AbstractThe purpose of the paper is to investigate the problem of the delayed active control of a linear system controlled by a closed‐loop linear law under the action of external dynamic forces. The choice of the optimal parameters, for each assigned delay, is pursued through the optimization of the controlled response with the constraint of limiting the control force under a prefixed threshold. The behaviour of the response, varying the control parameters, is investigated through the mapping of the “solution in the norm” of the response rather than the definition of the punctual response of the system.Numerical applications for different values of the delay are performed for a SDOF structure showing the range of the feasibility of the closed‐loop linear approach on one side, and proving the critical role of the delay on the oth