Method for tracking a position of a target
The method uses pulsed radio frequency signals and double sampling to track vehicle targets without user-worn devices, addressing the complexity and cost of current UWB systems, enhancing vehicle safety and accessibility.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- SCHAEFFLER TECHNOLOGIES AG & CO KG
- Filing Date
- 2025-12-17
- Publication Date
- 2026-06-25
AI Technical Summary
Current UWB radar systems for vehicle tracking require users to wear devices, imposing an additional burden and are complex and expensive to implement.
A method using pulsed radio frequency signals emitted by transceivers to track targets relative to a vehicle without requiring the user to wear a device, employing double sampling and standard deviation analysis to distinguish target presence from noise, enabling precise localization through triangulation.
Enables accurate and efficient tracking of user movements around vehicles without user-worn devices, improving vehicle safety and accessibility by reducing complexity and cost.
Smart Images
Figure EP2025087735_25062026_PF_FP_ABST
Abstract
Description
Description Method for tracking the position of a target technical field
[0001] This disclosure falls within the domain of processes 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 wide-bandwidth radio frequency signals. A wide-bandwidth radio frequency signal is an electromagnetic signal with a carrier frequency ranging, for example, from 3 kHz to 300 GHz, but most often from 5 GHz to 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 areas such as motion detection, the localization of people and objects, as well as in vehicle security and access systems.
[0005] Applications in this area 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 goals 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 burden on the user. Furthermore, current location methods based on measuring the time of flight between UWB devices can be complex and expensive to implement.
[0009] It is known from prior art that the location of users around vehicles is achieved 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 UWB devices worn by users and UWB anchors integrated into vehicles to determine the users' position.
[0011] However, this approach requires the user to wear a UWB device, which poses an additional constraint.
[0012] Therefore, there is a need for a system to locate and track users' trajectories 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, this 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: (a) emit, using at least one first and one second transceiver, a pulsed radio frequency signal called the forward signal, intended to be reflected at least partially by said target, (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, (c) demodulate the return signal and extract signals l(t) and Q(t) defining two components in phase and in quadrature phase respectively at a time t using a mixer, (d) obtain sampled data l(ti,k) and Q(ti,k) corresponding to a time sampling of the signals l(t) and Q(t), ti.k being a short-time sampling instant associated with a short sampling period, and the sampled data l(ti,k) and Q(ti,k) being grouped into vectors l(ti) and Q(ti), ti being a long-time sampling instant associated with a long sampling period, (e) perform steps (f) to (h) for each transceiver, (f) For each long time ti data and each short time ti.k_data, calculate a standard deviation oi,k_data of one of the following l(ti.k_data), Q(ti,k_data) and |CIR(ti,k_data)| corresponding to a modulus of l(ti,k_data) and Q(ti.k_data), (g) compare oi,k_data with a threshold standard deviation Oi, k _seuii corresponding so as to assign to each short time ti,k_data a number Ni, k_data satisfying: If Oi,k_data > Oi,k_threshold, Ni,k_data = 1 J and If Oi,k_data — Oi,k_threshold, Ni,k_data = 0, (h) search, for at least a long time ti_data_min, the smallest short time ti,k_data_min corresponding to a number Ni, k_data satisfying Ni,k_data = 1; (i) deduce the position of the target at each of said at least a long time ti_data_min.
[0014] Step (d) corresponds to double sampling: a first rapid sampling with short-time sampling instants ti.k, preferably at a sampling frequency on the order of 1 GHz, the frequency of the first fast sampling corresponding to the sampling period by the analog-to-digital converter of a chip of said at least one first and one second transceiver; A second slow sampling with long-time sampling intervals (ti) 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.
[0015] l(t) corresponds to a signal relative to an in-phase component of the return signal, resulting from mixing the return signal with a signal in phase and at the frequency of the transmitted signal (forward signal). Q(t) corresponds to a quadrature-phase component of the return signal, resulting from mixing the return signal with a quadrature-phase signal at the frequency of the transmitted signal; the signals l(t) and Q(t) define the two components of a demodulated return signal.
[0016] It is important to understand that l(t) and Q(t) correspond to the values of the in-phase and quadrature components, respectively, at time ti. It is also important to understand that l(ti,k) and Q(ti,k) correspond to the values of the in-phase and quadrature components, respectively, at time ti,k. This is, of course, valid for any other given instant or time.
[0017] CIR is the English acronym for "Channel Impulse Response". In this document, |CIR(ti,k_data)| corresponds to the amplitude of the demodulated return signal, and is equal to the square root of l 2 (ti)+Q 2 (ti): |c / 7?(t i fc(tata )| = l 2 (ti) + Q 2(tj) ■ H is to be understood as |CIR(ti,k_data)| corresponding to the value of the modulus |CIR(t)| for a time t=ti,k_data. This is of course valid for any other given instant or time.
[0018] oi,k_data corresponds to a measure of the dispersion or variability of one among l(ti,k_data), Q(ti,k_data) and |CIR(ti,k_data)|. It indicates how far the individual values of one among l(ti,k_data), Q(ti,k_data) and |CIR(ti,k_data)| deviate on average from the mean of one among l(ti,k_data), Q(ti,k_data) and |CIR(ti, k data)|.
[0019] The grouping of the sampled data l(ti,k) and Q(ti,k) into vectors l(t) and Q(t) corresponds to a folding of the time axis. In other words, each vector l(t) and Q(t) contains the data associated with one of the pulse trains of the emitted signal.
[0020] From the point of view of each vector l(t) and Q(t), the second slow sampling is similar to a spatial sampling: the first value corresponds to a zero distance of the target from the receiver, transceiver or 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, transceiver or vehicle; and so on.
[0021] 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 process makes it possible to extract precise time information on the movement of the target.
[0022] Long time intervals (ti) 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.
[0023] A "tap" can, for example, represent a distance of 15 cm.
[0024] The tracking method offers the advantage of not requiring a transmit-receive device, such as a badge, that the target must wear to carry out the tracking.
[0025] Indeed, the process is based, for a short time ti,k_data of each transmitter-receiver, on the comparison of the standard deviation oi,k_data with respect to the threshold standard deviation Oi, k _seuii. Therefore, only data from the first and second transceivers are needed here.
[0026] The condition Oi,k_data Oj,k_threshold corresponds to a situation in which the chosen values (|CIR(ti,k_data)|, l(ti,k_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 t data and short time ti,k_data. This allows us to distinguish false positives corresponding, for example, to accidental or unintentional movements.
[0027] This standard deviation Oi, k _seuii corresponds to a standard deviation of inactivity of the target.
[0028] Comparing standard deviations ensures consistent monitoring of the target and avoids potential false positives which are discriminated at step (g), the latter having a number Ni,k_data = 0.
[0029] Step (i) is equivalent to the search at long time t data for the short time ti,k_data_min for which Ni,k_data = 1, i.e. the ti,k_data_min for which there is presence of the target, for each transmitter-receiver.
[0030] This short time ti,k_data_min corresponds to the intersection between the signals emitted from the first and second transmitter-receivers for which there is presence of the target for both transmitter-receivers.
[0031] Step (i) corresponds to the deduction from the ti,k_data_min for each at least one long time corresponding ti data and for each transmitter-receiver of the trajectory of the position of the target.
[0032] The motor vehicle can be in reference frame Rv, the reference frame Rv having its origin at a point on the motor vehicle, the forward signal propagating uniformly in all directions, step (i) comprising determining an intersection of the forward signals from the first and second transmitters / receivers at at least every long time ti_data_min, said intersection corresponding to the intersection of a first and second circle whose center is the position of the first and second transmitters / receivers respectively and whose radius is the short time ti,k_data_min corresponding, in an analysis plane of the reference frame Rv parallel to a plane on which the wheels of the motor vehicle rest.
[0033] 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).
[0034] Determining the intersection (at short time intervals ti, k_data_min) of the forward signals from the first and second transceivers at each long time interval t_data allows for precise target localization using a triangulation method. This approach improves localization accuracy by combining information from the first and second transceivers to determine the target's exact position.
[0035] The intersection of the circles of radius ti,k_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 us to follow the trajectory of the target in a horizontal plane (the analysis plane), the forward signals being equivalent to circles in said plane.
[0036] The analysis plan can be a plan located opposite the part of the motor vehicle and including said part of the motor vehicle.
[0037] By limiting the analysis plan to the part of the motor vehicle and including said part of the vehicle, the process makes it possible to concentrate the detection and tracking of the target in a specific area of interest.
[0038] Indeed, this allows us to discriminate the intersection (among the two possible intersections) of the circles of radius ti,k_data_min of the first and second transmitters-receivers which is not relevant, namely the one which is not opposite the part of the motor vehicle.
[0039] Oi, k _seuii can be between 25% and 35%, preferably 30%, of an empty standard deviation Oi, k _empty of the short time ti,k_data.
[0040] By setting this interval, the process 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.
[0041] This document may also relate to a method for controlling an opening of a motor vehicle, including the tracking method according to the aforementioned type, said control method further comprising: (j) determine whether the target's position at each of said at least a long time ti_data_min corresponds to a voluntary movement of the target, (k) where applicable, 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 on the opening.
[0042] This document may also relate to a computer intended to be installed 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.
[0043] According to a particular feature, the calculator also includes a mixer. The mixer is capable of mixing the return signal with a signal in phase and at the frequency of the transmitted signal to obtain l(t), as well as mixing the return signal with a signal in quadrature phase and at the frequency of the transmitted signal to obtain Q(t). In other words, the mixer is capable of extracting l(t) and Q(t) during step a).
[0044] According to a particular characteristic, the mixer is separate from the calculator.
[0045] This document may also relate to a management system for an opening of a motor vehicle intended to be installed in said motor vehicle, characterized in that the system comprises: - at least one first and one second transceiver designed to transmit the signal and receive the return signal, and - an electronic management module comprising a computer of the aforementioned type.
[0046] According to a particular characteristic, the management system of an opening also includes the mixer.
[0047] 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
[0048] Other features, details, and advantages will become apparent upon reading the detailed description below and analyzing the attached drawings, on which:
[0049] [Fig. 1] is a schematic view of a motor vehicle according to an embodiment of this document,
[0050] [Fig. 2] is a block diagram of a method for controlling an opening of a motor vehicle according to an embodiment of this document,
[0051] [Fig. 3] is a horizontal cross-sectional view of a rear bumper of the motor vehicle in Figure 1, with an example of a straight trajectory of a target,
[0052] [Fig. 4] is a graph of a return signal resulting from the reflection of the target along the trajectory shown in Figure 3,
[0053] [Fig. 5] illustrates a table established according to the process of managing the opening of a door on a motor vehicle in Figure 2, and
[0054] [Fig. 6] is a view along a horizontal cross-section plane of a rear bumper of the motor vehicle in Figure 1, with a trajectory of a target deduced from Figure 5. Description of the implementation methods
[0055] Figure 1 schematically represents a motor vehicle 1 comprising a movable opening 2, capable of being controlled by a management system for said opening 2.
[0056] In the illustrated example, the opening 2 is the rear trunk of the motor vehicle 1.
[0057] The management system in question 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.
[0058] The computer includes a processor, a mixer and at least one memory, and is configured to implement each of the steps of a process for managing the opening of the opening 2.
[0059] The computer is capable of generating an output signal to control opening 2.
[0060] The method for controlling the opening 2 according to an embodiment of this document is described below with reference to Figure 2.
[0061] 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).
[0062] 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 by said target.
[0063] An example of this transmission of the forward signal is shown in Figure 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.
[0064] In operation, each transceiver 12, 14 emits a uniform forward signal in all directions (equivalent to a circular signal along the horizontal plane).
[0065] 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).
[0066] Here, a "tap" corresponds to a distance of 200 mm.
[0067] During an EB step, a radio frequency signal called the return signal is received using said at least one first and one second transceiver 12,14, resulting from the reflection of the forward signal on said target.
[0068] During an EC step, the return signal is demodulated and signals l(t) and Q(t) are extracted, defining two components in phase and in quadrature of phase respectively at a time t using the mixer.
[0069] During an ED step, we obtain sampled data l(ti,k) and Q(ti,k) corresponding to a time sampling of the signals l(t) and Q(t), ti,k being a sampling instant called short time, associated with a short sampling period, and the sampled data l(ti,k) and Q(ti,k) being grouped into vectors l(ti) and Q(ti), t being a sampling instant called long time, associated with a long sampling period.
[0070] During an EE step, for each transmitter-receiver 12, 14, the steps EF to EH are carried out.
[0071] During an EF step, for each long time ti_data and each short time ti,k_data, we calculate a standard deviation oi,k_data of one of the following l(ti.k_data), Q(ti,k_data) and |CIR(ti,k_data)| corresponding to a modulus of l(ti,k_data) and Q(ti,k_data).
[0072] During an EG step, oi,k_data is compared with a threshold standard deviation Oi, k _seuii corresponding so as to assign to each short time ti,k_data a number Ni, k_data satisfying: If Oi,k_data > Oi,k_threshold, Ni,k_data = 1 J and If Oi,k_data — Oi,k_threshold, Ni,k_data = 0.
[0073] In this way, for each long time ti data, only short times ti,k_data are considered relevant with regard to the presence of the target, which translates to Ni,k_data = 1.
[0074] As an example, the path of the target from position M1 to position M2 (see figure 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 presenting Ni, k _data = 1.
[0075] Thus, the EG step makes it possible to discriminate between irrelevant moments and taps during which the target is not present.
[0076] If we take a case of an arbitrary trajectory of a target, the EG step allows us to establish a table as illustrated in figure 5 with the different long times t data (here t0, t1, t2, t3, t4, t5, t6, t7, t8, t9, t10, t11, t12) in rows and the different taps ti,k_data (here TAP1, TAP2, TAP3, TAP4, TAP5, TAP6, TAP7, TAP8, TAP9, TAP10) in columns.
[0077] The binary values shown in each box correspond to the associated Ni,k_data = 1.
[0078] During an EH step, we search, for at least a long time t data, for the smallest short time ti,k_data_min corresponding to a number Ni, k_data satisfying Ni,k_data = 1.
[0079] Reference is now made to Figure 5, in which step EH corresponds to the reading, line by line, of the smallest tap for which Ni,k_data = 1.
[0080] For example, for the long time t1: For transceiver 12, the smallest tap (ti,k_data_min) is TAP3; and for transceiver 14, the smallest tap (ti,k_data_min) is TAP9.
[0081] As illustrated in Figure 6, the first target tracking position is position P1, which is the intersection between circle TAP4 of transceiver 12 and circle TAP10 of transceiver 14.
[0082] Regarding 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 TAP8.
[0083] As illustrated in Figure 6, the second target tracking position is position P2, which is the intersection between circle TAP3 of transceiver 12 and circle TAP9 of transceiver 14, and so on.
[0084] 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.
[0085] The analysis plan here is the PA plan which includes the rear end of the rear bumper 4 as well as the area opposite said rear bumper 4.
[0086] During a step El, we thus deduce the position of the target 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 transmitters-receivers at each of said at least one long time ti_data_min, said intersection corresponding to the intersection of a first and second circles having as center the position of the first and second transmitters-receivers respectively and as radius the corresponding short time ti,k_data_min, in an analysis plane of the reference frame Rv parallel to a plane on which the wheels of the motor vehicle rest.
[0087] The complete trajectory of the target is illustrated in Figure 6 with the remaining positions P3, P4, P5, P6, P7, P8, P9, P10, P11, P12.
[0088] During an EJ step, we determine if 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.
[0089] During an EK step, we 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.
Claims
Demands
1. A 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) emit (EA), using at least one first and one 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 signals l(t) and Q(t) defining two components in phase and in quadrature phase respectively at a time t using a mixer, (d) obtain (ED) sampled data l(ti,k) and Q(ti,k) corresponding to a time sampling of the signals l(t) and Q(t), ti.k being a short-time sampling instant associated with a short sampling period, and the sampled data l(ti,k) and Q(ti,k) being grouped into vectors l(t) and Q(t), ti being a long-time sampling instant associated with a long sampling period, (e) perform (EE) for each transceiver steps (f) to (h), (f) for each long time ti_data and each short time ti.k_data, calculate (EF) a standard deviation oi,k_data of one of l(ti.k_data), Q(ti,k_data) and |CIR(ti,k_data)| corresponding to a modulus of l(ti,k_data) and Q(ti,k_data), (g) compare (EG) oi,k_dat a with a threshold standard deviation Oi, k _seuii corresponding so as to assign to each short time ti,k_data a number Ni, k_data satisfying: If Oi,k_data > Oi,k_threshold, Ni,k_data= 1 J and If Oi,k_data — Oi,k_threshold, Ni,k_data = 0, (h) search (EH), for at least a long time ti_data_min, the smallest short time ti,k_data_min corresponding to a number Ni, k_data satisfying Ni,k_data = 1; (i) deduce (El) the position (P1, P2, P3, P4, P5, P6, P7, P8, P9, P10, P11, P12) of the target at each of said at least a 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 on 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 at least every 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 transmitter-receivers respectively and for radius the corresponding short time ti,k_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 Oj,k_seuii is between 25% and 35%, preferably 30%, of a typical empty error Oi,k_vide of the short time ti,k_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: (j) Determine (EJ) whether the target's position at each of said at least a long time ti_data_min corresponds to a voluntary movement of the target, (k) Where appropriate, control (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. 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 further comprising a mixer and being characterized in that it is configured for the implementation of each of the steps of a control method according to the preceding claim or a tracking method 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 emitted signal and 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.