Wheel sensor and axle counting system

Abstract

The present application relates to the technical field of rail transit, and in particular to a wheel sensor and an axle counting system. The wheel sensor is used for detecting the rim of a train wheel and converting a detected signal from an analog signal to a digital signal, and the wheel sensor is laid on a rail; a junction box is arranged near each wheel sensor, junction boxes are in one-to-one correspondence with wheel sensors, and each junction box is connected to the adjacent junction boxes in front of and behind same; and all the junction boxes along the railway are cascaded and then connected to an axle counter host. The wheel sensor comprises: a linear feedback circuit used for feeding back the oscillation amplitude of an oscillation circuit in the wheel sensor in real time, and an excitation frequency adjusting circuit used for adjusting the oscillation circuit on the basis of the oscillation amplitude of the oscillation circuit, so as to adaptively control the oscillation amplitude of the oscillation circuit. The stable operation of the wheel sensor is ensured; cable laying costs can be reduced, the cable can transmit a sufficiently large amount of data, is not easily susceptible to interference, and has high reliability; and manufacturing costs are lowered.

Description

A wheel sensor and axle counting system

[0001] Cross-reference to related applications:

[0002] This application claims priority to prior Chinese patent applications No. 202323168409.8; No. 202311730702.0; No. 202311572338.X; and No. 202311572337.5. The first patent application, filed on November 23, 2023, is entitled: A wheel sensor based on 2-out-of-3; the second patent application, filed on December 15, 2023, is entitled: A linear feedback circuit, a linear feedback method, and a wheel sensor; the third patent application, filed on November 23, 2023, is entitled: A wheel sensor axle counting system; and the fourth patent application, filed on November 23, 2023, is entitled: A wheel sensor with high reliability axle counting. The entire contents of these four Chinese patent applications are incorporated herein by reference. Technical Field

[0003] The present application belongs to the field of rail transportation technology, and in particular relates to a linear feedback circuit, method, wheel sensor, and axle counting system. Background Art

[0004] Wheel sensors are widely used in railways. They are installed on rails to detect train wheels. The wheel sensors sense the train wheels to generate axle counting signals, which are then transmitted to the axle counting host. The axle counting host calculates the detection signals of each wheel sensor and ultimately outputs a safety signal indicating whether the section is occupied or idle, thereby regulating the train and ensuring railway driving safety.

[0005] In the prior art, each wheel sensor is individually connected to the axle counting host. Since the position of each wheel sensor to the axle counting host is different, the cables connecting the wheel sensor and the axle counting host vary in length. As a result, when the cable is long, it will be affected by the cable resistance, and there will be a difference between the voltage collected by the host and the voltage at the sensor output end. The longer the cable, the greater the difference. In addition, the wheel sensor is used outdoors, and the environment along the railway varies greatly. The temperature and humidity of the environment have a great impact on the wheel sensor itself and the data transmitted by the related cables.

[0006] Summary of the Invention

[0007] In view of the above problems, the purpose of this application is to provide a wheel sensor and axle counting system with high anti-interference ability, low external influence, and low manufacturing cost.

[0008] To achieve the above-mentioned objectives, the present application adopts the following technical solutions: a linear feedback circuit, comprising an oscillation circuit, an analog switch, a low-pass filter and an amplifier; the two ends of the oscillation circuit are respectively connected to the corresponding input ends of the analog switch, and one end of the oscillation circuit is also connected to the input control end of the analog switch through a signal processing module, the signal processing module is used to convert the waveform of the oscillation circuit into a square wave signal with the same frequency and phase, the input control end of the analog switch is used to receive the square wave signal with the same frequency and phase as the oscillation circuit, when the input control end of the analog switch is at a high level, one path of the analog switch is turned on; otherwise, the other path of the analog switch is turned on to achieve full-wave rectification output of the oscillation circuit waveform; the input end of the low-pass filter is connected to the output end of the analog switch, and is used to filter the full-wave rectified waveform to obtain a DC voltage signal; the input end of the amplifier is connected to the output end of the low-pass filter, and is used to amplify the DC voltage signal and output the amplified DC voltage signal to represent the oscillation amplitude of the oscillation circuit.

[0009] Furthermore, the oscillation circuit includes an excitation coil, a first induction coil, a second induction coil, a first capacitor, and a second capacitor; the excitation coil and the first induction coil and the second induction coil form a mutual inductance structure; the first induction coil is connected in parallel to the first capacitor, the second induction coil is connected in parallel to the second capacitor, and the first capacitor and the second capacitor are short-circuited to ground; one end of the first induction coil and the second induction coil are respectively connected to the corresponding input ends of the analog switch.

[0010] Furthermore, the excitation coil, the first induction coil, and the second induction coil are all integrated into a printed circuit board, the first capacitor and the second capacitor are chip capacitors on the printed circuit board, and the inductance values ​​of the first induction coil and the second induction coil are determined by the number and length of the copper foil circuit printed on the printed circuit board.

[0011] Furthermore, the low-pass filter is an RC low-pass filter.

[0012] The present application also discloses a linear feedback method, which is used for any of the above-mentioned linear feedback circuits, including: connecting the two ends of the oscillation circuit to the corresponding input ends of the analog switch, and connecting one end of the oscillation circuit to the input control end of the analog switch through a signal processing module; the waveform of the oscillation circuit is converted into a square wave signal with the same frequency and phase through the signal processing module and input into the input control end of the analog switch; when the input control end of the analog switch is at a high level, one path of the analog switch is turned on; when the input control end of the analog switch is at a low level, the other path of the analog switch is turned on to achieve full-wave rectification output of the oscillation coil waveform; a low-pass filter filters the full-wave rectified waveform output by the analog switch to obtain a DC voltage signal; the amplifier amplifies the DC voltage signal and outputs the amplified DC voltage signal, so that the oscillation amplitude of the oscillation circuit is ultimately represented by a DC voltage.

[0013] The present application also discloses a wheel sensor, comprising at least two sets of linear feedback circuits and adjustment circuits as described in any one of the above items; the linear feedback circuit is used to provide real-time feedback on the oscillation amplitude of the oscillation circuit therein to reflect the working status of the wheel sensor; the adjustment circuit is used to adjust the excitation frequency of the oscillation circuit according to the oscillation amplitude of the oscillation circuit to adaptively control the oscillation amplitude of the oscillation circuit to ensure stable operation of the wheel sensor.

[0014] Furthermore, the oscillation circuit includes an excitation coil, a first induction coil, a second induction coil, a first capacitor, and a second capacitor; the excitation coil and the first induction coil and the second induction coil form a mutual inductance structure; the first induction coil is connected in parallel to the first capacitor, the second induction coil is connected in parallel to the second capacitor, and the first capacitor and the second capacitor are short-circuited to ground; one end of the first induction coil and the second induction coil are respectively connected to the corresponding input ends of the analog switch.

[0015] Furthermore, the induction coils in each group of the linear feedback circuits are equidistant and arranged along the direction of the rails, and the oscillation frequencies of the induction coils in each group of the linear feedback circuits are set differently; and pulse signals for determining the speed and direction of the train are generated in sequence according to the order in which the train wheels pass through the first and second induction coils in each group.

[0016] Furthermore, it also includes a processing module. When three or more groups of linear feedback circuits and adjustment circuits are used, the processing module is used to compare the superimposed pulse signal widths generated by two adjacent groups of linear feedback circuits with the pulse superimposed signal widths generated by other two adjacent groups of linear feedback circuits. When the superimposed pulse widths are consistent, it is determined to be a train axle; otherwise, it is determined to be interference.

[0017] Furthermore, the excitation coil, the first induction coil, and the second induction coil are all integrated into a printed circuit board, the first capacitor and the second capacitor are chip capacitors on the printed circuit board, and the inductance values ​​of the first induction coil and the second induction coil are determined by the number and length of the copper foil circuit printed on the printed circuit board.

[0018] Furthermore, the regulation circuit includes a transistor and a PWM controller; the oscillation circuit is an LC oscillation circuit; the LC oscillation circuit is connected to the collector of the transistor; the PWM controller is connected to the emitter of the transistor; the frequency of the LC oscillation circuit is the changing frequency of the collector current, and the PWM controller output controls the emitter current of the transistor; the PWM controller controls the LC oscillation circuit to always be in a self-excited oscillation state, and controls the amplitude of the LC oscillation circuit to be a constant value.

[0019] Furthermore, the PWM controller is composed of several pulses, and the average power is controlled by changing the width of each pulse. When the pulse becomes high, the transistor is turned on and the electrical energy is input into the LC oscillation circuit; when the pulse becomes low, the transistor is cut off and the electrical energy is disconnected from the LC oscillation circuit.

[0020] Furthermore, when the output pulse frequency of the PWM increases, the pulse width of the LC oscillation circuit decreases, and when the output pulse frequency of the PWM decreases, the pulse width of the LC oscillation circuit increases. Within several cycles, the pulse width and the guarantee of the LC oscillation circuit remain unchanged.

[0021] Furthermore, the closer the PWM is to the oscillation frequency of the LC oscillation circuit, the stronger the inductive capability is.

[0022] Furthermore, the emitter of the transistor is grounded, an emitter resistor is provided between the emitter of the transistor and the ground GND, and the PWM controller collects a signal from the emitter resistor so that the frequency output by the PWM controller is always consistent with the LC oscillation circuit.

[0023] Furthermore, the LC oscillation circuit includes an inductor and a capacitor, which are connected in parallel. One end of the LC oscillation circuit is connected to a power supply, and the other end is connected to the collector of the transistor. The inductor and the capacitor form a resonant circuit. When energy flows from the transistor into the LC oscillation circuit, the LC oscillation circuit accumulates energy and reaches resonance, and then transfers the energy to the transistor.

[0024] Furthermore, when the power supply and the PWM controller are connected, the capacitor is charged. When the PWM controller is at a high level, the current flowing through the emitter resistor is composed of the current of the PWM controller and the emitter, and the current of the emitter decreases. When the PWM controller is at a low level, the current flowing through the emitter resistor increases, the current of the emitter increases, the capacitor is discharged, and the LC oscillation circuit starts to oscillate.

[0025] Furthermore, a control resistor is provided between the PWM controller and the emitter resistor; and the LC oscillation circuit is connected in parallel with a collector resistor.

[0026] Furthermore, the regulation circuit includes: three independent sensing units, three logic AND units and one logic OR unit; the first sensing unit and the second sensing unit are connected to the first logic AND unit, the second sensing unit and the third sensing unit are connected to the second logic AND unit, the first sensing unit and the third sensing unit are connected to the third logic AND unit, the first logic AND unit, the second logic AND unit, and the third logic AND unit are all connected to the input end of the logic OR unit, and the output end of the logic OR unit is connected to the axle counting host through the communication module.

[0027] Furthermore, the communication module is a CAN communication module.

[0028] Furthermore, the sensing unit includes a voltage-controlled oscillator circuit, a phase-detection filter circuit and an amplification and comparison filter circuit. The voltage-controlled oscillator circuit is communicatively connected to the phase-detection filter circuit, and the voltage-controlled oscillator circuit and the phase-detection filter circuit are both connected to the amplification and comparison filter circuit. The amplification and comparison filter circuit outputs amplitude and phase signals.

[0029] Furthermore, the voltage-controlled oscillation circuit includes an LC oscillation circuit and a voltage regulation circuit. The LC oscillation circuit is connected to the voltage regulation circuit. The voltage regulation circuit changes the component parameters of the LC oscillation circuit by adjusting the voltage.

[0030] Furthermore, the three logic AND units and one logic OR unit are provided on the MCU, and the MCU is connected to the axle counter host via an auxiliary circuit, and the auxiliary circuit is used to reduce the output voltage of the axle counter host.

[0031] Furthermore, the auxiliary circuit reduces the output voltage of the axle counter host from 24V to 5V.

[0032] Furthermore, the oscillation amplitudes of the first sensing unit, the second sensing unit and the third sensing unit are consistent.

[0033] The present invention also discloses an axle counting system for wheel sensors, comprising: a wheel sensor, a junction box and an axle counting host; the wheel sensor is used to detect the wheel rim of a train wheel and convert the detected signal from an analog signal to a digital signal; the wheel sensor is laid on the rail, and a junction box is arranged near each wheel sensor, each junction box corresponds to a wheel sensor one-to-one, and each junction box is connected to the junction boxes adjacent to it, and all the junction boxes along the line are cascaded and connected to the axle counting host; the wheel sensor is a wheel sensor as described in any of the above items.

[0034] Furthermore, a CAN interface is provided on the wheel sensor, the wheel sensor outputs a CAN signal, the axle counting host is provided with a CAN interface corresponding to the CAN interface on the wheel sensor, a CAN bus is laid between the wheel sensor and the axle counting host, and signals are transmitted between the two using the CAN bus.

[0035] Furthermore, the CAN bus uses twisted pair cables.

[0036] Furthermore, the CAN bus adopts differential technology for transmission, and the real signal received by the axle counting host in the differential technology is the voltage difference between CAN_H and CAN_L.

[0037] Furthermore, the CAN bus adopts an error checking mechanism, in which each CAN frame includes a cyclic redundancy check field. If a data error is found, the receiving end will refuse to receive the data and require the sending end to resend the data.

[0038] Furthermore, the CAN bus uses the current mode of the receiver to perform data communication.

[0039] Furthermore, the wheel sensor includes two or more sensing units, and the time when the wheel passes through each sensing unit is different. The wheel sensor calculates the time difference and sequence of the signals sensed by each sensing unit, determines the running speed and direction of the train, and transmits its signal to the axle counting host through the CAN bus.

[0040] Furthermore, the wheel sensor is provided with a derailment sensing unit for detecting whether the wheel sensor is installed on the rail. When the wheel sensor is loose, derailment information is sensed, and the wheel sensor derailment signal is converted into a digital signal and transmitted to the axle counting host via the CAN bus.

[0041] Furthermore, the wheel sensor includes a temperature sensor for measuring rail temperature changes, and the temperature monitoring signal is transmitted via the CAN bus to provide real-time temperature data and alarm information.

[0042] Due to the adoption of the above technical solution, this application has the following advantages:

[0043] The axle counting system in this application can reduce the cost of laying cables, transmit a large enough amount of data without being easily interfered with, and has high reliability. Its maximum transmission distance can reach 8 km and is not affected by the resistance of the signal line. A bus is used between multiple sensors to transmit data to the host. Only one set of sensor cables is needed to meet the signal transmission needs of 8 sensors, saving cable costs.

[0044] The axle counting system in this application uses twisted-pair differential transmission, significantly reducing common-mode interference. The CAN bus transmission mechanism effectively filters out erroneous signals and offers high anti-interference capabilities. The digital signals are capable of transmitting large amounts of data. The wheel sensors in this application utilize CAN bus transmission, utilizing only two power cables and two signal cables to transmit all sensor signals. This offers greater economic benefits than traditional parallel transmission methods, reducing costs by at least 60% compared to conventional solutions. It also effectively improves electromagnetic interference resistance and signal transmission efficiency.

[0045] The linear feedback circuit in the wheel sensor of the present application can detect the oscillation amplitude of the induction coil in real time. If the oscillation amplitude of the induction coil changes due to environmental interference, the adjustment circuit in the wheel sensor can be used to adjust the excitation frequency of the induction coil in a timely manner to ensure that the induction coil can respond in a timely manner in the case of environmental interference, ensure the normal operation of the wheel sensor, and ultimately improve the stability and reliability of the system.

[0046] The solution in this application can timely understand the working status of the induction coil, reduce the risk of external environmental factors affecting the normal working status of the induction coil, and reduce costs and PCB space; it can complete adaptive adjustment of the induction sensitivity of the wheel sensor coil without the need to maintain the working status of the wheel sensor.

[0047] In this application, the sensor PWM controller tracks the self-excited oscillation frequency of the LC oscillator circuit and controls the LC oscillator circuit's amplitude to maintain consistency, thereby ensuring that the wheel sensor's sensitivity remains unaffected by external factors. The coil's oscillation frequency is adjustable within a certain range, increasing or decreasing the coil's sensitivity. The closer the PWM control frequency is to the oscillation frequency, the stronger the sensitivity. The PWM control frequency can be preset to be off-resonance, allowing the PWM frequency to be controlled closer or further away from the oscillation circuit's resonant frequency based on environmental influences.

[0048] In this application, the sensor does not require manual adjustment of the wheel sensor during installation. The wheel sensor is controlled by PWM itself to the optimal working state. Therefore, there is no need to regularly maintain the working state of the wheel sensor during operation, which saves maintenance costs and improves the reliability of the wheel sensor.

[0049] The present application can detect wheels more accurately and reliably and output correct axle counting signals. Due to the differences between the sensing units of the wheel sensor, there is a very small probability that they will be interfered with at the same time. Therefore, even when one sensing unit of the wheel sensor fails or is interfered with, the wheel can be accurately and reliably detected and the axle counting signal can be output, thereby ensuring the reliability of the wheel sensor. The wheel sensor in the present application adopts a 2-out-of-3 logic processing method, which can work in a more severe electromagnetic environment. Even if one sensing unit is interfered with, the wheel sensor can still reliably detect the wheel and output the axle counting signal, thereby enhancing the reliability of the wheel sensor. The three sensing units of the wheel sensor use different oscillation frequencies but maintain the same oscillation amplitude, which improves the anti-interference ability and detection sensitivity of the wheel sensor itself.

[0050] In summary, the present application can be widely used in the field of rail transportation technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Various other advantages and benefits will become apparent to those skilled in the art by reading the detailed description of the preferred embodiment below. The accompanying drawings are only for the purpose of illustrating the preferred embodiment and are not to be considered as limiting the present application. Throughout the drawings, the same reference numerals are used to represent the same components.

[0052] In the picture:

[0053] FIG1 is a schematic diagram of line resistance changed by ambient temperature in the prior art;

[0054] FIG2 is a schematic diagram of a connection method of a wheel sensor axle counting system in the prior art;

[0055] FIG3 is a schematic structural diagram of a wheel sensor cascade method according to an embodiment of the present application;

[0056] FIG4 is a diagram of wheel sensor level connection lines in one embodiment of the present application;

[0057] FIG5 is a schematic diagram of a CAN bus anti-interference principle using differential technology in one embodiment of the present application;

[0058] FIG6 is a schematic structural diagram of a linear feedback circuit according to an embodiment of the present application;

[0059] FIG7 is a schematic diagram showing the principle of an analog switch of a linear feedback circuit in an embodiment of the present application;

[0060] FIG8 is a schematic structural diagram of an oscillation circuit of a linear feedback circuit in an embodiment of the present application;

[0061] FIG9 is a schematic structural diagram of a wheel sensor according to an embodiment of the present application;

[0062] FIG10 is a schematic diagram of a regulating circuit in one embodiment of the present application;

[0063] FIG11 is a schematic structural diagram of a wheel sensor based on 2-out-of-2 in the prior art;

[0064] FIG12 is a schematic structural diagram of a wheel sensor based on 2 out of 3 in one embodiment of the present application;

[0065] FIG13 is a schematic structural diagram of a sensing unit of a wheel sensor in an embodiment of the present application. DETAILED DESCRIPTION

[0066] The following will describe exemplary embodiments of the present application in more detail with reference to the accompanying drawings. Although exemplary embodiments of the present application are shown in the accompanying drawings, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments described herein. Instead, these embodiments are provided to enable a more thorough understanding of the present application and to fully convey the scope of the present application to those skilled in the art.

[0067] The following will describe exemplary embodiments of the present application in more detail with reference to the accompanying drawings. Although exemplary embodiments of the present application are shown in the accompanying drawings, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments described herein. Instead, these embodiments are provided to enable a more thorough understanding of the present application and to fully convey the scope of the present application to those skilled in the art.

[0068] It should be understood that the terms used herein are for the purpose of describing specific example embodiments only and are not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms "one", "an" and "said" as used herein may also be meant to include plural forms. The terms "comprise", "include", "contain" and "have" are inclusive and therefore specify the presence of stated features, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, steps, operations, elements, parts, and / or combinations thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring them to be performed in the specific order described or illustrated, unless the order of execution is clearly indicated. It should also be understood that additional or alternative steps may be used.

[0069] Although the terms first, second, third, etc. can be used in the text to describe multiple elements, components, regions, layers and / or sections, these elements, components, regions, layers and / or sections should not be limited by these terms. These terms can only be used to distinguish an element, component, region, layer or section from another region, layer or section. Unless the context clearly indicates otherwise, terms such as "first", "second" and other numerical terms do not imply order or sequence when used in the text. Therefore, the first element, component, region, layer or section discussed below can be referred to as the second element, component, region, layer or section without departing from the teaching of the example embodiments.

[0070] The various aspects of the illustrative embodiments will be described using terms commonly used by those skilled in the art to convey the essence of their work to others skilled in the art. However, it will be apparent to those skilled in the art that alternative embodiments may be implemented using only some of the described aspects. For illustrative purposes, specific numbers, materials, and configurations are provided to provide a thorough understanding of the illustrative embodiments. However, it will be apparent to those skilled in the art that alternative embodiments may be implemented without these specific details. In other cases, well-known features may be omitted or simplified so as not to obscure the illustrative embodiments.

[0071] The phrase "A and / or B" means (A), (B), or (A and B). The phrases "A / B" and "A or B" mean (A), (B), or (A and B), similar to the phrase "A and / or B."

[0072] In railway signaling systems, electronic axle counting systems are used to monitor track sections. These systems count the axles of vehicles entering and exiting a section. They utilize vehicle sensors, electronic units, and an axle counter to analyze and calculate whether a section is occupied by a vehicle. The system records and compares the axle counts of trains entering and exiting the section. The basic structure of an electronic axle counting system consists of an outdoor section and an indoor section. The outdoor section includes vehicle sensors, electronic units, and transmission cables, while the indoor section primarily features signal processing and counting circuits. A dedicated axle counting cable connects the indoor and outdoor equipment.

[0073] To address the issues of cable resistance affecting long cables, resulting in a difference between the voltage collected by the host and the voltage at the sensor output. The longer the cable, the greater the difference. Furthermore, wheel sensors are used outdoors, and the environment along railway lines varies greatly, significantly affecting the wheel sensors themselves and the data transmitted by the associated cables due to temperature and humidity. This application proposes a linear feedback circuit, method, wheel sensor, and axle counting system, comprising: a wheel sensor for detecting the rim of a train wheel and converting the detected signal from analog to digital. The wheel sensor is installed on the rails, and a junction box is positioned near each wheel sensor. Each junction box corresponds to a wheel sensor and is connected to its adjacent junction boxes. All junction boxes along the track are cascaded and connected to the axle counting host. The wheel sensor includes a linear feedback circuit for real-time feedback of the oscillation amplitude of its internal oscillator circuit, and a frequency adjustment circuit for adjusting the excitation frequency of the oscillator circuit based on the oscillation amplitude of the oscillation circuit, thereby adaptively controlling the oscillation amplitude of the oscillation circuit and ensuring stable operation of the wheel sensor. This axle counting system reduces cabling costs, transmits large amounts of data, is resistant to interference, and offers high reliability. Its maximum transmission distance reaches 8 km, unaffected by signal line resistance. Multiple sensors use a bus to transmit data to a host computer, requiring only one set of sensor cables to transmit signals from eight sensors, saving cabling costs. This system will be described below using an embodiment with accompanying drawings.

[0074] Example 1

[0075] In the prior art, each wheel sensor is individually connected to the axle counter host. Since the position of each wheel sensor to the axle counter host is different, the cables connecting the wheel sensor and the axle counter host vary in length. When the cable is long, it will be affected by the cable resistance, resulting in a difference between the voltage collected by the host and the voltage at the sensor output end. The longer the cable, the greater the difference. The cable resistance will change with the ambient temperature, as shown in Figure 1. As a result, the signal collected by the axle counter host will also change with the ambient temperature, resulting in inaccurate wheel sensor signals collected by the axle counter host.

[0076] On the other hand, the analog signals transmitted by the wheel sensors are susceptible to electromagnetic interference, and the probability of signal transmission errors is high; the transmitted data is single and the data volume is small; the signal lines transmitted from each sensor to the host are transmitted in parallel and independently, as shown in Figure 2, which requires the layout of a large number of cables, and the cable laying cost is high.

[0077] This embodiment discloses an axle counting system of a wheel sensor, as shown in Figures 3 and 4, comprising: a wheel sensor, a junction box and an axle counting host;

[0078] Wheel sensors detect the rims of train wheels and convert the detected signals from analog to digital. Wheel sensors are installed on the rails according to train operation requirements. The rails are divided into several sections, and a junction box is placed near each wheel sensor. Each junction box corresponds to a wheel sensor and is connected to the adjacent junction boxes before and after it, such as the second junction box connecting to the first and third junction boxes. All junction boxes along the line are cascaded via the CAN bus, and all wheel sensors are connected to the axle counting host. The host counts the number of wheels detected by each wheel sensor, determines whether a section is occupied or idle, and outputs this information to the interlocking system. The wheel sensors installed on the rails are cascaded with the remaining wheel sensors via the junction box, and the signals are ultimately transmitted to the host via four cables, saving cabling. Compared to traditional sensors where each sensor signal line is directly connected to the host, this cascaded approach saves approximately 60% in cabling costs.

[0079] The wheel sensor in this embodiment includes: at least two sets of linear feedback circuits and adjustment circuits;

[0080] The linear feedback circuit is used to provide real-time feedback of the oscillation amplitude of the oscillation circuit therein to reflect the working status of the wheel sensor;

[0081] The regulating circuit is used to regulate the excitation frequency of the oscillation circuit according to the oscillation amplitude of the oscillation circuit, so as to adaptively control the oscillation amplitude of the oscillation circuit and ensure the stable operation of the wheel sensor.

[0082] The CAN bus interface circuit includes a CAN bus controller, an optical coupler and a CAN bus transceiver. The CAN bus controller and the CAN bus transceiver communicate with each other through the optical coupler. The CAN bus controller is used to control the signal transmission and fault alarm signal of the axle counting system.

[0083] The CAN bus uses differential transmission technology, meaning the difference in signal value is transmitted between the two signal lines. Signals are transmitted via the voltage difference between the sending and receiving lines. Using differential technology, the actual signal received by the axle counter host is the voltage difference between CAN_H and CAN_L. As shown in Figure 5, when the signal is subject to external interference, both CAN_H and CAN_L are affected, but the voltage difference remains unchanged, ultimately ensuring that the signal received by the host is unaffected. This transmission method minimizes the impact of noise caused by external electromagnetic interference on the signal and transmission losses on the signal lines, ensuring stable and reliable signal transmission over longer distances. Although interference signals may act on both signal lines simultaneously, their effects are offset by the receiver's calculation of the differential signal, ensuring accurate data transmission.

[0084] The CAN bus uses an error checking mechanism to ensure transmission reliability. In the error checking mechanism, each CAN frame contains a CRC (cyclic redundancy check) field, which can verify the data and detect whether there are transmission errors. If a data error is found, the receiving end will refuse to receive it and require the sending end to resend the data to ensure the accuracy and integrity of the transmission.

[0085] The CAN bus also features a multi-layer message prioritization and arbitration mechanism to ensure that high-priority messages are transmitted promptly within the network. This allows the CAN bus to arbitrate according to specific rules when multiple nodes are sending data simultaneously, preventing data conflicts and collisions while ensuring the order and reliability of data transmission.

[0086] Specifically, the wheel sensor includes two or more sensing units. The wheel passes each sensing unit at a different time. The wheel sensor calculates the time difference and sequence of the signals sensed by each sensing unit to determine the train's speed and direction. The signals are then transmitted to the axle counter host via a bus, enabling real-time monitoring of the train's speed. The bus is a CAN bus. The wheel sensor is provided with a CAN interface, which outputs CAN signals. The axle counter host is provided with a CAN interface corresponding to the CAN interface on the wheel sensor. The CAN bus is laid between the wheel sensor and the axle counter host, and signals are transmitted between the two using the CAN bus. The wheel sensor may also be provided with an RS485 or other interface, with the corresponding wheel sensor outputting an RS485 or other corresponding signal. The corresponding interface on the axle counter host may also be configured as an RS485 or other interface, transmitting RS485 or other corresponding digital signals between the two.

[0087] In this embodiment, the CAN bus uses the receiver's current mode for data communication, rather than the traditional voltage mode. Therefore, the strength of the transmitted signal is less dependent on the resistance of the signal line, ensuring that the transmission distance is not limited by line resistance. This makes the CAN bus transmission method highly resistant to interference and adaptable in industrial environments, enabling long-distance data transmission, with a single CAN bus capable of transmitting up to 8 kilometers.

[0088] Example 2

[0089] This embodiment improves the linear feedback circuit in the wheel sensor based on the first embodiment. The oscillation amplitude of the induction coil of the wheel sensor can be affected by environmental changes and wheel induction. This embodiment proposes a linear feedback circuit that can overcome the influence of environmental changes on the wheel sensor. As shown in Figures 6 and 7, the linear feedback circuit includes an oscillator circuit, an analog switch, a low-pass filter, and an amplifier.

[0090] One end of the oscillation circuit is connected to the input end of the analog switch, and the other end is connected to the input control end of the analog switch through a signal processing module, wherein the signal processing module is used to convert the waveform of the oscillation circuit into a square wave signal with the same frequency and phase. The input control end of the analog switch is used to receive the square wave signal with the same frequency and phase as the oscillation circuit. Since the oscillation frequency of the oscillation circuit is consistent with the frequency of the input control end of the analog switch, when the input control end of the analog switch is at a high level, one path of the analog switch is turned on; when the input control end of the analog switch is at a low level, the other path of the analog switch is turned on, thereby realizing full-wave rectification output of the oscillation circuit waveform;

[0091] The input end of the low-pass filter is connected to the output end of the analog switch, and is used to filter the full-wave rectified waveform output by the analog switch to obtain a DC voltage signal;

[0092] The input end of the amplifier is connected to the output end of the low-pass filter. The amplifier amplifies the DC voltage signal by adjusting the resistor and outputs the amplified DC voltage signal, so that the oscillation amplitude of the oscillation circuit is finally represented by a DC voltage.

[0093] In this embodiment, the wheel sensor provides real-time feedback on the oscillation amplitude of the induction coil, enabling timely monitoring of the coil's oscillation status. The oscillation amplitude is maximum when the induction coil's oscillation frequency matches the excitation frequency. In the wheel sensor, if environmental changes cause the induction coil's oscillation amplitude to change, the linear feedback circuit promptly reports this change, and the regulation circuit automatically adjusts the excitation frequency, thereby adaptively controlling the induction coil's oscillation amplitude. This ensures stable operation of the wheel sensor, unaffected by environmental factors, ultimately improving system stability and reliability.

[0094] The waveform mentioned in this embodiment is preferably a sine wave, but is not limited thereto and may also be other waveforms, such as a pulse wave.

[0095] In a preferred embodiment, when the oscillation amplitude of the oscillation circuit changes, the output of the amplifier also changes with the amplitude of the induction coil, and the change relationship is linear. The data is shown in Table 1 below:

[0096] Table 1 Comparison of peak-to-peak values ​​of induction coil and amplifier output

[0097] In this embodiment, the oscillation circuit, as shown in FIG8 , includes an excitation coil, a first induction coil, a second induction coil, a first capacitor, and a second capacitor. The excitation coil and the first and second induction coils form a mutual induction structure, which can be implemented using windings to maintain and control the circuit's oscillation. The first induction coil is connected in parallel with the first capacitor, the second induction coil is connected in parallel with the second capacitor, and the first and second capacitors are short-circuited to ground. One end (① and ②) of the first and second induction coils is connected to the corresponding input end of an analog switch, respectively. The induction coils in each set of linear feedback circuits are equidistant and arranged along the rail direction, and the oscillation frequency of the induction coils in each set of linear feedback circuits is set differently. Pulse signals for determining the train's running direction and speed are generated sequentially based on the order in which the train wheels pass through each set of the first and second induction coils. This embodiment provides only an example of a preferred oscillation circuit, and does not limit the use of this type of oscillation circuit. For example, a traditional LC oscillation circuit can also be used.

[0098] Specifically, the excitation coil, first induction coil, and second induction coil are all integrated on a printed circuit board. The first and second capacitors are chip capacitors on the printed circuit board. The inductance of the first and second induction coils is determined by the number and length of turns of the copper foil printed on the printed circuit board. The integrated design of the coils and capacitors on the printed circuit board makes the oscillation circuit more compact. The printed circuit board circuit is easy to manufacture, and the coils are highly consistent. The resulting inductance is more accurate than that of traditional wire-wound inductors, ensuring stable operation of the oscillation circuit, reliable operation of the linear feedback circuit, and high detection accuracy.

[0099] In this embodiment, the low-pass filter is preferably an RC low-pass filter, but is not limited thereto.

[0100] The linear feedback method of the linear feedback circuit in the wheel sensor of this embodiment is:

[0101] 1) Connect the two ends of the oscillation circuit to the corresponding input ends of the analog switch respectively, and connect one end of the oscillation circuit 1 to the input control end of the analog switch through the signal processing module.

[0102] 2) The waveform of the oscillation circuit is converted into a square wave signal with the same frequency and phase through the signal processing module and input into the input control terminal of the analog switch.

[0103] 3) When the input control terminal of the analog switch is at a high level, one path of the analog switch is turned on; when the input control terminal of the analog switch is at a low level, the other path of the analog switch is turned on, realizing full-wave rectification output of the oscillation coil waveform.

[0104] 4) The low-pass filter filters the full-wave rectified waveform output by the analog switch to obtain a DC voltage signal.

[0105] 5) The amplifier amplifies the DC voltage signal and outputs the amplified DC voltage signal, so that the oscillation amplitude of the oscillation circuit is ultimately represented by a DC voltage. When the DC voltage changes, the oscillation coil is disturbed.

[0106] Example 3

[0107] This embodiment improves upon the wheel sensor of the second embodiment. In this embodiment, the first and second induction coils of the oscillator circuit in each linear feedback circuit are equidistant and arranged along the rail, operating independently of each other. The oscillation frequencies of the first and second induction coils in each linear feedback circuit are set differently. Pulse signals are generated sequentially based on the order in which the train wheels pass each set of first and second induction coils, used to determine the train's direction and speed. The waveforms generated by the oscillator circuits are used to detect the wheels.

[0108] In a preferred embodiment, the wheel sensor also includes a processing module. When three or more groups of linear feedback circuits are used, the processing module is used to compare the width of the superimposed pulse signal generated by two adjacent groups of linear feedback circuits with the width of the pulse superimposed signal generated by other two adjacent groups of linear feedback circuits. When the superimposed pulse widths are consistent, the processing module determines it as a train axle; otherwise, the processing module determines it as interference, thereby improving the reliability of the wheel sensor.

[0109] Example 4

[0110] This embodiment improves the regulation circuit in the wheel sensor based on the first embodiment. As shown in Figure 9 , the regulation circuit of the wheel sensor in this embodiment includes an oscillator circuit, a transistor, and a PWM controller. One end of the oscillator circuit is connected to the power supply VCC1, and the other end is connected to the collector of the transistor. An emitter resistor R3 is provided between the emitter of the transistor and ground GND, and the PWM controller is connected to the emitter of the transistor. The frequency of the oscillator circuit is the frequency of the collector current. The PWM controller output controls the emitter current of the transistor and collects the signal from the emitter resistor R3 to ensure that the frequency output by the PWM controller is consistent with that of the oscillator circuit. The PWM controller controls the oscillator circuit to always be in a self-excited oscillation state and maintains a constant amplitude. The emitter of the transistor is grounded. The amplitude of the oscillation circuit's pulse signal is collected and compared with the amplitude of the reference pulse signal in the PWM controller. If the amplitude matches the reference pulse signal, the PWM output frequency does not need to be changed. However, if environmental factors cause the oscillation circuit's self-oscillation amplitude to change, the amplitude of the oscillation circuit's pulse signal will become inconsistent with the reference pulse signal in the PWM controller, requiring a change in the PWM output frequency. By varying the PWM output frequency, the axle counter wheel sensor further adjusts the oscillation circuit's frequency, ensuring the self-oscillation amplitude of the oscillation circuit remains constant, reducing the risk of changes in wheel sensing sensitivity.

[0111] In this embodiment, the above function is completed by a comparator, that is, if the amplitude of the pulse signal of the LC oscillation circuit is the same as the reference pulse signal in the PWM controller, a low-frequency signal is input; if the amplitude of the pulse signal is different, a high-frequency signal is input.

[0112] When the frequency of the control signal output by the PWM controller changes, the total pulse width of the oscillator circuit remains consistent. That is, when the PWM output pulse frequency increases, the pulse width of the oscillator circuit decreases, and when the PWM output pulse frequency decreases, the pulse width of the oscillator circuit increases. Over several cycles, the pulse width of the oscillator circuit is guaranteed to remain unchanged. This ensures that the amplitude of the oscillator circuit is consistent, maintaining the same magnetic field strength of the sensor and, therefore, the sensitivity to the train wheels.

[0113] As shown in Figure 10, in this embodiment, the oscillator circuit is an LC oscillator circuit connected in parallel with a collector resistor R1. The LC oscillator circuit includes an inductor and a capacitor connected in parallel. One end of the LC oscillator circuit is connected to a power supply, and the other end is connected to the collector of the transistor. The inductor and capacitor form a resonant circuit that can generate self-oscillation under certain conditions. When energy flows from the transistor into the LC oscillator circuit, the LC oscillator circuit accumulates energy and reaches resonance, then transfers the energy to the transistor. This energy exchange cycle may cause the oscillation frequency to match the frequency of the PWM signal. Due to the presence of the LC oscillator circuit, the frequency of the LC oscillator circuit can be controlled within a certain range using a PWM controller. In this embodiment, the LC oscillator circuit L and C are integrally formed on a printed circuit board. L is a copper foil coil, the number of turns and length of which are determined according to actual needs, and C is the distributed capacitance of the copper foil. The inductance value of L is determined by setting the number of turns and length of the copper foil trace on the printed circuit board, and the capacitance value of C is determined by setting the width and number of layers of the copper foil trace on the printed circuit board. This determines the desired oscillation frequency of the wheel sensor LC oscillator circuit. Both L and C are integrated into the printed circuit board, making the LC oscillator circuit more compact and easier to manufacture. The resulting inductance and capacitance are highly accurate, ensuring stable operation of the LC oscillator circuit, resulting in reliable wheel sensor operation and high detection accuracy. When the PWM signal's frequency mismatches with the LC oscillator circuit's, some effects occur, including changes in amplitude and other characteristics.

[0114] When the power supply and PWM controller are connected, capacitor C1 is charged. When the PWM controller is at a high level, the current flowing through the emitter resistor R3 is composed of the current of the PWM controller and the emitter, and the emitter current decreases. When the PWM controller is at a low level, the current flowing through the emitter resistor R3 increases, the emitter current increases, the capacitor discharges, and the LC oscillation circuit starts to oscillate.

[0115] Amplitude attenuation: If the PWM signal frequency is significantly higher or lower than the resonant frequency of the LC self-oscillating circuit, the LC oscillating circuit may not be able to effectively absorb energy from the PWM signal or convert it into internal energy. This can cause the oscillating circuit's amplitude to attenuate. The smaller the oscillating circuit's amplitude, the lower the energy of the output signal.

[0116] Waveform distortion: Frequency mismatch can cause uneven energy exchange between the PWM signal and the LC self-oscillator circuit, resulting in waveform distortion. The shape and amplitude of the PWM signal may change due to interaction with the oscillator circuit, which can affect the stability and accuracy of the output signal.

[0117] Increased power consumption: When the PWM signal frequency does not match the oscillator circuit frequency, the oscillator circuit's energy efficiency may decrease. This means that more power is consumed in the circuit rather than effectively converted into the output signal. This may affect the circuit's efficiency and heat generation.

[0118] When a PWM signal is connected to the emitter of a transistor and the collector of the transistor is connected to an LC oscillator circuit, this configuration can produce resonance, causing the oscillation frequency to match the PWM signal frequency. Specifically, if the resonant frequency of the LC oscillator circuit is exactly equal to the PWM signal frequency, resonance will occur between the two. Near the resonant frequency, the LC oscillator circuit will more easily absorb energy from the PWM signal and effectively convert it into energy within the resonant circuit. This can cause the LC oscillator circuit to return some energy to the input through the collector, affecting the amplitude and shape of the PWM signal and causing the oscillation frequency to align with the PWM frequency. Therefore, the closer the PWM is to the oscillation frequency of the LC oscillator circuit, the stronger the induction capability.

[0119] A control resistor R4 is provided between the PWM controller and the emitter resistor R3.

[0120] The PWM controller consists of a series of pulses, controlling average power by varying the width of each pulse. When the pulse is high, the transistor conducts, feeding energy into the LC oscillator circuit; when the pulse is low, the transistor cuts off, disconnecting the energy from the LC oscillator circuit. The PWM controller maintains a consistent output pulse width over N cycles, ensuring a consistent LC oscillation amplitude. This means that while the oscillation frequency can vary slightly with environmental conditions, the amplitude remains constant, ensuring that the wheel sensor's sensitivity is unaffected by environmental fluctuations. In this embodiment, N is a positive integer.

[0121] The output signal frequency of the PWM controller is consistent with the self-excited oscillation frequency of the LC oscillation circuit, which can reduce the power consumption and heat generation of the wheel sensor itself, thereby reducing the influence of the wheel sensor's own factors on the oscillation amplitude, thereby affecting the sensing sensitivity of the wheel sensor and improving the working reliability of the wheel sensor.

[0122] Example 5

[0123] With the development of rail transit, wheel sensors have also gained widespread application. Existing wheel sensors use a 2-out-of-2 logic processing method, as shown in Figure 11. This means that two different sensing units within the wheel sensor detect the wheel. Only when both sensing units detect wheel signals and meet certain axle counting conditions will the axle counting signal be output to the axle counting host. Due to the harsh and complex electromagnetic environments in which wheel sensors are used, if interference occurs and one of the sensing units cannot accurately and reliably detect the wheel signal, or if one of the sensing units fails and cannot accurately and reliably detect the wheel signal, the 2-out-of-2 logic processing method will prevent the axle counting system from outputting the corresponding axle counting signal, leading to failures such as lost axles and multiple axles. Existing wheel sensors have poor anti-interference capabilities and low axle counting accuracy.

[0124] This embodiment improves the wheel sensor based on the second embodiment. The wheel sensor in this embodiment adopts a 2-out-of-3 logic processing method, as shown in FIG12 , and includes: three independent sensing units, three logic AND units, and one logic OR unit;

[0125] The first and second sensing units are connected to the first logical AND unit, the second and third sensing units are connected to the second logical AND unit, and the first and third sensing units are connected to the third logical AND unit. In other words, each sensing unit outputs two signals, and each logical AND unit receives two signals, each from a different sensing unit. The first, second, and third logical AND units are all connected to the input of the logical OR unit. The output of the logical OR unit is connected to the axle counting host via a communication module. The logical OR unit outputs a wheel signal, which is transmitted to the axle counting host via the communication module.

[0126] In this embodiment, three logical AND units and one logical OR unit are installed on the MCU (microcontroller unit) and are constructed by the MCU. The MCU collects wheel signals from the sensing units, which include amplitude and phase signals, and determines whether the sensing unit has detected a wheel. When the wheel signals from any two of the three sensing units meet the axle counting signal conditions, the MCU outputs the axle counting signal to the axle counting host. Specifically, the axle counting signal is sent via the CAN bus to the axle counting host, which then outputs segment occupied and idle signals. When a wheel passes through a sensing unit, the internal circuit parameters of the sensing unit change, generating a wheel signal. Due to the use of a 2-out-of-3 logic processing method, the wheel sensor can still accurately and reliably detect the wheel and output a reliable axle counting signal even if one sensing unit is interfered with or fails.

[0127] The first, second, and third sensing units use different oscillation frequencies but consistent oscillation amplitudes. These different oscillation frequencies reduce mutual interference between the three sensing units. The oscillation frequency is set near the frequency at which the metal of the train wheel is most sensitive. Setting the oscillation amplitudes consistent across the three sensing units ensures consistent sensitivity to the train wheel, improving the wheel sensor's detection performance.

[0128] The communication module is a CAN communication module. Axle counting signals are transmitted to the axle counting host via the CAN bus. Information between the wheel sensors and the axle counting host is transmitted via the bus. The wheel sensors are powered by the axle counting host, which provides a 24V voltage. The MCU is connected to the axle counting host via an auxiliary circuit that reduces the host's output voltage from 24V to 5V.

[0129] As shown in Figure 13, the sensing unit includes a voltage-controlled oscillator circuit, a phase-detection filter circuit, and an amplification, comparison, and filtering circuit. The voltage-controlled oscillator circuit is communicatively connected to the phase-detection filter circuit, and both circuits are connected to the amplification, comparison, and filtering circuit, which outputs amplitude and phase signals. When a wheel passes over the sensing unit, the oscillation amplitude of the voltage-controlled oscillator circuit decreases, and the phase changes, generating a phase difference. The amplitude change is converted into an amplitude signal by the amplification, comparison, and filtering circuit unit, and the phase difference is converted into a phase voltage signal through phase detection and filtering.

[0130] The voltage-controlled oscillation circuit includes an LC oscillation circuit and a voltage regulation circuit. The LC oscillation circuit is connected to the voltage regulation circuit. The coil L of the LC oscillation circuit not only participates in the oscillation, but also generates a magnetic field to induce the train wheels. The voltage regulation circuit changes the component parameters of the LC oscillation circuit by adjusting the voltage, thereby achieving adjustable frequency. The voltage regulation circuit is controlled by the MCU to input a pulse level signal. The amplitude of the input pulse signal of each sensing unit is different, so that the three sensing units oscillate at different frequencies. By adjusting the input voltage of the oscillation circuit, the MCU can achieve precise control of the oscillation frequency of the three sensing units and reduce mutual interference between the wheel sensors themselves. The MCU controls the pulse width of the output pulse signal, controls the amplitude of the oscillation circuit to be consistent, and ensures the sensing sensitivity of the wheel sensor. The LC oscillation circuit circuit of this embodiment includes an inductor and a capacitor, and the inductor and capacitor are connected in parallel.

[0131] In this embodiment, the LC oscillator circuit, L and C, are integrated on a printed circuit board. L is a copper foil coil, the number of turns and length of which are determined based on actual needs, and C is the distributed capacitance of the copper foil. The inductance of L is determined by setting the number of turns and length of the copper foil traces on the printed circuit board, while the capacitance of C is determined by setting the width and number of layers of the copper foil traces on the printed circuit board. This determines the desired oscillation frequency of the wheel sensor's LC oscillator circuit. The integration of L and C on the printed circuit board makes the LC oscillator circuit more compact and easier to manufacture. The resulting inductance and capacitance values ​​are highly accurate, ensuring stable operation of the LC oscillator circuit, resulting in reliable operation and high detection accuracy for the wheel sensor.

[0132] The wheel sensor utilizes a 2-out-of-3 logic processing method, enabling operation in harsh electromagnetic environments. Even if one sensing unit is interfered with, the wheel sensor can still reliably detect the wheel and output an axle counting signal, enhancing its reliability. The three sensing units of the wheel sensor utilize different oscillation frequencies but maintain consistent amplitudes, improving the sensor's anti-interference capabilities and detection sensitivity.

[0133] Example 6

[0134] This embodiment improves the wheel sensor based on the first embodiment. In this embodiment, a derailment sensing unit is provided on the wheel sensor to detect whether the wheel sensor is installed on the rail. When the wheel sensor is loose, derailment information is sensed. The wheel sensor derailment signal is converted into a digital signal and transmitted to the axle counting host via the CAN bus to realize real-time monitoring of the train running speed.

[0135] Example 7

[0136] This embodiment improves the wheel sensor based on the first embodiment. In this embodiment, a temperature sensor is provided on the wheel sensor to measure the temperature change of the rail, thereby realizing temperature monitoring and control. The temperature monitoring signal can also be transmitted via the CAN bus to provide real-time temperature data and alarm information.

[0137] The above embodiments are only used to illustrate the present application, wherein the structure, connection method and manufacturing process of each component can be changed. Any equivalent transformations and improvements based on the technical solution of the present application should not be excluded from the scope of protection of the present application.

[0138] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and are not intended to limit them. Although the present application has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present application can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not deviate from the spirit and scope of the present application should be included in the scope of protection of the claims of the present application. The above content is only a specific implementation method of the present application, but the scope of protection of the present application is not limited to this. Any technician familiar with the technical field can easily think of changes or replacements within the technical scope disclosed in the present application, which should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A wheel sensor, characterized in that: The wheel sensor comprises a linear feedback circuit, wherein the linear feedback circuit is used to feed back the oscillation amplitude of the oscillation circuit therein in real time to reflect the working state of the wheel sensor; the wheel sensor also comprises an adjustment circuit, wherein the adjustment circuit is used to adjust the excitation frequency of the oscillation circuit according to the oscillation amplitude of the oscillation circuit to adaptively control the oscillation amplitude of the oscillation circuit; the oscillation circuit comprises an excitation coil, a first induction coil, a second induction coil, a first capacitor and a second capacitor; The excitation coil and the first induction coil and the second induction coil form a mutual inductance structure; the first induction coil is connected to the first capacitor in parallel, the second induction coil is connected to the second capacitor in parallel, and the first capacitor and the second capacitor are short-circuited to ground; one end of the first induction coil and the second induction coil are respectively connected to the input ends corresponding to the analog switch.

2. A wheel sensor as claimed in claim 1, characterized in that: The linear feedback circuit is used to turn on one path of the analog switch when a high level is input to the analog switch, and to turn on the other path of the analog switch when a high level is input; the linear feedback circuit also includes an oscillation circuit and a signal processing module, the two ends of the oscillation circuit are respectively connected to the corresponding input ends of the analog switch, one end of the oscillation circuit is also connected to the input control end of the analog switch through the signal processing module, and the signal processing module is used to convert the waveform of the oscillation circuit into a square wave signal with the same frequency and phase.

3. A wheel sensor as claimed in claim 2, characterized in that: The oscillation circuit comprises an excitation coil, a first induction coil, a second induction coil, a first capacitor and a second capacitor; The excitation coil and the first induction coil and the second induction coil form a mutual inductance structure; the first induction coil is connected to the first capacitor in parallel, the second induction coil is connected to the second capacitor in parallel, and the first capacitor and the second capacitor are short-circuited to ground; one end of the first induction coil and the second induction coil are respectively connected to the input ends corresponding to the analog switch.

4. A wheel sensor as claimed in claim 3, characterized in that: The excitation coil, the first induction coil and the second induction coil are all integrated with a printed circuit board. The first capacitor and the second capacitor are chip capacitors on the printed circuit board. The inductance values ​​of the first induction coil and the second induction coil are determined by the number of turns and length of the copper foil circuit printed on the printed circuit board.

5. A wheel sensor as claimed in claim 2, characterized in that: The excitation coil, the first induction coil and the second induction coil are all integrated with a printed circuit board. The first capacitor and the second capacitor are chip capacitors on the printed circuit board. The inductance values ​​of the first induction coil and the second induction coil are determined by the number of turns and length of the copper foil circuit printed on the printed circuit board.

6. A wheel sensor according to any one of claims 1 to 5, characterized in that: The linear feedback circuit also includes a low-pass filter and an amplifier. The input end of the low-pass filter is connected to the output end of the analog switch, and is used to filter the waveform after full-wave rectification to obtain a DC voltage signal; the input end of the amplifier is connected to the output end of the low-pass filter, and is used to amplify the DC voltage signal and output the amplified DC voltage signal to represent the oscillation amplitude of the oscillation circuit. The low-pass filter adopts an RC low-pass filter.

7. A wheel sensor according to any one of claims 1 to 5, characterized in that: The induction coils in each group of the linear feedback circuits are arranged equidistantly and along the rail direction; the oscillation frequencies of the induction coils in each group of the linear feedback circuits are set differently.

8. A wheel sensor as claimed in claim 1, characterized in that: According to the order in which the train wheels pass through each group of the first induction coil and the second induction coil, pulse signals for determining the speed and direction of the train are generated in sequence.

9. A wheel sensor as claimed in claim 10, characterized in that: The wheel sensor also includes a processing module. When three or more groups of linear feedback circuits and adjustment circuits are used, the processing module is used to compare the width of the superimposed pulse signal generated by two adjacent groups of linear feedback circuits with the width of the pulse superimposed signal generated by other two adjacent groups of linear feedback circuits. When the superimposed pulse widths are consistent, it is determined to be a train axle, otherwise it is determined to be interference.

10. A wheel sensor as claimed in claim 9, characterized in that: The excitation coil, the first induction coil and the second induction coil are all integrated with a printed circuit board, and the first capacitor and the second capacitor are chip capacitors on the printed circuit board.

11. A wheel sensor as claimed in claim 10, characterized in that: The inductance values ​​of the first induction coil and the second induction coil are determined by the number of turns and length of the copper foil circuit printed on the printed circuit board.

12. A wheel sensor as claimed in claim 1, characterized in that: The regulation circuit includes a transistor and a PWM controller; the oscillation circuit is an LC oscillation circuit; the LC oscillation circuit is connected to the collector of the transistor; the PWM controller is connected to the emitter of the transistor; the frequency of the LC oscillation circuit is the changing frequency of the collector current, and the PWM controller output controls the emitter current of the transistor; the PWM controller controls the LC oscillation circuit to always be in a self-excited oscillation state, and controls the amplitude of the LC oscillation circuit to be a constant value.

13. The wheel sensor according to claim 12, characterized in that: The PWM controller is composed of a number of pulses, and the average power is controlled by changing the width of each pulse. When the pulse becomes high, the transistor is turned on and the electric energy is input into the LC oscillation circuit; When the pulse goes low, the transistor is cut off, disconnecting the power from the LC oscillating circuit.

14. The wheel sensor according to claim 12, characterized in that: When the output pulse frequency of the PWM increases, the pulse width of the LC oscillation circuit decreases, and when the output pulse frequency of the PWM decreases, the pulse width of the LC oscillation circuit increases. Within several cycles, the pulse width and guarantee of the LC oscillation circuit remain unchanged.

15. The wheel sensor according to claim 12, characterized in that: The closer the PWM is to the oscillation frequency of the LC oscillation circuit, the stronger the inductive capability is.

16. The wheel sensor according to claim 13, characterized in that: The emitter of the transistor is grounded, and an emitter resistor is arranged between the emitter of the transistor and the ground GND.

17. The wheel sensor according to claim 16, characterized in that The PWM controller collects the signal of the emitter resistor so that the frequency output by the PWM controller is always consistent with the LC oscillation circuit.

18. The wheel sensor according to claim 17, characterized in that The LC oscillation circuit includes an inductor and a capacitor, which are connected in parallel. One end of the LC oscillation circuit is connected to a power supply, and the other end is connected to the collector of the transistor. The inductor and the capacitor form a resonant circuit. When energy flows from the transistor into the LC oscillation circuit, the LC oscillation circuit accumulates energy and reaches resonance, and then transfers the energy to the transistor.

19. The wheel sensor according to claim 16, characterized in that: When the power supply and PWM controller are connected, the capacitor is charged. When the PWM controller is at a high level, the current flowing through the emitter resistor is composed of the current of the PWM controller and the emitter, and the current of the emitter decreases. When the PWM controller is at a low level, the current flowing through the emitter resistor increases, the current of the emitter increases, the capacitor is discharged, and the LC oscillation circuit starts to oscillate.

20. The axle counting wheel sensor according to claim 19, characterized in that: A control resistor is arranged between the PWM controller and the emitter resistor; and the LC oscillation circuit is connected in parallel with a collector resistor.

21. A wheel sensor as claimed in claim 1, characterized in that: The regulating circuit adopts a regulating output method based on 2 out of 3, and the regulating circuit includes: three independent sensing units, three logic AND units and one logic OR unit; each sensing unit outputs two signals, each logic AND unit receives two signals, the outputs of the three logic AND units are connected to the logic OR unit, and the logic OR unit determines whether the signals output by the three logic AND units are the same. If two of the signals are the same, an axle counting signal is output.

22. A wheel sensor as claimed in claim 21, characterized in that: The two signals come from different logic AND units respectively. The first sensing unit and the second sensing unit are connected to the first logic AND unit, the second sensing unit and the third sensing unit are connected to the second logic AND unit, the first sensing unit and the third sensing unit are connected to the third logic AND unit, the first logic AND unit, the second logic AND unit and the third logic AND unit are all connected to the input end of the logic OR unit, and the output end of the logic OR unit is connected to the axle counting host through the communication module.

23. A wheel sensor as claimed in claim 22, characterized in that: The communication module is a CAN communication module.

24. A wheel sensor as claimed in claim 23, characterized in that: The sensing unit includes a voltage-controlled oscillation circuit, a phase-detection filter circuit and an amplification comparison filter circuit. The voltage-controlled oscillation circuit is communicatively connected to the phase-detection filter circuit, and the voltage-controlled oscillation circuit and the phase-detection filter circuit are both connected to the amplification comparison filter circuit. The amplification comparison filter circuit outputs amplitude and phase signals.

25. A wheel sensor as claimed in claim 24, characterized in that: The voltage-controlled oscillation circuit comprises an LC oscillation circuit and a voltage regulating circuit. The LC oscillation circuit is connected to the voltage regulating circuit. The voltage regulating circuit changes the component parameters of the LC oscillation circuit by adjusting the voltage.

26. A wheel sensor according to any one of claims 21 to 25, characterized in that: The three logic AND units and one logic OR unit are arranged on the MCU. The MCU is connected to the axle counter host via an auxiliary circuit. The auxiliary circuit is used to reduce the output voltage of the axle counter host.

27. A wheel sensor as claimed in claim 26, characterized in that: The auxiliary circuit reduces the output voltage of the axle counter host from 24V to 5V.

28. A wheel sensor as claimed in claim 27, characterized in that: The oscillation amplitudes of the first sensing unit, the second sensing unit and the third sensing unit are consistent.

29. An axle counting system of a wheel sensor, characterized in that: A wheel sensor as described in any one of claims 1 to 28 is used, wherein the wheel sensor corresponds to a junction box one by one, and each junction box is connected to the adjacent junction boxes before and after it, and all the junction boxes along the line are cascaded and connected to the axle counting host.

30. The wheel sensor axle counting system according to claim 29, characterized in that: The wheel sensor detects the wheel rim of the train wheel and converts the detected signal from an analog signal to a digital signal. The wheel sensor is laid on the rail.

31. The wheel sensor axle counting system according to claim 30, characterized in that: The wheel sensor is provided with a CAN interface, the wheel sensor outputs a CAN signal, and the axle counting host is provided with a CAN interface corresponding to the CAN interface on the wheel sensor.

32. The wheel sensor axle counting system according to claim 31, characterized in that: A CAN bus is laid between the wheel sensor and the axle counter host, and signals are transmitted between the two using the CAN bus.

33. The wheel sensor axle counting system according to claim 32, characterized in that: The CAN bus uses twisted pair cables.

34. The wheel sensor axle counting system according to claim 32, characterized in that: The CAN bus adopts differential transmission technology.

35. The wheel sensor axle counting system according to claim 34, characterized in that: In the differential technology, the real signal received by the axle counter host is the voltage difference between CAN_H and CAN_L.

36. The wheel sensor axle counting system according to claim 32, characterized in that: The CAN bus adopts an error checking mechanism.

37. The wheel sensor axle counting system according to claim 36, characterized in that: In the error checking mechanism, each CAN frame includes a cyclic redundancy check field. If a data error is found, the receiving end will refuse to receive the data and require the sending end to resend the data.

38. The wheel sensor axle counting system according to claim 37, characterized in that: The CAN bus uses the current mode of the receiver for data communication.

39. The wheel sensor axle counting system according to claim 37, characterized in that: The wheel sensor includes two or more sensing units. The time when the wheel passes through each sensing unit is different. The wheel sensor calculates the time difference and sequence of the signals sensed by each sensing unit, determines the running speed and direction of the train, and transmits its signal to the axle counting host through the CAN bus.

40. The wheel sensor axle counting system according to claim 37, characterized in that: The wheel sensor is provided with a derailment sensing unit for detecting whether the wheel sensor is installed on the rail. When the wheel sensor is loose, derailment information is sensed, and the wheel sensor derailment signal is converted into a digital signal and transmitted to the axle counting host through the CAN bus.

41. The wheel sensor axle counting system according to claim 40, characterized in that: The wheel sensor includes a temperature sensor for measuring rail temperature changes, and the temperature monitoring signal is transmitted via the CAN bus to provide real-time temperature data and alarm information.

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