说明：  等腰三角波发生器，在simulink 中有的是锯齿波和三角波的现成模块，可是等腰三角波的就没有了，现提供给大家。
(isosceles triangular wave generator, which in some Simulink ramp and triangular wave off-the-shelf modules, But isosceles triangle wave, there is no, it is available to everyone.)