Abstract: The control problem of characteristic model with unknown input delay is studied. Using the method of directly solving the roots of the closedloop system, the results show that the minimumvariance controller is not robust to unknown input delay, the prototype goldensection controller can deal with small input delay, and the λ type goldensection controller can deal with larger input delay. Considering a stable, oscillating, unstable twointegrator characteristic model, the stability and robustness performance of the closedloop system are further analyzed respectively for the prototype and the λ type goldensection controller with unknown input delay. For stable controlled plant, the λ type goldensection controller is tolerable with large input delay, and the closedloop system performance is basically unchanged. For unstable plant, the λ type goldensection controller can improve the stability and performance by optimizing λ.

Key words: characteristic model, goldensection control