CN111341116B - Geomagnetic parking space detection method - Google Patents
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- 238000000034 method Methods 0.000 claims abstract description 22
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- 230000005358 geomagnetic field Effects 0.000 claims abstract description 8
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- G—PHYSICS
- G08—SIGNALLING
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- 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
- G08G1/14—Traffic control systems for road vehicles indicating individual free spaces in parking areas
- G08G1/145—Traffic control systems for road vehicles indicating individual free spaces in parking areas where the indication depends on the parking areas
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Abstract
The invention discloses a geomagnetic parking space detection method, which comprises the following steps of: collecting geomagnetic field data of the current parking space through a geomagnetic detection node; smoothing the acquired geomagnetic field data by using mean filtering; the baseline value of the current environment is obtained by a double-baseline tracking method, and errors caused by single-baseline tracking can be eliminated while environmental magnetic field changes are tracked; and judging whether the vehicle exists or not by combining the algorithm of multi-state machine detection. The method avoids errors introduced during single-baseline tracking, and improves the accuracy of geomagnetic parking space detection through more accurate baseline values.
Description
Technical Field
The invention belongs to the field of automatic detection, and relates to a geomagnetic parking space detection method.
Background
Since twenty-first century, the quantity of motor vehicles in China continuously shows a rapid growth state, and the quantity of parking spaces is far from keeping pace with the increment of automobiles. Because the number of parking spaces is seriously insufficient, the problems of occupying the parking spaces, occupying public lanes and the like are caused, and serious pressure is brought to urban traffic, so that the establishment of a perfect parking system is particularly important at present. Wherein, the detection node is the key of the parking system. There are many vehicle detectors in the past, such as ultrasonic wave, microwave, infrared ray, video, etc., but because these detectors have the difficult problem of installation and later maintenance, with high costs, easily receive environmental impact scheduling problem, can't generally be applicable to the outdoor parking area that distributes scattered and receive the environmental constraint.
Compared with the scheme, the geomagnetic detection parking place has the most development potential. The cost is low, the installation and maintenance are easy, the power consumption is low, and the long-term work can be realized. The more mainstream detection method is a self-adaptive baseline parking space detection algorithm, a baseline tracks the environmental magnetic field quantity, and the existence of the vehicle is determined by comparing the detected variable quantity with a set threshold value.
However, long-term observation shows that sometimes the vehicle is driven out after being parked for a long time, and the parking space state is not changed, which directly causes the system to generate false alarm, influences the parking space utilization rate and brings inconvenience to the driver.
Disclosure of Invention
In order to solve the problems, the technical scheme of the invention is a geomagnetic parking space detection method, which comprises the following steps of:
s10, placing a geomagnetic detection node at the center of the parking space, and acquiring the current geomagnetic field value to obtain three-axis data x (t), y (t), z (t) of the detection node;
s20, smoothing the acquired data on the x axis of the geomagnetic field by using mean value filtering to remove data burrs;
s30, obtaining a baseline value X of the first current parking space magnetic field by using a baseline tracking method according to the obtained filtering valuebase(t) to adapt to a changing ambient magnetic field;
s40, obtaining a baseline value X delayed by three seconds according to the obtained baseline valuebase(t-3) as XdbaseTracking, as a second baseline, changes in the ambient magnetic field;
s50, repeating S20-S40 to obtain two base lines Y in the Y-axis directionbase，YdbaseAnd two base lines Z in the Z-axis directionbase，Zdbase；
And S60, judging whether the vehicle exists or not according to the multi-state machine detection method.
Preferably, the mean filtering in S20 is obtained by equation (1):
wherein, Xs(t) is the mean filtered signal, x (t) is the magnetic field value collected by the node, and N is the window length of the mean filtering.
Preferably, in S30, the baseline value of the baseline tracking is obtained by equation (2):
wherein, Xbase(t) is a baseline value of the earth magnetic field in the x-axis direction of the sensor node, and α is a weighting coefficient.
Preferably, in S60, the multi-state machine detection method includes six states:
s1 is in an empty state, the baseline value is updated, the total variation M of the magnetic field of the current parking space is calculated and obtained by the formula (3), and when the total variation M of the magnetic field is larger than the set threshold THR1, the operation goes to S2;
s2 is the first vehicle transition state, the baseline is completely stopped updating, and the total magnetic field variation is calculated by equation (4);
meanwhile, the counter cnTS2 starts counting, and if the count value of the cnTS2 exceeds the preset value Nav1, the state of S5 is entered;
if M < THR1 appears, go to S3;
s3 is the second vehicle-in transition state, the counter cntS3 starts counting, if M is larger than or equal to THR1, the state returns to S2;
if the count value of the cntS3 exceeds the preset value Nav2, returning to the S1 state;
s5 shows that the vehicle is in a state, when the total magnetic field variation M is smaller than the set threshold THR2, the process goes to S6;
s6 is the first non-vehicle transition state, the counter cntS6 starts counting, if M is larger than or equal to THR2, the state is entered into S4;
if the count value of the cntS3 exceeds the preset value Ndp1, the state returns to the S1 state;
s4 is the second no-vehicle transition state, the counter cntS4 starts counting, if M < THR2 appears, the state returns to S6;
if the count value of cntS4 exceeds the preset value Ndp2, the state of S5 is entered.
Preferably, the geomagnetic detection node in S10 adopts a sensor HMC5883L, and the acquisition frequency is 5 Hz.
Preferably, the window length N of the mean filtering in S20 is 20.
Preferably, the weighting coefficient α in S30 is 0.95.
Preferably, the set thresholds THR1, THR2, Nav1, Nva2, Ndp1 and Ndp2 in S60 are respectively 3 μ T, 4, 4, 4 and 4.
The invention has the following beneficial effects: the parking space magnetic field is tracked by using the double baselines, so that the baseline error introduced in the driving process of the vehicle is reduced, the misjudgment of the parking space when the vehicle drives out is caused, meanwhile, the multi-state machine detection algorithm is combined, the accuracy of geomagnetic parking space detection is effectively improved, the utilization rate of limited parking spaces is enhanced, convenience is provided for travelers, and meanwhile, the cost is also saved.
Drawings
Fig. 1 is a flowchart illustrating steps of a geomagnetic parking space detection method according to an embodiment of the present invention;
fig. 2 is a detection state diagram of S60 multi-state machine of the geomagnetic parking space detection method according to an embodiment of the method of the present invention;
fig. 3 is a comparison graph of x-axis data and a baseline in the process of exiting after parking once according to the method for detecting a geomagnetic parking space in an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
On the contrary, the invention is intended to cover alternatives, modifications, equivalents and alternatives which may be included within the spirit and scope of the invention as defined by the appended claims. Furthermore, in the following detailed description of the present invention, certain specific details are set forth in order to provide a better understanding of the present invention. It will be apparent to one skilled in the art that the present invention may be practiced without these specific details.
Referring to fig. 1, a flowchart of steps of a geomagnetic parking space detection method according to an embodiment of the present invention includes the following steps:
s10, placing a geomagnetic detection node at the center of the parking space, and acquiring the current geomagnetic field value to obtain three-axis data x (t), y (t), z (t) of the detection node;
s20, smoothing the acquired data on the x axis of the geomagnetic field by using mean value filtering to remove data burrs;
s30, obtaining the first current parking space magnet by using a baseline tracking method according to the obtained filtering valueBase line value X of the fieldbase(t) to adapt to a changing ambient magnetic field;
s40, obtaining a baseline value X delayed by three seconds according to the obtained baseline valuebase(t-3) as XdbaseTracking, as a second baseline, changes in the ambient magnetic field;
s50, repeating S20-S40 to obtain two base lines Y in the Y-axis directionbase，YdbaseAnd two base lines Z in the Z-axis directionbase，Zdbase；
And S60, judging whether the vehicle exists or not according to the multi-state machine detection method.
The average filtering in S20 is obtained by equation (1):
wherein, Xs(t) is the mean filtered signal, x (t) is the magnetic field value collected by the node, and N is the window length of the mean filtering.
In S30, the baseline value of the baseline tracking is obtained by equation (2):
wherein, Xbase(t) is a baseline value of the earth magnetic field in the x-axis direction of the sensor node, and α is a weighting coefficient.
Referring to fig. 2, in S60, the multi-state machine detection method includes six states:
s1 is in an empty state, the baseline value is updated, the total variation M of the magnetic field of the current parking space is calculated and obtained by the formula (3), and when the total variation M of the magnetic field is larger than the set threshold THR1, the operation goes to S2;
s2 is the first vehicle transition state, the baseline is completely stopped updating, and the total magnetic field variation is calculated by equation (4);
meanwhile, the counter cnTS2 starts counting, and if the count value of the cnTS2 exceeds the preset value Nav1, the state of S5 is entered;
if M < THR1 appears, go to S3;
s3 is the second vehicle-in transition state, the counter cntS3 starts counting, if M is larger than or equal to THR1, the state returns to S2;
if the count value of the cntS3 exceeds the preset value Nav2, returning to the S1 state;
s5 shows that the vehicle is in a state, when the total magnetic field variation M is smaller than the set threshold THR2, the process goes to S6;
s6 is the first non-vehicle transition state, the counter cntS6 starts counting, if M is larger than or equal to THR2, the state is entered into S4;
if the count value of the cntS3 exceeds the preset value Ndp1, the state returns to the S1 state;
s4 is the second no-vehicle transition state, the counter cntS4 starts counting, if M < THR2 appears, the state returns to S6;
if the count value of cntS4 exceeds the preset value Ndp2, the state of S5 is entered.
In a specific embodiment, the geomagnetic detection node in S10 adopts a sensor HMC5883L, and the acquisition frequency is 5 Hz.
The window length N of the mean filtering in S20 is 20.
The weighting coefficient α in S30 is 0.95.
The preset values THR1, THR2, Nav1, Nva2, Ndp1 and Ndp2 in S60 are respectively 3 mu T, 4, 4, 4 and 4.
Fig. 3 is a comparison graph of x-axis data and a baseline in the process of exiting after parking once, which shows that when a vehicle is about to enter a parking space, the magnetic field value changes, and a certain error is introduced due to the change in the conventional single baseline tracking method.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (8)
1. A geomagnetic parking space detection method is characterized by comprising the following steps:
s10, placing a geomagnetic detection node at the center of the parking space, and acquiring the current geomagnetic field value to obtain three-axis data x (t), y (t), z (t) of the detection node;
s20, smoothing the acquired data on the x axis of the geomagnetic field by using mean value filtering to remove data burrs;
s30, obtaining a baseline value X of the first current parking space magnetic field by using a baseline tracking method according to the obtained filtering valuebase(t) to adapt to a changing ambient magnetic field;
s40, obtaining a baseline value X delayed by three seconds according to the obtained baseline valuebase(t-3) as XdbaseTracking, as a second baseline, changes in the ambient magnetic field;
s50, repeating S20-S40 to obtain two base lines Y in the Y-axis directionbase，YdbaseAnd two base lines Z in the Z-axis directionbase，Zdbase；
S60, judging whether the vehicle exists or not according to the multi-state machine detection method;
in S60, the multi-state machine detection method includes six states:
s1 is in an empty state, the baseline value is updated, the total variation M of the magnetic field of the current parking space is calculated and obtained by the formula (3), and when the total variation M of the magnetic field is larger than the set threshold THR1, the operation goes to S2;
s2 is the first vehicle transition state, the baseline is completely stopped updating, and the total magnetic field variation is calculated by equation (4);
meanwhile, the counter cnTS2 starts counting, and if the count value of the cnTS2 exceeds the preset value Nav1, the state of S5 is entered;
if M < THR1 appears, go to S3;
s3 is the second vehicle-in transition state, the counter cntS3 starts counting, if M is larger than or equal to THR1, the state returns to S2;
if the count value of the cntS3 exceeds the preset value Nav2, returning to the S1 state;
s5 shows that the vehicle is in a state, when the total magnetic field variation M is smaller than the set threshold THR2, the process goes to S6;
s6 is the first non-vehicle transition state, the counter cntS6 starts counting, if M is larger than or equal to THR2, the state is entered into S4;
if the count value of the cntS3 exceeds the preset value Ndp1, the state returns to the S1 state;
s4 is the second no-vehicle transition state, the counter cntS4 starts counting, if M < THR2 appears, the state returns to S6;
if the count value of cntS4 exceeds the preset value Ndp2, the state of S5 is entered.
2. The method of claim 1, wherein the mean filtering in S20 is obtained by equation (1):
wherein, Xs(t) is the mean filtered signal, x (t) is the magnetic field value collected by the node, and N is the window length of the mean filtering.
3. The method according to claim 1, wherein in the S30, the baseline value of the baseline tracking is obtained by equation (2):
wherein, Xbase(t) is a baseline value of the earth magnetic field in the x-axis direction of the sensor node, and α is a weighting coefficient.
4. The method according to claim 1, wherein in S60, the multi-state machine detection method comprises six states:
s1 is in an empty state, the baseline value is updated, the total variation M of the magnetic field of the current parking space is calculated and obtained by the formula (3), and when the total variation M of the magnetic field is larger than the set threshold THR1, the operation goes to S2;
s2 is the first vehicle transition state, the baseline is completely stopped updating, and the total magnetic field variation is calculated by equation (4);
meanwhile, the counter cnTS2 starts counting, and if the count value of the cnTS2 exceeds the preset value Nav1, the state of S5 is entered;
if M < THR1 appears, go to S3;
s3 is the second vehicle-in transition state, the counter cntS3 starts counting, if M is larger than or equal to THR1, the state returns to S2;
if the count value of the cntS3 exceeds the preset value Nav2, returning to the S1 state;
s5 shows that the vehicle is in a state, when the total magnetic field variation M is smaller than the set threshold THR2, the process goes to S6;
s6 is the first non-vehicle transition state, the counter cntS6 starts counting, if M is larger than or equal to THR2, the state is entered into S4;
if the count value of the cntS3 exceeds the preset value Ndp1, the state returns to the S1 state;
s4 is the second no-vehicle transition state, the counter cntS4 starts counting, if M < THR2 appears, the state returns to S6;
if the count value of cntS4 exceeds the preset value Ndp2, the state of S5 is entered.
5. The method as claimed in claim 1, wherein the geomagnetic detection node in S10 employs a sensor HMC5883L, and the acquisition frequency is 5 Hz.
6. The method according to claim 2, wherein the window length N of the mean filtering in S20 is 20.
7. The method according to claim 3, wherein the weighting factor α in S30 is 0.95.
8. The method as claimed in claim 4, wherein the set threshold values THR1, THR2, Nav1, Nva2, Ndp1 and Ndp2 in S60 are 3 μ T, 3 μ T, 4, 4, 4 and 4 respectively.
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| CN113689711B (en) * | 2021-08-31 | 2023-06-02 | 武汉拓宝科技股份有限公司 | Geomagnetic parking detection method and geomagnetic parking detection system |
| CN113971887A (en) * | 2021-10-29 | 2022-01-25 | 深圳市顺易通信息科技有限公司 | Processing method and processing device for judging whether vehicles enter or exit parking lot |
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| CN107945570B (en) * | 2017-12-18 | 2020-05-26 | 浙江工业大学 | Geomagnetic parking space detection optimization method |
| DE102017223696A1 (en) * | 2017-12-22 | 2019-06-27 | Robert Bosch Gmbh | Method for calibrating a device for determining an occupancy state of a parking space of a parking space |
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