连杆机构英文文献和中文翻译(2)

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Much of engineering education deals with topics of analysis, which means to de- compose, to take apart, to resolve into its constituent parts. This is quite necessary. The engineer must know how to analyze systems of various types, mechanical, electrical, thermal, or fluid. Analysis requires a thorough understanding of both the appropriate mathematical techniques and the fundamental physics of the system's function. But, before any system can be analyzed, it must exist, and a blank sheet of paper provides lit- tle substance for analysis. Thus the first step in any engineering design exercise is that of synthesis, which means putting together.

The design engineer, in practice, regardless of discipline, continuously faces the challenge of structuring the unstructured problem. Inevitably, the problem as posed to the engineer is ill-defined and incomplete. Before any attempt can be made to analyze the situation he or she must first carefully define the problem, using an engineering ap- proach, to ensure that any proposed solution will solve the right problem. Many exam- ples exist of excellent engineering solutions which were ultimately rejected because they solved the wrong problem, i.e., a different one than the client really had.

Much research has been devoted to the definition of various "design processes" in- tended to provide means to structure the unstructured problem and lead to a viable solu- tion. Some of these processes present dozens of steps, others only a few. The one pre- sented in Table 1-1 contains 10 steps and has, in the author's experience, proven success- ful in over 30 years of practice in engineering design.

ITERATION Before discussing each of these steps in detail it is necessary to point out that this is not a process in which one proceeds from step one through ten in a linear fashion. Rather it is, by its nature, an iterative process in which progress is made halt- ingly, two steps forward and one step back. It is inherently circular. To iterate means to repeat, to return to a previous state. If, for example, your apparently great idea, upon analysis, turns out to violate the second law of thermodynamics, you can return to the ideation step and get a better idea! Or, if necessary, you can return to an earlier step in the process, perhaps the background research, and learn more about the problem. With the understanding that the actual execution of the process involves iteration, for simplic- ity, we will now discuss each step in the order listed in Table 1-1.