oscillator 44 with a constant frequency. An amplifier 46 is connected downstream of the oscillator 44. The output of the pick-up 24 and the amplifier 46 are connected to a counter 26. Both the pick-up 24 and the amplifier 46 generate from their respective analog input signals a digital clock which is respectively input into the counter 26. The output of the counter 26 is connected to a digital-to-analog converter 28.

[0048] The device 10 also has a magnet 50, for example in the form of a permanent magnet. The device 10 also has a sensor 52, which in Figure 3 is for example configured as a Hall sensor. The sensor 52 is configured to detect the magnet 50, or more precisely the magnetic field of the magnet 50. More specifically, the sensor 52 detects the magnetic field of the magnet 50 when the magnet 50 is very close to the sensor 52 such that the distance between the magnet 50 and the sensor 52 is below a predetermined limit value.

[0049] In Figure 3In this case, the magnet 50 is arranged on the slider 110, for example, and the sensor 52 is arranged on the guide 120. Alternatively, however, the magnet 50 can be arranged on the guide 120 and the sensor 52 can be arranged on the slider 110. Thereby, the distance between the magnet 50 and the sensor 52 in the direction of extension of the guide 120 is determined such that the magnet 50 passes the sensor 52 or approaches the sensor 52 at predetermined time intervals. For example, in the starting position of the slider 110, the distance is determined such that the magnet 50 passes or approaches the sensor 52 at least once per cycle of the oscillation circuit, or the distance falls below a predetermined limit value.

[0050] To determine the stroke by means of the spring / coil 12, the physical properties of the spring when stretched / compressed are used. The spring / coil 12 will change its length when loaded. As a result, the coupling factor of the individual windings changes. This in turn changes its inductance. In the case of a compressed spring ( Figure 4a ), the individual windings are in close proximity and better coupled to one another. As a result, the inductance of the spring / coil 12 in the device increases. On the other hand, in the case of a stretched spring ( Figure 4b ), the windings are further apart and less well coupled. As a result, the inductance of the spring / coil 12 decreases. By determining / measuring the inductance, the length of the spring and thus indirectly the stroke can be determined.

[0051] The length of the spring / coil 12 is measured here by means of an arrangement in the form of an LC oscillation circuit. The spring / coil 12, more specifically the return spring 12, represents the inductance of the LC oscillation circuit. The length change caused by the displacement movement of the slider results in a change in the inductance of the spring / coil 12. As a result of the change in the inductance of the spring / coil 12, the frequency of the LC oscillation circuit, which functions as an oscillator 18, changes.

[0052] The frequency of the LC oscillation circuit is determined by a frequency determination component 20. This can be achieved, for example, by determining the number of pulses of a reference oscillation circuit. In Figure 3 , a counter 26 detects or receives the pulses of the LC oscillation circuit and the pulses of the reference oscillation circuit. The counter 26 detects or receives the pulses during a predetermined time period, for example during half a cycle of the LC oscillation circuit. By way of example only, a counter value of from 200 to 3800 can be mentioned here as being detected or received by the counter 26.

[0053] The counter value is converted into a voltage by means of a digital-to-analog converter 28. By way of example only, the voltage value of the voltage can have a value of 0.2 to 3.8 V. The voltage value can be emitted to the evaluation unit 30. In this way, information can be simply emitted to the evaluation unit 30. It is also conceivable to omit the digital-to-analog converter 28 and to use the digital frequency-counter-value of the counter 26 for further data processing. For example, the digital frequency-counter-value as determined by the counter 26 can be forwarded to the evaluation unit 30 or further data processing can be carried out on the basis of the digital counter value in the counter 26. It is thus conceivable to carry out further evaluations in the digital-to-analog converter. In other words, the counter 26 can have or be configured as the evaluation unit 30 or the evaluation unit 30 can have or be configured as the counter 26.

[0054] In order to reduce measurement errors or ideally completely avoid measurement errors, in particular voltage shifts of the LC oscillation circuit due to interference fields occurring in the industrial environment, for calibration, a sensor 52, for example a Hall sensor, is also arranged or installed on the guide 120 and a magnet 50 is arranged or installed on the slider 110 (or vice versa). When the sensor 52 passes, the (previously known) position is compared with the position determined by the LC frequency in order to eliminate deviations (i.e. shifts) occurring in the signal. The position of the Hall sensor 52 is chosen such that the Hall sensor 52 is passed by the slider 110 in each cycle, if possible. More specifically, when the sensor 52 detects the magnet 50, the length or length change of the spring / coil 12 is determined and compared with a previously known, for example stored, length or length change, which should occur at this position of the slider 110. If a deviation between the measured length or length change of the spring / coil 12 and the previously known, for example stored, length or length change of the coil / spring 12 is determined, this deviation is taken into account in the calculation of the length or length change in this cycle and / or in additional cycles, for example in all cycles. In one embodiment variant, the deviation is determined at least once per cycle and taken into account in all calculations in the same cycle. In this way, the accuracy of the determination of the length or length change of the spring / coil 12 is improved.

[0055] Although the application has only been described for one spring, the application is not limited thereto. Thus, in a system with multiple springs 12, it is also possible to connect the springs in parallel or in series, as indicated in Figure 5 In this case, the total inductance resulting from the individual connections can be used to determine the length or length change of the springs 12 and thus the stroke of the slider 110. In this case, it is conceivable to use only the fixed ends of the springs 12 to connect or contact the evaluation unit 30. In this case, the mechanical setup is simple and stable.

[0056] To improve the sensitivity of the measuring method, a greater inductance change can be achieved by positioning one or more core parts partially or completely in the system, and the compression and / or stretching of the spring causes a change / overlap in the relative position between the spring and the core. The shape of the core can be changed to achieve different types of effects (e.g. linear or exponential change in inductance). As an alternative to a core inside the spring, a ring around the spring can also be used.

[0057] By measuring the length of the spring and thus the travel of the slider 110, additional information can be obtained, for example, periodic detection, mechanical load, spring force, displacement speed, acceleration, etc., which can be relevant for statistical evaluation and preventive maintenance. The above-described method with the corresponding settings can be used widely, in particular in the case of energy supply and retraction devices used on industrial robots.

Claims

1. A device (10) for monitoring a retraction system (100) of a line guiding device or a supply device of a robot having at least one spring (12), wherein The device (10) has - at least one capacitor (14) which is interconnected with the at least one spring (12) such that the interconnection of the at least one spring (12) and the at least one capacitor (14) forms an oscillation circuit (16); - a frequency determination component (20) which is configured to determine information about a frequency of the oscillation circuit (16); and - an evaluation unit (30) which is configured to derive information about a length of the at least one spring (12) from the information about the frequency of the oscillation circuit (16), wherein the frequency determination component (20) is configured as or has a digital frequency determination component and the digital frequency determination component is configured to determine a number of pulses which occur in the oscillation circuit (16) during a predetermined time period as the information about the frequency of the oscillation circuit (16).

2. The apparatus (10) of claim 1, wherein The evaluation unit (30) is configured to derive information about a length change of the at least one spring (12) from the information about the frequency of the oscillation circuit (16) as the information about the length of the at least one spring (12).

3. The apparatus (10) according to any one of claims 1 to 2, wherein, The frequency determination component (20) is configured to determine the information about the frequency of the oscillation circuit (16) taking into account information about a frequency of a reference oscillation circuit.

4. The apparatus (10) according to any one of claims 1 to 2, wherein, The device (10) has a digital-to-analog converter (28) which is configured to convert the information about the frequency of the oscillation circuit (16) into a voltage value.

5. The apparatus (10) of claim 4, wherein, The digital-to-analog converter (28) is configured to emit the voltage value to the evaluation unit (30) and the evaluation unit (30) is configured to derive the information about the length of the at least one spring (12) from the emitted voltage value.

6. The apparatus (10) according to any one of claims 1 to 2, wherein, The retraction system comprises at least one slider (110) which is connected to the at least one spring (12); at least one guide (120) which is configured to guide the at least one slider (110); The device (10) further has a magnet (50) and a sensor component (52) for detecting the magnet (50), wherein the sensor component (52) is arranged on the at least one slider (110) and the magnet (50) is arranged on the at least one guide (120); or the magnet (50) is arranged on the at least one slider (110) and the sensor component (52) is arranged on the at least one guide (120).

7. The apparatus (10) of claim 6, wherein The evaluation unit (30) is configured to, when the sensor component (52) detects the magnet (50), compare the information about the length of the at least one spring (12) determined at the time of the detection with previously known information about the length of the at least one spring (12) and to determine information about a deviation from the comparison.

8. The apparatus (10) of claim 6, wherein, The sensor component (52) has or is configured as a Hall sensor.

9. A retraction system (100) having - at least one spring (12); - at least one slider (110) which is connected to the at least one spring (12); - at least one guide (120) configured to guide the at least one slider (110); and - the device (10) according to any one of claims 1 to 8.

10. Retraction system (100) according to claim 9, wherein a sensor component (52) is arranged on the at least one slider (110) and a magnet (50) is arranged on the at least one guide (120); or the magnet (50) is arranged on the at least one slider (110) and the sensor component (52) is arranged on the at least one guide (120).

11. Robot having a device (10) according to any one of claims 1 to 8 or a retraction system (100) according to claim 9 or 10.

12. A method for monitoring a retraction system (100) of a line guiding device or a supply device of a robot having at least one spring (12), wherein at least one capacitor (14) is interconnected with the at least one spring (12) such that the interconnection of the at least one spring (12) and the at least one capacitor (14) forms an oscillation circuit (16) and the system frequency determining component (20) is configured to determine information about a frequency of the oscillation circuit (16), wherein the frequency determining component (20) is in the form of or has a digital frequency determining component, wherein the method comprises: - determining information about a frequency of the oscillation circuit (16); - deriving information about a length of the at least one spring (12) from the information about the frequency of the oscillation circuit (16); and - determining a number of pulses occurring in the oscillation circuit (16) during a predetermined time period as the information about the frequency of the oscillation circuit (16).

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