Why we have infinity solution? We have to consider that we have to make a trade off between these two extremes up. If we plot the objective functions, say wear and vibrations, on a point on a plane, and for example we define a number of possible feasible parameter, we can imagine to simulate the behaviour of the system and for each parameter set we can have a different behaviour of the system. By performing this many times I can fill an area and I can find a boundary which is called Pareto set. The Pareto set represents the best trade off possible.

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