阅读说明：本技术 用于确定液压回路装置的健康状态的方法 (Method for determining the state of health of a hydraulic circuit arrangement ) 是由 莫里·巴特勒 马库斯·赫雷拉 于 2020-03-04 设计创作，主要内容包括：本发明涉及一种确定包括至少一个液压流体工作机器(2,3)的液压回路装置的健康状态的方法(25)。该健康状态是至少部分地使用该液压回路装置(1)的实际温度信息(12)与该液压回路装置(1)的预期温度信息(24)的比较来确定(29)的。(The invention relates to a method (25) for determining the state of health of a hydraulic circuit arrangement comprising at least one hydraulic fluid working machine (2, 3). The state of health is determined (29) at least partially using a comparison of actual temperature information (12) of the hydraulic circuit arrangement (1) with expected temperature information (24) of the hydraulic circuit arrangement (1).)

1. A method of determining a state of health of a hydraulic circuit arrangement, in particular a hydraulic circuit arrangement comprising at least one hydraulic fluid working machine, characterized in that the state of health is determined at least partly using a comparison of actual temperature information of the hydraulic circuit arrangement with expected temperature information of the hydraulic circuit arrangement.

2. The method of claim 1, wherein the expected temperature information is determined at least in part from the following group of temperature information acquisition methods: using a fixed temperature; using a temperature based model of the hydraulic circuit arrangement; using a temperature based measurement of the hydraulic circuit arrangement; modifying the temperature based on the operating time; modifying the temperature based on the operating load; modifying the temperature based on the operating load history; modifying the temperature based on an environmental parameter; modifying the temperature based on the actual temperature information history; modifying the temperature based on the hydraulic fluid type; modifying the temperature based on the hydraulic fluid change; the temperature is modified based on the previous health status data.

3. The method of claim 1, wherein the actual temperature information is determined at least in part from the following group of temperature information acquisition methods: measuring the hydraulic fluid temperature; measuring the development of the temperature over time; measuring the mechanical power introduced into the hydraulic circuit arrangement; measuring mechanical power extracted from the hydraulic circuit arrangement; measuring the heat dissipation condition of the hydraulic circuit device to the environment; the measurement results are replaced or modified by calculations.

4. The method according to claim 1, wherein the health status comprises at least one, two or more health status levels, in particular at least one health status level is selected from the following group of health status levels: an indication that the hydraulic circuit arrangement is fully operational; an indication of the number of hours remaining for which the hydraulic circuit arrangement is fully operable; the number of operating hours remaining before preventative maintenance; the number of hours remaining before maintenance; an indication of suggested preventative maintenance; an indication of required preventative maintenance; an indication of a proposed maintenance; an indication of recommended maintenance; an indication of highly recommended maintenance; an indication that the recommended device is unavailable; an indication of an impending failure; an indication of a fault.

5. The method of claim 1, wherein the health status is affected by previous health status information.

6. Method according to claim 1, wherein the health status can be modified from the outside, in particular based on the examination results and/or the maintenance performed.

7. The method of claim 1, wherein the health status is determined at least in part using machine learning methods, processes, and systems.

8. The method according to claim 1, wherein the health status is indicated to an operator of the hydraulic circuit arrangement, stored in a memory device for human reading, and/or transmitted to an external device.

9. The method according to claim 1, wherein the state of health and/or the expected temperature information and/or the actual temperature information is a vector value.

10. A control unit for a hydraulic circuit arrangement, which control unit is designed and arranged in such a way that the method according to claim 1 is performed at least occasionally.

11. The control unit of claim 8, wherein the control unit is an electronic control unit, a programmable control unit, an electronic controller, and/or a device comprising a digital processing device.

12. A hydraulic circuit arrangement, wherein the hydraulic circuit arrangement is at least occasionally operated according to the method of claim 1.

13. The hydraulic circuit arrangement according to claim 10, for a mobile device, in particular for a non-road vehicle and/or a construction floor vehicle.

14. The method of claim 1, wherein the actual temperature information is determined at least in part from the following group of temperature information acquisition methods: measuring the hydraulic fluid temperature; measuring the development of the temperature over time; measuring the mechanical power introduced into the hydraulic circuit arrangement; measuring mechanical power extracted from the hydraulic circuit arrangement; measuring the heat dissipation condition of the hydraulic circuit device to the environment; the measurement results are replaced or modified by calculations.

15. The method according to claim 2, wherein the health status comprises at least one, two or more health status levels, in particular at least one health status level is selected from the group of health status levels consisting of: an indication that the hydraulic circuit arrangement is fully operational; an indication of the number of hours remaining for which the hydraulic circuit arrangement is fully operable; the number of operating hours remaining before preventative maintenance; the number of hours remaining before maintenance; an indication of suggested preventative maintenance; an indication of required preventative maintenance; an indication of a proposed maintenance; an indication of recommended maintenance; an indication of highly recommended maintenance; an indication that the recommended device is unavailable; an indication of an impending failure; an indication of a fault.

16. The method according to claim 3, wherein the health status comprises at least one, two or more health status levels, in particular at least one health status level is selected from the group of health status levels consisting of: an indication that the hydraulic circuit arrangement is fully operational; an indication of the number of hours remaining for which the hydraulic circuit arrangement is fully operable; the number of operating hours remaining before preventative maintenance; the number of hours remaining before maintenance; an indication of suggested preventative maintenance; an indication of required preventative maintenance; an indication of a proposed maintenance; an indication of recommended maintenance; an indication of highly recommended maintenance; an indication that the recommended device is unavailable; an indication of an impending failure; an indication of a fault.

17. The method of claim 2, wherein the health status is affected by previous health status information.

18. The method of claim 3, wherein the health status is affected by previous health status information.

19. The method of claim 4, wherein the health status is affected by previous health status information.

20. A hydraulic circuit arrangement, wherein the hydraulic circuit arrangement operates at least occasionally according to the method of claim 1, and/or wherein the hydraulic circuit arrangement comprises a control unit, wherein the health status is indicated to an operator of the hydraulic circuit arrangement, stored in a memory device for human readout, and/or transmitted to an external device.

Technical Field

The invention relates to a method for determining the state of health of a hydraulic circuit arrangement. Furthermore, the invention relates to a control unit for a hydraulic circuit arrangement and to a hydraulic circuit arrangement which employs a method for determining its state of health.

Background

Technical devices, in particular technical devices comprising mechanically moving parts, only show a certain lifetime, after which they become unreliable and/or less efficient. Eventually, the device will be damaged or at least deteriorated to a level where it is practically no longer usable.

Often, the problem of accidental failure of equipment is significant. Not only does the productivity of the respective device drop significantly, often to zero, at a possibly problematic point in time, but the device must often also be recovered and/or repaired in problematic situations.

For this reason, a well-established solution is regular maintenance, in particular regular preventive maintenance. Herein, a component is replaced before a certain level of probability that it will fail is exceeded. In this way, the probability that the entire device will accidentally fail during use will be reduced to a correspondingly lower level. The probability level of unexpected failure is mainly selected according to the priority of the corresponding device.

This method is well known. For example, automobiles require regular maintenance. Typically, maintenance intervals are scheduled according to a particular allowed kilometer reading and a particular allowed time span between maintenance actions (both not in succession). Thus, unexpected failures occur rarely on the road.

Although this simple method works well in practice, there are some disadvantages. The main problem is that this fixing arrangement does not take into account individual wear. By way of example, if a car is always pulling a heavy trailer, primarily for use in mountainous areas, the wear on its components is significantly higher than that of light duty cars, which are primarily used on well-conditioned rural highways with little traffic congestion, curves and intersections. At the same time, in the first described case, the probability of failure rises above the standard probability level, the part replacement is premature in the second example, and therefore results in unnecessary waste of time and money for unnecessary maintenance work.

Various approaches have been used in the art to address this problem.

One possible approach is to use data describing the actual performance of the device being used. If the actual required performance is above the expected average, the maintenance interval is shortened, and if the actual required performance is below the expected average, the maintenance interval is lengthened. Returning to the example of an automobile: if the average power required by the automobile engine is higher than the design reference value, the maintenance interval is shortened. This will be indicated to the driver by a suitable indication in the cockpit.

The problem with this method is that the wear of the respective component/components is not directly taken into account. Instead, the wear is roughly estimated based on a model of the respective component. Again using only the example, if the material of a certain component exhibits some undetected weaknesses, the actual (possibly significantly increased) wear of the respective component will not be known, but a failure may still occur.

To alleviate these problems it is also suggested to directly measure the actual wear of the part/parts in question. Thus, these components are only replaced when they really need to be replaced. A simple example for this is to measure the thickness of the brake pad. If a certain lower limit of brake pad thickness is reached or exceeded, the brake lining will be replaced.

Although this method gives good results in practice, it still presents the disadvantage that additional sensors are usually required. These sensors are always a cost factor and they do require a certain installation space. Also, when displaying erroneous data, the corresponding sensor may be a cause of a defect. Therefore, excessive use of the sensor also presents a problem.

There is therefore a need in the art to obtain data that describes the actual health of the system as accurately as possible, while using as little sensor data as possible (especially sensor data from sensors that have to be provided purely for this purpose). Of course, these two conflicting requirements always require a certain compromise. Thus, there is still much room for improvement.

Disclosure of Invention

The object of the present invention is therefore to propose a method for determining the state of health of a hydraulic circuit arrangement which is improved compared to the methods known from the prior art for determining the state of health of a hydraulic circuit arrangement. Another object of the present invention is to provide a control unit for operating a hydraulic circuit arrangement which is improved compared to control units for operating hydraulic circuit arrangements known from the prior art. It is yet another object of the present invention to provide a hydraulic circuit arrangement which is improved compared to hydraulic circuit arrangements known in the art.

The presently proposed method, control unit and hydraulic circuit arrangement solve these problems.

According to a first aspect of the invention, a method of determining the state of health of a hydraulic circuit arrangement, in particular a hydraulic circuit arrangement comprising at least one hydraulic fluid working machine, is proposed. The state of health is determined at least in part using a comparison of actual temperature information of the hydraulic circuit arrangement and expected temperature information of the hydraulic circuit arrangement. Surprisingly, by using such input data partially/mainly/(substantially) only, an extremely accurate state of health of the hydraulic circuit arrangement monitored by the proposed method can be determined. Another particular advantage of the presently proposed method is that the sensors required with this method are relatively cheap, accurate and reliable. In most cases, temperature sensors are already present in the hydraulic circuit arrangement for monitoring purposes. Thus, an additional sensor may not be required. Even if the sensors already present are not sufficient for the methods proposed so far (e.g. the accuracy of the measured values is not high enough), the replacement of the imprecise temperature sensor which in any case has to be used by a (slightly) more complex temperature sensor is easy and generally cheaper to implement. In some cases, additional information (in addition to temperature information) may prove reasonable. The additional information may come from control inputs, databases, or additional sensors, to name a few examples. Using this additional information, a more accurate health status can generally be obtained. It should be noted that even if additional sensors are used, generally less costly, less accurate sensors (especially for additional information) may be used and/or the number of additional sensors may be reduced (which also has a suitable cost advantage). In particular, in most cases, already existing mechanical hardware can be used in combination with the presently proposed method. Even if some modifications to the hardware currently in use must be made, these changes are usually only necessary at a minimal level (if at all). Nowadays, since the hydraulic circuit arrangement usually already has electronic control circuitry, the presently proposed method can also be carried out using presently available hardware. Sometimes it may be necessary to use a somewhat more powerful electronic controller (or similar device). In this case, suitably larger electronic devices may be used. However, such alternatives are generally easy to implement and relatively inexpensive to implement. Such a replacement can usually be achieved in a very cost-effective manner even in cases where additional/separate electronic circuitry (in particular an electronic controller) has to be used to employ the presently proposed method. For completeness only, it should be mentioned that the use of separate electronic circuitry/electronic controllers for the presently proposed approach may present certain advantages that may easily outweigh the burden of additional cost. In particular, a higher reliability of the method can generally be ensured by such an arrangement. Since the presently proposed method usually requires only minor modifications, if any, of the hardware devices, the presently proposed method can even be used as a direct alternative (drop-in-solution) and/or a simple solution to achieve possible upgrades of already used machines. How the actual temperature information and/or the expected temperature information is obtained is basically arbitrary. Of course, suitable selection and/or modification of the respective information is suggested, wherein the selection/modification may depend on the actual used hydraulic circuit arrangement and its environment of use. Furthermore, the information used and/or the manner in which the health status is determined may be appropriately selected/modified based on the required or desired accuracy of the health status. Furthermore, the method for determining the state of health may be used in many hydraulic circuit arrangements, as will be explained in more detail later.

Although essentially all types of reasonable expected temperature information may be used, it is preferred if the expected temperature information is determined at least in part from the following set of temperature information acquisition methods: using a fixed temperature; using a temperature based model of the hydraulic circuit arrangement; using a temperature based on measurements made on the hydraulic circuit arrangement; modifying the temperature based on the operating time; modifying the temperature based on the operating load; modifying the temperature based on the operating load history; modifying the temperature based on an environmental parameter; modifying the temperature based on the actual temperature information history; modifying the temperature based on the hydraulic fluid type; modifying the temperature based on the hydraulic fluid change; the temperature is modified based on the previous health status data. Using one or several of the previous proposals, a more accurate health status can be determined. In particular, various influences can be taken into account in this way. Only a few examples are given: if the hydraulic circuit requires a higher power level, the actual temperature will also typically vary with the required load. However, the actual temperature change will typically vary in a non-linear manner with actual wear of the hydraulic circuit device. Modifying the expected temperature information may be used to reflect the non-linearity. The same idea applies mutatis mutandis to other influences, e.g. environmental influences, viscosity of the hydraulic fluid, etc. In particular, by using any kind of historical data of the hydraulic circuit arrangement, it is possible to take into account the typical wear behaviour over time of the hydraulic circuit arrangement (and its respective components) when determining the state of health. As a typical example: when using entirely new parts comprising mechanically moving parts, they will initially usually exhibit a slightly higher friction and therefore generate more heat. The friction force and thus the temperature are usually initially reduced due to the run-in effect. Typical behavior is then that these parts will exhibit substantially uniform friction/heat generation over a long period of time. Usually, at the end of the life cycle of the respective component, its friction and therefore the heat generated will increase again, which indicates a deterioration of the health condition. When referring to "friction forces", the wording may also include or even (at least partly) replace different heating effects, such as increased fluid losses due to increased clearance of the respective components, etc. At least for some of the previously mentioned methods of determining expected temperature information, in particular modifications to the "initial" temperature information, at least one additional sensor may prove advantageous or even necessary.

In general, the quality of the health status information may be even further improved if the actual temperature information is determined at least in part from the following set of temperature information acquisition methods: measuring the hydraulic fluid temperature; measuring the development of the temperature over time; measuring the mechanical power introduced into the hydraulic circuit arrangement; measuring mechanical power extracted from the hydraulic circuit arrangement; measuring the heat dissipation condition of the hydraulic circuit device to the environment; the measurement results are replaced or modified by calculations. It is to be understood that one of the above-described temperature information acquisition methods may be employed, and two or more thereof may be employed. In particular, typical (major) side effects on the actual temperature measurement may be considered. In addition, the nonlinearity between the actual wear and temperature information of the hydraulic circuit device (component) described previously is adapted to the actual temperature information (i.e., is adapted not only to the expected temperature information) with modification. At least for some of the previously mentioned actual temperature information determination methods (especially the modification of the "initial" temperature information) at least one additional sensor may prove advantageous or even necessary.

Preferably, the determined health states may be grouped, which group may comprise at least one, two or more health state levels. In particular, the at least one, two or more health status levels may be selected from the following group of health status levels: an indication that the hydraulic circuit arrangement is fully operational; an indication of the number of hours remaining for which the hydraulic circuit arrangement is fully operable; the number of operating hours remaining before preventative maintenance; the number of hours remaining before maintenance; an indication of suggested preventative maintenance; an indication of required preventative maintenance; an indication of a proposed maintenance; an indication of recommended maintenance; an indication of highly recommended maintenance; an indication that the recommended device is unavailable; an indication of an impending failure; an indication of a fault. It should be appreciated that different health status levels or any other type of health status may be used instead of and/or in addition to the non-exhaustive list given above. However, the indicated state of health level is often characterized by advantageous information for the operator and/or the operating facilities of the hydraulic circuit arrangement in question. In particular, it should be noted that, at times, there may be an urgent need to use a hydraulic circuit arrangement, so that it may prove reasonable to continue using the arrangement, despite the (possibly even significant) increased likelihood of failure. In contrast, during times when the hydraulic circuit arrangement in question (if any) is in any case hardly used, early maintenance may be meaningful, in order to have at hand a hydraulic circuit arrangement that can be operated for a long time for future needs.

The first experiment shows that it is particularly advantageous if the health status is influenced by previous health status information. In this way, the state of health may be of a somewhat comprehensive nature. In particular, the non-linear effects of actual use and actual wear during the history of use of the hydraulic circuit arrangement may be taken into account.

It is also proposed that the health status can be modified from the outside, in particular on the basis of the examination results and/or the maintenance performed. As an example, if a component has been repaired or replaced, the health status should normally be reset at the workshop to a completely new status (similarly: refurbished status, repaired status, "maintenance performed" status, etc.) so that the actual temperature increase due to increased friction of the respective component during the run-in phase of the respective component will not trigger a false alarm regarding the health status. This applies mutatis mutandis to some kind of rework or some kind of maintenance or the like performed on one or several components.

Further, it is proposed to determine a health state at least in part using machine learning methods, processes, and systems. In this way, a steady improvement of the quality of the determined health state may be achieved. Furthermore, the quality of the determined state of health may be improved depending on the actual operating characteristics of the hydraulic circuit arrangement. It should be noted that depending on the consumer and/or site in which the hydraulic circuit arrangement is used, it is very common for existing hydraulic circuit arrangements to be used in different ways. The manufacturer of the hydraulic circuit arrangement can hardly predict these dependencies, if at all. However, such characteristics may be taken into account using the proposed embodiments, at least over a long term.

It is further suggested that the health status is indicated to an operator of the hydraulic circuit arrangement, stored in a memory device for human reading, and/or transmitted to an external device. In this way, the versatility of the method can be improved in various ways. The question as to whether to transmit the health status, where to transmit the health status may depend on the determined health status level. As an example: the number of hours remaining for which the device is fully operational may not be of much interest to the operator of the hydraulic circuit arrangement (to avoid information overload) so that the corresponding information is only stored for reading out/transmission to external equipment so that a reasonable maintenance schedule can be arranged (which may also take into account the availability of maintenance facilities, to give just an example). However, a warning indicating a fault or impending fault is displayed to the operator of the device in great correlation. For this, a red light may be a suitable solution. Since the operator is likely to be informed of this anyway, there may be no need at all to transmit corresponding information to the external device (although this is of course still possible).

Furthermore, it is often particularly advantageous if the state of health and/or the expected temperature information and/or the other actual temperature information is a vector value. In this way, it is possible that the quality of the proposed method, in particular the health state to be determined, is even higher. The vector health may give different health levels for at least two, a plurality, most or (substantially) all (different) components of the hydraulic circuit arrangement using the presently proposed method. Thus, the state of health may take into account different wear of the various components. This applies mutatis mutandis to the external temperature information and/or the actual temperature information.

According to a further aspect of the invention, a control unit for a hydraulic circuit arrangement is proposed, wherein the control unit is designed and arranged in such a way that the method according to the preceding description is performed at least occasionally. In this way, the control unit may exhibit the same (at least similar) features and advantages as previously described. It should be noted that the control unit may also be modified at least similarly in the sense as described previously, typically yielding the same (at least similar) results and advantages as previously described.

In particular, it is proposed that the control unit is an electronic control unit, a programmable control unit, an electronic controller, and/or a device comprising a digital processing device. Such units are generally very versatile for use with the previously described methods. Furthermore, such units are currently available and are generally relatively inexpensive.

According to yet another aspect of the invention, a hydraulic circuit arrangement is proposed, wherein the hydraulic circuit arrangement is at least occasionally operated according to the previously suggested method, and/or wherein the hydraulic circuit arrangement comprises a control unit according to the previously suggested method. Such a hydraulic circuit arrangement will generally exhibit the same (at least similar) features and advantages as previously described. Moreover, the hydraulic circuit arrangement may generally be modified at least similarly in the sense previously described, generally yielding results and advantages identical to (at least similar to) those previously described.

In particular, the hydraulic circuit arrangement proposed at present can be used for mobile devices, in particular non-road vehicles and/or construction floor vehicles. When used in this case, the hydraulic circuit arrangement may utilize the inherent features of the present method and/or control unit in a particularly advantageous manner, thereby producing generally superior results.

It should be understood that it would be possible that various features as disclosed in the present application may be combined with each other even if such a combination is not explicitly stated. Further, it is possible that some features of the embodiments may be combined with the claims even if a plurality or even (substantially) all features of the respective embodiments are not comprised in the respective claim(s). Further, features of the claim/claims may be combined even if an explicit back-reference is not indicated in the respective claim(s).

Drawings

Other advantages, features and objects of the present invention will become apparent from the following detailed description of the invention when taken in conjunction with the accompanying drawings, wherein:

FIG. 1: a possible embodiment of the hydraulic circuit arrangement of the closed-loop hydraulic arrangement in the schematic;

FIG. 2: a schematic diagram of the probability of failure of the hydraulic circuit arrangement in relation to the operating time;

FIG. 3: an initial measurement of the temperature rise of a normally operating hydraulic circuit arrangement relative to the hydraulic circuit arrangement including a leak; and

FIG. 4: a flow chart of an embodiment of a method for determining a state of health of a hydraulic circuit arrangement.

Detailed Description

In fig. 1, a typical embodiment of the hydraulic circuit arrangement 1 is shown as a schematic circuit system (circuit). That is, a closed loop hydraulic system 1 is shown in fig. 1. In general, the closed loop hydraulic system 1 basically comprises a main hydraulic pump 2 and a hydraulic motor 3 interconnected by a main hydraulic fluid line 4. Most of the hydraulic fluid flux is confined in these main hydraulic fluid lines 4. The remaining fluid lines 5, 6 are limited to a relatively low percentage of the overall fluid flux, as will be described later.

In the presently illustrated embodiment of the closed-loop hydraulic system 1, both the main hydraulic pump 2 and the main hydraulic motor 3 are variable (e.g., swash plate pump/motor, wobble plate pump/motor, etc.). However, this will be seen as an optional feature of the respective devices 2, 3.

Currently, the main hydraulic pump 2 is driven by a prime mover 7 (e.g., an internal combustion engine). The main hydraulic motor 3 is connected to a mechanical load, for example a drive shaft 8 (only schematically depicted) of a vehicle.

Since a certain degree of leakage of oil can never be completely avoided in the hydraulic system, a hydraulic fluid collection line 6 is present. In the shown schematic, the hydraulic fluid collection line 6 is connected only to the housing of the main hydraulic pump 2, the main hydraulic motor 3 and the perfusion pump 10. However, it may be connected to additional hydraulic consumer equipment (consumer), joints of fluid lines, etc.; especially wherever a certain degree of hydraulic fluid leakage is expected. The hydraulic fluid collection line 6 returns the thus collected leakage oil to the fluid reservoir 9.

To take into account fluid leakage losses, the priming pump 10 draws hydraulic fluid from the fluid reservoir 9 and feeds it back into the main hydraulic circuit 4 (now one of the main hydraulic fluid lines 4) through the hydraulic fluid make-up line 5 and a suitably arranged check valve 11. Such devices are well known in the art. For the sake of completeness only, it should be mentioned that the perfusion pump 10 may be driven by the prime mover 7 (in particular via a common shaft; not shown) or any other type of mechanical power source.

Furthermore, in the presently shown embodiment, a temperature sensor 12 is arranged in one of the main hydraulic fluid lines 4. The temperature data acquired by the temperature sensor 12 are fed to an electronic controller 13. It is contemplated that the electronic controller 13 is used for this purpose only. However, it is also possible that the necessary calculations will be made by the electronic controller 13 being shared to provide several functions.

The electronic controller 13 compares the actual temperature data from the temperature sensor 12 and compares it with a reference temperature value. Based on the difference, the health status is calculated and output/delivered to the alarm panel 14. In order to be able to calculate an accurate state of health, the determination of the state of health is not only influenced by the pure temperature difference between the actual temperature value and the reference temperature value, but some additional influencing factors are taken into account, such as previous temperature development, number of operating hours experienced, development of previous state of health, etc. This additional data may be stored in and retrieved from memory 15 (e.g., flash memory 15, which may store the data contained therein), even if memory 15 is temporarily disconnected from the power source.

Fig. 2 shows a typical development of the failure rate 16 of the hydraulic circuit arrangement 1 over time. The failure rate 16 is plotted along the ordinate 18 of the graph, while the number of operating hours that have elapsed is plotted along the abscissa 17.

The probability of a device failure can be basically divided into three time intervals I, II and III.

The first time interval I is a burn-in time interval. This aging effect may occur if new components are present in the hydraulic circuit. Typically, such new components exhibit higher friction and manufacturing tolerances that may not have been detected. Therefore, the failure rate 16 is typically relatively high.

Typically, the failure rate 16 will initially decrease towards the boundary value 20. The failure rate 16 then typically remains substantially constant during time interval II. The time interval II is generally referred to as the service life of the device. The length of this time interval II depends, of course, on the type of component(s) and the quality of their design and construction. During this time interval, the failure rate 16 remains relatively constant over an extended time span.

However, after a certain operating time, the failure rate 16 will increase again. This is the so-called wear phase III.

For the sake of completeness only, it should be mentioned that the lengths of the first time interval I and/or (in particular) the service life interval II are not necessarily the same, even for the same device. In particular, the heavy use of some machines will generally shorten the length of the first time interval I and/or (in particular) the service life interval II (and therefore the wear phase III will be reached earlier). Additionally or alternatively, the length of the first time interval I and/or the service life interval II may be (even significantly) shortened due to some early major failure (which may be from some undetected failure of some component) and/or from unforeseen abnormal conditions. It should be noted that the cause of an early failure of a component may also originate from a different component. As an example: if metal debris from the fluid reservoir is transported into the pump, the pump may quickly break down, although the problem is elsewhere. Contrary to the above, in case the machine is operated in a slightly relaxed manner, the first time interval I and/or the service life interval II may of course be longer.

The optimum maintenance time is usually at or shortly after the transition time 19 between the service life interval II and the wear interval III (so that the failure rate 16 is still sufficiently low, but slightly above the limit value 20 of the failure rate 16).

Fig. 3 shows a measurement data map 21 of the first experiment. The data shown and the threshold line 24 will be understood as possible embodiments that may differ, in particular in relation to other devices. The vertical intersection 22 of the measurement data plot 21 indicates a run-in fluid flow device (e.g., the closed loop hydraulic system 1, shown in fig. 1) with substantially no fluid leakage. By essentially no fluid leakage is meant that this reflects a typical fluid leakage that exists during the service life interval II (see fig. 2), and that this fluid leakage can never be completely avoided. Furthermore, several X-intersections 23 are shown in the measurement data map 21. The X-intersection 23 represents a measurement made of a fluid flow device with increased leakage flow. Such increased leakage flow is typical for components that are subject to some wear and therefore does show an increased clearance between these components and other (adjacent/neighbouring) components; this is a typical behavior of the fluid flow device during wear phase III (see fig. 2).

On the abscissa 17 ("x-axis") of the measured data diagram 21, the pressure differences across typical components of the hydraulic circuit arrangement (e.g. the pressure difference between the fluid inlet and the fluid outlet of the main hydraulic pump 2 and/or the main hydraulic motor 3; compare with fig. 1) are shown. On the ordinate 18 ("y-axis") of the measurement data map 21, the temperature difference between the actual measured temperature and the reference temperature is plotted.

As is clear from fig. 3, there is a rather clear distinction between the different sets of measured values. Thus, a threshold line 24 may be drawn. If the measured point is above the threshold line 24, a very high probability can be concluded: the respective component is already in its wear phase III and has to be replaced. As mentioned previously, such temperature increases may also result from unforeseeable abnormal conditions, early failure of some components, and the like. Conversely, if the measurement point is below the threshold line 24, the component is still in its service life phase II, at least with a higher probability.

The threshold line 24 may also look different. In particular, the threshold line 24 may be modified based on an adaptive algorithm using machine learning techniques.

Based on these observations and a first experiment, in fig. 4 a possible embodiment of a method 25 of determining the state of health of the hydraulic circuit arrangement 1 is shown as a flow chart.

After system start 26, temperature data from the sensor 12 is read into the controller 13 at 27. The actual temperature data thus received is modified 28 so as to take into account the load characteristics, environmental characteristics, heat dissipation effects, and the like of the hydraulic circuit device 1. Within the same modification step 28, the reference temperature may also be modified, for example by taking into account previously determined health status data.

Once the corrected actual temperature information and the corrected reference temperature information are obtained (calculated in step 28), an actual comparison is made and from this the state of health data is determined in a continuous state of health determination step 29.

After the determination 29 of the health status, a check 30 is performed whether the health status is still within the allowable limits. If the state of health 30 is above a certain threshold, a warning message 31 is generated and the algorithm 25 jumps back to the beginning. However, if the state of health is still below a certain threshold, the algorithm 25 simply jumps back and does not generate a warning message.

While the disclosure has been shown and described with respect to certain embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the disclosure.