CN101947905A - Positioning transmit device and method of automobile tire temperature and pressure monitoring system - Google Patents

Abstract

The invention provides a positioning transmit device and method of an automobile tire temperature and pressure monitoring system (TPMS). The positioning transmit device comprises a microprocessor, two acceleration sensors, a tire temperature and pressure sensor, an ASK emitting chip and an antenna matching filter circuit which are arranged on the hub of an automobile tire, wherein the acceleration measuring axes of the acceleration sensor I and the acceleration sensor II coincides with the radial line of the hub, and the acceleration measuring axes and the radial line all point to the same direction. By using the device and method of the invention, the influence of metal components such as the tire steel nets and the automobile body on the radio-frequency signals sent by the transmit device of the TPMS can be effectively overcome. The principle of the invention is simple and is easy to realize, thus the data transmission quality of the TPMS can be increased and the transmission power of the transmit device in the tire can be reduced. Therefore, the bit error rate performance of the TPMS can be greatly improved and the market competition of the TPMS product can be increased.

Description

The location feedway and the method for motor tire temperature, pressure monitoring system

Technical field

The present invention relates to the data link of a kind of direct-type motor tire temperature, pressure wireless monitor system (TPMS).The present invention also relates to a kind of data transmission method of direct-type motor tire temperature, pressure wireless monitor system.

Background technology

Motor tire temperature, pressure monitoring system (TPMS) is most important to safe driving, and at present, TPMS mainly is divided into two types ^[1]: indirect type TPMS and direct-type TPMS.The indirect type TPMS rotating speed of ABS tire speed sensor measuring wheel tire, thus judge tire pressure, and accuracy and reliability are relatively poor.Direct-type TPMS system can monitor tire pressure and temperature when running car in real time automatically, can play the effect that gives warning in advance and guarantee traffic safety, therefore becomes the market mainstream gradually ^[2]Yet the temperature and pressure transmitter module of direct-type TPMS need be installed on inside tires, transmit tire information with wireless mode, be subjected to the screening effect of tire inner steel web and wheel hub, transmitter module and receiver module appear at the not enough failure-free problem of some tire location upper sensor data transmission often because of apart from each other when being used for full size vehicle, in order to address the above problem, the present invention proposes a kind of technical scheme of controlling transmitter module location emission in the tire, its control mechanism and system modeling method have been described in detail in detail, have provided concrete implementation algorithm.Location of the present invention launching technique can be improved the performance of TPMS product effectively.

List of references

[1] He Ren, Hu Qingxun, Xue Xiang. air pressure of automobile tire monitoring system development Overview. Chinese safe and scientific journal .2005,15 (10): 105-106;

[2] Korean is refined, Yin Shufei. based on the TPMS system design analysis .http of MPXY 8020 sensors: //www.aojauto.comhtml/TecEdge/086409053922566.shtml, 2008.06.04.

Summary of the invention

The object of the present invention is to provide a kind of location feedway of motor tire temperature, pressure monitoring system of the influence that can overcome the radiofrequency signal that hard wares such as tire steel mesh and vehicle body send the TPMS feedway effectively.The present invention also aims to provide a kind of location launching technique of motor tire temperature, pressure monitoring system.

The object of the present invention is achieved like this:

The composition of the location feedway of motor tire temperature, pressure monitoring system of the present invention comprises the microprocessor MCU on the wheel hub that is installed on motor tire, two acceleration pick-ups, tire temperature tyre pressure sensor, the ASK transmitting chip, the antenna matching filter circuit, microprocessor MCU is the SP30T chip, acceleration pick-up I and tire temperature tyre pressure sensor are that SP30T is the sheet inner sensor of microprocessor MCU, acceleration pick-up II is served as by the sheet inner sensor of another sheet SP30T, microprocessor MCU links to each other with acceleration pick-up II by the mode of duplexing serial communication and reads its acceleration information, the ASK transmitting chip is MAX7044, the antenna matching filter circuit is connected to form by 5 capacity cells and 2 inductance elements, and the acceleration analysis axis of acceleration pick-up I and acceleration pick-up II overlaps and point to same direction with the omnibearing line of wheel hub.

The location launching technique of motor tire temperature, pressure monitoring system

Step 1: initialization, microprocessor MCU is set works in the mode of waking up once every 4 minutes, change dormant state then over to;

Step 2:, then change step 3 over to if microprocessor MCU is waken up; Otherwise the continuation dormancy, wake-up waiting;

Step 3: read acceleration information from acceleration pick-up I and acceleration pick-up II, and calculate running speed v according to following formula ₁

$v_1=R\·\sqrt{({\mathrm{\α}}_A-{\mathrm{\α}}_B)/2r}$

Wherein, α _AAnd α _BRepresenting the data, the R that read from acceleration pick-up I and acceleration pick-up II respectively is that tire outline projection radius, r are projection radius at the bottom of the rim gutter;

Step 4: as speed of a motor vehicle v ₁When being higher than 30km/h, change step 5 over to, otherwise go back to step 2 and reenter dormant state;

Step 5: the acceleration information that reads according to step 3 calculates, and finds out when the position at prelocalization feedway place, changes step 6 then over to and specifies the transmitting site location;

Step 6: at first, utilize formula

Calculating forwards to from location feedway current location θ and specifies transmitting site θ ₀The required time, wherein,

When

The time must add 360 ° correct its on the occasion of;

Then, give the microprocessor time-delay t value of obtaining, and change step 7 over to;

Step 7:, then read tire temperature, tire pressure sensing data and give the MAX7044 chip with its coding framing and launch with the form of radiofrequency signal if the time-delay of t time arrives; Then, turn back to step 2 and reenter dormant state; Otherwise return step 7, check and delay time not.

The concrete steps that the described acceleration information that reads according to step 3 calculates, find out when the position at prelocalization feedway place are:

In the 1st step, three working cell a are set in microprocessor MCU ₁, a ₂, a ₃, and zero clearing;

The 2nd step, read data from acceleration pick-up I and acceleration pick-up II, promptly obtain α _AAnd α _B

In the 3rd step, calculate α=α _A+ α _B

In the 4th step, the α value is deposited in the working cell in the following order:

a ₂＝＞a ₁

a ₃＝＞a ₂

α＝＞a ₃

Wherein, symbol "=＞" is represented assignment operation;

In the 5th step, check a ₁＜0, a ₂≤ 0, a ₃Whether＞0 satisfy? if satisfy, then current location finds and is θ=270 °, finishes to search; Otherwise, change next step over to;

In the 6th step, check a ₁＞0, a ₂〉=0, a ₃Whether＜0 satisfy? if satisfy, then current location finds and is θ=90 °, finishes to search; Otherwise, returned for the 2nd step, continue to search.

Essence of the present invention is: by to TPMS feedway location, select the little position emission tire temperature tire pressure data of wheel hub steel mesh and car body screening effect, and then reach the effect that improves radio communication quality.This feedway location is that the acceleration/accel difference of utilizing the acceleration pick-up I that is installed in the vehicle tyre and acceleration pick-up II to measure realizes.

Effect intentionally of the present invention is: the method that has proposed to utilize the emission of acceleration pick-up Data Control TPMS feedway location and the estimation speed of a motor vehicle, after introducing the location launching technique, overcome the influence of the radiofrequency signal that hard wares such as tire steel mesh and vehicle body send the TPMS feedway effectively.Its principle simply is easy to realize, help to improve the data transmission quality of TPMS system and reduce the emissive power that is positioned over the feedway in the tire, make the bit error rate performance of TPMS obtain to improve greatly, and can receive the effect that increases the TPMS product market competitiveness.

Description of drawings

Fig. 1 TPMS location transmitter module theory of constitution block diagram;

Fig. 2 TPMS transmitter module circuit diagram;

The scheme of installation of Fig. 3 TPMS location feedway;

Fig. 4 searches the diagram of circuit of the current position of feedway, TPMS location;

Fig. 5 wheel schematic cross-section;

Total work diagram of circuit of Fig. 6 TPMS location feedway;

Fig. 7 wheel schematic cross-section;

The curve that Fig. 8 α changes with the tire rotational angle theta.

The specific embodiment

For example the present invention is done description in more detail below in conjunction with accompanying drawing:

In conjunction with Fig. 1, the location feedway of motor tire temperature, pressure monitoring system is by microprocessor MCU, acceleration pick-up, and tire temperature tyre pressure sensor, ASK transmitting chip, antenna matching filter circuit are formed.Wherein microprocessor MCU is the SP30T chip; Acceleration pick-up I and tire temperature tyre pressure sensor are the sheet inner sensor of SP30T (microprocessor MCU); Acceleration pick-up II is served as by the sheet inner sensor of another sheet SP30T, and microprocessor MCU is attached thereto by the mode of duplexing serial communication and reads acceleration information from it; The ASK transmitting chip is MAX7044; The antenna matching filter circuit is connected to form in mode shown in Figure 2 by 5 capacity cells and 2 inductance elements.

During work, microprocessor U1 reads acceleration measurement from acceleration pick-up I (sheet inner sensor) and acceleration pick-up II earlier, the speed of a motor vehicle of reruning algorithm and location algorithm carry out optimum transmit position calculation and location, control radio frequency chip U2 then and will launch with the form of radiofrequency signal from the tire temperature tire pressure that tire temperature tyre pressure sensor (the sheet inner sensor of microprocessor MCU) reads.

In conjunction with Fig. 2, the circuit bank of a kind of specific embodiment of the location feedway of motor tire temperature, pressure monitoring system of the present invention becomes:

Signal, the MSDA of acceleration pick-up II (being realized by SP30T) and MSCL signal wire (SW) are connected respectively to Signal, MSDA and the MSCL signal wire (SW) of the microprocessor MCU (being realized by SP30T) in the power circuit; The Data signal wire (SW) of microprocessor MCU is connected to the Data signal wire (SW) of ASK transmitting chip MAX7044; The output PAOUT of ASK transmitting chip MAX7044 (pin 4) is connected to the antenna matching filter circuit.

TPMS location transmitter module divides on the wheel hub 3 that two parts are installed on motor tire, and concrete installation site as shown in Figure 3.Among the figure, 1 (A point) is the installation site of acceleration pick-up I (power circuit part), and 2 (B points) are the installation site of acceleration pick-up II.Must guarantee during installation that the acceleration analysis axis of acceleration pick-up I and acceleration pick-up II overlaps and point to same direction with the omnibearing line of wheel hub.Among Fig. 44 is tire.

The emission of TPMS location realizes by carrying out the following step:

Step 1: initialization: microprocessor MCU (SP30T) is set works in the mode of waking up once every 4 minutes; Then, change dormant state over to.

Step 2:, then change step 3 over to if microprocessor MCU is waken up; Otherwise the continuation dormancy, wake-up waiting.

Step 3: read acceleration information from acceleration pick-up I and acceleration pick-up II, and calculate running speed v according to following formula ₁(principle is seen note 1)

${\mathrm{<figure-callout\; id="1"\; label="v"\; filenames="HSA00000220817400041.png"\; state="\{\{state\}\}">v</figure-callout>}}_1=R\&CenterDot;\sqrt{({\mathrm{\&alpha;}}_A-{\mathrm{\&alpha;}}_B)/2r}---\left(1\right)$

In the formula, α _AAnd α _BRepresent the data that read from acceleration pick-up I and acceleration pick-up II respectively; R is a tire outline projection radius; R is a projection radius at the bottom of the rim gutter.

Step 4: as speed of a motor vehicle v ₁When being higher than 30km/h, change step 5 over to, otherwise go back to step 2 and reenter dormant state.

Step 5: the acceleration information that reads according to step 3, find out the position (principle is seen note 2) at current TPMS transmitter module place by calculation process shown in Figure 4, then, change step 6 over to and specify the transmitting site location.

Step 6: at first, utilize formula (2) (principle is seen note 3) to calculate and forward appointment transmitting site θ to from location feedway current location θ (90 ° or 270 ° are determined by step 5) ₀(relevant with vehicle definite) the required time by experiment in advance

In the formula,

When

The time must add 360 ° correct its on the occasion of; α _A, α _BIdentical with the implication of r with formula (1).

Then, give the microprocessor time-delay t value of obtaining, and change step 7 over to.

Near step 7: if the time-delay of t time to (expression location feedway has arrived the appointment transmitting site), is then read tire temperature, tire pressure sensing data and given 7044 chips with its coding framing and launch with the form of radiofrequency signal; Then, turn back to step 2 and reenter dormant state; Otherwise return step 7, check and delay time not.

Note 1: speed of a motor vehicle calculating formula

Suppose that wheel rotates in the counterclockwise direction, as shown in Figure 7, center of circle O represents the wheel shaft axle center, and is that initial point is set up rectangular coordinate system XOY with O.Among the figure, the solid line cylindrical is represented the projection of tire outline, and radius is R, is v along the tangential speed of tire outline ₁Projection at the bottom of the circle expression rim gutter in the dotted line, radius is r, the tangential speed at the bottom of rim gutter is v ₂G is an acceleration due to gravity.Acceleration pick-up I in the TPMS feedway and acceleration pick-up II are placed in an A respectively and put the B place.The acceleration analysis axis of acceleration pick-up I and acceleration pick-up II overlaps and points to same direction with the omnibearing line of wheel hub.

Any time, the acceleration measurement at some A place is:

α _A＝g.cosθ+α _n (3)

The acceleration measurement at some B place is:

α _B＝g.cosθ-α _n (4)

In the formula, θ is an angle that the acceleration pick-up I at A place turns over along y axle positive dirction conter clockwise, and span is 0 °～360 °; α _nBe the centripetal acceleration that the wheel uniform circular motion causes, direction is pointed to center of circle O.

By centripetal acceleration α _n, the tangential speed v at the bottom of the rim gutter ₂, the relation at the bottom of the rim gutter between radius r:

${\mathrm{\&alpha;}}_n=\frac{{v_2}^2}{r}$

Can obtain v ₂For:

$v_2=\sqrt{{\mathrm{\&alpha;}}_{n}r}---\left(5\right)$

Know by (3) and (4):

α _n＝(α _A-α _B)/2

Substitution formula (5)

$v_2=\sqrt{({\mathrm{\&alpha;}}_A-{\mathrm{\&alpha;}}_B)\&CenterDot;r/2}---\left(6\right)$

Therefore, vehicle actual travel speed v ₁Can obtain into:

${\mathrm{<figure-callout\; id="1"\; label="v"\; filenames="HSA00000220817400041.png"\; state="\{\{state\}\}">v</figure-callout>}}_1=R\frac{v_2}{r}=R\&CenterDot;\sqrt{({\mathrm{\&alpha;}}_A-{\mathrm{\&alpha;}}_B)/2r}---\left(7\right)$

Note 2: definite principle of current TPMS feedway position

Formula in the note 1 (3) and (4) are got and, obtain the output of two acceleration pick-ups and be with the pass of tire corner:

α＝2g.cosθ (8)

The curve of reflection α～theta function relation is provided by Fig. 8.

As seen from Figure 8, when θ=90 ° and θ=270 °, α is to the mould maximum (being 2g) of the rate of change of θ, just, this moment, the difference of adjacent twice observed reading had highest resolution, thus these two positions as meticulous R point of searching the appointment transmitting site, the i.e. starting point of location algorithm.

Can see also that by Fig. 8 ° locate in θ=90, three observed readings in succession necessarily satisfy α 1＞0, α 2 〉=0, α 3＜0; ° locate in θ=270, three observed readings in succession necessarily satisfy α ' 1＜0, α ' 2≤0, α ' 3＞0; Therefore, can utilize above-mentioned feature to determine current TPMS transmitter module position (power circuit part), the promptly meticulous R point of specifying transmitting site of searching.

Note 3: the principle of determining to specify transmitting site

Suppose current TPMS transmitter module position at the θ place, the appointment transmitting site that needs positioning control is at θ ₀Place's (concrete vehicle is needed to be determined by experiment in advance) forwards θ to from the θ position ₀The angle that the position turned over is

(note: when

The time must add 360 ° correct its on the occasion of).

Know by Fig. 7, wheel rim girth C=2 π r, in the time, the distance that wheel rim passes through is at t:

$S={\&Integral;}_0^t{v}_2\mathrm{dt}$

Be without loss of generality, ignore the ground-surface relatively slip of wheel, and the motion of wheel is regarded as the resultant movement of the linear uniform motion on uniform circular motion and the horizontal direction, so put the tangential speed v of A ₂Size does not change in time, that is:

$S=v_2{\&Integral;}_0^{\mathrm{<figure-callout\; id="1"\; label="t"\; filenames="HSA00000220817400041.png"\; state="\{\{state\}\}">t</figure-callout>}}1\&CenterDot;\mathrm{dt}=v_{2}t$

So the angle that wheel rim turns in the t time is:

Substitution formula (9)

Therefore, after the method that provides with note 2 detects R point, obtain t by (10) earlier, behind the t time delays, transmitter module can arrive near the transmitting site of appointment again.

Claims (3)

1. the location feedway of a motor tire temperature, pressure monitoring system, it is characterized in that: comprise microprocessor MCU on the wheel hub that is installed on motor tire, two acceleration pick-ups, tire temperature tyre pressure sensor, the ASK transmitting chip, the antenna matching filter circuit, microprocessor MCU is the SP30T chip, acceleration pick-up I and tire temperature tyre pressure sensor are that SP30T is the sheet inner sensor of microprocessor MCU, acceleration pick-up II is served as by the sheet inner sensor of another sheet SP30T, microprocessor MCU links to each other with acceleration pick-up II by the mode of duplexing serial communication and reads its acceleration information, the ASK transmitting chip is MAX7044, the antenna matching filter circuit is connected to form by 5 capacity cells and 2 inductance elements, and the acceleration analysis axis of acceleration pick-up I and acceleration pick-up II overlaps and point to same direction with the omnibearing line of wheel hub.

2. the location launching technique of a motor tire temperature, pressure monitoring system is characterized in that:

Step 1: initialization, microprocessor MCU is set works in the mode of waking up once every 4 minutes, change dormant state then over to;

Step 2:, then change step 3 over to if microprocessor MCU is waken up; Otherwise the continuation dormancy, wake-up waiting;

Step 3: read acceleration information from acceleration pick-up I and acceleration pick-up II, and calculate running speed v according to following formula ₁

$v_1=R\&CenterDot;\sqrt{({\mathrm{\&alpha;}}_A-{\mathrm{\&alpha;}}_B)/2r}$

Wherein, α _AAnd α _BRepresenting the data, the R that read from acceleration pick-up I and acceleration pick-up II respectively is that tire outline projection radius, r are projection radius at the bottom of the rim gutter;

Step 4: as speed of a motor vehicle v ₁When being higher than 30km/h, change step 5 over to, otherwise go back to step 2 and reenter dormant state;

Step 5: the acceleration information that reads according to step 3 calculates, and finds out when the position at prelocalization feedway place, changes step 6 then over to and specifies the transmitting site location;

Step 6: at first, utilize formula

Calculating forwards to from location feedway current location θ and specifies transmitting site θ ₀The required time, wherein,

When

The time must add 360 ° correct its on the occasion of;

Then, give the microprocessor time-delay t value of obtaining, and change step 7 over to;

Step 7:, then read tire temperature, tire pressure sensing data and give the MAX7044 chip with its coding framing and launch with the form of radiofrequency signal if the time-delay of t time arrives; Then, turn back to step 2 and reenter dormant state; Otherwise return step 7, check and delay time not.

3. the location launching technique of motor tire temperature, pressure monitoring system according to claim 2 is characterized in that: the concrete steps that the described acceleration information that reads according to step 3 calculates, find out when the position at prelocalization feedway place are:

In the 1st step, three working cell a are set in microprocessor MCU ₁, a ₂, a ₃, and zero clearing;

The 2nd step, read data from acceleration pick-up I and acceleration pick-up II, promptly obtain α _AAnd α _B

In the 3rd step, calculate α=α _A+ α _B

In the 4th step, the α value is deposited in the working cell in the following order:

a ₂＝＞a ₁

a ₃＝＞a ₂

α＝＞a ₃

Wherein, symbol "=＞" is represented assignment operation;

In the 5th step, check a ₁＜0, a ₂≤ 0, a ₃Whether＞0 satisfy? if satisfy, then current location finds and is θ=270 °, finishes to search; Otherwise, change next step over to;

In the 6th step, check a ₁＞0, a ₂〉=0, a ₃Whether＜0 satisfy? if satisfy, then current location finds and is θ=90 °, finishes to search; Otherwise, returned for the 2nd step, continue to search.

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