Method for tracking the position of a target
A method using pulsed radio frequency signals for vehicle localization without user-worn devices achieves precise and reliable tracking by discriminating target presence from noise, addressing the constraints of existing UWB systems.
Patent Information
- Authority / Receiving Office
- FR · FR
- Patent Type
- Applications
- Current Assignee / Owner
- SCHAEFFLER TECHNOLOGIES AG & CO KG
- Filing Date
- 2024-12-19
- Publication Date
- 2026-06-26
Abstract
Description
Title of the invention: Method for tracking the position of a target technical field
[0001] The present disclosure falls within the domain of methods for tracking the position of a target relative to a part of a motor vehicle. Previous technique
[0002] The field of UWB (“Ultra Wideband”) radar sensors concerns detection and localization technology using wideband radio frequency signals. A wideband radio frequency signal is an electromagnetic signal comprising a carrier with a frequency, for example, between 3 kHz and 300 GHz, but most often between 5 GHz and 30 GHz.
[0003] UWB radar sensors emit short, broad-spectrum radio frequency pulses, enabling high temporal resolution and penetration capability through various materials.
[0004] These sensors find applications in fields such as motion detection, the localization of people and objects, as well as in vehicle security and access systems.
[0005] Applications in this field also include the precise and real-time location of users or objects, the monitoring of movements and gestures, as well as the improvement of vehicle safety and accessibility.
[0006] UWB radar sensors are used to track user movements around vehicles, detect gestures for opening doors, and monitor security zones to prevent intrusions.
[0007] These applications require reliable and accurate detection, even in the presence of obstacles or interference.
[0008] One of the main obstacles to achieving these objectives is the need for the user to wear a UWB device to establish communication with the sensors integrated into the vehicles. This requirement limits the convenience and effectiveness of location and tracking systems, as it imposes an additional constraint on the user. Furthermore, current location methods based on measuring the time of flight between UWB devices can be complex and costly to implement.
[0009] It is known from the prior art that the localization of users around vehicles is carried out by systems, called "secure ranging", using UWB devices worn by users, such as badges for example.
[0010] These systems measure the time of flight of signals between the UWB devices worn by users and the UWB anchors integrated into vehicles to determine the position of the users.
[0011] However, this approach requires the user to wear a UWB device, which poses an additional constraint.
[0012] There is therefore a need for a system for locating and tracking the trajectory of users around vehicles that does not require the user to wear a UWB device. Such a system would allow for more practical and efficient detection and tracking, thereby improving vehicle safety and accessibility. Summary
[0013] To this end, the present document proposes a method for tracking the position of a target, such as a portion of a user's body, relative to a part of a motor vehicle, said method comprising the steps of:
[0014] (a) emit, using at least one first and one second transceiver, a a pulsed radio frequency signal called the forward signal, intended to be reflected at least partially by said target,
[0015] (b) receive, using said at least one first and one second transceiver, a radio frequency signal called the return signal, resulting from the reflection of the forward signal on said target,
[0016] (c) demodulate the return signal and extract the signals I(t) and Q(t) defining two components in phase and in quadrature of phase respectively using a mixer,
[0017] (d) obtain sampled data I(tijk) and Q(tijk) corresponding to a temporal sampling of the signals I(t) and Q(t), ti>k being a sampling instant called short time, associated with a short sampling period, and the sampled data I(tijk) and Q(tijk) being grouped into vectors 1(6) and Q(f), h being a sampling instant called long time, associated with a long sampling period,
[0018] (e) perform steps (f) to (h) for each transceiver,
[0019] (f) for each long time ti data and each short time tijk data, calculate the standard deviation oijk_dataof one of ICIR(ti>k data)l, I(ti>k data) and Q(ti>k data),
[0020] (g) compare oijk data with a corresponding threshold standard deviation _seuii so as to assign at each short time ti>k data a number Nijk data satisfying: if okk_data Gi,k _seuii, Nijk_data — 1, and if Cf k_data < Oijk_threshold, Nijk_data — 0, (h) search, for at least a long time ti_data_min, the smallest short time tijk_data_min corresponding to a number Ni>k_data satisfying Nijk_data = 1;
[0021] (i) deduce the position of the target at each of said at least a long time ti data _min.
[0022] Step (d) corresponds to double sampling: - a first rapid sampling with short time sampling instants tijk, preferably at a sampling frequency of the order of 1 GHz, the frequency of the first rapid sampling corresponding to the sampling period by the analog-to-digital converter of a chip of said at least a first and a second transceiver; - a second slow sampling with long-time sampling intervals (f) corresponding to the repetition period of the pulse trains of the forward signal. For example, the frequency of the second slow sampling could be on the order of kHz. The interval between the long-time sampling intervals could be 2 ms.
[0023] The grouping of the sampled data I(ti,k) and Q(ti,k) into vectors I(ti) and Q(ti) corresponds to a folding of the time axis. In other words, in each vector I(ti) and Q(ti) are the data associated with one of the pulse trains of the emitted signal.
[0024] From the point of view of each vector I(ti) and Q(ti), the second slow sampling is similar to a spatial sampling: the first value corresponds to a zero distance of the target from the receiver, the transceiver or the vehicle; the second value, following the first value, corresponds to a first time of flight of the signal associated with a first distance of the target from the receiver, the transceiver or the vehicle; and so on.
[0025] By demodulating the received radio frequency signal into in-phase and quadrature-phase components (step (c)), and then sampling these signals in time (step (d)), the tracking method makes it possible to extract precise time information on the movement of the target.
[0026] Long time intervals f are also called "taps," which are discrete intervals in the numerical representation of the distance axis in a radar signal processing context. The distance between the target and the receiver or transceiver is calculated by multiplying the number of taps by the distance.
[0027] A "tap" can, for example, represent a distance of 15 cm.
[0028] The tracking method has the advantage of not requiring a transmit-receive device, such as a badge, that the target must wear to carry out its tracking.
[0029] Indeed, the process is based, for a short time ti>k data of each transmitter-receiver, on the comparison of the standard deviation 0ijk_data with the threshold standard deviation 0l k _seuii. Therefore, only data from the first and second transmitter-receivers are required here.
[0030] The condition oijk_data > Gi* _seuii corresponds to a situation in which the chosen values (ICIR(tijkdata)l, I(tijk data) or Q(ti,k data)) exhibit a dispersion over a range of values greater than the threshold value, which is synonymous with the presence of the target at the corresponding long time ti data and short time ti>k data. This discriminates false positives corresponding, for example, to accidental or unintentional movements.
[0031] This standard deviation _seuiicorresponds to a standard deviation of inactivity of the target.
[0032] Comparing standard deviations ensures consistent monitoring of the target, and to avoid possible false positives which are discriminated at step (g), the latter having a number Nijk data = 0.
[0033] Step (i) is equivalent to the long time search ti data of the short time tijk data min for which Nijk_data = 1, that is to say the tijk_data_min for which there is presence of the target, for each transmitter-receiver.
[0034] This short time tijk data min corresponds to the intersection between the signals emitted from the first and second transceivers for which there is presence of the target for both transceivers.
[0035] Step (i) corresponds to the deduction from the tijk_data_min for each at least one long time f corresponding data and for each transmitter-receiver of the trajectory of the position of the target.
[0036] The motor vehicle can be of reference frame Rv, the reference frame Rv having as its origin a point of the motor vehicle, the forward signal propagating uniformly in all directions, the step (i) comprising the determination of an intersection of the forward signals of the first and second transmitters-receivers at every at least a long time ti_data_min, said intersection corresponding to the intersection of a first and second circles having as their center the position of the first and second transmitters-receivers respectively and as their radius the corresponding short time tijk_data_min, in an analysis plane of the reference frame Rv parallel to a plane on which the wheels of the motor vehicle rest.
[0037] The forward signal propagating uniformly in all directions ensures homogeneous coverage around the vehicle. This improves detection reliability by guaranteeing that the target is detected consistently, regardless of its position relative to the corresponding transceiver (and therefore relative to the vehicle).
[0038] Determining the intersection (the short time tijk data min) of the forward signals from the first and second transceivers at each long time tij data allows for precise localization of the target using a triangulation method. This approach improves the accuracy of the localization by combining information from the first and second transceivers to determine the exact position of the target.
[0039] The intersection of the circles of radius tijk_data_min of the first and second transmitter-receivers in an analysis plane of the reference frame Rv parallel to a plane on which the wheels of the motor vehicle rest allows the trajectory of the target to be followed in a horizontal plane (the analysis plane), the forward signals being equivalent to circles in said plane.
[0040] The analysis plan may be a plan located opposite the part of the motor vehicle and including said part of the motor vehicle.
[0041] By limiting the analysis plan to the part of the motor vehicle and including said part of the vehicle, the method makes it possible to concentrate the detection and tracking of the target in a specific area of interest.
[0042] Indeed, this makes it possible to discriminate the intersection (among the two possible intersections) of the circles of radius tijk_data_min of the first and second transmitter-receivers which is not relevant, namely the one which is not opposite the part of the motor vehicle.
[0043] oijk _seuiipeut be between 25% and 35%, preferably 30%, of an empty standard deviation Oijc _empty of the time COURt tiîk_data.
[0044] By fixing this interval, the method optimizes the sensitivity and accuracy of target detection. This range of values for the threshold standard deviation is chosen to balance the detection of actual target movements while minimizing false positives due to background noise or minor signal variations.
[0045] This document may also relate to a method for controlling an opening of a motor vehicle comprising the tracking method according to the aforementioned type, said control method further comprising: a. Determine if the target's position at each of said at least one long time interval (f_data_min) corresponds to a voluntary movement of the target. b. where appropriate, control a locking or unlocking of the opening, and / or respectively an opening or closing of the opening, and / or respectively a tilting from a rest position to a gripping position of a flush handle of the opening.
[0046] This document may also relate to a computer intended for installation in a motor vehicle comprising at least one processor and at least one memory, said at least one processor having access to said at least one memory to read the steps stored in said at least one memory, said computer being characterized in that it is configured for the implementation of each of the steps of a control process according to the aforementioned type or a monitoring process according to the aforementioned type.
[0047] This document may also relate to a system for managing an opening of a motor vehicle intended to be installed in said motor vehicle, characterized in that the system comprises:
[0048] - at least one first and one second transceivers intended to emit the signal emitted and received return signal, and
[0049] - an electronic management module comprising a computer of the type mentioned above.
[0050] This document may also relate to a motor vehicle equipped with an opening, characterized in that it includes a system for managing said opening according to the aforementioned type. Brief description of the drawings
[0051] Other features, details and advantages will become apparent from reading the detailed description below, and from analyzing the accompanying drawings, on which:
[0052] [Fig-1] is a schematic view of a motor vehicle according to a mode of production of this document,
[0053] [Fig.2] is a block diagram of a method for controlling an opening of a motor vehicle according to an embodiment of this document,
[0054] [Fig.3] is a horizontal cross-sectional view of a rear bumper of the motor vehicle of [Fig.1], with an example of a straight trajectory of a target,
[0055] [Fig.4] is a graph of a return signal resulting from the reflection of the target along the trajectory shown in [Fig.3],
[0056] [Fig.5] illustrates a table established according to the method of managing the opening of a door of a motor vehicle of [Fig.2], and
[0057] [Fig. 6] is a horizontal cross-sectional view of a rear bumper of the motor vehicle of [Fig. 1], with a target trajectory deduced from [Fig. 5]. Description of embodiments
[0058] Fig. 1 schematically represents a motor vehicle 1 comprising a movable opening 2, capable of being controlled by a management system for said opening 2.
[0059] In the illustrated example, the opening 2 is the rear trunk of the motor vehicle 1.
[0060] Said management system comprises: - a first and a second transceiver arranged in a rear part 4 of the motor vehicle 1 (here the rear bumper 4), and - an electronic management module including a computer.
[0061] The computer includes a processor and at least one memory, and is configured to implement each of the steps of a method for managing the opening of the opening 2.
[0062] The computer is capable of generating an output signal enabling the control of the opening 2.
[0063] The method of controlling the opening 2 according to an embodiment of this document is described below with reference to [Fig.2].
[0064] In particular, the method for controlling the opening 2 includes a method for tracking the position of a target relative to the rear bumper 4 of the motor vehicle 1 (steps EA to El).
[0065] During an EA step, a pulsed radio frequency signal called the forward signal is emitted using at least one first and one second transceiver, intended to be reflected at least partially on said target.
[0066] An example of this transmission of the forward signal is shown in [Fig.3] which illustrates, according to a horizontal cross-section (i.e. parallel to the ground on which the wheels of the motor vehicle 1 rest), the rear bumper 4 and the first and second transmitter-receivers 12, 14 arranged at the lateral ends of the rear bumper 4.
[0067] In operation, each transceiver 12, 14 emits a uniform forward signal in all directions (equivalent to a circular signal along the horizontal plane).
[0068] As it propagates, the forward signal can be illustrated in the form of several circles TAP1, TAP2, TAP3, TAP4, TAP5, TAP6, TAP7, TAP8, TAP9, TAP10 whose center corresponds to the position of the respective transmitter-receiver 12, 14 and whose radius is defined by the associated "tap" (i.e. the distance from the position of the transmitter-receiver 12, 14).
[0069] Here, a "tap" corresponds to a distance of 200 mm.
[0070] During a step EB, a radio frequency signal called the return signal is received, using said at least one first and one second transceiver 12,14, from the reflection of the forward signal on said target.
[0071] During an EC step, the return signal is demodulated and the signals I(t) and Q(t) defining two components in phase and in quadrature of phase respectively are extracted using a mixer.
[0072] During an ED step, sampled data I(ti>k) and Q(tik) are obtained corresponding to a time sampling of the signals I(t) and Q(t), tik being a sampling instant called short time, associated with a short sampling period, and the sampled data I(ti>k) and Q(t; k) being grouped into vectors I(t;) and Q(ti), f being a sampling instant called long time, associated with a long sampling period.
[0073] During an EE step, for each transmitter-receiver 12, 14, the steps EF to EH are carried out.
[0074] During an EF step, for each long time ti data and each short time ti>k data, the standard deviation 0ijk_data of one of ICIR(ti>k data)l, I(ti>k data) and Q(ti>k data) is calculated.
[0075] During an EG step, Oi^data^c is compared with a corresponding threshold standard deviation oi>k_seud so as to assign to each short time tijk_data a number Nijk_data satisfying: If 0,k_data ^i,k _seuib Nkk_data 1, and If 0i ,k_data — ^i,k _seuib Nkk_data 0.
[0076] In this way, for each long time t;_data, only the short times tijk_data are considered relevant with regard to the presence of the target, which translates to Ni^data = 1 •
[0077] By way of example, the path of the target from position M1 to position M2 (see [Fig. 1]) towards the transceiver 12 arranged at the left lateral end of the rear bumper 4 corresponds to time intervals 110, 19, 18, 17, 16, 15, 14, 13, 12, 11 of each tap TAP10, TAP9, TAP8, TAP7, TAP6, TAP5, TAP4, TAP3, TAP2, TAP1 with Nijk_data = L
[0078] Thus, the EG step makes it possible to discriminate between irrelevant moments and taps during which the target is not present.
[0079] If we take a case of an arbitrary trajectory of a target, the EG step allows us to establish a table as illustrated on [Fig.5] with the different long times h dataGci t0, tl, t2, t3, t4, t5, t6, t7, t8, t9, tl0, tll, tl2) in rows and the different taps ti>k data (here TAPI, TAP2, TAP3, TAP4, TAP5, TAP6, TAP7, TAP8, TAP9, TAP10) in columns.
[0080] The binary values shown in each box correspond to the associated Nijk_data = 1.
[0081] During an EH step, for at least a long time tLdata, the smallest short time tijk_data_min corresponding to a number N^data satisfying Nijk_data = L is sought.
[0082] Reference is now made to [Fig. 5] in which step EH corresponds to the reading, line by line, of the smallest tap for which Nijk_data = 1-
[0083] For example, for the long time tl: - For transceiver 12, the smallest tap (tijk_data_min) is TAP4; and - For transceiver 14, the smallest tap (tijk_data_min) is TAP10.
[0084] As illustrated in [Fig.6], the first position of the target tracking is the PI position which is the intersection between the circle TAP4 of the transceiver 12 and the circle TAP10 of the transceiver 14.
[0085] With regard to the subsequent second position, for the long time t2: - For transceiver 12, the smallest tap is TAP3; and - For transceiver 14, the smallest tap is TAP9.
[0086] As illustrated in [Fig.6], the second position of the target tracking is position P2, which is the intersection between circle TAP3 of the transceiver 12 and circle TAP9 of the transceiver 14, and so on.
[0087] Since the intersection of two circles includes two points, the method restricts the analysis plane to a plane located opposite the rear bumper 4 of the motor vehicle and including said rear bumper 4 of the motor vehicle.
[0088] The analysis plane here is the PA plane which includes the rear end of the rear bumper 4 as well as the area opposite said rear bumper 4.
[0089] During a step El, the position of the target is thus deduced at each of said at least one long time ti data _min, by determining an intersection of the forward signals of the first and second transmitter-receivers at each of at least one long time tL data _min, said intersection corresponding to the intersection of a first and second circles having as its center the position of the first and second transmitter-receivers respectively and as its radius the corresponding short time tijk_data_min, in an analysis plane of the reference frame Rv parallel to a plane on which the wheels of the motor vehicle rest.
[0090] The complete trajectory of the target is illustrated on [Fig.6] with the remaining positions P3, P4, P5, P6, P7, P8, P9, P10, P12.
[0091] During an EJ step, it is determined whether the position of the target at each of said at least a long time ti data _min corresponds to a voluntary movement of the target.
[0092] During an EK step, a locking or unlocking of the opening is controlled, and / or respectively an opening or closing of the opening, and / or respectively a tilting from a rest position to a gripping position of a flush handle of the opening.
Claims
1. Demands Method for tracking the position of a target, such as a portion of a user's body, relative to a part (4) of a motor vehicle (1), said method comprising the steps of: (a) transmitting (EA), using at least a first and a second transceiver (12, 14), a pulsed radio frequency signal called the forward signal intended to be reflected at least partially by said target, (b) receive (EB), using said at least one first and one second transceiver (12, 14), a radio frequency signal called the return signal, resulting from the reflection of the forward signal on said target, (c) demodulate (EC) the return signal and extract the signals I(t) and Q(t) defining two in-phase and quadrature-phase components respectively using a mixer, (d) obtain (ED) sampled data I(t; >k) and Q(tik) corresponding to a time sampling of the signals I(t) and Q(t), tik being a short-time sampling instant associated with a short sampling period, and the sampled data I(t; >k) and Q(tik) being grouped into vectors ht,) and Q(t;), h being a long-time sampling instant associated with a long sampling period, (e) perform (EE) for each transmitter-receiver the steps (f) to (h), (f) for each long time f_data and each short time tijk_data, calculate (EF) the standard deviation oijk_data of one of ICIR(ti>k_data)l, I(ti>k_data) and Q(ti>k_data), (g) compare (EG) o; >k_data with a corresponding threshold standard deviation _ seuii so as to assign to each short time ti>k data a number Ni>k_data satisfying: if O; îk_dadl okk _ Seuib Nijk_data 1, and If ,k_data — ^i,k _ threshold, Nkk_data 0, (h) search (EH), for at least one long time ti data _min, the smallest short time ti>k data _min corresponding to a number Nijk data satisfying Nijcdata = 1; (i) deduce (E1) the position (PI, P2, P3, P4, P5, P6, P7, P8, P9, P10, P11, P12) of the target at each of said at least one long time ti data min*
2. A tracking method according to claim 1, wherein the motor vehicle (1) has a reference frame Rv, the reference frame Rv having its origin at a point of the motor vehicle (1), the forward signal propagating uniformly in all directions, step (i) comprising determining an intersection of the forward signals of the first and second transmitter-receivers (12, 14) at every at least one long time tijk_data_min, said intersection corresponding to the intersection of a first and second circles having as their center the position of the first and second transmitter-receivers respectively and as their radius the corresponding short time tijk_data_min, in an analysis plane of the reference frame Rv parallel to a plane on which the wheels of the motor vehicle (1) rest.
3. A tracking method according to the preceding claim, wherein the analysis plane is a plane located opposite part (4) of the motor vehicle (1) and comprising said part (4) of the motor vehicle (1).
4. A tracking method according to any one of the preceding claims, wherein 0lk _ seuiiest is between 25% and 35%, preferably 30%, of an empty standard deviation _empty of the short time tijk data.
5. A method for controlling an opening (2) of a motor vehicle (1) comprising the tracking method according to any one of the preceding claims, said control method further comprising: a. Determining (EJ) whether the position of the target at each of said at least a long time ti data _min corresponds to a voluntary movement of the target, b. If so, controlling (EK) a locking or unlocking of the opening (2), and / or respectively an opening or closing of the opening (2), and / or respectively a tilting from a rest position to a gripping position of a flush handle of the opening (2).
6. A computer intended to be installed in a motor vehicle (1) comprising at least one processor and at least one memory, said at least one processor having access to said at least one memory to read the steps stored in said at least one memory, said computer being characterized in that it is configured for the implementation of each of the steps of a control process according to the preceding claim or a monitoring process according to any one of claims 1 to 4.
7. A system for managing an opening (2) of a motor vehicle (1) intended to be installed in said motor vehicle (1), characterized in that the system comprises: - at least one first and one second transceiver (12, 14) intended to transmit the signal emitted and to receive the return signal, and - an electronic management module comprising a computer according to the preceding claim.
8. Motor vehicle (1) equipped with an opening (2), characterized in that it comprises a management system for said opening (2) according to the preceding claim.