In this paper, a combination problem of controllers which are the same type of $H_{infty}$ controllers designed with different weighting functions. This approach can remove the difficulty in the selection of the weighting functions. As a sub-controller, the Youla type of $H_{infty}$ controller is used. In the $H_{infty}$ controller, Youla parameterization is used to minimize $H_{infty}$ norm of mixed sensitivity function by using polynomial approach. Computer simulation results show the robustness improvement and the performance improvement.