Current mode speed sensor acquisition safety circuit

Abstract

The application discloses a current mode speed sensor acquisition safety circuit, and relates to the technical field of rail transit. The current mode speed sensor acquisition safety circuit comprises a signal ATP speed acquisition circuit adopting a two-by-two voting architecture. The signal ATP speed acquisition circuit comprises an A system and a B system. The A system and the B system each comprise two CPUs. Each CPU is provided with four independent acquisition circuits. The four acquisition circuits of each CPU respectively acquire two speed sensor channel signals of two speed sensors. The signal ATP speed acquisition circuit can match a current mode speed sensor based on a Hall principle. Each group of acquisition circuits only occupies two channels of the speed sensor to realize speed and direction acquisition. Two speed sensors constitute two-by-two redundancy. The acquisition circuits of the two systems are completely independent. Acquisition and self-checking are not affected by the other system, and self-checking does not affect the speed sensor signals.

Description

Technical Field

[0001] This invention relates to the field of rail transit technology, and in particular to a safety circuit for acquiring data using a current-type speed sensor. Background Technology

[0002] Traditional vehicles have separate speed sensors for their signaling and braking systems, which takes up a significant amount of wiring space. Furthermore, different speed sensors cannot fully guarantee real-time performance and signal consistency. Since the safety integrity level requirement for the ATP (Automatic Train Protection) signaling system is SIL4, the speed sensor board must also meet SIL4 design requirements. Therefore, the safety acquisition circuit must have multiple independent acquisition units.

[0003] Traditional signal speed acquisition schemes are mostly based on pressure source schemes because pressure source speed sensors have a large number of channels and can be connected in parallel to meet the requirements of multiple acquisitions from the same source in signal safety circuits. Therefore, signal systems rarely involve current-type speed sensor acquisition schemes. Thus, this invention proposes a current-type speed sensor acquisition safety circuit. Summary of the Invention

[0004] This invention provides a current-type speed sensor acquisition safety circuit to solve the problems existing in the prior art.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A current-type speed sensor acquisition safety circuit includes a signal ATP speed acquisition circuit with a two-to-two architecture. The signal ATP speed acquisition circuit includes an A-series and a B-series. Each A-series and B-series includes two CPUs. Each CPU is equipped with four independent acquisition circuits. The four acquisition circuits of each CPU acquire the channel signals corresponding to the two speed sensors respectively.

[0007] Preferably, each speed sensor channel signal is electrically connected with a first sampling detection circuit and a second sampling detection circuit in parallel. The first sampling detection circuit includes the acquisition circuits in the two CPUs of system A that acquire the channel signal, and the second sampling detection circuit includes the acquisition circuits in the two CPUs of system B that acquire the channel signal.

[0008] Preferably, the sampling circuits of two CPUs in the same system that are used to acquire signals from the same channel share the same sampling resistor.

[0009] Preferably, an amplifier circuit is electrically connected across the two ends of the sampling resistor, and the amplifier circuit is electrically connected to a pulse detection circuit.

[0010] Preferably, the pulse detection circuit includes two hysteresis comparator circuits for signal comparison and disconnection comparison, respectively.

[0011] Preferably, the hysteresis comparator circuit for signal comparison compares the voltage after the input current of the speed sensor is shaped during normal operation with two upper and lower voltage limits to obtain the voltage PWM. The comparison principle is that if the voltage is higher than the upper limit, the output is high, and if it is lower than the lower limit, the output is low.

[0012] Preferably, the hysteresis comparator circuit for disconnection comparison compares the voltage after the input current of the speed sensor is shaped after disconnection with two upper and lower voltage limits to obtain the voltage PWM. The comparison principle is that if the voltage is higher than the upper limit, the output is high, and if it is lower than the lower limit, the output is low.

[0013] Preferably, the parallel connection point of the first sampling detection circuit and the second sampling detection circuit is provided with a two-to-one switch, which selects between the channel signal and the self-test circuit.

[0014] Preferably, after the two 2-to-1 switches are powered on, they default to the self-test circuit. The self-test circuit includes two injection-type constant current sources, which can simulate external high current and low current injection scenarios and inject into the same system sampling and detection circuit. If the power-on self-test of both systems passes, the 2-to-1 switch of the first sampling and detection circuit is directed to the speed sensor channel signal, and the 2-to-1 switch of the second sampling and detection circuit is directed to the self-test circuit.

[0015] Preferably, the two channel signals are a rate signal and a direction signal, respectively.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] 1. The signal ATP velocity acquisition circuit proposed in this invention can be matched with a current-type velocity sensor based on the Hall principle. Each acquisition circuit occupies only two channels of the velocity sensor, and the two velocity sensors form a two-fold redundancy to realize the acquisition of velocity and direction.

[0018] 2. The two acquisition circuits are completely independent, and the acquisition and self-test are not affected by the other system, and the self-test does not affect the speed sensor channel signal;

[0019] 3. The present invention adds a two-to-one switching circuit to the parallel connection point of the two sampling and detection circuits to solve the problem that the failure of one system sampling affects the sampling results of the other system. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the two-out-of-two topology for signal ATP velocity acquisition in this invention;

[0021] Figure 2 This invention relates to a series-parallel sampling and detection circuit. Detailed Implementation

[0022] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. The described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] like Figures 1 to 2 As shown in the figure, an embodiment of the present invention provides a current-type speed sensor acquisition safety circuit, including a signal ATP speed acquisition circuit with a 2x2-out-of-2 architecture. The signal ATP speed acquisition circuit includes an A-series and a B-series, each including two CPUs. Each CPU is equipped with four independent acquisition circuits, and each CPU's four acquisition circuits acquire signals from two speed sensor channels of the two speed sensors respectively. The speed sensors are current-type speed sensors. The two channel signals are the rate signal and the direction signal, respectively. The 2x2-out-of-2 redundancy design ensures that if a single speed sensor or acquisition circuit fails, the other speed sensors and acquisition circuits can still operate normally, improving overall safety. Data from multiple acquisition circuits can be cross-validated, thereby improving the accuracy of the acquisition.

[0024] like Figure 2 As shown, each speed sensor channel signal is electrically connected to a first sampling detection circuit and a second sampling detection circuit in parallel, and a two-to-one switch is set at each parallel connection point. The first sampling detection circuit includes the acquisition circuits of the two CPUs in system A that acquire the channel signal, and the second sampling detection circuit includes the acquisition circuits of the two CPUs in system B that acquire the channel signal. The sampling circuits of the two CPUs in the same system that acquire the same channel signal share the same sampling resistor. In this invention, "same system" refers to either the first sampling detection circuit or the second sampling detection circuit, and "two systems" refers to the A-system acquisition circuit and the second sampling detection circuit.

[0025] The Hall effect current sensor outputs high and low current pulse signals. The maximum high current is approximately 17mA, and the minimum low current is approximately 5mA. The output load capacity is 450 ohms, meaning that at full power output, it can generate a signal waveform with a high level of approximately 8V and a low level of 2.25V, with a power of 0.13W. Therefore, in a fully series topology, each acquisition circuit can obtain a high level of 2V, a low level of 0.56V, and a disconnect voltage of 0V. Since the absolute values ​​of these three voltages are very close, the dynamic acquisition range is narrow. An amplifier circuit must be added to amplify the signal amplitude to facilitate the operation of the subsequent pulse detection circuit.

[0026] Therefore, an amplifier circuit is electrically connected across the sampling resistor, and the amplifier circuit is electrically connected to a pulse detection circuit.

[0027] Because of the added amplification circuit, the detection circuit had to be redesigned to cover all failure modes, including the amplification circuit itself. Furthermore, current-type signals cannot achieve the same level of circuit simplicity and injection homogeneity as voltage-type signals. Additionally, care must be taken to ensure that the current-type signal detection circuit does not interfere with the normal speed sensor signal. The amplification circuit uses a current-sensing amplifier to amplify the sampled resistor (…). Figure 2 The voltage drop across R2 is amplified to the detection range of the back end by a certain proportion.

[0028] The pulse detection circuit is a hysteresis comparator circuit, setting two comparison voltages to shape the amplified input voltage PWM waveform into a PWM that can be acquired by the back-end CPU. This invention incorporates two types of hysteresis comparator circuits: one for signal comparison, which performs a hysteresis comparison on the voltage after shaping the input current when the speed sensor is operating normally, such as setting the upper limit of the high level to 3.3V and the lower limit of the low level to 2.6V; and the other for disconnection comparison, which performs a hysteresis comparison on the voltage after shaping the input current when the speed sensor is disconnected, such as setting the upper limit of the high level to 1.2V and the lower limit of the low level to 1.0V. The high and low level settings are related to R1 and R2, aiming to ensure the operational amplifier operates within a suitable amplification range, and that an appropriate hysteresis voltage can filter out jitter that occurs in actual situations. (The hysteresis voltage refers to the upper limit of the high level minus the lower limit of the low level set by the hysteresis comparator). The principle of hysteresis comparison is to obtain the voltage PWM by comparing the input voltage with the two upper and lower voltage limits respectively. The comparison principle is that if the voltage is higher than the upper limit, the output is high; if it is lower than the lower limit, the output is low.

[0029] Based on the above reasons, in order to improve the dynamic range of the speed sensor signal acquisition and to prevent both systems from becoming unusable due to the failure of a single resistor short circuit, the following design is further proposed:

[0030] The two-way switch directs the user between the self-test circuit and the speed sensor channel signal. Upon power-up, the switch defaults to the self-test circuit side, which includes two injection-type constant current sources (the constant current source circuit is conventional) designed to simulate external high and low current values ​​(12mA and 5mA).

[0031] The self-test circuit signal simulates the injection scenarios of external high and low currents. Like the current of the speed sensor channel signal, it flows through the hysteresis comparator circuit in the subsequent stage to form a PWM waveform. The switching period between high and low currents can be set. This self-test process has covered the continuity detection of the self-test side contacts, that is, there is no PWM waveform at the back end when the wire is disconnected.

[0032] If both systems pass the power-on self-test, the system will default to operating in system A, meaning the two-way switch in system A will guide the speed sensor channel signal side, while the two-way switch in system B will guide the self-test circuit side.

[0033] When the two-way switch in the same department malfunctions, and there is a situation where the self-test circuit signal and the speed sensor channel signal input are present at the same time, the CPU of the department can identify this type of fault and stop the constant current source injection of the department.

[0034] When the two-way switch malfunctions and causes both systems to operate in the speed sensor channel signal input state, the sampling circuit is connected in parallel. The subsequent pulse detection circuit is not faulty and can still distinguish the PWM waveform and calculate the speed value, but the CPU will detect and record the fault.

[0035] The two-way selector switch is equipped with a relay position detection system, which can provide feedback on the actual position of the two-way selector switch. By default, the relay directs the two-way selector switch to the self-test circuit side.

[0036] Figure 2 The demonstration shows the acquisition scheme for a single channel of the speed sensor; the acquisition scheme for each external speed sensor channel is the same.

[0037] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit and essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0038] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A safety circuit for acquiring data using a current-type speed sensor, characterized in that, The system includes a signal ATP velocity acquisition circuit employing a 2x2-out-of-2 architecture. This circuit comprises two systems, A and B, each containing two CPUs. Each CPU has four independent acquisition circuits, which acquire signals from two corresponding velocity sensors. Each velocity sensor channel signal is electrically connected to a first sampling detection circuit and a second sampling detection circuit connected in parallel. The first sampling detection circuit includes the acquisition circuits from the two CPUs in system A that acquire the signal for that channel, and the second sampling detection circuit includes the acquisition circuits from the two CPUs in system B that acquire the signal for that channel. The sampling circuits from the two CPUs in the same system that acquire the same channel signal share the same sampling resistor. The sampling resistor is electrically connected to an amplifier circuit, which is electrically connected to a pulse detection circuit. The pulse detection circuit includes two hysteresis comparator circuits for signal comparison and disconnection comparison, respectively. A two-way switch is provided at the parallel connection point of the first and second sampling detection circuits. The two-way switch selects between the channel signal and the self-test circuit. Upon power-up, both two-way switches default to the self-test circuit. The self-test circuit includes two injection-type constant current sources, which can simulate external high-current and low-current injection scenarios, injecting into the same-system sampling detection circuit. If both systems pass the power-up self-test, the two-way switch of the first sampling detection circuit directs to the speed sensor channel signal, and the two-way switch of the second sampling detection circuit directs to the self-test circuit.

2. The current-type speed sensor acquisition safety circuit as described in claim 1, characterized in that, The hysteresis comparator circuit for signal comparison compares the voltage after the input current of the speed sensor is shaped when it is working normally with two upper and lower voltage limits to obtain the voltage PWM. The comparison principle is that if the voltage is higher than the upper limit, the output is high, and if it is lower than the lower limit, the output is low.

3. The current-type speed sensor acquisition safety circuit as described in claim 2, characterized in that, The hysteresis comparator circuit for disconnection comparison compares the voltage after the input current of the speed sensor is shaped after disconnection with two upper and lower voltage limits to obtain the voltage PWM. The comparison principle is that if the voltage is higher than the upper limit, the output is high, and if it is lower than the lower limit, the output is low.

4. The current-type speed sensor acquisition safety circuit as described in claim 1, characterized in that, The two channel signals are the rate signal and the direction signal, respectively.

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