Portunus怪问题之一：Singular matrix.

1.1 当主模块的architecture内有多余的

  terminal shaft, rotational  : rotational_v;

就始终报错：

20128: Singular matrix.

20127: The equation system could not be solved at time (t=1e-006s).

02093: Error on simulating.

Simulation aborted. 3 error(s). 0 warning(s).

必须去掉多余的terminal

1.2 当testbench里的architecture内有多余的：

    terminal t1,t2,t3: electrical;

就始终报错：

20128: Singular matrix.

20127: The equation system could not be solved at time (t=1e-006s).

02093: Error on simulating.

Simulation aborted. 3 error(s). 0 warning(s).

必须去掉多余的terminal