| dc.description.abstract | In a vehicular environment, the DVD drives are apt to be influenced by severe external vibration. Therefore, At our laboratory a modified adaptive hybrid servo controller (MAHC) associated with the robust variable step-size filter-x-least-mean-square (RVSS-FXLMS) was applied to eliminate the focusing and tracking errors at low frequencies from 0 Hz to 100 Hz. However, no matter how the tracking errors under 100 Hz frequency was suppressed, the DVD data-reading still failed since there existed errors at high frequencies. Hence, the sponge was added on the DVD drive to aid MAHC associated with RVSS-FXLMS to eliminate the tracking errors at higher frequencies from 100 Hz to 500 Hz, and then the DVD drive was able to read data well. At the beginning, to explore the causes to make tracking errors large at high frequencies, the balancing balls were suspected. However, this study used a series of experiments to explore exact reasons of the tracking errors at high frequencies. It is found that these errors are generated by structural resonance but not balancing balls on the DVD drive. On the contrary, the balancing balls play an effective role to resolve the unbalanced disk and spindle. In this study, the automatic ball balancer (ABB) dynamic motion equations are derived, and direct computer simulations are carried out. The simulated results confirm that the balancing balls are effective when the unbalanced disk or spindle is operated above the critical speed (ω/ωn=1). Therefore, if the spindle speed of the DVD drives is higher than the structural resonance frequency, the balancing balls will eliminate the tracking errors.
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