11 - Design of fault tolerant systems

Abstract

The human body is an excellent example of a fault tolerant system. If the body suffers an injury to a limb, the muscles on the other fully functional limbs develop to compensate for the loss. Similarly, if there is a loss of one of the senses, other senses develop to make up for that loss. The concept of a fault tolerant system is quite simple; the important thing to remember is that fault tolerance has to be designed into a product. This chapter adopts a rather different approach by looking at ways in which an equipment or system can be made to operate within specification when a fault is present. Fault tolerance can be defined as the ability of a system to operate within specification even when a fault is present. The more complex and more critical an item of equipment or system is, the more it can benefit from a degree of fault tolerance. Simple, non-critical equipment is unlikely to be a candidate for the implementation of a fault tolerant system, even though some parts of the equipment may exhibit a degree of fault tolerance in their operation.