buffers

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buffers

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Buffers are bond graph elements that can store energy. There are two types of buffers: C-elements and I-elements. The table below shows the effort and flow descriptions that belong to these elements. The parameters "C" and "I" are the bufferconstants, which determine a linear buffer behavior. Examples of C-elements are a mechanical spring and an electrical capacitor. Examples of an I-element are a mechanical inertia and an electrical inductance.

 

C-element

bond graph element

equation

effort-in causality

CElementEffortIn

f = C de/dt

effort-out causality

CElementEffortOut

e = (1/C) int(f)

I-element

bond graph element

equation

effort-in causality

IElementEffortIn

f = (1/I) int(e)

effort-out causality

IEementEffortOut

e = I df/dt

 

Buffer elements do not fix the direction of the effort and flow. Both effort-in as well as effort-out causality is allowed. With simulation however, we prefer to avoid differentiation. in other words, with the C-element the effort-out causality is preferred and with the I-element the effort-in causality is preferred.