By Eugene le Roux, FSAIRAC, and Eamonn Ryan
Engineering projects seldom achieve the optimum solution on the first attempt. Whether designing a vehicle, machine or industrial system, engineers often begin with estimated values that evolve as the design matures. Iterative modelling is therefore an essential part of the System Engineering Process (SEP), allowing designers to refine their assumptions until every aspect of the project is consistent. In Part 1, we examine why repeated modelling is necessary and how it helps engineers produce designs that meet performance requirements.
Not every aspect of the design can be automated.
Tirachardz | Magnific.com
Consider the development of a new vehicle with a specified maximum mass of six tonnes. Before any hardware is manufactured, the vehicle must first be modelled as part of the System Engineering Process (SEP) to determine whether it can meet all of the prescribed performance requirements.
One of the challenges is that the vehicle’s mass is both an input and an output of the modelling process. The mass is required as an input to perform the engineering calculations, yet the true mass only becomes known once the design has been completed and simulated.
The logical approach is to begin with the specified maximum mass, or preferably a slightly higher estimate, as the starting point for the design.
Once the first simulation has been completed, however, the calculated mass often differs from the original estimate. Frequently, the simulated vehicle is heavier than anticipated. Because the entire design has been based on an incorrect input mass, the modelling process must be repeated using the revised value.
This process continues until the calculated final mass closely matches the mass used as the input for the model. Only then can the engineer have confidence that the design is internally consistent and that subsequent calculations accurately reflect the final product.
Several iterations may be required before this point is reached. For that reason, as much of the design process as possible should be automated using engineering software or spreadsheet tools such as Excel. Automating calculations allows engineers to update the design efficiently without having to repeat every calculation manually during each iteration.
Not every aspect of the design can be automated. Certain engineering decisions still require information to be selected from technical catalogues or reference tables, such as bearing sizes, oil seal dimensions and other standard components. Nevertheless, automating the bulk of the calculations significantly reduces engineering effort while improving consistency throughout the design process.
The ultimate objective is to produce a model that is complete, consistent, executable and compliant with all applicable requirements before the project progresses to the next stage.
Coming in Part 2
Now that the design has reached a consistent solution through iterative modelling, the next challenge is ensuring that the project remains on course. In Part 2, we examine how Engineering Change Proposals (ECPs) help manage changing requirements, why protecting the technical baseline is critical, and what can happen when project consistency is allowed to deteriorate.
