# Hybrid Decision-Making-Method-Based Intelligent System for Integrated Bogie Welding Manufacturing
## 3 Experiments
### Build Cases and Rules  
Case construction is divided into three subtasks: case representation, case retrieval, and case revision. Case representation can also be seen as a form of case storage. Depending on the data characteristics of the weld file, cases are stored in a structured database. Case retrieval is a critical element of the acquisition decision, and the best matching result is obtained by calculating the similarity between new and old cases. The similarity calculation compares the problem with the known cases to obtain the highest matching result to complete the decision. In order to obtain credible matching results, the computational process must consider the attribute characteristics of the target data. As far as welding decisions are concerned, each condition attribute has a different degree of influence on the result attribute. It is necessary to define the weights for each attribute. The steps of similarity calculation based on weight are as follows:  
1. Case similarity calculation. The new case is defined as P, the old case as C, and the similarity calculation process between cases is shown in Equation (4). We calculate the product of the similarity of each attribute and its weight and sum it to obtain the case similarity. Here, \(\mathrm{sim}\) (P, C) represents the case similarity, n is the number of case condition attributes, ai represents the i-th attribute, and \(\omega_{\mathrm{i}}\) represents the i-th attribute weight: \[\mathrm{sim}(P,C)=\sum_{i=1}^{n}\omega_{i}\cdot\mathrm{sim}\left(a_{i}^{P},a _{i}^{C}\right)\] (4)
2. Attribute similarity calculation. Attributes generally include numeric, symbolic, and conforming attributes. Equation (5) is the numerical attribute calculation process. For symbolic attributes, the attribute similarity is \"1\" when the attribute values are equal and \"0\" when the attribute values are unequal. The calculation process is shown in Equation (6). Composite attributes contain numeric and symbolic characteristics. Among them, the symbolic feature is selected as the first matching element. The similarity is calculated according to Equation (5), when the symbols are equal. If the symbols are not equal, the similarity is \"0\": \[\mathrm{sim}\left(a_{i}^{P},a_{i}^{C}\right)=\frac{1}{m^{|a_{i}^{P}-a_{i}^{C}| }},\] (5) \[\mathrm{sim}\left(a_{i}^{P},a_{i}^{C}\right)=\left\{ \begin{array}{l}1,a_{i} ^{P}=a_{i}^{C}\\ 0,a_{i}^{P}\
eq a_{i}^{C}\end{array} \right.,\] (6) where \(a_{i}^{P}\) is the i-th attribute value of the new case, \(a_{i}^{C}\) is the i-th attribute value of the old case, and m is constant (\(m=1.2\) according to field experience). 3. Attribute weight division. Assigning the same weight to the attributes is unreasonable because the conditional attributes in the case have different degrees of influence on the decision attributes. Therefore, the conditional attribute weights are calculatedbased on the number of decision attributes associated with the attribute, which is calculated as Equation (7), where ai denotes the i-th conditional attribute and count(ai) denotes the number of decision attributes associated with the conditional attribute:  
\[\omega_{i}=\frac{\text{count}(a_{i})}{\sum\limits_{i=1}^{n}\text{count}(a_{i})} \tag{7}\]  
Based on expert experience, 0.85 is chosen as the case-matching threshold, and cases below the threshold do not have reusability. For valid cases, case revision is required to ensure the usability of the case. Rule-based decision-making methods are employed to revise the case. Rule construction is the process of transforming expert experience into an executable computer program. Logic rules are divided into dynamic rules and static rules. Dynamic rules rely on database calls to build the logic. For example, the decision rules for welding procedure qualification records (WPQR) require a structural database correspondence to complete the development. Rules constructed only through logical relations and predicates are called static rules, for example, \"IF weld quality level == CP A THEN weld inspection level == CT 1\".