Method for detecting seat occupancy in a vehicle

Abstract

The invention relates to a method for detecting the occupancy of at least one of several seats in a vehicle cabin of a vehicle (20), wherein radar pulses are emitted into the vehicle cabin by means of a transmitter (5) of a single UWB module (1) arranged on a symmetrical central axis longitudinal to a direction of travel on a ceiling (21) of the vehicle cabin, which has several receivers (6), wherein radar pulses reflected in the vehicle cabin are received by means of the receivers (6) and, based on the angles of incidence of the received radar pulses, it is detected which of the seats is occupied by an occupant (10).

Description

[0001] The invention relates to a method for detecting an occupancy of at least one of several seats in a vehicle cabin of a vehicle according to the preamble of claim 1.

[0002] Conventional seat occupancy detection systems in vehicles often rely on weight sensors embedded in seats to determine whether a seat is occupied. These systems can be expensive and complex, requiring maintenance and calibration. There is a need for a more efficient and accurate method of detecting seat occupancy without the need for weight sensors, particularly to ensure seatbelt warnings are triggered correctly.

[0003] DE 10 2022 122 348 A1 describes a device and a method for precise seat occupancy detection in a vehicle. The device comprises an ultra-wideband (UWB) radar including a transmitter and at least two receivers, wherein the transmitter is configured to send a plurality of preamble symbols towards the vehicle seats; and wherein the at least two receivers are configured to receive the preamble symbols reflected by the vehicle seats. The device includes a processing unit configured to generate channel impulse responses (CIRs) from the received, reflected preamble symbols and to process the generated CIRs using a suitable machine learning algorithm; to perform an angle-of-arrival calculation based on the reflected preamble symbols; and to determine the occupancy of the vehicle seats from the processed CIRs and the performed angle-of-arrival calculation.

[0004] The invention is based on the objective of providing a novel method for detecting the occupancy of at least one of several seats in a vehicle cabin.

[0005] The problem is solved according to the invention by a method for detecting an occupancy of at least one of several seats in a vehicle cabin of a vehicle with the features of claim 1.

[0006] Advantageous embodiments of the invention are the subject of the dependent claims.

[0007] A method for detecting the occupancy of at least one of several seats in a vehicle cabin is proposed. According to the invention, radar pulses are emitted into the vehicle cabin by means of a transmitter of a single UWB module arranged on a symmetrical central axis longitudinally to a direction of travel on a ceiling of the vehicle cabin, which has several receivers. Radar pulses reflected in the vehicle cabin are received by the receivers, and the angle of incidence of the received radar pulses is used to detect which of the seats is occupied by an occupant.

[0008] The present invention relates to a system for detecting seat occupancy in a vehicle, which uses ultra-wideband radar (UWB) technology. The invention eliminates the need for weight sensors in each seat to trigger seatbelt warnings, thereby reducing costs and complexity and improving safety. In particular, a UWB module is used to detect the presence of children in order to accurately determine whether a person is sitting in a seat. Such sensors are currently mainly used to detect the presence of a child left in a parked vehicle (to prevent health problems caused by heat in the vehicle) or to locate a smartphone. The present invention utilizes such a UWB module for additional purposes.

[0009] The system uses a single UWB module, strategically placed within the vehicle, to accurately detect the presence of a person in each seat. This technology enables precise seat occupancy detection, particularly for triggering seatbelt warnings, without the need for weight sensors. For example, a seatbelt warning can be triggered if the vehicle is in motion and an occupant is not wearing a seatbelt. The user experience remains unaffected, and no user action is required.

[0010] The solution according to the invention can also be configured and / or suitable to distinguish between different types of occupants and objects.

[0011] Using the UWB module and intelligent fusion technology, the presence of a user in the vehicle's cockpit can be detected when they sit down. If an automatically closing door is present, it can then be closed immediately without having to wait for a timer to expire.

[0012] Exemplary embodiments of the invention are explained in more detail below with reference to drawings.

[0013] This shows: Fig. 1 a schematic view of a UWB module, Fig. 2 schematic views of a vehicle with a UWB module, Fig. 3 A schematic view of a transmitting antenna and two receiving antennas during the reflection of a signal from a distant object, Fig. 4 A schematic view of a transmitting antenna and two receiving antennas in a detailed reflection case on both receiving antennas, Fig. 5 A schematic view to illustrate a phase difference between a plurality of receiver antennas.

[0014] Corresponding parts are marked with the same reference symbols in all figures.

[0015] UWB sensors are used in vehicles 20 to detect the presence of children. These sensors operate on the UWB frequency and are used for so-called "ranging" and "radar" functions. Ranging functions calculate the time of flight (TOF) of a user's device to locate them. This capability is used both for vehicle access 20 and for starting the engine. With a different antenna and a hardware upgrade, these sensors can distinguish movements down to the millimeter. If a child is breathing in the vehicle 20, the UWB module 1 can detect them as long as they remain in the cockpit. This function has been an NCAP requirement for achieving a five-star rating since 2024.

[0016] The idea of ​​the present invention is to use the radar function of the UWB sensor for seatbelt warning detection. UWB radar pulses are emitted into the cockpit of the vehicle 20 to detect whether movements of large bodies are occurring in the area of ​​or towards the seats. A movement of a body the size of a person is detectable by a clearly distinguishable pulse response from the UWB sensor, allowing a signal to be transmitted to a processing unit to signal the presence of a person in real time. This triggers a warning if the user has not fastened their seatbelt and the vehicle 20 is in motion.

[0017] The UWB module 1 can emit short pulses in the UWB radio wave range for environmental detection. The UWB module 1 has a transmitter section that sends nanosecond pulses in the time domain and a receiver section that measures reflected signals from the environment, including the angle of incidence of the signals.

[0018] Fig. Figure 1 is a schematic view of a UWB module 1.

[0019] The UWB module 1, which also functions as a pulse-based radar, includes the following components: a system clock 2, a pulse wave generator 3, a signal amplifier 4, a transmitter 5, a receiver 6, a wave delay detector 7 and a localizer 8.

[0020] The UWB module 1 operates over a wide frequency range, typically from 3.1 GHz to 10.6 GHz, enabling high-resolution spatial measurements. It uses short-time pulses, which, due to their high temporal resolution, allow for the measurement of precise distances and locations.

[0021] Fig. Figure 2 shows schematic views of a vehicle 20, for example a passenger car, a commercial vehicle or a bus, with a UWB module 1.

[0022] According to the present invention, a single UWB module 1 is arranged in or on the ceiling 21 of a vehicle cabin of the vehicle 20. The UWB module 1 has a plurality of built-in antennas 9, at least one transmitter 5, and several receivers 6 and is configured to locate each of, for example, a maximum of five or more occupants 10 by determining an angle of incidence (AoA). The UWB module 1 can further be configured to locate a user's authentication device and to detect the presence of children. The UWB module 1 is arranged in the center of the ceiling 21 of the vehicle cabin in order to be able to detect movement even in the footwell of the cabin.

[0023] A single UWB module 1 is strategically positioned at the top of the vehicle cabin, for example, near a central point, to maximize coverage. UWB module 1 is configured to measure the angle of arrival (AoA) at which reflected signals reach the module. By analyzing this angle, the position of occupants 10 within the vehicle cabin can be determined.

[0024] To focus the detection capabilities of UWB module 1, advanced algorithms can be used to differentiate between various seats and occupants. UWB module 1 is capable of handling multipath reflections (signals reflected from surfaces). This improves the accuracy in detecting occupants, even in complex vehicle cabin environments.

[0025] Based on unique radar signatures, UWB Module 1 can detect the presence of living beings, including distinguishing between adults, children, and infants. Furthermore, UWB Module 1 can track movements within the vehicle cabin to provide real-time updates on the positions and activities of the occupants.

[0026] The UWB module 1 can be connected to or integrated with the vehicle's access control system 20 to identify occupants 10 and verify authorized users. UWB technology can ensure that data is processed locally within the vehicle 20 to minimize privacy concerns that may be associated with external data transmission.

[0027] The use of a single UWB module keeps hardware costs low and simplifies installation compared to systems with multiple sensors. AoA technology ensures that all seats are efficiently monitored and the entire vehicle cabin is covered. Based on accurate occupant detection, the system can trigger safety mechanisms, such as airbags, based on real-time data.

[0028] Fig. Figure 3 is a schematic view of a transmitting antenna TX and several receiving antennas RX during the reflection of a signal from a distant object O.

[0029] Fig. Figure 4 is a schematic view of a transmitting antenna TX and several receiving antennas RX in a detailed reflection case on both receiving antennas RX.

[0030] In the described scenario, a radar system (UWB sensor) with a transmitting antenna TX is used to emit a signal. This signal is reflected by a distant object O, and the reflected signal is received by multiple receiving antennas RX. The method of using lines to represent the transmitted and reflected signals is known as ray tracing and simplifies the modeling of these signals.

[0031] The elementary geometry shows that the distance d, which the signal travels from object O to each receiver antenna RX, differs by a factor of Δd: Δd=dsin(θ)

[0032] This difference in path length results in a phase shift in the signal received by each receiver antenna (RX). This phase shift is used to determine the angle of incidence (AoA). This phase shift, also known as phase delay or phase difference, is defined as follows: Phase shift = w = 2π Dsin(θ)λ

[0033] Here, D is the distance between the receiving antennas. This phase shift can be expressed in complex phasor form: exp(−j2π Dsin(θ)λ)

[0034] This approach can be extended to more than two receiver antennas RX arranged in a uniform linear array (ULA), as can be used in the present case in the UWB sensor 1.

[0035] Fig. Figure 5 is a schematic view to illustrate the phase difference with a plurality of receiver antennas RX.

[0036] It is evident how the phase difference scales based on the position of the receiver antennas (RX) and that only one axis is considered. The angle can be estimated by performing a Fast Fourier Transform (FFT) over the dimension of the receiver antenna (RX) of a radar data cube, allowing the use of phase differences across spatially separated chirps (compressed high-intensity radar pulses). The resulting FFT is sometimes referred to as the spatial spectrum.

[0037] However, the FFT method alone does not necessarily lead to accurate results in all cases. More advanced techniques, known as beamforming, offer better estimates of the spatial spectrum. These algorithms scan a virtual beam over a multitude of locations and calculate a response. If this response exceeds a certain threshold, a detection can be confirmed. Beam scanning is achieved through a technique known as steering vectoring.

[0038] The steering vector defines the direction of a signal or beam relative to the array and remains the same regardless of whether the signal is sent or received.

[0039] Essentially, the steering vector represents a complex phasor representation of the incoming signal, which is composed of two vectors: Wave vector: k=(kx,ky,kz) Element position vector: rm=(xm,ym,zm) with a total of m positions

[0040] The element position vector shows the position of each receiving element. The wave vector represents the direction of the incoming signal at a specific frequency: Although the term "wave vector" may seem complex, it can be simplified to a vector that describes the direction of the signal at a given frequency.

[0041] The derivation of the steering vector from the radar data is as follows: vm(k)=exp(−jk⋅rm) vm(k)=exp(−j(kx,ky,kz)⋅(xm,ym,zm)) vm(k)=exp(−jkxxm) only the x-axis is valid vm(k)=exp(−j2πλsin(θ)xm) vm(k)=exp(−j2πλsin(θ)mλ2) Distance is half the wavelength, therefore each xi is λ2 vm(k)=exp(−j π m sin(θ))

[0042] This derivation assumes a spacing of half a wavelength between the elements, as can be used in the present radar system. The resulting equation provides a complex phasor for an incoming signal at an angle θ for each antenna element m. This allows the phase difference at each element to be described easily using the steering vector.

[0043] In summary, a single UWB module 1 with multiple receivers 6 and / or receiver antennas RX represents an advanced solution for reliable occupant detection throughout the cockpit. This technology enhances safety and offers a simple and economical implementation.

[0044] UWB modules 1 can be used to detect the position of a person's smart device. The discrete-time position information can be used to recalibrate the user's trajectory within and around the vehicle 20. The single UWB module 1, located inside the vehicle cabin, is used to detect the body of an occupant 10 within the cabin. When one of the receivers 6 receives a signal with an angle of incidence reflected from the body of the occupant 10, it can detect that the occupant 10 is in close proximity to a seat (during the dynamic movement of sitting). The system can then mark the timestamp to indicate that the seat in question is occupied. After sending and receiving several pulses, the UWB module 1 has a rough indication of the occupant 10's position.This position information (from the UWB radar) is weighted more heavily than in conventional UWB time-of-flight localization. Therefore, after several measurements, more accurate information is available as to whether occupant 10 is sitting in the vehicle cabin. Reference symbol list 1 UWB module 2 System clock 3 Pulse wave generator 4 signal amplifiers 5 channels 6 recipients 7-wave delay detector 8 Locators 9 Antenna 10 inmates 20 vehicles 21 Ceiling d distance D distance O object Rx receiver antenna Tx transmitter antenna Δd factor θ angle QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2022 122 348 A1

[0003]

Claims

[1] Method for detecting that at least one of several seats in a vehicle cabin of a vehicle is occupied (20), characterized by , that radar pulses are emitted into the vehicle cabin by means of a transmitter (5) of a single UWB module (1) arranged on a symmetrical central axis longitudinal to a direction of travel on a ceiling (21) of the vehicle cabin, which has several receivers (6), wherein radar pulses reflected in the vehicle cabin are received by means of the receivers (6) and, based on the angles of incidence of the received radar pulses, it is detected which of the seats is occupied by an occupant (10). [2] Method according to claim 1, characterized by , that the UWB module (1) is located near a center point of the ceiling (21). [3] Method according to claim 1 or 2, characterized by , that the angle of incidence is determined from a phase shift of the received radar pulses between the receivers (6). [4] Method according to claim 3, characterized by , that the angle of incidence is estimated by performing an FFT over the dimension of a receiver antenna (RX) of a radar data cube, thereby using phase differences over spatially separated chirps. [5] Method according to any one of the preceding claims, characterized by , that beamforming and / or a steering vector is used to detect the occupancy of at least one of several seats. [6] Method according to claim 5, characterized by that the receiver antennas (RX) are arranged in an array with a spacing of half a wavelength of a signal used for the radar pulses between the receiver antennas (RX).

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