Adaptive filtering for the external and cross vibration
Original Publication Date: 2001-Oct-11
Included in the Prior Art Database: 2003-Jun-20
Currently there is just a retry operation applied or the fixed filtering is applied for Hard Disk Drive (HDD). This is not fit in the actual worse environment like external vibration or the cross vibration induced. During the error recovery procedure(ERP), measure the servo PES stability with frequency to find the external or the cross vibration frequency. If there is unique frequency which characteristics are different from the measured value during the manufacturing test, then additional filtering will be applied to prevent the temporary induced vibration caused by from outside or the cross interfered one. This additional frequency filtering will be worked with only several ERP steps. In the error recovery procedure which sequence will be followed when the target sector has ECC error even with multiple retry, PES stability will be measured on that whole target track and convert to the frequency peaks. Those peaks will be compared with the pre-measured value which was measured during manufacturing test and saved in the disk and transferred to the memory during Power On Reset (POR) sequence. If there is additional peak which exceeds the pre-defined criteria, additional filtering will be applied with that frequency peak temporary. This additional filtering will be applied in several ERP steps but that will continue during reading or writing operation on that track.