CN109782010A - A kind of vehicle speed measuring method and speed measuring equipment based on acceleration transducer - Google Patents
A kind of vehicle speed measuring method and speed measuring equipment based on acceleration transducer Download PDFInfo
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Abstract
The present invention provides a kind of vehicle speed measuring methods based on acceleration transducer, its easy to implement, at low cost, convenient for safeguarding, high reliablity, and require no knowledge about vehicle initial velocity, it can calculating speed at any time, accuracy is high, acceleration transducer is placed at the position in the axle center of wheel, using the axle center of wheel as origin, X-axis and Y-axis are established in the perpendicular where acceleration transducer, acquires acceleration information；Acceleration transducer data are read, to any carry out low-pass filtering and high-pass filtering in the acceleration information on the acceleration information and Y-axis in obtained X-axis, is then smoothed, is obtained in sinuous acceleration information using sliding mean filter；Search wave crest and trough number and each wave crest in obtained acceleration information, trough and position in data calculate vehicle wheel rotational speed, speed is calculated by vehicle wheel rotational speed.In addition, the present invention also provides a kind of vehicle speed measuring equipment based on acceleration transducer.
Description
Technical field
The present invention relates to vehicle speed measuring technical field, specially a kind of vehicle speed measuring method based on acceleration transducer and
Speed measuring equipment.
Background technique
In certain fields, such as in large chemical plant, to ensure plant area's traffic safety, plant area's traffic order is safeguarded,
The generation to try to forestall traffic accidents, needs to carry out working truck fine-grained management, for example, to the driving speed management of different work vehicle,
Allow working region management, driver's management etc..Wherein, driving speed management is most one of basic function.It realizes to vehicle speed
The management of degree requires accurately to measure car speed first.Traditional Vehicle Velocity Measurement Method specifically includes that coil
It tests the speed, video detection, microwave radar, sonic detection, laser detection, radar velocity measurement, GPS test the speed, the original of these speed-measuring methods
Reason and shortcoming are as follows:
1) time that coil tests the speed according to vehicle Jing Guo parallel coil tests the speed.The shortcomings that detection method is to be ground
Inbuilt induction coil it is great in constructing amount, road surface once change if need circle of sunkening cord again, in addition high latitude thaws phase and low latitudes summer
Season road surface and the bad place of pavement quality be all huge to the maintenance work of coil.
2) video frequency speed-measuring calculates car speed by the analysis to continuous videos image.The advantages of this method is the road Bu Shou
The limitation of face situation, installation does not need to destroy road surface, or induction coil is buried under road surface.The disadvantage is that the identification to move vehicle has
Certain difficulty, video technique are influenced by light, weather.
3) radar velocity measurement obtains the movement velocity of testee according to the calculating to the back wave frequency shift amount received, should
Method needs
4) sound wave, which tests the speed, issues ultrasonic wave by ultrasonic transmission device, and time difference when ultrasonic wave is connected to according to receiver
Calculate car speed.The disadvantage is that service life is at most also with regard to several weeks in the great adverse circumstances of dust.
5) laser velocimeter issues laser by laser beam emitting device, calculates vehicle according to the time difference of the reflected light received
A vehicle may be implemented in speed, this method, the disadvantage is that laser injures greatly human eye, safety is not high, generally requires manual behaviour
Make.
6) GPS, which tests the speed, carries out car speed vehicle by GPS positioning signal, the disadvantage is that it is good to can be used only in GPS signal
Place, the vehicle speed measuring error that furthermore GPS runs low speed is big.
7) acceleration transducer integral tests the speed using linear acceleration sensors, acquires vehicle acceleration, to acceleration into
Row integral calculation speed, the disadvantage is that being to need to know initial velocity, and cumulative errors are big.
In addition, the above speed-measuring method requires to install corresponding speed measuring equipment on road greatly, equipment manufacturing cost is at high cost, and
And additional equipment management cost can be also introduced, therefore, these methods are more suitable for fixed road vehicle and test the speed, for area
The vehicle speed detection management application of domain property, such as the driving speed management in chemical plant, the above speed-measuring method are all not applicable.
Summary of the invention
In view of the above-mentioned problems, being easy to real the present invention provides a kind of vehicle speed measuring method based on acceleration transducer
Apply, be at low cost, is convenient for safeguarding, high reliablity, and requiring no knowledge about vehicle initial velocity, can calculating speed at any time, accuracy
Height is particularly suitable for regional vehicle speed detection management, in addition, the present invention also provides a kind of based on acceleration transducer
Vehicle speed measuring equipment.
Its technical solution is such that a kind of vehicle speed measuring method based on acceleration transducer, which is characterized in that including
Following steps:
Step 1: acceleration transducer being placed at the position in the axle center of wheel, using the axle center of wheel as origin, accelerated
Perpendicular where degree sensor establishes X-axis and Y-axis, and Z axis is arranged perpendicular to the perpendicular where acceleration transducer, leads to
Acceleration transducer is crossed, acceleration information is acquired；
Step 2: reading acceleration transducer data, obtain the acceleration degree on the acceleration information and Y-axis in X-axis
According to, to any carry out low-pass filtering and high-pass filtering in the acceleration information on the acceleration information and Y-axis in X-axis,
Then it is smoothed, is obtained in sinuous acceleration information using sliding mean filter；
Step 3: wave crest and trough number and each wave crest, trough in acceleration information obtained in finding step 2
And the position in data calculates vehicle wheel rotational speed, by vehicle wheel rotational speed calculates speed.
Further, step 2 the following steps are included:
Step 201: the collected acceleration transducer initial data of acceleration transducer being stored in buffer, buffer
Length according to acceleration transducer sample rate and it is required test the speed range determine；
Step 202: low-pass filtering is carried out to the X-axis acceleration information in buffer, is indicated with following formula:
XLPF_current=α * XRAW_current+ (1- α) * XLPF_previous
Wherein, XLPF_current is this X-axis low-pass filtering data；XRAW_current is the original of this X-axis sampling
Beginning data；XLPF_previous is last X-axis low-pass filtering data；α is low-pass filtering coefficient, 0 < α < 1, α=t/ (t+
dT)；T is filter temporal constant, is the unitary sampling time of acceleration transducer, dT is sample frequency；
Step 203: high-pass filtering being carried out to the X-axis acceleration information in the buffer obtained after step 202, with following public affairs
Formula indicates:
XHPF_current=XRAW_current-XLPF_current
Wherein, XHPF_current is this X-axis high-pass filtering data, and XLPF_current is this X-axis low-pass filtering
Data, XRAW_current are the initial data of this X-axis sampling；
Step 204: the data obtained after step 203 being smoothed using sliding mean filter, are obtained in sine
Wavy acceleration information.
Further, step 3 the following steps are included:
Step 301: the first-order difference of acceleration information obtained in step 2 is calculated, formula is expressed as:
Diff_Buffer [i]=Buffer [i+1]-Buffer [i]
Wherein, i ∈ 1,2 ..., N-1, N are the length of buffer；
Step 302: first-order difference data Diff_Buffer is carried out taking symbolic operation, is expressed as formula:
Trend_Buffer=sign (Diff_Buffer)
It is expressed as traversal first-order difference data Diff_Buffer, if Diff_Buffer [i] > 0, Trend_Buffer
[i]=1；If Diff_Buffer < 0, Trend_Buffer [i]=- 1, otherwise Trend_Buffer [i]=0；
Step 303: inverted order traverses Trend_Buffer, if Trend_Buffer [i]=0 and Trend_Buffer [i+
1] > 0, then Trend_Buffer [i]=1；If Trend_Buffer [i]=0 and Trend_Buffer [i+1] < 0,
Trend_Buffer [i]=- 1；
Step 304: calculating the first-order difference of Trend_Buffer, as Diff_Trend_Buffer, be expressed as public affairs
Formula:
Diff_Trend_Buffer [i]=Trend_Buffer [i+1]-Trend_Buffer [i]
Wherein, i ∈ 1,2 ..., N-1, N are the length of buffer；
Step 305: Diff_Trend_Buffer obtained in traversal 304, if Diff_Trend_Buffer [i]=-
2, then i+1 is a peak value position, and corresponding peak value is Buffer [i+1]；If Diff_Trend_Buffer [i]=2, i+1
For a valley position, corresponding trough is Buffer [i+1]；
Step 306: wave crest, the trough found out is screened, and removes the error result as caused by data dithering, will
Final Wave crest and wave trough lookup result, the position of number and each Wave crest and wave trough including Wave crest and wave trough in a buffer are protected
It deposits；
Step 307: wave crest, the trough lookup result screened according to 306 calculates vehicle wheel rotational speed rpm, is expressed as
Formula:
Rpm=(top_cnt-1) * SAMPLE_RATE/ (top_position [top_cnt-1]-top_position
[0])
Wherein, top_cnt is the wave crest number in buffer, and SAMPLE_RATE is the sampling rate of acceleration transducer,
Top_position [i] is position of i-th of wave crest in Buffer, and top_position [0] is the significant wave screened
First of peak, top_position [top_cnt-1] are the last one of the Valid peak screened；
Step 308: vehicle velocity V X-HPF is calculated according to vehicle wheel rotational speed rpm and radius of wheel:
VX-HPF=rpm*2 π r, wherein r is radius of wheel.
Further, step 2 the following steps are included:
Step 201: the collected acceleration transducer initial data of acceleration transducer being stored in buffer, buffer
Length according to sensor sample rate and it is required test the speed range determine；
Step 202: low-pass filtering is carried out to the Y-axis acceleration information in buffer, is indicated with following formula:
YLPF_current=α * YRAW_current+ (1- α) * YLPF_previous
Wherein, YLPF_current is this Y-axis low-pass filtering data；YRAW_current is the original of this Y-axis sampling
Beginning data；YLPF_previous is last Y-axis low-pass filtering data；α is low-pass filtering coefficient, 0 < α < 1, α=t/ (t+
dT)；T is filter temporal constant, is the unitary sampling time of acceleration transducer, dT is sample frequency；
Step 203: high-pass filtering being carried out to the Y-axis acceleration information in the buffer obtained after step 202, with following public affairs
Formula indicates:
YHPF_current=YRAW_current-YLPF_current
Wherein, YHPF_current is this Y-axis high-pass filtering data, and YLPF_current is this Y-axis low-pass filtering
Data, YRAW_current are the initial data of this Y-axis sampling；
Step 204: the data obtained after step 203 being smoothed using sliding mean filter, are obtained in sine
Wavy acceleration information.
Further, step 3 the following steps are included:
Step 301: the first-order difference of acceleration information obtained in step 2 is calculated, formula is expressed as:
Diff_Buffer [i]=Buffer [i+1]-Buffer [i]
Wherein, i ∈ 1,2 ..., N-1, N are the length of buffer；
Step 302: first-order difference data Diff_Buffer is carried out taking symbolic operation, is expressed as formula:
Trend_Buffer=sign (Diff_Buffer)
It is expressed as traversal first-order difference data Diff_Buffer, if Diff_Buffer [i] > 0, Trend_Buffer
[i]=1；If Diff_Buffer < 0, Trend_Buffer [i]=- 1, otherwise Trend_Buffer [i]=0；
Step 303: inverted order traverses Trend_Buffer, if Trend_Buffer [i]=0 and Trend_Buffer [i+
1] > 0, then Trend_Buffer [i]=1；If Trend_Buffer [i]=0 and Trend_Buffer [i+1] < 0,
Trend_Buffer [i]=- 1；
Step 304: calculating the first-order difference of Trend_Buffer, as Diff_Trend_Buffer, be expressed as public affairs
Formula:
Diff_Trend_Buffer [i]=Trend_Buffer [i+1]-Trend_Buffer [i]
Wherein, i ∈ 1,2 ..., N-1, N are the length of buffer；
Step 305: Diff_Trend_Buffer obtained in traversal 304, if Diff_Trend_Buffer [i]=-
2, then i+1 is a peak value position, and corresponding peak value is Buffer [i+1]；If Diff_Trend_Buffer [i]=2, i+1
For a valley position, corresponding trough is Buffer [i+1]；
Step 306: wave crest, the trough found out is screened, and removes the error result as caused by data dithering, will
Final Wave crest and wave trough lookup result, the position of number and each Wave crest and wave trough including Wave crest and wave trough in a buffer are protected
It deposits；
Step 307: wave crest, the trough lookup result screened according to step 306 calculates vehicle wheel rotational speed rpm, is expressed as
Following formula:
Rpm=(top_cnt-1) * SAMPLE_RATE/ (top_position [top_cnt-1]-top_position
[0])
Wherein, top_cnt is the wave crest number in buffer, and SAMPLE_RATE is the sampling rate of acceleration transducer,
Top_position [i] is position of i-th of wave crest in Buffer, and top_position [0] is the significant wave screened
First of peak, top_position [top_cnt-1] are the last one of the Valid peak screened；
Step 308: vehicle velocity V Y-HPF is calculated according to vehicle wheel rotational speed rpm and radius of wheel:
VY-HPF=Rpm*2 π r, wherein r is radius of wheel.
Further, the condition that wave crest, trough are screened is the physical features of wave crest, trough, comprising:
A) absolute value of acceleration value is greater than 0.5g；
B) wave crest, trough interval are greater than minimum interval, and minimum interval is by sensor sample rate and maximum is allowed to test the speed range
It determines；
C) trough is located between two spikes, and wave crest is located between two troughs.
Further, sample frequency is set as FsampleHz, maximum test the speed range V km/h, then minimum interval
Intervalmin=3.6* π * R*Fsample/V sampled point.
Further, step 4: the second acceleration transducer being set on wheel, is measured by the second acceleration transducer
Speed calibrates the speed that step 3 obtains.
Further, step 4 comprising the following specific steps
Step 410: the second acceleration transducer being placed at the position that the axle center apart from wheel is R1, in vertical plane
Coordinate system is established, using the axle center of wheel as origin, Y-axis is directed toward axle center along the vertical direction, and X-direction is vertical with Y direction；
Step 420: acceleration information being read by acceleration transducer, passes through the acceleration a of Y-axisYTurn to calculate wheel
Fast VY-LPF, is expressed as formula:
aIt is centripetal=aY=ω2* R1=VY-LPF2/R22*R1
Wherein, it is centripetal acceleration that a is centripetal, and ω is angular speed of wheel, and V is wheel linear velocity, and R1 is acceleration transducer
Distance apart from axis wheel, R2 are radius of wheel, calculate vehicle wheel rotational speed by the centripetal acceleration of Y-axis, obtain vehicle velocity V Y-
LPF；
Step 430: acceleration information being read by acceleration transducer, obtains the acceleration degree of X-axis；To adding in X-axis
Speed data carries out low-pass filtering and high-pass filtering, is then smoothed, is obtained in sine wave using sliding mean filter
The acceleration information of shape；Search the wave crest and trough number and each wave crest, trough and in data in acceleration information
Position calculates vehicle wheel rotational speed, passes through vehicle wheel rotational speed and calculates vehicle velocity V X-LPF；
Step 440: the speed that step 3 obtains being calibrated by vehicle velocity V X-LPF and vehicle velocity V Y-LPF, is obtained final
Vehicle velocity V final sets thresholding VTH, VTH=(2*G*R2 2*R1) 1/2=(2*9.8*R2 2*R1)1/2；
As VY-LPF < VTH, the result that finally tests the speed Vfinal=VX-LPF；
As VY-LPF >=VTH, the result that finally tests the speed Vfinal=(VX-HPF+VY-LPF)/2 or Vfinal=
(VY-HPF+VY-LPF)/2。
Further, step 430 is specific as follows:
Step 4301: the collected acceleration transducer initial data of the second acceleration transducer is stored in buffer,
The length of buffer is determined according to the second acceleration transducer sample rate and the required range that tests the speed；
Step 4302: low-pass filtering is carried out to the X-axis acceleration information in buffer, is indicated with following formula:
XLPF_current=α * XRAW_current+ (1- α) * XLPF_previous
Wherein, XLPF_current is this X-axis low-pass filtering data；XRAW_current is the original of this X-axis sampling
Beginning data；XLPF_previous is last X-axis low-pass filtering data；α is low-pass filtering coefficient, 0 < α < 1, α=t/ (t+
dT)；T is filter temporal constant, is the unitary sampling time of acceleration transducer, dT is sample frequency；
Step 4303: high-pass filtering being carried out to the X-axis acceleration information in the buffer obtained after step 4302, with as follows
Formula indicates:
XHPF_current=XRAW_current-XLPF_current
Wherein, XHPF_current is this X-axis high-pass filtering data, and XLPF_current is this X-axis low-pass filtering
Data, XRAW_current are the initial data of this X-axis sampling；
Step 4304: the data obtained after step 4303 being smoothed using sliding mean filter, are obtained in just
The wavy acceleration information of string；
Step 4305: the first-order difference of acceleration information obtained in step 4304 is calculated, formula is expressed as:
Diff_Buffer [i]=Buffer [i+1]-Buffer [i]
Wherein, i ∈ 1,2 ..., N-1, N are the length of buffer；
Step 4306: first-order difference data Diff_Buffer is carried out taking symbolic operation, is expressed as formula:
Trend_Buffer=sign (Diff_Buffer)
It is expressed as traversal first-order difference data Diff_Buffer, if Diff_Buffer [i] > 0, Trend_Buffer
[i]=1；If Diff_Buffer < 0, Trend_Buffer [i]=- 1, otherwise Trend_Buffer [i]=0；
Step 4307: inverted order traverses Trend_Buffer, if Trend_Buffer [i]=0 and Trend_Buffer [i+
1] > 0, then Trend_Buffer [i]=1；If Trend_Buffer [i]=0 and Trend_Buffer [i+1] < 0,
Trend_Buffer [i]=- 1；
Step 4308: calculating the first-order difference of Trend_Buffer, as Diff_Trend_Buffer, be expressed as
Formula:
Diff_Trend_Buffer [i]=Trend_Buffer [i+1]-Trend_Buffer [i]
Wherein, i ∈ 1,2 ..., N-1, N are the length of buffer；
Step 4309: Diff_Trend_Buffer obtained in traversal step 4308, if Diff_Trend_Buffer
[i]=- 2, then i+1 is a peak value position, and corresponding peak value is Buffer [i+1]；If Diff_Trend_Buffer [i]=
2, then i+1 is a valley position, and corresponding trough is Buffer [i+1]；
Step 4310: wave crest, the trough found out is screened, and removes the error result as caused by data dithering,
By final Wave crest and wave trough lookup result, the position of number and each Wave crest and wave trough including Wave crest and wave trough in a buffer is protected
It deposits；
Step 4311: wave crest, the trough lookup result screened according to step 4310 calculates vehicle wheel rotational speed rpm, indicates
For following formula:
Rpm=(top_cnt-1) * SAMPLE_RATE/ (top_position [top_cnt-1]-top_position
[0])
Wherein, top_cnt is the wave crest number in buffer, and SAMPLE_RATE is the sampling rate of acceleration transducer,
Top_position [i] is position of i-th of wave crest in Buffer, and top_position [0] is the significant wave screened
First of peak, top_position [top_cnt-1] are the last one of the Valid peak screened；
Step 4312: vehicle velocity V X-LPF is calculated according to vehicle wheel rotational speed rpm and radius of wheel:
VX-LPF=rpm*2 π r, wherein r is radius of wheel.
A kind of vehicle speed measuring equipment based on acceleration transducer, which is characterized in that MCU, acceleration including communication connection
Sensor, bluetooth are spent, the acceleration transducer is used to acquire the acceleration information of vehicle, and the MCU is used for acceleration degree
According to being handled, extraction rate metrical information, calculating speed as a result, and will be tested the speed result broadcast by the bluetooth, further include
Battery, for powering.
Vehicle speed measuring method based on acceleration transducer of the invention does not need fixed the testing the speed of installation on road and sets
It is standby, directly velometer is mounted on wheel, that is, can measure car speed, this method is at low cost, it is easy to implement, convenient for safeguarding,
High reliablity, and algorithm requires no knowledge about vehicle initial velocity, calculating speed, accuracy height can be particularly suitable for area at any time
The vehicle speed detection management of domain property, the vehicle speed measuring equipment of the invention based on acceleration transducer is easy to install and use, convenient
Communication.
Detailed description of the invention
Fig. 1 is the schematic diagram of the establishment of coordinate system of the vehicle speed measuring method based on acceleration transducer of specific embodiment 1；
Fig. 2 is the schematic diagram of the establishment of coordinate system of the vehicle speed measuring method based on acceleration transducer of specific embodiment 2；
Fig. 3 is the schematic diagram of acceleration information obtained in step 2；
Fig. 4 is the frame diagram of speed measuring equipment of the invention.
Specific embodiment
Specific embodiment 1:
See Fig. 1, a kind of vehicle speed measuring method based on acceleration transducer of the invention, comprising the following steps:
Step 1: acceleration transducer 1 being placed at the position in the axle center of wheel, using the axle center of wheel as origin, accelerated
Perpendicular where degree sensor establishes X-axis and Y-axis, and Z axis is arranged perpendicular to the perpendicular where acceleration transducer, leads to
Acceleration transducer is crossed, acceleration information is acquired；
Step 2: reading acceleration transducer data, obtain the acceleration degree on the acceleration information and Y-axis in X-axis
According to, to any carry out low-pass filtering and high-pass filtering in the acceleration information on the acceleration information and Y-axis in X-axis,
Then it is smoothed, is obtained in sinuous acceleration information using sliding mean filter；
Step 3: wave crest and trough number and each wave crest, trough obtained in searching 2 in acceleration information and
Position in data calculates vehicle wheel rotational speed, calculates speed by vehicle wheel rotational speed.
Using the acceleration information in X-axis as foundation, step 2 the following steps are included:
Step 201: the collected acceleration transducer initial data of acceleration transducer being stored in buffer, buffer
Length according to acceleration transducer sample rate and it is required test the speed range determine；
Step 202: low-pass filtering is carried out to the X-axis acceleration information in buffer, is indicated with following formula:
XLPF_current=α * XRAW_current+ (1- α) * XLPF_previous
Wherein, XLPF_current is this X-axis low-pass filtering data；XRAW_current is the original of this X-axis sampling
Beginning data；XLPF_previous is last X-axis low-pass filtering data；α is low-pass filtering coefficient, 0 < α < 1, α=t/ (t+
dT)；T is filter temporal constant, is the unitary sampling time of acceleration transducer, dT is sample frequency；
Step 203: high-pass filtering being carried out to the X-axis acceleration information in the buffer obtained after step 202, with following public affairs
Formula indicates:
XHPF_current=XRAW_current-XLPF_current
Wherein, XHPF_current is this X-axis high-pass filtering data, and XLPF_current is this X-axis low-pass filtering
Data, XRAW_current are the initial data of this X-axis sampling；
Step 204: the data obtained after step 203 being smoothed using sliding mean filter, are obtained in sine
Wavy acceleration information, it is seen that Fig. 3.
Step 3 the following steps are included:
Step 301: the first-order difference of acceleration information obtained in step 2 is calculated, formula is expressed as:
Diff_Buffer [i]=Buffer [i+1]-Buffer [i]
Wherein, i ∈ 1,2 ..., N-1, N are the length of buffer；
Step 302: first-order difference data Diff_Buffer is carried out taking symbolic operation, is expressed as formula:
Trend_Buffer=sign (Diff_Buffer),
It is expressed as traversal first-order difference data Diff_Buffer, if Diff_Buffer [i] > 0, Trend_Buffer
[i]=1；If Diff_Buffer < 0, Trend_Buffer [i]=- 1, otherwise Trend_Buffer [i]=0；
Step 303: inverted order traverses Trend_Buffer, if Trend_Buffer [i]=0 and Trend_Buffer [i+
1] > 0, then Trend_Buffer [i]=1；If Trend_Buffer [i]=0 and Trend_Buffer [i+1] < 0,
Trend_Buffer [i]=- 1；
Step 304: calculating the first-order difference of Trend_Buffer, as Diff_Trend_Buffer, be expressed as public affairs
Formula:
Diff_Trend_Buffer [i]=Trend_Buffer [i+1]-Trend_Buffer [i]
Wherein, i ∈ 1,2 ..., N-1, N are the length of buffer；
Step 305: Diff_Trend_Buffer obtained in traversal 304, if Diff_Trend_Buffer [i]=-
2, then i+1 is a peak value position, and corresponding peak value is Buffer [i+1]；If Diff_Trend_Buffer [i]=2, i+1
For a valley position, corresponding trough is Buffer [i+1]；
Step 306: wave crest, the trough found out is screened, and removes the error result as caused by data dithering, will
Final Wave crest and wave trough lookup result, the position of number and each Wave crest and wave trough including Wave crest and wave trough in a buffer are protected
It deposits, the condition that wave crest, trough are screened is the physical features of wave crest, trough, comprising:
A) absolute value of acceleration value is greater than 0.5g；
B) wave crest, trough interval are greater than minimum interval, and minimum interval is by sensor sample rate and maximum is allowed to test the speed range
It determines；
C) trough is located between two spikes, and wave crest is located between two troughs.
Sample frequency is set as FsampleHz, maximum test the speed range V km/h, then minimum interval Intervalmin=3.6*
π * R*Fsample/V sampled point；
Step 307: wave crest, the trough lookup result screened according to 306 calculates vehicle wheel rotational speed rpm, is expressed as
Formula:
Rpm=(top_cnt-1) * SAMPLE_RATE/ (top_position [top_cnt-1]-top_position
[0])
Wherein, top_cnt is the wave crest number in buffer, and SAMPLE_RATE is the sampling rate of acceleration transducer,
Top_position [i] is position of i-th of wave crest in Buffer, and top_position [0] is the significant wave screened
First of peak, top_position [top_cnt-1] are the last one of the Valid peak screened.
Step 308: vehicle velocity V X-HPF is calculated according to vehicle wheel rotational speed rpm and radius of wheel:
VX-HPF=rpm*2 π r, wherein r is radius of wheel.
Using the acceleration information in Y-axis as foundation, step 2 the following steps are included:
Step 201: the collected acceleration transducer initial data of acceleration transducer being stored in buffer, buffer
Length according to sensor sample rate and it is required test the speed range determine；
Step 202: low-pass filtering is carried out to the Y-axis acceleration information in buffer, is indicated with following formula:
YLPF_current=α * YRAW_current+ (1- α) * YLPF_previous
Wherein, YLPF_current is this Y-axis low-pass filtering data；YRAW_current is the original of this Y-axis sampling
Beginning data；YLPF_previous is last Y-axis low-pass filtering data；α is low-pass filtering coefficient, 0 < α < 1, α=t/ (t+
dT)；T is filter temporal constant, is the unitary sampling time of acceleration transducer, dT is sample frequency；
Step 203: high-pass filtering being carried out to the Y-axis acceleration information in the buffer obtained after step 202, with following public affairs
Formula indicates:
YHPF_current=YRAW_current-YLPF_current
Wherein, YHPF_current is this Y-axis high-pass filtering data, and YLPF_current is this Y-axis low-pass filtering
Data, YRAW_current are the initial data of this Y-axis sampling；
Step 204: the data obtained after step 203 being smoothed using sliding mean filter, are obtained in sine
Wavy acceleration information.
Step 3 the following steps are included:
Step 301: the first-order difference of acceleration information obtained in step 2 is calculated, formula is expressed as:
Diff_Buffer [i]=Buffer [i+1]-Buffer [i]
Wherein, i ∈ 1,2 ..., N-1, N are the length of buffer；
Step 302: first-order difference data Diff_Buffer is carried out taking symbolic operation, is expressed as formula:
Trend_Buffer=sign (Diff_Buffer)
It is expressed as traversal first-order difference data Diff_Buffer, if Diff_Buffer [i] > 0, Trend_Buffer
[i]=1；If Diff_Buffer < 0, Trend_Buffer [i]=- 1, otherwise Trend_Buffer [i]=0；
Step 303: inverted order traverses Trend_Buffer, if Trend_Buffer [i]=0 and Trend_Buffer [i+
1] > 0, then Trend_Buffer [i]=1；If Trend_Buffer [i]=0 and Trend_Buffer [i+1] < 0,
Trend_Buffer [i]=- 1；
Step 304: calculating the first-order difference of Trend_Buffer, as Diff_Trend_Buffer, be expressed as public affairs
Formula:
Diff_Trend_Buffer [i]=Trend_Buffer [i+1]-Trend_Buffer [i]
Wherein, i ∈ 1,2 ..., N-1, N are the length of buffer；
Step 305: Diff_Trend_Buffer obtained in traversal step 304, if Diff_Trend_Buffer [i]
=-2, then i+1 is a peak value position, and corresponding peak value is Buffer [i+1]；If Diff_Trend_Buffer [i]=2,
I+1 is a valley position, and corresponding trough is Buffer [i+1]；
Step 306: wave crest, the trough found out is screened, and removes the error result as caused by data dithering, will
Final Wave crest and wave trough lookup result, the position of number and each Wave crest and wave trough including Wave crest and wave trough in a buffer are protected
It deposits, the condition that wave crest, trough are screened is the physical features of wave crest, trough, comprising:
A) absolute value of acceleration value is greater than 0.5g；
B) wave crest, trough interval are greater than minimum interval, and minimum interval is by sensor sample rate and maximum is allowed to test the speed range
It determines；
C) trough is located between two spikes, and wave crest is located between two troughs.
Sample frequency is set as FsampleHz, maximum test the speed range V km/h, then minimum interval Intervalmin=3.6*
π * R*Fsample/V sampled point；
Step 307: wave crest, the trough lookup result screened according to step 306 calculates vehicle wheel rotational speed rpm, is expressed as
Following formula:
Rpm=(top_cnt-1) * SAMPLE_RATE/ (top_position [top_cnt-1]-top_position
[0])
Wherein, top_cnt is the wave crest number in buffer, and SAMPLE_RATE is the sampling rate of acceleration transducer,
Top_position [i] is position of i-th of wave crest in Buffer, and top_position [0] is the significant wave screened
First of peak, top_position [top_cnt-1] are the last one of the Valid peak screened；
Step 308: vehicle velocity V Y-HPF is calculated according to vehicle wheel rotational speed rpm and radius of wheel:
VY-HPF=rpm*2 π r, wherein r is radius of wheel.
See Fig. 4, the acceleration transducer in the present embodiment can rely on speed measuring equipment realization comprising communication connection
MCU 3, acceleration transducer 4, bluetooth 5, acceleration transducer are used to acquire the acceleration information of vehicle, and MCU 3 is used for adding
Speed data is handled, extraction rate metrical information, calculating speed as a result, and by bluetooth 5 will test the speed result broadcast, also wrap
Include battery 6 and peripheral circuit 7.
Speed measuring equipment is mounted on hub for vehicle wheel by the way of magnet absorption, and when installation will ensure that accelerometer is in vehicle
Center is taken turns, speed measuring equipment rotates together with wheel, and the X of acceleration transducer, Y-axis are led by gravity and vehicle forward direction
The effect of gravitation, due to the periodicity of wheel rotation, gravity also has periodicity in the component of X, Y-axis, by calculating its period
Property, the revolving speed of available wheel, and then speed can be calculated according to radius of wheel.
Specific embodiment 2:
In certain scenes, such as wheel does not rotate, but in the case of a shock, the X/Y axis of acceleration transducer is high
Although logical data are not sine waves, can also there be Wave crest and wave trough, according to above-mentioned algorithm, the deviation that tests the speed will be generated, therefore used
Following vehicle speed measuring methods based on acceleration transducer improves rate accuracy.
See Fig. 2, a kind of vehicle speed measuring method based on acceleration transducer, comprising the following steps:
Step 1: acceleration transducer being set 1 at the position in the axle center of wheel, using the axle center of wheel as origin, is being accelerated
Perpendicular where degree sensor 1 establishes X-axis and Y-axis, and Z axis is arranged perpendicular to the perpendicular where acceleration transducer 1,
By acceleration transducer 1, acceleration information is acquired；
Step 2: reading acceleration transducer data, obtain the acceleration degree on the acceleration information and Y-axis in X-axis
According to, to any carry out low-pass filtering and high-pass filtering in the acceleration information on the acceleration information and Y-axis in X-axis,
Then it is smoothed, is obtained in sinuous acceleration information using sliding mean filter；
Step 3: wave crest and trough number and each wave crest, trough obtained in searching 2 in acceleration information and
Position in data calculates vehicle wheel rotational speed, calculates speed by vehicle wheel rotational speed；
Step 4: the second acceleration transducer 2 is set on wheel, speed is measured by the second acceleration transducer 2, it is right
The speed that step 3 obtains is calibrated.
Using the acceleration information in X-axis as foundation, step 2 the following steps are included:
Step 201: the collected acceleration transducer initial data of acceleration transducer being stored in buffer, buffer
Length according to acceleration transducer sample rate and it is required test the speed range determine；
Step 202: low-pass filtering is carried out to the X-axis acceleration information in buffer, is indicated with following formula:
XLPF_current=α * XRAW_current+ (1- α) * XLPF_previous
Wherein, XLPF_current is this X-axis low-pass filtering data；XRAW_current is the original of this X-axis sampling
Beginning data；XLPF_previous is last X-axis low-pass filtering data；α is low-pass filtering coefficient, 0 < α < 1, α=t/ (t+
dT)；T is filter temporal constant, is the unitary sampling time of acceleration transducer, dT is sample frequency；
Step 203: high-pass filtering being carried out to the X-axis acceleration information in the buffer obtained after step 202, with following public affairs
Formula indicates:
XHPF_current=XRAW_current-XLPF_current
Wherein, XHPF_current is this X-axis high-pass filtering data, and XLPF_current is this X-axis low-pass filtering
Data, XRAW_current are the initial data of this X-axis sampling；
Step 204: the data obtained after step 203 being smoothed using sliding mean filter, are obtained in sine
Wavy acceleration information.
Step 3 the following steps are included:
Step 301: the first-order difference of acceleration information obtained in step 2 is calculated, formula is expressed as:
Diff_Buffer [i]=Buffer [i+1]-Buffer [i]
Wherein, i ∈ 1,2 ..., N-1, N are the length of buffer；
Step 302: first-order difference data Diff_Buffer is carried out taking symbolic operation, is expressed as formula:
Trend_Buffer=sign (Diff_Buffer),
It is expressed as traversal first-order difference data Diff_Buffer, if Diff_Buffer [i] > 0, Trend_Buffer
[i]=1；If Diff_Buffer < 0, Trend_Buffer [i]=- 1, otherwise Trend_Buffer [i]=0；
Step 303: inverted order traverses Trend_Buffer, if Trend_Buffer [i]=0 and Trend_Buffer [i+
1] > 0, then Trend_Buffer [i]=1；If Trend_Buffer [i]=0 and Trend_Buffer [i+1] < 0,
Trend_Buffer [i]=- 1；
Step 304: calculating the first-order difference of Trend_Buffer, as Diff_Trend_Buffer, be expressed as public affairs
Formula:
Diff_Trend_Buffer [i]=Trend_Buffer [i+1]-Trend_Buffer [i]
Wherein, i ∈ 1,2 ..., N-1, N are the length of buffer；
Step 305: Diff_Trend_Buffer obtained in traversal 304, if Diff_Trend_Buffer [i]=-
2, then i+1 is a peak value position, and corresponding peak value is Buffer [i+1]；If Diff_Trend_Buffer [i]=2, i+1
For a valley position, corresponding trough is Buffer [i+1]；
Step 306: wave crest, the trough found out is screened, and removes the error result as caused by data dithering, will
Final Wave crest and wave trough lookup result, the position of number and each Wave crest and wave trough including Wave crest and wave trough in a buffer are protected
It deposits, the condition that wave crest, trough are screened is the physical features of wave crest, trough, comprising:
A) absolute value of acceleration value is greater than 0.5g；
B) wave crest, trough interval are greater than minimum interval, and minimum interval is by sensor sample rate and maximum is allowed to test the speed range
It determines；
C) trough is located between two spikes, and wave crest is located between two troughs.
Sample frequency is set as FsampleHz, maximum test the speed range V km/h, then minimum interval Intervalmin=3.6*
π * R*Fsample/V sampled point；
Step 307: wave crest, the trough lookup result screened according to 306 calculates vehicle wheel rotational speed rpm, is expressed as
Formula:
Rpm=(top_cnt-1) * SAMPLE_RATE/ (top_position [top_cnt-1]-top_position
[0])
Wherein, top_cnt is the wave crest number in buffer, and SAMPLE_RATE is the sampling rate of acceleration transducer,
Top_position [i] is position of i-th of wave crest in Buffer, and top_position [0] is the significant wave screened
First of peak, top_position [top_cnt-1] are the last one of the Valid peak screened.
Further, step 4 comprising the following specific steps
Step 410: the second acceleration transducer being placed at the position that the axle center apart from wheel is R1, in vertical plane
Coordinate system is established, using the axle center of wheel as origin, Y-axis is directed toward axle center along the vertical direction, and X-direction is vertical with Y direction；
Step 420: acceleration information being read by acceleration transducer, passes through the acceleration a of Y-axisYTurn to calculate wheel
Fast VY-LPF, is expressed as formula:
aIt is centripetal=aY=ω2* R1=VY-LPF2/R22*R1
Wherein, it is centripetal acceleration that a is centripetal, and ω is angular speed of wheel, and V is wheel linear velocity, and R1 is acceleration transducer
Distance apart from axis wheel, R2 are radius of wheel, and the X of acceleration transducer, Y-axis are drawn by gravity and vehicle forward direction
The effect of power, and in addition to this centripetal force effect that Y-axis is also rotated by wheel.After vehicle wheel rotational speed is more than a certain range, to
The meeting of mental and physical efforts calculates vehicle wheel rotational speed by the centripetal acceleration of Y-axis much larger than the effect of gravity and car direction of advance tractive force,
Obtain vehicle velocity V Y-LPF.
Step 430: acceleration information being read by acceleration transducer, obtains the acceleration degree of X-axis；To adding in X-axis
Speed data carries out low-pass filtering and high-pass filtering, is then smoothed, is obtained in sine wave using sliding mean filter
The acceleration information of shape；Search the wave crest and trough number and each wave crest, trough and in data in acceleration information
Position calculates vehicle wheel rotational speed, passes through vehicle wheel rotational speed and calculates vehicle velocity V X-LPF.
Step 430 is specific as follows:
Step 4301: the collected acceleration transducer initial data of the second acceleration transducer is stored in buffer,
The length of buffer is determined according to the second acceleration transducer sample rate and the required range that tests the speed；
Step 4302: low-pass filtering is carried out to the X-axis acceleration information in buffer, is indicated with following formula:
XLPF_current=α * XRAW_current+ (1- α) * XLPF_previous
Wherein, XLPF_current is this X-axis low-pass filtering data；XRAW_current is the original of this X-axis sampling
Beginning data；XLPF_previous is last X-axis low-pass filtering data；α is low-pass filtering coefficient, 0 < α < 1, α=t/ (t+
dT)；T is filter temporal constant, is the unitary sampling time of acceleration transducer, dT is sample frequency；
Step 4303: high-pass filtering being carried out to the X-axis acceleration information in the buffer obtained after step 4302, with as follows
Formula indicates:
XHPF_current=XRAW_current-XLPF_current
Wherein, XHPF_current is this X-axis high-pass filtering data, and XLPF_current is this X-axis low-pass filtering
Data, XRAW_current are the initial data of this X-axis sampling；
Step 4304: the data obtained after step 4303 being smoothed using sliding mean filter, are obtained in just
The wavy acceleration information of string；
Step 4305: the first-order difference of acceleration information obtained in step 4304 is calculated, formula is expressed as:
Diff_Buffer [i]=Buffer [i+1]-Buffer [i]
Wherein, i ∈ 1,2 ..., N-1, N are the length of buffer；
Step 4306: first-order difference data Diff_Buffer is carried out taking symbolic operation, is expressed as formula:
Trend_Buffer=sign (Diff_Buffer)
It is expressed as traversal first-order difference data Diff_Buffer, if Diff_Buffer [i] > 0, Trend_Buffer
[i]=1；If Diff_Buffer < 0, Trend_Buffer [i]=- 1, otherwise Trend_Buffer [i]=0；
Step 4307: inverted order traverses Trend_Buffer, if Trend_Buffer [i]=0 and Trend_Buffer [i+
1] > 0, then Trend_Buffer [i]=1；If Trend_Buffer [i]=0 and Trend_Buffer [i+1] < 0,
Trend_Buffer [i]=- 1；
Step 4308: calculating the first-order difference of Trend_Buffer, as Diff_Trend_Buffer, be expressed as
Formula:
Diff_Trend_Buffer [i]=Trend_Buffer [i+1]-Trend_Buffer [i]
Wherein, i ∈ 1,2 ..., N-1, N are the length of buffer；
Step 4309: Diff_Trend_Buffer obtained in traversal step 4308, if Diff_Trend_Buffer
[i]=- 2, then i+1 is a peak value position, and corresponding peak value is Buffer [i+1]；If Diff_Trend_Buffer [i]=
2, then i+1 is a valley position, and corresponding trough is Buffer [i+1]；
Step 4310: wave crest, the trough found out is screened, and removes the error result as caused by data dithering,
By final Wave crest and wave trough lookup result, the position of number and each Wave crest and wave trough including Wave crest and wave trough in a buffer is protected
It deposits；
Step 4311: wave crest, the trough lookup result screened according to step 4309 calculates vehicle wheel rotational speed rpm, indicates
For following formula:
Rpm=(top_cnt-1) * SAMPLE_RATE/ (top_position [top_cnt-1]-top_position
[0])
Wherein, top_cnt is the wave crest number in buffer, and SAMPLE_RATE is the sampling rate of acceleration transducer,
Top_position [i] is position of i-th of wave crest in Buffer, and top_position [0] is the significant wave screened
First of peak, top_position [top_cnt-1] are the last one of the Valid peak screened；
Step 4312: vehicle velocity V X-LPF is calculated according to vehicle wheel rotational speed rpm and radius of wheel:
VX-LPF=rpm*2 π r, wherein r is radius of wheel.
Step 440: the speed that step 3 obtains being calibrated by vehicle velocity V X-LPF and vehicle velocity V Y-LPF, is obtained final
Vehicle velocity V final sets thresholding VTH, VTH=(2*G*R2 2*R1) 1/2=(2*9.8*R2 2*R1)1/2；
As VY-LPF < VTH, the result that finally tests the speed Vfinal=VX-LPF；
As VY-LPF >=VTH, the result that finally tests the speed Vfinal=(VX-HPF+VY-LPF)/2.
Vehicle speed measuring method based on acceleration transducer of the invention, directly installs speed measuring equipment on vehicle to be measured,
Application method simple and flexible no longer needs to install speed measuring equipment on road, at low cost；
Vehicle speed measuring method based on acceleration transducer of the invention measures vehicle wheel rotational speed by acceleration transducer
Mode calculating speed, compared to the algorithm calculating speed with integrated acceleration, the scope of application is wider, can also be with even if uniform motion
Test.In addition, needing an initial velocity to will lead to and test the speed if initial velocity is not right with the algorithm of integrated acceleration calculating speed
Mistake, and such problems is not present in the algorithm that the present invention designs.
Claims (10)
1. a kind of vehicle speed measuring method based on acceleration transducer, which comprises the following steps:
Step 1: acceleration transducer being placed at the position in the axle center of wheel, using the axle center of wheel as origin, passed in acceleration
Perpendicular where sensor establishes X-axis and Y-axis, and Z axis is arranged perpendicular to the perpendicular where acceleration transducer, by adding
Velocity sensor acquires acceleration information；
Step 2: reading acceleration transducer data, the acceleration information on the acceleration information and Y-axis in X-axis is obtained, to X
Any carry out low-pass filtering and high-pass filtering in the acceleration information on acceleration information and Y-axis on axis, are then adopted
It is smoothed, is obtained in sinuous acceleration information with sliding mean filter；
Step 3: wave crest and trough number and each wave crest, trough in acceleration information obtained in finding step 2 and
Position in data calculates vehicle wheel rotational speed, calculates speed by vehicle wheel rotational speed.
2. a kind of vehicle speed measuring method based on acceleration transducer according to claim 1, which is characterized in that step 2
The following steps are included:
Step 201: the collected acceleration transducer initial data of acceleration transducer being stored in buffer, the length of buffer
Degree is determined according to acceleration transducer sample rate and the required range that tests the speed；
Step 202: low-pass filtering is carried out to the X-axis acceleration information in buffer, is indicated with following formula:
XLPF_current=α * XRAW_current+ (1- α) * XLPF_previous
Wherein, XLPF_current is this X-axis low-pass filtering data；XRAW_current is the original number of this X-axis sampling
According to；XLPF_previous is last X-axis low-pass filtering data；α is low-pass filtering coefficient, 0 < α < 1, α=t/ (t+dT)；t
It is the unitary sampling time of acceleration transducer, dT is sample frequency for filter temporal constant；
Step 203: high-pass filtering being carried out to the X-axis acceleration information in the buffer obtained after step 202, with following formula table
Show:
XHPF_current=XRAW_current-XLPF_current
Wherein, XHPF_current is this X-axis high-pass filtering data, and XLPF_current is this X-axis low-pass filtering data,
XRAW_current is the initial data of this X-axis sampling；
Step 204: the data obtained after step 203 being smoothed using sliding mean filter, are obtained in sinusoidal wave shape
Acceleration information.
3. a kind of vehicle speed measuring method based on acceleration transducer according to claim 2, which is characterized in that step 3
The following steps are included:
Step 301: the first-order difference of acceleration information obtained in step 2 is calculated, formula is expressed as:
Diff_Buffer [i]=Buffer [i+1]-Buffer [i]
Wherein, i ∈ 1,2 ..., N-1, N are the length of buffer；
Step 302: first-order difference data Diff_Buffer is carried out taking symbolic operation, is expressed as formula:
Trend_Buffer=sign (Diff_Buffer),
It is expressed as traversal first-order difference data Diff_Buffer, if Diff_Buffer [i] > 0, Trend_Buffer [i]=
1；If Diff_Buffer < 0, Trend_Buffer [i]=- 1, otherwise Trend_Buffer [i]=0；
Step 303: inverted order traverses Trend_Buffer, if Trend_Buffer [i]=0 and Trend_Buffer [i+1] > 0,
Then Trend_Buffer [i]=1；If Trend_Buffer [i]=0 and Trend_Buffer [i+1] < 0, Trend_
Buffer [i]=- 1；
Step 304: the first-order difference of Trend_Buffer, as Diff_Trend_Buffer are calculated, formula is expressed as:
Diff_Trend_Buffer [i]=Trend_Buffer [i+1]-Trend_Buffer [i]
Wherein, i ∈ 1,2 ..., N-1, N are the length of buffer；
Step 305: Diff_Trend_Buffer obtained in traversal 304, if Diff_Trend_Buffer [i]=- 2, i
+ 1 is a peak value position, and corresponding peak value is Buffer [i+1]；If Diff_Trend_Buffer [i]=2, i+1 mono-
A valley position, corresponding trough are Buffer [i+1]；
Step 306: wave crest, the trough found out is screened, and removes the error result as caused by data dithering, will be final
Wave crest and wave trough lookup result, number and each Wave crest and wave trough including Wave crest and wave trough position in a buffer save；
Step 307: wave crest, the trough lookup result screened according to 306 calculates vehicle wheel rotational speed rpm, is expressed as formula:
Rpm=(top_cnt-1) * SAMPLE_RATE/ (top_position [top_cnt-1]-top_position [0])
Wherein, top_cnt is the wave crest number in buffer, and SAMPLE_RATE is the sampling rate of acceleration transducer, top_
Position [i] is position of i-th of wave crest in Buffer, and top_position [0] is the Valid peak screened
First, top_position [top_cnt-1] is the last one of the Valid peak screened；
Step 308: vehicle velocity V X-HPF is calculated according to vehicle wheel rotational speed rpm and radius of wheel:
VX-HPF=rpm*2 π r, wherein r is radius of wheel.
4. a kind of vehicle speed measuring method based on acceleration transducer according to claim 1, which is characterized in that step 2
The following steps are included:
Step 201: the collected acceleration transducer initial data of acceleration transducer being stored in buffer, the length of buffer
Degree is determined according to sensor sample rate and the required range that tests the speed；
Step 202: low-pass filtering is carried out to the Y-axis acceleration information in buffer, is indicated with following formula:
YLPF_current=α * YRAW_current+ (1- α) * YLPF_previous
Wherein, YLPF_current is this Y-axis low-pass filtering data；YRAW_current is the original number of this Y-axis sampling
According to；YLPF_previous is last Y-axis low-pass filtering data；α is low-pass filtering coefficient, 0 < α < 1, α=t/ (t+dT)；t
It is the unitary sampling time of acceleration transducer, dT is sample frequency for filter temporal constant；
Step 203: high-pass filtering being carried out to the Y-axis acceleration information in the buffer obtained after step 202, with following formula table
Show:
YHPF_current=YRAW_current-YLPF_current
Wherein, YHPF_current is this Y-axis high-pass filtering data, and YLPF_current is this Y-axis low-pass filtering data,
YRAW_current is the initial data of this Y-axis sampling；
Step 204: the data obtained after step 203 being smoothed using sliding mean filter, are obtained in sinusoidal wave shape
Acceleration information.
5. a kind of vehicle speed measuring method based on acceleration transducer according to claim 4, which is characterized in that step 3
The following steps are included:
Step 301: the first-order difference of acceleration information obtained in step 2 is calculated, formula is expressed as:
Diff_Buffer [i]=Buffer [i+1]-Buffer [i]
Wherein, i ∈ 1,2 ..., N-1, N are the length of buffer；
Step 302: first-order difference data Diff_Buffer is carried out taking symbolic operation, is expressed as formula:
Trend_Buffer=sign (Diff_Buffer),
It is expressed as traversal first-order difference data Diff_Buffer, if Diff_Buffer [i] > 0, Trend_Buffer [i]=
1；If Diff_Buffer < 0, Trend_Buffer [i]=- 1, otherwise Trend_Buffer [i]=0；
Step 303: inverted order traverses Trend_Buffer, if Trend_Buffer [i]=0 and Trend_Buffer [i+1] > 0,
Then Trend_Buffer [i]=1；If Trend_Buffer [i]=0 and Trend_Buffer [i+1] < 0, Trend_
Buffer [i]=- 1；
Step 304: the first-order difference of Trend_Buffer, as Diff_Trend_Buffer are calculated, formula is expressed as:
Diff_Trend_Buffer [i]=Trend_Buffer [i+1]-Trend_Buffer [i]
Wherein, i ∈ 1,2 ..., N-1, N are the length of buffer；
Step 305: Diff_Trend_Buffer obtained in traversal 304, if Diff_Trend_Buffer [i]=- 2, i
+ 1 is a peak value position, and corresponding peak value is Buffer [i+1]；If Diff_Trend_Buffer [i]=2, i+1 mono-
A valley position, corresponding trough are Buffer [i+1]；
Step 306: wave crest, the trough found out is screened, and removes the error result as caused by data dithering, will be final
Wave crest and wave trough lookup result, number and each Wave crest and wave trough including Wave crest and wave trough position in a buffer save；
Step 307: wave crest, the trough lookup result screened according to 306 calculates vehicle wheel rotational speed rpm, is expressed as formula:
Rpm=(top_cnt-1) * SAMPLE_RATE/ (top_position [top_cnt-1]-top_position [0])
Wherein, top_cnt is the wave crest number in buffer, and SAMPLE_RATE is the sampling rate of acceleration transducer, top_
Position [i] is position of i-th of wave crest in Buffer, and top_position [0] is the Valid peak screened
First, top_position [top_cnt-1] is the last one of the Valid peak screened；
Step 308: vehicle velocity V Y-HPF is calculated according to vehicle wheel rotational speed rpm and radius of wheel:
VY-HPF=rpm*2 π r, wherein r is radius of wheel.
6. a kind of vehicle speed measuring method based on acceleration transducer according to claim 3 or 5, it is characterised in that:
The condition that wave crest, trough are screened is the physical features of wave crest, trough, comprising:
A) absolute value of acceleration value is greater than 0.5g；
B) wave crest, trough interval are greater than minimum interval, and minimum interval is by sensor sample rate and the maximum range that tests the speed is allowed to determine；
C) trough is located between two spikes, and wave crest is located between two troughs；
Sample frequency is set as FsampleHz, maximum test the speed range V km/h, then minimum interval Intervalmin=3.6* π * R*
Fsample/V sampled point.
7. a kind of vehicle speed measuring method based on acceleration transducer according to claim 3 or 5, it is characterised in that: step
Rapid 4: the second acceleration transducer being set on wheel, speed, the vehicle obtained to step 3 are measured by the second acceleration transducer
Speed is calibrated.
8. a kind of vehicle speed measuring method based on acceleration transducer according to claim 7, it is characterised in that: step 4
Comprising the following specific steps
Step 410: the second acceleration transducer being placed at the position that the axle center apart from wheel is R1, established in vertical plane
Coordinate system, using the axle center of wheel as origin, Y-axis is directed toward axle center along the vertical direction, and X-direction is vertical with Y direction；
Step 420: acceleration information being read by acceleration transducer, passes through the acceleration a of Y-axisYTo calculate vehicle wheel rotational speed VY-
LPF is expressed as formula:
aIt is centripetal=aY=ω2* R1=VY-LPF2/R22*R1
Wherein, it is centripetal acceleration that a is centripetal, and ω is angular speed of wheel, and V is wheel linear velocity, and R1 is acceleration transducer distance
The distance of axis wheel, R2 are radius of wheel, calculate vehicle wheel rotational speed by the centripetal acceleration of Y-axis, obtain vehicle velocity V Y-LPF；
Step 430: acceleration information being read by acceleration transducer, obtains the acceleration degree of X-axis；To the acceleration in X-axis
Data carry out low-pass filtering and high-pass filtering, are then smoothed, are obtained in sinuous using sliding mean filter
Acceleration information；Wave crest and trough number and each wave crest, trough and the position in data in lookup acceleration information
Vehicle wheel rotational speed is calculated, passes through vehicle wheel rotational speed and calculates vehicle velocity V X-LPF；
Step 440: the speed that step 3 obtains being calibrated by vehicle velocity V X-LPF and vehicle velocity V Y-LPF, obtains final speed
Vfinal sets thresholding VTH, VTH=(2*G*R2 2*R1) 1/2=(2*9.8*R2 2*R1)1/2；
As VY-LPF < VTH, the result that finally tests the speed Vfinal=VX-LPF；
As VY-LPF >=VTH, the result that finally tests the speed Vfinal=(VX-HPF+VY-LPF)/2 or Vfinal=(VY-HPF
+VY-LPF)/2。
9. a kind of vehicle speed measuring method based on acceleration transducer according to claim 8, it is characterised in that: step
430 is specific as follows:
Step 4301: by the collected acceleration transducer initial data deposit buffer of the second acceleration transducer, buffering
The length of device is determined according to the second acceleration transducer sample rate and the required range that tests the speed；
Step 4302: low-pass filtering is carried out to the X-axis acceleration information in buffer, is indicated with following formula:
XLPF_current=α * XRAW_current+ (1- α) * XLPF_previous
Wherein, XLPF_current is this X-axis low-pass filtering data；XRAW_current is the original number of this X-axis sampling
According to；XLPF_previous is last X-axis low-pass filtering data；α is low-pass filtering coefficient, 0 < α < 1, α=t/ (t+dT)；t
It is the unitary sampling time of acceleration transducer, dT is sample frequency for filter temporal constant；
Step 4303: high-pass filtering being carried out to the X-axis acceleration information in the buffer obtained after step 4302, with following formula
It indicates:
XHPF_current=XRAW_current-XLPF_current
Wherein, XHPF_current is this X-axis high-pass filtering data, and XLPF_current is this X-axis low-pass filtering data,
XRAW_current is the initial data of this X-axis sampling；
Step 4304: the data obtained after step 4303 being smoothed using sliding mean filter, are obtained in sine wave
The acceleration information of shape；
Step 4305: the first-order difference of acceleration information obtained in step 4304 is calculated, formula is expressed as:
Diff_Buffer [i]=Buffer [i+1]-Buffer [i]
Wherein, i ∈ 1,2 ..., N-1, N are the length of buffer；
Step 4306: first-order difference data Diff_Buffer is carried out taking symbolic operation, is expressed as formula:
Trend_Buffer=sign (Diff_Buffer),
It is expressed as traversal first-order difference data Diff_Buffer, if Diff_Buffer [i] > 0, Trend_Buffer [i]=
1；If Diff_Buffer < 0, Trend_Buffer [i]=- 1, otherwise Trend_Buffer [i]=0；
Step 4307: inverted order traverses Trend_Buffer, if Trend_Buffer [i]=0 and Trend_Buffer [i+1] >
0, then Trend_Buffer [i]=1；If Trend_Buffer [i]=0 and Trend_Buffer [i+1] < 0, Trend_
Buffer [i]=- 1；
Step 4308: the first-order difference of Trend_Buffer, as Diff_Trend_Buffer are calculated, formula is expressed as:
Diff_Trend_Buffer [i]=Trend_Buffer [i+1]-Trend_Buffer [i]
Wherein, i ∈ 1,2 ..., N-1, N are the length of buffer；
Step 4309: Diff_Trend_Buffer obtained in traversal step 4308, if Diff_Trend_Buffer [i]
=-2, then i+1 is a peak value position, and corresponding peak value is Buffer [i+1]；If Diff_Trend_Buffer [i]=2,
I+1 is a valley position, and corresponding trough is Buffer [i+1]；
Step 4310: wave crest, the trough found out is screened, and removes the error result as caused by data dithering, will most
Whole Wave crest and wave trough lookup result, the position of number and each Wave crest and wave trough including Wave crest and wave trough in a buffer save；
Step 4311: the wave crest that is screened according to step 4310, trough lookup result calculate vehicle wheel rotational speed rpm, be expressed as
Lower formula:
Rpm=(top_cnt-1) * SAMPLE_RATE/ (top_position [top_cnt-1]-top_position [0])
Wherein, top_cnt is the wave crest number in buffer, and SAMPLE_RATE is the sampling rate of acceleration transducer, top_
Position [i] is position of i-th of wave crest in Buffer, and top_position [0] is the Valid peak screened
First, top_position [top_cnt-1] is the last one of the Valid peak screened；
Step 4312: vehicle velocity V X-LPF is calculated according to vehicle wheel rotational speed rpm and radius of wheel:
VX-LPF=rpm*2 π r, wherein r is radius of wheel.
10. a kind of speed measuring equipment, it is characterised in that: MCU, acceleration transducer including communication connection, bluetooth, the acceleration
Sensor is used to acquire the acceleration information of vehicle, and the MCU is for handling acceleration information, extraction rate measurement letter
Breath, calculating speed as a result, and by the bluetooth will test the speed result broadcast.
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