## 2 Safety Analysis Framework for Complex Electromechanical Equipment System Based on STAMP
### A Safety Analysis Framework for Complex Electromechanical System Based on STAMP  
The electromechanical equipment system is the most common part of an integrated system, in which humans can operate control system consisting of computer or programmable logic controller (PLC). The cooperation of various parts such as electronic components, mechanical parts, and industrial control algorithms can guarantee system safety of the electromechanical equipment system. Due to the  
\begin{table}
\begin{tabular}{p{56.9 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Method** & **Time\& by** & **Advantages** & **Disadvantages** \\ \hline \multirow{4}{*}{**FTA**} & 1961 & Concise expression of causality and logic; Predict and Prevent accident; Qualitative and quantitative analysis & Not for analysis of a process or equipment system; More steps and computational complexity for a complex system; The probability of all basic events needs to know for quantitative analysis etc. \\ \hline \multirow{4}{*}{**FMECA**} & 1950s & The whole process of product development; Principle and operation are simple; The base of other failure analysis & Heavy workload, time-consuming; Univariate analysis; Limited by environmental conditions; Poor generality of the conclusion, etc. \\ \hline \multirow{4}{*}{**HAZOP**} & 1974 & Detailed analysis of process engineering; Design evaluation and operation evaluation; & Need professional groups to work; Ignore the interaction between subsystems \\ \hline \multirow{4}{*}{**STAMP**} & 2004 & Understanding accidents from the perspective of system theory of Massachusetts Institute of Technology & Emphasize social factors; Mostly the interaction between systems; & Mostly used for qualitative analysis and need to be combined with other methods for quantitative analysis \\ \hline \hline \end{tabular}
\end{table}
Table 2: Comparison of safety analysis techniques.  
complex mechanical components and control process, traditional hazard analysis methods based on event chain model have limitations in exploring component interaction failure and process unmatched in such a complex social-technical system. Therefore, a hazard analysis framework for complex electromechanical equipment based on STAMP is proposed in this paper. Figure 6 shows the main diagram of the framework.  
Figure 6 can be divided into four parts: (1) Firstly, safety requirements of an electromechanical equipment system can be determined on the basis of system understanding and accident case collection, then hierarchy structure model of equipment and process model of operation should be established. (2) Secondly, safety constraints can be defined by hierarchy structure model and process model combined with safety requirements; Then, safety control structure and safety control process are established. Iterative STPA are performed with the help of basic unsafe control principles to identify unsafe control constraints and example casual scenarios. (3) Specific hazards (such as component failure, components interaction failure, external disturbance, dangerous behavior of the system and so on) for accident can be identified based on the analysis of STPA. (4) Finally, some targeted improvement measures can be added according to some key hazards such as components failure and components interaction failure.