Updated on January 10, 2025

Function modeling

Function modeling is the stage in function analysis, during which a function model of the analyzed engineering system is built.

Overview

Function modeling is the final stage of function analysis for both devices and processes. This stage involves creating a function model in the form of a table, a graph, or both.

If cost reduction is the goal of the project, function modeling is supplemented with cost analysis, which provides important information about the components. On one hand, it helps identify the cost-related disadvantages, on the other, it aids in making decisions about which components should be considered for trimming. Function-cost analysis is usually presented by adding a column to the function model table. 

Differences between function modeling for devices and for processes

Function modeling is the stage of function analysis where the two types of analysis differ the most.

Input

The input to function modeling for devices is the interaction matrix, specifically the boxes with the sign “+”. Since interaction is a basic condition for the function to exist, only those pairs of components between which it exists are considered, while all the cells assigned with “–“ are being ignored.
For each cell containing „+” sign, an analysis is performed to investigate if the interaction between components represents a function. The components in the vertical axis are treated as function carriers and the components in the horizontal axis as function objects.

Since the interaction analysis for processes is not performed at all, the input to function modeling is a component model created during the component analysis.

Relation between functions and components

For both types of analyses, the notion of a function remains the same; however the role played by components changes.

In the case of devices, both the carriers and the objects of functions are the previously identified components:

In the case of processes, functions are performed within components (operations), meaning that neither their carriers nor their objects are components:

Function ranking

For devices, a function can have one of three ranks, which depend solely on the status of their objects. The most valued are functions whose object is the a target component. Those directed at other components of the supersystem hold a slightly lower rank. Finally, the least valued are functions that act on the components of the system itself.

Since the target component and the supersystem components are not actively used in processes, ranking for them is based on different criteria.

Procedure

Procedure for function modeling for devices

For devices, the function modeling is performed according to the following procedure:

  1. check whether any function is performed for every interaction identified during the interaction analysis,
  2. specify each function as useful or harmful,
  3. determine the level of performance of the useful function,
  4. rank the functions (if needed),
  5. calculate the functionality index of the engineering system components (if needed),
  6. calculate the value of each component of the engineering system (if needed).

Procedure for function modeling for processes

For processes, the function modeling is performed according to the following procedure:

  1. identify functions performed within each operation,
  2. specify each function as useful or harmful,
  3. rank the useful functions.,
  4. calculate the functionality index of each operation (if needed),
  5. calculate the value of each operation of the engineering system (if needed).
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