| Summary: | 碩士 === 國立清華大學 === 動力機械工程學系 === 88 === In many kinds of the automatic balancers, the ball balancer has the advantages of simple in construction, easily to assemble and high capacity to compensate automatically for the unbalance of a rotor above the critical speed. However, experimental results show that the ball balancer applied to the optical-disk drive has the characteristic of low consistence in locating the balls at right positions. To understand the reasons for low consistence, a mathematical model is first constructed for the purpose of theoretically investigating the dynamic behaviors of the foundation and balancing balls. Therefore, the positions of the balls at steady state can be predicted. Herein, the steady state indicates that the speed of the spindle motor runs constantly and there is no relative motion between balls and the balancer. Then, the method of multiple scale is employed to analyze the stability of the balancer with two balls at steady state. Finally, an experimental setup is constructed to examine the correctness of the mathematical model and computer simulation of the steady-state solutions and their stability. Good agreement has been obtained. This research also leads to several design guidelines for the ball balancer in improving the consistence of ball positions and, therefore, reducing vibration resulting from unbalance of the rotor.
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