说明：  现在的滑模控制都是基于计算机实现的，如何很好地实现离散滑模控制也非常重要，这个程序很有参考价值，基于离散滑模的位置跟踪控制
(Now the sliding mode control are based on the computer, and realize how well discrete sliding mode control is also very important that this process is the reference value, based on the location of discrete sliding mode tracking control)