TELKOMNIKA ISSN: 1693-6930
Railway Signal Distributed Computer Control Switch Module Hualin Chen 154
railway signal equipment play an important role in the safety design of railway signal equipment. 1 Fault tree analysis method
Fault tree analysis FTA is an important safety analysis method, which can be applied to the whole design of safety related system [8]. It includes qualitative analysis and quantitative
analysis. The process of qualitative analysis is the process of identifying faults and analyzing the faults. Fault tree quantitative analysis is the task of the fault tree will be built to quantify the
quantitative analysis.
2 Module hazard control The control switch module is the key equipment to ensure the safe and efficient
operation of the train, and its security requirements are very high, so it is very important to control the risk. By reference to the international general safety standard EN50129, this section
will discuss the risk control of the switch control module through the safety analysis method, combining with the analysis and calculation. The risk control process is shown in figure 1.
Figure 1. Risk control process 3 Module THR calculation
According to the requirements of the international standard EN50129, the safety
integrity level of the safety integrity level of the switch risk of the train crash or crash accident may be 4, so we can come to the conclusion: THR
switch
≤ 10
-9
. According to experience, we assume that the maximum size of the system is about 150 sets of switches. The allowable risk
rate for each set of switch control functions is THR
each-set-points
= 6.6×10
-12
. We can assign THR once again. The THR is 4.2 ×10
-12
after the distribution of the switch, which is less than 6.6 × 10
- 12
, and meets the requirements [9].
2.3. Hardware Design of Control Switch Module
The overall structure of switch control module According to the requirements of turnout module function demand and the requirements
of switch machine interface in Section 2.2, combined with the related security technologies, we on the overall structure of the module hardware design. The hardware components of the
module mainly include the data acquisition circuit, the switch control main circuit, and the logic control circuit, the current detection circuit, the microprocessor circuit and so on [10, 11].
Among them, the signal acquisition circuit is mainly completed on the location of the switch, the back position and the four open state acquisition; Switch control main circuit is
responsible for the implementation of the operation of the switch; The driving circuit realizes the safety control of the circuit and the control of the main circuit relay; The microprocessor circuit is
responsible for the core logic operation of the whole module and the realization of the fault
ISSN: 1693-6930
TELKOMNIKA Vol. 14, No. 3A, September 2016 : 152 – 160
155 alarm function; The signal circuit realizes the safety communication function between the switch
module and the communication host computer. Main circuit of switch control module
1 Switch control main circuit Switch action circuit is mainly to complete the set operation and anti-exercise control of
four wire direct current DC switch machine. Because it is directly related to the safety of the module control, the key design and analysis of the switch action circuit should be carried out.
This paper selected the zero crossing trigger SCR type alternating current AC solid state relay, and the solid state relay that collects the signal representation of switch machine is FET device.
Considering the Fault-Safety Principle, we choose the safety plate elastic load relay for control circuits and circuit safety switch.
The circuit mainly includes switch control main circuit and current detecting circuit. Switch control main circuit to achieve the on-off control of fixed and reverse operating circuit.
Current detection circuit is mainly to control the detection of the main loop current. Combined with the software design, we need to complete the monitoring of the state of the circuit and the
fault conditions. Switch control main circuit is shown in Figure 2 below. It is mainly composed of switch DCJ, FCJ, HCJ, BHJ and the rectifier bridge D1, D2.
Figure 2. Hardware schematic diagram of switch control circuit Current detecting circuit can realize the real-time monitoring of the switch machine
operation circuit current information, and it also can complete the relay circuit component failure detection. In the main control circuit, we use the current detection circuit as the fault detector of
the switch control circuit to meet the reactive fault-safety principle. AC detection circuit mainly completes the induction of line current, and the induction current is converted to the value that
the processor can read, so as to realize the track monitoring and fault location function of the circuit. The safety supervision circuit mainly completes the supervision to the relay short circuit
and the open circuit fault, realizes the real-time monitoring of the relay status, and ensures the timely detection of the circuit fault. Signal acquisition circuit mainly completes the acquisition of
the state information of the switch and the back position, and it is mainly composed of a transformer, a resistor and a photoelectric coupler.
2 Control circuit design The control representation function of the switch control module is all based on the
microcontroller as the core. It mainly completes the interaction of information with the interlocking host information, and it is responsible for the core logic operation function of the
TELKOMNIKA ISSN: 1693-6930
Railway Signal Distributed Computer Control Switch Module Hualin Chen 156
whole module. The circuit uses redundant MCU to control the circuit. The circuit is able to move only when two MCU execute the same command, and when two MCU receive command is not
consistent or circuit failure; it needs to ensure that the switch will not miss the action. The controller area network CAN bus interface circuit is composed of 6N137 and TJA1050 devices.
Compared with other communication bus, CAN bus have outstanding performance? Because the protocol meets the design requirements of the system, we choose CAN as the
communication protocol between the module and the host. In order to improve the availability and reliability of the system, each module of the system is designed with double modules. A
switch machine safety control is completed by two modules.
2.4. Software Design of Control Switch Module
