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Thanks.<br> <BR><div><hr id="stopSpelling">Date: Wed, 1 Aug 2012 14:59:35 +0200<br>From: vogt@centre-cired.fr<br>To: users@lists.scilab.org<br>Subject: Re: [scilab-Users] Converting from continuous to discrete time tranfer function.<br><br>
<div class="ecxmoz-cite-prefix">On 25/07/2012 00:16, steven hallacy
wrote:<br>
</div>
<blockquote cite="mid:SNT143-W5030C5CB9AF87F111DD2B8AFDC0@phx.gbl">
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Hello,<br>
<br>
With Scilab, I know of two ways of converting from a continuous
time transfer function (e.g. 1/s) to a discrete time transfer
funtion:<br>
<span style="color: rgb(0, 0, 0);"></span> <br>
<span style="color: rgb(0, 0, 0);">1st way:</span><br>
<span style="color: rgb(0, 0, 0);">s</span><span style="color: rgb(92, 92, 92);">=</span><span style="color: rgb(50, 185, 185);">poly</span><span style="color: rgb(74, 85, 219);">(</span><span style="color: rgb(188, 143, 143);">0</span><span style="color: rgb(0, 0, 0);">,</span><span style="color: rgb(188, 143, 143);">'</span><span style="color: rgb(188, 143, 143);">s</span><span style="color: rgb(188, 143, 143);">'</span><span style="color: rgb(74, 85, 219);">)</span><br>
<span style="color: rgb(174, 92, 176); text-decoration: underline;">ss2tf</span><span style="color: rgb(74, 85, 219);">(</span><span style="color: rgb(174, 92, 176); text-decoration: underline;">cls2dls</span><span style="color: rgb(74, 85, 219);">(</span><span style="color: rgb(174, 92, 176); text-decoration: underline;">tf2ss</span><span style="color: rgb(74, 85, 219);">(</span><span style="color: rgb(174, 92, 176); text-decoration: underline;">syslin</span><span style="color: rgb(74, 85, 219);">(</span><span style="color: rgb(188, 143, 143);">'</span><span style="color: rgb(188, 143, 143);">c</span><span style="color: rgb(188, 143, 143);">'</span><span style="color: rgb(0, 0, 0);">,</span><span style="color: rgb(188, 143, 143);">1</span><span style="color: rgb(92, 92, 92);">/</span><span style="color: rgb(0, 0, 0);">s</span><span style="color: rgb(74, 85, 219);">)</span><span style="color: rgb(74, 85, 219);">)</span><span style="color: rgb(0, 0, 0);">,</span><span style="color: rgb(188, 143, 143);">0.1</span><span style="color: rgb(74, 85, 219);">)</span><span style="color: rgb(74, 85, 219);">)</span>
<br>
<br>
This way requires a lot of typing.<br>
<span style="color: rgb(0, 0, 0);"></span> <br>
<span style="color: rgb(0, 0, 0);">2nd Way:</span><br>
<span style="color: rgb(0, 0, 0);"><span style="color: rgb(0, 0, 0);">s</span><span style="color: rgb(92, 92, 92);">=</span><span style="color: rgb(50, 185, 185);">poly</span><span style="color: rgb(74, 85, 219);">(</span><span style="color: rgb(188, 143, 143);">0</span><span style="color: rgb(0, 0, 0);">,</span><span style="color: rgb(188, 143, 143);">'</span><span style="color: rgb(188, 143, 143);">s</span><span style="color: rgb(188, 143, 143);">'</span><span style="color: rgb(74, 85, 219);">)</span><span style="color: rgb(0, 0, 0);">;</span><span style="color: rgb(0, 0, 0);">z</span><span style="color: rgb(92, 92, 92);">=</span><span style="color: rgb(50, 185, 185);">poly</span><span style="color: rgb(74, 85, 219);">(</span><span style="color: rgb(188, 143, 143);">0</span><span style="color: rgb(0, 0, 0);">,</span><span style="color: rgb(188, 143, 143);">'</span><span style="color: rgb(188, 143, 143);">z</span><span style="color: rgb(188, 143, 143);">'</span><span style="color: rgb(74, 85, 219);">)</span><span style="color: rgb(0, 0, 0);">;</span></span><br>
<span style="color: rgb(0, 0, 0);">sl</span><span style="color: rgb(92, 92, 92);">=</span><span style="color: rgb(174, 92, 176); text-decoration: underline;">syslin</span><span style="color: rgb(74, 85, 219);">(</span><span style="color: rgb(188, 143, 143);">'</span><span style="color: rgb(188, 143, 143);">c</span><span style="color: rgb(188, 143, 143);">'</span><span style="color: rgb(0, 0, 0);">,</span><span style="color: rgb(188, 143, 143);">1</span><span style="color: rgb(92, 92, 92);">/</span><span style="color: rgb(0, 0, 0);">s</span><span style="color: rgb(74, 85, 219);">)</span><span style="color: rgb(0, 0, 0);">;</span>
<span style="color: rgb(0, 0, 0);"></span><br>
<span style="color: rgb(0, 0, 0);">sl2</span><span style="color: rgb(92, 92, 92);">=</span><span style="color: rgb(174, 92, 176); text-decoration: underline;">horner</span><span style="color: rgb(74, 85, 219);">(</span><span style="color: rgb(0, 0, 0);">sl</span><span style="color: rgb(0, 0, 0);">,</span><span style="color: rgb(74, 85, 219);">(</span><span style="color: rgb(188, 143, 143);">2</span><span style="color: rgb(92, 92, 92);">/</span><span style="color: rgb(188, 143, 143);">0.1</span><span style="color: rgb(74, 85, 219);">)</span><span style="color: rgb(92, 92, 92);">*</span><span style="color: rgb(74, 85, 219);">(</span><span style="color: rgb(0, 0, 0);">z</span><span style="color: rgb(92, 92, 92);">-</span><span style="color: rgb(188, 143, 143);">1</span><span style="color: rgb(74, 85, 219);">)</span><span style="color: rgb(92, 92, 92);">/</span><span style="color: rgb(74, 85, 219);">(</span><span style="color: rgb(0, 0, 0);">z</span><span style="color: rgb(92, 92, 92);">+</span><span style="color: rgb(188, 143, 143);">1</span><span style="color: rgb(74, 85, 219);">)</span><span style="color: rgb(74, 85, 219);">)</span><br>
<br>
This way requires me to remember the tustin approximation.<br>
<br>
Does matlab have anything like Matlab's c2d function?<br>
<br>
Stephen<br>
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</blockquote>
Hi<br>
<br>
Did you try defining it yourself?<br>
<br>
function y=c2d(x,p)<br>
<br>
if argn(2)<2<br>
p=0.1<br>
end<br>
<br>
<br>
<span style="color: rgb(174, 92, 176); text-decoration: underline;"> y=
ss2tf</span><span style="color: rgb(74, 85, 219);">(</span><span style="color: rgb(174, 92, 176); text-decoration: underline;">cls2dls</span><span style="color: rgb(74, 85, 219);">(</span><span style="color: rgb(174, 92, 176); text-decoration: underline;">tf2ss</span><span style="color: rgb(74, 85, 219);">(</span><span style="color: rgb(174, 92, 176); text-decoration: underline;">syslin</span><span style="color: rgb(74, 85, 219);">(</span><span style="color: rgb(188, 143, 143);">'</span><span style="color: rgb(188, 143, 143);">c</span><span style="color: rgb(188, 143, 143);">'</span><span style="color: rgb(0, 0, 0);">,</span><span style="color: rgb(188, 143, 143);">x</span><span style="color: rgb(74, 85, 219);">)</span><span style="color: rgb(74, 85, 219);">)</span><span style="color: rgb(0, 0, 0);">,</span><span style="color: rgb(188, 143, 143);">p</span><span style="color: rgb(74, 85, 219);">)</span><span style="color: rgb(74, 85, 219);">)</span>
<br>
endfunction<br>
<br>
<span style="color: rgb(0, 0, 0);">s</span><span style="color: rgb(92, 92, 92);">=</span><span style="color: rgb(50, 185, 185);">poly</span><span style="color: rgb(74, 85, 219);">(</span><span style="color: rgb(188, 143, 143);">0</span><span style="color: rgb(0, 0, 0);">,</span><span style="color: rgb(188, 143, 143);">'</span><span style="color: rgb(188, 143, 143);">s</span><span style="color: rgb(188, 143, 143);">'</span><span style="color: rgb(74, 85, 219);">)</span><br>
c2d(1/s)<br>
<br>
<br>
you can do similar stuff each time you use something that requires
lots of typing<br>
<br>
BR<br>
AVS<br></div> </div></body>
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