CN113671206A - Method and processing unit for determining vehicle speed - Google Patents

Method and processing unit for determining vehicle speed Download PDF

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Publication number
CN113671206A
CN113671206A CN202110520263.5A CN202110520263A CN113671206A CN 113671206 A CN113671206 A CN 113671206A CN 202110520263 A CN202110520263 A CN 202110520263A CN 113671206 A CN113671206 A CN 113671206A
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China
Prior art keywords
vehicle
wheel
radio signal
speed
frequency
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CN202110520263.5A
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Chinese (zh)
Inventor
卢卡斯·普瑞瑟尔
弗兰齐斯库斯·鲍尔
玛丽娜·加西亚帕斯托尔
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Ford Global Technologies LLC
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Ford Global Technologies LLC
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Publication of CN113671206A publication Critical patent/CN113671206A/en
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P3/00—Measuring linear or angular speed; Measuring differences of linear or angular speeds
    • G01P3/42—Devices characterised by the use of electric or magnetic means
    • G01P3/50—Devices characterised by the use of electric or magnetic means for measuring linear speed
    • G01P3/54—Devices characterised by the use of electric or magnetic means for measuring linear speed by measuring frequency of generated current or voltage
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P3/00—Measuring linear or angular speed; Measuring differences of linear or angular speeds
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
    • B60C23/00—Devices for measuring, signalling, controlling, or distributing tyre pressure or temperature, specially adapted for mounting on vehicles; Arrangement of tyre inflating devices on vehicles, e.g. of pumps or of tanks; Tyre cooling arrangements
    • B60C23/02—Signalling devices actuated by tyre pressure
    • B60C23/04—Signalling devices actuated by tyre pressure mounted on the wheel or tyre
    • B60C23/0408—Signalling devices actuated by tyre pressure mounted on the wheel or tyre transmitting the signals by non-mechanical means from the wheel or tyre to a vehicle body mounted receiver
    • B60C23/0422—Signalling devices actuated by tyre pressure mounted on the wheel or tyre transmitting the signals by non-mechanical means from the wheel or tyre to a vehicle body mounted receiver characterised by the type of signal transmission means
    • B60C23/0433—Radio signals
    • B60C23/0435—Vehicle body mounted circuits, e.g. transceiver or antenna fixed to central console, door, roof, mirror or fender
    • B60C23/0437—Means for detecting electromagnetic field changes not being part of the signal transmission per se, e.g. strength, direction, propagation or masking
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P3/00—Measuring linear or angular speed; Measuring differences of linear or angular speeds
    • G01P3/64—Devices characterised by the determination of the time taken to traverse a fixed distance
    • G01P3/66—Devices characterised by the determination of the time taken to traverse a fixed distance using electric or magnetic means
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S11/00—Systems for determining distance or velocity not using reflection or reradiation
    • G01S11/02—Systems for determining distance or velocity not using reflection or reradiation using radio waves
    • G01S11/10—Systems for determining distance or velocity not using reflection or reradiation using radio waves using Doppler effect

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Electromagnetism (AREA)
  • Mechanical Engineering (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Radar Systems Or Details Thereof (AREA)
  • Measuring Fluid Pressure (AREA)

Abstract

Detailed description of the invention a method for determining the speed v of a vehicle 20By means of which radio signals 6 emitted by transmission means 4 arranged positionally fixed on the wheel 1 and spaced apart from the axis of rotation 3 of the wheel 4 and received by a receiver 5 arranged on the vehicle 2 are processed, wherein the vehicle speed v0Is determined on the basis of the influence of the doppler effect on the radio signal 6. Furthermore, the invention specifies a method for determining the rotational speed of the wheel 1 of the vehicle 2, a processing unit 7, the vehicle 2 and a computer program.

Description

Method and processing unit for determining vehicle speed
Technical Field
The present invention relates to a method for determining a vehicle speed of a vehicle and a method for determining a rotational speed of a wheel of a vehicle. The invention further relates to a processing unit, a vehicle and a computer program.
Background
Vehicles, for example in the form of semi-autonomous or fully autonomous vehicles, are increasingly automatically operated. For this purpose, standardized driver assistance systems are increasingly being used to implement the main safety functions of the vehicle or to support the driver in this respect.
For some such driver assistance systems, it is necessary to be able to determine the current vehicle speed as accurately and reliably as possible. For this purpose, wheel speed sensors may be used, which make it possible to determine the rotational speed of the wheel. The vehicle speed may then be determined based on the circumference of the wheel, which may be determined by the rolling radius of the wheel, and the rotational speed.
Wheel speed sensors, as the sole source of information about vehicle speed, are weak in terms of the safety requirements to be met by the driver assistance system. Alternative methods, such as determining the speed by a global navigation satellite system (e.g., GPS (global positioning system)) that can be used to track changes in the vehicle's position and to determine the vehicle's speed based on the changes in the vehicle's position, typically do not have the required reliability. The reasons for this are: signal availability, for example in tunnels, canyons, etc., and reduced signal quality, for example in the case of dense clouds, is not always guaranteed.
Disclosure of Invention
Against this background, the object of the invention is to specify a method and a device with which the vehicle speed of a wheel-driven vehicle can be determined accurately and reliably.
This object is achieved by the subject matter of the independent claims. The dependent claims relate to embodiments of these solutions according to the invention.
The basic idea of the invention is to use the characteristics of radio waves or radio signals to determine the vehicle speed on the basis of the occurring doppler effect. For example, a radio data transmission carrier signal between a tire pressure monitoring system arranged in the rim of the tire and a corresponding evaluation circuit can be used for this purpose.
If the wheel rotates, the position of the transmission device for the radio signal changes in two spatial directions, for example along a sinusoidal curve, relative to the receiving device, which is arranged fixedly with respect to the vehicle. Along with the change in position, the frequency of the radio signal also changes. The frequency increases when the transmitting device is approaching the receiving device and decreases when the transmitting device is moving away from the receiving device. The resulting difference between the transmitted frequency at the transmitting device and the received frequency at the receiving device is referred to below as the frequency variation or doppler frequency. The frequency variation may have a positive sign (frequency increase) or a negative sign (frequency decrease).
A first aspect of the invention relates to a method for determining the vehicle speed of a vehicle, in which method radio signals emitted by a transmission device and received by a receiving device arranged on the vehicle are processed, the transmission device being positionally fixed on a wheel of the vehicle and spaced apart from the axis of rotation of the wheel. The vehicle speed is determined based on the influence of the doppler effect on the radio signal.
A vehicle is understood to be any mobile transport mode, regardless of its type of propulsion, for example a passenger car. The vehicle has at least one wheel, but the vehicle may of course also have a plurality of wheels, for example two, three or four wheels. The wheels are used to establish a link between the vehicle and a roadway (e.g., a road) in which the vehicle is used. During movement of the vehicle, the wheels rotate about their respective axes of rotation. The wheel may have a rubber tire as a running surface or contact surface with the roadway. Alternatively, the rubber tire may be replaced with, for example, an endless chain or the like.
In order to determine the speed of the vehicle, a radio signal is processed or evaluated, which is emitted by a transmission device arranged in a stationary manner relative to the wheels and which is received by a receiving device arranged on the vehicle.
The transfer device is positioned spaced from the axis of rotation of the wheel so that the transfer device also moves in accordance with the rotation of the wheel. The positionally fixed arrangement relative to the wheel allows the movement of the transmission means to be correlated with the movement of the wheel.
The receiving device may be designed as an antenna and be located on or in the vehicle. Preferably, the receiving device may be arranged in a fixed position relative to the other vehicle components, so that a variable but defined distance is always established between the transmitting device and the receiving device. For example, the receiving device may be firmly connected to the vehicle chassis or body. Thus, a relative movement occurs between the transmitting device and the receiving device during the movement of the wheel.
Rotation of the wheel changes the distance between the transmitting device and the receiving device. When the transmitting device and the receiving device are close to each other, there is a time compression, i.e. an increase in frequency, of the emitted radio signal. This leads to an increase in the time, i.e. a decrease in the frequency, of the emitted radio signal if the transmitting device and the receiving device are far away from each other. The rotational movement of the wheel results in a continuously uniform change between the increase and decrease in frequency.
In order to determine the vehicle speed, the frequency change of the received radio waves can be evaluated in a first variant of the method. That is, the effect of the radio signal may be a change in the frequency of the radio signal upon which the vehicle speed is determined.
This first variant has the following advantages: the transmission of radio signals can only be transmitted for a short period of time, i.e. sufficient time to determine the frequency change. Thus, this variant can be used if only a short time portion of the radio signal can be detected. Accordingly, the energy required to emit the radio signal is low, so that for example a packaged battery, the service life of which may be years or even the entire life of the vehicle, may be used as an energy source. Further, in this variation, the vehicle speed is determined independent of the wheel circumference, so that variations in the wheel circumference (e.g., by reducing the tire profile) are not relevant to determining the vehicle speed.
In order to determine the vehicle speed more precisely, it may be provided that the vehicle speed is determined as an average, for example as an arithmetic average, on the basis of the radio signals of a plurality of (preferably all) wheels of the vehicle, and that the individual vehicle speeds are determined from these.
For example, the frequency variation of the radio signal may be determined by a Fast Fourier Transform (FFT).
FFT is a method for determining the doppler frequency. When the wheel is stationary, the maximum FFT result is at frequency 0. As the wheel rotates, the maximum moves, or both maxima move from zero to the doppler frequency. The advantage of FFT is fast and resource-saving computation. A possible disadvantage is that the doppler frequency is between the two sampling frequencies of the FFT. In this case, the increase of two adjacent sampling frequencies is measured compared to the other sampling frequencies, and interpolation between two sampling frequencies must be performed.
Alternatively, the frequency variation of the radio signal may be determined by direct estimation.
In the case of PSK signals (PSK, phase shift keying) or ASK signals (ASK, amplitude shift keying), each received symbol is subject to a growing phase error. The rate of change of phase is proportional to the doppler frequency.
Direct estimation may be performed blindly based on received data (e.g., data that is not known a priori in the receiving device, such as information about tire pressure) or via pilot symbols. For example, the useful signal received after baseband demodulation may follow the frequency f of the received radio signal over timeαAnd (4) rotating. With the known pilot symbols, the frequency variation can be estimated from the received signal. At least when fα×tsThe frequency can also be estimated blindly when it is much smaller than the phase difference between the transmitted unknown useful signal symbols. Where t issIs the symbol time of the transmitted user signal bit.
In the case of Frequency Shift Keying (FSK), the phase difference between subsequently received symbols will always be slightly different from the expected difference. Delta (Δ δ) and f of differenceα×tsAnd (4) in proportion.
In a second method variant, the period duration of the sign change of the frequency change of the radio signal, i.e. the time interval between two successive frequency increases or decreases, can be evaluated for determining the vehicle speed, since the frequency of each wheel revolution detected at the receiving device increases once, decreases once. Thus, the effect of the radio signal may be the period duration of the symbol variation of the frequency variation of the radio signal.
The cycle duration corresponds to the length of time it takes for the wheel to make one revolution. The rotational speed of the wheel can thus be determined from the cycle duration. If the rolling radius or wheel circumference of the wheel is known, the vehicle speed may be determined based on the determined rotational speed. In order to more accurately determine the vehicle speed, the vehicle speed may be determined as an average, for example, as an arithmetic average determined from the rotational speeds of a plurality of (preferably all) wheels of the vehicle.
This second variant has the following advantages: it is not necessary to determine the exact frequency change, only whether the frequency is increased to a maximum or decreased to a minimum, i.e. whether the sign of the frequency change is positive or negative. The doppler frequency oscillates sinusoidally, because the direction of movement of the transmission means changes constantly between the X and Y directions due to the circular motion. For measuring the period duration, the time lapse between two zero points or the time between two extreme values can be measured.
However, a correspondingly long transmission of the radio signal is necessary for this purpose, i.e. the duration of the transmission of the radio signal must be at least so long that the transmission device can pass two opposite points, which, depending on the orientation of the receiving device relative to the transmission device, for example the highest and lowest points or the frontmost and rearmost points of the wheel, amounts to a change from increasing frequency to decreasing frequency or vice versa. In this variant, the vehicle speed is determined from the wheel circumference.
The determined vehicle speed may then be used by the driver assistance system to control vehicle functions. In addition to determining the vehicle speed, the determined rotational speed or rotational speed may also be used for other purposes, for example for detecting wheel slip.
Furthermore, the wheel rotational speed or vehicle speed determined by the proposed method may be compared with an otherwise determined rotational speed (e.g. determined by a wheel rotational speed sensor) or vehicle speed. If a deviation is detected, for example a deviation exceeding a predetermined fault tolerance, a warning message may be issued to indicate the condition and take any necessary action to more accurately analyze the cause and correct the problem.
The proposed method allows an accurate and reliable determination of the vehicle speed and, if necessary, deduction of parameters from the vehicle speed. Advantageously, the method may be performed completely within the vehicle, i.e. independent of the external system, so as to eliminate sources of errors otherwise connected to the external system (e.g. global satellite navigation system). Furthermore, the method may be used as a redundant way to determine vehicle speed, which may reduce the susceptibility of vehicle assistance systems to errors and improve vehicle safety.
Another aspect of the invention relates to a method for determining a rotational speed of a wheel of a vehicle. In this case, a radio signal is processed which is emitted by a transmission device fixed in position on the wheel and spaced apart from the axis of rotation of the wheel and is received by a receiving device provided on the vehicle, wherein the rotational speed of the wheel is determined on the basis of a change in the period duration of a change in the sign of a change in the frequency of the radio signal, which change is caused by the doppler effect.
The method may be performed according to the second variant of the method explained above. In this respect, the explanations of this second variant are also used to describe the method for determining the rotational speed, since in the case of this second variant the rotational speed or rotational speed is determined as an intermediate step in the determination of the vehicle speed.
According to different embodiment variants of the described method, the radio signal may be a modulated radio signal, i.e. a radio signal having a carrier signal and a useful signal.
Here, the analysis of the variation of the period duration of the frequency variation of the radio signal or of the sign variation of the frequency variation of the radio signal, i.e. the natural frequency range of the useful signal, can preferably be performed in the baseband.
The doppler effect affects the product of the baseband useful signal and the carrier signal. In the receiving apparatus, a carrier signal is known, and the carrier signal can be used to demodulate the received signal. The signal resulting from the demodulation is the baseband wanted signal modulated with the doppler frequency and any signal noise.
According to other embodiments of the described method, the radio signal may be a radio signal of a tire pressure monitoring system. Thus, the transmitting device or receiving device may be a transmitting device or receiving device of a tire pressure monitoring system. To determine vehicle speed, a useful signal of the tire pressure monitoring system may be evaluated.
This has the following advantages: in the context of other methods, radio signals have been transmitted, for example of a tire pressure monitoring system, and the associated transmission device and/or receiving device can be used to determine the vehicle speed. Additional radio signals and associated transmission and reception means may therefore be unnecessary. The proposed method can therefore be implemented cost-effectively, and there is also the possibility of simple retrofitting of existing vehicles, since only the processing unit for processing the radio signals needs to be suitably modified in order to determine the vehicle speed according to the proposed method.
Another aspect of the invention relates to a processing unit for determining a vehicle speed of a vehicle. The processing unit comprises means for carrying out one of the above-described methods, i.e. for example means for processing a radio signal transmitted by transmission means arranged positionally fixed on a wheel of the vehicle and spaced apart from the axis of rotation of the wheel and received by a receiver arranged on the vehicle, wherein the processing is carried out in such a way that the vehicle speed is determined on the basis of the influence of the doppler effect on the radio signal.
The above explanations regarding the description of the method according to the invention also serve to describe the processing unit. The advantages of the method are accordingly associated with the processing unit.
The processing unit has a signal connection to the receiving means. The receiving means may also be integrated in the processing unit. Preferably, the processing unit may be provided in the vehicle, so that it is possible to autonomously determine the wheel rotation speed or the vehicle speed within the vehicle.
The processing unit processes the received radio signal based on instructions or based on code programmed in the processing unit according to one or more programs. If the radio signal is a modulated radio signal, the processing may also comprise a demodulation step in order to be able to separate the useful signal from the carrier signal.
The processing unit may be implemented in hardware and/or software and in a single physical form or in a plurality of physical forms. The processing unit may be part of or integrated into an engine controller of the vehicle.
Another aspect of the invention relates to a vehicle having an apparatus for determining a vehicle speed of the vehicle. The device is provided with: a transmission device which is arranged on the wheel in a positionally fixed manner and is spaced apart from the axis of rotation of the wheel, which transmission device is designed to transmit radio signals, a receiving device which is arranged on the vehicle and is designed to receive the transmitted radio signals, and a processing unit according to the above description.
The processing unit is thus designed to process the received radio signals in order to determine the vehicle speed on the basis of the influence of the doppler effect on the radio signals.
Accordingly, the vehicle may be designed to carry out the method described above. Therefore, the above explanation is for explaining the method of the present invention and for describing the vehicle. The advantages of the method are accordingly associated with the vehicle.
In a different variant, the vehicle may have a plurality of wheels, each wheel having a transmission device. Here, the receiving means may be disposed equidistantly from each wheel. For example, a vehicle may have two pairs of wheels, each pair of wheels being connected to each other by an axle.
Equidistant means that the distance between the receiving device and the wheel is the same in each case. For this purpose, the receiving device can be arranged in the middle of the vehicle, for example.
The advantage of the equidistant arrangement of the receiving means with respect to the wheel is that the radio signals of all transmitting means can be handled equally well. If the receiving means is moved closer to one side, i.e. towards some wheels and away from others, the angle to the other side becomes less favourable compared to an equidistant arrangement, as a result of which the doppler effect may be measured less well, as the doppler effect is proportional to cos α.
More advantageously, the vehicle speed can be determined based on radio signals of a plurality of wheels by only one receiving device and one processing unit, so that costs and installation space can be saved.
Another aspect of the invention relates to a computer program comprising commands for causing a processing unit to execute a method according to the above description.
The above explanations of the method and the processing unit therefore also serve to describe the computer program. The advantages of the method and the processing unit are correspondingly associated with the computer program.
A computer program may be understood as a program code, which may be stored on and/or retrieved via a suitable medium. Any medium suitable for storing software, such as a non-volatile memory installed in the control unit, a DVD (digital versatile disc), a USB disk, a flash memory card, etc., may be used for storing the program code. The program code may be accessed, for example, over the internet or an intranet, or through other suitable wireless or wireline networks.
Another aspect of the invention relates to a computer-readable data carrier on which a computer program is stored.
Drawings
The invention is explained in more detail below on the basis of the figures and the corresponding description. In the drawings:
FIG. 1 shows a schematic view of a vehicle of exemplary design;
FIG. 2 shows a schematic diagram (top view) illustrating the Doppler effect;
FIG. 3a shows a schematic diagram illustrating the determination of vehicle speed;
FIG. 3b shows a schematic (side view) of Doppler frequency as a function of wheel rotation; and
FIG. 4 shows a flow chart of an example method.
Detailed Description
In fig. 1, a vehicle 2 is schematically shown, the vehicle 2 being a passenger car with four rubber- tired wheels 1a,1b,1c,1d, wherein each two wheels 1a,1b,1c,1d are connected to each other by a common rotating wheel axle 3. However, the invention is not limited to such passenger vehicles and may also be used for other vehicles having at least one wheel. The vehicle 2 is provided withDevice 8, with which device 8 the speed v of the vehicle 2 can be determined0。
The device 8 comprises a transmission device 4a,4b,4c,4d arranged on each wheel 1a,1b,1c,1d, the transmission device 4a,4b,4c,4d being designed to emit a radio signal 6a,6b,6c,6 d. The transfer devices 4a,4b,4c,4d are located positionally fixed on the wheels 1a,1b,1c,1d and spaced apart from the respective axis of rotation 3 and are thus firmly connected to the respective wheels 1a,1b,1c,1d, so that the transfer devices 4a,4b,4c,4d also perform a rotational movement of the wheels 1a,1b,1c,1 d.
The transmission devices 4a,4b,4c,4d are part of a tire pressure monitoring system which can be used for directly measuring the pressure of the respective tire and for transmitting the corresponding sensor signal to a control unit in the vehicle. For this purpose, the transport devices 4a,4b,4c,4d may be integrated into the valves of the tires.
The device 8 further comprises a receiving device 5 arranged on or in the vehicle, which receiving device 5 may be arranged equidistantly to the wheels 1a,1b,1c,1d, as shown in fig. 1. The equidistant arrangement has the following advantages: the influence of the doppler effect on the radio signals 6a,6b,6c,6d can equally well be determined for all radio signals 6a,6b,6c,6 d. If the receiving means 5 is moved closer to the axis of rotation 3, the angle alpha (see fig. 2) will become larger and the doppler effect may be measured worse, since the doppler effect is proportional to cos alpha.
The receiver device 5 may also be part of a tire pressure monitoring system, i.e. may correspond to a receiver device of a tire pressure monitoring system. The receiving means 5 are designed to receive the radio signals 6a,6b,6c,6d emitted by the transmitting means 4a,4b,4c,4 d.
Furthermore, the device 8 has a processing unit 7, which processing unit 7 is integrated in a common component together with the receiving device 5 in the exemplary embodiment. However, the processing unit 7 may also be provided separately, so long as an effective signal connection can be established between the receiving means 5 and the processing unit 7, so that the processing unit 7 can process the received radio signals 6a,6b,6c,6 d.
The processing unit 7 is designed to determine the vehicle speed v of the vehicle 20. For this purpose, the received radio signals 6a,6b,6c,6d are processed accordingly, wherein the influence of the doppler effect on the radio signals 6a,6b,6c,6d is evaluated. The vehicle speed v will be explained in more detail below with reference to fig. 2 and 3a, 3b0And (4) determining.
The processing unit 7 can be designed to determine the vehicle speed v0Compared to the vehicle speed determined in another way and designed to identify any deviation or to confirm the vehicle speed determined in another way.
The following explains the determination of the vehicle speed v of the vehicle 2 with reference to fig. 40Steps of the exemplary method of (a). For example, the method may be performed with the vehicle 2 explained above with reference to fig. 1.
After the method has started, in a step S1 a radio signal 6a,6b,6c,6d is emitted by the transmission device 4a,4b,4c,4 d. In step S2, the emitted radio signals 6a,6b,6c,6d are received by the receiving device 5.
In step S3, the received radio signals 6a,6b,6c,6d are processed by the processing unit 7. For processing the radio signals 6a,6b,6c,6d, the influence of the doppler effect on the radio signals 6a,6b,6c,6d is evaluated. For this purpose, the frequency change f of the radio signals 6a,6b,6c,6d can alternatively be evaluatedDOr the frequency change f of the radio signal 6a,6b,6c,6d can be determinedDAnd the wheel rotational speed and the vehicle speed v can be determined on the basis thereof0。
In step S4 (optional), the vehicle speed v is determined0May be compared to a vehicle speed determined in another manner. In the case of a deviation, an alarm signal can be issued. The method ends here.
The vehicle speed v is explained in more detail below with reference to fig. 2 and 30And (4) determining. Fig. 2 shows a simplified illustration of the vehicle 2 from fig. 1, so that the explanations with respect to fig. 1 can be referred to for the overall design.
The vehicle speed v is carried out by means of radio signals 6a,6b,6c,6d0Is determined, the radioThe electrical signals 6a,6b,6c,6d are output by transmission devices 4a,4b,4c,4d arranged on the wheels 1a,1b,1c,1 d. Here, the so-called doppler effect is used, which causes a change in the frequency of the radio waves of the radio signals 6a,6b,6c,6d when the distance between the transmission means 4a,4b,4c,4d and the reception means 5 changes.
If the vehicle 2 moves while the position of the receiving device 5 relative to the vehicle 2 remains unchanged, the wheels 1a,1b,1c,1d and thus the transmission devices 4a,4b,4c,4d, which are arranged in a positionally fixed manner relative to the wheels 1a,1b,1c,1d, move relative to the rest of the vehicle 2. Due to the rotational movement of the wheels 1a,1b,1c,1d about their respective rotational axis 3, this results in the transfer devices 4a,4b,4c,4d alternately approaching the receiving device 5 and moving away from the receiving device 5 again.
If the vehicle 2 is traveling in a forward direction and the receiving device 5 is arranged on a plane substantially parallel to the roadway together with the wheels 1a,1b,1c,1d, the transmitting device 4 arranged on the front wheel approaches the receiving device 5 from a front position to a rear position, the transmitting device 4 being furthest from the receiving device 5 in the front position and the transmitting device 4 being closest to the receiving device 5 in the rear position. Subsequently, the transmission device 4 is moved from the rear position toward the front position away from the reception device 5 again. This is shown in fig. 3, in which fig. 3 the change in position of the transmission device 4 during the forward movement is indicated by a dash-dotted arrow, and the possible positions of the transmission device 4 are indicated by symbols representing the dashed outline of the transmission device 4.
This applies in reverse order to the rear wheels of the vehicle 2. That is, if the vehicle 2 is traveling in the forward direction, the transmission device 4 provided on the rear wheel moves from the front position to the rear position away from the reception device 5, the transmission device 4 is closest to the reception device 5 in the front position, and the transmission device 4 is farthest from the reception device 5 in the rear position. Subsequently, the transmission device 4 approaches the reception device 5 again from the rear position toward the front position.
To determine the vehicle speed v0(speed of the vehicle in the direction of travel), or the Doppler effect may be evaluatedFrequency variation f of radio signal 6DSpeed v of the vehicle0Can vary f directly according to frequencyDTo determine (variant 1), or to determine the frequency change f of the radio signal 6DMay be determined from the cycle duration, the rotational speed of the wheel 1 may be determined from the cycle duration and the vehicle speed v may be determined from the cycle duration0(variant 2).
When evaluating the frequency change f caused by the Doppler effectDThe direction of the doppler effect must be taken into account. This means that the frequency variation f detected at the receiving means 5 isDDepending on the angle β (see fig. 2) between the direction of travel of the vehicle and the reception direction of the receiving device 5, since only the component of the movement of the transmitting device 4 in the reception direction influences the frequency change f detectable by the receiving device 5D. This component is proportional to cos β.
FIGS. 3a, 3b illustrate and determine vehicle speed v0Speed of interest (fig. 3a) and frequency variation f as a function of wheel rotationD(FIG. 3 b). The support point of the wheel 1 has a speed of zero determined by a stationary observer outside the vehicle 2. The centre of the wheel 1 and the receiving means 5 are at the speed v of the vehicle0And (4) moving. The apex of the wheel 1 is at twice the vehicle speed v0And (4) moving. The velocity associated with the doppler effect is ± vehicle velocity v with respect to the receiving device 50。
Doppler frequency fDDepending on the velocity v in the X direction in fig. 3bxRather than the Y component. And therefore depends on the current position of the transmission means 4, which is determined by the angle alpha in fig. 3 b. That is, the Doppler frequency fDSinusoidal oscillations because the direction of movement of the transport means 4 varies constantly between the X and Y directions due to the circular movement. Thus VxIs the X component of the speed of the transmission device 4, the magnitude of which relative to the receiving device 5 corresponds to the vehicle speed v0. At α ═ 0, the velocity vector of the transport device 4 points vertically downwards. V theny＝-v0And v isx＝0。Vx(. alpha.) is a function, in the case of which vxDepending on alpha.
As already mentioned, the doppler effect is influenced by the angle β between the direction of travel and the direction of reception determined by the position of the receiving means 5. Frequency f of received radio signal 6βCorresponding to the frequency f of the emitted radio signal 6 changed by the Doppler effectcIn which the frequency f of the received radio signal 6βAnd frequency fcCompared with that
Figure BDA0003063631580000121
And
Figure BDA0003063631580000122
to move in between.
The following also applies (fig. 3 b):
α＝-ωt
ω＝2πfrad
vx(t)＝v0sinωt
Figure BDA0003063631580000123
Figure BDA0003063631580000124
Figure BDA0003063631580000125
if the Doppler frequency fDAs in use for determining vehicle speed v0As determined in variant 1 of the method of (3), it is then possible to relate to the known frequency f of the emitted radio signalcKnown frequency variation fDCalculating the vehicle speed v from the known angle beta0。
Figure BDA0003063631580000126
vβ＝cosβ×v0sinωt
So as to facilitate the use of
Figure BDA0003063631580000131
Example of variant 1 (the effect of the radio signal 6 is a frequency change f of the radio signal 6D)：
Under the assumption that β is 0, which does not violate the general validity, the maximum frequency variation f of the measurementDIs 50 Hz. The carrier frequency is 500 MHz. At the speed of light c0is-3X 108In the case of m/s, this corresponds approximately to 50Hz 3X 108Vehicle speed of 30m/s at m/s/500MHz, which corresponds to 108 km/h.
Example of variant 2 (the effect of the radio signal 6 is a frequency change f of the radio signal 6DThe period duration of the sign change of):
the wheel circumference is 2 m. If the Doppler frequency fDIs measured as 25ms, a full wheel revolution takes 50 ms. The wheel was rotated 20 times in 1 second. From this, the rotational speed ω can be determined. In addition, the vehicle moves at a speed of 40 meters per second according to this. The speed is therefore 40 m/s-144 km/h.
List of reference numerals
1,1a,1b,1c,1d wheel
2 vehicle
3 axis of rotation, rotating wheel axle
4,4a,4b,4c,4d transmission device
5 receiving device
6,6a,6b,6c,6d radio signal
7 processing unit
8 device
9 direction of rotation
c0Speed of light
fcFrequency of the emitted radio signal (carrier frequency)
fαFrequency as a function of alpha
fβFrequency as a function of beta
fradRotational speed of wheel (revolutions per second)
fDFrequency variation due to doppler effect
time t
tsSymbol time of transmitted user signal bit
v0Speed of the vehicle in the direction of travel/magnitude of the speed of the transmitter relative to the speed of the receiving device
vxX component of speed of transmission device
vyY component of speed of transmission device
vx(α) v as a function of αx
Rotation angle of alpha receiver
Angle between the direction of travel of the beta vehicle and the direction of reception by the receiving device
Speed of rotation of omega
S1 sending radio signal
S2 receiving radio signal
S3 processing radio signals to determine rotational speed
S4 determining vehicle speed based on rotation speed

Claims (12)

1. A method for determining the speed v of a vehicle (2)0In which a radio signal (6) emitted by a transmission device (4) arranged positionally fixed on a wheel (1) of the vehicle (2) and spaced apart from an axis of rotation (3) of the wheel (1) and received by a receiving device (5) arranged on the vehicle (2) is processed, wherein,the vehicle speed v0Is determined on the basis of the influence of the doppler effect on the radio signal (6).
2. The method according to claim 1, wherein the influence on the radio signal (6) is a frequency variation f of the radio signal (6)D。
3. Method according to claim 2, wherein the frequency variation f of the radio signal (6)DIs determined by a fast fourier transform.
4. Method according to claim 2, wherein the frequency variation f of the radio signal (6)DIs determined by direct estimation.
5. The method according to claim 1, wherein the influence on the radio signal (6) is a frequency variation f of the radio signal (6)DThe period duration of the symbol change.
6. Method for determining the rotational speed of a wheel (1) of a vehicle (2), in which method a radio signal (6) emitted by a transmission device (4) which is arranged positionally fixed on the wheel (1) and spaced apart from the axis of rotation (3) of the wheel (1) and received by a receiving device (5) arranged on the vehicle (2) is processed, wherein the rotational speed of the wheel (1) is based on a frequency change f of the radio signal (6) caused by the doppler effectDIs determined by the change in the period duration of the symbol change.
7. The method according to any of the preceding claims, wherein the radio signal (6) is a modulated radio signal having a carrier signal and a wanted signal.
8. Method according to any one of the preceding claims, wherein said radio signal (6) is a radio signal of a tyre pressure monitoring system.
9. A method for determining the speed v of a vehicle (2)0Or the rotational speed of a wheel (1) of a vehicle (2), said processing unit (7) comprising means for performing the method according to any one of claims 1 to 8.
10. A vehicle (2), the vehicle (2) having a vehicle speed v for determining the vehicle (2)0Or the rotational speed of a wheel (1) of the vehicle (2), the device (8) having:
-a transmission device (4) which is arranged in a stationary manner on the wheel (1) of the vehicle (2) and is spaced apart from the axis of rotation (3) of the wheel (1), the transmission device (4) being designed for emitting a radio signal (6),
-a receiving device (5) arranged on the vehicle (2), which receiving device (5) is designed to receive the emitted radio signal (6), and
-a processing unit (7) according to claim 9.
11. Vehicle (2) according to claim 10, wherein the vehicle (2) has a plurality of wheels (1a, 1b,1c, 1d), each wheel (1a, 1b,1c, 1d) having a transmission device (4a, 4b,4c, 4d), and wherein the receiving device (5) is arranged equidistantly from each wheel (1a, 1b,1c,1 d).
12. A computer program comprising instructions for causing a processing unit (7) according to claim 9 to perform the method according to any one of claims 1 to 8.
CN202110520263.5A 2020-05-15 2021-05-13 Method and processing unit for determining vehicle speed Pending CN113671206A (en)

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