说明：  在控制系统中，由于某些系统不能直接实现所期望的性能，因此需要用系统校正的方法使其具有所期望的性能。本程序是基于频域法的串联校正，分为超前校正和滞后校正。
(In the control system, because some systems can not directly achieve the desired performance, requiring a systematic method of correction to have the desired performance. This procedure is based on the frequency-domain method of series correction, divided into ahead of correction and lag correction.)