振動自由度をもつ機構の位置決め制御に関する基礎的研究 : 第1報,ネガティブフィードバックによる系の不安定性

概要

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Instability phenomenon in feedback positioning mechanisms is well known in magnetic disk equipments, but it seems to the author that a comprehensive explanation of the cause of the instability have not been made. This paper presents a plain explanation of the instability encountered in a simple positioning mechanism which has one degree of vibration freedom in addition to one degree of rigid body freedom, when the negative feedback positioning force applied to one mass is provided by linear combination of the displacement and velocity of another mass. From the modal analysis of the closed system, it is found that although the increase in the negative feedback gain of the displacement increases the natural frequency of the in-phase mode, it decreases the natural frequency of the out-of-phase mode and results in instability. It is also found that the negative feedback of the velocity acts as an unstable damping for the out-of-phase mode.
1987-12-25