constructing bode diagrams

[Jimbo]

Hi

If you have asymptote approximations of a Bode plot - do you just find the vector sum of each asymptote to construct the 'full' bode plot?

I hope that makes sense

Any help much appreciated

Jimbo

[jamesrc]

I'm not quite sure what you mean. Are you talking about adding two Bode plots like when you have two transfer functions in series? Maybe you're breaking up the polynomial into its constituent parts; that's the same difference. When multiplying these terms together, the result is addition on the Bode plot. Say you have
H(s) = \frac{K(s+1)}{s}

You can break that up into an integrater (pole at the origin), a zero at s = -1, and a constant (gain) multiplier K. Draw the Bode plot for each component and sum together to find the overall Bode plot.

If you're talking about getting the actual Bode plot from the straight-line approximation, that's a different question. You can put in accuracy points to help you draw the curves or you could plot it exactly using something like MATLAB.