A traffic portal vehicle flow detection system

Abstract

The application discloses a traffic port vehicle flow detection system, which comprises a vehicle detection unit arranged on a lane where the traffic port is located, a roadside unit for estimating vehicle flow according to the vehicle detection unit, and a vehicle flow monitoring unit connected with the roadside unit. The vehicle detection unit comprises a first geomagnetic sensor and a second geomagnetic sensor arranged on the lane, the second geomagnetic sensor is arranged behind the first geomagnetic sensor in the lane direction, and the distance between the two geomagnetic sensors is not greater than the vehicle length. The first geomagnetic sensor and the second geomagnetic sensor are both connected with the roadside unit, the roadside unit judges whether a vehicle is merged into the traffic port according to the geomagnetic signals received by the first geomagnetic sensor and the second geomagnetic sensor, and adjusts the detection result of the vehicle according to the distance between the vehicles on the lane at this time. The application can avoid the vehicle detection error caused by the deviation of the threshold signal due to the environmental interference, and improve the vehicle flow detection accuracy.

Description

Technical Field

[0001] This invention belongs to the field of traffic flow monitoring technology, specifically relating to a traffic flow detection system at a traffic intersection. Background Technology

[0002] With the booming development of transportation, achieving sound and precise traffic management and accurate vehicle dispatching has become a crucial aspect of urban planning and management. Traffic flow reflects people's travel needs, and accurately and efficiently predicting traffic flow in different areas is fundamental to achieving urban orderliness. It is essential for improving travel efficiency, alleviating urban congestion, and promoting the coordinated development of smart transportation and smart cities. At key traffic checkpoints such as large bridges and tunnel entrances, effective traffic management in these areas is of paramount importance.

[0003] Induction coils were the most widely used in the early stages, but their widespread adoption was limited due to the need for road construction, inconvenient installation, high failure rate, and short product lifespan. Current technologies generally employ video image-based traffic flow detection, but this static-to-dynamic approach requires extensive deployment of monitoring equipment, resulting in high costs. Furthermore, it is susceptible to natural factors such as wind, lighting, people, rain, and snow, leading to significant errors and poor reliability. Geomagnetic sensors utilize the disturbance of the Earth's magnetic field by vehicles to determine vehicle arrival and passage, enabling vehicle information analysis, control, and management. They offer advantages such as low power consumption, easy installation, low cost, high detection accuracy, stable performance, and no road surface damage, leading to their gradual adoption in the transportation sector. Current technologies generally rely on threshold comparisons to detect magnetic disturbance signals when vehicles pass, but changes in the geomagnetic environment (such as climate or road conditions) alter the threshold, affecting detection accuracy and causing missed or duplicate detections. In addition, the geomagnetic sensor can also be affected by changes in the magnetic field caused by the passing of non-motorized vehicles or the falling of ferromagnetic materials, which can interfere with the vehicle detection results. At the same time, the surrounding environment, such as the obstruction of branches and leaves, and the signal absorption of roadside steel structures, may cause a significant attenuation of the wirelessly received geomagnetic signal. When cars in the city are too close together, that is, when following too closely, these factors may affect the detected geomagnetic interference signal and seriously affect the traffic flow detection results. Summary of the Invention

[0004] To address the above problems, this invention proposes a traffic flow detection system for traffic intersections. The technical solution adopted by this invention to solve the above technical problems is as follows:

[0005] A traffic flow detection system for an intersection includes a vehicle detection unit installed on the lane where the intersection is located, a roadside unit that estimates traffic flow based on the vehicle detection unit, and a traffic flow monitoring unit connected to the roadside unit. The vehicle detection unit includes a first geomagnetic sensor and a second geomagnetic sensor installed on the driving lane. The second geomagnetic sensor is located behind the first geomagnetic sensor in the driving lane direction, and the distance between the two geomagnetic sensors is no greater than the vehicle length specified by the lane. Both the first and second geomagnetic sensors are connected to the roadside unit. The roadside unit determines whether a vehicle is merging into the intersection based on the geomagnetic signals received by the first and second geomagnetic sensors, and adjusts the vehicle detection results according to the distance between vehicles in the lane at that time.

[0006] The roadside unit includes a wireless signal receiver for receiving geomagnetic signals output by a first geomagnetic sensor and a second geomagnetic sensor. The output of the wireless signal receiver is electrically connected to the inputs of a first interference suppressor and a second interference suppressor. The outputs of both the first and second interference suppressors are electrically connected to the input of a vehicle predictor. The output of the vehicle predictor is connected to a vehicle counter via an analog-to-digital converter and is also connected to the output of a flow calibrator. The flow calibrator uses a distance sensor to detect the distance between the current vehicle and the vehicle behind it, and adjusts the vehicle predictor based on the distance.

[0007] The first interference suppressor includes a resistor R1. One end of resistor R1 is connected to one end of capacitor C1 and the output terminal of the wireless signal receiver. The other end of resistor R1 is connected to one end of capacitor C2, one end of resistor R2, one end of resistor R3, one end of resistor R6, and one end of field-effect transistor T1. The drain of field-effect transistor T1 is connected to one end of resistor R4. The source of field-effect transistor T1 is connected to the drain of field-effect transistor T3, the gate of field-effect transistor T3, and the gate of field-effect transistor T4. The drain of field-effect transistor T4 is connected to one end of capacitor C3 and the source of field-effect transistor T2. The gate of field-effect transistor T2 is connected to the other end of resistor R6. The drain of field-effect transistor T2 is connected to one end of resistor R5 and the anode of diode D1. The cathode of diode D1 is connected to one end of resistor R7, one end of resistor R12, one end of inductor L1, and one end of capacitor C6. The other end of resistor R7 is connected to one end of capacitor C4 and the output terminal of the wireless signal receiver. One end of capacitor C5 is connected to one end of resistor R9. The other end of capacitor C5 is connected to one end of resistor R8 and the non-inverting input of operational amplifier AR1. The inverting input of operational amplifier AR1 is connected to one end of resistor R10 and one end of resistor R11. The other end of resistor R10 is connected to the other end of resistor R9, the other end of resistor R12, the output of operational amplifier AR1, and one end of normally closed switch K2-1. The other end of normally closed switch K2-1 is connected to the vehicle predictor, and the opening and closing of normally closed switch K2-1 is controlled by the flow calibrator. The other end of resistor R3, the source of field-effect transistor T3, the source of field-effect transistor T4, the other end of capacitor C3, the other end of capacitor C4, the other end of resistor R8, the other end of resistor R11, the other end of capacitor C6, and the other end of inductor L1 are all grounded. The other ends of resistor R2, resistor R4, and resistor R5 are all connected to the positive power supply VCC.

[0008] The vehicle predictor includes a resistor R21. One end of resistor R21 is connected to the output of a first interference suppressor, and the other end is connected to the non-inverting input of operational amplifier AR3. The inverting input of operational amplifier AR3 is connected to one end of resistor R23, one end of resistor R24, and one end of resistor R22. The other end of resistor R22 is connected to the output of a second interference suppressor. The output of operational amplifier AR3 is connected to the other end of resistor R23 and one end of resistor R25. The other end of resistor R25 is connected to the anode of diode D3, and the cathode of diode D3 is connected to the non-inverting input of operational amplifier AR4 and the inverting input of operational amplifier AR5. The non-inverting input of operational amplifier AR5 is connected to the inverting input of operational amplifier AR4, which is connected to one end of resistor R27, one end of resistor R26, and the anode of diode D4. The other end of resistor R26 is connected to the anode of diode D5, and the cathode of diode D5 is connected to the cathode of diode D4, one end of resistor R28, and the output of operational amplifier AR4. The other end of resistor R28 is connected to one end of resistor R29 and the inverting input of operational amplifier AR5. The output of operational amplifier AR5 is connected to the other end of resistor R29, one end of resistor R30, and the anode of thyristor Q10. The other end of resistor R30 is connected to the anode of thyristor Q10. The gate of 0 is connected to one end of capacitor C10 and one end of resistor R41. The cathode of thyristor Q10 is connected to the non-inverting input of operational amplifier AR6 and one end of transient suppression diode V1. The output of operational amplifier AR6 is connected to the other end of transient suppression diode V1, one end of resistor R31, and one end of transient suppression diode V2. The other end of resistor R31 is connected to one input of OR gate U1. The other input of OR gate U1 is connected to the output of the flow calibrator. The output of OR gate U1 is connected to one end of resistor R54, one end of resistor R55, one end of resistor R56, and one end of normally open switch K1-1. The base of transistor Q1 is connected; the other end of the normally open switch K1-1 is connected to the input terminal of the analog-to-digital converter. The emitter of transistor Q1, the other end of resistor R24, the other end of resistor R27, the other end of capacitor C10, the other end of resistor R41, the inverting input terminal of operational amplifier AR6, the other end of transient suppression diode V2, and the other end of resistor R56 are all grounded. The collector of transistor Q1 is connected to one end of relay K1, and the other end of relay K1 is connected to the positive power supply VCC. Relay K1 controls the opening and closing of normally open switch K1-1 and normally open switch K1-2 of the flow calibrator.

[0009] The flow calibrator includes a resistor R52. One end of resistor R52 is used to receive the distance between the following vehicle and the current vehicle sent by a distance sensor. The distance sensor is located behind the second geomagnetic sensor. The other end of resistor R52 is connected to the inverting input of operational amplifier AR10 and one end of capacitor C11. The other end of capacitor C11 is connected to the output of operational amplifier AR10, one end of resistor R57, the base of transistor Q2, and one end of normally open switch K1-2. The non-inverting input of operational amplifier AR10 is connected to... The lower end of the sliding rheostat X1 is connected to one end of the resistor R51. The collector of the transistor Q2 is connected to one end of the relay K2, and the other end of the relay K2 is connected to the positive power supply VCC. The other end of the normally open switch K1-2 is connected to one end of the resistor R53. The other end of the resistor R53 is connected to one end of the capacitor C12 and the other input terminal of the OR gate U1 of the vehicle predictor. The normally open switch K1-2 is controlled by the relay K2. The other end of the resistor R51, the emitter of the transistor Q2, and the other end of the capacitor C12 are all grounded.

[0010] The beneficial effects of this invention are:

[0011] 1. The first and second interference suppressors process the two received geomagnetic signals respectively. The differential amplifier circuit amplifies the geomagnetic signal differentially. The current source is used to improve the amplification capability of the differential circuit. Diode D1 removes small noise interference signals for the first time. The bandpass amplifier with operational amplifier AR1 as the main component performs secondary filtering on the geomagnetic signal and amplifies the signal simultaneously. The feedback circuit composed of resistor R21, inductor L1 and capacitor C1 feeds back the signal output by operational amplifier AR1. While compensating for the received signal, it further improves the signal purity.

[0012] 2. Two geomagnetic sensors are set up one after the other on the lane to detect passing vehicles. The two sensors are in the same environment, so the environmental interference is the same. The difference between the geomagnetic signals detected by the two geomagnetic sensors after processing is used to detect whether a vehicle has passed, avoiding the detection error caused by the shift of the threshold signal due to environmental interference.

[0013] 3. The distance sensor detects vehicles behind and corrects the traffic flow when following closely, avoiding missed detections caused by following too closely and improving the accuracy of vehicle detection. The system is easy to install, low in cost, does not damage the road surface, and can better detect traffic flow. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a schematic diagram of the structure of the present invention.

[0016] Figure 2 This is a schematic diagram of the circuit structure of an interference suppressor.

[0017] Figure 3 This is a schematic diagram of the circuit structure of the vehicle predictor and flow calibrator. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] A traffic flow detection and prediction device for traffic intersections, such as Figure 1As shown, the system includes a vehicle detection unit installed in the lane where the traffic intersection is located, a roadside unit that predicts traffic flow based on the vehicle detection unit, and a traffic flow monitoring unit connected to the roadside unit. The traffic flow monitoring unit can be located in a traffic monitoring center. The vehicle detection unit includes a first geomagnetic sensor and a second geomagnetic sensor installed in the driving lane. The second geomagnetic sensor is located behind the first geomagnetic sensor in the driving lane direction, and the distance between the two geomagnetic sensors is no greater than the vehicle length. Both the first and second geomagnetic sensors are connected to the roadside unit. The roadside unit determines whether a vehicle is merging into the traffic intersection based on the difference in geomagnetic signals received by the first and second geomagnetic sensors, and adjusts the vehicle detection results based on the distance between vehicles in the lane at this time. In this embodiment, the lane where the traffic intersection is located is set as a one-way lane. If it is a two-way lane, a corresponding prediction device can be set separately to count the traffic flow in the two lanes. The distance between the two geomagnetic sensors can be set to any value between 2 meters and 4 meters. The specific value can be set according to the current lane's regulations for vehicles. This application sets the distance to 2 meters based on the length of a two-box axle vehicle, as large vehicles are generally not allowed to pass through in urban areas. The geomagnetic sensor detects whether a vehicle is passing by by disturbing the geomagnetic field. This application uses two geomagnetic sensors to detect the disturbance signal synchronously and detect the vehicle based on the difference between the two signals. This avoids threshold drift caused by external factors such as environment and climate, which can lead to inaccurate detection. Because the two geomagnetic sensors are affected by the same external factors, the interference and drift caused by these factors are consistent, which improves the detection accuracy. The roadside unit also adjusts the traffic flow detection results based on the distance between the current vehicle and the vehicle behind it, avoiding missed detections caused by vehicles being too close together.

[0020] The roadside unit includes a wireless signal receiver for receiving geomagnetic signals output by a first geomagnetic sensor and a second geomagnetic sensor. The output of the wireless signal receiver is electrically connected to the inputs of a first interference suppressor and a second interference suppressor. The outputs of both the first and second interference suppressors are electrically connected to the input of a vehicle predictor. The output of the vehicle predictor is connected to a vehicle counter via an analog-to-digital converter. The vehicle counter counts the number of traffic flows based on the number of high-level signals received by the analog-to-digital converter. The total number obtained by the vehicle counter is transmitted to the traffic flow monitoring unit via a wireless transmission unit. The output of the vehicle predictor is also connected to the output of a traffic flow calibrator. The traffic flow calibrator uses a distance sensor to detect the distance between the current vehicle and the vehicle behind it, and adjusts the number of traffic flows detected by the vehicle predictor based on the distance. The geomagnetic signal on the road is generally composed of three superimposed parts: the background signal of the Earth's magnetic field, the interfering magnetic field signal, and the disturbance signal of the magnetic field when the vehicle passes. The interference suppressor filters, amplifies, and compensates the received geomagnetic signal, filters out the interference of high-frequency noise signals, and solves the problem of signal attenuation caused by obstacles. It ensures the integrity and authenticity of the original signal, eliminates the influence of environmental clutter on the detection results, improves the accuracy of the signal, and thus improves the accuracy of vehicle detection.

[0021] like Figure 2As shown, the first interference suppressor includes a resistor R1. One end of resistor R1 is connected to one end of capacitor C1 and the output terminal of the wireless signal receiver. The other end of resistor R1 is connected to one end of capacitor C2, one end of resistor R2, one end of resistor R3, one end of resistor R6, and one end of field-effect transistor T1. The drain of field-effect transistor T1 is connected to one end of resistor R4. The source of field-effect transistor T1 is connected to the drain of field-effect transistor T3, the gate of field-effect transistor T3, and the gate of field-effect transistor T4. The drain of field-effect transistor T4 is connected to one end of capacitor C3 and the source of field-effect transistor T2. The gate of field-effect transistor T2 is connected to the other end of resistor R6. The drain of field-effect transistor T2 is connected to one end of resistor R5 and the anode of diode D1. The cathode of diode D1 is connected to one end of resistor R7, one end of resistor R12, one end of inductor L1, and one end of capacitor C6. The other end of resistor R7 is connected to one end of capacitor C4. One end of capacitor C5 is connected to one end of resistor R9. The other end of capacitor C5 is connected to one end of resistor R8 and the non-inverting input of operational amplifier AR1. The inverting input of operational amplifier AR1 is connected to one end of resistor R10 and one end of resistor R11. The other end of resistor R10 is connected to the other end of resistor R9, the other end of resistor R12, the output of operational amplifier AR1, and one end of normally closed switch K2-1. The other end of normally closed switch K2-1 is connected to the vehicle predictor, and the opening and closing of normally closed switch K2-1 is controlled by the flow calibrator. The other end of resistor R3, the source of field-effect transistor T3, the source of field-effect transistor T4, the other end of capacitor C3, the other end of capacitor C4, the other end of resistor R8, the other end of resistor R11, the other end of capacitor C6, and the other end of inductor L1 are all grounded. The other ends of resistor R2, resistor R4, and resistor R5 are all connected to the positive power supply VCC.

[0022] Resistor R1, capacitor C1, and capacitor C2 form a matching circuit for receiving geomagnetic signals without distortion. Field-effect transistors T1 and T2 form a differential circuit to amplify the received geomagnetic signal. Resistors R2 and R3 are bias resistors. Field-effect transistors T3 and T4 form a current source connected to the sources of field-effect transistors T1 and T2, improving the amplification capability of the differential circuit. Diode D1 acts as a small-signal filter, filtering interference and glitches from the geomagnetic sensor. Resistors R7 and R11, capacitors C4 and C5, and operational amplifier AR1 form a bandpass filter to select the corresponding geomagnetic signal. The geomagnetic signal amplified by operational amplifier AR1 is then filtered a second time by resistor R21, inductor L1, and capacitor C6 before being fed back to one end of resistor R7 for compensation and extraction of the geomagnetic signal, further improving the anti-interference and clutter filtering capabilities of the geomagnetic signal and increasing detection accuracy. The circuit structure of the first and second interference suppressors is illustrated in this embodiment. Figure 1The only difference is that normally closed switch K2-1 is replaced with normally closed switch K2-2, and normally closed switch K2-2 is still controlled by the flow calibrator.

[0023] like Figure 3 As shown, the vehicle predictor includes a resistor R21. One end of resistor R21 is connected to the output of the first interference suppressor, and the other end of resistor R21 is connected to the non-inverting input of operational amplifier AR3. The inverting input of operational amplifier AR3 is connected to one end of resistor R23, one end of resistor R24, and one end of resistor R22. The other end of resistor R22 is connected to the output of the second interference suppressor. The output of operational amplifier AR3 is connected to the other end of resistor R23 and one end of resistor R25. The other end of resistor R25 is connected to the anode of diode D3, and the cathode of diode D3 is connected to the non-inverting input of operational amplifier AR4. The non-inverting input of operational amplifier AR5 is connected to the following terminals: the inverting input of operational amplifier AR4 is connected to one end of resistor R27, one end of resistor R26, and the anode of diode D4; the other end of resistor R26 is connected to the anode of diode D5; the cathode of diode D5 is connected to the cathode of diode D4, one end of resistor R28, and the output of operational amplifier AR4; the other end of resistor R28 is connected to one end of resistor R29 and the inverting input of operational amplifier AR5; the output of operational amplifier AR5 is connected to the other end of resistor R29, one end of resistor R30, and the anode of thyristor Q10; the other end of resistor R30 is connected to the thyristor... The gate of thyristor Q10, one end of capacitor C10, and one end of resistor R41 are connected. The cathode of thyristor Q10 is connected to the non-inverting input of operational amplifier AR6 and one end of transient suppression diode V1. The output of operational amplifier AR6 is connected to the other end of transient suppression diode V1, one end of resistor R31, and one end of transient suppression diode V2. The other end of resistor R31 is connected to one input of OR gate U1. The other input of OR gate U1 is connected to the output of the flow calibrator. The output of OR gate U1 is connected to one end of resistor R54, one end of resistor R55, one end of resistor R56, and one end of normally open switch K1-1. The base of transistor Q1 is connected; the other end of normally open switch K1-1 is connected to the input terminal of analog-to-digital converter. The emitter of transistor Q1, the other end of resistor R24, the other end of resistor R27, the other end of capacitor C10, the other end of resistor R41, the inverting input terminal of operational amplifier AR6, the other end of transient suppression diode V2, and the other end of resistor R56 are all grounded. The collector of transistor Q1 is connected to one end of relay K1, and the other end of relay K1 is connected to positive power supply VCC. Relay K1 controls the opening and closing of normally open switch K1-1 and normally open switch K1-2 of flow calibrator.

[0024] The geomagnetic signal processed by the first interference suppressor is sent to the non-inverting input of operational amplifier AR3 through resistor R21. The geomagnetic signal processed by the second interference suppressor is sent to the inverting input of operational amplifier AR3 through resistor R22. Operational amplifier AR3 calculates the difference between the two geomagnetic signals, and the result is sent to the non-inverting input of operational amplifier AR4 through resistor R25 and diode D3. Operational amplifier AR4, resistors R26-R29, diode D4, diode D5, and operational amplifier AR5 form an absolute value circuit to convert the difference into a positive signal. Resistor R30 and capacitor C10 form a delay circuit. The positive signal charges capacitor C10 through resistor R30. When the voltage on capacitor C10 reaches the gate voltage of thyristor Q10... When the voltage is limited, that is, when the peak signal obtained by the two geomagnetic sensors passes the vehicle, thyristor Q10 is turned on, and operational amplifier AR6 is a zero-crossing comparator. The positive signal is transmitted to the non-inverting input of operational amplifier AR6 through thyristor Q10, and operational amplifier AR6 outputs a high-level signal. This high-level signal is transmitted to the base of transistor Q1 through OR gate U1, relay K1 is energized, and normally open switches K1-1 and K1-2 are turned on. The high-level signal is transmitted to the input of analog-to-digital converter through normally open switch K1-1. The analog-to-digital converter converts the high-level signal into a digital signal. The vehicle counter counts the vehicles according to the received converted high-level signal, that is, at this time, one vehicle has passed. After normally open switch K1-2 is closed, the flow calibrator is started.

[0025] The flow calibrator includes a resistor R52. One end of resistor R52 is used to receive the distance between the following vehicle and the current vehicle sent by a distance sensor. The distance sensor is located behind the second geomagnetic sensor. The other end of resistor R52 is connected to the inverting input of operational amplifier AR10 and one end of capacitor C11. The other end of capacitor C11 is connected to the output of operational amplifier AR10, one end of resistor R57, the base of transistor Q2, and one end of normally open switch K1-2. The non-inverting input of operational amplifier AR10 is connected to... The lower end of the sliding rheostat X1 is connected to one end of the resistor R51. The collector of the transistor Q2 is connected to one end of the relay K2, and the other end of the relay K2 is connected to the positive power supply VCC. The other end of the normally open switch K1-2 is connected to one end of the resistor R53. The other end of the resistor R53 is connected to one end of the capacitor C12 and the other input terminal of the OR gate U1 of the vehicle predictor. The normally open switch K1-2 is controlled by the relay K2. The other end of the resistor R51, the emitter of the transistor Q2, and the other end of the capacitor C12 are all grounded.

[0026] When the flow calibrator is activated, it begins detecting vehicles behind the current vehicle. If the distance between two vehicles is less than a preset distance threshold, transistor Q2 conducts, relay K2 is energized, and normally closed switch K2-1 opens. The interference suppressor cannot transmit the geomagnetic signal to the vehicle predictor, thus preventing further measurement of the geomagnetic signal of closely following vehicles. Adjusting the resistance of the sliding rheostat X1 changes the preset distance threshold. This preset distance threshold is obtained based on experiments on the interference of vehicle types on the geomagnetic field in the lane. In this embodiment, the preset distance threshold is not less than the distance between the two geomagnetic sensors. After the following vehicle passes, transistor Q2 deconducts, relay K2 is de-energized, and normally closed switch K2-1 closes, allowing detection of the next following vehicle to begin. Resistor R53 and capacitor C12 form a delay circuit, but this delay time is set less than the energizing time of relay K2. That is, after the high-level signal sent by operational amplifier AR6 is transmitted to the analog-to-digital converter, transistor Q2 turns on. When the distance between the current vehicle and the vehicle behind is less than a preset distance threshold, operational amplifier AR10 outputs a high level. At this time, this high-level signal, after being delayed by resistor R53 and capacitor C12, is also sent to the analog-to-digital converter to count the vehicles immediately following the current vehicle. Afterwards, the following vehicles are turned off by transistor Q2. Capacitor C11 stabilizes the circuit and prevents self-oscillation.

[0027] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A traffic flow detection system at an intersection, comprising a vehicle detection unit installed on the lane where the intersection is located, a roadside unit for predicting traffic flow based on the vehicle detection unit, and a traffic flow monitoring unit connected to the roadside unit, characterized in that, The vehicle detection unit includes a first geomagnetic sensor and a second geomagnetic sensor installed on the driving lane. The second geomagnetic sensor is located behind the first geomagnetic sensor in the driving lane direction, and the distance between the two geomagnetic sensors is no greater than the vehicle length specified by the lane. Both the first and second geomagnetic sensors are connected to a roadside unit. The roadside unit determines whether a vehicle is merging into the traffic intersection based on the geomagnetic signals received by the first and second geomagnetic sensors, and adjusts the vehicle detection results according to the distance between vehicles in the lane at this time. The roadside unit includes a wireless signal receiver for receiving geomagnetic signals output by a first geomagnetic sensor and a second geomagnetic sensor. The output of the wireless signal receiver is electrically connected to the inputs of a first interference suppressor and a second interference suppressor. The outputs of both the first and second interference suppressors are electrically connected to the input of a vehicle prediction device. The output of the vehicle prediction device is connected to a vehicle counter via an analog-to-digital converter and is also connected to the output of a flow calibrator. The flow calibrator uses a distance sensor to detect the distance between the current vehicle and the vehicle behind it, and adjusts the vehicle prediction device accordingly. The vehicle predictor includes a resistor R21. One end of resistor R21 is connected to the output of a first interference suppressor, and the other end is connected to the non-inverting input of operational amplifier AR3. The inverting input of operational amplifier AR3 is connected to one end of resistor R23, one end of resistor R24, and one end of resistor R22. The other end of resistor R22 is connected to the output of a second interference suppressor. The output of operational amplifier AR3 is connected to the other end of resistor R23 and one end of resistor R25. The other end of resistor R25 is connected to the anode of diode D3, and the cathode of diode D3 is connected to the non-inverting input of operational amplifier AR4 and the inverting input of operational amplifier AR5. The non-inverting input of operational amplifier AR5 is connected to the inverting input of operational amplifier AR4, which is connected to one end of resistor R27, one end of resistor R26, and the anode of diode D4. The other end of resistor R26 is connected to the anode of diode D5, and the cathode of diode D5 is connected to the cathode of diode D4, one end of resistor R28, and the output of operational amplifier AR4. The other end of resistor R28 is connected to one end of resistor R29 and the inverting input of operational amplifier AR5. The output of operational amplifier AR5 is connected to the other end of resistor R29, one end of resistor R30, and the anode of thyristor Q10. The other end of resistor R30 is connected to the anode of thyristor Q10. The gate of 0 is connected to one end of capacitor C10 and one end of resistor R41. The cathode of thyristor Q10 is connected to the non-inverting input of operational amplifier AR6 and one end of transient suppression diode V1. The output of operational amplifier AR6 is connected to the other end of transient suppression diode V1, one end of resistor R31, and one end of transient suppression diode V2. The other end of resistor R31 is connected to one input of OR gate U1. The other input of OR gate U1 is connected to the output of the flow calibrator. The output of OR gate U1 is connected to one end of resistor R54, one end of resistor R55, one end of resistor R56, and one end of normally open switch K1-1. The base of transistor Q1 is connected; the other end of the normally open switch K1-1 is connected to the input terminal of the analog-to-digital converter. The emitter of transistor Q1, the other end of resistor R24, the other end of resistor R27, the other end of capacitor C10, the other end of resistor R41, the inverting input terminal of operational amplifier AR6, the other end of transient suppression diode V2, and the other end of resistor R56 are all grounded. The collector of transistor Q1 is connected to one end of relay K1, and the other end of relay K1 is connected to the positive power supply VCC. Relay K1 controls the opening and closing of normally open switch K1-1 and normally open switch K1-2 of the flow calibrator. The flow calibrator includes a resistor R52. One end of resistor R52 is used to receive the distance between the following vehicle and the current vehicle sent by a distance sensor. The distance sensor is located behind the second geomagnetic sensor. The other end of resistor R52 is connected to the inverting input of operational amplifier AR10 and one end of capacitor C11. The other end of capacitor C11 is connected to the output of operational amplifier AR10, one end of resistor R57, the base of transistor Q2, and one end of normally open switch K1-2. The non-inverting input of operational amplifier AR10 is connected to... The lower end of the sliding rheostat X1 is connected to one end of the resistor R51. The collector of the transistor Q2 is connected to one end of the relay K2, and the other end of the relay K2 is connected to the positive power supply VCC. The other end of the normally open switch K1-2 is connected to one end of the resistor R53. The other end of the resistor R53 is connected to one end of the capacitor C12 and the other input terminal of the OR gate U1 of the vehicle predictor. The normally open switch K1-2 is controlled by the relay K2. The other end of the resistor R51, the emitter of the transistor Q2, and the other end of the capacitor C12 are all grounded.

2. The traffic flow detection and prediction system at an intersection according to claim 1, characterized in that, The first interference suppressor includes a resistor R1. One end of resistor R1 is connected to one end of capacitor C1 and the output terminal of the wireless signal receiver. The other end of resistor R1 is connected to one end of capacitor C2, one end of resistor R2, one end of resistor R3, one end of resistor R6, and one end of field-effect transistor T1. The drain of field-effect transistor T1 is connected to one end of resistor R4. The source of field-effect transistor T1 is connected to the drain of field-effect transistor T3, the gate of field-effect transistor T3, and the gate of field-effect transistor T4. The drain of field-effect transistor T4 is connected to one end of capacitor C3 and the source of field-effect transistor T2. The gate of field-effect transistor T2 is connected to the other end of resistor R6. The drain of field-effect transistor T2 is connected to one end of resistor R5 and the anode of diode D1. The negative terminal of diode D1 is connected to one end of resistor R7, one end of resistor R12, one end of inductor L1, and one end of capacitor C6. The other end of resistor R7 is connected to one end of capacitor C4, one end of capacitor C5, and one end of resistor R9. The other end of capacitor C5 is connected to one end of resistor R8 and the non-inverting input terminal of operational amplifier AR1. The inverting input terminal of operational amplifier AR1 is connected to one end of resistor R10 and one end of resistor R11. The other end of resistor R10 is connected to the other end of resistor R9, the other end of resistor R12, the output terminal of operational amplifier AR1, and one end of normally closed switch K2-1. The other end of normally closed switch K2-1 is connected to the vehicle predictor, and the opening and closing of normally closed switch K2-1 is controlled by the flow calibrator. The other end of resistor R3, the source of field-effect transistor T3, the source of field-effect transistor T4, the other end of capacitor C3, the other end of capacitor C4, the other end of resistor R8, the other end of resistor R11, the other end of capacitor C6, and the other end of inductor L1 are all grounded. The other ends of resistor R2, resistor R4, and resistor R5 are all connected to the positive power supply VCC.

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