CN105966420A - Rail wheel sensing device - Google Patents

Abstract

A rail wheel sensing device, comprising a wheel sensing unit, a first impulse interference filter unit, and a second impulse interference filtering unit, the wheel sensing unit includes two magnetic head type wheel sensors, and the output first sensing signal , The second sensing signal is automatically filtered by the first pulse interference filter unit and the second pulse interference filter unit, respectively, the positive narrow pulse during the negative wide pulse period and the negative narrow pulse interference during the positive wide pulse period, especially the continuous jitter narrow pulse interference Signal. The maximum width of the positive narrow pulse and the negative narrow pulse to be filtered can be adjusted by changing the charging time constant and the discharging time constant respectively. The rail wheel sensor device can be applied to the occasions of wheel detection and axle counting of locomotives and trains on rails.

Description

Rail Wheel Sensing Device

technical field

The invention relates to a sensing and detecting device for a rail transit vehicle, in particular to a rail wheel sensing device.

Background technique

The track surface of the track circuit is badly shunted due to the influence of bad conductors. When a train or locomotive occupies the track, the track relay that controls the track section cannot operate normally, resulting in signal interlock failure. When the axle counting sensor solution is adopted, the mechanical sensor relies on the spring to control the on-off of the electrode contacts to generate the signal of the arrival of the train, which is prone to poor contact and signal jitter interference; the infrared rays of the infrared sensor are easily blocked by dust and debris, and are easily affected. The interference of other light produces interference pulses; the ultrasonic piezoelectric transducer cannot be effectively protected because it must be exposed, and is also susceptible to interference from other obstacles such as construction workers, resulting in interference pulses; eddy current coil induction, magnetic head sensor induction It is easily affected by metal debris. For example, when railway construction personnel slide over the magnetic head sensor with a shovel, it is easy to cause interference to the magnetic head discrimination and output interference pulses. When the above-mentioned various sensors enter or exit the detection interval, due to the vibration of the sensor caused by the passing of the vehicle, the vibration of the wheel itself, and the vibration of the contact point of the sensor itself, etc., the edge of the sensor signal will also generate a jitter pulse.

Contents of the invention

In order to solve the existing problems of wheel detection and axle counting devices for locomotives and trains on rails, the present invention provides a rail wheel sensing device, which includes a wheel sensing unit, a first pulse interference filtering unit, a second Pulse interference filter unit.

The wheel sensing unit outputs a first sensing signal and a second sensing signal; the first sensing signal is sent to the pulse input end of the first pulse interference filtering unit, and the second sensing signal is sent to the second pulse interference The pulse input end of the filtering unit; the output pulse end of the first pulse interference filtering unit outputs the first axle counting signal, and the output pulse end of the second impulse interference filtering unit outputs the second axle counting signal.

The first pulse interference filtering unit and the second pulse interference filtering unit are pulse interference filtering units with the same structural parameters.

The pulse interference filter unit includes a fast discharge circuit, a fast charge circuit, a capacitor, and a Schmidt circuit; the input of the fast discharge circuit is an input pulse, and the output end is connected to the Schmidt circuit input; the fast charge circuit The input is an input pulse, and the output end is connected to the input end of the Schmidt circuit; one end of the capacitor is connected to the input end of the Schmidt circuit, and the other end is connected to the common ground or the power supply of the pulse interference filtering unit; the Schmidt The output terminal of the special circuit is the output pulse terminal.

The fast discharge circuit includes a fast discharge diode, a charging resistor, and a fast discharge switch; after the fast discharge diode is connected in parallel with the charging resistor, it is connected in series with the fast discharge switch; the fast charging circuit includes a fast charging diode, a discharging resistor, a fast charging switch; after the fast charging diode is connected in parallel with the discharge resistor, it is connected in series with the fast charging switch; the unidirectional current flow direction on the fast discharging diode is from the output terminal of the fast discharging circuit to the input terminal; the single current on the fast charging diode The direction of current flow is from the input terminal of the fast charging diode to the output terminal.

The fast discharge switch and the fast charge switch are controlled by output pulses. The specific method is that when the Schmidt circuit is an in-phase Schmidt circuit, the low level of the output pulse controls the fast discharge switch to be turned on and the fast charge switch to be turned off. The high level of the output pulse controls the fast discharge switch to turn off and the fast charge switch to turn on; when the Schmidt circuit is an inverting Schmidt circuit, the high level of the output pulse controls the fast discharge switch to turn on and the fast charge switch to turn off The low level of the output pulse controls the fast discharge switch to turn off and the fast charge switch to turn on.

The fast discharge switch and the fast charge switch are digitally controlled multi-channel analog switches, or both are level controlled bidirectional analog switches.

When the resistance value of the charging resistance and the discharging resistance is the same, the charging resistance in the fast discharging circuit and the discharging resistance in the fast charging circuit can be canceled and replaced by the charging and discharging resistance having the same resistance value as the charging resistance; the charging and discharging resistance It is connected in parallel with the input pulse end and the input end of the Schmitt circuit.

The positive narrow pulse width that can be filtered by the pulse interference filtering unit is controlled by changing the charging time constant or the upper threshold voltage of the Schmidt circuit, and the negative narrow pulse width that can be filtered is controlled by changing the discharge time constant or the lower limit of the Schmidt circuit. Threshold voltage to control.

The charging time constant is the product of charging resistance and capacitance; the discharging time constant is the product of discharging resistance and capacitance. Alternatively, both the charging time constant and the discharging time constant are the product of the charging and discharging resistance and the capacitance.

The Schmitt circuit has a high input impedance characteristic.

The beneficial effects of the present invention are: the rail wheel sensing device allows the positive pulse and negative pulse signals with a width greater than a specified value to pass through in the sensing signal output by the wheel sensing unit, and can automatically filter the positive narrow pulse during the negative wide pulse period , especially the ability to quickly restore the filtering ability to filter continuous positive and narrow pulse interference signals, and eliminate the rising edge jitter of the input pulse; it can automatically filter the negative narrow pulse during the positive wide pulse period, especially the ability to quickly restore the filtering ability to filter continuous negative narrow pulses Interference signal, eliminate the falling edge jitter of the input pulse; the maximum width of the positive narrow pulse and negative narrow pulse that needs to be filtered can be adjusted by changing the charging time constant and discharging time constant.

Description of drawings

Fig. 1 is a structural block diagram of a rail wheel sensing device embodiment;

Fig. 2 is embodiment 1 of pulse interference filtering unit;

Fig. 3 is the input pulse and the output pulse waveform of pulse interference filtering unit embodiment 1;

Fig. 4 is embodiment 2 of pulse interference filtering unit;

Fig. 5 is embodiment 3 of the pulse interference filtering unit;

Fig. 6 is the input pulse and output pulse waveform of pulse interference filter unit embodiment 3;

Fig. 7 is embodiment 4 of the pulse interference filtering unit;

Fig. 8 is embodiment 5 of the pulse interference filtering unit;

Fig. 9 is Embodiment 6 of the pulse interference filtering unit.

detailed description

The present invention will be further described below in conjunction with accompanying drawing.

As shown in FIG. 1 , it is a structural block diagram of an embodiment of a rail wheel sensing device, including a wheel sensing unit 10 , a first impulse interference filtering unit 20 , and a second impulse interference filtering unit 30 . The wheel sensing unit 10 includes two wheel sensors, which respectively output a first sensing signal M1 and a second sensing signal N1; the first sensing signal M1 is sent to the pulse input terminal P1 of the first pulse interference filtering unit, and the second The second sensing signal N1 is sent to the pulse input terminal P1 of the second pulse interference filtering unit; the output pulse terminal P2 of the first pulse interference filtering unit outputs the first axle counting signal M2, and the output pulse terminal P2 of the second pulse interference filtering unit outputs Second axle counting signal N2.

The wheel sensors included in the wheel sensing unit are various axle counting sensors such as mechanical sensors, infrared sensors, ultrasonic piezoelectric transducers, eddy current coil induction sensors, and magnetic head sensors.

The first pulse interference filtering unit and the second pulse interference filtering unit are pulse interference filtering units having the same structural parameters. The composition of the pulse interference filtering unit includes a fast discharge circuit, a fast charge circuit, a capacitor, and a Schmidt circuit.

As shown in Figure 2, Embodiment 1 of the pulse interference filtering unit is shown. In embodiment 1, the fast discharge diode, the charging resistor, and the fast discharge switch are respectively diode D11, resistor R11, and switch T11, forming a fast discharge circuit; the fast charge diode, the discharge resistor, and the fast charge switch are respectively diode D12, resistor R12, The switch T12 constitutes a fast charging circuit; the capacitor is the capacitor C11. The Schmitt circuit F11 is an in-phase Schmitt circuit, and the output pulse P2 and the input pulse P1 in Embodiment 1 are in the same phase. One end of the capacitor C11 is connected to the input end of the Schmitt circuit, that is, the input end A2 of F11, and the other end is connected to the common ground. The anode of the diode D11 is connected to the input terminal A2 of F11, and the cathode is connected in series with the switch T11 to the input pulse terminal P1. When the switch T11 is turned on, the unidirectional current of the diode D11 flows from the input terminal A2 of F11 to the input pulse terminal P1. The cathode of the diode D12 is connected to the input terminal A2 of F11, and the anode is connected in series with the switch T12 to the input pulse terminal P1. When the switch T12 is turned on, the unidirectional current of the diode D12 flows from the input pulse terminal P1 to the input terminal of F11 A2.

The fast discharge switch and the fast charge switch are two-way analog switches controlled by the level. In Embodiment 1, both switch T11 and switch T12 are bidirectional analog switches that are turned on when the control signal is high and turned off when the control signal is low. The model can be CD4066 or CD4016. In Embodiment 1, the Schmitt circuit F11 is an in-phase Schmitt circuit, the output pulse P2 (point A3 in Figure 2) is directly connected to the level control terminal of the switch T12, and the high and low levels of the output pulse P2 respectively control the switch T12 turn on and off; the output pulse P2 passes through the inverter F12 (in Fig. 2 point) is connected to the level control terminal of the switch T11, and the high and low levels of the output pulse P2 respectively control the switch T11 to be turned off and turned on. Controlled by the output pulse P2, one of the switch T11 and the switch T12 is always in the on state, and the other is in the off state.

FIG. 3 is the input pulse and output pulse waveforms of Embodiment 1 of the pulse interference filtering unit. In Figure 3, P1 is the input pulse, and P2 is the output pulse. When the low level of P1 is a normal negative width pulse, the potential of point A2 in Figure 2 is consistent with the low level potential of point A1, and P2 is low level, switch T11 On, T12 off. The high level of the positive narrow pulse 11 charges the capacitor C11 through the charging resistor R11, so that the potential of the point A2 rises; since the width of the narrow pulse 11 is smaller than the time T1, the potential of the point A2 is still lower than the Schmidt circuit F11 at the end of the narrow pulse 11 Therefore, P2 is maintained at a low level, and the switch T11 is kept on; when the narrow pulse 11 ends, the point A1 becomes low again and the capacitor C11 is quickly discharged through the fast discharge diode D11, so that the potential of the point A2 Consistent with the low-level potential of point A1, it returns to the state before the narrow pulse 11, and its anti-interference ability is quickly restored. When there is a continuous positive narrow pulse interference signal immediately behind, it can also be filtered out. The widths of positive narrow pulse 12 and positive narrow pulse 13 are both shorter than time T1, therefore, when each of narrow pulse 12 and narrow pulse 13 ends, P2 remains at low level, point A1 becomes low level again and passes The fast discharge diode D11 discharges the capacitor C11 quickly, so that the potential of point A2 is consistent with the low level potential of point A1.

Pulse 14 is a normal positive wide pulse. When P1 maintains a high level time after the rising edge 20 and reaches T1, the high level of P1 charges the capacitor C11 through the charging resistor R11, so that the potential of point A2 rises to reach the Schmidt circuit F11. The upper threshold voltage, the Schmidt circuit F11 output P2 changes from low level to high level at the rising edge 25, so that the switch T11 is turned off and T12 is turned on; the high level of point A1 passes through the fast charging diode D12 to make the capacitor C11 Fast charging, so that the potential of point A2 is consistent with the high level potential of point A1, and P2 is maintained at high level.

The low level of the negative narrow pulse 15 discharges the capacitor C11 through the discharge resistor R12, so that the potential of the point A2 drops; since the width of the narrow pulse 15 is smaller than the time T2, the potential of the point A2 is still higher than the Schmidt circuit F11 at the end of the narrow pulse 15 Therefore, P2 remains at a high level, and the switch T12 remains on; at the end of the narrow pulse 15, point A1 becomes high level again and the capacitor C11 is quickly charged through the fast charging diode D12, so that the potential of point A2 Consistent with the high-level potential of point A1, it returns to the state before the narrow pulse 15, and its anti-interference ability is quickly restored. When there is a continuous negative narrow pulse interference signal immediately behind, it can also be filtered out. The widths of negative narrow pulse 16, negative narrow pulse 17, and negative narrow pulse 18 are all less than time T2, therefore, when each of narrow pulse 16, narrow pulse 17, and narrow pulse 18 ends, P2 maintains a high level, and A1 The point becomes high level again and the capacitor C11 is quickly charged through the fast charging diode D12, so that the potential of point A2 is consistent with the high level potential of point A1.

When P1 maintains a low level time after the falling edge 21 and reaches T2, it means that P1 has a normal negative width pulse, and the low level of P1 discharges the capacitor C11 through the discharge resistor R12, so that the potential of point A2 drops to the Schmidt circuit F11 The lower limit threshold voltage of the Schmidt circuit F11 output P2 changes from high level to low level at the falling edge 26, so that the switch T11 is turned on and T12 is turned off; the low level of point A1 makes the capacitor through the fast discharge diode D11 C11 discharges quickly, so that the potential of point A2 is consistent with the low level potential of point A1, and P2 maintains a low level. The width of the negative width pulse 19 of P1 is greater than T2 , and when the time of maintaining the high level reaches T1 after the rising edge 22 of the negative width pulse 19 , P2 changes from low level to high level at the rising edge 27 .

The pulse interference filtering unit filters out the narrow pulse 11, narrow pulse 12, narrow pulse 13, narrow pulse 15, narrow pulse 16, narrow pulse 17, and narrow pulse 18 in the P1 signal, while the positive wide pulse 14 and negative wide pulse 19 It is possible to make the corresponding positive width pulse 23 and negative width pulse 24 appear in the P2 signal. The output pulse P2 is in phase with the input pulse P1, and the rising edge of the output wide pulse 23 lags behind the rising edge of the input wide pulse 14 by time T1, and the falling edge lags time T2.

Narrow pulse 11 , narrow pulse 12 , and narrow pulse 13 are positive narrow pulses, wherein narrow pulse 11 is an interference pulse, and narrow pulse 12 and narrow pulse 13 are continuous contact shaking pulses. Time T1 is the maximum positive narrow pulse width that the pulse interference filtering unit can filter. T1 is jointly affected by the charging time constant, the high-level potential of the input pulse P1 , the low-level potential of the input pulse P1 and the upper threshold voltage of the Schmitt circuit F11 . Normally, the high-level potential and low-level potential of the input pulse P1 are fixed values, therefore, the value of T1 can be adjusted by changing the charging time constant or the upper threshold voltage of the Schmidt circuit. In Fig. 2, the charging time constant is the product of the charging resistor R11 and the capacitor C11.

Narrow pulse 15, narrow pulse 16, narrow pulse 17, and narrow pulse 18 are negative narrow pulses, wherein narrow pulse 15 is an interference pulse, narrow pulse 16, narrow pulse 17, and narrow pulse 18 are continuous contact shaking pulses. Time T2 is the maximum negative narrow pulse width that the pulse interference filtering unit can filter. T2 is jointly affected by the discharge time constant, the high-level potential of the input pulse P1, the low-level potential of the input pulse P1, and the lower threshold voltage of the Schmitt circuit F11. Normally, the high-level potential and low-level potential of the input pulse P1 are fixed values, therefore, the value of T2 can be adjusted by changing the discharge time constant or the lower threshold voltage of the Schmidt circuit. In Fig. 2, the discharge time constant is the product of the discharge resistor R12 and the capacitor C11.

In Figure 2, the diode D11 is connected in parallel with the resistor R11 and then connected in series with the switch T11. The input pulse P1 first passes through the switch T11 from the point A1, then passes through the parallel circuit of the diode D11 and the resistor R11 to point A2, and discharges quickly according to the flow direction of the pulse signal. The switch is connected in series in front of the parallel circuit of the fast discharge diode and the charging resistor; the diode D12 is connected in parallel with the resistor R12 and then connected in series with the switch T12. According to the flow direction of the pulse signal, the fast charging switch is connected in series in the parallel circuit of the fast charging diode and the discharging resistor in front of. The series position of the fast discharge switch can also be placed behind the parallel circuit of the fast discharge diode and the charging resistor. Similarly, the series position of the fast charge switch can also be placed behind the parallel circuit of the fast charge diode and the discharge resistor. In addition, the end of the capacitor C11 connected to the common ground can also be reconnected to the power supply end of the pulse interference filtering unit.

In Figure 2, the Schmitt circuit F11 can also choose an inverting Schmitt circuit. At this time, the output pulse P2 is inverse to the input pulse P1, and the connection mode of the output pulse P2 and its inverse signal to control the switch T11 and the switch T12 needs to be in accordance with The high and low levels of the output pulse P2 respectively control the switch T12 to be turned off and on, and the high and low levels of the output pulse P2 respectively control the switch T11 to be turned on and off.

Figure 4 shows embodiment 2 of the pulse interference filter unit, the fast discharge diode, charging resistor, and fast discharge switch are respectively diode D21, resistor R21, and switch T21, and the fast charging diode, discharging resistor, and fast charging switch are respectively diode D22, resistor R22, switch T22, and capacitor C21. The Schmitt circuit F21 is an in-phase Schmitt circuit, the output pulse P2 (point B3 in Fig. 4) is directly connected to the level control terminal of the switch T22; the output pulse P2 passes through the inverter F22 (point B3 in Fig. 4 point) is connected to the level control terminal of the switch T21. Embodiment 2 is similar in structure to Embodiment 1 shown in FIG. 2. The difference is that one end of the capacitor C21 is connected to the input end of the Schmidt circuit, and the other end is connected to the power supply +VCC of the pulse interference filtering unit. The difference Second, according to the pulse signal flow relationship, the series position of the fast discharge switch is behind the parallel circuit of the fast discharge diode and the charging resistor, that is, the switch T21 is connected in series behind the parallel circuit of the diode D21 and the resistor R21. The working principle of embodiment 2 is the same as that of embodiment 1.

As shown in Figure 5, embodiment 3 of the pulse interference filtering unit is shown. The fast discharge diode and the charging resistor are respectively diode D31 and resistor R31, the fast charging diode and the discharging resistor are respectively diode D32 and resistor R32, and the fast discharging switch and the fast charging switch are Digitally controlled multi-channel analog switch T31, the normally open switch of T31 is a fast discharge switch, and the normally closed switch is a fast charge switch; the diode D31, resistor R31 and the normally open switch of the multi-channel analog switch T31 (C1 in Figure 5) form a fast The discharge circuit, the diode D32, the resistor R32 and the normally closed switch (C0 in Figure 5) of the multi-channel analog switch T31 form a fast charging circuit; the capacitor is the capacitor C31, and one end of the capacitor C31 is connected to the input end of the Schmitt circuit, namely F31 The input end C2, the other end is connected to the common ground. The Schmitt circuit F31 is an inverse Schmitt circuit, which requires the high level of the output pulse P2 to control the fast discharge switch to be turned on and the fast charge switch to be turned off, and the low level to control the fast discharge switch to be turned off and the fast charge switch to be turned on; In Fig. 5, the output pulse P2 (point C3 in Fig. 5) is directly connected to the digital control terminal of the multi-channel analog switch T31, and the high level of the output pulse P2 controls the normally open switch of the multi-channel analog switch T31 to be turned on and the normally closed switch to be closed. off, that is, the high level of the output pulse P2 controls the fast discharge switch to turn on and the fast charge switch to turn off; the low level of the output pulse P2 controls the normally open switch to turn off and the normally closed switch to turn on in the multi-channel analog switch T31, that is The low level of the output pulse P2 controls the fast discharge switch to be turned off and the fast charge switch to be turned on.

Digitally controlled multi-channel analog switches can choose different types of devices such as CD4051, CD4052, and CD4053. In Example 3, T31 selects the digitally controlled 2-channel analog switch CD4053.

FIG. 6 is the input pulse and output pulse waveforms of Embodiment 3 of the pulse interference filtering unit. In Figure 6, P1 is the input pulse, and P2 is the output pulse. When the low level of P1 is a normal negative width pulse, the potential of point C2 in Figure 5 is consistent with the low level potential of point C4 at the pulse input terminal, and P2 is high level , The normally open switch of T31 is turned on, and the normally closed switch is turned off. The high level of the positive narrow pulse 31 charges the capacitor C31 through the charging resistor R31, so that the potential of point C2 rises; since the width of the narrow pulse 31 is smaller than the time T1, the potential of point C2 is still lower than the Schmidt circuit F31 at the end of the narrow pulse 31 Therefore, P2 maintains a high level, and the state of T31 maintains; when the narrow pulse 31 ends, point C4 becomes low level again and the capacitor C31 is quickly discharged through the fast discharge diode D31, so that the potential of point C2 is the same as that of point C4 The low-level potentials are the same, returning to the state before the narrow pulse 31 comes, and its anti-interference ability is quickly restored. When there is a continuous positive narrow pulse interference signal, it can also be filtered out. The widths of the positive narrow pulse 32 and the positive narrow pulse 33 are all less than the time T1, therefore, when each of the narrow pulse 32 and the narrow pulse 33 ends, P2 remains at a high level, and the C4 point becomes a low level again and passes The fast discharge diode D31 discharges the capacitor C31 quickly, so that the potential of point C2 is consistent with the low level potential of point C4.

Pulse 34 is a normal positive wide pulse. When P1 maintains a high level time after the rising edge 40 and reaches T1, the high level of P1 charges the capacitor C31 through the charging resistor R31, so that the potential of point C2 rises to reach the Schmidt circuit F31. The upper threshold voltage, the Schmidt circuit F31 output P2 changes from high level to low level at the falling edge 45, so that the normally open switch of T31 is turned off and the normally closed switch is turned on; the high level of C4 passes through the fast charging diode D32 charges the capacitor C31 quickly, makes the potential of point C2 consistent with the high level potential of point C4, and maintains the low level of P2.

The low level of the negative narrow pulse 35 discharges the capacitor C31 through the discharge resistor R32, so that the potential of the point C2 drops; since the width of the narrow pulse 35 is smaller than the time T2, the potential of the point C2 is still higher than the Schmidt circuit F31 at the end of the narrow pulse 35 Therefore, P2 is maintained at a low level, and the state of T31 is maintained; at the end of the narrow pulse 35, point C4 becomes high level again and the capacitor C31 is quickly charged through the fast charging diode D32, so that the potential of point C2 is the same as that of point C4 The high-level potentials are consistent, returning to the state before the narrow pulse 31 comes, and its anti-interference ability is quickly restored. When there is a continuous negative narrow pulse interference signal, it can also be filtered out. The negative narrow pulse 36, the negative narrow pulse 37, and the negative narrow pulse 38 have a width less than the time T2. Therefore, when each of the narrow pulse 36, the narrow pulse 37, and the narrow pulse 38 ends, P2 maintains a low level, and C4 The point becomes high level again and the capacitor C31 is charged quickly through the fast charging diode D32, so that the potential of point C2 is consistent with the high level potential of point C4.

When P1 maintains a low level time after the falling edge 41 and reaches T2, it means that P1 has a normal negative width pulse, and the low level of P1 discharges the capacitor C31 through the discharge resistor R32, so that the potential of point C2 drops to the Schmidt circuit F31 The lower limit threshold voltage of the Schmidt circuit F31 output P2 changes from low level to high level at the rising edge 46, so that the normally open switch of T31 is turned on and the normally closed switch is turned off; the low level of point C4 passes through the rapid discharge The diode D31 quickly discharges the capacitor C31, so that the potential of the C2 point is consistent with the low-level potential of the C4 point, and the P2 is maintained at a high level. The width of the negative wide pulse 39 of P1 is greater than T2 , and when the high level time reaches T1 after the rising edge 42 of the negative wide pulse 39 , P2 changes from high level to low level at the falling edge 47 .

The pulse interference filter unit filters out the narrow pulse 31, narrow pulse 32, narrow pulse 33, narrow pulse 35, narrow pulse 36, narrow pulse 37, and narrow pulse 38 in the P1 signal, while the positive wide pulse 34 and negative wide pulse 39 It is possible to make the corresponding negative width pulse 43 and positive width pulse 44 appear in the P2 signal and are opposite to P1. Narrow pulse 31 , narrow pulse 32 , and narrow pulse 33 are positive narrow pulses, wherein narrow pulse 31 is an interference pulse, and narrow pulse 32 and narrow pulse 33 are continuous contact shaking pulses. Narrow pulse 35, narrow pulse 36, narrow pulse 37, and narrow pulse 38 are negative narrow pulses, wherein narrow pulse 35 is an interference pulse, and narrow pulse 36, narrow pulse 37, and narrow pulse 38 are continuous contact shaking pulses.

In Fig. 6, time T1 is the maximum positive narrow pulse width that can be filtered by the pulse interference filter unit, and the value of T1 can be adjusted by changing the charging time constant or the upper threshold voltage of the Schmidt circuit. In FIG. 5, the charging time constant is the product of the charging resistor R31 and the capacitor C31. Time T2 is the maximum negative narrow pulse width of the input that the pulse interference filtering unit can filter. The value of T2 can be adjusted by changing the discharge time constant or the lower threshold voltage of the Schmidt circuit. In FIG. 5, the discharge time constant is the product of the discharge resistor R32 and the capacitor C31.

In Fig. 5, the multi-channel analog switch T31 adopts the distributor connection method, and the input pulse P1 is controlled by the digital signal C3 to distribute to the fast discharge circuit or the fast charge circuit; the multi-channel analog switch T31 can also adopt the selector connection method, that is The input pulse P1 is sent to the fast discharge circuit and the fast charge circuit at the same time, and the signal to select the fast discharge circuit or the fast charge circuit is connected to the Schmidt circuit by digital signal control.

In FIG. 5 , the end of the capacitor C31 connected to the common ground can also be reconnected to the power supply end of the pulse interference filtering unit.

In FIG. 5 , the Schmitt circuit F31 can also be an in-phase Schmitt circuit.

Figure 7 shows embodiment 4 of the pulse interference filter unit, the fast discharge diode and the charging resistor are respectively diode D41 and resistor R41, the fast charging diode and the discharging resistor are respectively diode D42 and resistor R42, the fast discharging switch and the fast charging switch are digital Controlled multi-channel analog switch T41; the capacitor is a capacitor C41, one end of the capacitor C41 is connected to the input end of the Schmidt circuit, that is, the input end D2 of F41, and the other end is connected to the common ground. The structure of embodiment 4 is similar to that of embodiment 3, the difference is that the multi-channel analog switch T41 adopts the selector connection method, and the selector connection method and the distributor connection method have no difference in working principle; The special circuit F41 is an in-phase Schmitt circuit, the output pulse P2 is in phase with the input pulse P1, and the output pulse P2 (point D3 in Figure 7) is directly connected to the digital control terminal of the multi-channel analog switch T41, so the normally closed switch of T41 is a fast discharge The switch, the normally open switch is a fast charging switch; the diode D41, the resistor R41 and the normally closed switch (D0 in Figure 7) of the multi-channel analog switch T41 form a fast discharge circuit, and the diode D42, the resistor R42 and the normally open switch of the multi-channel analog switch T41 The switch (D1 in Figure 7) forms a fast charging circuit.

Fig. 8 shows Embodiment 5 of the pulse interference filtering unit. In Embodiment 5, the fast discharge diode and the fast discharge switch are respectively diode D51 and switch T51, forming a fast discharge circuit; the fast charge diode and the fast charge switch are respectively diode D52 and switch T52, forming a fast charge circuit; the capacitor is a capacitor C51; Schmidt circuit F51 is an inverting Schmidt circuit, therefore, in embodiment 5, the output pulse P2 is reversed with the input pulse P1, and the output pulse P2 (point E3 in Figure 8) is directly connected to the level control of the switch T51 terminal; after the output pulse P2 passes through the inverter F52 (in Fig. 8 point) is connected to the level control terminal of the switch T52.

In Embodiment 5, the charge resistor and discharge resistor connected in parallel with the fast discharge diode and the fast charge diode respectively are cancelled, and are replaced by the charge and discharge resistor R51 connected in parallel with the input pulse terminal E1 and the input terminal E2 of the Schmidt circuit. This circuit is a special case where the charging resistor and the discharging resistor are the same, which can simplify the circuit structure.

Fig. 9 shows Embodiment 6 of the pulse interference filtering unit. In Embodiment 6, the fast discharge diode is a diode D61, the fast charge diode is a diode D62, the fast discharge switch and the fast charge switch are digitally controlled multi-channel analog switches T61; the capacitor is a capacitor C61, and one end of the capacitor C61 is connected to a Schmitt circuit The input end of F61 is the input end F2 of F61, and the other end is connected to the common ground; the multi-channel analog switch T61 adopts the distributor connection method. Schmitt circuit F61 is an in-phase Schmitt circuit, the output pulse P2 is in phase with the input pulse P1, and the output pulse P2 (point F3 in Figure 9) is directly connected to the digital control terminal of the multi-channel analog switch T61, so the normally closed switch of T61 is The fast discharge switch, the normally open switch is a fast charge switch; the diode D61 and the normally closed switch of the multi-channel analog switch T41 (F0 in Figure 9) form a fast discharge circuit, and the diode D62 and the normally open switch of the multi-channel analog switch T61 (Figure 9 Middle F1) constitutes a fast charging circuit.

In Embodiment 6, the charging and discharging resistors connected in parallel with the fast-discharging diode and the fast-charging diode respectively are canceled and replaced by the charging and discharging resistor R61 connected in parallel with the input pulse terminal F4 and the Schmidt circuit input terminal F2. This circuit is also a special case where the charging resistor and the discharging resistor are the same, which can simplify the circuit structure.

The input signal of the Schmidt circuit is the voltage on the capacitor, therefore, the Schmidt circuit is required to have a high input impedance characteristic. Schmitt circuit can choose CMOS Schmitt inverter CD40106, 74HC14 with high input impedance characteristics, or choose CMOS Schmitt NAND gate CD4093, 74HC24 and other devices with high input impedance characteristics. The upper threshold voltage and lower threshold voltage of CMOS Schmitt inverter or CMOS Schmidt NAND gate are fixed values related to the device. Therefore, adjusting the positive narrow pulse width and negative narrow pulse width of the input that can be filtered requires It is performed by changing the charging time constant and the discharging time constant. Using a Schmitt inverter or a Schmitt NAND gate to form a non-inverting Schmitt circuit requires adding an inverter after the Schmitt inverter or Schmitt NAND gate.

The Schmidt circuit can also be constructed by using an operational amplifier, which can flexibly change the upper threshold voltage and the lower threshold voltage. Similarly, when an operational amplifier is used to form a Schmitt circuit, it is necessary to adopt a structure and circuit with high input impedance characteristics.

Claims (10)

1. A rail wheel sensing device, characterized in that: It includes a wheel sensing unit, a first pulse interference filtering unit, and a second pulse interference filtering unit; The wheel sensing unit outputs a first sensing signal and a second sensing signal; the first sensing signal is sent to the pulse input end of the first pulse interference filtering unit, and the second sensing signal is sent to the second pulse interference The pulse input terminal of the filter unit; The output pulse end of the first impulse interference filtering unit outputs the first axle counting signal, and the output pulse end of the second impulse interference filtering unit outputs the second axle counting signal. 2. The rail wheel sensing device according to claim 1, characterized in that: The first pulse interference filtering unit and the second pulse interference filtering unit are pulse interference filtering units with the same structural parameters; The pulse interference filtering unit includes a fast discharge circuit, a fast charge circuit, a capacitor, and a Schmidt circuit; The input of the fast discharge circuit is an input pulse, and the output end is connected to the input end of the Schmidt circuit; The input of the fast charging circuit is an input pulse, and the output end is connected to the input end of the Schmidt circuit; One end of the capacitor is connected to the input end of the Schmidt circuit, and the other end is connected to the common ground of the pulse interference filtering unit or the power supply; The output end of the Schmidt circuit is the output pulse end. 3. The rail wheel sensing device according to claim 2, characterized in that: the fast discharge circuit comprises a fast discharge diode, a charging resistor, and a fast discharge switch; after the fast discharging diode is connected in parallel with the charging resistor, it is connected with A fast discharge switch is connected in series; the fast charge circuit includes a fast charge diode, a discharge resistor, and a fast charge switch; after the fast charge diode is connected in parallel with the discharge resistor, it is connected in series with the fast charge switch; The unidirectional current flow direction of the fast discharge diode is to flow from the output end of the fast discharge circuit to the input end; the unidirectional current flow direction of the fast charge diode is to flow from the input end of the fast charge diode to the output end; The fast discharge switch and the fast charge switch are controlled by output pulses. 4. The track wheel sensing device according to claim 3, characterized in that: the specific method of said fast discharge switch and fast charge switch being controlled by output pulses is, when the Schmidt circuit is in-phase Schmitt In the circuit, the low level of the output pulse controls the fast discharge switch to turn on and the fast charge switch to turn off, and the high level of the output pulse controls the fast discharge switch to turn off and the fast charge switch to turn on; when the Schmidt circuit is inverting In the Mitte circuit, the high level of the output pulse controls the fast discharge switch to be turned on and the fast charge switch to be turned off, and the low level of the output pulse controls the fast discharge switch to be turned off and the fast charge switch to be turned on. 5. The rail wheel sensing device according to claim 3, characterized in that: the fast discharge switch and the fast charge switch are digitally controlled multi-channel analog switches, or both are level controlled bidirectional analog switches. 6. The rail wheel sensing device according to claim 3, characterized in that: when the charging resistor and the discharging resistor have the same resistance value, the charging resistor in the fast discharging circuit and the discharging resistor in the fast charging circuit can be canceled and replace it with a charging and discharging resistor whose resistance value is the same as that of the charging resistor; the charging and discharging resistor is connected in parallel to the input pulse terminal and the input terminal of the Schmidt circuit. 7. The rail wheel sensor device according to any one of claims 3-6, characterized in that: the pulse interference filtering unit can filter positive and narrow pulse widths by changing the charging time constant or the Schmidt circuit The upper threshold voltage is used for control, and the negative narrow pulse width that can be filtered is controlled by changing the discharge time constant or the lower threshold voltage of the Schmidt circuit. 8. The rail wheel sensor device according to claim 7, characterized in that: the charging time constant is the product of charging resistance and capacitance; the discharging time constant is the product of discharging resistance and capacitance. 9. The rail wheel sensor device according to claim 7, characterized in that: both the charging time constant and the discharging time constant are the product of charging and discharging resistance and capacitance. 10. The rail wheel sensing device according to claim 7, wherein the Schmidt circuit has a high input impedance characteristic.