Page 98 - Design for Environment A Guide to Sustainable Product Development

Managing Envir onmental Innovation 77

is said to be satisfied by a product (or process) if a test or observation
reveals that the described conditions are met by that product (or pro-
cess). The conditions may be represented in various forms, including
• behavioral e.g., “system shall shut down when left idle”
• qualitative e.g., “shall be stable in extreme heat”
• quantitative e.g., “width ≤ (inner radius) × 1.9 cm”
• pictorial e.g., “shall resemble this zigzag pattern”
• logical e.g., “process type shall only be acid or thermal”
The requirements management process consists of three main
functions that are performed repeatedly in an iterative fashion. These
are requirements analysis, requirements tracking, and requirements
verification [6]. Each of these functions is described below:
1. Requirements analysis is the process of interpreting cus-
tomer needs and deriving explicit requirements that can
be understood and interpreted by people and/or computer
programs. It is usually carried out by a select group of pro-
gram managers, chief engineers, and senior project engineers.
Complex designs such as automotive systems can have
thousands of requirements, which are often represented in a
hierarchical fashion.
2. Requirements tracking involves continuous interchange and
negotiation within a project team regarding conflicting and
changing objectives. Design decisions must be weighed in
terms of a variety of factors, including project risk, schedule,
cost constraints, and performance goals. An organizing scheme
such as a traceability hierarchy is helpful in locating specific
types of requirements, navigating through large volumes of
requirements, and adding new ones at appropriate points.
3. Requirements verification is the process of evaluating whether
a product design complies with a designated set of require-
ments. This can be accomplished through actual testing of a
prototype or, at an earlier stage, through predictive methods.
Concurrent engineering teaches that the earlier in the design
process verification can be performed, the more likely it is
that design flaws will be detected before a large prototyping
investment has been made.
After requirements have been defined, the product development
cycle begins in earnest. As the team works on developing a detailed
design, they employ design rules and guidelines drawn from each
of the relevant design disciplines, e.g., manufacturability, maintain-
ability, etc. While automated aids such as expert systems can facilitate
the practice of DFX, the innovative capabilities of human engineers