只需要一个时钟控件，以很短的时间触发，本程序采用30ms，作为本程序的工作频率。降低频率：多个时间间隔后，运行一次。速度变化，在时间间隔内，变化不同值。-Only need a clock control to a very short time-triggered, the program uses 30ms, as the frequency of this procedure. Lower frequency: more than one time interval, run time. Speed ??changes in the time interval, changes in different values.