CN108007331B - The method and its system of motor vehicle length are calculated based on geomagnetic sensor - Google Patents
The method and its system of motor vehicle length are calculated based on geomagnetic sensor Download PDFInfo
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- CN108007331B CN108007331B CN201711185737.5A CN201711185737A CN108007331B CN 108007331 B CN108007331 B CN 108007331B CN 201711185737 A CN201711185737 A CN 201711185737A CN 108007331 B CN108007331 B CN 108007331B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
- G01B7/02—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness
- G01B7/04—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness specially adapted for measuring length or width of objects while moving
- G01B7/042—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness specially adapted for measuring length or width of objects while moving for measuring length
- G01B7/046—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness specially adapted for measuring length or width of objects while moving for measuring length using magnetic means
Abstract
The present invention provides a kind of method and its system that motor vehicle length is calculated based on geomagnetic sensor, after two voltage waveforms for obtaining each automobile；Interpolation is carried out to two voltage waveforms of each automobile, obtains the interpolated waveforms of each automobile；Bandpass filtering is carried out to the interpolated waveforms of each automobile in multiple frequency ranges, obtains bandpass waveform of each automobile in each frequency range；The sampling number for obtaining bandpass waveform of each automobile in each frequency range, the length of each automobile is calculated according to the sampling number of each automobile；Calculate the sum of the absolute error in each frequency range in more automobiles between the length and physical length of each automobile；Choose the length that the smallest frequency range of the sum of absolute error calculates each automobile as the filtering frequency range of bandpass filtering and according to the filtering frequency range.Method and system provided by the invention is able to ascend stability, reliability and accuracy, while can be suitable for each automobile.
Description
Technical field
The present invention relates to field of intelligent transportation technology more particularly to a kind of sides that motor vehicle length is calculated based on geomagnetic sensor
Method and its system.
Background technique
Traffic study equipment abbreviation intermodulation equipment in intelligent transportation system is put into effect according to project study institute, Department of Transportation
Associated documents traffic study equipment need road pavement automobile to classify, wherein automobile can be divided into according to vehicle commander L medium and small
Car (0 < L≤6), buggy (0 < L≤6), middle lorry (6 < L≤12), motor bus (6 < L≤12), truck (6 < L≤12),
Six class of super large lorry (12 < L).It is required according to the separation vehicle of intermodulation equipment, the calculating of motor vehicle length is very important.
Earth magnetism wagon detector (Geomagnetic Vehicle Detector, GVD) is the vehicle based on magnetoresistive sensor
Detection technique has the characteristics that size is small, easy for installation, reactionless to nonferromagnetic object, high reliablity, and experiment has been demonstrate,proved
Bright geomagnetic sensor has good effect for sound state vehicle detection, speed vehicle commander estimation, vehicle classification etc..
In existing intermodulation equipment, geomagnetic sensor is primarily used at the beginning of calculating automobile number, automobile passage speed, automobile
Step classification, and be rarely employed in terms of motor vehicle length calculating, also have and geomagnetic sensor is used for motor vehicle length calculating aspect, still
Due to all kinds of technologies, computational length is inaccurate, cannot provide a kind of relatively reliable and stable vehicle commander's calculation method.
Summary of the invention
To solve the above-mentioned problems, the present invention propose it is a kind of based on geomagnetic sensor calculate motor vehicle length method and its be
System, is able to ascend accuracy, stability and reliability.
It is proposed by the present invention the specific technical proposal is: provide it is a kind of based on geomagnetic sensor calculate motor vehicle length method,
The method includes the steps:
The voltage signal of two geomagnetic sensors corresponding to each automobile in more automobiles is obtained respectively；
The voltage signal of two geomagnetic sensors corresponding to each automobile is sampled respectively, obtains each vapour
Two voltage waveforms of vehicle；
Interpolation is carried out to two voltage waveforms of each automobile, obtains the interpolated waveforms of each automobile；
Bandpass filtering is carried out to the interpolated waveforms of each automobile in multiple frequency ranges, obtains each automobile in each frequency
Bandpass waveform in section；
The sampling number for obtaining bandpass waveform of each automobile in each frequency range, according to the sampled point of each automobile
Number calculates the length of each automobile；
Calculate the sum of the absolute error in each frequency range in more automobiles between the length and physical length of each automobile；
The smallest frequency range of the sum of absolute error is chosen as the filtering frequency range of bandpass filtering and according to the filtering frequency range meter
Calculate the length of each automobile.
Further, step carries out interpolation to two voltage waveforms of each automobile, obtains the interpolation of each automobile
Waveform specifically includes:
Two voltage waveforms of each automobile are filtered, two filter shapes of each automobile are obtained；
Interpolation is carried out to two filter shapes of each automobile, obtains the interpolated waveforms of each automobile.
Further, step carries out interpolation to two filter shapes of each automobile, obtains the interpolation of each automobile
Waveform specifically includes:
Cross-correlation coefficient of two voltage waveforms in each sampled point of each automobile is calculated, it is mutual to obtain each automobile
The maximum sampled point of related coefficient；
The speed of each automobile is calculated according to each maximum sampled point of automobile cross-correlation coefficient；
The normalization factor of each automobile is calculated according to the speed of each automobile；
Interpolation is carried out according to two filter shapes of the normalization factor of each automobile to each automobile, is obtained each
The interpolated waveforms of automobile.
Further, the normalization factor of each automobile is calculated according to the following equation:
Wherein, viIndicate the speed of i-th automobile, v0Indicate normalizated velocity, v0It is 10~30,000 ms/h.
Further, step carries out bandpass filtering to the interpolated waveforms of each automobile in multiple frequency ranges, obtains each
Bandpass waveform of the automobile in each frequency range specifically includes:
Bandpass filtering is carried out to the interpolated waveforms of each automobile in each frequency range, obtains each automobile in the frequency
First waveform in section；
By the voltage zero setting corresponding to the preceding n sampled point of the first waveform in the frequency range of each automobile, obtain
Second waveform of each automobile in the frequency range；
Second waveform of each automobile in the frequency range is reversed, the of each automobile in the frequency range is obtained
Three waveforms；
In the frequency range bandpass filtering is carried out to the third waveform of each automobile again, obtains each automobile in institute
State the 4th waveform in frequency range；
By voltage zero setting corresponding to the preceding n sampled point of the 4th waveform of each automobile in the frequency range, obtain
Bandpass waveform of each automobile in the frequency range.
Further, the size of n is fs/ 5~fs/ 4, wherein fsFor sample frequency.
Further, two endpoints of multiple frequency bands are respectively 1~5Hz, 50~80Hz.
Further, the sampling number for obtaining bandpass waveform of each automobile in each frequency range specifically includes:
The sampled point of bandpass waveform of each automobile in each frequency range is successively judged along the forward direction of sampling time axis
Voltage value whether be less than predetermined threshold；
If the voltage value of the sampled point is less than the predetermined threshold, by band logical of each automobile in each frequency range
Sampled point before waveform is located at the sampled point on sampling time axis removes, and obtains each automobile in each frequency range
First bandpass waveform；
Adopting for first bandpass waveform of each automobile in each frequency range is reversely successively judged along sampling time axis
Whether the voltage value of sampling point is less than the predetermined threshold；
If the voltage value of the sampled point be less than the predetermined threshold, by each automobile in each frequency range first
Sampled point of the bandpass waveform on sampling time axis after the sampled point removes, and obtains each automobile in each frequency range
The second interior bandpass waveform；
It obtains the sampling number of second bandpass waveform of each automobile in each frequency range and exists as each automobile
The sampling number of bandpass waveform in each frequency range.
Further, the size of the predetermined threshold be δ × | Vmax-Vmin|, wherein VmaxIndicate each automobile every
The maximum voltage value of bandpass waveform in a frequency range, VminIndicate the minimum of bandpass waveform of each automobile in each frequency range
Voltage value, the size of δ are 4%~6%.
The present invention also provides it is a kind of based on geomagnetic sensor calculate motor vehicle length system, the system comprises:
Voltage signal obtains module, for obtaining two earth magnetism sensings corresponding to each automobile in more automobiles respectively
The voltage signal of device；
Sampling module is adopted for the voltage signal respectively to two geomagnetic sensors corresponding to each automobile
Sample obtains two voltage waveforms of each automobile；
Interpolating module carries out interpolation for two voltage waveforms to each automobile, obtains the interpolation of each automobile
Waveform；
Bandpass filtering modules block is obtained for carrying out bandpass filtering to the interpolated waveforms of each automobile in multiple frequency ranges
Bandpass waveform of each automobile in each frequency range；
Length computation module, for obtaining the sampling number of bandpass waveform of each automobile in each frequency range, according to
The sampling number of each automobile calculates the length of each automobile；
Error calculating module, for calculate each automobile in more automobiles in each frequency range length Yu physical length it
Between the sum of absolute error；
Frequency band chooses module, for choosing filtering frequency range and root of the smallest frequency range of the sum of absolute error as bandpass filtering
The length of each automobile is calculated according to the filtering frequency range.
The method and its system provided by the invention that motor vehicle length is calculated based on geomagnetic sensor, by calculating each frequency range
The sum of absolute error in interior more automobiles between the length and physical length of each automobile；Choose the sum of absolute error minimum
Filtering frequency range of the frequency range as bandpass filtering, thus improve the stability of entire motor vehicle length calculation method, reliability and
Accuracy, while by carrying out linear regression analysis to more automobiles, it chooses so that the sum of absolute error of more automobiles minimum
The subsequent calculating motor vehicle length of conduct used in frequency range, improve the versatility of entire method.
Detailed description of the invention
What is carried out in conjunction with the accompanying drawings is described below, above and other aspect, features and advantages of the embodiment of the present invention
It will become clearer, in attached drawing:
Fig. 1 is the flow chart that the method for motor vehicle length is calculated based on geomagnetic sensor；
Fig. 2 is the structure chart that the system of motor vehicle length is calculated based on geomagnetic sensor.
Specific embodiment
Hereinafter, with reference to the accompanying drawings to detailed description of the present invention embodiment.However, it is possible to come in many different forms real
The present invention is applied, and the present invention should not be construed as limited to the specific embodiment illustrated here.On the contrary, providing these implementations
Example is in order to explain the principle of the present invention and its practical application, to make others skilled in the art it will be appreciated that the present invention
Various embodiments and be suitable for the various modifications of specific intended application.
Referring to Fig.1, it is provided in this embodiment based on geomagnetic sensor calculate motor vehicle length method comprising steps of
S1, the voltage signal for obtaining two geomagnetic sensors corresponding to each automobile in more automobiles respectively.
In step sl, two geomagnetic sensors are arranged along the direction interval of running car, and each automobile is passing through two
Two voltage signals are generated when a geomagnetic sensor respectively, two voltage signals of each automobile are analog signal.
S2, the voltage signal of two geomagnetic sensors corresponding to each automobile is sampled respectively, is obtained each
Two voltage waveforms of automobile, two voltage waveforms of each automobile obtained after sampling are digital signal, sample frequency
It can be determined according to actual needs.
S3, interpolation is carried out to two voltage waveforms of each automobile, obtains the interpolated waveforms of each automobile, wherein
A waveform i.e. interpolated waveforms are obtained after carrying out interpolation to two voltage waveforms of each automobile.
In step s3, interpolation formula used by the present embodiment is as follows:
yk=(1- λ) xk+λxk+1
Wherein, xkAnd xk+1It is voltage value corresponding to k-th of sampled point and k+1 sampled point, y before interpolationkAfter being interpolation
Voltage value corresponding to k-th of sampled point, λ are interpolation normalization factors, certainly, can also be common using other in step S3
Difference value equation, it is merely exemplary here to show, it is not used in restriction.
S4, bandpass filtering is carried out to the interpolated waveforms of each automobile in multiple frequency ranges, obtains each automobile every
Bandpass waveform in a frequency range.Wherein, j-th of frequency range a in multiple frequency rangesjTo bjTwo endpoints be respectively ajAnd bj, aj< bj,
Preferably, two endpoints of multiple frequency bands are respectively 1~5Hz, 50~80Hz, i.e. ajFor 1~5Hz, bjFor 50~80Hz.
S5, the sampling number for obtaining bandpass waveform of each automobile in each frequency range, according to adopting for each automobile
Number of samples calculates the length of each automobile, wherein it is as follows to calculate formula used by the length of each automobile:
Wherein, LiIndicate the length of i-th automobile, 0 < i≤N, N indicates the number of automobile, v0Indicate normalizated velocity,
KijIndicate the sampling number of bandpass waveform of i-th automobile in j-th of frequency range, D indicate between two geomagnetic sensors away from
From fsFor sample frequency.
S6, calculate absolute error in each frequency range in more automobiles between the length and physical length of each automobile it
With.
In step s 6, by taking j-th of frequency range as an example, in j-th of frequency range ajTo bjEach automobile in middle N automobile of calculating
Length LiWith physical length Li0Between the sum of absolute error εjUsed calculation formula is as follows:
S7, the sum of absolute error the smallest frequency range, that is, min (ε is chosen1, ε2……εj..., 1≤j≤M) it is filtered as band logical
The filtering frequency range of wave and the length that each automobile is calculated according to filtering frequency range, wherein M indicates the number of multiple frequency ranges.
After carrying out linear regression analysis by length of the step S1~S7 to N automobile, so that fitting is finally counted
Calculate the selected filtering frequency range of each motor vehicle length, when the subsequent length for needing to calculate other automobiles other than this N automobile,
It only needs to repeat above step S1~S5 in the filtering frequency range to this automobile to obtain band logical of the automobile in the frequency range
The sampling number of waveform can acquire the length of this automobile, so that entire method is suitable for each automobile.
In order to eliminate interference of the external electromagnetic signal to geomagnetic sensor, step S3 is specifically included:
S31, two voltage waveforms of each automobile are filtered, obtain two filter shapes of each automobile,
Wherein, needing to filter out is common electromagnetic interference signal, for example, rejection frequency is the power frequency interference signals of 50Hz；
S32, interpolation is carried out to two filter shapes of each automobile, obtains the interpolated waveforms of each automobile.
Specifically, step S32 is specifically included:
S321, cross-correlation coefficient of two voltage waveforms in each sampled point for calculating each automobile, obtain each
The maximum sampled point of automobile cross-correlation coefficient；
S322, the speed v that each automobile is calculated according to each maximum sampled point of automobile cross-correlation coefficienti, calculate
Formula is as follows:
Wherein, viIndicate the speed of i-th automobile, D indicates the distance between two geomagnetic sensors, fsFor sample frequency,
τ is each maximum sampled point of automobile cross-correlation coefficient to the time interval between the origin of time shaft, for example, i-th vapour
Two voltage waveforms of vehicle are maximum in k-th of sampled point cross-correlation coefficient, then τ=k × ts,ts=1/fs；
S323, according to the speed v of each automobileiCalculate the normalization factor of each automobile；
S324, interpolation is carried out to two filter shapes of each automobile according to the normalization factor of each automobile, obtained
Obtain the interpolated waveforms of each automobile.
In step S323, the normalization factor α of each automobile is calculated according to the following equation:
Wherein, viIndicate the speed of i-th automobile, v0Indicate normalizated velocity, v0It is 10~30,000 ms/h, preferably
Ground, v0For the minimum speed of N automobile.According to the normalization factor of each automobile to two filter shapes of each automobile
Interpolation is carried out, influence of the different speed to this method is avoided.
Specifically, step S4 includes:
S41, bandpass filtering is carried out to the interpolated waveforms of each automobile in each frequency range, obtains each automobile at this
First waveform in frequency range, for example, in j-th of frequency range ajTo bjBandpass filtering inside is carried out to the interpolated waveforms of N automobile respectively,
N automobile is obtained in j-th of frequency range ajTo bjInterior N number of first waveform, in this way each frequency range correspond to N number of first waveform；
S42, by the voltage zero setting corresponding to the preceding n sampled point of the first waveform in the frequency range of each automobile, obtain
Second waveform of each automobile in the frequency range is obtained, preferably, the size of n is fs/5~fs/4, fs is sample frequency；
S43, second waveform of each automobile in the frequency range is reversed, obtains the of each automobile in the frequency range
Three waveforms；
S44, bandpass filtering is carried out to the third waveform of each automobile in the frequency range again, each automobile is obtained and exists
The 4th waveform in the frequency range；
S45, the 4th waveform by each automobile in the frequency range preceding n sampled point corresponding to voltage zero setting, obtain
Bandpass waveform of each automobile in the frequency range, wherein the size of n in step S42 n it is equal in magnitude.
In step s 4, after carrying out a bandpass filtering to the interpolated waveforms of each automobile respectively in each frequency range
Then waveform after interception is reversed n sampled point before carrying out bandpass filtering again and intercepting by n sampled point before intercepting, thus
The concussion of filter step response generation can be eliminated, the wave band remained is consistency and the preferable frequency range of stability, is mentioned
The stability and reliability of entire method are risen.
Specifically, step S5 includes:
S51, adopting for bandpass waveform of each automobile in each frequency range is successively judged along the forward direction of sampling time axis
Whether the voltage value of sampling point is less than predetermined threshold, and the corresponding abscissa of bandpass waveform is sampling time, the vertical seat of bandpass waveform
Marking corresponding is voltage value, the corresponding voltage value of each sampled point on sampling time axis, here, sampling time axis
Forward direction refers to from left to right, i.e. the direction of sampling time from small to large, successively judges the corresponding voltage value of each sampled point
Whether predetermined threshold is less than；
If the voltage value of S52, the sampled point is less than predetermined threshold, by band logical wave of each automobile in each frequency range
Sampled point before shape is located at the sampled point on sampling time axis removes, and obtains first of each automobile in each frequency range
Bandpass waveform, for example, bandpass waveform includes 40 sampled points, if the 10th corresponding voltage value of sampled point is less than predetermined threshold
Value, then remove the 1st~10 sampled point of bandpass waveform, remaining the first bandpass waveform of waveform formation；
S53, first bandpass waveform of each automobile in each frequency range is reversely successively judged along sampling time axis
The voltage value of sampled point whether be less than the predetermined threshold, here, sampling time axis reversely refers to from right to left, that is, adopting
The direction of sample time from big to small, successively judges whether the corresponding voltage value of each sampled point is less than predetermined threshold；
If the voltage value of S54, the sampled point is less than predetermined threshold, by first band of each automobile in each frequency range
Sampled point of the logical waveform on sampling time axis after the sampled point removes, and obtains each automobile in each frequency range
Second bandpass waveform, for example, the first bandpass waveform includes 30 sampled points, if the 26th corresponding voltage value of sampled point is less than
Predetermined threshold then removes the 26th~30 sampled point of bandpass waveform, remaining the second bandpass waveform of waveform formation；
S55, the sampling number for obtaining second bandpass waveform of each automobile in each frequency range and as each vapour
The sampling number of bandpass waveform of the vehicle in each frequency range, for example, the second bandpass waveform finally includes 25 sampled points, then band logical
The sampling number of waveform is 25.
Preferably, in the present embodiment predetermined threshold size are as follows:
δ×|Vmax-Vmin|
Wherein, VmaxIndicate the maximum voltage value of bandpass waveform of each automobile in each frequency range, VminIndicate each
The minimum amount of voltage that of bandpass waveform of the automobile in each frequency range, the size of δ are 4%~6%.
Referring to Fig. 2, the present embodiment additionally provides a kind of system for calculating motor vehicle length based on geomagnetic sensor, the system
Module 1, sampling module 2, interpolating module 3, bandpass filtering modules block 4, length computation module 5, error meter are obtained including voltage signal
Calculate module 6, frequency band chooses module 7.
Voltage signal obtains module 1 for obtaining two earth magnetism sensings corresponding to each automobile in more automobiles respectively
The voltage signal of device.Sampling module 2 for respectively to the voltage signal of two geomagnetic sensors corresponding to each automobile into
Row sampling, obtains two voltage waveforms of each automobile.Interpolating module 3 be used for two voltage waveforms of each automobile into
Row interpolation obtains the interpolated waveforms of each automobile.Bandpass filtering modules block 4 is for inserting each automobile in multiple frequency ranges
It is worth waveform and carries out bandpass filtering, obtains bandpass waveform of each automobile in each frequency range.Length computation module 5 is for obtaining
The sampling number of bandpass waveform of each automobile in each frequency range, calculates each according to the sampling number of each automobile
The length of automobile.Error calculating module 6 is used to calculate the length and actual (tube) length of each automobile in more automobiles in each frequency range
The sum of absolute error between degree.Frequency band chooses module 7 for choosing the smallest frequency range of the sum of absolute error as bandpass filtering
Filtering frequency range and the length of each automobile is calculated according to the filtering frequency range.
The above is only the specific embodiment of the application, it is noted that for the ordinary skill people of the art
For member, under the premise of not departing from the application principle, several improvements and modifications can also be made, these improvements and modifications are also answered
It is considered as the protection scope of the application.
Claims (10)
1. a kind of method for calculating motor vehicle length based on geomagnetic sensor, comprising steps of obtaining in more automobiles each respectively
The voltage signal of two geomagnetic sensors corresponding to automobile；It is characterized in that, the method also includes steps:
The voltage signal of two geomagnetic sensors corresponding to each automobile is sampled respectively, obtains each automobile
Two voltage waveforms；
Interpolation is carried out to two voltage waveforms of each automobile, obtains the interpolated waveforms of each automobile；
Bandpass filtering is carried out to the interpolated waveforms of each automobile in multiple frequency ranges, obtains each automobile in each frequency range
Bandpass waveform；
The sampling number for obtaining bandpass waveform of each automobile in each frequency range, according to the sampling number meter of each automobile
Calculate the length of each automobile；
Calculate the sum of the absolute error in each frequency range in more automobiles between the length and physical length of each automobile；
The smallest frequency range of the sum of absolute error is chosen to calculate often as the filtering frequency range of bandpass filtering and according to the filtering frequency range
The length of one automobile.
2. the method according to claim 1, wherein step two voltage waveforms of each automobile are carried out it is slotting
Value, the interpolated waveforms for obtaining each automobile specifically include:
Two voltage waveforms of each automobile are filtered, two filter shapes of each automobile are obtained；
Interpolation is carried out to two filter shapes of each automobile, obtains the interpolated waveforms of each automobile.
3. according to the method described in claim 2, it is characterized in that, step two filter shapes of each automobile are carried out it is slotting
Value, the interpolated waveforms for obtaining each automobile specifically include:
Cross-correlation coefficient of two voltage waveforms in each sampled point of each automobile is calculated, each automobile cross-correlation is obtained
The maximum sampled point of coefficient；
The speed of each automobile is calculated according to each maximum sampled point of automobile cross-correlation coefficient；
The normalization factor of each automobile is calculated according to the speed of each automobile；
Interpolation is carried out according to two filter shapes of the normalization factor of each automobile to each automobile, obtains each vapour
The interpolated waveforms of vehicle.
4. according to the method described in claim 3, it is characterized in that, the normalization of each automobile is calculated according to the following equation
The factor:
Wherein, viIndicate the speed of i-th automobile, v0Indicate normalizated velocity, v0It is 10~30,000 ms/h.
5. the method according to claim 1, wherein step is in multiple frequency ranges to the interpolation wave of each automobile
Shape carries out bandpass filtering, obtains bandpass waveform of each automobile in each frequency range and specifically includes:
Bandpass filtering is carried out to the interpolated waveforms of each automobile in each frequency range, obtains each automobile in the frequency range
First waveform；
By the voltage zero setting corresponding to the preceding n sampled point of the first waveform in the frequency range of each automobile, obtain each
Second waveform of the automobile in the frequency range；
Second waveform of each automobile in the frequency range is reversed, third wave of each automobile in the frequency range is obtained
Shape；
In the frequency range bandpass filtering is carried out to the third waveform of each automobile again, obtains each automobile in the frequency
The 4th waveform in section；
By voltage zero setting corresponding to the preceding n sampled point of the 4th waveform of each automobile in the frequency range, obtain each
Bandpass waveform of the automobile in the frequency range.
6. according to the method described in claim 5, it is characterized in that, the size of n is fs/ 5~fs/ 4, wherein fsFor sampling frequency
Rate.
7. the method according to claim 1, wherein two endpoints of multiple frequency bands be respectively 1~5Hz, 50~
80Hz。
8. the method according to claim 1, wherein obtaining bandpass waveform of each automobile in each frequency range
Sampling number specifically include:
The electricity of the sampled point of bandpass waveform of each automobile in each frequency range is successively judged along the forward direction of sampling time axis
Whether pressure value is less than predetermined threshold；
If the voltage value of the sampled point is less than the predetermined threshold, by bandpass waveform of each automobile in each frequency range
Sampled point before being located at the sampled point on sampling time axis removes, and obtains first of each automobile in each frequency range
Bandpass waveform；
Along the sampled point for reversely successively judging first bandpass waveform of each automobile in each frequency range of sampling time axis
Voltage value whether be less than the predetermined threshold；
If the voltage value of the sampled point is less than the predetermined threshold, by first band logical of each automobile in each frequency range
Sampled point of the waveform on sampling time axis after the sampled point removes, and obtains each automobile in each frequency range
Second bandpass waveform；
Obtain the sampling number of second bandpass waveform of each automobile in each frequency range and as each automobile each
The sampling number of bandpass waveform in frequency range.
9. according to the method described in claim 8, it is characterized in that, the size of the predetermined threshold be δ × | Vmax-Vmin|,
In, VmaxIndicate the maximum voltage value of bandpass waveform of each automobile in each frequency range, VminIndicate each automobile every
The minimum amount of voltage that of bandpass waveform in a frequency range, the size of δ are 4%~6%.
10. a kind of system for calculating motor vehicle length based on geomagnetic sensor, comprising: voltage signal obtains module, for obtaining respectively
Take the voltage signal of two geomagnetic sensors corresponding to each automobile in more automobiles；It is characterized in that, the system is also
Include:
Sampling module is sampled for the voltage signal respectively to two geomagnetic sensors corresponding to each automobile, is obtained
Obtain two voltage waveforms of each automobile；
Interpolating module carries out interpolation for two voltage waveforms to each automobile, obtains the interpolated waveforms of each automobile；
Bandpass filtering modules block obtains each for carrying out bandpass filtering to the interpolated waveforms of each automobile in multiple frequency ranges
Bandpass waveform of the automobile in each frequency range；
Length computation module, for obtaining the sampling number of bandpass waveform of each automobile in each frequency range, according to each
The sampling number of automobile calculates the length of each automobile；
Error calculating module, for calculating in each frequency range in more automobiles between the length and physical length of each automobile
The sum of absolute error；
Frequency band chooses module, for choosing the smallest frequency range of the sum of absolute error as the filtering frequency range of bandpass filtering and according to institute
State the length that filtering frequency range calculates each automobile.
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