Monday, April 3, 2017

Resilient Systems and Resilient Design

We hear the word "resilience" a lot these days.  It's a word that's ripe for misuse and vagueness.  
There is a general agreement that resilience is the intrinsic ability of a system to resist disturbances.  Another equivalent definition of resilience is the ability to provide required capability in the face of adversity (sometimes referred to as disaster recovery).  Resilient design is about managing the ubiquitous uncertainties that constrain current design practices as well as finding ways to overcome an imperfect understanding of system requirements that lead to fragile and ineffectual system designs.

The definitions above are fine, but the real question is what is the “scope” of the system – and this is where views vary.  In this blog we focus on electronic products and systems, however, the concepts of resilience and resilient design are more prevalent in the building construction, architecture, and communities design space.

When you talk about resilient systems, several disciplines think they have a handle on the problem.  The control systems folks think that this is their domain, the optimization folks, the PHM (system health management) folks, the reliability engineering folks, sustainability folks, the system engineering folks, machine learning, artificial intelligence, … In my experience, none of these disciplines (with the possible exception of some system engineers) really grasps the total scope of resilience.  Every discipline wants to gather resilience under their umbrella and grant themselves ownership of the problem space based on their narrowed definition of what a system is.

In my opinion, designing resilient hardware and software (which is the focus of most resilient system design activities) is necessary but not sufficient for creating resilient systems.  For a system to be resilient requires:
  • reliable (or self-managing) hardware and software
  • a resilient logistics plan (including supply chain and workforce management)
  • a resilient contract structure
  • resilient legislation or governance (rules, laws, policy)
  • a resilient business model
One might also include within all of the above aspects, a resilience to changes in the end-of-support for the system.  For many systems, the end-of-support is a moving target that is extended ("life extensions") during the use of the system.

This represents a somewhat broader scope than what is generally articulated in the engineering literature, however, in practice, neglecting any of these elements potentially creates a legacy system with substantial (and potentially untenable) life-cycle support costs.

Although the discussion in this blog has an electronic product/system focus (our "scope").  Resilient design can certainly be applied to other things, e.g., buildings, communities, furniture, information technology, websites, health care, etc.  In this broader world one could consider adding the following to the bullets above:
  • culturally resilient (does the system transcend cultures and culture changes)
  • environmental resilience (sustainability)
  • resilience to climate change