1.2 Product life cycle

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Many products have a long life, of which the “normal” user (so-called end user) only sees a small fraction. To be aware of an entire life of a product, we must understand all of the processes involved in the product’s development and operation, and all activities of the people involved in the processes. The mechanism used to structure these processes and to identify the major activities is called a product life cycle (PLC) model. Usually, we divide a life cycle into several life cycle phases. Each phase is characterized not only by its inputs and final results, but also by its activities, support provided, the roles of the different people involved in the activities, and the different technologies and techniques used in them. Independent of the product type, we can identify six generic phases [1]: the business idea of the product, requirements management, development, production, operation and maintenance, and finally disposal (see Figure 1.2).

Figure 1.2: Generic PLC.

The business idea phase begins with a perception for a new product. It continues with an assessment of the market and technology and with the identification of the key requirements of the product. At this stage a feasibility study is performed (e.g., all available information is collected and, with this as a basis, it is decided if it is feasible to develop the product). An example of feasibility study is when a company receives an inquiry from a customer for a new radar for the next generation of aircraft. The space available for the new radar is specified in the inquiry as approximately one third of that occupied by today’s smallest possible radar. After months of work the feasibility study concludes that it can be done, assuming current trends in computer-aided design (CAD) and application-specific integrated circuit (ASIC) technology are extended some five to six years, and provided that the company buys a patent for 14 layer cards. The estimated risk factor is 30%.

The requirements management phase focuses on a further identification of requirements, their analysis, and their specification. The result of this phase is a product requirements specification.

The next phase, development, includes design and implementation activities. The result from this phase is the implementation of all of the artifacts needed for production. The types of artifacts can vary considerably, depending on the type of product concerned. A typical hardware product includes prototypes and all the material needed for the product production (for example tooling and test equipment). In principle, the development phase for software will complete with the product itself.

The production phase (also called manufacturing phase) is significantly different for software and hardware products. In the case of pure software products, this phase is automated to a high degree and has very low costs in comparison with the other phases; at an absolute minimum, it becomes a matter of only downloading the software product. On the other hand, for a product with hardware elements, this is probably the most demanding and the most costly of all the phases. Therefore, for hardware products, much effort is invested in coping with the production requirements and in keeping production costs low.

Operation and maintenance is the phase in which the product is used by consumers and often the only phase they will see. To ensure correct operation, the product may require continuous support and maintenance. Many products have a short lifetime and require no maintenance. Some products such as jewelry have a long lifetime but require almost no maintenance. Other products require maintenance for years or even decades (e.g., houses and bridges).

The final phase of the life cycle of a product is its disposal. Again, the significance of this phase depends very much on the product. Different aspects related not to the product itself but to its surroundings must be taken into consideration (e.g., its impact on the environment and the question of its replacement). Examples of disposal of products are the delivery of a car to the junkyard. This is actually only the beginning of its disposal—there is disassembly, recovery of recyclable materials, and disposal of nonrecyclables. Another disposal process example is the management of nuclear waste, which lasts over thousands of years. In some countries, the producer of a product is responsible for its final disposal. Many modern products are being designed to be recycled as a result of such legislation.

1.2.1 The development phase

Generic PLC models can be implemented in different ways. There will be particular differences in the cases of software and hardware products. Let us further analyze the development phase for two different types of products: pure software products and pure hardware products.

To describe the main steps of pure hardware development, we can adopt a generic development process from Ulrich and Eppinger [1]. The process contains six steps, as depicted in Figure 1.3 (the lower part). The development phase is preceded by the detailed requirements management. Although the requirements management phase can be treated separately and independently of how the product is realized (e.g., in hardware or software), a detailed requirement solicitation and specification is closely connected to the development, in particular to the conceptual development in which the product concepts are generated. At the system-level design, the architecture of the product is decided, including the identification of subsystems and components. The components are further designed during the detailed design. Testing and refinement includes the building of product prototypes to test both the product and the production system. During the production ramp up, the production system is used for serial production of the product, beginning at a low rate but then increasing to full production.

Figure 1.3: Software and hardware development processes.

The software development process consists of similar phases, expressed in a most illustrative way in the waterfall model [2], shown in Figure 1.3 (the upper part). The model includes the following phases: requirements analysis, design (overall and detailed), implementation, integration and test, and finally release. The detailed requirements analysis phase is completed with a requirements specification. This specification is an input to the system design that consists of two steps: the overall design where the system architecture is designed and the components and their interfaces are identified, and the detailed design in which the component implementations are specified. In the implementation phase, the developers follow the design documentation and implement the system in the form of algorithms and data structures specified and written in different programming languages. If it is possible, components are tested independently. In the integration and system test phase, the integrators build the system from the components. The system is then ready for the system test. The final development phase in this model is the release management, in which the product is packaged in an appropriate form for delivery and installation at the customer’s premises.

1.2.2 Different variants of PLCs

The hardware and software PLC models described here exhibit many similarities. The phases are similar; in many cases, there are no visible differences and the inputs and the goals of the corresponding phases are the same or very similar. Are there any differences then? If so, what are they? To answer these questions, we must analyze these processes in more detail. We must also understand that these models are abstractions and idealizations of the real world. For example, there are many different models that define different software development processes. The waterfall model is known to be a rigid, inflexible, and in many cases inappropriate model, but suitable for explaining and understanding software development process. It has often been used to manage large development processes. Other models (e.g., the unified process [3]) take another approach; the process is divided into a number of incremental stages in which the product is built progressively.

Finally, we should mention that there are many other PLC models that relate particularly to different aspects of product life, such as marketing issues, supply chain, and life cycles for particular products. However, all of these models have needs in common: the possibility of access to correct information, support for information generation, and the possibility of information integration.

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