具有不稳定零极点对消的结构图等效问题

为进一步完善经典控制论中的结构图简化规则，深入研究具有不稳定零极点对消的结构图等效问题。指出复杂结构图等效后，如果其等效式与其他环节存在不稳定零极点对消，则对消后系统的性质将发生改变，此时应保持原结构图而不做进一步的简化，仿真示例验证这一结论。

Problem of Block Diagram Algebra with Unstable Pole-zero Cancellation

In order to complement block diagram algebra rules in the classical control theory, further research on block diagram reducing problem is conducted with unstable pole-zero cancellation. The experiment shows that if the corresponding zeroes and poles belonging to different blocks of a complicated system are canceled, the stability of which might be changed immediately. This phenomenon should be considered and included in block diagram algebra rules of the classical control theory. The simulating results make the conclusion that maintaining the previous structure of the complex system is necessary to the equivalent process. Details of the comparison and the simulating curves are presented in the paper.