US 12,411,209 B2
Method for seat occupancy detection
Janine Cordie, Echternacherbrück (DE); Andreas Diewald, Kell am See (DE); Oscar Gomez, Paris (FR); Alan Koehler, Igel (DE); Jochen Landwehr, Trier (DE); and Parth Raj Singh, Luxembourg (LU)
Assigned to IEE INTERNATIONAL ELECTRONICS & ENGINEERING S.A., Echternach (LU)
Appl. No. 17/787,833
Filed by IEE INTERNATIONAL ELECTRONICS & ENGINEERING S.A., Echternach (LU)
PCT Filed Dec. 15, 2020, PCT No. PCT/EP2020/086227
§ 371(c)(1), (2) Date Jun. 21, 2022,
PCT Pub. No. WO2021/122603, PCT Pub. Date Jun. 24, 2021.
Claims priority of application No. LU101570 (LU), filed on Dec. 20, 2019.
Prior Publication US 2023/0026131 A1, Jan. 26, 2023
Int. Cl. G01S 7/35 (2006.01); B60N 2/00 (2006.01); B60N 2/26 (2006.01); G01S 13/04 (2006.01); B60R 21/015 (2006.01); G01S 7/41 (2006.01); G01S 13/88 (2006.01); G01S 13/931 (2020.01)
CPC G01S 7/356 (2021.05) [B60N 2/0021 (2023.08); B60N 2/266 (2023.08); B60N 2/267 (2023.08); G01S 13/04 (2013.01); B60N 2210/16 (2023.08); B60N 2230/30 (2023.08)] 11 Claims
OG exemplary drawing
 
1. A method for occupancy detection for at least one vehicle seat, using at least one transmit antenna and a plurality of receive antennas, the method comprising:
emitting a detection signal with each transmit antenna onto at least one vehicle seat, which detection signal is a frequency-modulated continuous-wave radar signal, and receiving with each receive antenna a reflected signal;
recording sample data representing the reflected signal, the sample data having M channels, with M=N1·N2, where N1 is the number of transmit antennas and N2 is the number of receive antennas;
for each channel, removing a component from the sample data that corresponds to a reflection from a static object; and
applying a frequency estimation method to the sample data to at least implicitly determine at least one angle of arrival θi corresponding to a position of an occupant on a vehicle seat,
wherein the frequency estimation method is a multiple signal classification (MUSIC) method and includes:
calculating a sample covariance matrix R;
calculating eigenvalues and eigenvectors of the sample covariance matrix R;
sorting the eigenvalues in descending order and, with D being a number of targets, selecting M−D smallest eigenvalues and corresponding eigenvectors to determine a noise subspace G; and
calculating roots zi of a root-MUSIC polynomial J(z) with
J(z)=zM-1pT(z−1)GGRp(z)
wherein

OG Complex Work Unit Math
 and each root zi corresponds to an angle of arrival θi,
wherein for each seat, an associated area in the complex plane is defined and for each frame, which corresponds to a plurality of modulation periods of the detection signal, a counter for this associated area is increased if at least one root zi is located in this associated area and decreased if there is no root zi in this associated area and the seat is identified as occupied if the counter exceeds a predefined threshold.