[Octave-bug-tracker] [bug #58538] [octave forge] (control) step and lsim fail on high order transfer functions

[Nicholas Jankowski]

Follow-up Comment #5, bug #58538 (project octave):

(adding details from the mailing list)
running step and lsim commands in comment #0  result in the following warning
being displayed repeatedly (for step, it appears every time the figure is
given focus until a ctrl-c)

warning: opengl_renderer: data values greater than float capacity.  (1) Scale
data, or (2) Use gnuplot

switching to gnuplot results in the output attached as file
OctaveControlGnuplot.png 

looking at the output from Torsten's tests:

output on Octave:

>> pkg load control
>> q=tf([  -1.46668928632582  38.5234944088261  -1023.42433722006 
18055.8729050165  -275471.128598611  3680685.32154243  -40413629.6869944 
433109318.542883  -3699840188.09672  32827566143.7738  -225798332168.488 
1689921426466.71  -9494747382069.7  60613579740811.5  -278626623858487 
1.52747193482069e+15  -5.6883783399098e+15  2.69067309068308e+16 
-7.92226372994905e+16  3.25360727881732e+17  -7.2059792475876e+17 
2.61175754638012e+18  -3.8909506684981e+18  1.31637705830625e+19 
-9.12640045084024e+18  3.78290213329238e+19  1.41630594163597e+19 
5.02932079881115e+19  1.29547036349465e+20  1.05983336007477e+19 
2.43633391646665e+20  -1.31208497581345e+19  1.04713601706961e+20 
7.83465823853832e+18  ],[  1  17.1698120499521  542.934121038049 
7294.98595152311  126155.971925398  1377306.37948524  16829405.6386297 
152789570.438515  1448656865.6342  11095921096.5808  85365123037.7488 
556372911296.259  3555399791580.02  19799716986834.5  106353561602035 
506292672690482  2.29624277698132e+15  9.31618125768562e+15 
3.56349262092232e+16  1.22398996473335e+17  3.92373264437545e+17 
1.12860046096021e+18  2.99632129507514e+18  7.09934073973815e+18 
1.53176948230893e+19  2.91760427412351e+19  4.97010301791734e+19 
7.33491370510952e+19  9.42777562297368e+19  1.01604047339533e+20 
9.12510568398965e+19  6.44576522525933e+19  3.46367980244933e+19 
1.23309424846899e+19  2.4145011614912e+18  ]);
>> sys_ss_ct = ss (q);
>> sys_dt2   = c2d (sys_ss_ct, 0.01);
>> eig (sys_dt2.a)
ans =

   0.99422 + 0.08037i
   0.99422 - 0.08037i
   0.99346 + 0.07615i
   0.99346 - 0.07615i
   0.99333 + 0.07155i
   0.99333 - 0.07155i
   0.99368 + 0.06688i
   0.99368 - 0.06688i
   0.99488 + 0.00426i
   0.99488 - 0.00426i
   0.99458 + 0.00842i
   0.99458 - 0.00842i
   0.99435 + 0.01262i
   0.99435 - 0.01262i
   0.99443 + 0.01718i
   0.99443 - 0.01718i
   0.99379 + 0.02253i
   0.99379 - 0.02253i
   0.99340 + 0.02768i
   0.99340 - 0.02768i
   0.99335 + 0.03249i
   0.99335 - 0.03249i
   0.99329 + 0.03711i
   0.99329 - 0.03711i
   0.99324 + 0.04174i
   0.99324 - 0.04174i
   0.99327 + 0.04646i
   0.99327 - 0.04646i
   0.99345 + 0.05142i
   0.99345 - 0.05142i
   0.99368 + 0.05637i
   0.99368 - 0.05637i
   0.99406 + 0.06152i
   0.99406 - 0.06152i

>> sys_tf_dt = c2d (q, 0.01);
>> sys_dt1   = ss (sys_tf_dt);
>> eig (sys_dt1.a)
ans =

   1.42735 + 0.92459i
   1.42735 - 0.92459i
   1.17401 + 0.91528i
   1.17401 - 0.91528i
   0.97044 + 0.84467i
   0.97044 - 0.84467i
   0.81966 + 0.74285i
   0.81966 - 0.74285i
   0.70737 + 0.63075i
   0.70737 - 0.63075i
   0.61757 + 0.53082i
   0.61757 - 0.53082i
   0.55208 + 0.43837i
   0.55208 - 0.43837i
   0.50582 + 0.34596i
   0.50582 - 0.34596i
   0.47599 + 0.25501i
   0.47599 - 0.25501i
   0.45893 + 0.16733i
   0.45893 - 0.16733i
   0.45075 + 0.08282i
   0.45075 - 0.08282i
   0.44843 + 0.00000i
   0.79468 + 0.52856i
   0.79468 - 0.52856i
   0.64503 + 0.00000i
   0.93407 + 0.00000i
   1.70651 + 0.84064i
   1.70651 - 0.84064i
   1.96533 + 0.64519i
   1.96533 - 0.64519i
   2.14777 + 0.35049i
   2.14777 - 0.35049i
   2.21291 + 0.00000i

>> diary off




output on Matlab 2020a:

q=tf([  -1.46668928632582  38.5234944088261  -1023.42433722006 
18055.8729050165  -275471.128598611  3680685.32154243  -40413629.6869944 
433109318.542883  -3699840188.09672  32827566143.7738  -225798332168.488 
1689921426466.71  -9494747382069.7  60613579740811.5  -278626623858487 
1.52747193482069e+15  -5.6883783399098e+15  2.69067309068308e+16 
-7.92226372994905e+16  3.25360727881732e+17  -7.2059792475876e+17 
2.61175754638012e+18  -3.8909506684981e+18  1.31637705830625e+19 
-9.12640045084024e+18  3.78290213329238e+19  1.41630594163597e+19 
5.02932079881115e+19  1.29547036349465e+20  1.05983336007477e+19 
2.43633391646665e+20  -1.31208497581345e+19  1.04713601706961e+20 
7.83465823853832e+18  ],[  1  17.1698120499521  542.934121038049 
7294.98595152311  126155.971925398  1377306.37948524  16829405.6386297 
152789570.438515  1448656865.6342  11095921096.5808  85365123037.7488 
556372911296.259  3555399791580.02  19799716986834.5  106353561602035 
506292672690482  2.29624277698132e+15  9.31618125768562e+15 
3.56349262092232e+16  1.22398996473335e+17  3.92373264437545e+17 
1.12860046096021e+18  2.99632129507514e+18  7.09934073973815e+18 
1.53176948230893e+19  2.91760427412351e+19  4.97010301791734e+19 
7.33491370510952e+19  9.42777562297368e+19  1.01604047339533e+20 
9.12510568398965e+19  6.44576522525933e+19  3.46367980244933e+19 
1.23309424846899e+19  2.4145011614912e+18  ]);
sys_ss_ct = ss (q);
sys_dt2   = c2d (sys_ss_ct, 0.01);
eig (sys_dt2.a)

ans =

   0.9942 + 0.0804i
   0.9942 - 0.0804i
   0.9935 + 0.0762i
   0.9935 - 0.0762i
   0.9933 + 0.0716i
   0.9933 - 0.0716i
   0.9937 + 0.0669i
   0.9937 - 0.0669i
   0.9941 + 0.0615i
   0.9941 - 0.0615i
   0.9937 + 0.0564i
   0.9937 - 0.0564i
   0.9935 + 0.0514i
   0.9935 - 0.0514i
   0.9933 + 0.0465i
   0.9933 - 0.0465i
   0.9932 + 0.0417i
   0.9932 - 0.0417i
   0.9933 + 0.0371i
   0.9933 - 0.0371i
   0.9934 + 0.0325i
   0.9934 - 0.0325i
   0.9934 + 0.0277i
   0.9934 - 0.0277i
   0.9938 + 0.0225i
   0.9938 - 0.0225i
   0.9944 + 0.0172i
   0.9944 - 0.0172i
   0.9943 + 0.0126i
   0.9943 - 0.0126i
   0.9946 + 0.0084i
   0.9946 - 0.0084i
   0.9949 + 0.0043i
   0.9949 - 0.0043i

sys_tf_dt = c2d (q, 0.01);
sys_dt1   = ss (sys_tf_dt);
eig (sys_dt1.a)

ans =

   2.0691 + 0.0000i
   2.0125 + 0.2961i
   2.0125 - 0.2961i
   1.8581 + 0.5393i
   1.8581 - 0.5393i
   1.6475 + 0.6911i
   1.6475 - 0.6911i
   1.4552 + 0.7483i
   1.4552 - 0.7483i
   1.2923 + 0.8011i
   1.2923 - 0.8011i
   1.1007 + 0.8116i
   1.1007 - 0.8116i
   0.9311 + 0.7639i
   0.9311 - 0.7639i
   0.8008 + 0.6860i
   0.8008 - 0.6860i
   0.7056 + 0.5990i
   0.7056 - 0.5990i
   0.6352 + 0.5112i
   0.6352 - 0.5112i
   0.5848 + 0.4239i
   0.5848 - 0.4239i
   0.5529 + 0.3406i
   0.5529 - 0.3406i
   0.5346 + 0.2680i
   0.5346 - 0.2680i
   0.5163 + 0.2043i
   0.5163 - 0.2043i
   0.4994 + 0.1373i
   0.4994 - 0.1373i
   0.4897 + 0.0687i
   0.4897 - 0.0687i
   0.4866 + 0.0000i

diary off


(file #49238)
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Additional Item Attachment:

File name: OctaveControlGnuplot.png       Size:110 KB
    <https://savannah.gnu.org/file/OctaveControlGnuplot.png?file_id=49238>



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