Re­silient Sys­tems

The term re­silience is used in many sci­en­tific dis­ci­plines rang­ing from ma­te­ri­als to psy­chol­ogy.

We are in­ter­ested in the re­silience of tech­ni­cal sys­tems, fo­cus­ing on cyber phys­i­cal sys­tems of sys­tems (CPSoS). We are re­search­ing op­tions to mea­sure re­silience, de­sign and test re­silient CPSoS. We de­fine CPS(oS) as re­silient, if they have the abil­ity to react to spec­i­fied and un­spec­i­fied dis­tur­bances in a way that pre­serves their func­tion and en­ables them to react quickly. This re­ac­tion in­cludes the early de­tec­tion, min­i­miza­tion, pre­dic­tion or even avoid­ance of dis­tur­bances. The IHP has the fol­low­ing com­pe­ten­cies in the field of re­silient sys­tems:

Re­silience is more than se­cu­rity and re­dun­dancy. Cog­ni­tion makes the dif­fer­ence.

Se­cu­rity is THE pre­req­ui­site needed to en­sure any fea­ture of a cer­tain sys­tem. With­out se­cu­rity an at­tacker can take con­trol of the sys­tem and in con­se­quence all its fea­tures are sub­ject to the in­ten­tion of the at­tacker. 

Re­dun­dancy is a well-​known op­tion to in­crease the re­li­a­bil­ity of al­most any sys­tem. With­out a cer­tain level of re­dun­dancy a sys­tem will fail in the mo­ment at which one of its es­sen­tial com­po­nents breaks. So at the least these com­po­nents re­quire re­dun­dancy. But the af­ford­able re­dun­dancy is lim­ited, e.g. 2 en­gines for cer­tain types of air­planes. But what hap­pens if the re­dun­dancy is lost, e.g. as in the case when an air­plane ex­pe­ri­ences a dou­ble bird strike shortly after take­off.  

Cop­ing with the Un­ex­pected 

What is going to help in an un­ex­pected sit­u­a­tion such as the dou­ble bird strike?

The an­swer is cog­ni­tion, i.e. find­ing a so­lu­tion to a for­merly un­ex­pe­ri­enced prob­lem. As we are work­ing on CPSoS the chal­lenge is not only to come up with a sys­tem that  re­acts prop­erly to such a chal­lenge, but to re­al­ize it with the very lim­ited re­sources of em­bed­ded sys­tems.

So metaphor­i­cally speak­ing, the prob­lem we are try­ing  to solve is squeez­ing Cap­tain Sul­len­berger (the pilot who landed the air­plane on the Hud­son river) into mil­lions of em­bed­ded sys­tems.