Automated starting of a motor vehicle

Abstract

Method for at least partially automated starting of a motor vehicle (1) with a passenger compartment (2), wherein - a first air pressure value is measured at a position of a key unit (3); - a second air pressure value is measured in an interior of the passenger compartment (2); - the motor vehicle (1) is started at least partially automatically depending on a difference between the first air pressure value and the second air pressure value; - an air pressure in the interior of the passenger compartment (2) is changed compared to an outside air pressure; - the second air pressure value is measured as the value of the changed air pressure; and - an interior volume of the passenger compartment (2) and / or a quantity of a gas in the interior of the passenger compartment (2) are changed in order to change the air pressure in the interior of the passenger compartment (2).

Description

[0001] The invention relates to a method for at least partially automated starting of a motor vehicle with a passenger compartment and an associated control system for a motor vehicle.

[0002] For keyless start systems in motor vehicles, i.e. those in which the vehicle can be started, for example, by pressing a button or starter without any explicit operation using a key, it may be necessary, for example, to ensure functional safety that the engine of the motor vehicle cannot be started if the corresponding key is outside the motor vehicle.

[0003] Depending on the design of the keyless start system, however, problems can arise. Systems that use remote keys, for example, are susceptible to relay attacks, where the distance between the vehicle and the remote key can be bridged by transceiver units in such a way that the vehicle can be opened and started even when the key is actually outside the intended range. Since no operation of the key itself is required to start the vehicle, the signal path for starting the vehicle can be extended via a relay attack, even if the key is put down or in a pocket. This means that in the event of a successful relay attack, the engine can be started even when the key is outside the vehicle.

[0004] Other systems, which are based, for example, on signal propagation time measurements or signal strength measurements and corresponding trilateration or triangulation, require a large number of measuring transducers installed on the vehicle and are nevertheless limited in the accuracy of the position determination, so that a reliable distinction between the position of the key device inside or outside the passenger compartment of the vehicle cannot be guaranteed.

[0005] Publication DE 10 2013 209 612 A1 describes a method for automatically opening a motor vehicle. A plausibility check can be performed to determine whether similar conditions are met for the vehicle and the key. These conditions can be linked, among other things, to data regarding air pressure or other environmental conditions. However, even with this method, a distinction between the interior and exterior of the motor vehicle is neither possible nor necessary, since only access to the vehicle is verified, not the vehicle's engine.

[0006] Document DE 10 2013 209 612 A1 describes a method for automatically opening a vehicle. A first air pressure datum can be determined in the vehicle and a second air pressure datum in the vicinity of an electronic key. A plausibility check can be performed to determine whether the same conditions are met for the vehicle and the key. Depending on the plausibility check, the vehicle's starting option can be enabled or denied.

[0007] DE 10 2017 205 162 A1 describes a method for detecting relay attacks. An ID transmitter can determine the air pressure in its surroundings and compare this with measurement data from a vehicle sensor. This makes it possible to determine whether the ID transmitter is in the vehicle and, if not, to prevent the engine from starting. In one embodiment, an acoustic signal is generated by the ID transmitter, and a check is carried out to determine whether a microphone in the vehicle can detect the acoustic signal.

[0008] Against this background, it is an object of the present invention to provide an improved concept for the at least partially automated starting of a motor vehicle with a passenger cell, which increases the functional safety during automated starting.

[0009] This problem is solved according to the improved concept by the respective subject matter of the independent claims. Advantageous developments and further embodiments are the subject matter of the dependent claims.

[0010] The improved concept is based on the idea of increasing functional safety by determining, based on at least two air pressure measurements in a key unit and inside the passenger compartment, whether the key unit is located inside the passenger compartment with sufficient probability.

[0011] According to the improved concept, a method is provided for the at least partially automated starting of a motor vehicle with a passenger compartment. According to the method, a first air pressure value is measured at a position of a key unit. A second air pressure value is measured in an interior of the passenger compartment, and the motor vehicle is started at least partially automatically, in particular by means of a computing unit, for example a computing unit of a control system, depending on a difference between the first air pressure value and the second air pressure value.

[0012] The first air pressure value is measured in particular by a first air pressure sensor of the key unit and the second air pressure value is measured by a second air pressure sensor of the motor vehicle, in particular of the control system, which is arranged in particular inside, i.e. in the interior, of the passenger compartment.

[0013] In this case, an interior volume of the passenger compartment and / or a quantity of a gas in the interior of the passenger compartment are changed in order to change the air pressure in the interior of the passenger compartment compared to an outside air pressure, and the second air pressure value is measured as the value of the changed air pressure or an air pressure in the interior of the passenger compartment is modulated over time, a temporal modulation of the second air pressure value is measured by means of the second air pressure sensor and the motor vehicle is started at least partially automatically depending on a temporal course of the difference.

[0014] The passenger compartment is spatially completely separated from the outside area around the vehicle.

[0015] Starting the motor vehicle includes in particular starting a drive motor of the motor vehicle.

[0016] For example, starting a motor vehicle, particularly in the case of electric vehicles, may initially involve merely making the vehicle ready to drive and / or switching on the ignition without actually starting the engine. The engine may then only start upon a second user action, such as applying the brake, engaging a gear, and so on, or upon starting off.

[0017] The fact that the starting is at least partially automatic can mean, in particular, that user interaction with the motor vehicle is required to start the motor vehicle. The user interaction can, for example, involve touching a button or pressing a start button on the motor vehicle.

[0018] The key unit is, in particular, a key unit for authenticating or authenticating an authorization to start the motor vehicle. The key unit is thus designed, for example, as a portable device, in particular a portable electronic device, whose owner is assumed to be a legitimate user of the motor vehicle.

[0019] The key unit can contain a motor vehicle key in the narrower sense, i.e., a key for operating a motor vehicle's ignition lock and / or unlocking a motor vehicle door. However, the key unit can also contain another portable electronic device, such as a mobile phone or a radio unit, that can communicate wirelessly with the motor vehicle to perform an authentication process as a prerequisite for starting the motor vehicle.

[0020] By linking the automated start to the air pressure difference, it is possible to determine or verify whether the key unit is located inside the passenger compartment. If this is the case, it can be assumed that the difference between the first air pressure value and the second air pressure value is smaller than a specified tolerance or threshold value. If the key unit is located outside the vehicle, i.e., outside the passenger compartment, the difference tends to be larger, which leads to a corresponding differentiation.

[0021] Absolute accuracy in the range of a few hectopascals can be achieved using common pressure sensors, for example, pressure sensors based on microelectromechanical systems (MEMS). Therefore, even small air pressure differences between the interior and exterior of the passenger compartment can be reliably detected.

[0022] By automatically starting the vehicle based on the difference, the risk of relay attacks is prevented, resulting in greater security. Since the key unit is usually not in the immediate vicinity of the vehicle in the event of a relay attack, it is likely that the difference in air pressure values is significantly greater than the corresponding measurement inaccuracies.

[0023] In addition, the improved concept requires only two pressure sensors, making the process a cost-effective and less complex solution.

[0024] According to at least one embodiment of the method, the first air pressure value is transmitted wirelessly from the key unit to the motor vehicle, in particular the control system, for example the computing unit.

[0025] According to at least one embodiment, the motor vehicle is started automatically depending on the difference only when a predetermined user interaction is detected, in particular by means of the computing unit.

[0026] The predefined user interaction includes in particular the actuation of an input component of the motor vehicle for starting the motor vehicle, for example a start button, a start switch or the like.

[0027] According to at least one embodiment, the computing unit compares the first air pressure value with the second air pressure value to determine the difference.

[0028] According to at least one embodiment, the computing unit generates a difference signal representing the difference depending on the result of the comparison. The motor vehicle is started automatically or partially automatically, for example, by the control system, depending on the difference signal.

[0029] According to at least one embodiment, the motor vehicle is only started at least partially automatically if the difference is less than or equal to a predetermined maximum difference.

[0030] According to at least one embodiment, it is determined, in particular by means of the computing unit, depending on the difference whether the key unit is located inside the passenger compartment.

[0031] According to at least one embodiment, the motor vehicle is only started at least partially automatically if it is determined, in particular by means of the computing unit, depending on the difference that the key unit is located in the interior of the passenger compartment.

[0032] For example, it can be assumed that the key unit is located inside the passenger compartment if the difference is less than or equal to the specified maximum difference.

[0033] According to at least one embodiment, the motor vehicle is then started at least partially automatically if it is determined, in particular by means of the computing unit, that the difference is less than or equal to the predefined maximum difference.

[0034] In the embodiments in which the air pressure in the interior of the passenger compartment is changed relative to the external air pressure of the passenger compartment or the motor vehicle, in particular by means of a pressure-changing device of the control system, and the second air pressure is measured as the value of the changed air pressure, in particular by means of the second pressure sensor, the air pressure inside the passenger compartment, which corresponds to the second air pressure value, is in other words specifically changed by appropriately modifying, for example, a quantity of substance or a volume content inside the passenger compartment. This increases the difference between the first and second air pressure values, for example, if the key unit is not located inside the passenger compartment.This means that, for example, a larger tolerance or a larger measurement error can be accepted when measuring air pressure values and / or a higher reliability of the method or the distinction between indoor and outdoor space can be ensured.

[0035] For example, the change in the air pressure in the interior of the passenger compartment compared to the outside air pressure can be verified by measuring the outside air pressure as a third air pressure value, for example by means of a third pressure sensor arranged outside the passenger compartment.

[0036] Another way to verify is to detect an air flow from the outside of the passenger compartment into the passenger compartment or vice versa.

[0037] The change in air pressure in the passenger compartment can affect the entire passenger compartment or a portion of the interior. This portion can be spatially separated from the rest of the interior. This can simplify the change in air pressure, since the smaller the total volume of the portion in which the air pressure is to be changed, the smaller the modification of the volume or amount of air in that portion.

[0038] In the embodiments in which the air pressure in the interior of the passenger compartment is modulated over time, in particular by means of the pressure-changing device, and the temporal modulation of the second air pressure value, in particular in response to the temporal modulation of the air pressure in the interior of the passenger compartment, is measured by means of the second air pressure sensor, and the motor vehicle is started partially automatically depending on a temporal profile of the difference between the second air pressure value and the first air pressure value, the modulation of the air pressure in the interior of the passenger compartment can, for example, involve changing the air pressure once or repeatedly over a specific period of time. The modulation can also involve periodically changing the air pressure.Modulating may also include generating a predefined temporal pattern of successive pressure increase phases, pressure decrease phases and / or constant phases during which the pressure remains constant.

[0039] The modulation of the air pressure inside the passenger compartment is reflected in the measured second air pressure value or its modulation. If the key unit is located inside the passenger compartment, this modulation is also recognizable in an identical or similar manner in a corresponding modulation of the first air pressure value.

[0040] The modulation of the air pressure can be changed differently and / or randomly by the vehicle, especially during each start-up process, in order to prevent recording and reproduction for a relay attack.

[0041] By measuring or monitoring the temporal progression of the difference between the two air pressure values, the position of the key unit inside or outside the passenger compartment can be determined with greater reliability. This results in greater security.

[0042] According to at least one embodiment, the motor vehicle is only started at least partially automatically if it is determined, in particular by means of the computing unit, that the difference during the predetermined modulation period is always less than or equal to the maximum difference.

[0043] In this case, it can be assumed that the modulation of the first and second air pressure values match and that the key unit is located in the interior of the passenger compartment.

[0044] According to at least one embodiment, one or more windows and / or a ventilation opening, for example for forced ventilation, of the motor vehicle are closed, in particular closed automatically, for example controlled by the computing unit, while the air pressure inside the passenger compartment is modulated, for example during the modulation period.

[0045] This allows the modulation of the air pressure in the interior to take place in a shorter time or at a higher frequency, so that less time is required to reliably compare the first and second air pressure values.

[0046] According to at least one embodiment, a partial area, in particular a partial area for storing the key unit, of the interior of the passenger compartment is spatially separated from the remaining interior of the passenger compartment, for example automatically or manually, for example controlled by means of the computing unit, and the air pressure in the interior of the partial area is modulated over time in order to modulate the air pressure in the interior of the passenger compartment over time, as described above.

[0047] For example, it can be verified by a position sensor of a separating device for separating the partial area that the partial area is separated from the rest of the interior.

[0048] By separating the partial area and modulating the air pressure only inside the partial area, less influence on the corresponding air volume or the corresponding amount of air is required than would be necessary to modulate the air pressure in the interior of the entire passenger compartment.

[0049] This allows for a higher degree of inaccuracy in measuring air pressure values and requires less effort to modulate the air pressure.

[0050] The partial area of the interior may, for example, correspond to a storage compartment which can be closed, for example, by a flap, a sliding door, a cover or the like to separate it from the rest of the interior.

[0051] The sub-area can, for example, be a storage location intended for wireless charging of a mobile device, for example with an inductive charging device for a smartphone.

[0052] According to at least one embodiment, an interior volume content of the passenger compartment, or optionally of the partial area of the passenger compartment, is modulated over time in order to modulate the air pressure in the interior of the passenger compartment or of the partial area.

[0053] According to the ideal gas equation, the product of pressure and volume is directly proportional to the product of the amount of substance and temperature of an ideal gas. Assuming an air pressure of the order of 1000 hPa and a total interior volume of the passenger compartment of 1 m 3 , a change in interior volume of about 1 / 1000 m 3 (1 I) leads to a change in air pressure of about 1 hPa. Such a pressure difference can be detected by sensitive pressure sensors.

[0054] In designs where the partial area of the interior is separated, the pressure change can be increased accordingly. For example, assuming a partial area of 1 / 1000 m 3 interior volume content, a volume change of 1 / 10000 m 3 (0.1 l) a pressure change of the order of 100 hPa, which can be easily detected even by less sensitive pressure sensors.

[0055] The change in the interior volume can be achieved, for example, by an air pressure changing device with a lifting cylinder with a corresponding stroke in the interior of the passenger compartment or in the interior of the partial area.

[0056] According to at least one embodiment, a quantity of a gas, in particular air, in the interior of the passenger compartment, or in the interior of the partial area, is modulated over time in order to modulate the air pressure in the interior of the passenger compartment.

[0057] The amount of gas can be adjusted, for example, by operating a fan or an air conditioning system of the motor vehicle or the air pressure changing device.

[0058] According to at least one embodiment, the first air pressure sensor for measuring the first air pressure value, in particular of the key unit, and the second air pressure sensor for measuring the second air pressure value, in particular of the motor vehicle or the control system, are calibrated against each other when the motor vehicle is started at least partially automatically depending on the difference.

[0059] In particular, calibration is performed after it has been determined that the difference is less than or equal to the maximum difference and the corresponding vehicle has been started.

[0060] Calibration can further increase the accuracy of the adjustment and thus the reliability of the process.

[0061] For calibration purposes, it is assumed, for example, that if the vehicle is started successfully, the two air pressures at the positions of the two air pressure sensors are identical by definition.

[0062] For example, calibration may be performed after the motor vehicle has been automatically started and then stopped again and it has been determined that all doors of the motor vehicle or other openings of the motor vehicle have been closed, in particular after all users of the motor vehicle have left the passenger compartment.

[0063] According to the improved concept, a control system for a motor vehicle with a passenger compartment is also specified. The control system has a second air pressure sensor that is configured and arranged to measure a second air pressure value in an interior of the passenger compartment, and the control system has a computing unit that is configured to receive a first measured air pressure value from a key unit for the motor vehicle and, depending on a difference between the first air pressure value and the second air pressure value, to generate an output signal in order to start the motor vehicle at least partially automatically. The control system has a pressure-changing device that is configured to change an interior volume of the passenger compartment and / or a quantity of a gas in the interior of the passenger compartment in order to change an air pressure in the interior of the passenger compartment relative to an external air pressure.The air pressure sensor is designed to measure the second air pressure value as the value of the changed air pressure.

[0064] The computing unit receives the first air pressure value, for example by means of a communication interface, in particular wirelessly, for example by radio.

[0065] According to at least one embodiment, the control system includes the key unit and in particular a first air pressure sensor for measuring the first air pressure value.

[0066] According to the improved concept, a further control system for a motor vehicle with a passenger compartment is specified. The control system has a second air pressure sensor that is configured and arranged to measure a second air pressure value in an interior of the passenger compartment, and the control system has a computing unit that is configured to receive a first measured air pressure value from a key unit for the motor vehicle and, depending on a difference between the first air pressure value and the second air pressure value, to generate an output signal in order to start the motor vehicle at least partially automatically. The control system has a pressure changing device that is configured to temporally modulate an air pressure in the interior of the passenger compartment.The air pressure sensor is configured to measure a temporal modulation of the second air pressure value and the computing unit is configured to start the motor vehicle at least partially automatically depending on a temporal progression of the difference.

[0067] Further embodiments of the control system according to the improved concept follow directly from the various embodiments of the method according to the improved concept, and vice versa. In particular, a control system according to the improved concept is configured to carry out a method according to the improved concept, or the control system carries out such a method.

[0068] According to the improved concept, a motor vehicle with a control system according to the improved concept is also specified.

[0069] According to the improved concept, a computer program with instructions is also specified. When the instructions are executed by a control system according to the improved concept, in particular by the control system's computing unit, the instructions cause the control system to perform a method according to the improved concept.

[0070] According to the improved concept, a computer-readable storage medium is specified on which a computer program according to the improved concept is stored.

[0071] The invention also includes further developments of the control system according to the invention that have features already described in connection with the further developments of the method according to the invention. For this reason, the corresponding further developments of the control system according to the invention are not described again here.

[0072] The invention also includes combinations of the features of the described embodiments.

[0073] An embodiment of the invention is described below. The figures show: Fig. 1 is a schematic representation of a motor vehicle with an exemplary embodiment of a control system according to the improved concept; and Fig. 2 a schematic representation of a motor vehicle with a further exemplary embodiment of a control system according to the improved concept.

[0074] The exemplary embodiments explained below are preferred embodiments of the invention. In the exemplary embodiments, the described components of the embodiments each represent individual, independently considered features of the invention, which also further develop the invention independently of one another and are thus also to be considered as components of the invention, either individually or in a combination other than that shown. Furthermore, the described embodiments can also be supplemented by further features of the invention already described.

[0075] In the figures, functionally identical elements are provided with the same reference numerals.

[0076] In Fig. 1 shows a motor vehicle 1 which includes a control system 9 according to the improved concept.

[0077] The control system 9 comprises a computing unit 8 and a second air pressure sensor 4b coupled to the computing unit 8, which is arranged in particular in the interior of a passenger compartment 2 of the motor vehicle 1. Furthermore, the control system 9 comprises a communication interface 6 for wireless communication with a key unit 3 or a communication interface 7 of the key unit 3.

[0078] The communication interfaces 6, 7 can be designed, for example, as radio receivers and / or transmitters.

[0079] Key unit 3 is in Fig. 1 arranged outside the passenger compartment 2.

[0080] The key unit 3 can be designed as a radio key for the motor vehicle 1 or as another electronic portable device, for example as a mobile phone.

[0081] The key unit 3 also has a first air pressure sensor 4a.

[0082] In Fig. 2 is the motor vehicle 1 of the Fig. 1 is shown again, with the key unit 3 being located in the interior of the passenger compartment 2.

[0083] During operation of the control system 9, the first air pressure sensor 4a measures a first air pressure value at the position of the key unit 3 and the second air pressure sensor 4b measures a second air pressure value in the interior of the passenger compartment 2.

[0084] The first air pressure value is transmitted to the computing unit 8 via the communication interface 7 of the key unit 3, in particular via the communication interface 6. The computing unit 8 compares the first air pressure value with the second air pressure value and determines a difference based on the comparison. Only if the difference is less than or equal to a predetermined maximum difference can the motor vehicle 1 be started automatically or partially automatically. This can be done, for example, by a user of the motor vehicle 1 pressing a start button or the like to start it.

[0085] By linking the automatic or partially automatic starting to the condition that the difference is less than or equal to the maximum difference, a sufficient probability is ensured that the key unit 3 is located in the interior of the passenger compartment 2 during the partially automatic starting of the motor vehicle 1.

[0086] Optionally, the control system 9 includes an air pressure modulating device (not shown). This device may, for example, include a lifting cylinder or a diaphragm and / or a fan. Furthermore, the air pressure modulating device includes a corresponding controller for controlling the lifting cylinder or the fan.

[0087] The lifting cylinder or membrane is arranged such that it can change the air volume in the interior of the passenger compartment 2. The fan is configured to change the mass of air in the interior of the passenger compartment 2.

[0088] The computing unit 8 is particularly configured to control the air pressure variation device so that it specifically manipulates the air pressure in the interior of the passenger compartment 2. The manipulation can involve a simple increase or decrease in the air pressure in the interior of the passenger compartment 2 relative to the surroundings, i.e., an exterior area of the motor vehicle 1.

[0089] Alternatively or additionally, it is possible to define a sequence or a defined temporal pattern of specific, consecutive pressure increase phases, pressure decrease phases, or constant phases using the air pressure variation device. The corresponding changes are then measured both by the second air pressure sensor 4b and, if the key unit 3 is located in the interior or in the corresponding area of the interior of the passenger compartment 2, by the first air pressure sensor 4a. If the temporal profiles of the corresponding air pressure values match sufficiently precisely, it can be assumed that the key unit 3 is located in the interior of the passenger compartment 2.

[0090] If all doors, windows, etc. are closed, the sealing of the interior of the passenger compartment 2 during the change in air pressure is sufficient to change the air pressure accordingly.

[0091] In order to additionally seal the passenger compartment, for example, a forced ventilation of the motor vehicle 1 can be closed during this period or controlled according to the change in air pressure in order, for example, to enable a faster pressure change.

[0092] For example, automatic starting may be prevented if it is detected that one or more windows or doors of motor vehicle 1 are open.

[0093] Alternatively or additionally, the computing unit 8 can control the corresponding window and close it automatically in order to then carry out the method as described.

[0094] Optionally, the motor vehicle 1 or the control system 9 can have a storage compartment 5 for storing the key unit 3, as shown in Fig.2. In such embodiments, the storage compartment 5 can be closed manually or automatically, for example, in order to define a partial area separated from the remaining interior of the passenger compartment 2. The second air pressure sensor 4b is then arranged such that it can determine the second air pressure value as the air pressure value in the interior of the partial area or of the storage compartment 5. The temporal change in the air pressure then occurs by changing the air quantity and / or the volume inside the storage compartment 5.

[0095] This means that a much smaller volume or amount of air has to be changed, which leads to pressure changes that are easier to measure.

[0096] The storage compartment 5 may, for example, contain a charging cradle for a mobile phone, in particular if the mobile phone represents the key unit 3.

[0097] Alternatively, a glove compartment of the motor vehicle 1 adapted as described could also serve as a storage compartment 5.

[0098] According to the improved concept, as described, a reliable method is provided for determining whether the key unit is located inside the passenger compartment. By coupling such a determination with the partially automatic starting of the motor vehicle, increased security is achieved.

[0099] For example, the air pressure sensors can be calibrated against each other after each authenticated engine start to enable the most accurate reading possible during the next measurement and subsequent comparison. In appropriate embodiments, calibration can be combined with air pressure manipulation. Calibration can be performed, for example, after the last door and window are closed after the vehicle has been parked. Any air pressure manipulation performed before the next engine start can then be measured more accurately.

[0100] The change in air pressure in the corresponding embodiments also has the advantage that air pressure as an environmental variable can be easily and quickly influenced. List of reference symbols 1 motor vehicle 2 passenger compartment 3 key unit 4a Air pressure sensor 4b Air pressure sensor 5 storage compartment 6 Communication interface 7 Communication interface 8 computing unit 9 Control system

Claims

[1] Method for at least partially automated starting of a motor vehicle (1) with a passenger compartment (2), wherein - a first air pressure value is measured at a position of a key unit (3); - a second air pressure value is measured in an interior of the passenger compartment (2); - the motor vehicle (1) is started at least partially automatically depending on a difference between the first air pressure value and the second air pressure value; - an air pressure in the interior of the passenger compartment (2) is changed compared to an outside air pressure; - the second air pressure value is measured as the value of the changed air pressure; and - an interior volume of the passenger compartment (2) and / or a quantity of a gas in the interior of the passenger compartment (2) are changed in order to change the air pressure in the interior of the passenger compartment (2). [2] Method for at least partially automated starting of a motor vehicle (1) with a passenger compartment (2), wherein - a first air pressure value is measured at a position of a key unit (3); - a second air pressure value is measured in an interior of the passenger compartment (2) by means of an air pressure sensor (4b) of the motor vehicle (1); - the motor vehicle (1) is started at least partially automatically depending on a difference between the first air pressure value and the second air pressure value; - an air pressure in the interior of the passenger compartment (2) is modulated over time; - a temporal modulation of the second air pressure value is measured by means of the air pressure sensor (4b); and - the motor vehicle (1) is started at least partially automatically depending on a temporal progression of the difference. [3] Method according to claim 2, characterized by , that - a partial area (5) of the interior of the passenger compartment (2) is spatially separated from the remaining interior of the passenger compartment (2); and - the air pressure inside the sub-area (5) is modulated over time. [4] Method according to one of claims 2 or 3, characterized by that an interior volume of the passenger compartment (2) is modulated over time in order to modulate the air pressure in the interior of the passenger compartment (2). [5] Method according to one of claims 2 to 4, characterized by that a quantity of a gas in the interior of the passenger compartment (2) is modulated over time in order to modulate the air pressure in the interior of the passenger compartment (2). [6] Method according to one of the preceding claims, characterized by that the motor vehicle (1) is only started at least partially automatically if, depending on the difference, it is determined that the key unit (3) is located in the interior of the passenger compartment (2). [7] Method according to one of the preceding claims, characterized by that the motor vehicle (1) is only started at least partially automatically if it is determined that the difference is less than or equal to a predefined maximum difference. [8] Method according to one of the preceding claims, characterized by that an air pressure sensor (4a) for measuring the first air pressure value and the air pressure sensor (4b) of the motor vehicle (1) for measuring the second air pressure value are calibrated against each other when the motor vehicle (1) is started at least partially automatically depending on the difference. [9] Control system for a motor vehicle (1) with a passenger compartment (2), wherein - the control system (9) comprises an air pressure sensor (4b) which is designed and arranged to measure a second air pressure value in an interior of the passenger compartment (2); - the control system (9) has a computing unit (8) which is designed to - to receive a first measured air pressure value from a key unit (3); and - to generate an output signal depending on a difference between the first air pressure value and the second air pressure value in order to start the motor vehicle (1) at least partially automatically; - the control system (9) comprises a pressure-changing device which is designed to change an interior volume of the passenger compartment (2) and / or a quantity of a gas in the interior of the passenger compartment (2) in order to change an air pressure in the interior of the passenger compartment (2) compared to an outside air pressure; and - the air pressure sensor (4b) is arranged to measure the second air pressure value as the value of the changed air pressure. [10] Control system for a motor vehicle (1) with a passenger compartment (2), wherein - the control system (9) comprises an air pressure sensor (4b) which is designed and arranged to measure a second air pressure value in an interior of the passenger compartment (2); - the control system (9) has a computing unit (8) which is designed to - to receive a first measured air pressure value from a key unit (3); and - to generate an output signal depending on a difference between the first air pressure value and the second air pressure value in order to start the motor vehicle (1) at least partially automatically; - the control system (9) comprises a pressure variation device which is designed to temporally modulate an air pressure in the interior of the passenger compartment (2); - the air pressure sensor (4b) is designed to measure a temporal modulation of the second air pressure value; and - the computing unit (8) is designed to start the motor vehicle (1) at least partially automatically depending on a temporal progression of the difference.

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