Servo signal processing for flying height control in hard disk drives

Abstract

A novel method of measuring the relative headmedium spacing based on a measurement in the servo sectors is developed and simulated using a read back signal model. The spacing measurement is tested experimentally on a spin stand where the flying height is varied using the resistance heater element in a thermal flying height control slider. In addition, voltage step response measurements were obtained. The data were used to perform system identification and estimate the dynamics of the thermal actuator. The model can potentially be used for thermal flying height control.

<i>In Situ</i> Spacing Fluctuation Monitoring of Hard Disk Drive with Thermal Asperity Sensors

“…However, due to the large apparatus and cost, it is impossible to put it into use in a real HDD. Reading-back signal of reading transducer, either data signal or servo signal is also used for spacing measurement [3], but it is easily affected by head off-track disturbance.…”

Analytical read back signal modeling in magnetic recording

“…Figure 7 shows the computed read back signal for the following assumed parameters: The bit dimensions were defined as L ¼ 170 nm; W ¼ 80 nm; T ¼ 20 nm; r ¼ 0 nm and reader parameter were assumed as w ¼ 60 nm; g ¼ 30 nm; t ¼ 10 nm: Figure 6 shows the simulated read back signal based on the above parameters for a ''16T''-type pattern that is used in the experimental section in Boettcher et al (2011). The 16T pattern consists of 8 ''up''-magnetized bits followed by 8 ''down''-magnetized bits.…”