Method, computing unit and computer program for determining relative humidity inside a vehicle

Abstract

The invention relates to a method (200) for determining the relative humidity in a cabin (110) of a vehicle (100), comprising acquiring (220, 230) an instantaneous dew point temperature for a geographical location (210) near the vehicle (100), determining (240) the actual interior air temperature inside the vehicle cabin (110), and determining (260) the relative humidity of the air inside the vehicle cabin (110) based on the dew point temperature and the actual interior temperature. A computing unit (130) and a computer program for carrying out such a method (200) are also proposed.

Description

[0001] This invention relates to a method for determining relative humidity inside a vehicle cabin, as well as a computing unit and a computer program for carrying out the method. Background of the invention

[0002] Excessive humidity can cause a number of problems in vehicles. For example, it can cause condensation on windows, obstructing the driver's view of the road and reducing driving safety. Additionally, prolonged periods of excessive humidity can promote the growth of mold and mildew inside the vehicle, particularly in upholstery, reducing the vehicle's usability and value, and endangering the health of its occupants. High relative humidity can also create a damp or stuffy feeling, further reducing passenger comfort.

[0003] Typically, the humidity inside a vehicle can be monitored, for example with dedicated humidity sensors, in order to take countermeasures in case of excessive humidity. Such countermeasures can include, for example, activating the air conditioning. Disclosure of the invention

[0004] The present invention proposes a method for determining relative humidity in a vehicle cabin, a computing unit, and a computer program with the features listed in the respective independent claims. Advantageous embodiments are the subject of the independent claims and the following description.

[0005] The invention utilizes the fact that meteorological data, such as dew point temperatures, are readily available for almost any location on Earth. This data is used to determine the local humidity (outside) and also the humidity inside a vehicle cabin. This eliminates the need for dedicated sensors and thus reduces the costs of vehicle manufacturing and / or maintenance. The determination of the relative humidity inside the vehicle cabin is based on the assumption that, at least at the beginning of the journey, the air inside the cabin has a composition that is essentially identical to the composition of the air surrounding the vehicle.

[0006] The procedure includes recording an instantaneous dew point temperature for a geographical location near the vehicle, determining an actual internal air temperature inside the vehicle cabin, and determining the relative humidity of the air inside the vehicle cabin based on the dew point temperature and the actual internal temperature.

[0007] In at least one embodiment, the method further comprises determining an actual outside temperature of the atmosphere surrounding the vehicle and determining the relative humidity of the atmosphere surrounding the vehicle based on the outside temperature and the dew point temperature.

[0008] In at least one embodiment, the method further comprises comparing the relative humidity of the air inside the vehicle cabin with a predetermined humidity threshold and taking action if the relative humidity reaches or exceeds the humidity threshold.

[0009] In particular, the threshold may depend on the indoor temperature.

[0010] In at least one embodiment, the method further comprises determining the geographical location of the vehicle using a satellite navigation device of the vehicle, wherein acquiring the instantaneous dew point temperature for the geographical location of the vehicle includes requesting the dew point temperature for the determined location from a database and receiving the dew point temperature from the database.

[0011] In particular, the database can be stored inside the vehicle and / or remotely from the vehicle.

[0012] In at least one embodiment, determining the relative humidity based on the dew point temperature comprises determining a vapor pressure based on the dew point temperature and a saturation vapor pressure based on the actual indoor temperature and / or—where determined—the outdoor temperature, and determining the relative humidity as the quotient of the determined vapor pressure and the determined saturation vapor pressure. The relative humidity can be expressed as a percentage or as a fraction of 1.

[0013] A computing unit according to the invention, e.g., a vehicle control unit, is configured to execute a method according to the invention. In particular, such a configuration can be implemented by appropriately programming the computing unit.

[0014] Implementing a method according to the invention in the form of a computer program or a computer program product with a program code form that executes all method steps is also advantageous, as it incurs particularly low costs. This is especially true in cases where a control unit executing the program code is also used for other tasks and is therefore already available. Finally, a machine-readable storage medium is proposed, wherein a computer program, as specified herein, is stored. Suitable storage media or data carriers for providing the computer program include, in particular, magnetic, optical, and electrical storage devices, such as hard disks, flash memory, EEPROMs, DVDs, and others. Downloading a program via computer networks (e.g., the Internet, intranet, etc.) is also possible. Such a download can be wireless (e.g., via Wi-Fi).via a WLAN network, a 3G, 4G, 5G or 6G connection, etc.) or wired or cable.

[0015] Further advantages and embodiments of the invention can be derived from the description and the accompanying drawing.

[0016] The invention is schematically illustrated in the drawing with reference to an exemplary embodiment and is described below with reference to the drawing. Brief description of the drawing Fig. Figure 1 schematically shows a vehicle that can be used in one embodiment of the invention. Fig. Figure 2 illustrates an exemplary embodiment of the invention in a schematic block diagram. embodiment(s) of the invention

[0017] In Fig. Figure 1 schematically depicts a vehicle usable in an embodiment of the invention and is collectively designated by reference numeral 100. The vehicle 100 comprises a cabin 110 configured to accommodate at least one person, e.g., a driver and / or a passenger of the vehicle 100. The cabin 110 can be partially or completely sealed off from the vehicle's environment, particularly with regard to fluid exchange, so that no air can flow freely between the cabin 110 and the surrounding atmosphere.

[0018] The vehicle 100 further includes two temperature sensors 120, 140, one of which is an external temperature sensor 140 configured to measure an external temperature, i.e., the temperature of the atmosphere surrounding the vehicle 100. The second of the two temperature sensors is an internal temperature sensor 120 configured to measure an internal temperature, i.e., the temperature of the air inside the cabin 110.

[0019] In the example shown, both temperature sensors 120 and 140 are connected to a computing unit 130, e.g., a control unit, of the vehicle 100 via data transmission. This data connection can be wired and / or wireless.

[0020] The computer 130 is configured to receive and interpret temperature data from the two temperature sensors 120 and 140, and is further configured to record at least data concerning a dew point temperature for a geographical location near the vehicle 100. For this purpose, the computing unit 130 can, for example, include an antenna for wireless communication with a data network 101.

[0021] In Fig. Figure 2 is an exemplary embodiment of the invention, schematically illustrated as a simplified block diagram and designated in its entirety by reference numeral 200. In particular, the block diagram can be interpreted as a flowchart of an embodiment 200 of a method according to the invention.

[0022] All pressures in this embodiment are given in hPa and all temperatures are given in °C unless otherwise stated.

[0023] In the embodiment shown, the method 200 starts with a step 210 in which a geographical location of the vehicle, for example the one in Fig. The location of vehicle 100 shown in Figure 1 is determined. In particular, a satellite navigation system of vehicle 100 can be used to determine the geographical location, but other means can also be used for this purpose.

[0024] Once the geographical location has been determined, the procedure 200 requests, in step 220, for example from a meteorological service provider, e.g. via the data network 101, an instantaneous dew point temperature for the determined location.

[0025] In step 230, the requested dew point temperature is recorded, for example, received via an antenna. Another option for requesting (step 220) and recording (step 230) this data is to store a database within the vehicle 100 itself (this could, for example, be downloaded from a meteorological service provider, as mentioned, for a specific area at the start of a journey, and then accessed during the vehicle 100's operation). It is also conceivable and advantageous to use information broadcast locally, for example, by radio stations, so that step 210 can be implemented intrinsically by receiving the locally broadcast signal. This ensures that only a locally valid dew point temperature is received in each case, rendering the determination of the vehicle 100's geographical location unnecessary.

[0026] In steps 240 and 250, an indoor temperature (step 240) and an outdoor temperature (step 250) are determined. This can be achieved by reading sensor signals from the respective temperature sensors 120 and 140 of the vehicle 100. However, various methods can also be used to determine the respective indoor and outdoor temperatures in the context of procedure 200. For example, meteorological services can also provide relatively accurate actual local temperature values, which can be used to determine at least the actual outdoor temperature (step 250).

[0027] Regardless of the specific way in which the temperature values ​​for the air inside the vehicle cabin 110 and / or the atmosphere surrounding the vehicle 100 are determined, in step 260 a relative humidity of the respective environment (i.e. the air in the cabin 110 and / or the atmosphere surrounding the vehicle 100) is determined based on the dew point temperature recorded (from step 230) and the respective actual temperature (step 240 and / or 250, respectively).

[0028] For example, based on the dew point temperature (abbreviated to T) DP ) an actual vapor pressure (abbreviated to p) v ) of water vapor in the atmosphere can be calculated based on the following formula: pV / mbar=TDP243.5°C+TDP

[0029] In the context of the Magnus-Tetens approximation for calculating the saturation vapor pressure over liquid water, the value 243.5 °C is an empirical constant. This formula approximates the more complex Clausius-Clapeyron equation, and the constants (such as 243.5 °C) have been determined by a regression analysis of observed data to provide a good fit over a range of typical atmospheric temperatures.

[0030] Additionally, the instantaneous saturation vapor pressure (p vs ) calculated based on the respective actual temperature (T) according to the empirical Magnus-Tetens formula: pVS / mbar=6.112⋅e(17.67×T243.5°C+T)

[0031] The relative humidity (RH) can then be obtained by calculating the quotient of the determined vapor pressure and the saturation vapor pressure: RH=(pVPVS)⋅100%

[0032] The relative humidity thus determined is then compared in step 270 with a predetermined humidity threshold. The threshold used in step 270 can be chosen depending on the actual relevant temperature. For example, at low temperatures (e.g., below 18 °C or 15 °C), a relative humidity of, say, more than 40% can already cause a clammy feeling, while at medium temperatures, e.g., between 18 °C and 24 °C, a higher relative humidity may still be tolerable, so that in such a case the threshold can be chosen, for example, to be in the range of 50% to 70%. At high temperatures, such as above 25 °C, high relative humidity can cause a stuffy feeling, so the threshold in such a temperature range can be chosen lower, for example, again below 50% or the like.Such temperature-dependent humidity thresholds can be stored in the vehicle, for example in control unit 130, in the form of a lookup table. In particular, such temperature-dependent humidity thresholds depend solely on the interior temperature and not on the exterior temperature.

[0033] If the determined relative humidity exceeds the predetermined threshold, procedure 200 proceeds to step 280 as described below. Conversely, if the determined relative humidity does not exceed the predetermined threshold, procedure 200 may return to a previous step, for example, step 210.

[0034] In step 280, a measure is taken to reduce the relative humidity inside cabin 110. For example, during step 280, the vehicle's air conditioning system 100 can be controlled to regulate the relative humidity inside cabin 110. This can involve cooling the air inside the cabin and collecting condensation from the cooled cabin air before reheating it, so that the temperature inside cabin 110 can remain essentially constant while reducing the relative humidity.

[0035] Other options for measures to reduce relative humidity inside the cabin (110) may include using a defrost setting on the vehicle's heating system. The defrost setting helps remove moisture from the inside of the vehicle's windshield by directing a stream of warm air to areas particularly prone to fogging due to their specific thermal environment. Using a dehumidifier, i.e., a device that removes excess moisture from the air, can also help reduce humidity inside the vehicle (100) and thereby prevent the windshield from fogging up.

[0036] Such removal of water vapor from the cabin air obviously changes the dew point temperature of the air inside the cabin, so that any measure taken during step 280 can be taken into account during the subsequent steps 260, determining the relative humidity inside the cabin 110 at a later time during the journey or even during a later journey of the vehicle 100.

[0037] Similarly, in some embodiments, step 260 can take into account water vapor added to the air inside cabin 110 by any occupants of the vehicle 100 (detected, for example, using seat occupancy sensors, an occupant monitoring camera, or the like). For example, a mathematical model can be used to assess the influence of occupants and / or measures taken during step 280 and / or any intentional or accidental (partial) exchange of cabin air with the atmosphere surrounding the vehicle 100. Any such calculations used to correct the specified relative humidity can, for example, be performed by the control unit 130.

[0038] After initiating action 280, procedure 200 can return to a previous step, for example to steps 240 or 250, to continue monitoring relative humidity during later time intervals.

Claims

[1] Method (200) for determining a relative humidity in a cabin (110) of a vehicle (100), comprising the acquisition (220, 230) of an instantaneous dew point temperature for a geographical location (210) near the vehicle (100), determining (240) an actual internal temperature of the air inside the vehicle cabin (110) and Determining (260) the relative humidity of the air inside the vehicle cabin (110) based on the dew point temperature and the actual interior temperature. [2] Method (200) according to claim 1, further comprising determining (250) an actual outside temperature of the atmosphere surrounding the vehicle (100) and determining (260) the relative humidity of the atmosphere surrounding the vehicle based on the outside temperature and the dew point temperature. [3] Method (200) according to claim 1 or 2, comprising comparing (270) the relative humidity of the air inside the vehicle cabin with a predetermined humidity threshold and taking action (280) if the relative humidity exceeds the humidity threshold. [4] Method (200) according to claim 3, wherein the threshold depends on the internal temperature. [5] Method (200) according to any of the preceding claims, comprising determining (210) the geographical location of the vehicle (100) using a satellite navigation system of the vehicle, wherein acquiring the instantaneous dew point temperature for the geographical location of the vehicle (100) comprises requesting (220) the dew point temperature for the determined location from a database and receiving (230) the dew point temperature from the database. [6] Method (200) according to claim 5, wherein the database is stored inside the vehicle (100) and / or remotely from the vehicle (101). [7] Method (200) according to any of the preceding claims, wherein determining (260) the relative humidity based on the dew point temperature comprises determining a vapor pressure based on the dew point temperature and a saturation vapor pressure based on the actual indoor temperature and / or, in a case according to claim 2, the actual outdoor temperature, and determining the relative humidity as the quotient of the determined vapor pressure and the determined saturation vapor pressure multiplied by 100%. [8] Computing unit (130) configured to perform a method (200) according to any of the preceding claims. [9] Computer program configured to instruct a computing unit (130) to execute a method (200) according to any of the preceding claims when executed by the computing unit (130). [10] Machine-readable storage medium with a computer program stored therein according to claim 9.

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