| Summary: | The aim of this study is to develop a systematic method to suppress residual vibration in overhead cranes that lowers operating performance and prevents automation of the system. In the previous paper, we proposed a control method which is based on the fact that residual vibration is completely suppressed in a linear undamped system excited by an external force that does not contain the natural frequency component of the system. The proposed method introduces the concept of the apparent external force which includes the influence of nonlinearity and damping, making it applicable to nonlinear damped systems as well as linear undamped ones. One possible drawback is that it needs the value of the natural frequency of a cargo whose on-site high-precision estimation is generally difficult. Therefore, this paper investigates the influence of the estimation error on the residual vibration, which reveals that the residual vibration increases with the estimation error. To improve the robustness against the estimation error, we employ two types of ways. One is to increase the number of frequency components eliminated from the apparent external force and the other is to make the derivatives of the frequency component zero at the estimated natural frequency. Numerical simulations demonstrate the effectiveness of these approaches, showing that they exhibit similar performance in robustness except in that the latter is easier to use since it does not need additional parameters to be determined.
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