Handheld device for controlling a motor vehicle

Abstract

A method (300) for locating a handheld device (110) relative to a motor vehicle (105) comprises the steps of negotiating a time interval between the handheld device (110) and the motor vehicle (105); transmitting a series of wireless pulses between the motor vehicle (105) and the handheld device (110), the wireless pulses being emitted with a time interval offset; and determining the position of the handheld device (110) relative to the motor vehicle (105) based on the time intervals between the reception times of the wireless pulses at the handheld device (110). The time interval is negotiated depending on the power output of a power source (155) of the handheld device (110).

Description

The present invention relates to the control of a motor vehicle. In particular, the invention relates to the control of the motor vehicle by means of a hand-held device.A motor vehicle comprises a control device which is configured to control a safety function of the motor vehicle, for example the opening or closing of the motor vehicle or the activation or deactivation of a immobilizer. For control purposes, a wirelessly communicating hand-held device can be used, which can be embodied, for example, integrated into a mechanical key or in the manner of a key fob. When the hand-held device is actuated, messages can be exchanged between the hand-held device and the motor vehicle in order to carry out the safety function. A hand-held device that is dedicated to communication with the motor vehicle usually uses the radio technology LF (125 kHz) or HF (434 MHz).A mobile device (smartphone) can also be used for wirelessly controlling the safety function of the motor vehicle. Radio technologies used herein include Bluetooth Low Energy (BLE) at a frequency of about 2.4 GHz and Ultra-Wide Band (UWB) at a frequency range of about 6 to about 10 GHz. Preferably, both mentioned radio technologies are used in an interlocked manner in order, on the one hand, to handle a secure communication and, on the other hand, to determine a position of the mobile device with respect to the motor vehicle. Significantly more extensive safety concepts are possible here than with a dedicated hand-held device. The controller may be implemented, for example, according to a standard known as a digital car key disclosed by the car connectivity consortium.In order to be able to use the motor vehicle even without a mobile telephone, a hand-held device is to be equipped with the technology of a mobile device. In order to be able to make the hand-held device small and light, an energy source of the hand-held device is dimensioned as small as possible. In a known method of locating the hand-held device relative to the motor vehicle by means of UWB, a heavy load on the energy source can occur during the reception of a series of wireless pulses. The energy source can comprise, for example, a button cell which should be loaded only with a low current of approximately 10 to 15 mA, wherein a significantly higher current of, for example, approximately 130 mA can be absorbed briefly during the reception.A pulse-like energy absorption can be smoothed by using a capacitor. If the button cell is in good condition, receiving the sequence of wireless pulses may be easy. However, if the button cell operates under suboptimal conditions, for example because it is already partially discharged or low temperatures prevail, the electrical voltage provided for the hand-held device may briefly drop below a predetermined threshold value during the reception, so that the processing may be disturbed.An object underlying the present invention is to provide an improved technique for communication between a hand-held device and a motor vehicle. The invention achieves this object by means of the subject matter of the independent claims.According to a first aspect of the present invention, a method for locating a hand-held device in relation to a motor vehicle comprises steps of negotiated a time interval between the hand-held device and the motor vehicle; transmitted a series of wireless pulses from the motor vehicle to the hand-held device; wherein the wireless pulses are transmitted offset from different positions on the motor vehicle by the time interval; and determining a position of the hand-held device in relation to the motor vehicle on the basis of time intervals between reception times of the wireless pulses on the hand-held device. In this case, the time interval is negotiated as a function of a capability of an energy source of the hand-held device.It is thus possible to prevent the energy source from being loaded so much during the reception of the wireless pulses that the function of a further component of the hand-held device is impaired. Functional reliability of the hand-held device can thus be increased. The hand-held device can be operated safely in an improved manner even under unfavourable conditions.The time interval is preferably extended with decreasing power capability of the energy source. If the power capability of the energy source is high, the time interval can be selected to be short and be, for example, approximately 1.333 ms. If the power source capability is only moderate, the time interval may be increased to a mean length of, for example, about 2.667 ms. If the power source is at the lower end of a usable range, the time interval may be increased to a long time of, for example, 4.00 ms. Usually, during a localization, as many pulses are transmitted in the series as there are transmitting devices at different positions of the motor vehicle. The number of transmitting devices is usually adjustable, so that even with a long time interval no noticeable delay compared to a short time interval can be detected by a person operating the hand-held device.In one embodiment, the energy source provides an electrical voltage, wherein the performance is determined as a function of the electrical voltage provided. In other words, a voltage of the energy source can be used as an indicator of a state of charge (SoC). The electrical voltage is preferably determined as open circuit voltage if the energy source is not significantly loaded by a load. In particular, if the energy source comprises an electrochemical energy store and is designed as a rechargeable battery or battery, the voltage can indicate the state of charge to a good approximation. The higher the state of charge, the greater the power capability of the energy source may be.In an embodiment in which the energy source provides an electrical voltage, the performance may be determined depending on an internal electrical resistance of the energy source. The lower the internal electric resistance, the greater the performance may be. The internal resistance can be determined by connecting an electrical load to the energy source and determining a current flowing through the load as a function of a voltage present at it. The consumer can in particular comprise a transmitter or a receiver of the hand-held device.If the energy source comprises an electrochemical energy store, the performance can be determined as a function of a temperature in the region of the energy store. The lower the temperature, the lower the performance may be. It can be considered that a battery and an accumulator may be degraded in performance when used under cold temperatures. The temperature in the region of the energy source can easily be determined, for example, by means of a temperature-dependent component, for example a diode.If the energy source comprises an energy store, the power capability of the energy store can be determined on the basis of past energy extraction from the energy store. The energy store is not regenerative, so that only a predetermined amount of energy can be taken from it. For energy which can still be drawn from the energy store, a model can be formed. The more frequently energy has been taken from the energy store or the greater an energy removal, the lower an energy remaining in the energy store can be. In other words, the performance of the energy store can drop the more energy has already been removed from it. Good models of this type are known in particular for accumulators and batteries.A hand-held device for communication with a motor vehicle comprises a wireless transceiver; an energy source; and a processing device. The processing device is configured to negotiate a time interval with a motor vehicle; to receive a series of wireless pulses that are transmitted offset from different positions on the motor vehicle by the time interval; and to determine a position of the hand-held device with respect to the motor vehicle on the basis of time intervals between reception times of the wireless pulses on the hand-held device. In this case, the processing device is configured to negotiate the time interval as a function of a capacity of the energy source of the hand-held device.The technique presented herein can be applied both in the transmission of pulses from the motor vehicle to the hand-held device and in the opposite direction. A transceiver includes a transmitter and a receiver. If only the direction from the hand-held device to the motor vehicle is to be covered, then only one transmitter can be provided instead of the transceiver. If only the transmission from the motor vehicle to the hand-held device is to be provided with the proposed technique, then only one receiver can be used in a corresponding manner instead of the transceiver. A transceiver is generally used here; a possible reduction to a transmitter or a receiver is thus implied.The processing device is preferably also configured to determine a current performance of the energy source. A method described herein can be carried out partially or completely by means of the hand-held device and in particular by means of the processing device. For this purpose, the processing device can be designed electronically and can comprise, for example, an integrated circuit, a programmable logic module or a programmable microcomputer. The method can be realized in the form of a configuration or as a computer program product having program code means for the processing device. The configuration or the computer program product can be stored on a computer-readable data carrier. Features or advantages of the method can be transferred to the device or vice versa.In one embodiment, the transceiver is activated only when an arrival of a wireless pulse is expected or a pulse is to be transmitted. An electrical voltage of the power source may be reduced while the transceiver is activated. In order to prevent the electric voltage from decreasing during the transmission or reception of the wireless pulses to such an extent that the function of the processing device is impaired, the time interval can be extended. An energy taken from the power source during transmission or reception of the series of pulses may remain the same by extending the time interval, but the load may be distributed over a longer period of time. A short-term voltage dip of the energy source can thereby be prevented.The energy source preferably comprises a buffer store in order to provide an increased electric current for a short time. The buffer memory can be designed in particular as a capacitor. The capacitor may also help reduce short term loading of the power source. The energy source can thus be loaded uniformly in an improved manner.In one embodiment, the processing device is configured to lengthen the time interval if an electrical voltage of the energy source falls below a predetermined threshold value during an activation of the wireless transceiver. In other words, it may be determined whether the electric voltage of the power source decreases unacceptably during transmission or reception of the series of pulses. If this is the case, the time interval can be extended in order to prevent a strong drop in the electrical voltage again. The time interval may be set again to a short value when the power source is charged or replaced.The hand-held device may comprise a reset generator for putting the processing device into a predetermined state if the electrical voltage falls below the predetermined threshold value. The reset generator can be embodied together with the processing device, for example, as an integrated circuit or as a microcontroller. The use of a reset generator on a digital processing device is customary. The reset generator can be used to detect a state of the undervoltage that is detrimental or disturbing for the operation of the processing device.The hand-held device further preferably comprises a further wireless interface for communication with the motor vehicle. The described wireless transceiver can be part of a first wireless interface, which in particular operates using UWB technology. The further wireless interface can operate, for example, according to the Bluetooth standard, in particular Bluetooth Low Energy (BLE). Both interfaces can be operated according to a predetermined protocol in order to handle communication between the hand-held device and the motor vehicle. The hand-held device preferably implements a protocol that is already known. The protocol can be included in particular by the digital car key.A communication standard implemented by the handheld device may provide a maximum or minimum time interval for communication between the handheld device and the motor vehicle. In one embodiment, such a restriction can be exceeded or undershot in order to realize a technique described herein and to prevent the failure of a localization of the handheld device with respect to the motor vehicle if the energy source of the handheld device is not sufficiently powerful.It is particularly preferred that the hand-held device is configured to control a function of the motor vehicle on the basis of information exchanged with the motor vehicle. In particular, the hand-held device can perform two-sided authentication with the motor vehicle and request a predetermined function of the motor vehicle. The function can comprise, for example, unlocking, opening or releasing a driving function of the motor vehicle. The hand-held device is preferably designed as a dedicated device which cannot serve any purpose other than communication with the motor vehicle. Nevertheless, the hand-held device can operate in a similar manner with respect to the control of the function of the motor vehicle as a mobile device (smartphone), which can additionally carry out further functions.The invention will now be described in more detail with reference to the accompanying drawings, in which: FIG. 1 shows a system; FIG. 2 shows exemplary voltage profiles on a hand-held device; and FIG. 3 shows a flow diagram of a methodillustrated.FIG. 1 shows a system 100 which comprises a motor vehicle 105 and a hand-held device 110. On board the motor vehicle 105, a control device 115 is provided, which is configured to communicate with the handheld device 110 and to control a function of the motor vehicle 105. The function can comprise, in particular, a safety function such as locking or unlocking an access lock. The control device 115 comprises a processing device 120, a plurality of wireless interfaces 125 and a further wireless interface 130. An interface 125 typically includes a transceiver as a combination of a transmitter and a receiver. Transmitter and receiver can also be constructed separately from one another. Strictly speaking, communication on the part of the motor vehicle 105 always takes place by means of the control device 115; for the sake of simplicity, it is also referred to below that the hand-held device 110 communicates with the motor vehicle 105.The interfaces 125 are attached to the motor vehicle 105 at different positions and can each comprise an antenna. Positions of the interfaces 125 shown in FIG. 1 are to be understood as exemplary. Preferably, the interfaces 125 can be used both for transmitting and for receiving UWB signals in a frequency range of approximately 6 to 10 GHz. The further wireless interface 130 may comprise one or more further dedicated antennas. The wireless interface 130 preferably operates by means of BLE technology at a frequency of approximately 2.4 GHz.The hand-held device 110 comprises a processing device 140, at least one wireless interface 145, which preferably operates according to UWB technology, and preferably a further wireless interface 150, which preferably operates according to BLE technology. The wireless interface 145 is preferably configured both for transmitting and for receiving UWB signals. The interface 150 is configured to communicate with the interface 130 of the control device 115 on board the motor vehicle 105.The hand-held device 110 preferably comprises an energy source 155, which is further preferably designed as an energy store 155 and in particular as an electrochemical energy store 155. For example, the energy source 155 may include an accumulator or a battery. Optionally, a buffer memory 160 is provided in order to level a time profile of an energy extraction from the energy source 155. The buffer memory 160 preferably comprises a capacitor and can be decoupled from the energy source 155, for example by means of a diode.A voltage monitor 165 may determine whether a voltage provided by the energy source 155 or a voltage provided to a component of the handheld device 110 falls below a predetermined threshold value. In this case, a signal may be provided to the processing device 140, which in one embodiment comprises a reset signal in order to reset the processing device 140 into a predetermined state, so that the voltage monitoring 165 may also be referred to as a reset generator 165. By providing a reset signal, processing of the processing device 140 can be interrupted or discontinued. The voltage monitoring device 165 can also comprise an analog-to-digital converter, with the aid of which the processing device 140 can actively determine a voltage of the energy source 155 or of the buffer memory 160. A particular voltage may be numerically compared to a predetermined threshold.Not shown in FIG. 1 is a user interface with which a person can activate the hand-held device 110, for example a button or a keypad. By activation, a predetermined communication between the hand-held device 110 and the motor vehicle 105 can be triggered. The communication may comprise mutual authentication, which may be based on asymmetric cryptographic keys. In addition, a distance and / or a direction of the hand-held device 110 with respect to the motor vehicle 105 can be determined.The communication and the determination of the distance or direction can be effected by means of different wireless technologies. The technologies can be used in combination or interleaved with one another in order to enable an orderly sequence of exchanging signals. For example, the communication between the motor vehicle 105 and the handheld device 110 can proceed essentially as follows according to the specifications of the digital car key:BLE transmits information via interfaces 130 and 150 to configure communication via UWB interfaces 125, 145the motor vehicle 105 sets all UWB interfaces 125 to receivethe hand-held device 110 sends a pre-pollingthe hand-held device 110 sends a pollinga first UWB interface 125 sends a response. The hand-held device 110 is in this case on receptionthe further UWB transmission devices 125 transmit a response in each case one after the other. The hand-held device 110 is in this case on receptionThe handset 110 sends a final packetThe handset 110 sends a Final_Data packet.The individual UWB packets are transmitted in a short sequence. Typical configuration is one packet every T_Slot=2.667ms (N_Chap_per_Slot=8). The slot time has been previously negotiated between the handset 110 and the motor vehicle. From the signal transit times, the motor vehicle 105 can determine the distances between the hand-held device 110 and the vehicle anchors, and from this the position.FIG. 2 shows, in a lower region, exemplary voltage profiles at the receiving device 145 and the processing device 140 of a hand-held device 110. A time in seconds is indicated in a horizontal direction and an electric voltage in volts is indicated in a vertical direction. A first plot 205 may result when a power capability of the energy source 155 is high; a second plot 210 is associated with an energy source 155 of medium or low power capability. It should be noted that the curves 205, 210 are shown schematically and qualitatively.Messages are indicated in an upper region, which are exchanged between the hand-held device 110 and a motor vehicle 105. A message is represented by an arrow which runs in the transmission direction from the hand-held device 110 to the motor vehicle 105 or vice versa. Horizontal positions of the arrows correspond to times of the messages in the representation of the voltage characteristics.With reference to the first curve 205, an open-circuit voltage of the energy source 155 is approximately 2.8 V. If the voltage at the processing device 140 and / or receiving device 145 falls below a predetermined threshold value of 1.8 V here, for example, an undervoltage can be detected at which the processing device 140 is reset to a predetermined state (reset).To determine a distance or position of the hand-held device 110 with respect to the motor vehicle 105, a series of pulses is usually exchanged between the motor vehicle 105 and the hand-held device 110. The pulses each have predetermined time durations, and each pulse is spaced a predetermined time interval from a preceding or succeeding pulse. The pulses are transmitted successively by different transmitting devices 125 of the motor vehicle 105.A propagation speed of an emitted wireless pulse corresponds substantially to the speed of light. Due to the different positions at which the transmitting devices 125 are located on the motor vehicle 105, distances that the individual pulses must bridge to the receiving device 145 of the hand-held device 110 are of different lengths. Accordingly, reception times of temporally successive pulses at the hand-held device 110 are usually spaced apart in terms of time differently from by the predetermined time interval which lies between the pulses during transmission. From a deviation of a relative time difference between reception times and the time interval, relative distances between the receiving device 145 and the different transmitting devices 125 can be determined.Operating the receiving device 145 usually requires a significant removal of energy from the energy store 155. In other words, an increased electric current can be drawn from the energy store 155 during the reception. Due to the finite internal electrical resistance of the energy source 155, the voltage of the energy source 155 decreases when the receiving device 145 is switched on. This effect is mitigated if a capacitor 160 is provided. Points in time at which the receiving device 145 is switched on are represented in FIG. 2 by sections of the curves 205, 210 which sink almost vertically.Since it is approximately known when receiving an emitted pulse is to be expected, the receiving device 145 is preferably operated only in such time ranges. Between these times, the receiving device 145 is switched off, so that the voltage of the energy source 155 can rise again. The rise usually takes place more slowly than the fall.The multiple load of the energy source 155 due to the series of pulses leads overall to a drop in the average electrical voltage provided. This is not critical for the first curve 205, since the voltage is not close to the threshold value of 1.8 V at any point in time.However, with reference to the second curve 210, it may occur that the voltage of the energy source 155 falls below the predetermined threshold value at least briefly. In the example shown, this is the case at time 0.045. The short-term dropping below the threshold value of 1.8 V may be sufficient to trigger the reset generator 165. The distance or position determination can thereby be ended prematurely.It is proposed to increase the time interval which lies between the emission of two successive pulses if the performance of the electrical energy store 155 is not sufficient to reliably prevent the described dropping below the threshold value. Time ranges at which the receiving device 145 is switched on can then be time-equalized by a corresponding amount. The energy store 155 may have an improved opportunity to regenerate between loads by the receiver 145 and increase the electrical voltage provided by it.FIG. 3 shows a flow diagram of an example method 300. The method 300 can be carried out in particular by means of a system 100.In a step 305, a localization of the hand-held device 110 with respect to the motor vehicle 105 can be prepared. For this purpose, information can be exchanged between the hand-held device 110 and the motor vehicle 105 accordingly. The data is preferably exchanged by means of the further interfaces 130, 150. In one embodiment, the location may be prepared while the handheld device 110 is within communication range of the interfaces 130, 150, but not yet within communication range of the interfaces 125, 145. The actual localization can only take place when the hand-held device 110 is located close enough to the motor vehicle 105 so that wireless pulses can be exchanged between the transmitting devices 125 and 145.In a step 310, a power capability of the energy source 155 can be determined by the hand-held device 110. The performance may indicate to what value an electrical voltage provided by the power source 155 will break down when the receiver 145 is turned on for a predetermined period of time. The greater this voltage, the greater the performance may be. For determining the performance, it can be taken into account which voltage the energy source 155 provides immediately before the receiving device 145 is switched on.The performance may be determined based on different concepts. In one embodiment, a parameter of the energy source 155 may be determined in a step 315. The parameter can comprise, in particular, an open-circuit voltage, an electrical internal resistance or a temperature. The performance may then be determined based on one or more elevated parameters of the energy source 155.In a step 320, it can be determined whether the energy source 155 was overloaded in a past position determination of the hand-held device 110 with respect to the motor vehicle 105. An overload can be detected if the electrical voltage provided by the energy source 155 has fallen below a predetermined threshold value. In this case, a time interval used in the past positioning can be extended. The extension can be effected by a predetermined increment. Should it be determined at a later time that the energy source 155 has been recharged or replaced, the time interval may be reset to a predetermined, low value.In a step 325, the performance of the energy source 155 can be determined on the basis of a model. The model can originate from a predetermined energy which is stored in the energy source 155 or can be called up by the energy source 155. Withdrawals of energy from the energy source 155 may be tracked and a remaining energy may be determined based on the model. The larger the remaining energy, the greater the power capability of the power source 155. It should be appreciated that the performance of the energy source 155 may be based on one or more of steps 315 through 325 or portions thereof.In a step 330, a time interval can be negotiated between the handheld device 110 and the motor vehicle 105. In this case, the hand-held device 110 proposes one or more intervals of different lengths, of which the shortest is preferably already sufficiently long in order to avoid overloading of the energy source 155 when a position is determined. If step 320 was previously carried out, the shortest time interval offered can correspond to the time interval determined in step 320. The motor vehicle 105 can confirm one of the time intervals offered, so that it is known on both sides 105, 110 which time interval is used for the positioning.In a step 335, wireless pulses can be emitted alternately by the hand-held device 110 and motor vehicle 105. The pulses are transmitted successively, with a time interval in each case being situated between successive pulses. The pulses are preferably transmitted by different ones of the transmission devices 125 and 145.In a step 340, wireless pulses can be received by the hand-held device 110 and motor vehicle 105. For this purpose, the receiving devices 125 and 145 can be activated in the short term in each case when the arrival of a wireless pulse is expected.In a step 345, a direction and / or distance of the hand-held device 110 with respect to the motor vehicle 105 can be determined. For this purpose, relative time intervals between reception times of the transmitted wireless pulses can be taken into account. Knowing a geometry in which the transmitting devices 125 are attached to positions of the motor vehicle 105, a distance and / or a direction of the hand-held device 110 with respect to the motor vehicle 105 can be determined.Reference numerals denote reference numerals100 System 105 Motor vehicle 110 Hand-held device 115 Control device 120 Processing device 125 Transmission device 130 Interface 140 Processing device 145 Reception device 150 Interface 155 Energy source, energy store 160 Buffer store 165 Voltage monitoring, reset generator 205 First curve 210 Second curve 300 Method 305 Prepare 310 Performance of the energy source determine 315 Parameters of the energy source determine 320 upon reset: Extend time interval 325 Model of the energy source 330 Negotiate time interval 335 Pulses at time intervals transmit 340 Pulses receive 345 Hand-held device

Claims

Method (300) for locating a hand-held device (110) with respect to a motor vehicle (105), the method (300) comprising the following steps: - negotiation (330) of a time interval between the hand-held device (110) and the motor vehicle (105); - exchange (335, 340) of a series of wireless pulses between the motor vehicle (105) and the hand-held device (110); - wherein the wireless pulses are emitted offset by the time interval from the hand-held device (110) and from different positions on the motor vehicle (105); and - determination (345) of a position of the hand-held device (110) with respect to the motor vehicle (105) on the basis of time intervals between reception times of the wireless pulses on the hand-held device (110); characterized in that - the time interval is negotiated as a function of a capability (310) of an energy source (155) of the hand-held device (110).The method (300) of claim 1, wherein the time interval is extended as the power capability of the energy source (155) decreases.Method (300) according to claim 2, wherein the energy source (155) provides an electrical voltage and the performance is determined depending on the electrical voltage provided.Method (300) according to one of the preceding claims, wherein the energy source (155) provides an electrical voltage and the performance is determined as a function of an electrical internal resistance of the energy source (155).Method (300) according to one of the preceding claims, wherein the energy source (155) comprises an electrochemical energy store; and the performance is determined as a function of a temperature in the region of the energy store.The method (300) of any preceding claim, wherein the energy source (155) comprises an energy store and the power capability of the energy store is determined based on past energy drains from the energy store.Hand-held device (110) for communication with a motor vehicle (105), wherein the hand-held device (110) comprises: - a wireless receiver; - an energy source (155); and - a processing device (140) which is configured to: - negotiate a time interval with a motor vehicle (105); - receive a series of wireless pulses which are emitted offset from different positions on the motor vehicle (105) by the time interval; and - determine a position of the hand-held device (110) with respect to the motor vehicle (105) on the basis of time intervals between reception times of the wireless pulses at the hand-held device (110); characterized in that - the processing device (140) is further configured to negotiate the time interval as a function of a capability of the energy source (155) of the hand-held device (110).The handheld device (110) of claim 7, wherein the receiver is activated only when a wireless pulse is expected to arrive; wherein an electrical voltage of the energy source (155) is reduced while the receiver is activated.The hand-held device (110) according to claim 7 or 8, wherein the energy source (155) comprises a buffer store (160) for temporarily providing an increased electric current.The handheld device (110) of any of claims 7 to 9, wherein the time interval is extended if an electrical voltage of the power source (155) falls below a predetermined threshold during activation of the wireless receiver.The hand-held device (110) according to claim 10, further comprising a reset generator (165) for putting the processing device (140) into a predetermined state when the electrical voltage falls below the predetermined threshold value.The hand-held device (110) according to any one of claims 7 to 11, further comprising a further wireless interface (150) for communication with the motor vehicle (105).The handheld device (110) according to any one of claims 7 to 12, wherein the handheld device (110) is configured to perform bilateral authentication with the motor vehicle (105); and request a predetermined function of the motor vehicle (105).

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