Satisfying ranged sets of design requirements using design capability indices as metrics

In this paper the notion of design capability indices is introduced for use in robust design. Design capability indices are based on process capability indices from statistical process control and provide an alternate approach to the use of Taguchi's signal-to-noise ratio in robust design. Successful implementation of design capability indices ensures that a range of design solutions, representing a family of designs, conforms to a given ranged set of design requirements. The design of a solar powered irrigation system is presented to demonstrate the usefulness of design capability indices.