CN107331160B - Method and apparatus based on single geomagnetic sensor measurement car speed - Google Patents
Method and apparatus based on single geomagnetic sensor measurement car speed Download PDFInfo
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- CN107331160B CN107331160B CN201710762178.3A CN201710762178A CN107331160B CN 107331160 B CN107331160 B CN 107331160B CN 201710762178 A CN201710762178 A CN 201710762178A CN 107331160 B CN107331160 B CN 107331160B
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- G—PHYSICS
- G08—SIGNALLING
- G08G—TRAFFIC CONTROL SYSTEMS
- G08G1/00—Traffic control systems for road vehicles
- G08G1/01—Detecting movement of traffic to be counted or controlled
- G08G1/042—Detecting movement of traffic to be counted or controlled using inductive or magnetic detectors
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- G—PHYSICS
- G08—SIGNALLING
- G08G—TRAFFIC CONTROL SYSTEMS
- G08G1/00—Traffic control systems for road vehicles
- G08G1/01—Detecting movement of traffic to be counted or controlled
- G08G1/052—Detecting movement of traffic to be counted or controlled with provision for determining speed or overspeed
Abstract
The invention discloses a kind of method and apparatus based on single geomagnetic sensor measurement car speed, belong to intelligent traffic vehicle detection field.Method based on single geomagnetic sensor measurement car speed includes: step 1: obtaining geomagnetic field intensity in multiple periods that geomagnetic sensor acquires in real time, the geomagnetic sensor is for being arranged under road；Step 2: geomagnetic field intensity change rate is calculated；Step 3: according to the relationship of the geomagnetic field intensity change rate and car speed of obtained geomagnetic field intensity change rate and measured in advance, car speed is calculated.The present invention take full advantage of vehicle speed to the shock wave in earth's magnetic field rule, construction volume is small, construction cost is low.
Description
Technical field
The present invention relates to intelligent traffic vehicle detection technique fields, particularly relate to a kind of based on single geomagnetic sensor measurement vehicle
The method and apparatus of speed.
Background technique
With the high speed development of social economy and the continuous expansion of city size, urban transport problems is also with increasingly tight
Weight.Wherein, the most distinct issues be city traffic safety problem.And the accurate detection of vehicular traffic travel speed is traffic
The powerful guarantee of safety and the important link of intelligent transportation system.
Currently, utilizing the traditional approach of geomagnetic sensor measurement speed are as follows: by two geomagnetic sensors, front and back is arranged respectively,
Bury in road in the following, and certain distance d is kept between two geomagnetic sensors, vehicle when driving, first passes through on road
One of geomagnetic sensor, when by this geomagnetic sensor, vehicle can nearby send out geomagnetic sensor earth's magnetic field and generate disturbance,
Disturbance of the geomagnetic sensors detection to this vehicle to earth's magnetic field judges that vehicle passes through, starts timing, vehicle passes through another therewith
When geomagnetic sensor device, when the geomagnetic sensors detection to vehicle is to the disturbance in earth's magnetic field, timing terminates.By above-mentioned detection
The available vehicle of process successively passes through time t used in two geomagnetic sensors, then can be acquired by formula v=d/t
The speed of vehicle.
The method of traditional measurement speed has used two geomagnetic sensors, measures vehicle just with geomagnetic sensor
Determining whether vehicle whether there is or not disturbance to earth's magnetic field passes through, and does not carry out more to the speed of vehicle to the variation of the disturbance quantity in earth's magnetic field
Add the analysis of accurate quantification, does not make full use of the rule of vehicle magnetic interference over the ground；Also, it is surveyed using two geomagnetic sensors
Amount speed needs bury two geomagnetic sensors below road, more serious to road damage, great in constructing amount, increase and are constructed into
This.
Summary of the invention
The present invention provides a kind of using shock wave of the vehicle speed to earth's magnetic field is regular, construction volume is small, construction cost is low
Based on single geomagnetic sensor measurement car speed method and apparatus.
In order to solve the above technical problems, present invention offer technical solution is as follows:
On the one hand, the present invention provides a kind of method based on single geomagnetic sensor measurement car speed, comprising:
Step 1: obtaining geomagnetic field intensity in multiple periods that geomagnetic sensor acquires in real time；The geomagnetic sensor is used for
It is arranged under road；
Step 2: geomagnetic field intensity change rate is calculated；
Step 3: according to obtained geomagnetic field intensity change rate and the geomagnetic field intensity change rate and vehicle of measured in advance
The relationship of speed, is calculated car speed.
Further, further include step 11 between the step 1 and step 2:
Step 11: vehicle being judged whether there is according to the geomagnetic field intensity of acquisition and is passed through, is held if so, executing step 2 if nothing
Row step 1.
Further, the step 11 is further are as follows:
The geomagnetic field intensity that the geomagnetic field intensity that current period obtains was obtained with a upper period is compared, if being more than to set
Determine threshold value, then regarded as vehicle process, execute step 2, otherwise, regards as no vehicle and pass through, execute step 1.
Further, the geomagnetic sensor is three axis geomagnetic sensors, and the geomagnetic field intensity is the earth magnetism field strength of X-axis
Degree, the direction of the X-axis of the geomagnetic sensor is parallel with direction of traffic, and the step 2 is further are as follows:
Geomagnetic field intensity when judging to have vehicle to pass through is Bnow, enable B1=Bnow, from obtaining BnowMoment, Bnow1For most
The geomagnetic field intensity of new one acquisition, Bpre1For data Bnow1A upper period acquisition geomagnetic field intensity, work as Bpre1-Bnow1>Δ
B1When, wherein Δ B1For given threshold, B is enabled2=Bpre1, calculate from there is geomagnetic field intensity BnowStart to there is earth's magnetic field
Intensity Bpre1This period geomagnetic sensor has the geomagnetic field intensity number N acquired, the geomagnetic field intensity change rate altogether are as follows:Wherein, BsFor the geomagnetic field intensity change rate of geomagnetic sensor X-axis, T is the week of geomagnetic sensor sampling
Phase.
Preferably, in the step 3, the geomagnetic field intensity change rate B of measured in advancesWith the relationship of car speed v are as follows:
V=aBs 3+bBs 2+cBs+d (1)
Wherein, a, b, c, d are constant；
The determination method of constant a, b, c, d are as follows in formula (1):
The geomagnetic field intensity data under different vehicle speed v are acquired with the same period, acquire ground X-axis according to the step 2
Change rate of magnetic density Bs, obtain multiple groups Bs- v data obtain constant a, b, c, d using least square method matched curve.
On the other hand, the present invention provides a kind of device based on single geomagnetic sensor measurement car speed, comprising:
Acquisition module: for obtaining geomagnetic field intensity in multiple periods that geomagnetic sensor acquires in real time；The earth magnetism passes
Sensor is for being arranged under road；
First computing module: for geomagnetic field intensity change rate to be calculated；
Second computing module: for the earth magnetism field strength according to obtained geomagnetic field intensity change rate and measured in advance
The relationship for spending change rate and car speed, is calculated car speed.
Further, the device based on single geomagnetic sensor measurement car speed further include:
Judgment module: vehicle is judged whether there is for the geomagnetic field intensity according to acquisition and is passed through.
Further, the judgment module, is further used for:
The geomagnetic field intensity that current period obtains is compared with the geomagnetic field intensity that upper a cycle obtains, if being more than
Given threshold has then regarded as vehicle process, otherwise, regards as no vehicle and passes through.
Further, the geomagnetic sensor is three axis geomagnetic sensors, and the geomagnetic field intensity is the earth magnetism field strength of X-axis
Degree, the direction of the X-axis of the geomagnetic sensor is parallel with direction of traffic, and first computing module is further used for:
Geomagnetic field intensity when judging to have vehicle to pass through is Bnow, enable B1=Bnow, from obtaining BnowMoment, Bnow1For most
The geomagnetic field intensity of new one acquisition, Bpre1For data Bnow1A upper period acquisition geomagnetic field intensity, work as Bpre1-Bnow1>Δ
B1When, wherein Δ B1For given threshold, B is enabled2=Bpre1, calculate from there is geomagnetic field intensity BnowStart to there is earth's magnetic field
Intensity Bpre1This period geomagnetic sensor has the geomagnetic field intensity number N acquired, the geomagnetic field intensity change rate altogether are as follows:Wherein, BsFor the geomagnetic field intensity change rate of geomagnetic sensor X-axis, T is the week of geomagnetic sensor sampling
Phase.
Preferably, in second computing module, preset geomagnetic field intensity change rate BsWith the pass of car speed v
System are as follows:
V=aBs 3+bBs 2+cBs+d (2)
Wherein, a, b, c, d are constant, and the determination method of constant a, b, c, d are as follows in formula (2):
The geomagnetic field intensity data under different vehicle speed v are acquired with the same period, are asked according to first computing module
Obtain the change rate of magnetic density B of ground X-axiss, obtain multiple groups Bs- v data, using least square method matched curve, obtain constant a, b,
c、d。
The invention has the following advantages:
Method and apparatus based on single geomagnetic sensor measurement car speed of the invention, using single geomagnetic sensor pair
Car speed measures, and is quantified using influence of the car speed to earth's magnetic field, passes through geomagnetic field intensity change rate
Car speed is obtained with the relationship of car speed, takes full advantage of the rule of car speed magnetic fields over the ground, this side
Method measurement car speed is all suitable for any vehicle, solves the influence different problems that different automobile types generate earth's magnetic field.
Measurement car speed method of the invention reduces under geomagnetic sensor burial ground only with single geomagnetic sensor
Construction volume and destruction to road, construction cost it is low.
Detailed description of the invention
Fig. 1 is the flow chart of the method for the invention that car speed is measured based on single geomagnetic sensor；
Fig. 2 is the relation schematic diagram of geomagnetic field intensity change rate and car speed of the invention；
Fig. 3 is the earth's magnetic field schematic diagram of geomagnetic sensor of the invention.
Specific embodiment
To keep the technical problem to be solved in the present invention, technical solution and advantage clearer, below in conjunction with attached drawing and tool
Body embodiment is described in detail.
On the one hand, the present invention provides a kind of method based on single geomagnetic sensor measurement car speed, as shown in Figures 1 to 3,
Include:
Step 1: obtaining geomagnetic field intensity in multiple periods that geomagnetic sensor acquires in real time；Geomagnetic sensor is for being arranged
Under road, setting depth can be arranged according to common knowledge；It is strong that geomagnetic sensor with the cycle T set acquires earth's magnetic field in real time
It spends and acquires once, single-chip microcontroller reads the sensitivity that once ensure that its detection from geomagnetic sensor；
Step 2: geomagnetic field intensity change rate is calculated；Two adjacent periods can be used when calculating geomagnetic field variation rate
Interior geomagnetic field intensity value is subtracted each other to be calculated divided by the period again, or is calculated and obtained using other modes；
Step 3: according to obtained geomagnetic field intensity change rate and the geomagnetic field intensity change rate and vehicle of measured in advance
The relationship of speed, is calculated car speed.
Method based on single geomagnetic sensor measurement car speed of the invention, using single geomagnetic sensor to vehicle speed
Degree measures, and is quantified using influence of the car speed to earth's magnetic field, passes through geomagnetic field intensity change rate and vehicle
The relationship of speed obtains car speed, takes full advantage of the rule of car speed magnetic fields over the ground, this method measurement
Car speed is all suitable for any vehicle, solves the influence different problems that different automobile types generate earth's magnetic field.
Measurement car speed method of the invention reduces under geomagnetic sensor burial ground only with single geomagnetic sensor
Construction volume and destruction to road, construction cost it is low.
Further, to better implement the present invention, further include step 11 between step 1 and step 2:
Step 11: vehicle being judged whether there is according to the geomagnetic field intensity of acquisition and is passed through, is held if so, executing step 2 if nothing
Row step 1.
Further, step 11 is further are as follows:
The geomagnetic field intensity that the geomagnetic field intensity that current period obtains was obtained with a upper period is compared, if being more than
Given threshold has then regarded as vehicle process, executes step 2, otherwise, regards as no vehicle and passes through, execute step 1.Specifically,
When there is vehicle near the traveling to geomagnetic sensor of distant place, geomagnetic sensor is with sampling period collected geomagnetic field intensity meeting
Having substantially enhances, according to this feature, BnowFor geomagnetic sensor the last time acquisition earth's magnetic field X-axis geomagnetic field intensity,
BpreFor data BnowA upper period earth's magnetic field X-axis geomagnetic field intensity, work as Bnow-BpreWhen > Δ B, it is determined as that vehicle passes through
It crosses, otherwise, passes through without vehicle, wherein Δ B is to judge whether there is vehicle by threshold value set by geomagnetic sensor, and threshold value is big
Small setting can specifically be set according to noisy degree of prevailing circumstances etc., and the size of threshold value does not influence implementation of the invention.
If passing through geomagnetic sensor without vehicle, geomagnetic sensor continues to acquire geomagnetic sensor with the sampling period
A neighbouring earth's magnetic field field strength and geomagnetic sensor data monolithic of every acquisition is machine-readable to be taken once, and whether real-time monitoring vehicle has
Vehicle passes through.If there is having detected vehicle by near geomagnetic sensor, then carrying out to the magnetic field strength date of earth's magnetic field X-axis
Below deeper into analysis.
Preferably, geomagnetic sensor is three axis geomagnetic sensors, and geomagnetic field intensity is the geomagnetic field intensity of X-axis, and earth magnetism passes
The direction of the X-axis of sensor is parallel with direction of traffic, as shown in figure 3, geomagnetic sensor is buried in road with appropriate depth in the following,
Component schematic diagram of the magnetic field strength in X, Y, Z axis, it is assumed that total magnetic intensity S, the component in X, Y, Z axis be respectively X1,
Y1, Z1 then meetBecause the direction of X-axis is parallel with direction of traffic, the earth magnetism field data of X-axis is most
It is regular, it is preferred that the geomagnetic field intensity used in the present invention is the geomagnetic field intensity of X-axis；
For convenience of measurement geomagnetic field intensity change rate, the following are a kind of specific calculation methods:
Geomagnetic field intensity when judging to have vehicle to pass through is Bnow, enable B1=Bnow, from obtaining BnowMoment, Bnow1For most
The geomagnetic field intensity of new one acquisition, Bpre1For data Bnow1A upper period acquisition geomagnetic field intensity, work as Bpre1-Bnow1>Δ
B1When, wherein Δ B1For given threshold, B is enabled2=Bpre1, calculate from there is geomagnetic field intensity BnowStart to there is earth's magnetic field
Intensity Bpre1This period geomagnetic sensor has the geomagnetic field intensity number N acquired, the geomagnetic field intensity change rate altogether are as follows:Wherein, BsFor the geomagnetic field intensity change rate of geomagnetic sensor X-axis, T is the week of geomagnetic sensor sampling
Phase.
If it is judged that there is vehicle by the geomagnetic field intensity for the point for then passing through vehicle as the first of calculating change rate
It is a, i.e. Bnow, be tested with vehicle through when find out by meeting given threshold the earth's magnetic field X-axis of geomagnetic sensor acquisition
Maximum value (the i.e. B of geomagnetic field intensity during this period of timepre1) it is used as second point, subtracted with the geomagnetic field intensity value of second point
Go the geomagnetic field intensity value of first point divided by being exactly this period change rate, herein, this period can sample by counting
Points are to calculate, as (N+1) T.It is worth noting that, the computation interval of above-mentioned calculation method is that judgement is opened when having vehicle to pass through
Stopping when beginning maximum value occur to the geomagnetic field intensity of X-axis of certain a period of time, is not arrived at the time of which occurs for vehicle
At the time of right above up to geomagnetic sensor, therefore, it is desirable to which, according to the velocity interval of vehicle to be measured, given threshold Δ is rationally set
B1, Δ B1Setting can be according to the velocity interval of vehicle to be measured, and guarantee the geomagnetic field intensity maximum value B of X-axispre1Appear in vehicle
Reach geomagnetic field intensity right above before, carry out test of many times, obtain reasonable given threshold.This calculation method is being taken into account
While simple, accurate rate is higher.
Preferably, in step 3, the geomagnetic field intensity change rate B of measured in advancesWith the relationship of car speed v are as follows:
V=aBs 3+bBs 2+cBs+d (1)
Wherein, a, b, c, d are constant；
The determination method of constant a, b, c, d are as follows in formula (1):
The geomagnetic field intensity data under different vehicle speed v are acquired with the same period, the earth magnetism of X-axis is acquired according to step 2
Field intensity change rate Bs, obtain multiple groups Bs- v data obtain constant a, b, c, d using least square method matched curve.
Applicant is by a large number of experiments discovery, geomagnetic field intensity change rate BsRelationship with car speed v will not be because of vehicle
Type is different, vehicle size is different and changes, as shown in Fig. 2, the B obtained for tests- v data and curves, horizontal axis are vehicle speed
Degree, unit km/h, horizontal axis is the change rate of magnetic density of geomagnetic sensor X-axis, using least square method to Bs- v data and curves
It is fitted, obtains a=5.35 × 10-6, b=-0.00226, c=0.6457, d=-16.94, that is to say, that using the present invention
Calculation method can shield different automobile types, the vehicle size difference different to geomagnetic field disturbance, only according to change of magnetic field strength
Rate can calculate car speed.
In the present invention, it is 5-20ms that geomagnetic sensor acquires the cycle T of geomagnetic field intensity in real time；Outside geomagnetic sensor
Portion is provided with sealed insulation device, and geomagnetic sensor can be prevented to be imbedded in underground and penetrated by rainwater, of the invention based on singlely
Magnetic Sensor measures the speed of the measurable 0-240km/h of method of car speed.
It is worth noting that, the electronic components such as circuit board can be set in the periphery of geomagnetic sensor, due to being passed by earth magnetism
Sensor measurement geomagnetic field intensity is that well-known technique repeats no more herein to the internal structure of geomagnetic sensor and measuring principle, can
It is measured referring to common knowledge.
On the other hand, the present invention also provides a kind of devices based on single geomagnetic sensor measurement car speed, comprising:
Acquisition module: for obtaining geomagnetic field intensity in multiple periods that geomagnetic sensor acquires in real time；Geomagnetic sensor
For being arranged under road, setting depth can be arranged according to common knowledge, and geomagnetic sensor is acquired in real time with the cycle T set
Geomagnetic field intensity and acquire primary, single-chip microcontroller reads primary from geomagnetic sensor；
First computing module: for geomagnetic field intensity change rate to be calculated；
Second computing module: for the earth magnetism field strength according to obtained geomagnetic field intensity change rate and measured in advance
The relationship for spending change rate and car speed, is calculated car speed.
Device based on single geomagnetic sensor measurement car speed of the invention, acquisition module use single geomagnetic sensor
Car speed is measured, is quantified using influence of the car speed to earth's magnetic field, is changed by geomagnetic field intensity
Rate and the relationship of car speed obtain car speed, take full advantage of the rule of car speed magnetic fields over the ground, this
Method measurement car speed is all suitable for any vehicle, solves the influence different problems that different automobile types generate earth's magnetic field.
The present invention reduces construction volume under geomagnetic sensor burial ground and to road only with single geomagnetic sensor
Destruction, construction cost is low.
Further, the device based on single geomagnetic sensor measurement car speed further include:
Judgment module: vehicle is judged whether there is for the geomagnetic field intensity according to acquisition and is passed through.
Further, judgment module is further used for:
The geomagnetic field intensity that current period obtains is compared with the geomagnetic field intensity that upper a cycle obtains, if being more than
Given threshold has then regarded as vehicle process, otherwise, regards as no vehicle and passes through.Specifically, have vehicle from distant place traveling to
When near geomagnetic sensor, geomagnetic sensor is had with sampling period collected geomagnetic field intensity substantially to be enhanced, according to this
Feature, BnowFor the geomagnetic field intensity of the earth's magnetic field X-axis of geomagnetic sensor the last time acquisition, BpreFor data BnowUpper one week
The geomagnetic field intensity of the earth's magnetic field X-axis of phase, works as Bnow-BpreWhen > Δ B, it is determined as that vehicle passes through near geomagnetic sensor, otherwise,
There is no vehicle process, wherein Δ B is to judge whether there is vehicle by threshold value set by geomagnetic sensor, the setting of threshold size
It can specifically be set according to noisy degree of prevailing circumstances etc., the size of threshold value does not influence implementation of the invention.
If passing through geomagnetic sensor without vehicle, geomagnetic sensor continues to acquire geomagnetic sensor with the sampling period
A neighbouring earth's magnetic field field strength and geomagnetic sensor data monolithic of every acquisition is machine-readable to be taken once, and whether real-time monitoring vehicle has
Vehicle passes through.If there is having detected vehicle by near geomagnetic sensor, then carrying out to the magnetic field strength date of earth's magnetic field X-axis
Below deeper into analysis.
Preferably, geomagnetic sensor is three axis geomagnetic sensors, and geomagnetic field intensity is the geomagnetic field intensity of X-axis, and earth magnetism passes
The direction of the X-axis of sensor is parallel with direction of traffic, as shown in figure 3, geomagnetic sensor is buried in road with appropriate depth in the following,
Component schematic diagram of the magnetic field strength in X, Y, Z axis, it is assumed that total magnetic intensity S, the component in X, Y, Z axis be respectively X1,
Y1, Z1 then meetBecause the direction of X-axis is parallel with direction of traffic, the earth magnetism field data of X-axis is most
It is regular, it is preferred that the geomagnetic field intensity used in the present invention is the geomagnetic field intensity of X-axis；
The following are specific first computing modules to calculate a kind of calculation method of geomagnetic field intensity change rate:
Geomagnetic field intensity when judging to have vehicle to pass through is Bnow, enable B1=Bnow, from obtaining BnowMoment, Bnow1For most
The geomagnetic field intensity of new one acquisition, Bpre1For data Bnow1A upper period acquisition geomagnetic field intensity, work as Bpre1-Bnow1>Δ
B1When, wherein Δ B1For given threshold, B is enabled2=Bpre1, calculate from there is geomagnetic field intensity BnowStart to there is earth's magnetic field
Intensity Bpre1This period geomagnetic sensor has the geomagnetic field intensity number N acquired, the geomagnetic field intensity change rate altogether are as follows:Wherein, BsFor the geomagnetic field intensity change rate of geomagnetic sensor X-axis, T is the week of geomagnetic sensor sampling
Phase.
If it is judged that there is vehicle by the geomagnetic field intensity for the point for then passing through vehicle as the first of calculating change rate
It is a, i.e. Bnow, be tested with vehicle through when find out by meeting given threshold the earth's magnetic field X-axis of geomagnetic sensor acquisition
Maximum value (the i.e. B of geomagnetic field intensity during this period of timepre1) it is used as second point, subtracted with the geomagnetic field intensity value of second point
Go the geomagnetic field intensity value of first point divided by being exactly this period change rate, herein, this period can sample by counting
Points are to calculate, as (N+1) T.It is worth noting that, the computation interval of above-mentioned calculation method is that judgement is opened when having vehicle to pass through
Stopping when beginning maximum value occur to the geomagnetic field intensity of X-axis of certain a period of time, is not arrived at the time of which occurs for vehicle
At the time of right above up to geomagnetic sensor, therefore, it is desirable to which, according to the velocity interval of vehicle to be measured, given threshold Δ is rationally set
B1, Δ B1Setting can be according to the velocity interval of vehicle to be measured, and guarantee the geomagnetic field intensity maximum value B of X-axispre1Appear in vehicle
Reach geomagnetic field intensity right above before, carry out test of many times, obtain reasonable given threshold.This calculation method is being taken into account
While calculating simple, accurate rate is higher.
Preferably, in the second computing module, the geomagnetic field intensity change rate B of measured in advancesWith the relationship of car speed v
Are as follows:
V=aBs 3+bBs 2+cBs+d (2)
Wherein, a, b, c, d are constant, and the determination method of constant a, b, c, d are as follows in formula (2):
The geomagnetic field intensity data under different vehicle speed v are acquired with the same period, acquire X-axis according to the first computing module
Geomagnetic field intensity change rate Bs, obtain multiple groups Bs- v data obtain constant a, b, c, d using least square method matched curve.
Applicant is by a large number of experiments discovery, geomagnetic field intensity change rate BsRelationship with car speed v will not be because of vehicle
Type is different, vehicle size is different and changes, as shown in Fig. 2, the B obtained for tests- v data and curves, horizontal axis are vehicle speed
Degree, unit km/h, horizontal axis is the change rate of magnetic density of geomagnetic sensor X-axis, using least square method to Bs- v data and curves
It is fitted, obtains a=5.35 × 10-6, b=-0.00226, c=0.6457, d=-16.94, that is to say, that using the present invention
Calculation method can shield different automobile types, the vehicle size difference different to geomagnetic field disturbance, only according to change of magnetic field strength
Rate can calculate car speed.
In the present invention, it is 5-20ms that geomagnetic sensor acquires the cycle T of geomagnetic field intensity in real time；Outside geomagnetic sensor
Portion is provided with sealed insulation device, and geomagnetic sensor can be prevented to be imbedded in underground and penetrated by rainwater, of the invention based on singlely
Magnetic Sensor measures the speed of the measurable 0-240km/h of method of car speed.
It is worth noting that, the electronic components such as circuit board can be set in the periphery of geomagnetic sensor, due to being passed by earth magnetism
Sensor measurement geomagnetic field intensity is that well-known technique repeats no more herein to the internal structure of geomagnetic sensor and measuring principle, can
It is measured referring to common knowledge.
The above is a preferred embodiment of the present invention, it is noted that for those skilled in the art
For, without departing from the principles of the present invention, it can also make several improvements and retouch, these improvements and modifications
It should be regarded as protection scope of the present invention.
Claims (8)
1. a kind of method based on single geomagnetic sensor measurement car speed characterized by comprising
Step 1: obtaining geomagnetic field intensity in multiple periods that geomagnetic sensor acquires in real time；The geomagnetic sensor is for being arranged
Under road；
Step 2: geomagnetic field intensity change rate is calculated；
Step 3: according to obtained geomagnetic field intensity change rate and the geomagnetic field intensity change rate of measured in advance and vehicle speed
The relationship of degree, is calculated car speed；
The geomagnetic sensor is three axis geomagnetic sensors, and the geomagnetic field intensity is the geomagnetic field intensity of geomagnetic sensor X-axis,
The direction of the X-axis of the geomagnetic sensor is parallel with direction of traffic, and the step 2 includes:
Geomagnetic field intensity when judging to have vehicle to pass through is Bnow, enable B1=Bnow, from obtaining BnowMoment, Bnow1It is newest one
The geomagnetic field intensity of secondary acquisition, Bpre1For data Bnow1A upper period acquisition geomagnetic field intensity, work as Bpre1-Bnow1>ΔB1When,
Wherein, Δ B1For given threshold, B is enabled2=Bpre1, calculate from there is geomagnetic field intensity BnowStart to there is geomagnetic field intensity
Bpre1This period geomagnetic sensor has the geomagnetic field intensity number N acquired, the geomagnetic field intensity change rate altogether are as follows:Wherein, BsFor the geomagnetic field intensity change rate of geomagnetic sensor X-axis, T is the week of geomagnetic sensor sampling
Phase；
B2For the geomagnetic field intensity maximum value of X-axis, and Δ B1Setting so that the geomagnetic field intensity maximum value of X-axis appears in vehicle
Reach geomagnetic field intensity right above before.
2. the method according to claim 1 based on single geomagnetic sensor measurement car speed, which is characterized in that the step
Further include step 11 between rapid 1 and step 2:
Step 11: vehicle being judged whether there is according to the geomagnetic field intensity of acquisition and is passed through, executes step if nothing if so, executing step 2
Rapid 1.
3. the method according to claim 2 based on single geomagnetic sensor measurement car speed, which is characterized in that the step
Rapid 11 further are as follows:
The geomagnetic field intensity that the geomagnetic field intensity that current period obtains was obtained with a upper period is compared, if being more than setting threshold
Value has then regarded as vehicle process, executes step 2, otherwise, regards as no vehicle and passes through, execute step 1.
4. the method according to claim 1 based on single geomagnetic sensor measurement car speed, which is characterized in that the step
In rapid 3, the geomagnetic field intensity change rate B of measured in advancesWith the relationship of car speed v are as follows:
V=aBs 3+bBs 2+cBs+d (1)
Wherein, a, b, c, d are constant；
The determination method of constant a, b, c, d are as follows in formula (1):
The geomagnetic field intensity data under different vehicle speed v are acquired with the same period, the earth magnetism of X-axis is acquired according to the step 2
Field intensity change rate Bs, obtain multiple groups Bs- v data obtain constant a, b, c, d using least square method matched curve.
5. a kind of device based on single geomagnetic sensor measurement car speed characterized by comprising
Acquisition module: for obtaining geomagnetic field intensity in multiple periods that geomagnetic sensor acquires in real time；The geomagnetic sensor
For being arranged under road；
First computing module: for geomagnetic field intensity change rate to be calculated；
Second computing module: for being become according to obtained geomagnetic field intensity change rate and the geomagnetic field intensity of measured in advance
The relationship of rate and car speed, is calculated car speed；
The geomagnetic sensor is three axis geomagnetic sensors, and the geomagnetic field intensity is the geomagnetic field intensity of geomagnetic sensor X-axis,
The direction of the X-axis of the geomagnetic sensor is parallel with direction of traffic, and first computing module is further used for:
Geomagnetic field intensity when judging to have vehicle to pass through is Bnow, enable B1=Bnow, from obtaining BnowMoment, Bnow1It is newest one
The geomagnetic field intensity of secondary acquisition, Bpre1For data Bnow1A upper period acquisition geomagnetic field intensity, work as Bpre1-Bnow1>ΔB1When,
Wherein, Δ B1For given threshold, B is enabled2=Bpre1, calculate from there is geomagnetic field intensity BnowStart to there is geomagnetic field intensity
Bpre1This period geomagnetic sensor has the geomagnetic field intensity number N acquired, the geomagnetic field intensity change rate altogether are as follows:Wherein, BsFor the geomagnetic field intensity change rate of geomagnetic sensor X-axis, T is the week of geomagnetic sensor sampling
Phase；
B2For the geomagnetic field intensity maximum value of X-axis, and Δ B1Setting so that the geomagnetic field intensity maximum value of X-axis appears in vehicle
Reach geomagnetic field intensity right above before.
6. the device according to claim 5 based on single geomagnetic sensor measurement car speed, which is characterized in that the base
In the device of single geomagnetic sensor measurement car speed further include:
Judgment module: vehicle is judged whether there is for the geomagnetic field intensity according to acquisition and is passed through.
7. the device according to claim 6 based on single geomagnetic sensor measurement car speed, which is characterized in that described to sentence
Disconnected module, is further used for:
The geomagnetic field intensity that current period obtains is compared with the geomagnetic field intensity that upper a cycle obtains, if being more than setting
Threshold value has then regarded as vehicle process, otherwise, regards as no vehicle and passes through.
8. the device according to claim 5 based on single geomagnetic sensor measurement car speed, which is characterized in that described the
In two computing modules, preset geomagnetic field intensity change rate BsWith the relationship of car speed v are as follows:
V=aBs 3+bBs 2+cBs+d (2)
Wherein, a, b, c, d are constant, and the determination method of constant a, b, c, d are as follows in formula (2):
The geomagnetic field intensity data under different vehicle speed v are acquired with the same period, acquire X-axis according to first computing module
Geomagnetic field intensity change rate Bs, obtain multiple groups Bs- v data obtain constant a, b, c, d using least square method matched curve.
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