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 .系統的H(下標∞)范數是誘導范數,它滿足乘法特性,利用H(下標∞)范數可以方便地引入系統的非結構不確定性,進行