Monitoring device for solenoid valve of compressed air system of vehicle, system comprising solenoid valve, monitoring device and control device, and method for monitoring solenoid valve

Abstract

The invention relates to a monitoring device (3) for a solenoid valve (2) of a compressed air system of a vehicle and to a method for monitoring a valve. The monitoring device (3) has a current detection device (5), which is designed to detect a supply current (I) of the solenoid valve (2), and an evaluation device (6), which is designed to evaluate a time profile of the supply current (I) detected during a switching process of the solenoid valve (2), and providing state information about the state of the solenoid valve (2) in relation to the time curve.

Description

Technical Field

[0001] The invention relates to a monitoring device for a solenoid valve of a compressed air system of a vehicle and to a method for monitoring a solenoid valve, in particular for safety-related applications. Background Art

[0002] Due to system requirements and safety requirements, it is necessary to monitor the effectiveness of the solenoid valve. In this effectiveness monitoring, it is monitored whether the solenoid valve is functioning properly, that is, whether the solenoid valve is switching as specified.

[0003] In such monitoring, when the solenoid valve is switched, a pressure detection device is used to check whether the desired or expected pressure is set before and / or after the solenoid valve. For this purpose, the pressure is measured and an evaluation device is used to check whether the desired pressure has been set. However, for this purpose, it has been necessary to provide a pressure switch or a pressure sensor for each individual solenoid valve to determine the pressure, and to provide additional electronics for the evaluation device, which results in high costs for such monitoring devices.

[0004] Furthermore, there is the problem that if no pressure is applied to the solenoid valve, such as in a test before the vehicle starts to move, effectiveness monitoring by detecting the pressure is not possible.

[0005] In order to avoid this problem, solenoid valves with additional sensor components can be used, which monitor the position of the solenoid valve armature and report this position as a state. It is possible to monitor the effectiveness, i.e., to check the switching of the solenoid valve, via the position of the armature. However, such solenoid valves are relatively expensive because they contain additional electronics. In addition, the signals emitted by the additional electronics must be read in and evaluated on the control side. Summary of the invention

[0006] The object of the present invention is therefore to eliminate the above-mentioned disadvantages and to provide for this purpose a monitoring device for a solenoid valve and a corresponding system and method, which allow effectiveness monitoring without the need for additional sensor complexity.

[0007] This object is achieved by a monitoring device according to claim 1, a system comprising a solenoid valve, a monitoring device and a control device according to claim 7, and a method according to claim 8. Advantageous developments of the invention are contained in the dependent claims.

[0008] According to one aspect of the present invention, a monitoring device for a solenoid valve of a compressed air system of a vehicle has a current detection device and an analysis device, wherein the current detection device is configured to detect a power supply current of the solenoid valve, and the analysis device is configured to analyze and process a time variation curve of the power supply current detected during a switching process of the solenoid valve and provide status information about the status of the solenoid valve related to the time variation curve.

[0009] By analyzing the time variation curve of the supply current by the analysis and processing device, the analysis and processing device can determine whether its time variation curve during the switching process of the solenoid valve is within the correct operating range of the solenoid valve, that is, whether it is within the range of the typical time variation curve for the corresponding characteristics of the solenoid valve. If it is determined to be an atypical curve, it is assumed that the solenoid valve is in a fault state. Therefore, it can be determined without using an additional sensor device whether the function is normal and fault-free, or whether there is a possible potential fault. Because it is common in today's systems to monitor the supply current of the solenoid valve for other functions, such as by shunt resistors and corresponding detection electronics, the current detection device already exists and therefore does not require additional costs. In addition, the solenoid valve is usually controlled by an electronic control device, wherein the analysis and processing device according to the present invention can be integrated into the existing or originally required electronic control device without high additional costs in mass production, so that the analysis and processing according to the present invention can also be performed without or with very little additional costs.

[0010] The time profile during operation of the solenoid valve (i.e., the possible multiple increases and decreases within a predetermined time period) is defined as the time profile of the supply current and is provided to the evaluation device. However, a one-time sudden increase or decrease in the supply current caused by switching on or off is not considered as a time profile, because no state information related to this profile can be provided here.

[0011] According to an advantageous embodiment of the monitoring device, the evaluation device is designed to evaluate the supply current during the entire switching process of the solenoid valve.

[0012] The entire switching process of the solenoid valve is preferably understood to mean the evaluation of the supply current from the time when the solenoid valve is actuated with the supply voltage until the end of the switching process of the solenoid valve, ie until the desired current flow of the solenoid valve is reached.

[0013] By means of the evaluation during the entire switching process, the behavior of the solenoid valve can be monitored during the entire switching process, so that, for example, an anomaly that occurs only in a specific phase of the switching process can be determined. The anomaly is preferably determined in the evaluation device by comparing the time profile of the detected supply current with a typical, correct time profile and by deviations outside a predefined tolerance range.

[0014] In a further advantageous embodiment of the monitoring device, the evaluation device is designed to determine a fault or the absence of a fault as part of an evaluation of the entire switching process of the solenoid valve as state information and to make this state information available as a result of the effectiveness monitoring.

[0015] Effectiveness monitoring is understood to be monitoring that checks whether the function of the solenoid valve complies with regulations. If the profile of the supply current during the switching process is typical and correct, a positive result, i.e. "unimpeded operation", is preferably provided as status information related to the detected profile of the supply current. Alternatively or additionally, preferably a "fault" of the solenoid valve is provided as status information when an anomaly occurs in the profile of the supply current during the switching process. Thus, effectiveness monitoring can be carried out simply and without the need for additional sensor devices.

[0016] According to a further advantageous embodiment of the monitoring device, the evaluation unit is designed to determine a “maintenance requirement” and to output or make available this “maintenance requirement” as status information.

[0017] In this state, the solenoid switch valve can continue to operate at present, but is likely to fail in the near future.

[0018] Based on the time profile of the supply current detected during the entire switching process or only during a part of the switching process, wear or a fault can be inferred when a predetermined characteristic of the curve occurs, for example, when a higher current occurs at a specific time due to increased friction. As a result, status information of a maintenance requirement can be provided in a simple manner, so that, for example, the corresponding solenoid valve can be taken into account in subsequent maintenance, and there is no risk that the corresponding solenoid valve is not taken into account in the subsequent maintenance and fails shortly after the maintenance.

[0019] In a further advantageous embodiment of the monitoring device, the evaluation unit is designed to infer an input-side pressure at the solenoid valve from the time profile of the supply current and to provide this pressure as state information.

[0020] Since the actuating force of the magnet on the solenoid valve depends on the inlet-side pressure at the solenoid valve, the inlet-side pressure can be estimated by detecting the supply current which is dependent on the actuating force, without requiring an additional sensor for the inlet-side pressure.

[0021] According to another advantageous embodiment of the monitoring device, the evaluation unit has a neural network which is designed to determine by independent learning typical current curves for a correct state of the solenoid valve and atypical current curves for a fault of the solenoid valve and to provide these current curves as state information.

[0022] When the detected supply current is processed by a neural network, the current profile during fault-free operation of the solenoid valve can be easily learned, compared to other methods, for example, which estimate the state of the solenoid valve based on a model. This can also be done outside the neural network, so that a corresponding data set is provided for effectiveness monitoring in the neural network. In this case, for example, effectiveness monitoring can be carried out so that functional faults are determined by detecting anomalies in the current profile, and other characteristics or possible potential problems can be easily identified.

[0023] According to another aspect of the present invention, a system is provided, which includes a solenoid valve, a monitoring device according to the present invention of the above-mentioned embodiment, and a control device, wherein the control device is configured to control the solenoid valve, wherein the system is configured to control the supply voltage for the solenoid valve based on status information provided by the monitoring device.

[0024] Such a system can, for example, control the solenoid valve with minimal energy input, so that reliable switching of the solenoid valve can be achieved with minimal energy input. This can save energy on the one hand and operate the solenoid valve as gently as possible to increase its service life on the other hand. This will be explained in detail below.

[0025] According to another aspect of the present invention, a method for monitoring a solenoid valve of a compressed air system of a vehicle comprises the following steps: detecting a supply current of the solenoid valve by means of a current detection device; analyzing and processing a time variation curve of the supply current detected during a switching process of the solenoid valve in the form of state information of the solenoid valve related to the time variation curve by means of an analysis and processing device; and providing the state information.

[0026] By analyzing the time profile of the supply current, a typical time profile for a fault-free function can be determined without using additional sensor devices. Thus, the solenoid valve can be monitored without or with little additional effort and / or status information about potential problems or faults of the solenoid valve can be provided.

[0027] In an advantageous embodiment of the method, the profile of the supply current is evaluated by means of a neural network based on the results of the training by means of machine learning.

[0028] In this case, an evaluation algorithm can be generated based on the input data of the detected supply current and the results ascertained during the learning process for the corresponding state information, without having to define relationships between the input data in a complex manner.

[0029] According to an advantageous embodiment of the method, the supply current is evaluated during the entire switching process of the solenoid valve.

[0030] By means of the evaluation during the entire switching process, the behavior of the solenoid valve during the entire switching process can be monitored so that, for example, anomalies which occur only in certain phases of the switching process can be identified.

[0031] An anomaly is preferably determined in the evaluation device by comparing the detected time profile of the supply current with a typical, correct time profile and by deviations outside a predefined tolerance range.

[0032] According to a further advantageous embodiment of the method, the expected service life of the solenoid valve is provided as the status information.

[0033] The expected service life of the solenoid valve can be easily provided as status information from the detected time profile of the supply current.

[0034] In a further advantageous embodiment of the method, a probability of failure of the solenoid valve is provided as the status information.

[0035] The failure probability of the solenoid valve can be easily provided as status information from the detected time profile of the supply current.

[0036] In an advantageous embodiment of the method, the result of monitoring the effectiveness of the switching function of the solenoid valve is provided as the status information.

[0037] In this case, the functionality of the solenoid valve can be determined easily without additional sensor components.

[0038] In a further advantageous embodiment of the method, a maintenance request for the required maintenance is provided as status information.

[0039] The state of the solenoid valve can be easily detected from the detected time profile of the supply current and thus indicate a maintenance requirement without the need for additional sensor devices.

[0040] According to a further advantageous embodiment of the method, the pressure acting on the solenoid valve on the input side is provided as state information.

[0041] Since the power for actuating the solenoid valve depends on the inlet-side pressure at the solenoid valve, the inlet-side pressure can be estimated by detecting the supply current without requiring an additional sensor for detecting the inlet-side pressure.

[0042] The invention is explained below with reference to the accompanying drawings and exemplary embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In the figure:

[0044] Figure 1 A circuit diagram showing a system according to the present invention;

[0045] Figure 2 a diagram showing a current profile during a switching process; and

[0046] Figure 3 A flow chart shows a method for monitoring a solenoid valve of a compressed air system of a vehicle. DETAILED DESCRIPTION

[0047] Figure 1 The circuit diagram of the system 1 according to the invention is shown. The system 1 comprises a solenoid valve 2 of a compressed air system of a vehicle, a monitoring device 3 for the solenoid valve 2 and a control device 4 which is designed to control the solenoid valve 2 .

[0048] The monitoring device 3 has a current detection device 5 and an evaluation device 6. In an alternative embodiment, the monitoring device 3 is integrated into at least one of the control device 4, the current detection device 5 and the evaluation device 6.

[0049] The solenoid valve 2 has a switching valve that can allow or block the flow of a fluid through the switching valve via a valve body seated on a valve seat. The valve body is connected to an armature moved by a magnet to seat on the valve seat and block or allow flow.

[0050] The current detection device 5 detects the supply current I of the solenoid valve 2. For this purpose, the current detection device 5 has a shunt resistor and detection electronics cooperating therewith. In an alternative embodiment, the supply current I is detected by a current transformer.

[0051] The evaluation device 6 evaluates the detected time profile of the supply current I and provides state information related to the time profile. The time profile of the supply current is defined as a time profile, i.e., a possible multiple rise and fall. However, a simple sudden rise or fall of the supply current I caused by switching on or off is not considered a time profile, because no state information related to this profile can be provided here.

[0052] In particular, the evaluation device 6 evaluates the time profile of the supply current I during the entire switching process. That is, the supply current I is evaluated from the time when the solenoid valve 2 is actuated with the supply voltage until the end of the switching process of the solenoid valve 2, that is, until the desired current of the solenoid valve is reached. In an alternative embodiment, the time profile of the supply current is not evaluated during the entire switching process, but only in a section of the switching process in which experience has shown that relevant state information can be expected.

[0053] The analysis device 6 has a neural network in this embodiment. In particular, an autoencoder is used as a neural network in this embodiment. The autoencoder is able to detect deviations from a "normal" state. The state information can be provided using the results of machine learning. In an alternative embodiment, a model-based observer is used instead of a neural network to estimate the state of the solenoid valve 2 and output the state information. In this case, deviations from the simulated physical properties are monitored. In the event of a deviation in the current / time characteristic, a solenoid valve malfunction can be inferred.

[0054] The system 1 uses the status information to control the supply voltage for the solenoid valve 2. In an alternative embodiment, the supply voltage is not controlled according to the status information, but the status information is only used to detect a status of the solenoid valve 2 that requires other actions such as immediate repair, consideration at the next maintenance, etc.

[0055] Figure 2 A diagram is shown with different time current profiles of the supply current I during a switching process. The time in milliseconds [ms] after the activation of the solenoid valve 2 is plotted on the abscissa and the supply current I of the solenoid valve 2 in amperes [A] is plotted on the ordinate. These time profiles of the supply current I are detected by the current detection device 5, provided to the evaluation device 6, and evaluated by the evaluation device 6.

[0056] In the diagram, the possible ranges of the supply current I operation after the time of actuating the solenoid valve 2 are plotted in each case. In particular, the range shown with vertical hatching shows the supply current I generated when the solenoid valve 2 is actuated at an input-side pressure of 0 bar to 2 bar. The range shown with horizontal dashed hatching shows the supply current I generated when the solenoid valve 2 is actuated at an input-side pressure of 2 bar to 4 bar.

[0057] The time profile of the corresponding supply current I can be divided essentially into three sections i, ii, iii.

[0058] In the first section i, the supply current I increases. The rising gradient G of the supply current I corresponds to an electrical constant, for example, the solenoid coil impedance of the solenoid valve 2. During this rising process, the armature of the solenoid valve 2 has not yet moved.

[0059] In the second section ii, the armature of the solenoid valve 2 moves from the time point B, which depends on the input side pressure of the solenoid valve 2 and is shown with a slash. After the armature movement begins, the supply current I first decreases and then increases. Finally, in the third section iii, the supply current I reaches the desired current value applied when the solenoid valve 2 is opened, and this current value can be within a preset bandwidth. The time point B and the subsequent magnitude of the supply current I, especially the supply current magnitude I in the second section ii, all depend on the input side pressure of the solenoid valve 2. However, the basic time variation curve of the supply current I is a characteristic of the solenoid valve 2.

[0060] As long as the time variation curve of the detected supply current I is consistent with the typical, i.e., characteristic, time variation curve of the supply current I of the normally operating solenoid valve 2, it can be considered that the solenoid valve 2 is switched normally, i.e., the solenoid valve 2 has no faults, and the corresponding status information is output. Thus, the effectiveness of the solenoid valve 2 is monitored by the analysis and processing device 6.

[0061] For example, when the current intensity is detected to be zero, there is a fault, and it can be considered that there is a pipeline rupture in the input pipeline or inside the solenoid valve 2, and corresponding status information is provided.

[0062] If it is determined that the supply current I increases above the stored value (usually occurs when the armature starts to move), it can be concluded that the armature is not moving, the solenoid valve 2 is blocked and therefore malfunctioning, and corresponding status information of this malfunction is provided.

[0063] If an abnormal increase in the supply current I is detected at a specific point in time or time period in the profile of the supply current I, it can be inferred from this that the friction inside the solenoid valve 2 has increased. The evaluation device 6 then provides status information that requires maintenance.

[0064] In a development of this specific embodiment, previously stored empirical values ​​regarding future wear are also incorporated and provide status information regarding the expected service life of the solenoid valve 2 .

[0065] Furthermore, from the time curve of the supply current I about the time point B at which the armature of the solenoid valve 2 starts to move, the evaluation device 6 outputs which input-side pressure is present on the solenoid valve 2 and provides corresponding state information. The input-side pressure is determined from empirical values.

[0066] In alternative embodiments, all of the above status information is provided, or only a portion thereof is selectively provided.

[0067] Figure 3 A flow chart shows a method for monitoring a solenoid valve 2 of a compressed air system of a vehicle.

[0068] During operation, the monitoring device 3 detects the supply current I of the solenoid valve 2 in a step S1 by means of the current detection device 5 .

[0069] The detected supply current I is then provided to the analysis device 6 in step S2 and is analyzed by the analysis device 6 in the form of state information of the solenoid valve related to the time variation curve during the switching process of the solenoid valve 2, wherein the data about the switching process are optionally provided by the control device 4. Here, the supply current I flowing during the entire switching process of the solenoid valve 2 is analyzed, that is, from the moment when the solenoid valve 2 is controlled by the supply voltage until the switching process of the solenoid valve 2 ends, that is, until the desired current of the solenoid valve is reached. In an alternative embodiment, only a partial area of ​​the supply current I flowing during the switching process is analyzed. The partial area of ​​the switching process is determined based on empirical values. For example, the part in which the input side pressure can be obtained from the current variation curve is analyzed.

[0070] The evaluation device 6 then provides status information related to the time profile in step S3 .

[0071] In order to monitor the function, ie the effectiveness, of the solenoid valve, a neural network is used in one embodiment, which uses a feedforward neural network as the neural network, in which information flows only one way without looping, or an autoencoder.

[0072] When using neural networks, training is performed in advance. In this case, data corresponding to correct ("normal") operation are detected with statistical deviations. These data are then used for training to detect abnormal situations. In a further step, different fault modes are compensated during training, which can be used to classify the fault modes. This training or learning is performed as so-called "supervised learning", in which so-called labels are given to the data based on previously acquired knowledge.

[0073] The autoencoder has a neural network which, during learning, adapts so-called hyperparameters so that, despite the compression, the reconstructed output data of the network are very close to the input data. The deviation of the reconstructed output data from the input data is a measure of the quality of the function monitoring, i.e., the degree of proximity of the input data to the "normal / correct" function of the solenoid valve 2. The function of detecting abnormal situations can be tested by intentionally generating a fault data set. At the same time, the fault data set is used to train the neural network for classification.

[0074] So-called convolutional neural networks are used to determine the input-side pressure and the remaining service life. In alternative embodiments, other types of neural networks are used.

[0075] Machine learning, in particular so-called supervised learning, is performed with the aid of the neural network of the evaluation device 6. In this case, data are input in the input level, results are calculated in the intermediate level, and these results are output in the output level. During learning or training, i.e., during input of data and verification of the expected results of the input data, the parameters used for the calculation are gradually changed by the neural network so that the desired results are produced.

[0076] By repeating this training several times, the parameters are optimized, so that the results are obtained more reliably. In addition, other influencing factors can also be added as inputs later, which are then taken into account when determining the result. Using the existing training data, for example, predictions about the function can be derived, predictions about the remaining service life can be determined, and the inlet pressure of the valve can be estimated.

[0077] use Figure 2 As input, the image of the diagram shown in the figure is used, and by so-called convolutional neural networks, which are used, for example, in particular in the machine processing of image data or audio data, the image of the diagram is not only used for training, but also as input in the application. For diagrams with different curves, which results are associated with different curve characteristics is learned respectively, and then this result is provided as state information. The detected current curve is thus analyzed by the neural network.

[0078] The status information is either displayed on a central display for the respective solenoid valve 2 or, alternatively, is transmitted to a central computer.

[0079] Furthermore, the expected service life of the solenoid valve 2 is provided as status information from the time profile of the supply current I.

[0080] Furthermore, the time profile of the supply current I provides a probability of failure of the solenoid valve 2 and / or a required maintenance of the solenoid valve 2 or a maintenance requirement for replacing the solenoid valve 2 as status information.

[0081] Furthermore, the pressure acting on the solenoid valve on the input side is provided as state information of the solenoid valve.

[0082] Finally, the result of the monitoring of the effectiveness of the switching function of the solenoid valve 2 is made available as status information.

[0083] In an alternative embodiment, not all status information is output, but only one or a few status information is output.

[0084] If the result of the effectiveness monitoring is positive, i.e. the solenoid valve 2 is functioning as intended, the supply voltage for the solenoid valve 2 can optionally be reduced, thereby also reducing the supply current. The solenoid valve 2 can thus be operated at reduced power in order to save energy and extend the service life of the solenoid valve 2. The supply voltage can be repeatedly reduced as long as reliable operation of the solenoid valve 2 is ensured.

[0085] If, on the other hand, the result of the effectiveness monitoring shows that the solenoid valve 2 is not switching as intended, the supply voltage for the solenoid valve 2 can optionally be increased in order to ensure restoration of its functionality.

[0086] Although the present invention has been described with reference to specific features and embodiments, it is apparent that various modifications and combinations may be made to the present invention without departing from the spirit and scope of the present invention. Therefore, the specification and drawings are only regarded as an illustration of the present invention as defined by the appended claims, and are intended to cover all modifications, variations, combinations or equivalents within the applicable scope of the present invention.

[0087] Reference numerals list

[0088] 1 System

[0089] 2 Solenoid valve

[0090] 3 Monitoring equipment

[0091] 4. Control Equipment

[0092] 5. Current detection device

[0093] 6Analysis and processing device

[0094] B The time when the armature of the solenoid valve starts to move

[0095] G Gradient

[0096] I Supply Current

[0097] iThe first section of the time profile of the supply current

[0098] ii The second section of the time variation of the supply current

[0099] iii The third section of the time variation curve of the supply current

Claims

1. A monitoring device (3) for a solenoid valve (2) of a compressed air system of a vehicle, the monitoring device comprising: a current detection device (5), the current detection device being configured to detect a power supply current (I) of the solenoid valve (2), and An evaluation device (6) is designed to evaluate a time profile of a supply current (I) detected during a switching process of the solenoid valve (2) and to provide state information about the state of the solenoid valve (2) related to the time profile.

2. The monitoring device (3) according to claim 1, wherein: The evaluation device (6) is designed to evaluate the time profile of the supply current (I) during the entire switching process of the solenoid valve.

3. The monitoring device (3) according to claim 2, wherein: The evaluation device (6) is designed to determine a fault or the absence of a fault as state information within the scope of an evaluation of the entire switching process of the solenoid valve (2) and to provide this state information as a result of the validity monitoring.

4. The monitoring device (3) according to any one of the preceding claims, wherein: The evaluation unit (6) is designed to determine a “maintenance requirement” and to provide the “maintenance requirement” as status information for required maintenance.

5. The monitoring device (3) according to any one of the preceding claims, wherein: The evaluation unit (6) is designed to infer the input-side pressure at the solenoid valve (2) from the time profile of the supply current and to provide this pressure as state information.

6. The monitoring device (3) according to any one of the preceding claims, wherein: The evaluation unit (6) has a neural network which is designed to determine, by independent learning, typical current profiles for a correct state of the solenoid valve (2) and atypical current profiles for a fault of the solenoid valve (2) and to provide these current profiles as state information.

7. A system (1) comprising a solenoid valve (2), a monitoring device (3) and a control device (4), the monitoring device being a monitoring device according to any one of the preceding claims, the control device being configured to control the solenoid valve (2), wherein: The system (1) is designed to control a supply voltage for the solenoid valve (2) as a function of status information provided by the monitoring device (3).

8. Method for monitoring a solenoid valve (2) of a compressed air system of a vehicle, the method comprising the following steps: - detecting the supply current (I) of the solenoid valve (2) by means of a current detection device (5) (S1); - analyzing (S2) the time profile (I) of the supply current (I) detected during the duration of the switching process of the solenoid valve (2) in the form of state information of the solenoid valve related to the time profile by means of an analysis device (6); and - providing status information related to the time profile (S3).

9. The method according to claim 8, wherein: The profile of the supply current (I) is evaluated by means of a neural network based on the results of the training by means of machine learning.

10. The method according to claim 8 or 9, wherein: The supply current (I) is evaluated during the entire switching process of the solenoid valve (2).

11. The method according to any one of claims 8 to 10, wherein: The expected service life of the solenoid valve (2) is provided as status information.

12. The method according to any one of claims 8 to 11, wherein: The failure probability of the solenoid valve (2) is provided as status information.

13. The method according to any one of claims 8 to 12, wherein: The result of monitoring the effectiveness of the switching function of the solenoid valve (2) is provided as status information.

14. The method according to any one of claims 8 to 13, wherein: Maintenance requirements for required maintenance are provided as status information.

15. The method according to any one of claims 8 to 14, wherein: The pressure acting on the solenoid valve (2) on the input side is provided as state information.

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