From Concept to Verification
Once the team finalizes safety goals and objectives to determine what the projected performance will be—which, for receivers, is positioning accuracy and the expected reliability of that position—they move on to the concept phase, Auld explained. During this phase, engineers develop the proposed architecture that meets the outlined objectives and then complete a Failure Mode Effects Analysis (FMEA) that takes a step-by-step approach to identifying all possible failures in a design. As they develop the prototype, they ask themselves what could go wrong and the different ways the system might not work as expected.
From there, engineers incorporate mitigations into the design to minimize the chance of something going wrong, and to prove they can meet the outlined safety objectives, Auld said. Strict coding and design standards must be followed when writing the firmware, which will further minimize the chance of future problems while also possibly constraining how the team can develop the product.
“You have to perform various levels of verification on the software and the hardware,” Auld added. “Instead of ‘black box’ testing, you might have to go into the code and make sure every line is justified, executed, and individually behaving itself.”
While developing these products, engineers must address different levels of safety. While for some products achieving the overall safety level may only add a small amount of time to the development process, the time added to designing products with higher safety standards can be quite substantial.
Testing and Regulatory Approval
With safety-certified products, it’s not just a matter of building a prototype and then testing it when it’s finished, Auld explained. Various testing and verification activities are built into the product development process at every step, starting with verifying the system specifications.
“Verification steps are staged throughout the process with the objective of finding problems as early as possible so they can be fixed before the end of the project. That’s good design practice anyway,” Auld said. “In a lot of cases you build the prototype, get it working, then conduct extensive testing on it. In this case that would still happen, but leading up to the prototype there are verification steps throughout the process.”
At the end of a project, receiving approval doesn’t depend on a regulatory agency so much as members of the industry the product is designed for. In the aviation world, for example, aircraft manufacturers and related experts take the team through an approval audit to ensure they carried out the required due diligence during the design process. This includes not only delivering on and executing all the necessary steps, but also producing evidence that they completed each necessary task.
“You don’t send the product to a lab to get certified,” Auld said. “It’s different depending on the industry, but it all comes down to an audit. Someone looks at the process you followed and at the design artifacts you generated and confirms that you’ve done your due diligence.”