perf

代码说明：

   求系统单位节约给定相应的性能指标（超调量，峰值时间，调整时间），其中key=1表5 超调量 key=2表2 的超调量，y，t表示系统节约相应的函数值与其对应时间(Demand units to save the system give the corresponding performance indicators (overshoot, peak time, adjusting the time), where key = 1 Table 5 percent overshoot key = 2 Table 2 overshoot, y, t that the system saves the corresponding function value and its corresponding time)