If we combine these three fonus of damping, their sum will look like Figure 1O-5d
and e. This is obviously a nonlinear function. But we can approximate it over a reasonably
small range of velocity as a linear function with a slope c which is then a pseudoviscous
damping coefficient. This is shown in Figure 1O-5f. While not an exact method
to account for the true damping, this approach has been found to be acceptably accurate
for a first approximation during the design process. The damping in these kinds of mechanical
systems can vary quite widely from one design to the next due to different geometries,
pressure or transmission angles, types of bearings, lubricants or their absence,
etc. It is very difficult to accurately predict the level of damping (i.e., the value of c) in
advance of the construction and testing of a prototype, which is the best way to determine
the damping coefficient. If similar devices have been built and tested, their history can
provide a good prediction. For the purpose of our dynamic modeling, we will assume
pseudo-viscous damping and some value for c.
If we combine these three fonus of damping, their sum will look like Figure 1O-5dand e. This is obviously a nonlinear function. But we can approximate it over a reasonablysmall range of velocity as a linear function with a slope c which is then a pseudoviscousdamping coefficient. This is shown in Figure 1O-5f. While not an exact methodto account for the true damping, this approach has been found to be acceptably accuratefor a first approximation during the design process. The damping in these kinds of mechanicalsystems can vary quite widely from one design to the next due to different geometries,pressure or transmission angles, types of bearings, lubricants or their absence,etc. It is very difficult to accurately predict the level of damping (i.e., the value of c) inadvance of the construction and testing of a prototype, which is the best way to determinethe damping coefficient. If similar devices have been built and tested, their history canprovide a good prediction. For the purpose of our dynamic modeling, we will assumepseudo-viscous damping and some value for c.
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