An Investigation of Slider Vibrations in Near Contact Recording Using a Digital Laser Doppler Vibrometer

2003 ◽  
Vol 125 (3) ◽  
pp. 571-575 ◽  
Author(s):  
Shinji Yonemura ◽  
Lin Zhou ◽  
Frank E. Talke
Keyword(s):  
Noise Level ◽  
Laser Doppler Vibrometer ◽  
Laser Doppler ◽  
Flying Height ◽  
Design Consideration ◽  
Skew Angle ◽  
Torsion Mode ◽  
And Control ◽  
Contact Recording ◽  
Important Design

At a flying height of 10 nanometers, contacts between slider and disk are likely to occur, and control of contact-induced slider vibrations is an important design consideration. In this study, slider vibrations during contact are investigated using a digital laser Doppler vibrometer (LDV). The noise level of the digital interferometer is compared with that of a conventional analog LDV. In addition, acoustic emission (AE) sensors are used to evaluate the contact behavior of the slider. A comparison of AE and LDV data is performed. The results show that the noise level of the digital LDV is lower than that of the analog LDV, and that suspension sway mode vibrations and torsion mode vibrations are excited during contact as a function of the skew angle.

Heater AC Voltage Induced Flying Height Modulations

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Wei Hua ◽  
Kang Kee Ng ◽  
Shengkai Yu ◽  
Weidong Zhou ◽  
Kyaw Sett Myo
Keyword(s):  
Electrostatic Force ◽  
Laser Doppler Vibrometer ◽  
Drive Level ◽  
Flying Height ◽  
Air Bearing ◽  
Skew Angle ◽  
Frequency Method ◽  
Disk Interface ◽  
Height Control ◽  
Disk Contact

For a thermal flying-height control (TFC) slider, its heater is usually provided with DC voltage. However, recently, both DC and AC voltages may be supplied to the heater. Unlike supplying AC voltage to the slider and disk in the past, the AC voltage to the heater will not only produce a thermal protrusion on the slider, but also leaves a part of the AC voltage on the slider/disk interface. The voltage acts as the electrostatic force and can be used for further control of the slider, even in the drive level. Simulations show that the flying height modulation is highly related to the AC frequency. By sweeping the AC frequencies while monitoring the flying height and pitch angle modulations, the first and second pitch modes of air bearing frequencies can be experimentally obtained without slider/disk contact. The roll mode frequency is also obtainable when the skew angle is not zero. The simulation results agree well with the experimental results obtained by a laser Doppler vibrometer (LDV). Therefore, the sweeping AC frequency method provides a practical scheme to obtain the air bearing frequencies without any slider/disk contact, even in the drive level.

Effect of Lubricant on Flyability and Read-Write Performance in the Ultra-Low Flying Regime

2001 ◽  
Vol 124 (2) ◽  
pp. 259-265 ◽  
Author(s):  
Xiaoding Ma ◽  
David Kuo ◽  
Jianping Chen ◽  
Huan Tang ◽  
Jing Gui
Keyword(s):  
Acoustic Emission ◽  
Laser Doppler Vibrometer ◽  
Disk Surface ◽  
Laser Doppler ◽  
The Other ◽  
Flying Height ◽  
Magnetic Spacing ◽  
Instability Characteristic ◽  
Step Thickness

The effect of lubricant on flyability and read-write performance in ultra-low flying regime has been studied over the disks with lubricant on one half of disk surface thicker than the other half. The dynamics of a slider was monitored using Acoustic Emission (AE) and Laser Doppler Vibrometer (LDV). An instability characteristic of a slider flying over the thick lubricant region has been observed and this instability intensifies as flying height decreases and the step thickness increases. After the slider flies over the disks, it has been found that lubricant re-distribution occurs as lubricant is “carried” by the flying slider from the thick lubricant region and deposited onto the thin lubricant region. Possible mechanisms were discussed to explain the observations. Finally, recording tests were performed and the magnetic spacing loss due to the lubricant steps was estimated.

scholarly journals Using a Retro-Reflective Membrane and Laser Doppler Vibrometer for Real-Time Remote Acoustic Sensing and Control

Sensors ◽  
2021 ◽  
Vol 21 (11) ◽  
pp. 3866
Author(s):  
Tong Xiao ◽  
Sipei Zhao ◽  
Xiaojun Qiu ◽  
Benjamin Halkon
Keyword(s):  
Active Noise Control ◽  
Laser Doppler Vibrometer ◽  
Sound Field ◽  
Laser Doppler ◽  
Remote Measurement ◽  
Control Applications ◽  
Acoustic Sensing ◽  
Minimal Invasiveness ◽  
Wide Range ◽  
And Control

Microphones have been extensively studied for many decades and their related theories are well-established. However, the physical presence of the sensor itself limits its practicality in many sound field control applications. Laser Doppler vibrometers (LDVs) are commonly used for the remote measurement of surface vibration that are related to the sound field without the introduction of any such physical intervention. This paper investigates the performance and challenges of using a piece of retro-reflective film directly as an acoustic membrane pick-up with an LDV to sense its vibration to form a remote acoustic sensing apparatus. Due to the special properties of the retro-reflective material, the LDV beam can be projected to the target over a wide range of incident angles. Thus, the location of the LDV relative to the pick-up is not severely restricted. This is favourable in many acoustic sensing and control applications. Theoretical analysis and systematic experiments were conducted on the membrane to characterise its performance. One design has been selected for sensing sound pressure level above 20 dB and within the 200 Hz to 4 kHz frequency range. Two example applications—remote speech signal sensing/recording and an active noise control headrest—are presented to demonstrate the benefits of such a remote acoustic sensing apparatus with the retro-reflective material. Particularly, a significant 22.4 dB noise reduction ranging from 300 Hz to 6 kHz has been achieved using the demonstrated active control system. These results demonstrate the potential for such a solution with several key advantages in many applications over traditional microphones, primarily due to its minimal invasiveness.

Skew angle and off-track capability of near contact recording systems

1996 ◽  
Vol 32 (5) ◽  
pp. 3866-3868 ◽  
Author(s):  
Sheng-Bin Hu ◽  
Bo Liu ◽  
Teck-Seng Low
Keyword(s):  
Skew Angle ◽  
Contact Recording
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