Abstract
By the technique of Bogolybov asymptotic method the author clarified the nonlinear gain characteristic necessary to reduce the system to hard oscillation system. When the system contains such a nonlinear gain element as reducing the system to hard oscillation system, the system may comes up to stable system, to hard oscillation system or to soft oscillation system according to the value of linear gain constant. When the gain constant is adjusted to a value which causes hard oscillation, the system in the stationary state will begin to oscillate by the reception of step input of magnitude within certain range and the existing oscillation will die out by the reception of step input of magnitude within certain another range at the proper instant. The author revealed that it is possible to cause the start or stop of oscillation not accompanied with any transient phenomena by selecting the magnitude of step input properly in each case. The electronic simulation experiments are also made.
