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MATLAB求拉氏逆变换的问题

dreammeir 发布于 2009-07-28 08:25， 2596 次点击
我不懂matlab，但想用它求一下拉氏逆变换，可求得的结果，看不懂，敬请高人指点：
注：它有三个特征根：其中1个实根，两个共轭复根
>> syms s;
>> ilaplace((s^2+256*s+83.3)/(s^3+36*s^2+26.6*s+83.3))
 
ans =
 
-1/961113601*sum((9487060*_alpha^2-3461988103+65712985*_alpha)*exp(_alpha*t),_alpha = RootOf(10*_Z^3+360*_Z^2+266*_Z+833))
2 回复
#2
dreammeir2009-07-28 10:34
后来又这样算
后又改如下方式，结果如下：
>> F=sym('(s^2+256*s+83.3)/(s^3+36*s^2+26.6*s+83.3)');
>> ft=ilaplace(F)
 
ft =
 
-6.2929694418705059118508883314873*exp(-35.313545800725236441622910891424*t)+7.2929694418705059118508883314873*exp(-.34322709963738177918854455428817*t)*cos(1.4970181534921276621150716871639*t)+.18442003563872051633497396365708*exp(-.34322709963738177918854455428817*t)*sin(1.4970181534921276621150716871639*t)-.10404597322933941083620145335973e-8*i*(-88624302.274639505243643074225846*exp(-.34322709963738177918854455428817*t)*cos(1.4970181534921276621150716871639*t)+3504686061.1295610563153979296622*exp(-.34322709963738177918854455428817*t)*sin(1.4970181534921276621150716871639*t))-.10404597322933941083620145335973e-8*i*(88624302.274639505243643074225846*exp(-.34322709963738177918854455428817*t)*cos(1.4970181534921276621150716871639*t)-3504686061.1295610563153979296622*exp(-.34322709963738177918854455428817*t)*sin(1.4970181534921276621150716871639*t))
但不懂e-8*i*(...)在matlab中是什么意思？
#3
孢子2009-09-09 09:29
_alpha = RootOf(10*_Z^3+360*_Z^2+266*_Z+833)) 这是说alpha是后面方程的根。
e-8*i*(...)是说*10^(-8)*i*(…），i为虚数
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