ISSN: 1693-6930
TELKOMNIKA Vol. 14, No. 3A, September 2016 : 152 – 160
153 following characteristics [4]: 1 it does not produce arc in operation and has high stability. 2 It
can save design cost. 3 Solid state relays are small in size and more likely to be placed in PCB, making the product modular. 4 It can significantly improve the throughput of the data, and
satisfy the requirement of the railway signal to the information transmission rate. 5 Compared with the electromagnetic relay, it has a longer service life. Therefore, the application of solid
state switch instead of traditional relay will become a development trend.
2 Fault tree analysis technique As an important method of safety analysis, tree analysis fault is of great significance to
analyze the safety of equipment and the factors that affect the safety of equipment. Fault analysis technology was developed by Baer laboratory in 1962 [5], which has the characteristics
of clear cause and effect relationship, image and so on. It is mainly used in the following situations: 1 the top events in the analysis of the fault tree are the accidents that have occurred
or the accidents can be expected. 2 to find out the inherent or potential risk factors in the system, and provide scientific and reasonable basis for the safety design, development of safety
technology measures and safety management.
3 Safety reliability design technology Security refers to the ability of equipment accident, and it is an important indicator to
determine the performance evaluation system, and it is also the most important characteristics of signal equipment. Reliability refers to the ability to work without fault, and it is also an
important index to judge the performance of equipment. The application of safety and reliability technology in railway signal mainly include: fault-Safety Technology, error-avoiding technology
and fault-tolerance technology.
2.2. Requirement Analysis of the Control Switch Module
Compared with the general equipment, in the life cycle of safety equipment, in addition to the need for functional requirements analysis of the system, it is necessary to carry out safety
related analysis. This section will analyze the functional requirements and security requirements of the switch control module, and put forward the requirement for the software and hardware
design of the following modules.
Analysis of switch machine interface requirements Switch machine is switch control system of the implementing agencies, which is an
important part of the computer interlocking system execution unit, and it is used for driving the switch and lock and to switch the location and status to reflect. Because it is directly related to
the safety of the equipment, we should pay much attention to the performance and quality of the equipment. Its specific functions are as follows.
Conversion switch [6]: Switch machine must have enough power to drive the switch within the stipulated time to locate or reverse action according to the need.
Lock switch: When the switch conversion is completed, if the tongue rail and basic rail dense paste, switch machine should be the rail mechanical lock in the close state, to prevent
the external force caused by the switch from of the basic track conditions. Reflect the state of the switch: As a monitoring device switch, switch machine should
ensure the correct reflection of the four states of turnout. Module functional requirements analysis
Because the switch control circuit is a safe circuit, it must have a very high safety and reliability. When the fault occurs, it can timely alarm, and take appropriate measures to deal with
security. So the switch control module of distributed computer interlocking should meet the following requirements [7]:
1 It can complete the communication function with the interlocking host, and realize the security exchange of information with the communication extension, and it must use a
secure communication protocol to ensure that the instructions are properly transmitted. 2 The module can carry out self-inspection and fault location, and fault alarm for
abnormal situation. 3 The module can realize the position control and the counter position control function
of the four wire switch. 4 It must be able to capture the position, back and four open in real time, and
send the state information to the interlocking system. Module security requirement analysis
From the concept of safety integrity, it is clear that the safety integrity requirements of
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
