Masatsugu Otsuki

This paper presents a vibration control method for a wire with time-varying length such as an elevator cable and a crane wire. The characteristics of moving wire are varying with time. When the wire is approximately modeled with such a method as FEM, it is possible to cause a spillover due to the ignored high order modes. Therefore, the robustness for the variation of tension, spillover of high order modes and rapid change of disturbance is important and a robust nonstationary control method is proposed by applying nonstationary H-infinity control theory in this study. For the moving wire such as crane string and elevator cable, it is possible to reduce the vibration by using only a nonstationary robust controller for the case that the mass at the tip of wire changes its weight, that is, the tension of wire varies. The robust controller then is designed based on a lower order model of wire with the frequency weightings. As a result, in the numerical calculations we show the robustness and the usefulness of the robust controllers are shown.

This study presents a synthesis method of a nonstationary optimal controller with a time-varying criterion function for reducing vibration of a time-varying object such as rope of elevator and crane. Moreover, from the viewpoint of wave propagation, we also propose a method of reducing vibration with wave-absorbing controller to remove the reflected waves. As an illustration, the performance of reducing vibration with respect to the rope-sway problem on a high-rise building is examined through numerical calculation. These nonstationary optimal and wave-absorbing controllers are compared with the stationary optimal controller in case that the structure is subjected to Kobe earthquake.

This paper develops an approach for the control of the motion of a multiple-link manipulator possessing unactuated joints. A three-rigid-link arm with its shoulder joint actuated and two elbow joints unactuated is modeled as a nonlinear Affine system. The system is a case of second-order nonholonomy since the constraints at the passive joints contain terms of accelerations. In the proposed method to solve the problem of optimal positioning the control input is expressed as a general function of a Fourier basis parameter acquired by using the Ritz method; then this parameter is optimized through the application of the Newton method. Numerical simulations were carried out and tests with an experimental setting demonstrate the effectiveness of the approach.