阅读说明：本技术 用于确定设有轮胎压力监测系统的机动车辆的运动开始的方法 (Method for determining the start of a movement of a motor vehicle provided with a tyre pressure monitoring system ) 是由 S.高德特 S.比利 于 2018-05-17 设计创作，主要内容包括：一种用于确定机动车辆的运动开始的方法,该机动车辆设有用于监测机动车辆轮胎压力的系统,用于监测压力的系统的接收器与每个发射器之间的通信经受多普勒效应,使得周期性分量插入到由发射器发射到接收器的信号中。该方法的特征在于,其包括以下步骤：在由计算装置解调以提取由射频信号所携带的数据之前获取中频信号,确定中频信号的快速傅立叶变换,在预设的持续时间内确定中频信号的快速傅立叶变换的平均值,通过将快速傅立叶变换的瞬时值与快速傅立叶变换的平均值进行比较,确定是否存在频率偏差,如果是这种情况,则确定偏差的幅度是否高于阈值,如果是这种情况,则确定偏差是否是周期性的,如果是这种情况,则确定：频率偏差与由于多普勒效应而插入到由发射器发射的信号中的周期性分量相对应,用于监测轮胎压力的发射器正在运动,且车辆正在运动。(A method for determining the start of movement of a motor vehicle provided with a system for monitoring the pressure of the tyres of the motor vehicle, the communication between the receiver and each transmitter of the system for monitoring the pressure being subject to the Doppler effect, so that a periodic component is inserted in the signal transmitted by the transmitter to the receiver. The method is characterized in that it comprises the following steps: acquiring the intermediate frequency signal before demodulation by the calculation means to extract the data carried by the radio frequency signal, determining the fast fourier transform of the intermediate frequency signal, determining the mean value of the fast fourier transform of the intermediate frequency signal over a preset duration, determining whether there is a frequency deviation by comparing the instantaneous value of the fast fourier transform with the mean value of the fast fourier transform, determining if the magnitude of the deviation is above a threshold value if this is the case, determining if the deviation is periodic if this is the case, determining if: the frequency deviation corresponds to a periodic component inserted into the signal transmitted by the transmitter due to the doppler effect, the transmitter for monitoring the tire pressure is moving, and the vehicle is moving.)

1. Method for determining the start of a movement of a motor vehicle provided with at least one transmitter for monitoring the pressure of the tires of the motor vehicle and a receiver for monitoring the pressure of at least one tire, said receiver being connected to an electronic control unit of the motor vehicle and being able to communicate with the at least one transmitter for monitoring the pressure,

the communication between the receiver for monitoring and each transmitter for monitoring pressure is subject to the doppler effect, so that a periodic component is inserted into the signal transmitted by the transmitter to the receiver,

the receiver comprises an intermediate filter capable of reconstructing an intermediate frequency signal from the radio frequency signal and the reference signal,

the intermediate frequency signal can be demodulated by a computing device to extract the data carried by the radio frequency signal,

said method is characterized in that it comprises the following steps:

obtaining the intermediate frequency signal, and obtaining the intermediate frequency signal,

determining a fast fourier transform of the intermediate frequency signal,

determining an average value of a fast fourier transform of the intermediate frequency signal over a preset duration,

determining whether there is a frequency deviation by comparing instantaneous values of the fast fourier transform with an average value of the fast fourier transform,

if this is the case, determining if the absolute value of the deviation magnitude is above a threshold,

if this is the case, determining if the deviation is periodic,

if this is the case, then it is determined that: the frequency deviation corresponds to a periodic component inserted into the signal transmitted by the transmitter due to the doppler effect, the transmitter for monitoring the tire pressure is moving, and the vehicle is moving.

2. The method according to the preceding claim, wherein, for determining whether there is a frequency deviation depending on the instantaneous value of the fast Fourier transform and the average value of the fast Fourier transform,

subtracting the instantaneous value of the fast fourier transform from the average value of the fast fourier transform, and then determining whether the obtained signal is non-zero,

if this is the case, then a frequency deviation is determined to be present.

3. Method according to any one of the preceding claims, wherein the intermediate frequency signal is acquired when a transmitter for monitoring the tyre pressure is in a "low consumption" operating mode.

4. A method according to any preceding claim, wherein the operating mode of the transmitter for monitoring tyre pressure is switched from a "low consumption" operating mode to a "driving" operating mode when it is determined that the vehicle is moving.

Technical Field

The technical field of the invention is the determination of the start of movement of a motor vehicle and, more particularly, of such a start of movement by a system for monitoring the tyre pressure of a motor vehicle.

Background

In the prior art, a Tire Pressure monitoring system TPMS (english acronym for "Tire Pressure monitoring system") comprises a TPMS receiver connected to an electronic control unit of a vehicle, and at least one TPMS transmitter placed on a wheel of the vehicle. Typically, each wheel of the vehicle is provided with a TPMS transmitter.

The TPMS transmitter includes a radio frequency transmitter (operating at 315 MHz or 433.92 MHz depending on the country), a low frequency receiver (operating at 125 kHz), a microcontroller, sensors and a battery.

The sensors typically include pressure sensors, temperature sensors, and accelerometers.

The pressure sensor and the temperature sensor allow to measure the pressure and the temperature, respectively, of the air contained between the tyre and the rim.

The accelerometer allows the radial acceleration experienced by the wheel, and thus the movement of the vehicle, to be determined.

However, accelerometers are expensive components that are large in size and have high power consumption.

Therefore, there is a need for a more compact and less expensive TPMS transmitter.

There is also a need for a TPMS transmitter that consumes less power than prior transmitters.

Disclosure of Invention

The subject of the invention is a method for determining the start of a movement of a motor vehicle provided with at least one transmitter for monitoring the pressure of the tyres of the motor vehicle and a receiver for monitoring the pressure of at least one tyre, connected to an electronic control unit of the vehicle and able to communicate with said at least one transmitter for monitoring the pressure,

the communication between the monitoring receiver and each transmitter for monitoring pressure is subject to the doppler effect, so that a periodic component is inserted into the signal transmitted by the transmitter to the receiver,

the receiver comprises an intermediate filter capable of reconstructing an intermediate frequency signal from the radio frequency signal and the reference signal,

the intermediate frequency signal can be demodulated by a computing device to extract the data carried by the radio frequency signal.

The method is characterized in that it comprises the following steps:

obtaining the intermediate frequency signal, and obtaining the intermediate frequency signal,

determining a fast fourier transform of the intermediate frequency signal,

determining an average value of a fast fourier transform of the intermediate frequency signal over a preset duration,

determining whether there is a frequency deviation by comparing instantaneous values of the fast fourier transform with an average value of the fast fourier transform,

if this is the case, determining if the absolute value of the deviation magnitude is above a threshold,

if this is the case, determining if the deviation is periodic,

if this is the case, then it is determined that: the frequency deviation corresponds to a periodic component inserted into the signal transmitted by the transmitter due to the doppler effect, the transmitter for monitoring the tire pressure is moving, and the vehicle is moving.

In order to determine whether there is a frequency deviation depending on the momentary value of the fast fourier transform and the mean value of the fast fourier transform, the following steps can be performed:

subtracting the instantaneous value of the fast fourier transform from the average value of the fast fourier transform, and then determining whether the obtained signal is non-zero,

if this is the case, then a frequency deviation is determined to be present.

The intermediate frequency signal may be acquired when the transmitter used to monitor tire pressure is in a "low-cost" mode of operation.

When it is determined that the vehicle is moving, the operating mode of the transmitter for monitoring tire pressure may be switched from a "low consumption" operating mode to a "driving" operating mode.

Drawings

Other objects, features and advantages of the present invention will become apparent upon reading the following description, given by way of non-limiting example only, with reference to the accompanying drawings, in which:

figure 1 shows a radio frequency reception system of a TPMS receiver according to the prior art,

figure 2 shows a phase locked loop according to the prior art,

figure 3 shows the signal output from the intermediate filter of the TPMS receiver,

figure 4 shows a signal obtained from the output of the fast fourier transform of the intermediate frequency signal,

figure 5 shows the main steps of a method for determining the start of motion of a TPMS transmitter, according to one embodiment, an

Figure 6 shows the main steps of a method for determining the start of motion of a TPMS transmitter according to another embodiment.

Detailed Description

Fig. 1 illustrates a radio frequency receiving system of a TPMS receiver according to the related art.

It can be seen that it comprises a receiving antenna 1 connected to a parametric amplifier 2, the parametric amplifier 2 itself being connected to a mixer 3.

The mixer 3 is connected via another input to a Phase Locked Loop (PLL) with reference numeral 4 and via its output to an intermediate filter 5 of the computing means.

The receiving antenna 1 receives a radio frequency signal and converts it into an electrical signal of frequency F1, which is amplified by the parametric amplifier 2. The amplified signal is mixed with a frequency shift F1 + deltaf received from the phase locked loop 4 to produce an offset signal with a frequency deltaf.

The shifted signal is processed by an intermediate filter 5, which intermediate filter 5 reconstructs the time-varying power signal, which can then be processed in order to extract the data carried by the radio frequency signal.

Fig. 2 shows a phase locked loop according to the prior art.

It comprises means 6 for generating a reference frequency, which are connected to the input of a phase comparator 7. The means for generating the reference frequency may be a quartz oscillator or an oscillator of the MEMS (english acronym for "MicroElectroMechanical System", "MicroElectroMechanical systems") type.

The output of the phase comparator 7 is connected to a low pass filter 8, the output of the low pass filter 8 being connected to a charge pump 9. A Voltage-Controlled Oscillator VCO (acronym for "Voltage Controlled Oscillator") with reference numeral 10 is connected via its input to the charge pump 9 and via its output to the output of the phase locked loop 4 and to a frequency divider 11, which frequency divider 11 is connected to the input of the comparator 7.

The means 6 for generating a reference frequency transmit a signal at the reference frequency Fref. The phase comparator 7 determines the difference epsilon from the phase difference between the signal at the reference frequency Fref and the signal at the frequency Fs output from the frequency divider 11.

The error signal with the difference epsilon is then filtered with a low-pass filter 8 to remove the negative component therefrom.

The charge pump 9 generates a voltage V from the filtered signal so that the voltage-controlled oscillator 10 is controlled so as to output a signal whose frequency is substantially constant and included in a frequency range centered on a multiple of a reference frequency that depends on the division factor of the frequency divider 11.

The inventors have observed that the frequency shift of the signal received at the input of the filter 5 comprises, in addition to the component af inserted by the phase-locked loop, also a component already present in the received radio frequency signal.

Through studies, they observed that this component varies with the rotation of the TPMS transmitter due to the doppler effect. It should be remembered that the doppler effect is a shift in the frequency of the electromagnetic emissions due to the relative motion of the source with respect to the receiver.

It is therefore an object of the present invention to detect the onset of motion of a TPMS transmitter by determining the doppler-induced component in the signal transmitted by the TPMS transmitter. Thus, the accelerometer can be removed from such a TPMS transmitter while ensuring that the start of motion is detected.

As seen in the introduction, the TPMS transmitter comprises a wireless transmission system for communicating with a TPMS receiver connected to an onboard control unit of the motor vehicle.

Each TPMS transmitter experiences a circular motion due to its positioning in the wheel relative to the axis of the wheel, while the TPMS receiver remains in a fixed position in the vehicle. The circular motion experienced by the TPMS transmitter causes relative motion that is closer to the TPMS receiver for one half of the wheel rotation and further away from the TPMS receiver for the other half of the wheel rotation.

When the transmitter is close to the receiver, the transmit frequency undergoes a first frequency shift defined by the following equation:

(equation 1)

Wherein:

c: speed of light

Vs: speed of movement of the transmitter relative to the receiver

f: the frequency of the waves transmitted by the transmitter.

As the transmitter gets farther away from the receiver, the transmit frequency undergoes a second frequency shift defined by the equation:

(equation 2)

Therefore, the signal transmitted by the TPMS transmitter undergoes a periodic frequency shift depending on the rotational speed and the size of the vehicle.

By determining the simple presence of this additional frequency-shifted component, which is characteristic of the doppler effect and which is different from the component introduced by the phase-locked loop, it can therefore be determined that the TPMS transmitter is moving.

For this purpose, the signal at the input of the intermediate filter 5 is acquired.

Next, a fast fourier Transform FFT (english acronym for "fast fourier Transform") is performed on the signal output from the intermediate filter 5.

By way of illustration, fig. 3 shows the signal output from the intermediate filter 5, and fig. 4 shows the corresponding signal output from the FFT. In the latter signal, the occurrence of a periodic signal can be seen.

Fig. 5 shows the main steps of a method for determining the start of motion of a TPMS transmitter.

In a first step 20, the signal output from the intermediate filter is acquired.

In a second step 21, a fast fourier transform of the intermediate frequency signal is determined.

In a third step 22, the average value of the fast fourier transform of the intermediate frequency signal is determined for a preset duration. The preset duration is selected according to the duration of a data frame received from the TPMS transmitter, according to the sampling throughput of said frame and according to the time elapsed between the transmission of two consecutive frames. Those skilled in the art will appreciate that the detection of the presence of the frequency-shifted component requires a sufficient amount of data. In particular, the average of the fourier transform over a duration corresponding to the reception of a frame carrying data represents only a large amount of data. Thus, for a 10 ms frame transmitted every 100 ms and a sample throughput between 9.6 kb/s and 19.2 kb/s, it is believed that the data contained in at least one frame allows a significant mean value of the fast fourier transform to be obtained.

In a fourth step 23, it is determined whether there is a frequency deviation by comparing the instantaneous value of the fast fourier transform with the average value of the fast fourier transform. This may be done by determining whether the subtraction of the signals is non-zero. If this is not the case, the method restarts at a first step 20.

If this is the case, the method continues to a fifth step 24, in which it is determined whether the absolute value of the deviation amplitude is above a threshold value. If this is not the case, the method restarts at a first step 20.

If this is the case, the method continues with a sixth step 25 in which it is determined whether the deviation is periodic. If this is not the case, the method restarts at a first step 20.

If this is the case, the method proceeds to a seventh step 26 in which it is determined that the TPMS transmitter is moving. It is inferred therefrom that the vehicle is moving. If this is not the case, the method restarts at a first step 20.

The above method may be coupled with periodic monitoring of the tire condition, which is performed continuously at a preset frequency.

Since each data transmission of such monitoring is expensive in terms of energy of the battery-powered TPMS transmitter, multiple modes of operation are typically employed to conserve its energy. Each of these modes includes a transmission frequency and a modulation that conveys information. The operating modes are standardized and generally include at least one of a "park" mode, a "low consumption" mode, and a "drive" mode.

Therefore, it is basically necessary to detect the movement of the vehicle to change between the "low consumption" and "driving" operation modes.

In this case, the method described with reference to fig. 5 will be activated periodically when the TPMS transmitter is in "low consumption" mode in step 19. Detecting that the vehicle is moving at the end of step 26 allows the TPMS transmitter to switch to the "drive" mode of operation in step 27.