The successful release of an electronic device is about more than just the fundamental design of the product itself. To build a high quality product, it’s important to keep in mind testability and manufacturability from early on in the design cycle. In order to accomplish this, a designer has to consider these goals in all aspects of the design, whether it’s following printed circuit board (PCB) design standards or minimizing the complexity of the mechanical assembly. For the Myo armband, there have been many challenges that we’ve had to overcome on the hardware team. Some of the topics that I’ll go into more detail on include the difficulties of testing wearable technology, the development of custom test systems, and the construction of a standard test tracking and analysis architecture from the ground up.
When testing wearable tech like the Myo™ armband in production, it’s important to consider that there won’t be a real person there to generate the muscle signals needed to test functionality. Using a human to do this would be extremely time consuming and exhausting. To come up with a solution, we had to find a way to emulate the signal from a human forearm in a repeatable and controlled way. What we ended up doing was creating a shaped mandrel, which is the device on which the Myo under test will reside. We then embedded the mandrel with a set of muscle signal emulators that allow us to imitate real EMG signals with arbitrary waveform generators, based on data collected by Thalmic’s Machine Intelligence team. The flexibility of our test system allows us to compare the signal response of the units under test to that of a set of ideal or “golden” Myo devices. Using Fourier transforms, we’re able to get a detailed analysis of each unit to be tracked and recorded. This transform converts the signal characteristics into useful, time-invariant frequency characteristics.
To design a test system for a product as unique and complex as the Myo armband, many factors come into play. One of the main ones was that we had to determine what needed to be tested during the design stage versus the production stage. Once we determined the criteria to be tested, a formal manufacturing test proposal was drafted and used to develop the test systems. When designing the test systems themselves, we had to take into consideration not only the electrical tests of the individual components, but also the functional tests of the assembled unit. The functional tests of the Myo armband required verifying the function and performance of the EMG sensing, in addition to key aspects of the product such as Bluetooth, USB and IMU (motion sensing) capabilities. The design of these tests systems requires a large amount of coordination between all of the Thalmic Labs designers – as each team plays their own vital role in the product!
Another interesting aspect of working on the first product of a tech start-up is that there aren’t many established standards for testing and manufacturing frameworks. Many things need to be determined such as how units will be serialized, how data will be collected and analyzed, as well as how any issues will be tracked and dealt with. What’s great about working in this kind of environment is that you have the opportunity to sit down with team members and really determine what will work best for the future. Aspects like volume of units and serial numbers have to be extendable to future revisions. The data you collect from testing has to be processed and analyzed in order to take advantage of any improvements, or trends that may present themselves way before the units make it into the wild. Any issues or bugs that are found must be recorded in detail and be assignable to those responsible for looking for solutions.
At Thalmic Labs, I’m working alongside some of the best and brightest engineers in the world who are working through these challenges to deliver an amazing product. It’s important for all of our design teams to work together so that all aspects of the Myo armband function well in unison. With the amount of talent that we’ve got in our labs, we’re truly bringing the future to consumers.