A kind of automobile tire built-in braking characteristic sensing method
Technical field
The present invention relates to ride safety of automobile state sensing and Dynamic Monitoring, specifically be meant a kind of automobile tire built-in braking characteristic sensing method.
Background technology
Braking ability is an index of crucial importance of vehicle safety travel, and under automobile high-speed or non-high-speed travel state, braking ability is as the burst factor of safety, and its situation quality can influence the safety of travelling with lives and properties at any time.At present, the contact-sensing mode is adopted in the detection of automobile brake perfrmance usually, the restriction that is subjected to the velocity function scope and measures factors such as parts accuracy, its accuracy of detection, real-time are relatively poor, can't realize the sensing and the monitoring of automobile brake perfrmance under low speed and the fast state preferably.
Summary of the invention
The objective of the invention is to overcome the shortcoming and defect of above-mentioned prior art, provide a kind of accuracy of detection, real-time good, the automobile tire built-in braking characteristic sensing method that data-handling capacity is strong.
Purpose of the present invention is achieved through the following technical solutions: this automobile tire built-in braking characteristic sensing method, and its step comprises:
(1) the radial acceleration simulating signal of acceleration transducer unit output becomes digital signal through sampling A/D converter unit, delivers to central control microprocessor unit in the down trigger mode;
(2) central control microprocessor unit, external data storage unit carry out dynamically mark and storage piecemeal to signal;
(3) central control microprocessor unit carries out dynamic smoothing filtering piecemeal to the described signal waveform data that has stored;
(4) in the section of finishing the signal waveform data smoothing processing, enter before subsequent segment handles, central control microprocessor unit carries out the judgement that dynamic slope contrast and tire are braked the initial moment to signal waveform data in the section;
(5) from braking the initial moment, central control microprocessor unit stops the signal waveform data smoothing processing is outwards exported follow-up brake signal to outside receiving system by wireless mode, carries out the braking characteristic conversion process.
Must realize the present invention for better, be provided with three block address among the RAM of described external data storage unit, comprise main body block ADDRa, smooth block ADDRb, common block ADDRc, the configuration specification of described main body block ADDRa and smooth block ADDRb is identical, inside is divided into the multistage address equably, the section sequence number is marked with code name Ma and Mb respectively, initial sequence number is 1, maximum sequence number is P, 10<P<20, data sequence number in the section is marked with Na and Nb respectively, and initial sequence number is 1, and maximum sequence number is Q, 400<Q<800, the maximum allocated address value of main body block and smooth block is MAX=P * Q, and main body block ADDRa and smooth block ADDRb are marked with code name Wa and Wb respectively by the number of times of the topped storage of last volume, and initial number of times is 1, maximum times is H, 125<H<256, described common block ADDRc only is configured to be equivalent to the address capability of a section, and the initial pointer sequence number is 1.
It is described that dynamically mark and storage are meant that the sequence number Na of described radial acceleration digital signal carries out dynamically labeled since 1 in the interrupt service routine ring of central control microprocessor piecemeal, and simultaneously signal is stored among the main body block ADDRa successively, main body block ADDRa pointer increases 1 then, this moment main paragraph sequence number Ma=1, the multiplicity Wa=1 of main body block ADDRa, main paragraph sequence number Ma increases 1 after body data Na arrives maximum sequence number Q, and body data sequence number Na restores since 1 circulation again, formation has the multistage address date of identical data sequence number Na, and after main body block ADDRa pointer arrives maximal value MAX, signal stores on the address and rolls up, the topped storage of first address 1 beginning from main body block ADDRa, main paragraph sequence number Ma restores since 1 circulation, and the multiplicity Wa of main body block ADDRa increases 1, after multiplicity Wa arrived maximal value H, Wa restored since 1 circulation again.
Described dynamic smoothing filtering is meant the smooth manner that central control microprocessor unit adopts dynamic segment to lag behind, and is that processing unit is implemented dynamic smoothing filtering to remove burr and spike to the signal waveform data that stores with main paragraph sequence number Ma, and its step comprises:
(1) when determining the main paragraph sequence number when being increased to Ma=2, show that the storage of sampled data has entered the 2nd section, begin the canned data of the 1st section Ma=1 is carried out smoothing processing this moment;
(2) after the data point that the maximum sequence number Nb=Q of data is the center was smoothly finished, smooth section sequence number Mb increased 1, and data sequence number Nb restores for Nb=1, changes follow-up one section smoothing processing and backup over to;
(3) after the maximum sequence number of smooth section reached Mb=P, smooth scroll multiplicity Wb increased 1, and section sequence number Mb restores and is Mb=1, and data sequence number Nb recovery is Nb=1, and the smoothing processing circulation is carried out;
(4) after the topped maximum times of smooth scroll reaches Wb=H, on roll up multiplicity Wb and restore and to be Wb=1, a section sequence number Mb restores and is that Mb=1, data sequence number Nb restore and is Nb=1, smoothing processing is carried out again.
Described smoothing processing may further comprise the steps:
(1) when initial multiplicity Wb=1 and initial smooth section sequence number Mb=1, with smoothed data sequence number Nb=1 is that the center begins, from main body block ADDRa, extract the data point of 4 forward sequence numbers corresponding with the Nb sequence number, ask its totally 5 data point sums, be designated as S, getting its mean value is S ÷ 5, in order to replace the numerical value of this center sequence number data point, other is stored among the smooth block ADDRb, and circulation is performed until smoothed data sequence number Nb=5 as method, and the corresponding sequence number data point that changes step (2) over to continues and carries out;
(2) when multiplicity Wb ≠ 1, with smoothed data sequence number Nb=1 is that the center begins, from main body block ADDRa, extract the data point of corresponding with the Nb sequence number each 4 reverse and forward sequence numbers, ask its totally 9 data point sums, be designated as S, getting its mean value is S ÷ 9, and in order to replace the numerical value of this center sequence number data point, other is stored among the smooth block ADDRb.
Described dynamic slope contrast and tire are braked the judgement in the initial moment, and its step comprises:
(1) central control microprocessor unit is pressed the interior Wave data of this section of the smooth block address AD DRb of external data storage unit storage and is preset the spacing T that counts and be divided into a series of data point segments, obtains the dynamic slope absolute value L of each corresponding segment
(i), simultaneously the dynamic slope absolute value of each segment is deposited among the common block address AD DRc of external data storage unit in addition;
(2) the central control microprocessor unit dynamic slope absolute value situation of change of adjacent segment in the common block address AD DRc relatively is if in continuous some segments, the dynamic slope absolute value difference of adjacent segment is greater than preset threshold value T
h, promptly | L
(i)-L
(i+1)|>T
h, then with slope L
(i)The segment that is characterized just can be judged to be tire and brake the initial moment, and sets up the distinguishing mark of braking, otherwise, the segment mark Mb among the smooth block address AD DRb is increased 1, proceed follow-up one section smoothing processing process then.
Ultimate principle of the present invention: in the prior art, usually pick up the car the wheel maximum deceleration at the mean value of stablizing in the period, monitoring standard as braking ability, and retarded velocity can convert out by the relation of wheel linear velocity in theory, studies show that, the envelope shape of wheel radial acceleration signal and wheel linear velocity curve shape basically identical can be made for the numerical basis that follow-up braking characteristic converts and handles.The central control microprocessor unit of the present invention by being installed in automotive interior and being electrically connected mutually, acceleration transducer unit, the external data storage unit, sampling mould/transformation of variables unit, mark and storage are piecemeal carried out dynamically in sampling and the tire radial acceleration signal after digitizing, to the signal value of the averaging smoothing denoising filtering piecemeal that has stored, and then in section, ask for the variation slope of sigtnal interval point, compare the difference between each slope, judge that difference arrives the signaling point of preset threshold value, as the moment point that braking takes place, the follow-up signal that this moment point begins is outwards exported as the data of braking time interval.
The relative prior art of the present invention has following advantage and beneficial effect:
(1) by to the processing of the built-in radial acceleration signal of tire, obtains the relation of braking characteristic, for the monitoring of automobile brake perfrmance provides a kind of new approach;
(2) because the continuous sampling that will carry out acceleration signal to running automobile just can be guaranteed the servo response to braking procedure, among the present invention, the mark of acceleration signal, storage and processing all take the dynamic circulation mode of segmentation to carry out, and have solved the contradiction between quantity of information and the admittance ability;
(3) solved the dynamic vehicle braking by non-contacting flexible way decision problem has constantly taken place, and make sensor-based system only in of short duration period of braking just by the noncontact approach to the outside tires output data, save the energy consumption of tire built-in system to greatest extent.
Description of drawings
Fig. 1 is the hardware configuration synoptic diagram of tire built braking characteristic sensing method of the present invention;
Fig. 2 is the process flow diagram of tire radial acceleration sampling of the present invention and dynamically labeled storage;
Fig. 3 is the process flow diagram of tire radial acceleration signal dynamic smoothing of the present invention filtering;
Fig. 4 is that the dynamic slope contrast of the present invention is braked the process flow diagram of initial moment judgement with tire;
Fig. 5 is the radial acceleration signal waveform partial enlarged drawing of acceleration transducer unit output voltage conversion shown in Figure 1;
Fig. 6 is the synoptic diagram that tire is braked initial moment judgement;
Fig. 7 brakes initial moment radial acceleration (m/s from tire
2) with the time (s) concern synoptic diagram.
Embodiment
Below in conjunction with embodiment and accompanying drawing, the present invention is described in further detail, but embodiments of the present invention are not limited thereto.
Embodiment one
As shown in Figure 1, the hardware system that this automobile tire built-in braking characteristic sensing method adopts, comprise acceleration transducer unit 1, sampling mould/transformation of variables unit 2, central authorities control microprocessor unit 3, external data storage unit 4 is electrically connected composition mutually, and all be installed on the tire inner wheel hub, central authorities control microprocessor unit 3 is connected with external data storage unit 4 usefulness signal wires, and be connected with acceleration transducer unit 1 usefulness signal wire by sampling mould/transformation of variables unit 2, central control microprocessor unit 3 is also by output port and the wireless connections of outside tires receiving system.Wherein, acceleration transducer signals unit 1 adopts the ADXL190 type, and sampling D/A converting unit 2 adopts the AD7705 type, and central control microprocessor unit 3 adopts the P89LPC936 type, and external data storage unit 4 adopts the UPD43256 type.
This automobile tire built-in braking characteristic sensing method can adopt assembly language to work out each corresponding processing program, and its workflow comprises:
(1) the radial acceleration simulating signal of acceleration transducer unit output becomes digital signal through sampling A/D converter unit, delivers to central control microprocessor unit in the down trigger mode;
(2) central control microprocessor unit, the external data storage unit carries out dynamically mark and storage piecemeal to signal: three block address externally are set among the data storage unit R AM, be respectively main body block ADDRa, smooth block ADDRb and common block ADDRc, wherein the configuration specification of main body block ADDRa and smooth block ADDRb is identical, inside is divided into the multistage address equably, the section sequence number is marked with code name Ma and Mb respectively, initial sequence number is 1, maximum sequence number is P, 10<P<20, data sequence number in the section is marked with Na and Nb respectively, initial sequence number is 1, maximum sequence number is Q, 400<Q<800, and the maximum allocated address value of main body block and smooth block is MAX=P * Q, main body block ADDRa and smooth block ADDRb are marked with code name Wa and Wb respectively by the number of times of the topped storage of last volume, initial number of times is 1, and maximum times is H, 125<H<256, common block ADDRc only is configured to be equivalent to the address capability of a section, and the initial pointer sequence number is 1.
As shown in Figure 2, the sequence number Na of radial acceleration digital signal carries out dynamically labeled in the interrupt service routine ring of central control microprocessor since 1, and simultaneously signal is stored among the main body block ADDRa successively, main body block ADDRa pointer increases 1 then, this moment main paragraph sequence number Ma=1, the multiplicity Wa=1 of main body block ADDRa, main paragraph sequence number Ma increases 1 after body data Na arrives maximum sequence number Q, and body data sequence number Na restores since 1 circulation again, formation has the multistage address date of identical data sequence number Na, and after main body block ADDRa pointer arrives maximal value MAX, signal stores on the address and rolls up, the topped storage of first address 1 beginning from main body block ADDRa, main paragraph sequence number Ma restores since 1 circulation, and the multiplicity Wa of main body block ADDRa increases 1, and after multiplicity Wa arrived maximal value H, Wa restored since 1 circulation again.
(3) as shown in Figure 3, central control microprocessor unit carries out dynamic smoothing filtering piecemeal to the described signal waveform data that has stored:
1, when determining the main paragraph sequence number when being increased to Ma=2, the storage that shows sampled data has entered the 2nd section, begin the canned data of the 1st section Ma=1 is carried out smoothing processing this moment, be divided into (a) and (b) two kinds of estimate of situations: (a) when initial multiplicity Wb=1 and initial smooth section sequence number Mb=1, with smoothed data sequence number Nb=1 is that the center begins, from main body block ADDRa, extract the data point of 4 forward sequence numbers corresponding with the Nb sequence number, ask its totally 5 data point sums, be designated as S, getting its mean value is S ÷ 5, in order to replace the numerical value of this center sequence number data point, other is stored among the smooth block ADDRb, circulation is performed until smoothed data sequence number Nb=5 as method, and the corresponding sequence number data point that changes situation (b) over to continues and carries out; (b) when multiplicity Wb ≠ 1, with smoothed data sequence number Nb=1 is that the center begins, from main body block ADDRa, extract the data point of corresponding with the Nb sequence number each 4 reverse and forward sequence numbers, ask its totally 9 data point sums, be designated as S, getting its mean value is S ÷ 9, and in order to replace the numerical value of this center sequence number data point, other is stored among the smooth block ADDRb;
2, after the data point that the maximum sequence number Nb=Q of data is the center was smoothly finished, smooth section sequence number Mb increased 1, and data sequence number Nb restores for Nb=1, changes follow-up one section smoothing processing and backup over to;
3, after the maximum sequence number of smooth section reached Mb=P, smooth scroll multiplicity Wb increased 1, and section sequence number Mb restores and is Mb=1, and data sequence number Nb recovery is Nb=1, and the smoothing processing circulation is carried out; (4) after the topped maximum times of smooth scroll reaches Wb=H, on roll up multiplicity Wb and restore and to be Wb=1, a section sequence number Mb restores and is that Mb=1, data sequence number Nb restore and is Nb=1, smoothing processing is carried out again.
(4) as shown in Figure 4, in the section of finishing the signal waveform data smoothing processing, enter before subsequent segment handles, central control microprocessor unit carries out the judgement that dynamic slope contrast and tire are braked the initial moment to signal waveform data in the section:
1, Wave data in this section of smooth block address AD DRb is pressed preset the spacing T that counts and be divided into a series of data point segments, by the following close dynamic slope absolute value L that calculates each corresponding segment that seemingly asks
(i):
i=1,2,3,Λ,m,m≤Q/T
Wherein, f
nBe the sensor sample frequency, j and k represent the starting point sequence number and the terminal point sequence number of this segment, d respectively
jAnd d
kRepresent corresponding data point numerical value, i is the sequence number of data segment, and Q is the data sequence number maximal value, simultaneously each little slope over 10 is deposited among the common block address AD DRc in addition;
2, compare the slope variation situation of adjacent segment in the common block address AD DRc, difference is greater than preset threshold value T
h, and there is following relation in this situation in continuous some segments:
|L
(i)-L
(i+1)|>T
h
Then with slope L
(i)The segment that is characterized begins to be judged to be the initial moment of tire braking and to set up the distinguishing mark of braking, otherwise, the segment mark Mb among the smooth block address AD DRb is increased 1, proceed follow-up one section smoothing processing process then;
(3) from the initial moment of braking, central control microprocessor unit stops the smoothing processing process to data, and the follow-up brake signal that is stored among the main body block ADDRa is outwards exported to outside receiving system, carries out the braking characteristic conversion process.
Fig. 5 is the radial acceleration signal waveform partial enlarged drawing of acceleration transducer unit 1 output voltage conversion, and as shown in Figure 5, horizontal ordinate is sampling number (n), and ordinate is radial acceleration (m/s
2), because acceleration transducer is subjected to the influence of gravity in vertical direction,, also be mingled with interference components such as spike simultaneously so the radial acceleration signal of output can present the alternation fluctuation status in cycle with the rotation of tire, need carry out corresponding smoothing processing.
Fig. 6 is the processing synoptic diagram that braking is judged constantly behind the smoothing denoising, and as shown in Figure 7, wherein ar represents the radial acceleration waveform, dotted line envelope and linear velocity v basically identical, and the state of horizontal direction at the uniform velocity travelling, vergence direction is the state of braking deceleration; Get each segment that spaced points is divided at vergence direction, the difference of its adjacent slope is compared with the difference of the adjacent slope of each segment of getting spaced points in the horizontal direction and being divided into, its intensity of variation obviously increases, when difference has surmounted the boundary of preset threshold value, as the t2 among the figure constantly, decidable is that braking time interval begins.
Fig. 7 brakes initial moment radial acceleration (m/s from tire
2) with the time (s) concern synoptic diagram, expression after the concrete conversion of model acceleration transducer output voltage to acceleration ratio, a kind of radial acceleration (m/s that begins constantly from braking
2) with the relation of time (s), outwards output offers the usefulness of outside receiving system as the braking characteristic conversion process.
As mentioned above, just can realize the present invention preferably.