# The Research of Complex Product Design Process Model under the Concept of Self-Recovery
## 2 Relevant Research
### Research of Complex Products at the Functional Level  
Mechanical products designed under the self-recovery concept usually need to operate under extreme working conditions, and there will be non-linear, coupling, openness, time-varying, and other complex product features between various physical processes in the product. At the same time, in axiomatic design, [PERSON] [2] proposed that product analysis from the functional perspective is an effective method for complex product design; therefore, the product analysis method and solution method at the functional level can be applied to the complex product design process under the self-recovery concept.  
[PERSON] et al. [16] combined physical laws with function decomposition, subdivided product requirements through function units, and used physical laws to assist function unit solutions, thus improving the analysis speed and design accuracy of complex products. [PERSON] et al. [17] quantified the similarity between each function unit and established the relationship between user requirements and each function unit through function decomposition and functional analogy, which accelerated the generation of conceptual solutions for ideal product principal solutions. Using function decomposition to decompose the total function of complex products into function units is the key to analyzing products from the functional perspective and reducing the difficulty of product design.  
[PERSON] et al. [18] organically combined the function units obtained by function decomposition with flows to establish the product function structure. The changes in product parameters were expressed in the function structure by flow attributes, and a model for analyzing and solving multi-flow problems of complex products was constructed. [PERSON] et al. [19] analyzed the parameter changes in the product through the changes in flows in the function structure and established the process model of implicit conflict identification of complex products in combination with failure analysis to solve the problem of the strong latency of implicit conflict in complex products. By marking the flow in the function structure, the process of parameter change from raw materials to goods can be clearly expressed, and the functions that have problems in the products can be analyzed by detecting parameter changes.  
[PERSON] et al. [7] transformed the dimension of parameters in the product into the length and time dimension (LT parameter), and the genetic idea of the length and time dimension matrix (LT matrix) was applied to the product problem-solving process, combined with an effect library to produce a disruptive and innovative design solution for complex products. [PERSON] et al. [20] built an effect chain reasoning process guided by idealized physical quantity resources through the connection between the LT dimension and physical effects, where the generation of high-level innovative solutions was accelerated by using an LT matrix. Using the connection between the LT dimension and effect and combining the genetic ideas in the LT matrix with effect library software for solving product problems will speed up the solution of complex products and improve the efficiency of complex product design.  
As can be seen, scholars all over the world have conducted a lot of research at the functional level and put forward relatively perfect problem analyses and solutions. By combining the self-recovery concept with product analysis methods and solution methods at the functional level and extending the application of the self-recovery concept to the functional level, intelligent product design will be carried out from more angles and the design ideas of complex products will be broadened.