Head Disk Interference Sensor Touchdown Detection via AC Heater Phase
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Solution Overview
Problem
Existing disk storage apparatuses face challenges in accurately detecting the touchdown of a head on a disk, which is crucial for setting the optimal flying height for high-density recording, as current methods lack sensitivity and accuracy.
Innovation Solution
A method involving a head disk interference sensor and a heater element that supplies alternating-current heater power, detecting touchdown based on changes in the phase of the sensor's output signal, allowing for precise determination of the operational heater power needed to maintain the target flying height.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a head disk interference sensor is used to detect touchdown, then the head flying height can be adjusted, but the detection sensitivity and accuracy are insufficient
Solution Approach 1:
The patent applies periodic action by supplying alternating-current heater power to the heater element rather than continuous DC power. This periodic heating creates alternating thermal expansion and contraction cycles of the head, which generates detectable phase changes in the head disk interference sensor signal at the touchdown point, significantly improving detection sensitivity and accuracy.
Solution Approach 2:
The patent changes the parameter of heater power supply from DC to AC, and utilizes the phase angle of the sensor output signal as a detection parameter. By monitoring the phase change of the sensor signal in response to periodic thermal expansion, the system achieves precise touchdown detection with high reliability.
2Measurement precision
If heater power is increased step by step to achieve touchdown, then the head projection amount increases, but the detection sensitivity remains insufficient
Solution Approach 1:
Instead of increasing heater power step by step, the patent uses periodic alternating-current heater power supply. This creates cyclic thermal expansion of the head, generating periodic signals from the head disk interference sensor. The phase angle of this periodic signal provides a sensitive and simple indicator of touchdown, reducing control complexity while improving detection sensitivity.
Solution Approach 2:
The patent replaces the mechanical step-by-step power adjustment method with an electrical signal-based detection method. By using AC heater power and measuring the phase angle of the sensor output, the system substitutes mechanical control complexity with electrical signal analysis, achieving higher detection sensitivity.
3Productivity
If the head is projected toward the disk surface to reduce flying height, then recording density increases, but the risk of head-disk contact increases
Solution Approach 1:
The patent implements feedback by continuously monitoring the head disk interference sensor output signal during heater power adjustment. The phase angle of the sensor signal provides real-time feedback on the head's proximity to the disk, enabling precise control of the head projection amount to achieve optimal flying height while preventing harmful head-disk contact.
Solution Approach 2:
The patent uses parameter changes by monitoring the phase angle of the sensor signal to control the heater power. This allows precise adjustment of the head projection amount, optimizing recording density while maintaining safe flying height to avoid head-disk contact.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables sensitive and accurate detection of touchdown, ensuring the head flying height is accurately set, enhancing both electromagnetic conversion performance and head disk interface reliability.
Implementation Method 1
When supplied with power (heater power), the heater element generates heat
Implementation Method 2
the heater element generates heat and thus thermally deforms (expands) the head
Implementation Method 3
A head disk interference sensor has been used to detect the touchdown
Data Source
AI summary
According to one embodiment, there is provided a method for detecting touchdown of head in a disk storage apparatus. The disk storage apparatus includes the head. The head includes a write element, a read element, a head disk interference (HDI) sensor, and a heater element. The HDI sensor detects thermal interference between the head and the disk. The method supplies alternating-current heater power to the heater element. The method increases the heater power in a step-by-step manner. The method further detects a phase of an output signal from the HDI sensor corresponding to the increased heater power, and detects the touchdown based on a change in the detected phase.