October 2006: Lifecycle design issues
Historically, traditional designs have paid little attention to the later parts of the lifecycle. This is understandable because such issues are not of immediate importance to most designers.
One exception to this is manufacturing, but other issues that are often related to maintenance and end of life issues are frequently neglected.
It is generally accepted that in future most design engineers will need to consider all aspects of the design lifecycle. This is not just a case of optimising a design or making a design more cost effective but means a more holistic view of the cost of a product throughout its lifecycle, involving the total cost of ownership. In future, aspects such as this may often be a matter of legislation. In general what is required is an increase in the transparency to the designer of the:
- manufacturing costs
- maintenance costs, and
- termination or end of life (scrap) costs.
What is required is a means by which a deeper insight into lifecycle issues can be attained. The EDC is strongly involved in the development of tools, which can achieve this. Currently what we have is intended for use in the earliest stage in the lifecycle, that is the conceptual design.
To expand this further will require a more complete understanding of the following stages: manufacturing, supportability, cost, implementation, validation, and operational requirements. In effect this means all aspects of the lifecycle from initial concept to final disposal. The result will be an increase in the overall transparency of the product lifecycle. The benefits that will accrue from this approach include: improvement of product quality, concurrency of product and process phases, and an overall reduction in development time.
If we consider Figure 1, we see that in the initial design stage design freedom starts from an arbitrary 100%, but quickly falls as the design progresses into the detailed stages. The objective of the modelling framework, is to lift this freedom thus allowing more flexibility in design.
Extension of the tools we have developed into the later stages of the lifecycle will produce an even greater flexibility into the design stage by increasing transparency. Thus allowing system designers more extended views of their design consequences.
Prospects of an all encompassing design tool
An important aspect is that of storing design rationale and making the knowledge accrued by the system designer available for reuse. An alternate view is that of using information systems as legacy utilities. This is also linked to upgradeability which requires flexibility in the design of a system. As the previous figure shows, an increase in flexibility is one of the aims of the approaches used by the EDC.
If we consider this further we can see that knowledge of a design is also linked to flexibility. That is the decrease in design freedom sees a corresponding increase in knowledge. The overall aim is to lift these levels using tools developed by the EDC. Figure 2 also indicates that by implementing design reuse we can lift the level of knowledge at an earlier stage in the design.
Upgradeability is closely linked to flexibility and knowledge levels. Often a design will be in operation for a number of years before an upgrade is considered. It is also extremely difficult to design with upgradeability in mind, since technology will advance and the scope of any future upgrade must be generally unknown to the designer.
Therefore by increasing the levels of design freedom and knowledge this will give greater scope to the issue of upgradeability. This will also be facilitated by using the design tools developed by the EDC as fully integrated information systems, which can track and monitor changes as well as giving some indication of the knock-on effects dueing the entire lifecycle of a product.
Author: John Dalton