Let's check our result by comparing the transfer function from the input force to the force on the mass in both the discrete- and continuous-time cases.

For the discrete-time case, we have

where the last simplification comes from the mass reflectance relation . (Note that we are using the standard traveling-wave notation for the

We now need . To simplify notation, define the two coefficients as

From Figure F.32, we can write

Thus, the desired transfer function is

We now wish to compare this result to the bilinear transform of the
corresponding analog transfer function. From Figure F.29, we
can recognize the mass and dashpot as
*voltage divider*:

Applying the bilinear transform yields

Thus, we have verified that the force transfer-function from the driving force to the mass is identical in the discrete- and continuous-time models, except for the bilinear transform frequency warping in the discrete-time case.

[How to cite this work] [Order a printed hardcopy] [Comment on this page via email]

Copyright ©

Center for Computer Research in Music and Acoustics (CCRMA), Stanford University