Friday, 21 November 2008

Assessing Conflicting Design Requirements (Car Example)

This Southbeach Model shows one of the key principles from TRIZ, namely that everything is both useful and harmful, and its just a matter of perspective as to whether something is considered to be predomantly useful or harmful.

Consider the Car, useful, as it provides Travel; however, it consumes fuel and creates pollution, which counteracts the Environment. People still drive cars despite this, hence the car is considered predominantly useful despite its harmful side effects. Furthermore, "The need for speed", or the need to accelerate to higher speeds more quickly, results in many cars also having turbo chargers. These typically are designed to improve performance and this is often at the cost of creating even more pollution.

Southbeach can be used to understand root causes and perform impact analysis. Also, it is useful for functional decomposition of systems. Consider the following extension to the above diagram:

Here we have extrapolated that pollution contributes to Global Warming, which in turn is actually destroying the Environment, and in a much stronger way than pollution alone. The model recognises that there are also other factors contributing to Global Warming, and that these may be worth exploring. What you explore depends on who you are and what you are trying to do. An environmentalist may explore this avenue. A car manufacturer may explore the pollution avenue in more detail. There are examples of car manufacturers who have taken that extra step and recognised that the car could potentially clean the environment - having an overall positive effect. There are actually cars that clean the air now.

This model additionally shows how further design considerations result in systems becoming more complex over time. Here the need to improve cost effectiveness and reduce pollution has resulted in this car being upgraded to include an economy mode (or "green" mode). This reduces the fuel consumption. However, for comfort this car has also been upgraded to include air conditioning to improve comfort, a desirable feature of the car. This counteracts the economy, hence increasing the fuel consumption and increasing the pollution.

The system is now considerably more complex, and as a consequence contains many more tensions as parts of the system are working in opposition to each other. This results in another iteration of the design process, where further parts are added to compensate for the conflicting effects of the existing parts. The result will be an even more complex system, but by design, this will reduce waste by resolving some of these technical contradictions between the components. There are other ways to improve systems, and some designers are exploring how instead of adding more and more parts (increasing the weight, incidentally, and thereby increasing fuel consumption further), they are looking for ways of improving component design and simplifying the overall design to increase the harmony of the system. This involves taking a holistic approach to the design goals. We will talk more about this in future.

A further elaboration of this model might observe that Car's only produce polution when they are travelling - and it is actually the act of consuming fuel that is the primary cause of that pollution. This model below shows the pollution being created by the act of fuel consumption, and breaks that pollution down into different types using the 'is-a' construct. This elaborated model also includes blue boxes indicating the actions that could be considered to improve the situation.

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