【求助】应用S函数时遇到的问题

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我用S函数搭了一个电机模型,可是开始仿真就会出现一个错误信息,State derivatives returned by S-function 'dianjimx1' in 'chouyouji3/sanxiangyibudianjimoxing/dianji/S-Function' during flag=1 call must be a real vector of length 4,我不明白这句话是说S函数需要返回一个四个长度的实数向量,还是其它意思.