Digital Control Systems: Difference between revisions

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*Convolution and Z Transforms
*Convolution and Z Transforms
**[http://www.ualberta.ca/~msacchi/GEOPH426/chapter2.pdf Z Transforms and Convolution]
**[http://www.ualberta.ca/~msacchi/GEOPH426/chapter2.pdf Z Transforms and Convolution]
**[http://www-rohan.sdsu.edu/~jiracek/DAGSAW/4.3.html Here is an animation of discrete convolution.] To convolve <math>x(t)</math> with <math>h(t)</math>, you flip shift <math>h(t)</math> into <math>h(t-t_0)</math> on the <math>t_0</math> axis, then you multiply it by <math>x(t_0)</math> to get <math>x(t_0)h(t-t_0)</math>, then you integrate with respect to <math>t_0</math>, so that the convolution is: <math>x(t) * h(t) = \int_{-\infty}^\infty x(t_0)h(t-t_0) dt_0</math>. The animation shows this happening with sampled waveforms: <math>x_s(t) = x(t) \sum_{n=0}^\infty \delta (t-nT) = \sum_{n=0}^\infty x(nT) \delta (t-nT)</math> and <math>h_s(t) = h(t) \sum_{n=0}^\infty \delta (t-nT)= \sum_{n=0}^\infty h(nT) \delta (t-nT)</math>.
**[http://www.jhu.edu/signals/convolve/index.html Here is an animation of convolution with continuous signals.] Look at it so you understand what is happening with the mechanics of convolution. To convolve <math>x(t)</math> with <math>h(t)</math>, you flip shift <math>h(t)</math> into <math>h(t-t_0)</math> on the <math>t_0</math> axis, then you multiply it by <math>x(t_0)</math> to get <math>x(t_0)h(t-t_0)</math>, then you integrate with respect to <math>t_0</math>, so that the convolution is: <math>x(t) * h(t) = \int_{-\infty}^\infty x(t_0)h(t-t_0) dt_0</math>. The animation shows this happening with sampled waveforms: <math>x_s(t) = x(t) \sum_{n=0}^\infty \delta (t-nT) = \sum_{n=0}^\infty x(nT) \delta (t-nT)</math> and <math>h_s(t) = h(t) \sum_{n=0}^\infty \delta (t-nT)= \sum_{n=0}^\infty h(nT) \delta (t-nT)</math>.
***More discrete convolution animations
***Discrete convolution animations
****[http://www-rohan.sdsu.edu/~jiracek/DAGSAW/4.3.html Here is an animation of discrete convolution to illustrate the above equations.]
****[http://www.jhu.edu/signals/discreteconv2/index.html This one lets you try several functions.]
****[http://www.jhu.edu/signals/discreteconv2/index.html This one lets you try several functions.]
****[http://www.cse.yorku.ca/~asif/spc/ConvolutionSum_Final3.swf This one shows what happens if your signals happen prior to time zero.]
****[http://www.cse.yorku.ca/~asif/spc/ConvolutionSum_Final3.swf This one shows what happens if your signals happen prior to time zero.]

Revision as of 13:46, 8 April 2014

Links

MATLAB/Octave

Z Transforms