在编写S-function时报错。
error occurred while running the simulation and the simulation was terminated Caused by: Output returned by S-function ‘cassie’ in ‘basic9/Cassie arc model sfunction/S-Function’ during flag=3 call must be a real vector of length 1
可能的错误因素：
- 输出元素个数和你的定义输出个数不同；
- s-function的输入变量个数和与其连接的模块的输入变量个数不一致；
- 还有一种可能是输出为无穷，也就是除以0了；
- S-function的输入变量的维数不是1维的向量；