At this point, the designer begins to introduce controller functions ( G ( s ) {\displaystyle G(s)} ) and tune their parameters, a process called Loop Shaping, until the best possible controller is reached without violation of the frequency constraints.
此時，設計者會導入控制器函數（ G ( s ) {\displaystyle G(s)} ）並且調適其參數，此一程序稱為迴路整形（Loop Shaping），直到找到了在不違背頻率限制條件下，最理想的控制器為止。