Method for localizing a mobile device relative to a motor vehicle using UWB

Abstract

The invention relates to a method for localizing a mobile device (1) relative to a motor vehicle (2), wherein the motor vehicle (2) has a control arrangement (3) with an anchor arrangement, the anchor arrangement having at least two anchors (4) that receive signals from the mobile device (1), wherein the control arrangement (3) calculates a raw signal (5), in particular a channel impulse response, for each of the anchors (4) at a given time, wherein the raw signals (5) contain one or more signal segments (6) corresponding to a distance between the respective anchor (4) and the transmitter, and wherein the control arrangement (3) determines the position of the mobile device (1) at that time from the signal segments (6) of the raw signals (5) of the individual anchors (4).The control arrangement (3) determines the position of the mobile device (1) by identifying a primary signal segment (7) for each anchor (4) and determining the position of the mobile device (1) from the distances associated with the primary signal segments (7). It is proposed that the control arrangement (3) determines the primary signal segments (7) by combining, for an anchor (4), the raw signal (5) of the anchor (4) at that time and another raw signal (5) of one of the anchors (4) and / or information derived from the other raw signal (5) of one of the anchors (4) to determine the primary signal segment (7) of the raw signal (5) of the anchor (4).

Description

[0001] The present invention relates to a method for locating a mobile device relative to a motor vehicle using UWB according to the preamble of claim 1 and to a control arrangement configured to carry out the method according to claim 5.

[0002] In some vehicles, the localization of motor vehicle operators is carried out using multiple UWB (ultra-wideband) anchors distributed throughout the vehicle, usually located at the front and rear. Based on the localization, support functions for the user can be activated and triggered. During localization, primary signal sections, such as signal sections corresponding to power maxima, are determined for multiple anchors. These are assigned a distance, for example, based on a corresponding propagation time.

[0003] The ability of UWB-based localization systems to accurately determine an operator's position is compromised by the phenomenon of multipath propagation. When a signal is emitted from a transmitter, it can be reflected by various surfaces in the environment before reaching the receiver. As a result, a UWB anchor can receive multiple signals with different propagation times and amplitude levels, which becomes apparent in the channel impulse response (CIR) as multiple amplitude or power peaks.

[0004] In particular, if the direct path between the transmitter and the UWB anchor is obscured by an obstacle, the reflected path may have higher power than the direct path. This can lead to problems when using conventional methods such as received power thresholds or power maxima, as these methods are based on the assumption that the signal with the highest power corresponds to the direct path. Shadowing can occur, for example, if the transmitter is carried in the operator's back pocket. In underground parking garages, for example, the reflected path can then regularly have higher power.

[0005] To deal with the resulting misestimations during the user's approach, motion models are used, for example. Based on assumptions for typical user movements (including the path of the motion vector and speed), the estimated positions are checked for plausibility. If estimates result that do not follow a typical user movement, the corresponding estimation results are disregarded or interpolated based on the underlying model.

[0006] The invention is based on the problem of designing and developing the known methods in such a way that misestimations are reduced.

[0007] The above problem is solved by the features of the characterising part of claim 1.

[0008] The fundamental consideration is that implausible distance data from an anchor can be discarded, but the local maximum of the direct path is still contained in the raw data, especially the channel impulse response, and can be extracted. In the simplest case, the second-highest maximum can be used for an implausible distance. Plausibility can be verified in several ways.

[0009] In detail, it is proposed that the control arrangement determines the primary signal sections by the control arrangement combining for an anchor, in particular for each anchor, the raw signal of the anchor at the time and a further raw signal of one of the anchors and / or information derived from the further raw signal of one of the anchors in order to determine the primary signal section of the raw signal of the anchor.

[0010] According to claim 2, it is proposed that data from at least two further anchors are used to improve the estimation of an anchor.

[0011] In a preferred embodiment according to claim 3, several signal sections are determined and the data of the further anchor are used to decide which of the signal sections is the primary signal section.

[0012] For example, the signal section with the highest power may be discarded if the motion model indicates that the operator is unlikely to be at a position within the distance associated with the signal section.

[0013] It is also possible to weight the raw signal and subsequently determine the signal section that meets a maximum criterion (claim 4). For example, a window can be defined around a previous distance, outside of which the energy in the raw signal is weighted with a factor that decreases with increasing distance.

[0014] According to a further teaching according to claim 5, which has independent significance, a control arrangement is claimed to be set up for carrying out the proposed method.

[0015] Reference may be made to all statements relating to the proposed procedure.

[0016] The invention will be explained in more detail below with reference to a drawing which merely represents an exemplary embodiment. Fig. 1 a vehicle with anchors and a mobile device for determining the user’s position, Fig. 2 exemplary channel impulse responses (CIR) for three anchors on the vehicle and Fig. 3 an exemplary overlay of the CIR of the three anchors on the vehicle.

[0017] The preferred embodiment illustrated in the figures relates to a method for locating a mobile device 1 relative to a motor vehicle 2 using UWB. The mobile device 1 can be a radio key or the like. Such mobile devices 1 are now widely used to locate and authenticate the operator B of a motor vehicle 2.

[0018] The motor vehicle 2 has a control arrangement 3 with an armature arrangement, wherein the armature arrangement has at least two armatures 4 that receive signals from the mobile device 1. The control arrangement 3 can have one or more control units, which can be integrated into an armature 4 as a UWB control unit or communicate with one or more armatures 4. The proposed method is implemented by the control arrangement 3 and in particular the control unit and the armatures 4.

[0019] Preferably, the armatures 4 are configured for communication in the frequency range from 3.1 GHz to 10.6 GHz. The UWB signals used by the armatures 4 are preferably pulses with a bandwidth of at least 500 MHz, more preferably with a duration in the order of nanoseconds.

[0020] An armature 4 preferably has at least one antenna for receiving measurement signals and / or transmitting UWB signals. A UWB control unit is preferably connected to the antenna for evaluating the measurement signals and / or generating the UWB signals. The UWB control unit can be functionally limited and, for example, implemented solely in hardware. The UWB control unit preferably has at least one microcontroller. The measurement signals can be UWB signals received by the mobile device 1, i.e., part of a communication, in particular bidirectional communication, and / or measurement signals from reflection measurements.

[0021] The control arrangement 3 calculates a raw signal 5, in particular a channel impulse response, for each of the armatures 4 at a given time. The term "calculate" is to be understood broadly and also includes measuring and digitizing. The raw signal 5 is preferably calculated by a UWB control unit per armature 4. This saves transmission capacity. The control arrangement 3 preferably calculates such a raw signal 5 regularly, for example, 10 times per second.

[0022] In the raw signals 5, if a mobile device 1 is present, one or more signal sections 6 are inherently present, which are assigned to a distance between the respective anchor 4 and the transmitter.

[0023] The control arrangement 3 determines a position of the mobile device 1 at the time from the signal sections 6 of the raw signals 5 of the individual anchors 4. The control arrangement 3 determines a primary signal section 7 for each anchor 4 to determine the position of the mobile device 1 and determines the position of the mobile device 1 from the distances assigned to the primary signal sections 7. This determination also preferably takes place regularly, in particular at each time at which a measurement is taken. Thus, a position of the mobile device 1 and thus indirectly of the operator B is assigned to each time.

[0024] Fig. 1 shows an exemplary motor vehicle 2 with six anchors 4 and an operator B with a mobile device 1. An obstacle H is located between the mobile device 1 and one of the anchors 4. The operator B can also represent such an obstacle H if the mobile device 1 is, for example, in a back trouser pocket. Thus, if a direct path DP between the mobile device 1 and one of the anchors 4 is blocked by the obstacle H, it can happen that a signal received via a reflection path RP at the anchor 4 has a higher signal power. For example, in an underground car park, this risk is comparatively high because good reflection options and various obstacles H are present.

[0025] Fig. Figure 2 shows three exemplary channel impulse responses for three anchors 4. These each have, for example, two signal sections 6 with recognizable maxima 8, i.e., two possible distances at which the mobile device 1 can be located. For one of the anchors 4, the higher maximum 8 is now, for example, a maximum 8 of a reflection path RP ( Fig. 2 b)). Fig. Figure 3 then shows that, when projecting the channel impulse responses through known positions of the anchors 4, several possible positions 9 of the mobile device 1 result, but that no intersection point exists between the distances assigned to all three power maxima 8. The localization of the mobile device 1 is therefore ambiguous.

[0026] It is therefore proposed that the control arrangement 3 determines the primary signal sections 7 by combining the raw signal 5 of the armature 4 at the time and a further raw signal 5 of one of the armatures 4 and / or information derived from the further raw signal 5 of one of the armatures 4 for an armature 4, in particular for each armature 4, in order to determine the primary signal section 7 of the raw signal 5 of the armature 4. It is Fig. 3 that there is an intersection point of the maxima 8 of two anchors 4 and a second, lower maximum 8 of the third anchor 4, which corresponds to the position of the operator B. At this intersection point, the Fig. 3 schematically shown spatially projected sum of the three raw signals 5 has a maximum amplitude of 8.

[0027] Thus, in general, the control arrangement 3 determines the primary signal sections 7 according to a criterion that, when applied to the raw signal 5, would result in the selection of a signal section 6 as the primary signal section 7, but that, based on the combination of the raw signal 5 with the further raw signal 5 or the derived information, the control arrangement 3 selects a different signal section 6 as the primary signal section 7. The criterion can be exceeding a threshold value of the amplitude in a predefined period of time or finding a maximum 8 of the raw signal 5 in a predefined period of time.

[0028] Out of Fig. 1 that the control arrangement 3 here and preferably has at least three, preferably at least four, anchors 4, which are preferably used for localization within the scope of the method. Then, for the anchor 4, in particular for each anchor 4, the control arrangement 3 combines the raw signal 5 of the anchor 4 at the time and further raw signals 5, in particular belonging to the time, of the other anchors 4 and / or information derived from the further raw signals 5 of at least two, preferably at least three, of the other anchors 4, in order to determine the primary signal section 7 of the raw signal 5 of the anchor 4.

[0029] As already indicated, it can be provided that the control arrangement 3 determines several signal sections 6 with several associated distances from the raw signal 5 and determines the primary signal section 7 by combining the signal sections 6 with the derived information.

[0030] One possibility for determining the primary signal segment 7 is to derive the derived information from a motion model. Using the motion model, probable positions of operator B can be determined, which in turn can be assigned probable distances to the respective anchors 4. Signal segments 6 that correspond to improbable distances can be discarded.

[0031] The control arrangement 3 can perform a central calculation or a decentralized calculation to determine the position of the mobile device 1.

[0032] During the central calculation, the control arrangement 3 can transmit the raw signals 5 detected by the anchors 4 to a central control unit. The central control unit can then calculate the most probable individual distances for each anchor 4 and use these to determine the position of the mobile device 1. The control arrangement 3 can take a motion model into account to increase the plausibility of the localization. It is also conceivable for the UWB control units of the anchors 4 to quantize the raw signals 5 to reduce the data volume. For example, signal sections 6 with a power below a predefined threshold can be discarded at the UWB control unit of the anchor 4.

[0033] During decentralized calculation, the control arrangement 3 can transmit an estimated previous position vector to the UWB control units of the anchors 4. The UWB control units can then calculate the new most probable distances for each anchor 4 and transmit them to the central control unit. The central control unit can then determine the position of the mobile device 1 from the received distances. Here, too, a motion model can be applied for further plausibility check.

[0034] An initial value for the motion model can be determined by a BLE-based distance determination, for example using RSSI, channel sounding or high-accuracy distance measurement (HADM).

[0035] Alternatively or additionally, it is conceivable that the control arrangement 3 spatially calculates the raw signals 5 based on a known distance between the anchors 4 and preferably determines the localization of the mobile device 1 from the calculated raw signals 5. Thus, based on the Fig. 3 demonstrates that the raw signals 5 can also be spatially superimposed starting from the respective anchor 4, and subsequently, a total amplitude maximum can be determined as the position of the mobile device 1. A model of the motor vehicle 2 and / or antenna directional characteristics can also be taken into account.

[0036] Overall, it can be said that the control arrangement 3 preferably weights the raw signal 5 with the derived information, and further preferably, the control arrangement 3 determines the primary signal section 7 as the maximum signal section 6 with respect to a predefined maximum criterion. The maximum criterion can be an energy in a predetermined time period.

[0037] According to a further doctrine of independent significance, it is proposed to establish a tax order 3 to implement the proposed procedure.

Claims

[1] Method for locating a mobile device (1) relative to a motor vehicle (2) by means of UWB, wherein the motor vehicle (2) has a control arrangement (3) with an anchor arrangement, wherein the anchor arrangement has at least two anchors (4) which receive signals from the mobile device (1), wherein the control arrangement (3) calculates a raw signal (5), in particular a channel impulse response, for each of the anchors (4) at a time, wherein one or more signal sections (6) associated with a distance between the respective anchor (4) and the transmitter are present in the raw signals (5), wherein the control arrangement (3) determines a position of the mobile device (1) at the time from the signal sections (6) of the raw signals (5) of the individual anchors (4),in that the control arrangement (3) for determining the position of the mobile device (1) determines a primary signal section (7) for each anchor (4) and determines the position of the mobile device (1) from the distances assigned to the primary signal sections (7), , characterized by that the control arrangement (3) determines the primary signal sections (7) by the control arrangement (3) combining, for an armature (4), in particular for each armature (4), the raw signal (5) of the armature (4) at the time and a further raw signal (5) of one of the armatures (4) and / or information derived from the further raw signal (5) of one of the armatures (4), in order to determine the primary signal section (7) of the raw signal (5) of the armature (4). [2] Method according to claim 1, characterized bythat the control arrangement (3) has at least three, preferably at least four, armatures (4), and that the control arrangement (3) for the armature (4), in particular for each armature (4), combines the raw signal (5) of the armature (4) at the time and further raw signals (5) of the other armatures (4), in particular those belonging to the time, and / or information derived from the further raw signals (5) of at least two, preferably at least three, of the other armatures (4), in order to determine the primary signal section (7) of the raw signal (5) of the armature (4). [3] Method according to claim 1 or 2, characterized by that the control arrangement (3) determines a plurality of signal sections (6) with a plurality of associated distances from the raw signal (5) and determines the primary signal section (7) by combining the signal sections (6) with the derived information, and / or that the derived information is derived from a movement model. [4] Method according to one of the preceding claims, characterized by that the control arrangement (3) weights the raw signal (5) with the derived information, preferably that the control arrangement (3) determines the primary signal section (7) as the maximum signal section (6) with regard to a predefined maximum criterion, further preferably that the maximum criterion is an energy in a predetermined time period. [5] Control arrangement arranged to carry out the method according to one of the preceding claims.

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