When faced with an obstacle, human nature pushes us to avoid or remove what’s in our way. But an alternative approach to engineering does neither, at least initially. Known as TRIZ (pronounced treez), it intentionally embraces and reproduces the challenge to get a closer look.
When encountering airplane GPS dropout, for example, a TRIZ practitioner does not try to eliminate the issue right away. The first step is to replicate it. That is, assume that the desired output from the GPS is the dropout under the right conditions. To find the right conditions, define the requirements for a field (the means of accomplishing an action), which in this case would interfere with GPS reception. Surprisingly, this change of perspective can open up the team’s thinking and, with the aid of TRIZ techniques, identify how resources available in the system create the now-desired complication.
A Russian acronym that translates loosely to “Theory of Inventive Problem Solving,” TRIZ attempts to overcome innate mental inertia that pressures us to maintain a set of assumptions and patterns of thought.
Our brains prefer fast and automatic to slow and effortful. TRIZ encourages us to break out of these well-worn tracks.
The basic premise is that someone, someplace, has already solved our problem or one very similar to it. The method breaks down the issue, generalizes it and finds relevant solutions from principles discovered by the world’s best problem-solvers — inventors.
Over the last two decades, Boeing has leveraged TRIZ to:
- Improve designs, such as finding adequate power to meet a fuel offload rate requirement for the KC-767 Tanker.
- Develop inventions, including clamping mechanisms for aircraft interiors, rain-on-the-plane solutions and new actuation technologies.
- Suggest a technology forecasting strategy.
- Remove contradictions that lead to compromise designs.
For our GPS example, our team identified key features of the system failure and organized these into a fishbone diagram. However, after close to a year of root cause analysis and lab testing, the cause of an intermittent failure remained unclear.
We decided to conduct a two-hour TRIZ workshop. The roles in the workshop included a TRIZ facilitator, TRIZ scribe, TRIZ expert and workshop participants with technical expertise for the problem domain. During the workshop, a type of TRIZ analysis called Tool-Object-Product was created. In this analysis, a model of the situation is created where a tool acts on an object through a field. The product is the result of the action of the tool on the object.
The strategy used in this workshop was to reveal the cause.
Workshop participants completed some preliminary problem formulation then followed a step-by-step process to create what we were trying to ultimately avoid, as if it were a “desired” product. The desired product in this case study was GPS dropout.
The key activity was to define the requirements that have to be met by the field to obtain that previously undesirable product. This was the point in the workshop where it became clear that there was a signal-to-noise ratio requirement for noise to cause GPS dropout. While this seems obvious in retrospect, the combination of a weak GPS signal with a jamming signal as the cause for GPS dropout had not been formally considered prior to the TRIZ workshop. A weakness for combinatorial causality is a known drawback to fishbone diagrams.
The team next designed and coordinated a laboratory test of the dropout conditions. The approach was to place the GPS antenna in a room shielded from electromagnetic radiation. A signal would be introduced using a GPS simulator so that the intensity of it could be varied. At various levels of GPS signal intensity, interference signals would be introduced to determine the susceptibility of the GPS antenna to interference. Interference would be detected by loss of a GPS fix at the multi-mode receiver, located outside the shield room.
Lab test results showed that an interference signal of sufficient strength in combination with a weak GPS signal does indeed cause GPS dropout. The team used this information to make recommendations on how to use new designs already available to solve this GPS dropout.
We didn’t set out to find a fix right away.
TRIZ nudged us to look at the issue from a different angle. And the solution was revealed by creating a model of the problem.
The Boeing Technical Journal is a peer-reviewed, proprietary periodical for Boeing subject matter experts to capture and share knowledge.This article is a summary of “Root cause analysis using TRIZ” by Scott Button, Al Nguyen, Robert Hainline and F. Tad Calkins, an article originally published April 9, 2020.