Merged with duplicate record 10026.1/829 on 10.04.2017 by CS (TIS)Three readback signal detection methods are investigated for real-time flying height or
head disk spacing variation measurement under vibration conditions. This is carried out
by theoretical analysis, numerical simulation, and experimental study. The first method
(amplitude detection) provides a simple way to study the head disk spacing change. The
second method ( PW50 parameter estimation) can be used effectively for real-time
spacing variation measurement in normally operated hard disk drives, primarily in low
frequency spacing variation conditions. The third method (thermal signal detection), on
the other hand, is more effective and suitable for high frequency spacing variation
measurement. By combining the PW50 estimation and thermal signal detection
methods, a noval spacing variation detection method for the whole frequency range is
constructed. This combined signal detection method not only has been used to study the
head disk spacing variation itself, but also has the potential of being used for real time
flying height control.
Analytical models are developed for head disk assembly and head position servo control
mechanisms to analyse the operation failure of hard disk drives under vibration
conditions. Theoretical analysis and numerical simulation show their good agreement
with experimental results.
A novel active flying height control method is proposed to suppress the flying height or
head-disk spacing variation in hard disk drives under vibration conditions. Simulation
results show that this active flying height control can effectively suppress the head-disk
spacing variation, therefore the performance and reliability of HDDs can be well
improved when working in vibration conditions: The method has a good potential to be
applied to future ruggedized hard disk drives