Accessibility Versus Feasibility: Optimizing Function Allocation for Accommodation of Heterogeneous Populations

Abstract

Human beings are physically and cognitively variable, leading to a wide array of potential system use cases. To design safe and effective systems for highly heterogeneous populations, engineers must cater to this variability to minimize the chance of error and system failure. This can be a challenge because of the increasing costs associated with providing additional product variety. Most guidance for navigating these trade-offs is intended for late-stage design, when significant resources have been expended, thus risking expensive redesign or exclusion of users when new human concerns become apparent. Despite the critical need to evaluate accommodation-cost trade-offs in early stages of design, there is currently a lack of structured guidance. In this work, an approach to function modeling is proposed that allows the simultaneous consideration of human and machine functionality. This modeling approach facilitates the allocation of system functions to humans and machines to be used as an accessible baseline for concept development. Further, a multi-objective optimization model was developed to allocate functions with metrics for accommodation and cost. The model was demonstrated on a design case study. 16 senior mechanical engineering students were recruited and tasked with performing the allocation task manually. The results were compared to the output of the optimization model. Results indicated that participants were unable to produce concepts with the same accommodation-cost efficiency as the optimization model. Further, the optimization model successfully produced a wide range of potential product concepts, demonstrating its utility as a decision-aid.

Aligning Functional Analysis Processes With Designers' Natural Cognitive Flow

“…For those that do, this may be the first point in the process where they will begin to gain a better understanding of how their users interact with the product and if the product is liked. If this discovery goes poorly, design teams may be forced to iterate back through the process again with a need for severe change (Knisely, and Vaughn-Cooke, 2022). Unlike iterating back through the process to fix small issues in a prototype design, re-designing around an entirely new user perspective can be wildly expensive if there is a large change in scope.…”

“…Studies have shown that these participants feel bogged down, at times, by the process, and the results they produce are often limited as well. (Caldwell et al, 2012;Knisely and Vaughn-Cooke, 2022) Additionally, these methods are challenging for inexperienced engineers to pick up. Students and early-career engineers that are not thoroughly versed in the design process and accompanying terminology may struggle through functional analysis.…”

“…It is very common in computer and software engineering fields due to their increasingly customer-facing nature (Caldwell et al, 2012;Gericke & Eisenbart, 2017), however it is less common in mechanical design spaces. The idea is that incorporating a user-centric approach earlier on in the design process can limit some of the need for expensive redesigns in future stages (Knisely & Vaughn-Cooke, 2022) and provide better overall products for consumers. Expanding on this concept when developing design methods, it is also important to consider the designers, as they are the users of the design methods themselves.…”