The trade study is a critical component of your capstone. It serves to demonstrate your ability to evaluate multiple alternatives for a system component or solution and make an informed decision based on objective criteria.
The Trade Study report is an interim artifact during the execution of the Concept Definition life cycle phase (Kossiakoff Chapters 7 & 11).
If you require a refresher, here's the latest trade study walkthrough lesson from the Intro Course.
Here's what you need to know:
The purpose of the trade study is to prove to the university that you know how to conduct a trade study within the framework of systems engineering. It’s not about developing a comprehensive system architecture with fully validated components, but rather about demonstrating your ability to evaluate alternatives using established methods.
When selecting components for your trade study, choose something that is:
High Risk: Components that are critical to the system’s success but carry significant risk.
Critical and Immature: Components essential to the system's primary mission but still in developmental stages.
Easily Obtainable Data: Components for which you can easily access data online, allowing for a straightforward comparison.
Avoid over-complicating the trade study. You shouldn’t need to contact manufacturers or dig deep for obscure data. The point is to use easily accessible information to demonstrate your trade study skills.
To convert raw values such as mph, lumens, bandwidth, power available, and so on into a common scale, there are two primary methods taught in the program:
Pair-Wise Comparison: This method converts subjective criteria into objective, measurable criteria using eigenvector mathematics.
Utility Curves: This method uses utility curves to evaluate alternatives based on their performance against established thresholds and objectives. Here's a helpful utility function chart.
Use one or both of these methods to conduct your trade study.
Cost analysis is optional and should be done independently of the trade study criteria. Cost should not be one of the criteria but can be factored in after the primary analysis.
Inconsistent Utility Scales: Ensure all criteria are evaluated on the same scale. Inconsistent scales (e.g., one criterion on a scale of 1-5, another on 1-10) will skew results.
Criteria Not Based on Requirements: All criteria must be directly traceable to requirements from your Requirements Analysis Report. Ensure your criteria are aligned with the "shall" statements in your system specification.
Utility Scales Not Linked to Thresholds and Objectives: When using utility curves, the scales should align with your system’s performance thresholds and objectives. For example, if a system has a speed requirement of 80 mph (threshold) and 100 mph (objective), your utility curve should reflect this range. We should not see the Utility Scale begin at 0 and extend to some arbitrary number.
Purpose of the trade study
Selection criteria are described and their source is identified (must be tied to one or more requirements). If you can’t tie a selection criterion to a requirement, it means that you are missing a requirement. Generate a requirement at this time and include it in your A-Spec.
Alternatives are described and referenced. Overachievers: include pictures!
Criteria Weights are applied with a rationale (their source and method should be identified). Weights are generated using one or more of the following methods:
Customer/stakeholder survey
Pair-wise comparison technique (either Nth-root method, or Binary method; I recommend Nth-root method.)
Analytical Hierarchy Process
Quality Functional Deployment house of quality
Utility functions are plotted and described. All labels should be provided. Overachievers: a rationale or source should be presented.
Raw scores are provided and their sources identified.
Weighted utility scores are calculated; use the template I provide if you don’t have one.
Discussion of the results
Sensitivity analysis
Description of the selected alternative
Overachievers: additional requirements, if any. Note: Many students have additional requirements after performing the trade study. What have you learned? Did you identify a criterion that had no corresponding requirement? If so, add a requirement.
Note: The trade study is not just the mechanics of performing the trade study. The “whys” need to be evident. Why did you do the trade study? What rationale did you use to generate alternatives, criteria, weights and utility functions? What was the result? What decision(s) did you make? Is your physical concept representative of the decision made in the trade study?
TS Checklist Checklist Credit: Steve Biemer