The "lqi" command failed to stabilize the plant or find an optimal feedback gain

Hi all,

I got a problem when I tried using lqi command. My system is a discrete system with 8 states, 4 inputs and 4 outputs. All my states are controllable. But when I try to use lqi, it reports :The "lqi" command failed to stabilize the plant or find an optimal feedback gain. To remedy this problem:

1. Make sure that all unstable poles of A are controllable through B (use MINREAL to check)

2. Modify the weights Q and R to make [Q N;N' R] positive definite (use EIG to check positivity).

I think the problem is caused by the cond number. So anyone knows how to deal with it?

Thanks alot