CN112037533B - Vehicle passing detection method of geomagnetic sensing type spike - Google Patents
Vehicle passing detection method of geomagnetic sensing type spike Download PDFInfo
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Abstract
The invention belongs to the technical field of intelligent transportation, and particularly relates to a vehicle passing detection method of a geomagnetic sensing type spike.
Description
Technical Field
The invention belongs to the technical field of intelligent traffic, and particularly relates to a vehicle passing detection method of a geomagnetic sensing type spike.
Background
The traffic flow is based on the number of vehicles passing through a road section in a certain time, and the formula for the traffic flow is as follows: traffic flow = number of passing vehicles/time.
The traffic flow data is the most core data for evaluating the road traffic condition and is one of the parameters which most intuitively reflect the current traffic state of the road, so when the road traffic condition is detected, the traffic flow data is often required to be acquired.
In the prior art, the most common vehicle flow data acquisition technologies include a video-based vehicle flow detector, an infrared-based vehicle flow detection system, a radar-based vehicle flow detection system, an ultrasonic-based vehicle flow detection system and the like, but these methods all have different defects, for example, a video vehicle flow detector has the disadvantage that a professional chip capable of performing image recognition is required through camera image recognition, so that the cost is high, the power consumption is high, and only a place with mains supply can be installed, the risk of camera failure cannot be completely avoided even in a visual recognition mode under scenes with poor illumination conditions such as night and the like, and clear camera shooting cannot be performed in special weather such as rain, snow, fog and the like; similarly, the vehicle flow detection system based on infrared detection is influenced by the heat source of the vehicle and the working environment, and the noise resistance is weak; the detection precision of the ultrasonic-based traffic flow detection system is not high, the detection distance is short, and the ultrasonic-based traffic flow detection system is easily influenced by external environmental factors; the radar-based traffic flow detection system is expensive and not suitable for road sections with high traffic density and low speed.
For example, in the chinese patent publication of CN102063795B entitled "a dense traffic flow information collection system, method and apparatus", disclosing a dense traffic flow information collection system, by obtaining the vehicle body running speed and the running speed of each set of wheels in the time interval between each vehicle body shielding and leaving of two sets of laser detectors in the measurement range between two sets of laser detectors, and comparing the vehicle body running speed and the running speed of each set of wheels, the traffic volume and the vehicle speed of the monitored road are obtained, the measurement accuracy of the traffic information can be improved, the vehicle shielding and the cross-lane running condition can be distinguished, the measurement accuracy is improved, but this laser detection type needs a laser transmitter and a laser receiver, like there is no isolation zone in the middle of the road in the urban area, and under the condition that multiple vehicles are in parallel, the vehicle is judged to have a vehicle because the vehicle forms shielding to the laser, then do not easily distinguish when the vehicle is parallel to form the laser instrument simultaneously and shelter from, just need extra detection device to lead to with high costs, the consumption is high as detecting, and partial truck, freight train intermediate structure have the space moreover, also can see through laser for laser repeated computation causes the false retrieval.
Now, a traffic flow detection method based on a geomagnetic sensor is emerging, and as disclosed in the patent publication with the publication number of CN110310495A entitled "cooperative traffic flow detection method and traffic flow detection system", a traffic flow detection system is disclosed, which comprises a data acquisition unit and a data processing unit in communication connection with the data acquisition unit, wherein the data acquisition unit comprises a plurality of intelligent spikes paved in the same section of a driving road, and each intelligent spike is used for detecting position data of a running vehicle, so as to form a vehicle detection point; the data acquisition unit receives position data of running vehicles sent by each intelligent spike, sets a plurality of vehicle detection points for detecting the positions of the vehicles on a running road, judges the relative position of each running vehicle in the lane and the corresponding vehicle detection point, and performs cooperative comprehensive judgment by combining the number of lanes of the running road, so as to obtain the traffic flow of the running road. However, many details of the geomagnetic sensor measurement method in this scheme are not considered, a double-window method is used for judging, the length of the window cannot be automatically adjusted, a reasonable threshold value is selected, a window for detecting vehicle-coming and a window for detecting vehicle-going are judged according to whether the change of data in the window exceeds the threshold value or not and a certain time is kept, and the vehicle-going and the vehicle-coming are judged. At high speeds, the speed of the truck may vary from road section to road section, even though the truck may be travelling at very low speeds (e.g. 40 km/h) for the same road section, and the truck may be travelling at very high speeds (e.g. 110 km/h). If the window is set to be small, the sensor is easily triggered by interference (power supply fluctuation, abnormal work of the sensor or a chip, interference of part of vehicle structures). If the setting is too large, the vehicle with the fast speed can not be detected, and the vehicle with the fast speed is mistakenly judged as one vehicle. The truck and the wagon are long in length, the middle of the vehicle is provided with a plurality of connecting structures, the geomagnetic sensor can change very little, the geomagnetic sensor can walk slowly, the carriage passing through the connecting structures can be mistakenly judged as the carriage walking, and no automatic recovery mechanism is provided. For example, the sensor only detects that a vehicle comes once, but does not detect that the vehicle is moved all the time, and the sensor can be stuck in the link and is always out of work. Such as a vehicle coming and stopping over the sensor, or starting with a vehicle or other metal object over the sensor and then moving away again. The change of the posture of the sensor can cause a large change of the acquired data, and the acquired data cannot be recovered below a threshold value, so that the failure is caused. Such as if the device is subjected to a roll tilt or turn of a large vehicle.
Disclosure of Invention
In order to overcome the problems and disadvantages in the prior art, the present invention aims to provide a vehicle passing state detection method for determining a vehicle passing state through a magnetic field intensity variation state based on a distributed arrangement of geomagnetic sensing type spikes.
The purpose of the invention is realized by the following technical scheme:
the vehicle passing detection method of the geomagnetic sensing type spike is characterized by comprising the following steps: the geomagnetic sensing type spike is arranged on a road surface for detecting the passing of vehicles in a road section and is connected into the gateway through the repeater according to groups, the geomagnetic sensing type spike uploads geomagnetic fluctuation data to the repeater, and the repeater judges whether a geomagnetic fluctuation intensity value acquired by the geomagnetic sensing type spike and a corresponding fluctuation time length accord with a standard for passing of the vehicles according to a set geomagnetic fluctuation intensity threshold and a fluctuation time length threshold of the vehicles, specifically, the geomagnetic fluctuation intensity of the magnetic sensing type spike is not less than a threshold B when the vehicles pass throughstAnd in order to prevent false triggering of the geomagnetic sensor spike by flying gravel and the like, the geomagnetic fluctuation intensity of the geomagnetic sensor spike is set to be not less than the threshold B when the vehicle passes through according to the classic prior value of the triggering action time of the geomagnetic sensor spike when the vehicle passes throughstShould not be less than Tst(ii) a The earth magnetic field is almost stable and unchanged in a small area, when the periphery of the earth magnetic field is influenced by magnetic metals such as iron, nickel, cobalt and the like, the earth magnetic field is distorted, the earth magnetic sensor judges the vehicle passing by sensing the change of the magnetic field, the magnetic field B (x, y, z) of each earth magnetic sensing type spike is a three-dimensional space vector and has the size attribute and the direction attribute, namely the mode of the earth magnetic sensing type spike, namely the magnetic field intensity is | B | =
In the working state, a magnetic field reference value B of the geomagnetic sensing type spike when no vehicle passes is setbase（xbase，ybase，zbase) The magnetic field of the current working moment of the geomagnetic sensing type spike is B0（x0，y0，z0) Then, then
Recording the magnetic field variation Δ Bbase=B0-BbaseI.e. the strength of the magnetic field change is | Δ Bbase|，
When the magnetic field changes intensity | Δ Bbase| exceeds the set threshold Δ BstAnd the magnetic field variation strength | Δ BbaseThe time length T of | exceeding the set threshold exceeds the set time length threshold TstIf so, the vehicle is judged to pass. The threshold value deltaB of the magnetic field variation strength may cause different threshold values to be set for different roads due to road trend, latitude, altitude, system errors, device aging and the likestAnd the magnetic field variation trigger time TstCan be automatically set. And due to system circuit error, temperature drift, device aging and the like, the magnetic field change strength threshold value delta B can be greatly changed in the yearsstAnd the magnetic field variation trigger time TstCan be automatically updated.
Yet further, when the threshold value Δ B of the intensity of the magnetic field change is setstWhen the vehicle is large, when two or more section vehicles such as trucks and vans are encountered, the two or more sections vehicles are pulled by the vehicle head through the structure, the magnetic field change twice before and after the intermediate connection structure passes through the structure is very small, the vehicles move slowly, and the intermediate connection structure can lead the magnetic field change to be continuously lower than the magnetic field change strength threshold delta B for a period of time after passing through the structurestThe default of the system is that the vehicle passes through, and the magnetic field change strength exceeding the threshold value delta B is triggered again when the subsequent container passes throughstIf the vehicle is judged to pass by more than one vehicle, the threshold value delta B is simply setstThe adjustment is small, and the probability of false triggering detection is increased due to the fact that a large vehicle passes by a next lane.
Therefore, preferably, in the vehicle passage determination step, the magnetism sensing type spike detects a vehicle passage signal, specifically:
step 1, in a working state, after the geomagnetic sensing type spike is started, collecting magnetic field data of a channel at a set Time interval (10 ms) and preprocessing, wherein the preprocessing is to take an average value of N (5) newly collected magnetic field data before the current Time as a magnetic field reference value Bbase；
Step 2, calculating the magnetic field B at the current moment0And a magnetic field reference value BbaseMagnetic field fluctuation intensity | Δ B therebetweenbaseIf the magnetic field fluctuation intensity is | Δ Bbase| is less than a set threshold Δ BstAnd the duration exceeds the set duration TstThen record the magnetic field B at the current moment0As a magnetic field reference value, and adjusting the magnetic field fluctuation intensity threshold value delta B according to the intensity of the magnetic field at the moment0Duration threshold T0And a magnetic field reference value B0And then, changing the current detection section into a vehicle-free state, and formally starting vehicle detection by the geomagnetic sensing type spike, or returning to the step 1 again.
Step 3, calculating the magnetic field B of the geomagnetic sensing type spike at the current working moment after the formal start of the vehicle detection1And is compared with a magnetic field reference value B as a reference value0Calculating the field fluctuation strength | Delta B | and calculating the field fluctuation strength | Delta B | according to | Delta B | and the set magnetic field fluctuation strength threshold Delta B0And a corresponding duration threshold T0Judging whether the current trigger is a vehicle solution and a passing, false trigger or no vehicle passing, specifically:
if the magnetic field fluctuation strength | Δ B | exceeds the threshold value Δ B0And the duration exceeds T0Confirming that a vehicle is approaching and passing;
if the magnetic field fluctuation strength | Δ B | exceeds the threshold value Δ B0And the duration is less than T0Confirming that the trigger is false trigger;
if the magnetic field fluctuation strength | Δ B | does not exceed the threshold value Δ B0It is considered that no vehicle passes and reference value following is performed, i.e. with the magnetic field B currently as the reference value0Magnetic field B corresponding to current working moment1Averaging again according to the weight as a new magnetic field reference value Bbase。
In step 3, if it is determined that a vehicle is approaching and passing, the vehicle will either leave after passing or stop, or the trigger is mistakenly triggered by a large oncoming vehicle due to vehicle type difference, the magnetic field B of the geomagnetic sensor type spike needs to pass through in the passing process of the vehicle2And the last time as the reference valueMagnetic field B1The magnetic field fluctuation strength | Δ B' | is used for further judging whether the current vehicle normally passes through or stops or the adjacent channel large-scale vehicle passes through to cause false triggering, specifically:
if the magnetic field fluctuation strength | delta B' | exceeds the set magnetic field fluctuation strength threshold value delta B1And the duration exceeds the set duration T1But less than a set time period T2If the vehicle is judged to pass through normally, the vehicle will be reported to pass through and return to the no-vehicle state; if | Δ B' | exceeds the set magnetic field fluctuation strength threshold value Δ B1And the duration exceeds the set duration T2The vehicle is considered to be stopped, the vehicle is judged to enter a parking state, the vehicle stops firstly and then goes, and the sensor is rotated, so that the same effect is achieved; preferably, if the duration T1In the interior, the magnetic field change greater than delta B appears temporarily0The vehicle is also considered to pass normally, the change may be caused by the hollow structure of the vehicle in the process of passing the trailer, and the short time can be set according to the actual road condition and the classical speed;
if the magnetic field fluctuation intensity is | delta B' | in the set time length T1Exceeds the set magnetic field fluctuation strength threshold value Delta B2But less than the threshold deltab1If the number of times of the channel is equal to or exceeds the set number of times N, judging that the adjacent channel large-scale vehicle passes through to cause false triggering;
wherein the threshold value Delta B2<ΔB1<ΔB0，ΔB1Is the classic value of the change of the magnetic field fluctuation intensity of a common small vehicle at the current moment and the previous moment in the normal passing process, delta B2The method is a classic value of the fluctuation intensity change of the magnetic field when a large vehicle on an adjacent road passes through the magnetic field to cause a false triggering state. Namely, Delta B0For determining the coming process, Δ B1For determining the course of the vehicle, and Δ B2Disturbance data for determining whether the vehicle is a next-door lane; wherein, part of the vehicles have the characteristic of hollow structure in the middle, the structure has small disturbance to the earth magnetic field, and the threshold value Delta B1The vehicle-driving-away judgment is carried out by using a smaller threshold value, so that misjudgment cannot occur, and if a larger threshold value is used, the part of the hollow structure can be considered as the vehicle-driving-away judgmentAfter the vehicle is started, judging that the subsequently connected compartment is one vehicle, so that more judgments are caused; when a large vehicle or a vehicle with high iron content approaches and passes through the next-door lane, the magnetic field change exceeds the threshold value delta B during the determination0When it is determined that a vehicle passes through the magnetic field sensor, the magnetic field disturbance has a characteristic of rapidly attenuating with distance increase, and the magnetic field changes even if the magnetic field exceeds Δ B0But the magnetic field change Δ B during the passage of the disturbance2Or much less than the magnetic field change deltab caused by passing over the vehicle directly above the sensor1Therefore, the threshold value Δ B is set1And Δ B2Judging whether the lane crossing interference of the next door exists, if so, judging that a vehicle approaches and passes through, but the magnetic field change is larger than delta B in the passing process2But less than Δ B1In case of exceeding Δ B2If the number of times exceeds the set number of times N, it is determined that the next vehicle has passed through the lane, and false triggering is caused.
The vehicle passing determination step further comprises a vehicle passing speed and vehicle length calculation step, specifically, the arrangement distance between two adjacent spikes in a group of spikes of the repeater is set to be L, and the current time t is recorded when the repeater determines that the vehicle approaches in the road driving direction and passes through the group of the first geomagnetic sensing spikes1And the vehicle passes through the duration T of a first geomagnetic sensing type spike and receives a vehicle passing detection signal of a second geomagnetic sensing type spike of the group in the road driving direction, and records the current time T when the vehicle is judged to be close to and pass2If the current vehicle speed is V = L/(t)2-t1) The current vehicle length S = T × V.
Has the advantages that:
compared with the prior art, the technical scheme provided by the invention has the advantages that multiple groups of the magnetic induction function-based only-capable spikes are arranged on the driving road, the spikes are networked through the repeater and the gateway, the time division multiplexing control is carried out on the spike groups according to the use environment and the requirement, the geomagnetic induction type spikes sense the fluctuation of the magnetic field when the vehicle passes through, the passing state of the vehicle can be judged by monitoring the fluctuation intensity value of the magnetic field, the sensor is installed in the middle of the road, the data change of the sensor is obvious, the interference signal and the real vehicle passing signal can be distinguished more easily, the accuracy is improved, the installation is fixed and convenient, the direction does not need to be fixed, any installation direction is realized, the construction and installation are convenient, and the device is suitable for different regions.
Whether the corresponding vehicle passing state under the fluctuation intensity of the magnetic field of each spike is the passing state of the vehicle passing through a detection road is judged by setting a threshold value, in order to further increase the precision, a processing mode of judging threshold value self-adaptive adjustment and multiple threshold value judgment for judging a single spike is also set, the conditions of error triggering calculation and the like can be effectively avoided, a plurality of threshold values are used, the interference of special vehicle types is filtered, the interference of vehicles in lanes at the next door is filtered, state machine programming is adopted, logic jumping is clear, more special conditions such as parking, data jitter and the like are identified, an automatic recovery mechanism is set, even if a detection error occurs at one time, data is abnormal, or a temporary sensor chip fails and the like, the automatic recovery mechanism can quickly recover, the events of parking and the sensor is steered only caused by inaccurate detection, the automatic recovery mechanism can be realized, After a few seconds, the vehicle can automatically jump to a non-vehicle state, then the vehicle can normally work, and the magnetic induction design can work in special weather at night in the day.
Drawings
The foregoing and following detailed description of the invention will be apparent when read in conjunction with the following drawings, in which:
FIG. 1 is a schematic diagram illustrating the distribution of the geomagnetic sensing spike of the present invention;
FIG. 2 is a schematic representation of a logical relationship of the approach and passage of a vehicle under test of the present invention;
FIG. 3 is a schematic diagram of a logical relationship during a vehicle passing process of the present invention;
FIG. 4 is a schematic diagram of the waveform of the variation of the intensity of the magnetic wave in time of approaching and passing the present invention;
fig. 5 is a schematic diagram of waveforms of intensity variations of geomagnetic waves during a vehicle passing process according to the present invention.
Detailed Description
The technical solutions for achieving the objects of the present invention are further illustrated by the following specific examples, and it should be noted that the technical solutions claimed in the present invention include, but are not limited to, the following examples.
Examples
As a specific embodiment of the traffic flow detection system of the present invention, a method for detecting vehicle passing by a geomagnetic sensor spike, as shown in fig. 1, includes arranging the geomagnetic sensor spike on a road surface on which vehicles pass in a detection road section, connecting the geomagnetic sensor spike to a gateway by a repeater in groups, uploading geomagnetic fluctuation data to the repeater by the geomagnetic sensor spike, and determining, by the repeater, whether a geomagnetic fluctuation intensity value acquired by the geomagnetic sensor spike and a corresponding fluctuation time length meet a criterion for passing the vehicle according to a set geomagnetic fluctuation intensity threshold and a fluctuation time length threshold for passing the vehicle, specifically, setting a geomagnetic fluctuation intensity of the geomagnetic sensor spike to be not less than a threshold B when the vehicle passes the detection systemstAnd in order to prevent false triggering of the geomagnetic sensor spike by flying gravel and the like, the geomagnetic fluctuation intensity of the geomagnetic sensor spike is set to be not less than the threshold B when the vehicle passes through according to the classic prior value of the triggering action time of the geomagnetic sensor spike when the vehicle passes throughstShould not be less than Tst(ii) a The earth magnetic field is almost stable and unchanged in a small area, when the periphery of the earth magnetic field is influenced by magnetic metals such as iron, nickel, cobalt and the like, the earth magnetic field is distorted, the earth magnetic sensor judges the vehicle passing by sensing the change of the magnetic field, the magnetic field B (x, y, z) of each earth magnetic sensing type spike is a three-dimensional space vector and has the size attribute and the direction attribute, namely the mode of the earth magnetic sensing type spike, namely the magnetic field intensity is | B | =
In the working state, a magnetic field reference value B of the geomagnetic sensing type spike when no vehicle passes is setbase（xbase，ybase，zbase) The magnetic field of the current working moment of the geomagnetic sensing type spike is B0（x0，y0，z0) Then, then
Recording the magnetic field variation Δ Bbase=B0-BbaseI.e. the strength of the magnetic field change is | Δ Bbase|，
When the magnetic field changes intensity | Δ Bbase| exceeds the set threshold Δ BstAnd the magnetic field variation strength | Δ BbaseThe time length T of | exceeding the set threshold exceeds the set time length threshold TstIf so, the vehicle is judged to pass. The threshold value deltaB of the magnetic field variation strength may cause different threshold values to be set for different roads due to road trend, latitude, altitude, system errors, device aging and the likestAnd the magnetic field variation trigger time TstCan be automatically set. And due to system circuit error, temperature drift, device aging and the like, the magnetic field change strength threshold value delta B can be greatly changed in the yearsstAnd the magnetic field variation trigger time TstCan be automatically updated.
However, when the threshold value Δ B of the intensity of the magnetic field change is setstWhen the vehicle is large, when two or more section vehicles such as trucks and vans are encountered, the two or more sections vehicles are pulled by the vehicle head through the structure, the magnetic field change twice before and after the intermediate connection structure passes through the structure is very small, the vehicles move slowly, and the intermediate connection structure can lead the magnetic field change to be continuously lower than the magnetic field change strength threshold delta B for a period of time after passing through the structurestThe default of the system is that the vehicle passes through, and the magnetic field change strength exceeding the threshold value delta B is triggered again when the subsequent container passes throughstIf the vehicle is judged to pass by more than one vehicle, the threshold value delta B is simply setstThe adjustment is small, and the probability of false triggering detection is increased due to the fact that a large vehicle passes by a next lane.
Therefore, as shown in fig. 2 and 3, the sensors are preferably buried in the road surface, and after being activated, the sensors start collecting magnetic field data at a set time interval (e.g., 10 ms) and preprocess the magnetic field data in such a way that the latest 5 magnetic field data are always averaged. The method comprises the steps of always calculating magnetic field fluctuation by comparing current magnetic field data with magnetic field data before set interval time (such as 50 ms), if the fluctuation is not large and the duration exceeds 1s (if the fluctuation is large for one time in the midway, the magnetic field data is re-timed), recording the magnetic field data at the moment, taking the magnetic field data as a reference value, adjusting three threshold values according to the intensity of the magnetic field at the moment, then changing to a vehicle-free state, formally starting vehicle detection, continuously acquiring data by a sensor, and calculating the magnetic field change of the magnetic field data at the moment compared with the reference value.
Specifically, in the vehicle passage determination step, the geomagnetic sensor type spike detection vehicle passage signal includes the steps of:
step 1, in a working state, after the geomagnetic sensing type spike is started, collecting magnetic field data of a channel at a set Time interval (10 ms) and preprocessing, wherein the preprocessing is to take an average value of N (5) newly collected magnetic field data before the current Time as a magnetic field reference value Bbase；
Step 2, calculating the magnetic field B at the current moment0And a magnetic field reference value BbaseMagnetic field fluctuation intensity | Δ B therebetweenbaseIf the magnetic field fluctuation intensity is | Δ Bbase| is less than a set threshold Δ BstAnd the duration exceeds the set duration TstThen record the magnetic field B at the current moment0As a magnetic field reference value, and adjusting the magnetic field fluctuation intensity threshold value delta B according to the intensity of the magnetic field at the moment0Duration threshold T0And a magnetic field reference value B0And then, changing the current detection section into a vehicle-free state, and formally starting vehicle detection by the geomagnetic sensing type spike, or returning to the step 1 again. The magnetic field fluctuation intensity threshold value, the duration threshold value and the magnetic field reference value are all formed by weighting ratio of an empirical value and the current magnetic field intensity; because the same zone, the magnitude and the direction of the earth magnetic field are almost the same, and the larger the magnetic field intensity measured by different sensors due to system errors, temperature, direction and the like is, the more sensitive the sensors are, and the slower the sensors are measured to be. If T1 is preferably set to 400 according to a number of experiments at a field strength of 20000, some sensors are relatively insensitive, and the measured field strength is 15000, the threshold TI should preferably be 15000/20000 x 400= 300.
Step 3, calculating the geomagnetic sensing type spike after the vehicle detection is formally startedMagnetic field B at present working moment1And is compared with a magnetic field reference value B as a reference value0Calculated field fluctuation intensity | Δ B |:
if the magnetic field fluctuation strength | Δ B | exceeds the threshold value Δ B0And the duration exceeds T0Confirming that a vehicle is approaching and passing;
if the magnetic field fluctuation strength | Δ B | exceeds the threshold value Δ B0And the duration is less than T0Confirming that the trigger is false trigger;
if the magnetic field fluctuation strength | Δ B | does not exceed the threshold value Δ B0It is considered that no vehicle passes and reference value following is performed, i.e. with the magnetic field B currently as the reference value0Magnetic field B corresponding to current working moment1Averaging again according to the weight as a new magnetic field reference value Bbase. When the power-on reset state is switched to the non-vehicle state, the reference value is completely refreshed, namely the magnetic field data at the current moment is directly used for replacing the old reference value, and the reference value is refreshed in the non-vehicle state, namely the reference value is updated according to the weight ratio. Such as: and (3) carrying out reference value following refreshing on the new reference value = (the old reference value 7+ the magnetic field data at the moment)/8 according to the weight of 7:1, so that if interference occurs once at a time, the influence degree of the interference data on the new reference value can only account for one eighth, the influence is small, if the change is normal, along with the following refreshing of a plurality of reference values, the influence degree of the old reference value data on the new reference value is continuously smaller, and finally the new reference value is continuously approached. If the magnetic field changes greatly, the vehicle is judged and the reference value is not refreshed.
Preferably, in step 3, if it is determined that a vehicle is approaching and passing, the vehicle will either leave after passing or stop, or the trigger is triggered by a large vehicle approaching the road by mistake due to vehicle type difference, the magnetic field B of the geomagnetic sensor type spike needs to pass through during the passing process of the vehicle2And the magnetic field B at the last moment as a reference value1The magnetic field fluctuation strength | Δ B' | is used for further judging whether the current vehicle normally passes through or stops or the adjacent channel large-scale vehicle passes through to cause false triggering, specifically:
if the magnetic field fluctuates in intensity| Δ B' | exceeds the set magnetic field fluctuation intensity threshold Δ B1And the duration exceeds the set duration T1But less than a set time period T2If the vehicle is judged to pass through normally, the vehicle will be reported to pass through and return to the no-vehicle state; if | Δ B' | exceeds the set magnetic field fluctuation strength threshold value Δ B1And the duration exceeds the set duration T2The vehicle is considered to be stopped, the vehicle is judged to enter a parking state, the vehicle stops firstly and then goes, and the sensor is rotated, so that the same effect is achieved; preferably, if the duration T1In the interior, the magnetic field change greater than delta B appears temporarily0The vehicle is also considered to pass normally, the change may be caused by the hollow structure of the vehicle in the process of passing the trailer, and the short time can be set according to the actual road condition and the classical speed;
if the magnetic field fluctuation intensity is | delta B' | in the set time length T1Exceeds the set magnetic field fluctuation strength threshold value Delta B2But less than the threshold deltab1If the number of times of the channel is equal to or exceeds the set number of times N, judging that the adjacent channel large-scale vehicle passes through to cause false triggering;
wherein the threshold value Delta B2<ΔB1<ΔB0，ΔB1Is the classic value of the change of the magnetic field fluctuation intensity of a common small vehicle at the current moment and the previous moment in the normal passing process, delta B2The method is a classic value of the fluctuation intensity change of the magnetic field when a large vehicle on an adjacent road passes through the magnetic field to cause a false triggering state. Namely, Delta B0For determining the coming process, Δ B1For determining the course of the vehicle, and Δ B2Disturbance data for determining whether the vehicle is a next-door lane; wherein, part of the vehicles have the characteristic of hollow structure in the middle, the structure has small disturbance to the earth magnetic field, and the threshold value Delta B1The vehicle walking is judged by using a smaller threshold value, so that misjudgment cannot occur, if the larger threshold value is used, the part of the hollow structure is possibly considered to be that the vehicle leaves, and then the subsequently connected compartment is judged to be one vehicle, so that more judgments are caused; when a large vehicle or a vehicle with high iron content approaches and passes through the next-door lane, the magnetic field change exceeds the threshold value delta B during the determination0And is determined to haveWhen a vehicle passes, the magnetic field changes even if the magnetic field exceeds Δ B due to the characteristic that the magnetic field disturbance has sharp attenuation with the increase of the distance0But the magnetic field change Δ B during the passage of the disturbance2Or much less than the magnetic field change deltab caused by passing over the vehicle directly above the sensor1Therefore, the threshold value Δ B is set1And Δ B2Judging whether the lane crossing interference of the next door exists, if so, judging that a vehicle approaches and passes through, but the magnetic field change is larger than delta B in the passing process2But less than Δ B1In case of exceeding Δ B2If the number of times exceeds the set number of times N, it is determined that the next vehicle has passed through the lane, and false triggering is caused.
The vehicle passing determination step further comprises a vehicle passing speed and vehicle length calculation step, specifically, the arrangement distance between two adjacent spikes in a group of spikes of the repeater is set to be L, and the current time t is recorded when the repeater determines that the vehicle approaches in the road driving direction and passes through the group of the first geomagnetic sensing spikes1And the vehicle passes through the duration T of a first geomagnetic sensing type spike and receives a vehicle passing detection signal of a second geomagnetic sensing type spike of the group in the road driving direction, and records the current time T when the vehicle is judged to be close to and pass2If the current vehicle speed is V = L/(t)2-t1) The current vehicle length S = T × V.
Specifically, according to the use requirement, the approaching and passing detection time of the vehicle is determined by the fastest vehicle speed, the minimum vehicle length and the sampling frequency. If the vehicle length is 4m and the vehicle speed is 120km \ h, the vehicle passes through the spike for 120ms approximately, sampling is carried out at a sampling frequency of 10ms, the sensor can only acquire data for 12 times, and the detection time for the vehicle to approach and pass is smaller than the calculated minimum time, so that the minimum vehicle can be detected.
The passing time of the vehicle is determined by the fastest speed, the minimum following distance and the sampling frequency. If the minimum following distance is 20m and the maximum speed is 120km \ h, the time without the vehicle is about 600ms, and the time when the vehicle passes through the vehicle is smaller than the value, so that the continuous following vehicle cannot be mistakenly judged as one vehicle.
The continuous passing time of the vehicle is determined according to the longest vehicle type and the slowest vehicle speed, for example, the vehicle length is 20m, the vehicle speed is 40km \ h, the time of the vehicle passing through the sensor is about 1.8s, the vehicle cannot be parked at will on the highway, and the parking detection time is set to be 4s in the scheme. If the vehicle can be parked on some road sections, the vehicle can be parked for a longer time than the longest time.
Claims (2)
1. The vehicle passing detection method of the geomagnetic sensing type spike is characterized in that the geomagnetic sensing type spike is arranged on a road surface for detecting the passing of vehicles in a road section and is connected into a gateway through a repeater according to groups, the geomagnetic sensing type spike uploads geomagnetic fluctuation data to the repeater, the repeater judges whether a geomagnetic fluctuation intensity value acquired by the geomagnetic sensing type spike and a corresponding fluctuation duration meet the passing standard of the vehicle according to a set geomagnetic fluctuation intensity threshold and a fluctuation duration threshold of the vehicle, and the geomagnetic fluctuation intensity of the geomagnetic sensing type spike is not less than a threshold B when the vehicle passes through the set geomagnetic fluctuation intensity value and the corresponding fluctuation duration threshold, so that the geomagnetic fluctuation intensity of the geomagnetic sensing type spike is set to be not less thanstSetting and judging that the geomagnetic fluctuation intensity of the geomagnetic sensing type spike is not less than a threshold B when the vehicle passes through according to a classic prior value of the triggering action time of the geomagnetic sensing type spike when the vehicle passes throughstShould not be less than Tst(ii) a The magnetic field B (x, y, z) of each geomagnetic sensing spike is a three-dimensional space vector, that is, the magnitude of the magnetic field intensity of the geomagnetic sensing spike is | B | =
In the working state, a magnetic field reference value B of the geomagnetic sensing type spike when no vehicle passes is setbase（xbase，ybase，zbase) The magnetic field of the current working moment of the geomagnetic sensing type spike is B0（x0，y0，z0) Then, then
Recording the magnetic field variation Δ Bbase=B0-BbaseI.e. the strength of the magnetic field change is | Δ Bbase|，
When the magnetic field changes intensity | Δ Bbase| exceeds the set threshold Δ BstAnd the magnetic field variation strength | Δ BbaseThe time length T of | exceeding the set threshold exceeds the set time length threshold TstAnd if so, judging that the vehicle passes, specifically:
step 1, in a working state, after the geomagnetic sensing type spike is started, collecting magnetic field data of a channel at a set time interval of 10ms and preprocessing the magnetic field data, wherein the preprocessing is to take an average value of 5 newly collected magnetic field data before the current moment as a magnetic field reference value Bbase；
Step 2, calculating the magnetic field B at the current moment0And a magnetic field reference value BbaseMagnetic field fluctuation intensity | Δ B therebetweenbaseIf the magnetic field fluctuation intensity is | Δ Bbase| is less than a set threshold Δ BstAnd the duration exceeds the set duration TstThen record the magnetic field B at the current moment0As a magnetic field reference value, and adjusting the magnetic field fluctuation intensity threshold value delta B according to the intensity of the magnetic field at the moment0Duration threshold T0And a magnetic field reference value, then changing the current detection section into a vehicle-free state, and formally starting vehicle detection by the geomagnetic sensing type spike, otherwise returning to the step 1 again;
step 3, calculating the magnetic field B of the geomagnetic sensing type spike at the current working moment after the formal start of the vehicle detection1And B as the current field reference value0Calculating the fluctuation intensity of the magnetic field | Delta B | and setting a threshold value Delta B of the fluctuation intensity of the magnetic field according to the | Delta B |, the threshold value Delta B0And a corresponding duration threshold T0Judging whether the current trigger is a vehicle solution and passes, a false trigger or no vehicle passes;
in the step 3, according to | Δ B | and the set magnetic field fluctuation strength threshold value Δ B0And a corresponding duration threshold T0Judging whether the current trigger is a vehicle solution and a passing, false trigger or no vehicle passing, specifically:
if the magnetic field fluctuation strength | Δ B | exceeds the threshold value Δ B0And the duration exceeds T0Confirming that a vehicle is approaching and passing;
if the magnetic field fluctuation strength | Δ B | exceeds the threshold value Δ B0And the duration is less than T0Confirming that the trigger is false trigger;
if the magnetic field fluctuation strength | Δ B | does not exceed the threshold value Δ B0No vehicle is considered to pass and reference value following is performed, i.e. with the magnetic field B present as reference value0Magnetic field B corresponding to current working moment1Averaging again according to the weight as a new magnetic field reference value Bbase；
If a vehicle is judged to approach and pass, the magnetic field B of the geomagnetic sensing type spike is required to pass through the vehicle in the passing process2And the magnetic field B at the last moment as a reference value1The magnetic field fluctuation strength | Δ B' | is used for further judging whether the current vehicle normally passes through or stops or the adjacent channel large-scale vehicle passes through to cause false triggering, specifically:
if the magnetic field fluctuation strength | delta B' | exceeds the set magnetic field fluctuation strength threshold value delta B1And the duration exceeds the set duration T1But less than a set time period T2If the vehicle is judged to pass through normally, the vehicle will be reported to pass through and return to the no-vehicle state; if | Δ B' | exceeds the set magnetic field fluctuation strength threshold value Δ B1And the duration exceeds the set duration T2The vehicle is considered to be stopped, and the vehicle is judged to enter a parking state;
if the magnetic field fluctuation intensity is | delta B' | in the set time length T1Exceeds the set magnetic field fluctuation strength threshold value Delta B2But less than the threshold deltab1If the number of times of the channel is equal to or exceeds the set number of times N, judging that the adjacent channel large-scale vehicle passes through to cause false triggering;
wherein the threshold value Delta B2<ΔB1<ΔB0，ΔB1Is the classic value of the change of the magnetic field fluctuation intensity of a common small vehicle at the current moment and the previous moment in the normal passing process, delta B2The method is a classic value of the fluctuation intensity change of the magnetic field when a large vehicle on an adjacent road passes through the magnetic field to cause a false triggering state.
2. The vehicle pass-through of a geomagnetic sensing spike of claim 1The detection method is characterized in that: the method also comprises a step of calculating the passing speed and the passing length of the vehicle, specifically, the arrangement distance of two adjacent spikes in a group of spikes of the repeater is set to be L, and the current time t is recorded when the repeater judges that the vehicle approaches to the road in the driving direction and passes through the first geomagnetic sensing type spike of the group1And the vehicle passes through the duration T of a first geomagnetic sensing type spike and receives a vehicle passing detection signal of a second geomagnetic sensing type spike of the group in the road driving direction, and records the current time T when the vehicle is judged to be close to and pass2If the current vehicle speed is V = L/(t)2-t1) The current vehicle length S = T × V.
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| CN114387793A (en) * | 2022-03-04 | 2022-04-22 | 广州巨时信息科技股份有限公司 | Dual-mode hybrid vehicle detection method and device based on radar and geomagnetism |
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