Method for detecting moisture in a control unit

Abstract

The present invention relates to a method for detecting moisture in a control unit, wherein, in response to a change (102) in a power input (100) in an interior of the control unit, a resulting temperature change (104) of the interior is evaluated in order to detect moisture in the interior.

Description

Field of the invention

[0001] The invention relates to a method for detecting moisture in a control unit of a vehicle, a corresponding control unit, and a corresponding computer program product. State of the art

[0002] A control unit may be installed in an area of ​​a vehicle that is exposed to environmental influences, such as splash water. Therefore, the housings of such control units are designed to be sealed.

[0003] The control unit may have a humidity sensor to detect moisture in the control unit. If moisture is detected, this indicates that the housing is leaking, for example, because a seal on an opening is not sealing properly, the housing is damaged, condensation has formed, or because a pressure compensation element in the control unit is no longer fluid-tight.

[0004] The humidity sensor can, for example, comprise a material that changes an electrical property depending on its humidity. The material can, for example, be hygroscopic, so that it can detect not only direct wetting of the humidity sensor but also increased humidity in the interior of the control unit. Disclosure of the invention

[0005] Against this background, the approach presented here presents a method for detecting moisture in a control unit, a corresponding control unit, and a corresponding computer program product according to the independent claims. Advantageous further developments and improvements of the approach presented here emerge from the description and are described in the dependent claims. Advantages of the invention

[0006] A humidity sensor is a component of a control unit that is installed solely in case of a fault that hopefully never occurs and otherwise has no functionality for the operation of the control unit. The humidity sensor incurs additional costs because it is purchased or manufactured, installed, electrically connected, and evaluated via a separate electrical circuit.

[0007] The approach presented here does not require a separate humidity sensor. Here, humidity is detected indirectly, through a change in the specific heat capacity of the interior of the control unit due to the moisture ingress. This requires only temperature measurement in the control unit and evaluation of the resulting temperature signal.

[0008] The temperature in the control unit is usually recorded as standard to detect thermal overload of the control unit. If an overload is detected, the system can react by reducing the comfort functions of the control unit while fully maintaining the safety functions of the control unit.

[0009] The approach presented here eliminates the need for a separate humidity sensor and typically allows for dual use of existing control unit hardware. By detecting ingress of moisture based on the change in heat capacity, even moisture that would never reach a humidity sensor and therefore cannot be detected by the sensor can be detected.

[0010] A method for detecting moisture in a control unit is presented, wherein in response to a change, in particular a sudden change, in a power input in an interior of the control unit, a resulting temperature change of the interior is evaluated in order to detect moisture in the interior.

[0011] Ideas for embodiments of the present invention can be considered, among other things, to be based on the thoughts and findings described below.

[0012] A control unit can be a control unit of a vehicle. The control unit can be, for example, a brake control unit of the vehicle. The control unit can have a housing sealed against the ingress of liquid. An interior of the control unit is enclosed by the housing. Electronics and other components of the control unit are at least partially arranged in the interior. The housing has openings for data lines, control lines and / or supply lines. At least one of the openings is closed by a cover of the housing. Media lines can also be routed into the interior through openings. A pressure compensation element of the housing can be arranged in one opening. The openings are sealed to prevent the ingress of moisture.The pressure equalization element is also sealed against moisture, but allows air to flow into and out of the interior when there is a negative pressure or positive pressure in the interior compared to the ambient pressure.

[0013] All penetrations are potential defects through which moisture could enter the interior in the event of a defect. To detect moisture, the approach presented here observes the temperature profile of the interior as the control unit heats up or cools down, and a change in the temperature profile compared to an expected temperature profile is used to infer the presence of moisture in the interior. This takes advantage of the fact that the electronics usually already include a temperature sensor and an electrical circuit for evaluating the temperature sensor. Therefore, only data processing capacity in the control unit or a central control unit is required to evaluate the temperature profile.

[0014] Heating is observed in situations in which additional energy in the form of heat is introduced into the control unit by switching on at least one component of the control unit. Cooling is observed in situations in which less energy in the form of heat is introduced into the control unit by switching off at least one component of the control unit. Switching components of the control unit on or off therefore influences a momentary power input into the control unit. The aforementioned switching on or off of a component can be accompanied by a sudden, i.e. abrupt, change in the power, energy or heat input into the interior of the control unit.

[0015] Additional heat input warms up the interior. Less heat input cools down the interior. If moisture is present in the interior, the moisture will heat up or cool down in addition to the air normally present in the interior and the components of the control unit. The moisture has additional heat capacity and increases the overall heat capacity of the interior and its components. With the same power input, the additional heat capacity of the moisture will cause the interior to heat up or cool down more slowly than without the moisture. The delayed heating or cooling can therefore be used to determine the presence of moisture.

[0016] The temperature change can be evaluated based on a known change in power input. The power input can be changed by activating or deactivating functions of the control unit. The change in power input associated with the respective function may be known, for example, because the function has a defined power requirement. An expected temperature change can be linked to a known power input or a known change in power input. If the temperature change deviates from the expected temperature change, in particular, occurs more slowly, the presence of moisture in the control unit can be inferred.

[0017] An expected temperature change can be determined during control unit design and testing. The expected temperature change can be learned through several changes in power input. When the control unit is new, it can generally be assumed that the control unit is sealed and therefore no moisture is present in the interior. Therefore, an expected temperature curve can be learned during a change in power input for later moisture testing. After a predetermined learning period or a predetermined number of heating and / or cooling processes, the expected temperature curve can be saved, and the learning process can be terminated.

[0018] The evaluation and / or learning process can be interrupted if a further unknown change in the power input is detected. An unknown change in the power input can occur, for example, in modulated processes. For example, it may be necessary to dynamically adjust the power supply for actuators controlled by the control unit depending on the situation. In this case, the power input may be unknown and the temperature change undefined. Measurements during and / or shortly after the unknown power input can be discarded.

[0019] The temperature change can be compared to a temperature difference expected within a predefined period following the change in power input to detect humidity. If the total heat capacity of the control unit is increased by humidity, the temperature will increase or decrease less than without humidity in the same period, assuming a known power input. Humidity in the control unit can therefore be detected if the temperature change within that period is smaller than the expected temperature difference.

[0020] The time required for a predefined temperature change after a change in power input can be compared with the expected time for the temperature change to detect humidity. If the total heat capacity of the control unit is increased by humidity, it will take longer for the temperature to increase or decrease by a certain temperature difference, assuming a known power input.

[0021] Moisture in the control unit can therefore be detected if the time required to heat up or cool down the control unit is longer than the expected time by the temperature difference.

[0022] The temperature change can be evaluated after the control unit has been booted up and / or shut down. After the control unit is switched on, for example, when starting the vehicle, standardized processes can be executed in the control unit that change the power input in a known manner. For example, the components can be tested or the electronics self-tests can be performed each time the system is booted up. If the control unit warms up more slowly and / or takes longer than expected after booting up, moisture can be detected.

[0023] During shutdown, for example, when parking the vehicle, the control unit may have been supplied with a known electrical power prior to shutdown. During shutdown, the power input may end because no electrical current flows. The control unit can then cool down freely and is not cooled by wind or spray. If the control unit cools down more slowly and / or takes longer to cool down than expected, moisture can be detected.

[0024] The control unit can be at least partially restarted after a predefined waiting period after shutdown to measure the temperature change. This waiting period can be monitored by a timer that is started when the control unit is shut down. During this waiting period, the control unit can consume virtually no power. It is not necessary to activate the entire control unit to measure the temperature; a small portion of the electronics may be sufficient. To measure the temperature, the control unit can be briefly reactivated and then deactivated again. By measuring the temperature after the waiting period, particularly accurate humidity detection can be achieved.

[0025] Furthermore, at least one environmental parameter can be evaluated during the temperature change to detect the humidity. An environmental parameter can be, for example, an ambient temperature. The environmental parameter can also be an air humidity. The environmental parameter can cause an external power input or energy withdrawal and thus influence the heating and / or cooling rate of the control unit. The environmental parameter can influence energy transfer between the environment and the control unit.

[0026] The method is preferably computer-implemented and can be implemented, for example, in software or hardware or in a mixed form of software and hardware, for example in a driver assistance system.

[0027] The approach presented here further creates a control unit, wherein the control unit is designed to carry out, control or implement the steps of a variant of the method presented here in corresponding devices.

[0028] The control unit can be an electrical device with at least one computing unit for processing signals or data, at least one memory unit for storing signals or data, and at least one interface and / or a communication interface for reading in or outputting data embedded in a communication protocol. The computing unit can be, for example, a signal processor, a so-called system ASIC, or a microcontroller for processing sensor signals and outputting data signals depending on the sensor signals. The memory unit can be, for example, a flash memory, an EPROM, or a magnetic storage unit. The interface can be designed as a sensor interface for reading in the sensor signals from a sensor and / or as an actuator interface for outputting the data signals and / or control signals to an actuator.The communication interface can be configured to read or output data wirelessly and / or via a wired connection. The interfaces can also be software modules, which are present, for example, on a microcontroller alongside other software modules.

[0029] Also advantageous is a computer program product or computer program with program code that can be stored on a machine-readable carrier or storage medium such as a semiconductor memory, a hard disk memory or an optical memory and is used to carry out, implement and / or control the steps of the method according to one of the embodiments described above, in particular when the program product or program is executed on a computer, in a control unit or a device.

[0030] It should be noted that some of the possible features and advantages of the invention are described herein with reference to different embodiments. A person skilled in the art will recognize that the features of the control device and the method can be combined, adapted, or exchanged as appropriate to achieve further embodiments of the invention. Short description of the drawings

[0031] Embodiments of the invention are described below with reference to the accompanying drawings, wherein neither the drawings nor the description are to be construed as limiting the invention. Fig. 1 shows a temperature curve when switching on a control unit, which is evaluated using a method according to an embodiment; Fig. 2 shows a temperature profile when switching off a control unit, which is evaluated using a method according to an embodiment; Fig. 3 shows a representation of an evaluation of a temperature profile according to an embodiment after a defined time; and Fig. 4 shows a representation of an evaluation of a temperature curve according to an embodiment after a defined temperature change.

[0032] The figures are merely schematic and not to scale. Like reference numerals denote like or equivalent features. Embodiments of the invention

[0033] Fig. 1 shows temperature curves when a control unit is switched on, which are evaluated using a method according to an exemplary embodiment. The temperature curves are shown in a diagram with time t plotted on its abscissa and a temperature T in an interior of the control unit on its ordinate. A solid line represents a temperature curve of a dry control unit with only air in the housing. A dashed line represents a temperature curve of a control unit with additional moisture penetrated into the housing. Above the diagram, a curve of a power input 100 into the control unit is shown, correlated in time to the temperature curves. The temperature T is recorded by a temperature sensor of the control unit that is installed in the interior as standard.

[0034] At a constant power input 100, an equilibrium temperature is established in the control unit. At the equilibrium temperature, the heat loss from the control unit to the environment and the power input 100 are equivalent. In response to a change 102 in the power input 100, the temperature T changes and approaches a new equilibrium temperature at which the power input 100 and the heat loss are again equal. This temperature change 104 is detected by the temperature sensor and is depicted in the temperature curves shown as examples for the dry control unit and the wet control unit.

[0035] Switching on causes a sudden increase in the power input 100. Due to this increase, the power input 100 and the heat loss are no longer equivalent. In response to the increase in the power input 100, there is also a temperature increase above the previous equilibrium temperature. Due to the temperature increase, the heat loss of the control unit increases. The temperature increase slows down the closer the temperature T approaches a new equilibrium temperature at which the power input 100 and the heat loss are again equivalent.

[0036] The rate of temperature change 104, or the gradient of the temperature rise, depends significantly on the heat capacity of the control unit. With a higher heat capacity, more power is required to heat the control unit by the same temperature increase in the same time. Here, the power is the same for a dry and a moist control unit, which means that the rate of temperature change 104, or the gradient of the temperature rise, is lower for the control unit with moisture in the housing than for the control unit with a dry housing.

[0037] The temperature curves thus reflect changes 102 in power input 100 with a time delay. The dry control unit reaches the elevated equilibrium temperature faster than the control unit with moisture in the interior.

[0038] When the change 102 in the power input 100 is detected, a subsequent temperature change 104 of the interior is evaluated to detect the humidity. In particular, the temperature change 104 during an observation period 106 is considered. During the observation period, the gradient of the temperature curve is essentially constant. After the observation period, the temperature T slowly approaches the equilibrium temperature.

[0039] The power input 100 results, for example, from waste heat generated by control unit components during operation. When additional components are activated, the power input 100 changes due to the additional waste heat generated by these components. Likewise, a change 102 in the power input 100 occurs when components are deactivated. When components are deactivated, the power input 100 decreases.

[0040] Here, the temperature change 104 after the control unit is switched on is recorded and evaluated in order to detect the humidity. When the control unit is switched on, the same components are usually always activated within a short period of time. The components can also be tested according to a test routine during switch-on and heat up in a known manner. Due to this additional power input 100, the interior heats up in a known manner without humidity. If the interior heats up more slowly despite the same power input 100, the specific heat capacity in the interior has most likely increased. Since no components have been added to the control unit to increase the heat capacity, the increase in heat capacity must be due to another additional medium, the most likely additional medium being penetrated moisture.

[0041] The power input 100 can be detected, for example, by measuring an electrical current flow for operating the control unit. The current power input 100 or its change 102 can also be detected indirectly based on actions of the control unit.

[0042] Fig. Figure 2 shows a temperature curve when switching off a control unit, which is evaluated using a method according to an embodiment. The illustration essentially corresponds to the illustration in Fig. 1. In contrast, the change 102 in power input 100 is negative here. After switching off, the control unit begins to cool from a previously reached equilibrium temperature. Here, too, the temperature curve of the dry control unit is shown as a solid line. A temperature curve of the control unit with moisture in the interior is shown as a dashed line. The temperature T of the dry control unit drops faster after switching off than the temperature T of the control unit with moisture in the housing, because the moisture significantly increases the total heat capacity of the air and the components in the housing.

[0043] Fig. Figure 3 shows an illustration of an evaluation of temperature profiles according to an embodiment after a defined time Δt. The temperature profiles are as in Fig. 1 in a diagram with a normalized time Tau on its abscissa and a normalized temperature T on the ordinate. The temperature curves represent, as in Fig. 1 Thermal step responses of a control unit with and without moisture in the housing to a sudden increase in the power input into the housing.

[0044] Here, the temperature change 104 is recorded and evaluated after the time Δt has elapsed. The control unit without moisture in the housing has heated up significantly more within the time Δt than the control unit with moisture in the housing.

[0045] Fig. 4 shows a representation of an evaluation of a temperature profile 100 according to an embodiment after a defined temperature change 104. The temperature profiles are as in Fig. 1 in a diagram with a normalized time Tau on its abscissa and a normalized temperature T on the ordinate. The temperature curves represent, as in Fig. 1 Thermal step responses of a control unit with and without moisture in the housing to a sudden increase in the power input into the housing.

[0046] Here, a time period Δt is recorded and evaluated until the defined temperature change 104 occurs. The control unit without moisture in the housing requires a significantly shorter time period Δt to complete the temperature change 104 than the control unit with moisture in the housing.

[0047] In the following, possible embodiments of the invention are summarized again or presented with slightly different wording.

[0048] An estimation of the air humidity and a detection of an inadmissibly high water content in a control unit are presented.

[0049] It is well known that control units in the automotive environment are protected against water ingress. This particularly applies to all control units installed in the underbody or engine compartment. Examples include the engine control unit, the brake control unit, and the steering control unit.

[0050] There are, among other things, installation regulations for these control units that ensure that no “puddles” form when driving through water, spraying or cleaning the engine, which over time can penetrate into the control unit.

[0051] In addition, measures are taken on the plug to prevent water from entering. This means that they are not only plugged in, but also securely locked. For example, at least one rubber seal is activated. In the relatively unlikely event that water does penetrate the plug, barriers are also included to ensure that only specific areas of the plug are exposed to water, not the entire plug at once.

[0052] The housings of the control units are protected against the ingress of water by means of sealing lips / sealing beads and additional gluing / welding.

[0053] Since water ingress can never be completely ruled out despite the measures listed here, moisture sensors are sometimes built into control units, especially those required for driving safety (e.g., steering control units). This allows the driver to be warned early on of a potential failure of, for example, the steering assistance.

[0054] The approach presented here proposes to dispense with the use of a humidity sensor, which saves considerable costs.

[0055] The advantage here is that it can detect whether water has penetrated the control unit's housing without the need for additional sensors. This means that the built-in sensors can perform this task, and only additional analysis is required at the software level.

[0056] Brake control units (ESP, IBC, etc.) typically contain at least one temperature sensor. This is required to detect whether the control unit temperature, i.e., the heat input into the control unit, is within the permissible temperature range or whether it is exceeding this temperature range. If the temperature is too high, individual or multiple functions (comfort functions) are deactivated, for example, to ensure that the control unit does not heat up further due to the control of actuators (B6 or H-bridge for pump or plunger, MOSFETs for the valves).

[0057] In the approach presented here, the temperature sensor is evaluated in an additional way. This additional analysis allows the control unit to be examined for water ingress, providing the driver with an early warning and thus initiating repairs before a failure occurs. A failure particularly relates to safety-relevant functions, such as active pressure buildup and active pressure release within the scope of ABS, TCS, and ROM, which should continue to be enabled. Furthermore, unintentional pressure buildup and release should be reliably prevented. Steering assistance should also continue to be provided – if possible to the usual extent. Incorrect or unwanted steering interventions should be reliably prevented.

[0058] It is irrelevant whether the functions are required by the driver during normal driving or whether the vehicle is in piloted or even autonomous mode. It goes without saying that with increasing automation and thus the execution of functions by the system itself rather than by the driver, the demands on a reliably functioning control unit increase. Another example are "true-by-wire" systems, in which functionality depends entirely on functioning electronics and there is no mechanical fallback in the event of a fault.

[0059] When a vehicle is started, the control units (brakes, steering, transmission, engine, etc.) are first powered up. This means they are supplied with power and perform various tests designed to ensure the driver is warned early in the event of a potential malfunction. Some of the tests are also performed cyclically while the vehicle is in operation.

[0060] Typically, no highly dynamic driving maneuvers take place in the first few minutes after the vehicle is started. This means that neither the steering nor the brakes need to perform rapid or highly dynamic activations. The heating of the control unit is therefore primarily caused by the heating of active components such as microcontrollers, ASICs, or MOSFETs. Of course, other simple electronic components also contribute to the heating of the control unit through heat loss. This power consumption is known and should generally be kept as low as possible to save energy, but it cannot be prevented.

[0061] Since the control unit has a constant volume, it can be assumed that a defined energy input ΔE also leads to a defined temperature increase ΔT. That is, ΔT ~ΔE. However, this assumption only applies to hermetically sealed or enclosed control units.

[0062] Many control units are equipped with a pressure equalization element. This is designed to ensure that the pressure in the control unit correlates with the ambient pressure, preventing unnecessary stresses in the control unit. The pressure in the control unit increases due to the energy input, which heats the air, causing it to expand. However, since expansion is limited (rigid housing), this would be reflected as pressure. Membranes such as Goretex© (or similar) are used as pressure equalization elements. These are waterproof, but not vapor- and pressure-tight.

[0063] For a control unit (example) with internal dimensions of approximately 10 cm x 12 cm x 3.5 cm, the air volume is VECU=420 cm3

[0064] The specific heat capacity of air is (at 20°C and 100% relative humidity) cAir=1.03kJkg K

[0065] With the density of air at 20° ρAir=1.204kgm3

[0066] If the mass of the air is mAir=ρAir⋅VECU mAir=0.50568 g

[0067] To heat this amount of air by 20°C, for example, QAir=cAir⋅mAir⋅ΔT Q=1.03kJkg K⋅0.0051 kg⋅20K QAir=0.1 kJ[≅100 Ws] required. This means that this amount of energy approximately leads to a corresponding temperature increase in the control unit (at least the temperature increase of the air).

[0068] Assuming that "only" 1 ml of water has penetrated the housing, this water, as well as the rest of the control unit including the enclosed air, will be heated by the waste heat of the components. A temperature increase of 20°C is also required for this. Q=c⋅m⋅ΔT Q=4.19kJkg K⋅0.001 kg⋅20K Q=0.0838 kJ[≅84Ws] additional energy is necessary.

[0069] This means that with the same amount of energy (and this is almost constant for each control unit under the same operating conditions) either the temperature variation in the same period is significantly lower (with the above example approximately 11 K instead of 20 K) or the predefined temperature lift takes significantly longer (with the above example for an intact (water-free system) 60 seconds is assumed, then with the corresponding amount of water this results in approximately 110 seconds).

[0070] In reality, the temperature increase will differ from the above calculation, as the hardware was not taken into account. However, since this hardware is immutable, it can be considered absolute. This means that it will always heat up equally in both the intact and the "water-affected" system.

[0071] In other words, a method is presented which is characterized in that the temperature behavior of a brake control unit - or the temperature behavior of another, for example, safety-relevant control unit in the vehicle - is evaluated and, if the heating behavior changes, a leaky housing is concluded.

[0072] If the duration for a temperature increase of e.g. 20 K (e.g. factor 1.5) is significantly longer, an information error can be stored in the control unit.

[0073] If the temperature increase is significantly lower in the same period (temperature increase, for example, approx. 30%), an information error can be stored in the control unit.

[0074] The information error can be displayed to the driver.

[0075] The ambient temperature can be taken into account as a supporting variable.

[0076] The evaluation can be carried out at the start of the journey or shortly after the control unit is started up.

[0077] The evaluation can be carried out in “normal load operation” of the control unit.

[0078] Normal load is, for example, the load that occurs when, for example, no active brake control interventions are taking place. Normal load is, for example, the load that occurs when, for example, only moderate brake modulation occurs without panic braking and without significant load changes. Normal load is, for example, the load that occurs when, for example, only moderate steering interventions occur without sudden lane changes and without evasive maneuvers.

[0079] By specifically controlling one or more electronic components, a deterministic amount of heat can be generated. For example, a B6 bridge can be controlled in an operating state without the EC motor rotating.

[0080] The cooling behavior of the control unit temperature during run-on can be evaluated.

[0081] When there is water in the control unit, cooling occurs more slowly because the heat sinks more slowly due to the high heat capacity of the “additional” water.

[0082] All potential heat sources can be deactivated during the run-down period. A timer can briefly wake up the control unit after a predefined time, perform a temperature measurement, and perform an analysis.

[0083] The result of the humidity estimation can be provided in the following ignition cycle.

[0084] A temperature-dependent electronic component can be used as a temperature sensor. For example, a resistor with a positive or negative temperature coefficient can be used.

[0085] The evaluation can be based on a physical heat model, which determines an expected temperature change at the temperature sensor in the control unit from the heat input of electronic components in the control unit, the heating of the solid and gaseous substances within the control unit and the heat dissipation to the environment.

[0086] The evaluation can be based on machine learning with the aim of determining a temperature increase in different operating situations during the initial use of the control unit and an assumed moisture-free state.

[0087] A deviation between the determined temperature and the actually measured temperature above a specified threshold can be considered an indicator of moisture ingress in the control unit.

[0088] In Fig. Figure 1 shows an example of the time behavior of the temperature in a control unit when switched on.

[0089] The heating of an ECU occurs approximately according to the behavior of a PT1 element (first-order delay element). The jump is triggered by the ECU being switched on. Part of the electrical energy is not converted into computing power, but is dissipated into the environment as heat. The electrical resistance of various components and the self-heating of microcontrollers and ASICs (application-specific integrated circuits) play a significant role in this.

[0090] Of particular interest is the temporal behavior of the temperature during the "preferred observation period." This period begins at the time the control unit is switched on (or shortly thereafter). The preferred observation period ends at a value corresponding to a maximum of 1 tau (time constant).

[0091] Limiting the observation period to 0 to 1 tau has the advantage of assuming an approximately linear relationship between energy input and temperature variation. Furthermore, the temperature variation per unit time is largest here, simplifying the analysis.

[0092] It may be useful to further restrict the observation period (e.g. to the interval [0 ... 0.5]), since the linear relationship is even more pronounced here.

[0093] It may be useful to further restrict the observation period (e.g., to the interval [0.1 ... 0.5]), since possible delay or attenuation elements influence the PT1 behavior, especially in the initial phase. The delay can occur, for example, due to shielding properties of large components between the heat source and the temperature measuring element.

[0094] The time constant of the control unit can be determined once before the start of series production in order to provide this parameter to the evaluation software during flashing.

[0095] Alternatively, the control unit can be configured to observe the PT1 behavior, for example, during the first 10, 20, or 50 cycles, and determine the time constant. Once the time constant value has stabilized, it can be used for further monitoring (for water). It is helpful to define a minimum or maximum value within which the time constant should be. If a time constant is determined that lies outside the specified interval, it can be assumed that water already entered the control unit at the beginning (e.g., shortly after the vehicle was delivered to the customer).

[0096] In Fig. Figure 2 shows an example of the time behavior of the temperature in a control unit when switched off.

[0097] Analogous to the behavior in Fig. 1 also applies the time behavior in Fig. 2 after the control unit is switched off. When the power electronics are switched off, some of the heat sources are eliminated, and the control unit cools back down to ambient temperature.

[0098] It's also conceivable that the control unit could be shut down almost completely after the end of the trip, with only a "timer" running. This timer would activate the control unit once, for example, after 5 minutes, measure the temperature, and perform the analysis. This could further save energy, and the measurement results would be less distorted by remaining heat sources.

[0099] In Fig. Figure 3 shows a standardized temperature curve with an evaluation after a defined time. This shows the temporal behavior of the temperature in a control unit during power-up based on the above example calculation with given volumes and water quantities. For example, if the temperature rise is evaluated at time 0.6, an expected standardized temperature rise of approximately 0.45 results. If, however, additional moisture is present in the housing, a significantly lower temperature rise (here, approximately 0.28) is observed.

[0100] In Fig.Figure 4 shows the standardized temperature curve with an evaluation based on a defined temperature rise. The temporal behavior of the temperature in a control unit during power-up is shown based on the above example calculation with given volumes and water quantities. For example, if the time for a temperature rise of 0.4 is evaluated, the expected time is approximately 0.5 tau. However, if additional moisture is present in the housing, the same temperature rise takes significantly longer (here, approximately 0.9).

[0101] The approach presented here allows moisture ingress to be detected without a specific humidity sensor in the control unit. The approach presented here can be used for all typical control units in passenger cars (brake control units, steering control units, engine control units, transmission control units, airbag control units, control units for determining acceleration and rotational movements (e.g., IIS). Future systems, such as control units directly on the brake caliper (e.g., EMB), can also be monitored using this method.

[0102] Finally, it should be noted that terms such as "comprising," "having," etc., do not exclude other elements or steps, and terms such as "a" or "an" do not exclude a plurality. Reference signs in the claims are not to be considered limiting.

Claims

[1] Method for detecting moisture in a control unit, wherein, in response to a change (102) in a power input (100) in an interior of the control unit, a resulting temperature change (104) of the interior is evaluated in order to detect moisture in the interior. [2] Method according to claim 1, wherein the temperature change (104) is evaluated after a known change (102) of the power input (100). [3] Method according to claim 2, wherein the evaluation is interrupted if a further unknown change (102) of the power input (100) is detected. [4] Method according to one of the preceding claims, in which the temperature change (104) is compared with a temperature difference expected in a predefined period (Δt) after the change (102) of the power input (100) in order to detect the humidity. [5] Method according to one of the preceding claims, in which a time period required for a predefined temperature change (104) after the change (102) of the power input (100) is compared with a time period expected for the temperature change (104) in order to detect the humidity. [6] Method according to one of the preceding claims, in which the temperature change (104) is evaluated after starting up and / or shutting down the control unit. [7] Method according to claim 6, wherein the control unit is at least partially restarted after a predefined waiting time after shutdown in order to measure the temperature change (104). [8] Method according to one of the preceding claims, further comprising evaluating at least one environmental parameter during the temperature change (104) in order to detect the humidity. [9] Method according to one of the preceding claims, in which an expected temperature change (104) is learned via several changes (102) of the power input (100). [10] Control device, wherein the control device is designed to carry out, implement and / or control the method according to one of the preceding claims in corresponding devices. [11] Computer program product which is designed to instruct a processor, when the computer program product is executed, to carry out, implement and / or control the method according to one of claims 1 to 9. [12] A machine-readable storage medium on which the computer program product according to claim 11 is stored.

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