Method and device for detecting occupancy of a vehicle seat

Abstract

Method for detecting occupancy of a vehicle seat (2) in a vehicle (4), wherein at least one elastic part (10) of the vehicle seat (2) is used as part of an oscillating system, wherein the presence of an occupancy is checked based on the oscillation behavior of the oscillating system, characterized in that a monitoring sensor (12B) attached outside the vehicle seat (2) is used to detect the oscillation behavior of the oscillating system and the monitoring sensor (12B) is a camera or a radar sensor.

Description

[0001] The invention relates to a method and a device for detecting whether a vehicle seat is occupied.

[0002] Various technical solutions exist for detecting whether a vehicle seat is occupied. These include, for example, integrating sensors into the vehicle seat or using external monitoring sensors, such as radar sensors.

[0003] From EP 3 461 685 A1 a vehicle seat with an electromechanical massage function can be found, in which the occupancy of the seat is determined on the basis of a recorded torque of an electric motor.

[0004] Such solutions are sometimes complex and costly.

[0005] From DE 10 2018 120 743 A1 a sensor system for determining the weight of vehicle occupants can be found, in which the weight determination is carried out on the basis of dynamic vibrations of the vehicle seat.

[0006] Similarly, a device for seat occupancy detection by evaluating a vibration can be found in DE 197 41 451 A1, wherein an actuator is used to excite the vibration.

[0007] Similar systems in which vibration is evaluated for weight determination and / or seat occupancy detection can be found, for example, in DE 10 2004 046 190 A1, DE 10 2005 030 078 A1, DE 10 2009 014 354 A1 or DE 10 2018 205 091 A1.

[0008] Based on this, the invention aims to provide a method and a device for detecting the occupancy of a vehicle seat, which is easy to implement.

[0009] The problem is solved according to the invention by a method with the features of claim 1 and by a device for detecting whether a vehicle seat is occupied in a vehicle with the features of claim 9. The vehicle seat has at least one elastic section, which is part of an oscillating mechanical system, wherein the presence of an occupant is verified based on the oscillation behavior of the oscillating system. This oscillation behavior is hereinafter also referred to simply as seat oscillation.

[0010] In addition to the elastic section, the device also includes at least one sensor for detecting vibrations of the oscillating system and an evaluation unit that is designed and configured to determine the vibration behavior of the oscillating system and to check, based on the determined vibration behavior, whether a seat is occupied.

[0011] This principle of detecting seat occupancy based on the vibration behavior of the oscillating system is based on the consideration that the vehicle seat, or at least parts of it, together with any additional mass when occupied, constitutes an elastic, oscillating mechanical system. Due to the elasticity of the elastic section, this system exhibits its own characteristic vibration behavior when subjected to vibration, which depends in particular on the mass of the oscillating system. The mass, in turn, is significantly influenced by whether the seat is occupied or not.Depending on the mass, a defined vibration behavior of the oscillating system is established, so that the mass and thus the seat occupancy can be determined based on the vibration behavior, in particular based on at least one characteristic value or on several characteristic values ​​of the vibration behavior, such as frequency, frequency spectrum, phase or amplitude.

[0012] In particular, the evaluation of the vibration behavior involves recording and determining the mass and thus the weight. This also helps to differentiate whether it is merely a (light) object or a person.

[0013] In a preferred embodiment, a resonance frequency of the oscillating system, and thus of the seat vibration, is detected, and this detected resonance frequency is used to check whether the seat is occupied. Accordingly, in a preferred further development, the device, and specifically the evaluation unit, is configured to determine the vibration behavior of the oscillating system and, based on this determined vibration behavior, to check whether the seat is occupied. The resonance frequency therefore constitutes the previously described (characteristic) parameter for the vibration behavior.

[0014] This design is based on the premise that the oscillating system has a defined spring constant. The mechanical oscillating system accordingly exhibits a resonant frequency, which depends solely on its mass. In addition to the spring constant, the intrinsic mass of the elastic section is also known. When the vehicle seat is occupied, for example by a person or an object, the mass of the oscillating mechanical system changes and thus influences the resonant frequency. By measuring the resonant frequency, the mass of the oscillating mechanical system can therefore be directly determined, and consequently, it can be directly inferred whether there is additional mass on the elastic section of the vehicle seat. By evaluating and determining the resonant frequency of the oscillating system, it is thus possible to ascertain whether the vehicle seat is occupied or not.

[0015] The spring constant is known due to the design of the vehicle seat, or is determined in advance, for example through investigations and measurements, and is therefore known.

[0016] The evaluation of whether the seat is occupied and / or the mass of the person occupying it is performed, in particular, when the spring constant is known. This evaluation is carried out, for example, by calculation taking into account the instantaneous, weight-dependent resonance frequency and the known spring constant. According to a simplified evaluation, this is done, for example, solely based on the determined resonance frequency and a stored assignment to an occupancy and / or a corresponding weight, particularly using a lookup table.

[0017] This generally applies when checking seat occupancy based on vibration behavior, i.e., the evaluation of vibration behavior and checking of seat occupancy is carried out, for example, by calculation or by comparison with a stored assignment.

[0018] A vehicle seat typically consists of a seat cushion and a backrest. The backrest is usually adjustable relative to the seat cushion. Both the seat cushion and the backrest each typically have a support, such as a frame or shell, to which padding, specifically a seat cushion and / or a cover fabric, is attached. The padding is typically made of foam.

[0019] The elastic section refers in particular to the seat part or at least a part thereof, such as padding or a seat cushion of the seat part.

[0020] In a preferred embodiment, the oscillating system is excited to oscillate during vehicle operation due to the vehicle's movements. In particular, it is a purely passive oscillating system that does not have a motorized vibration exciter integrated into the vehicle seat, which is designed to generate a mass-dependent vibration behavior of the oscillating system that varies depending on the seat occupancy. By omitting a vibration exciter, the entire system for detecting vehicle seat occupancy is simple in design.

[0021] In particular, a weight sensor, which directly measures weight and therefore occupancy, has been omitted.

[0022] This approach utilizes the fact that vibrations occur during driving, for example due to uneven road surfaces, which excite the oscillating system. The vibration behavior is essentially a response to this (external) vibration excitation, hereinafter also referred to as excitation vibration. This vibration excitation during driving fundamentally leads to vibration behavior of the vehicle itself, and in particular to vibration behavior of the body or a body component. Thus, the vibration behavior of the vehicle excites the elastic, oscillating system, and therefore especially the vehicle seat. This external vibration excitation of the oscillating system is therefore also referred to as vehicle-side excitation (vibration excitation).

[0023] This vibration excitation is typically very broadband. Due to this broadband vibration spectrum of the (external) vibration excitation, the oscillating system is also regularly excited at its mass-dependent and therefore variable natural frequency, and thus at its mass-dependent, instantaneous resonance frequency, so that the entire system oscillates at this resonance frequency. At the very least, the vibration at the resonance frequency is dominant due to the resonance and can therefore be easily determined. Overall, by utilizing the already existing broadband vibration spectrum, excitation of the oscillating system at the resonance frequency is easily ensured, which is the basis for the preferred design involving the determination of the resonance frequency.

[0024] Although the system is also excited to other vibrations by the broadband spectrum of the vibration excitation, these are negligible compared to the resonant vibration. At least the resonant vibration, and thus the resonant frequency, can be reliably determined in a simple way as the vibration with the largest amplitude.

[0025] To determine the resonance frequency and the vibration behavior in general, at least one suitable sensor is typically used to capture motion data from the elastic subrange. This motion data usually consists of the velocity or acceleration of a reference point specifically within the elastic subrange and / or a change in distance between two reference points specifically within the elastic subrange.

[0026] In a preferred embodiment, several sensors are used, which are either identical and / or based on different detection principles. In any case, this provides redundancy for determining the vibration behavior. The sensors described below can therefore also be used in any combination.

[0027] Preferably, only one type of sensor is used to detect the vibration.

[0028] According to the invention, the at least one sensor is a monitoring sensor mounted outside the vehicle seat. The monitoring sensor is used in particular for monitoring the vehicle's interior. The monitoring sensor is an optical camera or, alternatively, a radar sensor.

[0029] In both cases, a defined reference area or reference point, specifically of the elastic sub-area, and its movement are detected and tracked. The monitoring sensor is preferably mounted away from the vehicle seat inside the vehicle, for example, in the vehicle's headliner.

[0030] To reliably identify and track the reference area, it is, for example, marked with a marker or designed as a marker. In the case of an optical camera, the reference area might have a color code and / or a pattern. When using a radar sensor, a radar-sensitive marker is employed, which is capable of reflecting radar waves. Such a radar-sensitive marker is, for example, integrated into or attached to the elastic section.

[0031] However, such a marker is not strictly necessary. The vibration behavior can also be recorded without one. For example, to determine the vibration behavior, the whole-body vibration of the vehicle seat and / or a person sitting on it is also recorded by the monitoring sensor.

[0032] According to a preferred embodiment, a sensor integrated into the vehicle seat is used to additionally detect the vibration behavior and, in particular, the resonance frequency. This sensor is integrated directly into the elastic section. Preferably, it is arranged within the seat cushion and, for example, within the upholstery. Alternatively, it can also be located outside the elastic section, for example, on its underside.

[0033] This integrated sensor is preferably an accelerometer. It is preferably mounted on the underside of the seat. It is attached, for example, mechanically using a clip or in some other way.

[0034] Alternatively or additionally, the integrated sensor is a capacitive sensor. This typically has two electrodes whose distance from each other can be changed. This sensor is also located, for example, on the underside of the seat. Preferably, it is located within the seat, particularly in the upholstery, i.e., typically within the foam.

[0035] According to a preferred embodiment, a reference sensor is used to detect the previously described vehicle-side excitation vibration and thus the external excitation vibration (external vibration excitation). By detecting at least one characteristic value of this external excitation vibration, which causes and initiates the vibrational behavior of the oscillating system, a more precise analysis is possible; in particular, further analytical options are available for determining and verifying whether a seat is occupied.

[0036] This reference sensor is preferably a vibration sensor already present in the vehicle, whose signals are also processed elsewhere. For example, the commonly installed ESP system accesses data from this reference sensor.

[0037] According to a preferred variant, at least one characteristic value of the excitation vibration is compared with a characteristic value of the vibration of the oscillating system. Based on this comparison, the seat occupancy is then deduced.

[0038] One of these parameters, at least, is the oscillation frequency.

[0039] According to a preferred embodiment, a phase relationship between the excitation vibration and the vibration of the oscillating system is determined. This is based on the consideration that the phase shift or phase ratio between the vehicle-side excitation and the vibration of the oscillating system (seat vibration) is influenced by the mass.

[0040] In particular, the reference sensor also enables the analysis of the oscillating system's response to external vibration excitation in the time domain. The greater the mass on the vehicle seat, the more sluggishly it reacts to the vehicle's vibration. Therefore, the inertia of the oscillating system is specifically evaluated and determined, i.e., its temporal response to external vibration excitation. This inertia is also reflected in the phase relationship, which is a measure of the time lag and thus of the system's inertia.

[0041] An embodiment of the invention is explained in more detail below with reference to the single figures.

[0042] This shows, in a highly simplified representation, a vehicle seat with a device for detecting whether the vehicle seat is occupied.

[0043] A vehicle seat 2 is arranged within a vehicle 4, shown here only as a dashed line, in particular a passenger car. The vehicle seat 2 has a seat section 6 and a backrest section 8, which is usually pivotable relative to the seat section 6. The vehicle seat 4 typically has a variety of adjustment options; in addition to the aforementioned tilt adjustment of the backrest section 8, the entire vehicle seat 2 is, for example, longitudinally adjustable on a rail system, and the seat section is, for example, height-adjustable. Depending on the comfort features, further seat adjustment options may be provided.

[0044] A device for detecting seat occupancy comprises an elastic section 10 of the vehicle seat 2, at least one sensor 12A, 12B, and an evaluation unit 14. The elastic section 10 is formed, in particular, by the seat part 6 or at least by a section of the seat part 6, for example, by padding (seat foam).

[0045] In the exemplary embodiment, two different types of sensors 12A and 12B are shown for illustrative purposes: a sensor 12A integrated into the vehicle seat 2, and in particular into the elastic section 10, and a monitoring sensor 12B located outside the vehicle seat 2. This monitoring sensor is, for example, installed in a headliner (not shown in detail here). In the exemplary embodiment, an optical camera is shown as the monitoring sensor 12B. The integrated sensor 12A is, for example, a capacitive sensor or an accelerometer.

[0046] Preferably, only one sensor 12A, 12B, or at least only one sensor type for the function of seat occupancy detection is present or at least used.

[0047] In a suitable configuration, this is a sensor 12A, 12B, which is also used for other functions, i.e. the sensor 12A, 12B is already present in vehicle 4 and no additional sensor 12A, 12B is required for seat occupancy detection.

[0048] In addition to sensors 12A and 12B, a reference sensor 13 is also arranged within the vehicle 2. This reference sensor 13 serves to detect a vehicle-side excitation vibration and thus to detect an excitation vibration that excites the elastic section 10 to vibrate. This excitation vibration is generated during driving, for example, due to uneven road surfaces and is transmitted to the vehicle seat 2 via the chassis / body. This reference sensor 13 is generally a sensor for detecting the vibration of at least one body component. Preferably, it is a sensor already installed in the vehicle for other purposes. Specifically, the reference sensor is part of an ESP system, or data from the reference sensor 13 are also used for the ESP system.

[0049] The at least one sensor 12A, 12B detects motion data of the elastic sub-section 10. Based on this motion data, a vibration behavior and, in particular, a vibration frequency of the elastic sub-section 10 is determined. Specifically, a resonance frequency of an oscillating mechanical system is determined. This system is formed by at least parts of the elastic sub-section 10 and by any additional mass located on the vehicle seat 2, specifically a person 16, which in the exemplary embodiment is only sketched and represented by dotted lines.

[0050] For reliable acquisition of motion data by at least one sensor 12A, 12B, a marker 18 is attached, specifically for the monitoring sensor 12B. The movement of the marker 18 is tracked by the at least one sensor 12A, 12B to determine the motion data. The marker 18 is, for example, applied to a surface of the elastic sub-area 10, formed by a sub-area of ​​the surface, or alternatively integrated within the elastic sub-area 10.

[0051] Specifically, the captured movement data from at least one sensor 12A, 12B is transmitted to the evaluation unit 14. This transmission can be either wireless or wired. The evaluation unit 14 is preferably an evaluation unit already present in the vehicle 4. For example, it is a seat control unit, which is typically installed within the vehicle seat 2. Such a seat control unit serves to control the adjustment movements of the vehicle seat 2. A suitable evaluation unit, in particular an evaluation algorithm, is therefore implemented in this existing control unit.

[0052] Alternatively, the evaluation unit 14 is also a higher-level control unit within the vehicle 4.

[0053] The evaluation unit 14 is generally designed for acquiring and evaluating sensor data from sensors 12A and 12B, which may already be partially processed. Within the evaluation unit 14, a processing unit, such as a chip, typically a memory, and the evaluation algorithm installed on the processing unit are present for this purpose.

[0054] The elastic section 10 generally has a spring constant, which is known and is stored, for example, in the evaluation unit 14 and specifically in the memory. Alternatively or additionally, a lookup table is stored.

[0055] Based on the transmitted movement data, a movement frequency of the elastic sub-area 10 and, for example, of the marker 18, and thus the resonance frequency, is determined.

[0056] The movements and vibrations of the elastic section 10, and thus of the oscillating system, are already caused passively during driving by the vibrations of the vehicle 2 that inevitably occur during driving, particularly due to road surface irregularities. These (vehicle) vibrations generally exhibit a very broadband vibration spectrum, so that the oscillating system is initially excited by a multitude of vibrations. Excitation at the natural frequency, and thus the resonance frequency, of the oscillating system is dominant due to the resonance effect, so that the measured vibration frequency is determined by the resonance frequency of the oscillating mechanical system.

[0057] From this, it is then deduced – either by calculation or by comparison with stored assignment data – whether vehicle seat 2 is occupied by an additional mass. Based on the specific resonance frequency, the actual weight is also inferred or calculated. Overall, the resonance frequency depends only on the constant, structurally predetermined spring constant and the vibration mass. The vibration mass is formed by the self-mass of the elastic section and, if there is an additional mass on vehicle seat 2, by this additional mass.

[0058] The previously described reference sensor 13 is used, in a preferred but not mandatory embodiment, to additionally verify whether a seat is occupied. Specifically, the data from reference sensor 13 are compared with the data from at least one of the other sensors 12A, 12B. Thus, characteristic values ​​of the excitation vibration are compared with, in particular, corresponding characteristic values ​​of the vibration of the oscillating system, and from this, it is deduced whether a seat is occupied. The evaluation is again performed using the evaluation unit 14, to which the data from reference sensor 13 are also transmitted.

[0059] In particular, a phase relationship is determined between the excitation vibration detected via the reference sensor 13 and the vibration of the oscillating system, and from this conclusions are drawn about the presence of a seat occupancy and in particular about the mass (weight).

[0060] As usual, based on the result of the detection of an occupancy of the vehicle seat, two further measures are initiated; in particular, an occupancy signal is emitted by the evaluation unit 14 and determined, for example, by a higher-level control unit.

[0061] The system described here, which measures the vibration behavior of the oscillating system and, in particular, its resonant frequency, enables a cost-effective and simple integration of seat occupancy detection. Specifically, it utilizes an already integrated sensor 12A, 12B, so that only the evaluation unit 14 needs to be upgraded. Reference symbol list 2 vehicle seats 4 vehicles 6 Seat section 8 Backrest section 10 elastic sub-area 12A integrated sensor 12B Monitoring Sensor 13 Reference sensor 14 evaluation units 16 people 18 markers

Claims

[1] Method for detecting that a vehicle seat (2) in a vehicle (4) is occupied, wherein at least one elastic part (10) of the vehicle seat (2) is used as part of an oscillating system, and wherein the oscillation behavior of the oscillating system is used to check whether the seat is occupied, characterized by , that a monitoring sensor (12B) mounted outside the vehicle seat (2) is used to detect the vibration behavior of the oscillating system and that the monitoring sensor (12B) is a camera or a radar sensor. [2] Method according to the preceding claim, wherein a resonance frequency of the oscillating system is detected and the resonance frequency is used to check whether a seat is occupied. [3] Method according to the preceding claim, wherein the oscillating system is excited to oscillate during driving operation due to the movements of the vehicle (4). [4] Method according to the preceding claim, wherein the oscillating system is a purely passive system without a vibration exciter integrated into the vehicle seat (2). [5] Method according to one of the preceding claims, wherein a sensor (12A) integrated into the vehicle seat (2) is used to detect the vibration behavior of the vibrating system. [6] Method according to the preceding claim, wherein the integrated sensor (12A) is integrated into a seat part of the vehicle seat (2). [7] Method according to one of the preceding claims, wherein an external excitation vibration is detected using a reference sensor. [8] Method according to the preceding claim, wherein at least one characteristic value of the excitation vibration is compared with a characteristic value of the vibration of the oscillating system. [9] Device for detecting occupancy of a vehicle seat (2), comprising an elastic section (10) of the vehicle seat (2), a sensor (12A, 12B), and an evaluation unit (14), wherein the elastic section (10) is part of an oscillating system and the sensor (12A, 12B) is designed to detect vibrations of the oscillating system, and wherein the evaluation unit (14) is configured to determine the vibration behavior of the oscillating system and to check, based on the determined vibration behavior, whether the seat is occupied, characterized by, that a monitoring sensor (12B) mounted outside the vehicle seat (2) is used to detect the vibration behavior of the oscillating system and that the monitoring sensor (12B) is a camera or a radar sensor. [10] Device according to the preceding claim, wherein the evaluation unit (14) is configured to determine a resonance frequency of the oscillating system and to use this to check whether a seat is occupied. [11] Device according to one of the two preceding claims, in which a sensor (12A) integrated in the vehicle seat (2) is additionally arranged. [12] Device according to the preceding claim, wherein the integrated sensor (12A) is an accelerometer or a capacitive sensor. [13] Device according to one of claims 9 to 12, in which a reference sensor is arranged for detecting an excitation vibration and the evaluation unit (14) is configured to compare at least one characteristic value of the excitation vibration with a characteristic value of the vibration of the oscillating system. [14] Device according to the preceding claim, wherein the evaluation unit (14) is configured to determine a phase relationship between the excitation vibration and the vibration of the oscillating system. [15] Device according to one of claims 9 to 14, wherein a weight sensor and / or a vibration exciter integrated into the vehicle seat (2) for the vibrating system is omitted.

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