# A Review of Research on Diagnosability of Control Systems Based on Structural Analysis
## 4 Diagnosability Design Based on Structural Analysis
### Actual Diagnostic Design
#### 4.2.2 MSO-Based Residual Observer Design  
The principle of fault diagnosis based on structural analysis is to use the ARR to build a test set as a residual generator and to determine whether the system is faulty based on the residual signal generated. The structural analysis-based fault diagnosis system generates residuals based on MSO and designs fault diagnosis strategies and methods based on the sensitive relationship between the residuals and the faults. As the structural model ignores the constraint relationship between the variables, the design of residuals in practice will encounter various difficulties, such as the causal relationship of dynamic variables, noise, unknown inputs, interference, modeling uncertainty, and other effects. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Author** & **Reference** & **Objects** & **Fault** & **Diagnosis Strategies** & **Particularities** \\ \hline \multirow{4}{*}{[PERSON]} & \multirow{4}{*}{[61]} & \multirow{4}{*}{Sensor faults} & \multirow{4}{*}{Sensor faults} & [PERSON] used actual data for correlation analysis of output variables with input variables. & The methods based on structural analysis are more straightforward than data-driven fault diagnosis and guarantee good performance in the presence of noise. \\  & & & & \\  & & & & \\  & & & & \\  & & & & \\  & & & & \\  & & & & \\ \hline \multirow{4}{*}{[PERSON]} & \multirow{4}{*}{[62]} & Complex industries systems & All faults & [PERSON] proposed a robust fault diagnosis method based on structural analysis and data-driven diagnosis. & The method does not require precise mathematical modeling and applies to various natural industrial systems. \\  & & & & \\  & & & & \\  & & & & \\  & & & & \\  & & & & \\  & & & & \\  & & & & \\ \hline \multirow{4}{*}{[PERSON]} & \multirow{4}{*}{[63]} & \multirow{4}{*}{Two-tank system} & Multiplicative fault diagnosis method based on a grey-box neural network and structural analysis. & The method optimizes the DM decomposition algorithm, reducing the complexity of DM decomposition and the matching number. \\  & & & & \\  & & & & \\  & & & & \\  & & & & \\  & & & & \\  & & & & \\ \hline \multirow{4}{*}{[PERSON]} & \multirow{4}{*}{[65]} & \multirow{4}{*}{Electrified vehicle systems} & \multirow{4}{*}{Sensor faults} & [PERSON] proposed a model-based fault detection and isolation diagnostic tool based on structural analysis. & The method can diagnose any fault; the residual selection criterion is designed to select the optimal diagnostic test with the most desirable diagnostic performance from candidate solutions. \\ \hline \multirow{4}{*}{[PERSON]} & \multirow{4}{*}{[66]} & \multirow{4}{*}{Drive-by-wire systems} & Mechanical isolation fault and pedal & [PERSON] generated system residuals based on the MSO ensemble and further detected and isolated the faults through sensor design. \\  & & & & \\  & & & \\  & & & \\  & & & \\  & & & \\ \hline \multirow{4}{*}{[PERSON]} & \multirow{4}{*}{[67]} & \multirow{4}{*}{Electrical distribution} & Defects in instrumentation, power generation, transformation, and transmission & [PERSON] proposed a method for fault diagnosis of power distribution systems. & The method is susceptible to noise as well as external interference. \\  & & & & \\  & & & & \\  & & & & \\ \hline \multirow{4}{*}{[PERSON]} & \multirow{4}{*}{[68]} & Four-tank monitored system & All faults & [PERSON] proposed a diagnosability analysis method for augmenting and generalizing structural models. & The method significantly reduces the structural analysis-based diagnosis time and the computational complexity. \\ \cline{1-1}  & & & & \\ \hline \multirow{4}{*}{[PERSON]} & \multirow{4}{*}{[69]} & \multirow{4}{*}{Traction system} & Sensor and IGBT faults & [PERSON] proposed a real-time fault diagnosis method for pulse rectifiers of traction systems based on structural analysis. & The method significantly reduces the structural analysis-based diagnosis time and the computational complexity. \\ \cline{1-1}  & & & & \\ \hline \end{tabular}
\end{table}