Axle counting system signal source signal transmission and broken line detection system and method thereof

Abstract

The invention discloses an axle counting system signal source signal transmission and broken line detection system and method. The system comprises an outdoor signal source transmission assembly and an indoor host assembly. The outdoor signal source transmission assembly is connected with the indoor host assembly through a transmission line; the outdoor signal source transmission assembly is used for receiving the two paths of switching value signals and carrying out combination, amplification and boosting processing on the two paths of switching value signals to obtain a boosted voltage signal; and the indoor host assembly is used for receiving the boosted voltage signal, carrying out voltage reduction and band-pass filtering processing on the boosted voltage signal, and separating to obtain two paths of signal source signals corresponding to the two paths of switching value signals. The anti-interference performance and safety of signal transmission of the signal source of the axle counting system can be improved, in signal transmission of the signal source of the axle counting system, a method for matching the step-up transformer with the step-down transformer is proposed for the first time, the signal-to-noise ratio of transmission signals is greatly improved, and the anti-interference performance of signal transmission is enhanced.

Description

Technical Field

[0001] The present invention belongs to the technical field of rail transit, and in particular relates to a signal transmission and disconnection detection system and method for an axle counting system signal source. Background Art

[0002] The railway axle counting system consists of two parts: the indoor axle counting host and the outdoor signal source. The signal transmission between the outdoor signal source and the indoor axle counting host usually includes current loop, digital communication, on-off keying and other methods.

[0003] The current loop usually uses a DC current signal. The outdoor signal source converts the signal of the wheel sensor detection coil into a controllable DC constant current source. The change in the voltage across the wheel sensor detection coil controls the change in the output current of the DC constant current source. The current signal has a low impedance, so the signal attenuation is small, which can ensure the integrity of the signal during long-distance transmission. In addition, the current signal is less affected by external interference during transmission, has stronger anti-interference ability, and more reliable signal transmission. However, the signal transmission distance of the current loop method is limited by the circuit loop resistance. When transmitting over long distances, the circuit loop resistance must meet the requirements. However, if you want to reduce the circuit loop resistance, you must increase the cable diameter, which greatly increases the construction cost.

[0004] The digital communication method is to design a microcontroller for the outdoor signal source, encode the coil voltage signal after processing, and then transmit it to the indoor axle counter host by digital communication, usually using the CAN bus. The digital communication method can ensure the integrity and accuracy of the data in the design of the protocol, but in long-distance transmission, the signal is susceptible to interference, resulting in an increase in the packet loss rate, resulting in a delay in information transmission, and reducing the performance of the system.

[0005] Since the modulation signal of on-off keying OOK has only two levels of 0 or 1, the result of multiplication is equivalent to turning off or on the carrier frequency. Its actual meaning is that when the modulated digital signal is "1", the carrier is transmitted; when the modulated digital signal is "0", the carrier is not transmitted. This method is simple in technology and has high circuit reliability, which can meet the needs of long-distance transmission, but the anti-interference performance of this method is weak. According to public information, the transmission signal of the outdoor signal source of the axle counting system currently using this technology is relatively low, and the amplitude of the signal source output signal is normally around 1-2V. During long-distance transmission, the signal attenuation is large and it is easily interfered by the high-order harmonic components of the traction return current. When encountering long slope lines, cable aging or poor cable grounding, the component of the interference signal is very large, resulting in a very low signal-to-noise ratio of the on-off keying method, which will greatly affect the system performance. At the same time, this method also has a technical defect, that is, when the two detection systems of the wheel sensor sense the wheel at the same time, the output signal of the on-off keying method is without carrier, which is consistent with the result of cable breakage. The host in the axle counting room cannot distinguish whether the cable is broken or the wheel sensors sense the wheel at the same time, which poses a relatively large safety hazard. Summary of the invention

[0006] The purpose of the present invention is to address the above-mentioned deficiencies in the prior art and to provide an axle counting system signal source signal transmission and break detection system and method thereof, so as to solve the problem that the axle counting signal source signal transmission method has poor anti-interference ability and cannot detect transmission line breakage.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] In a first aspect, a signal transmission and disconnection detection system and method for an axle counter system signal source include an outdoor signal source transmission component and an indoor host component; the outdoor signal source transmission component and the indoor host component are connected via a transmission line;

[0009] The outdoor signal source transmission component is used to receive two switching quantity signals, and combine, amplify and boost the two switching quantity signals to obtain a boosted voltage signal;

[0010] The indoor host component is used to receive the boosted voltage signal, and perform voltage reduction and bandpass filtering on the boosted voltage signal to separate and obtain two signal source signals corresponding to the two switch quantity signals.

[0011] Furthermore, the outdoor signal source transmission component includes a voltage-controlled oscillation circuit 1, a voltage-controlled oscillation circuit 2, a signal superposition circuit, a power amplifier circuit, a transformer T1 and a step-up transformer T2;

[0012] The input end of the voltage-controlled oscillation circuit one and the input end of the voltage-controlled oscillation circuit two are respectively connected to two switching signals; the output end of the voltage-controlled oscillation circuit one and the output end of the voltage-controlled oscillation circuit two are both connected to the input end of the signal superposition circuit, and the output end of the signal superposition circuit is connected to the input end of the power amplifier circuit; the output end of the power amplifier circuit is connected to the primary winding of the transformer T1, and the secondary winding of the transformer T1 is connected to the primary winding of the step-up transformer T2; the secondary winding of the step-up transformer T2 is connected to the transmission line.

[0013] Further, the indoor host assembly includes a step-down transformer T3, a transformer T4, a band-pass filter circuit 1, a band-pass filter circuit 2, a signal processing circuit 1 and a signal processing circuit 2;

[0014] The transmission line is connected to the primary winding of the step-down transformer T3 after being coupled through capacitors C1 and C2, and the secondary winding of the step-down transformer T3 is connected to the primary winding of the transformer T4; one end of the secondary winding of the transformer T4 is grounded, and the other end is respectively connected to the input end of the band-pass filter circuit one and the input end of the band-pass filter circuit two; the output end of the band-pass filter circuit one is connected to the input end of the signal processing circuit one, and the output end of the band-pass filter circuit two is connected to the input end of the signal processing circuit two; the output end of the signal processing circuit one and the output end of the signal processing circuit two respectively output signal source signals corresponding to the switch signal.

[0015] Furthermore, the indoor host component also includes a constant current source circuit, an operational amplifier circuit and a voltage comparison circuit; the current output by the constant current source circuit is connected to one end of the resistor RL and the input end of the operational amplifier circuit via a transmission line and a secondary winding of a transformer T2 respectively; the other end of the resistor RL is grounded; and the output end of the operational amplifier circuit is connected to the voltage comparison circuit.

[0016] Furthermore, the signal superposition circuit includes an operational amplifier, which is an OP285 amplifier that uses a Butler amplifier front end. The OP285 amplifier has a slew rate of 22V / μs and a bandwidth of 9MHz.

[0017] Furthermore, the power amplifier circuit is a transformer-coupled class A power amplifier circuit.

[0018] Furthermore, the voltage comparison circuit is an in-phase hysteresis comparator, and its reference voltage Vref is 1V.

[0019] Furthermore, the constant current source circuit includes a voltage reference chip REF3320, which outputs a reference voltage of 2.048V.

[0020] In a second aspect, a method for transmitting a signal from a signal source of an axle counting system comprises the following steps:

[0021] S1, high-level switch signals CT1 and CT2 are respectively input into the voltage-controlled oscillator circuit 1 and the voltage-controlled oscillator circuit 2, and output signals U1 with a frequency of f1 and U2 with a frequency of f2 respectively;

[0022] S2, signal U1 and signal U2 enter the signal superposition circuit and are combined into a dual-frequency signal U3;

[0023] S3 and dual-frequency signal U3 drive transformer T1 through power amplifier circuit, and are coupled to the secondary winding output of transformer T1. The output signal of transformer T1 is connected to transformer T2, and the boosted voltage signal is transmitted to the indoor host assembly through the transmission line;

[0024] S4, the boosted voltage signal is coupled through capacitors C1 and C2 and then input into step-down transformer T3, and the stepped-down voltage signal is coupled and output through transformer T4;

[0025] S5, the stepped-down voltage signal is output to the first bandpass filter circuit and the second bandpass filter circuit, and a signal U4 with a frequency of f1 and a signal U5 with a frequency of f2 are respectively extracted from the stepped-down voltage signal;

[0026] S6, signal U4 and signal U5 are input to signal processing circuit 1 and signal processing circuit 2 respectively, and CT1' and CT2' signals corresponding to switch value signals CT1 and CT2 are output respectively.

[0027] In a third aspect, a method for detecting axle counter system disconnection includes the following steps:

[0028] T1: The constant current source circuit outputs a DC current, which is loaded on the side of the transmission line close to the indoor host component, flows through the transmission line and the secondary winding of the step-up transformer T2, then flows back to the indoor host component, and then passes through the sampling resistor RL to the ground, forming a current loop;

[0029] T2: The DC current output by the constant current source circuit generates a voltage drop V1 on the sampling resistor RL. The voltage signal V1 is amplified by the operational amplifier circuit to output the voltage signal V2. The voltage signal V2 is input into the voltage comparison circuit. If the voltage signal V2> the reference voltage Vref of the voltage comparison circuit, the output signal JC of the voltage comparison circuit is high level, and the transmission line is normal.

[0030] T3: The DC current output by the constant current source circuit generates a voltage drop V1 on the sampling resistor RL. The voltage signal V1 is amplified by the operational amplifier circuit to output the voltage signal V2. The voltage signal V2 is input into the voltage comparison circuit 11. If the voltage signal V2 is less than the reference voltage Vref of the voltage comparison circuit, the output signal JC of the voltage comparison circuit is a low level, and a broken line fault occurs in the transmission line.

[0031] The axle counting system signal source signal transmission and line break detection system and method provided by the present invention have the following beneficial effects:

[0032] The present invention can improve the anti-interference performance and safety of the signal transmission of the axle counting system signal source. In the signal transmission of the axle counting system signal source, a method of using a step-up transformer in conjunction with a step-down transformer is proposed for the first time, thereby greatly improving the signal-to-noise ratio of the transmission signal and enhancing the anti-interference performance of the signal transmission.

[0033] Aiming at the defect that the on-off keying method cannot detect the broken wire, the present invention proposes for the first time a method of detecting the broken wire of the transmission line by using the constant current source method, thereby improving the safety of signal transmission of the signal source of the axle counting system. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is the circuit principle block diagram of the axle counting system signal source signal transmission and wire break detection system.

[0035] Figure 2 This is the signal superposition circuit of the present invention.

[0036] Figure 3 This is the power amplifier circuit of the present invention.

[0037] Figure 4 This is the voltage comparison circuit of the present invention.

[0038] Figure 5 This is the constant current source circuit of the present invention. DETAILED DESCRIPTION

[0039] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0040] Example 1

[0041] This embodiment provides a signal transmission and disconnection detection system for the signal source of the axle counting system, a variable frequency adjustment method that can improve the anti-interference performance of the wheel sensor, and can adjust the working frequency of the sensor according to the different interference frequencies of each project, so that the wheel sensor has higher flexibility and anti-interference ability. Figure 1 , which specifically include:

[0042] An outdoor signal source transmission component and an indoor host component are connected with the outdoor signal source transmission component and the indoor host component via a transmission line.

[0043] The outdoor signal source transmission component is used to receive two switching quantity signals, and combine, amplify and boost the two switching quantity signals to obtain a boosted voltage signal, which specifically includes:

[0044] Voltage controlled oscillator circuit 1, voltage controlled oscillator circuit 2, signal superposition circuit, power amplifier circuit, transformer T1 and step-up transformer T2;

[0045] Specifically, the connection relationship between various circuits and electrical components in the outdoor signal source transmission component is as follows;

[0046] The input end of the voltage-controlled oscillation circuit one and the input end of the voltage-controlled oscillation circuit two are respectively connected to two switching signals; the output end of the voltage-controlled oscillation circuit one and the output end of the voltage-controlled oscillation circuit two are both connected to the input end of the signal superposition circuit, the output end of the signal superposition circuit is connected to the input end of the power amplifier circuit, the output end of the power amplifier circuit is connected to the primary winding of the transformer T1, the secondary winding of the transformer T1 is connected to the primary winding of the boost transformer T2, and the secondary winding of the boost transformer T2 is connected to the transmission line.

[0047] In this embodiment, CT1 and CT2 are switch signals, representing the presence or absence of a wheel. When CT1 or CT2 is at a high level, it represents that there is no wheel above the wheel sensor. When CT1 or CT2 is at a low level, it represents that there is a wheel above the wheel sensor.

[0048] Voltage controlled oscillator circuit 1;

[0049] The voltage-controlled oscillation circuit 1 converts the high and low levels of the input signal CT1 into a frequency signal. When CT1 is at a high level, the voltage-controlled oscillation circuit 1 oscillates and outputs a fixed-frequency signal U1. The signal frequency is f1, and the signal frequency f1 is 980KHz. When CT1 is at a low level, the voltage-controlled oscillation circuit 1 stops oscillating and no signal is output.

[0050] Voltage controlled oscillator circuit 2;

[0051] The voltage-controlled oscillator circuit 2 converts the high and low levels of the input signal CT2 into a frequency signal. When CT2 is at a high level, the voltage-controlled oscillator circuit 2 starts to oscillate and outputs a fixed frequency signal U2. The signal frequency is f2, and the signal frequency f2 is 1650KHz. When CT2 is at a low level, the voltage-controlled oscillator circuit 2 stops oscillating and no signal is output.

[0052] Signal superposition circuit;

[0053] refer to Figure 2The signal superposition circuit superimposes the output signals U1 and U2 of the voltage-controlled oscillator circuit 1 and the voltage-controlled oscillator circuit 2, and modulates them into a new signal U3. Signal U3 carries the frequency information of signals U1 and U2, and can achieve the purpose of transmitting signals with only one set of cables, thereby reducing construction costs. The implementation principle is to use the op amp addition circuit. The op amp uses OP285, which is a precision high-speed amplifier and uses the Butler amplifier front end. This new front-end design combines the precision and low noise performance of bipolar transistors with the speed advantage of JFET. Therefore, the amplifier has a high slew rate, low offset voltage, good noise performance and low power supply current. The slew rate is 22V / μs and the bandwidth is 9MHz, which meets the requirements of this example. The output signals U1 and U2 of the voltage-controlled oscillator circuit 1 and the voltage-controlled oscillator circuit 2 are input into the same-direction input pins of the op amp. Let R2=R3, R1=R4, then U3=U1+U2, and then output through capacitor C1 coupling. The output signal superimposes two frequency signals, namely f1 and f2, which are referred to as dual-frequency signals.

[0054] Power amplifier circuit;

[0055] refer to Figure 3 The power amplifier circuit amplifies the signal output by the signal superposition circuit to meet the requirements of the long-distance sensor. The power amplifier circuit adopts a transformer-coupled Class A power amplifier circuit and uses transformer coupling to output to the load. The load can only receive the amplified AC signal without a DC component.

[0056] Transformer T1;

[0057] The turns ratio of transformer T1 is 1:1, which can achieve signal isolation and impedance transformation, and at the same time improve the lightning protection capability of the transmission line.

[0058] Step-up transformer T2;

[0059] The turn ratio of the step-up transformer T2 is 1:10, which increases the amplitude of the output signal of the transformer T1, thereby improving the signal-to-noise ratio of the transmission signal.

[0060] The indoor host component is used to receive the boosted voltage signal, and perform voltage reduction and bandpass filtering on the boosted voltage signal to separate and obtain two signal source signals corresponding to the two switch quantity signals, which specifically includes:

[0061] Step-down transformer T3, transformer T4, band-pass filter circuit 1, band-pass filter circuit 2, signal processing circuit 1 and signal processing circuit 2; Specifically, the connection relationship between each circuit and electrical component in the indoor host assembly is as follows;

[0062] The transmission line is connected to the primary winding of the step-down transformer T3 after being coupled through capacitors C1 and C2. The secondary winding of the step-down transformer T3 is connected to the primary winding of the transformer T4. One end of the secondary winding of the transformer T4 is grounded, and the other end is respectively connected to the input end of the band-pass filter circuit 1 and the input end of the band-pass filter circuit 2. The output end of the band-pass filter circuit 1 is connected to the input end of the signal processing circuit 1, and the output end of the band-pass filter circuit 2 is connected to the input end of the signal processing circuit 2. The output end of the signal processing circuit 1 and the output end of the signal processing circuit 2 respectively output signal source signals corresponding to the switch signal.

[0063] Among them, step-down transformer T3;

[0064] The turn ratio of step-down transformer T3 is 1:1, which can achieve signal isolation and impedance transformation, and at the same time improve the lightning protection capability of the transmission line;

[0065] Transformer T4;

[0066] The turns ratio of transformer T4 is 10:1, which reduces the output signal amplitude of transformer T3 to meet the input signal range requirements of the host in the axle counting room.

[0067] Bandpass filter circuit 1;

[0068] Bandpass filter circuit 1 is a type of filter that can pass signals within a certain frequency band and block or weaken signals of other frequencies. Common bandpass filters include: Second-order bandpass filter: It is composed of a low-pass filter and a high-pass filter in cascade, which can realize the bandpass filtering function. Resonant bandpass filter: It is composed of inductance and capacitance, which can realize the passage of signals at the resonant frequency and block or weaken signals of other frequencies. SAW bandpass filter: It uses the resonance of surface acoustic waves in the resonator to realize the passage of signals within a certain frequency range. BAW bandpass filter: It uses the resonance of piezoelectric ceramic materials to realize the passage of signals within a certain frequency range. Microstrip bandpass filter: It uses microstrip lines and resonator structures to realize the passage of signals within a certain frequency range. Ceramic filter: It is made of ceramic materials, has a simple structure and small size, and can realize the bandpass filtering function. This example uses a Butterworth bandpass filter with a center frequency of f1=980KHz and a stopband attenuation of 30db. The signal with a frequency of f1 in the transmission signal can be separated, and its corresponding voltage-controlled oscillation circuit 1 outputs a signal with a frequency of f1.

[0069] Bandpass filter circuit 2;

[0070] Bandpass filter circuit 2 is a type of filter that can pass signals within a certain frequency band and block or weaken signals of other frequencies. This example uses a Butterworth bandpass filter with a center frequency of f1=1650KHz and a stopband attenuation of 30db. The signal with a frequency of f2 can be separated from the transmission signal, and its corresponding voltage-controlled oscillator circuit 1 outputs a signal with a frequency of f2.

[0071] Signal processing circuit 1;

[0072] The signal processing circuit 1 is composed of an amplifier circuit, a rectifier circuit, a filter circuit and a voltage comparison circuit, which can convert a signal with a frequency of f1 into a high and low level CT1', which corresponds to the signal source signal CT1. Since the signal amplitude output by the bandpass filter circuit 1 is low, it is first amplified by the in-phase proportional circuit, and then converted into a pulsating DC by a small signal precision rectifier current. The pulsating DC is converted into a smooth DC signal by a filter circuit. The DC signal range is DC3-5V, and then sent to the voltage comparison circuit. The voltage comparison circuit uses an in-phase hysteresis comparator, also known as an in-phase Schmitt trigger, which is a special voltage comparator. By introducing a positive feedback mechanism, its output signal has a certain hysteresis when the input signal changes, thereby playing a role in eliminating noise, stabilizing signals and eliminating jitter in signal processing. In the in-phase hysteresis comparator, there are two important threshold voltages: a high threshold voltage (Uh) and a low threshold voltage (Ul). When the input voltage rises from low level to high level, the output signal flips to high level after the input voltage exceeds the high threshold voltage; when the input voltage drops from high level to low level, the output signal flips to low level after the input voltage falls below the low threshold voltage. The difference between these two threshold voltages is called hysteresis width (AU), which determines the anti-interference ability of the circuit. Since the DC signal range is DC3-5V, the reference voltage of the in-phase hysteresis comparator is set to 2V. The reference voltage is divided by resistors and impedance transformed by the op amp follower to improve the stability of the reference voltage.

[0073] Signal processing circuit 2;

[0074] The signal processing circuit 2 is composed of an amplifier circuit, a rectifier circuit, a filter circuit and a voltage comparison circuit, which can convert the signal with a frequency of f1 into a high and low level CT2', which corresponds to the signal source signal CT2. Since the signal amplitude output by the bandpass filter circuit 2 is low, it is first amplified by the in-phase proportional circuit, and then converted into a pulsating DC by the small signal precision rectifier current. The pulsating DC is converted into a smooth DC signal by the filter circuit. The DC signal range is DC3-5V. The reference voltage of the in-phase hysteresis comparator is set to 2V. The reference voltage is formed by resistor voltage division and impedance transformation is performed by the operational amplifier follower to improve the stability of the reference voltage.

[0075] The indoor host component of this embodiment also includes a constant current source circuit, an operational amplifier circuit and a voltage comparison circuit for detecting a broken transmission line; the current output by the constant current source circuit is connected to one end of the resistor RL and the input end of the operational amplifier circuit via the transmission line and the secondary winding of the transformer T2 respectively; the other end of the resistor RL is grounded; the output end of the operational amplifier circuit is connected to the voltage comparison circuit.

[0076] Specific;

[0077] Constant current source circuit;

[0078] The constant current source circuit can maintain a stable current output under different load conditions. The present invention uses the transmission line as the load of the constant current source and uses the constant current source current characteristic to determine whether the transmission line is broken. Figure 5 , U2 is a voltage reference chip, its model is REF3320, it outputs a reference voltage of 2.048V, and is decoupled by a capacitor. The resistor RL represents the resistance of the transmission circuit. When R1 / R2=R3 / R4, the output current I=Vef / R5, Vef is the output voltage of REF3320, that is, Vef=2.048V, when R5=1kΩ, the output current I=2.048V / 1000Ω=2.048mA, at this time the maximum circuit load is 4.9kΩ.

[0079] Operational amplifier circuit;

[0080] The operational amplifier circuit amplifies the voltage drop on the sampling resistor R1. The current output by the constant current source circuit reaches the ground through the transmission line, the secondary winding of the transformer T2 and the resistor R1. The current generates a voltage drop V1 on the resistor R1, making R1 = 200Ω, then V1 = 200*0.0002048 = 409.6mV, which is amplified 4 times by the operational amplifier circuit to output 1.638V.

[0081] Voltage comparison circuit;

[0082] The voltage comparison circuit compares the signal processed by the operational amplifier circuit with a fixed voltage threshold. When the signal is higher than the voltage threshold, it indicates that the cable is normal, and when the signal is lower than the voltage threshold, it indicates that the cable is broken. The voltage comparison circuit uses a common-phase hysteresis comparator. Since the DC signal range is DC1.638V, the reference voltage of the common-phase hysteresis comparator is set to 1V. The reference voltage is divided by a resistor and impedance transformed by an operational amplifier follower to improve the stability of the reference voltage.

[0083] The working principle of signal transmission of the signal source in this embodiment is:

[0084] When CT1 / CT2 is at a high level, the voltage-controlled oscillation circuit 1 and the voltage-controlled oscillation circuit 2 output carrier signals. At this time, the carrier signal frequency of the voltage-controlled oscillation circuit 1 is f1, and the carrier signal frequency of the voltage-controlled oscillation circuit 2 is f2. After these two carrier signals of different frequencies enter the signal superposition circuit, they are combined into a dual-frequency signal, and then drive the transformer T1 through the power amplifier circuit. After the transformer T1 is coupled to the secondary winding output, the output signal of the transformer T1 is connected to the step-up transformer T2. Since the step-up transformer T2 is a step-up transformer with a turns ratio of 1:10, the secondary winding voltage of the step-up transformer T2 is 10 times the primary winding voltage. The boosted voltage signal is transmitted through the transmission line to the indoor host and is transmitted through the capacitor C 1 and C2 are coupled and input into transformer T3, and transformer T3 is a step-down transformer with a turns ratio of 10:1. After stepping down, the secondary winding voltage of step-down transformer T3 is 0.1 times of the primary winding voltage. The stepped-down voltage signal is coupled to band-pass filter circuit 1 and band-pass filter circuit 2 through transformer T4. Band-pass filter circuit 1 extracts the signal with frequency f1 in the voltage signal, and band-pass filter circuit 2 extracts the signal with frequency f2 in the voltage signal. After signal processing circuit 1 and signal processing circuit 2, CT1' and CT2' signals are output. CT1' and CT2' are both high and low levels. CT1' corresponds to CT1, and CT2' corresponds to CT2, thereby realizing the transmission of signal source signal.

[0085] The working principle of disconnection detection in this embodiment is as follows:

[0086] The constant current source circuit of the indoor host component outputs a 2.048mA DC current, which is loaded on the indoor side of the transmission line, flows through the transmission line and the secondary winding of the step-up transformer T2, flows back to the indoor axle counter host, and then passes through the sampling resistor RL to the ground, forming a current loop. Since the current loop is a DC constant current, the loop resistance of the transmission line and the secondary winding resistance of the transformer T2 can be ignored. The capacitors C1 and C2 are designed in series at the port where the transmission line inputs the indoor host, which can block the current from flowing through the primary winding of the transformer T3.

[0087] If the transmission line is normal, the DC current output by the constant current source circuit will generate a voltage drop on the sampling resistor RL, which is recorded as V1. Since RL = 200Ω, V1 = 200*0.0002048 = 409.6mV, and the operational amplifier circuit amplifies the output voltage V2 by 4 times, V2 = 4*409.6mV = 1.638V, and then the voltage signal V2 is input to the voltage comparison circuit for processing. The voltage comparison circuit is a common-phase hysteresis comparator, and the reference voltage Vref is set to 1V. At this time, the signal voltage V2> Vref, so the voltage comparison circuit output signal JC is high, indicating that the transmission line is normal.

[0088] If a disconnection occurs in the transmission line, the DC current output by the constant current source circuit generates a voltage drop V1=0V on the sampling resistor RL, which is amplified by 4 times by the operational amplifier circuit to output a voltage V2=4*V1=0V, and then the voltage signal V2 is input to the voltage comparison circuit for processing. The voltage comparison circuit is a common-phase hysteresis comparator, and the reference voltage Vref is set to 1V. At this time, the signal voltage V2<Vref, so the output signal JC of the voltage comparison circuit is a low level, indicating that a disconnection occurs in the transmission line.

[0089] Example 2

[0090] This embodiment provides a method for transmitting a signal source of an axle counting system based on the signal transmission and disconnection detection system of the axle counting system signal source in Embodiment 1, including the following steps:

[0091] S1, high-level switch signals CT1 and CT2 are respectively input into the voltage-controlled oscillator circuit 1 and the voltage-controlled oscillator circuit 2, and output signals U1 with a frequency of f1 and U2 with a frequency of f2 respectively;

[0092] S2, signal U1 and signal U2 enter the signal superposition circuit and are combined into a dual-frequency signal U3;

[0093] S3 and dual-frequency signal U3 drive transformer T1 through power amplifier circuit, and are coupled to the secondary winding output of transformer T1. The output signal of transformer T1 is connected to transformer T2, and the boosted voltage signal is transmitted to the indoor host assembly through the transmission line;

[0094] S4, the boosted voltage signal is coupled through capacitors C1 and C2 and then input into step-down transformer T3, and the stepped-down voltage signal is coupled and output through transformer T4;

[0095] S5, the stepped-down voltage signal is output to the first bandpass filter circuit and the second bandpass filter circuit, and a signal U4 with a frequency of f1 and a signal U5 with a frequency of f2 are respectively extracted from the stepped-down voltage signal;

[0096] S6, signal U4 and signal U5 are input to signal processing circuit 1 and signal processing circuit 2 respectively, and CT1' and CT2' signals corresponding to switch signals CT1 and CT2 are output respectively, thereby realizing the transmission of signal source signals.

[0097] Example 3

[0098] This embodiment provides a method for detecting axle counting system disconnection based on the signal source signal transmission and disconnection detection system of the axle counting system in Embodiment 1, including the following steps:

[0099] T1: The constant current source circuit outputs a 2.048mA DC current, which is loaded on the transmission line near the indoor host component side, flows through the transmission line and the secondary winding of the step-up transformer T2, flows back to the indoor host component, and then flows to the ground after passing through the sampling resistor RL, forming a current loop; since the current loop is a DC constant current, the loop resistance of the transmission line and the secondary winding resistance of the transformer T2 can be ignored. The capacitors C1 and C2 are designed in series at the port where the transmission line inputs the indoor host, which can block the current from flowing through the primary winding of the transformer T3;

[0100] T2: The DC current output by the constant current source circuit generates a voltage drop V1 on the sampling resistor RL. Since RL = 200Ω, V1 = 200*0.0002048 = 409.6mV.

[0101] The voltage signal V1 is amplified by the operational amplifier circuit to output the voltage signal V2, V2 = 4 * 409.6mV = 1.638V;

[0102] The voltage signal V2 is input into the voltage comparison circuit. If the voltage signal V2> the reference voltage Vref of the voltage comparison circuit, the output signal JC of the voltage comparison circuit is high level, and the transmission line is normal.

[0103] T3: The DC current output by the constant current source circuit generates a voltage drop V1 on the sampling resistor RL, V1 = 0V;

[0104] The voltage signal V1 is amplified by the operational amplifier circuit to output the voltage signal V2, V2 = 4*V1 = 0V;

[0105] The voltage signal V2 is input to the voltage comparison circuit 11. If the voltage signal V2 is less than the reference voltage Vref of the voltage comparison circuit, the output signal JC of the voltage comparison circuit is a low level, and a transmission line disconnection fault occurs.

[0106] Although the specific implementation of the invention is described in detail in conjunction with the drawings, it should not be understood as limiting the scope of protection of this patent. Within the scope described in the claims, various modifications and variations that can be made by those skilled in the art without creative work still fall within the scope of protection of this patent.

Claims

1. A signal transmission and disconnection detection system for axle counting system signal source, characterized in that: It includes an outdoor signal source transmission component and an indoor host component; the outdoor signal source transmission component and the indoor host component are connected via a transmission line; The outdoor signal source transmission component is used to receive two switching quantity signals, and combine, amplify and boost the two switching quantity signals to obtain a boosted voltage signal; The indoor host component is used to receive the boosted voltage signal, and perform voltage reduction and bandpass filtering on the boosted voltage signal to separate and obtain two signal source signals corresponding to the two switch quantity signals.

2. The axle counting system signal source signal transmission and wire breakage detection system according to claim 1, characterized in that: The outdoor signal source transmission component includes a voltage-controlled oscillation circuit 1, a voltage-controlled oscillation circuit 2, a signal superposition circuit, a power amplifier circuit, a transformer T1 and a step-up transformer T2; The input end of the voltage-controlled oscillation circuit one and the input end of the voltage-controlled oscillation circuit two are respectively connected to two switching signals; the output end of the voltage-controlled oscillation circuit one and the output end of the voltage-controlled oscillation circuit two are both connected to the input end of the signal superposition circuit, and the output end of the signal superposition circuit is connected to the input end of the power amplifier circuit; the output end of the power amplifier circuit is connected to the primary winding of the transformer T1, and the secondary winding of the transformer T1 is connected to the primary winding of the step-up transformer T2; the secondary winding of the step-up transformer T2 is connected to the transmission line.

3. The axle counting system signal source signal transmission and disconnection detection system according to claim 1, characterized in that: The indoor host assembly includes a step-down transformer T3, a transformer T4, a band-pass filter circuit 1, a band-pass filter circuit 2, a signal processing circuit 1 and a signal processing circuit 2; The transmission line is connected to the primary winding of the step-down transformer T3 after being coupled through capacitors C1 and C2, and the secondary winding of the step-down transformer T3 is connected to the primary winding of the transformer T4; one end of the secondary winding of the transformer T4 is grounded, and the other end is respectively connected to the input end of the band-pass filter circuit one and the input end of the band-pass filter circuit two; the output end of the band-pass filter circuit one is connected to the input end of the signal processing circuit one, and the output end of the band-pass filter circuit two is connected to the input end of the signal processing circuit two; the output end of the signal processing circuit one and the output end of the signal processing circuit two respectively output signal source signals corresponding to the switch signal.

4. The axle counting system signal source signal transmission and wire breakage detection system according to claim 3, characterized in that: The indoor host component also includes a constant current source circuit, an operational amplifier circuit and a voltage comparison circuit; the current output by the constant current source circuit is connected to one end of the resistor RL and the input end of the operational amplifier circuit via a transmission line and a secondary winding of a transformer T2 respectively; the other end of the resistor RL is grounded; and the output end of the operational amplifier circuit is connected to the voltage comparison circuit.

5. The axle counting system signal source signal transmission and wire breakage detection system according to claim 2, characterized in that: The signal superposition circuit includes an operational amplifier, which is an OP285 amplifier that uses a Butler amplifier front end. The OP285 amplifier has a slew rate of 22V / μs and a bandwidth of 9MHz.

6. The axle counting system signal source signal transmission and wire breakage detection system according to claim 2, characterized in that: The power amplifier circuit is a transformer coupled class A power amplifier circuit.

7. The axle counting system signal source signal transmission and wire breakage detection system according to claim 4, characterized in that: The voltage comparison circuit is a non-inverting hysteresis comparator, and its reference voltage Vref is 1V.

8. The axle counting system signal source signal transmission and wire breakage detection system according to claim 4, characterized in that: The constant current source circuit includes a voltage reference chip REF3320, which outputs a reference voltage of 2.048V.

9. A signal source signal transmission method for an axle counting system and a wire breakage detection system according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1, high-level switch signals CT1 and CT2 are respectively input into the voltage-controlled oscillator circuit 1 and the voltage-controlled oscillator circuit 2, and output signals U1 with a frequency of f1 and U2 with a frequency of f2 respectively; S2, signal U1 and signal U2 enter the signal superposition circuit and are combined into a dual-frequency signal U3; S3 and dual-frequency signal U3 drive transformer T1 through power amplifier circuit, and are coupled to the secondary winding output of transformer T1. The output signal of transformer T1 is connected to transformer T2, and the boosted voltage signal is transmitted to the indoor host assembly through the transmission line; S4, the boosted voltage signal is coupled through capacitors C1 and C2 and then input into step-down transformer T3, and the stepped-down voltage signal is coupled and output through transformer T4; S5, the stepped-down voltage signal is output to the first bandpass filter circuit and the second bandpass filter circuit, and a signal U4 with a frequency of f1 and a signal U5 with a frequency of f2 are respectively extracted from the stepped-down voltage signal; S6, signal U4 and signal U5 are input to signal processing circuit 1 and signal processing circuit 2 respectively, and CT1' and CT2' signals corresponding to switch value signals CT1 and CT2 are output respectively.

10. A wire breakage detection method for a signal transmission and wire breakage detection system of an axle counting system according to any one of claims 1 to 8, characterized in that: The following steps are involved: T1: The constant current source circuit outputs a DC current, which is loaded on the side of the transmission line close to the indoor host component, flows through the transmission line and the secondary winding of the step-up transformer T2, then flows back to the indoor host component, and then passes through the sampling resistor RL to the ground, forming a current loop; T2: The DC current output by the constant current source circuit generates a voltage drop V1 on the sampling resistor RL. The voltage signal V1 is amplified by the operational amplifier circuit to output the voltage signal V2. The voltage signal V2 is input into the voltage comparison circuit. If the voltage signal V2> the reference voltage Vref of the voltage comparison circuit, the output signal JC of the voltage comparison circuit is high level, and the transmission line is normal. T3: The DC current output by the constant current source circuit generates a voltage drop V1 on the sampling resistor RL. The voltage signal V1 is amplified by the operational amplifier circuit to output the voltage signal V2. The voltage signal V2 is input into the voltage comparison circuit 11. If the voltage signal V2 is less than the reference voltage Vref of the voltage comparison circuit, the output signal JC of the voltage comparison circuit is a low level, and a broken line fault occurs in the transmission line.

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