在做现代控制理论极点配置实验时，MATLAB出现了如下错误， 请问是怎么回事，请高手指点，如何改正，错误出

a=[0 1;2 3]
>> b=[0 1]'
>> c=[1 0];
>> d=[0];
>> sx=[-1 -1]

sx =

-1 -1

>> [k,prec,message]=place(a,b,sx)
??? Error using ==> place at 79
The "place" command cannot place poles with multiplicity greater than rank(B).

>> place(a,b,sx);
??? Error using ==> place at 79
The "place" command cannot place poles with multiplicity greater than rank(B).

应该是矩阵a的秩为1导致的；

不过若用acker函数则有结果

>> K=acker(a,b,sx)

K=

3 5

呵呵，LZ科大的？