H ( subscript ∞ ) norm a kind of induced norm and satisfies the multiplicative property . in robust control it is convenient to represent the unstructured model uncertainty by H ( subscript ∞ ) norm .系统的H(下标∞)范数是诱导范数,它满足乘法特性,利用H(下标∞)范数可以方便地引入系统的非结构不确定性,进行