High Sample Rate dPES Contact Detection for Storage Media

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Solution Overview

Problem

Current contact detection schemes in data storage devices, such as disc drives, face challenges in accurately detecting head-to-media contact due to reduced signal-to-noise ratio (SNR) and increased friction at lower fly heights, leading to potential signal errors and wear issues.

Innovation Solution

A method utilizing high sample rate position error signal (dPES) combined with a pulsed heater and lock-in technique to improve SNR for contact detection, involving a pulsed input signal with specific amplitude and duty cycle to simulate a response signal, and locking in amplitude with respect to heater frequency to determine the optimal heater power for initiating contact between the transducing head and media.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If fly height is reduced to increase recording density, then more data can be recorded and read, but contact between transducer and media occurs due to surface irregularities

Engineering Contradiction:

Improverecording densityVSAvoidcontact detection reliability

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent applies periodic pulsing of the writer heater at a specific frequency to generate a modulated friction signal during contact. By pulsing the heater periodically and using lock-in detection at the same frequency, the system can extract the contact signal from noise, enabling reliable contact detection at reduced fly heights where contact is more likely to occur.

Inventive Principle:

Principle #19Periodic action

2Reliability

If writer heater power is increased to ensure contact, then contact detection becomes more reliable, but friction between head and media increases causing signal errors

Engineering Contradiction:

Improvecontact detection reliabilityVSAvoidfriction-induced signal errors

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The system uses feedback by monitoring the dPES signal generated during heater pulsing. The lock-in detection technique processes the dPES signal at the heater pulse frequency to determine contact status. This feedback mechanism allows the system to identify the minimum heater power required for contact, preventing excessive power application that would cause harmful friction.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent changes the operational parameters by using pulsed heater power with specific amplitude and duty cycle rather than continuous power. This parameter modification creates a modulated friction signal that can be detected through lock-in techniques, enabling accurate contact detection at lower average power levels and reducing friction-induced signal errors.

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If conventional contact detection schemes are used at reduced fly height, then contact detection can be performed, but signal-to-noise ratio deteriorates leading to inaccurate detection

Engineering Contradiction:

Improvecontact detection accuracyVSAvoidsignal-to-noise ratio

Core Design Contradiction:

Measurement precisionVSLoss of information

Solution Approach 1:

By pulsing the writer heater periodically and using lock-in detection at the same frequency, the system can extract the contact signal from noise, enabling reliable contact detection at reduced fly heights where contact is more likely to occur.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The periodic pulsing of the writer heater creates a modulated mechanical friction signal when contact occurs. This vibration-like modulation at the pulse frequency allows the contact signal to be distinguished from background noise through frequency-selective lock-in detection, improving measurement precision.

Inventive Principle:

Principle #18Mechanical vibration

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 enhances the accuracy of contact detection, minimizing friction and signal errors, allowing for reliable and wear-free contact between the head and media, thereby maintaining optimal head-to-media spacing and reducing operational issues.

Implementation Method 1

powering a transducing head actuator with pulsed input signal... to simulate a response signal

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

locking in an amplitude with respect to the heater frequency

Methodology Applied

Scientific EffectLock-in detection:

Implementation Method 3

detecting off-track signal by measuring change in position error signal (dPES), which results from friction between the head and the contacted media

Methodology Applied

Scientific EffectFriction: Friction

Data Source

PatentUS9792940B2High sample rate dPES to improve contact detection signal to noise ratio

Publication Date: 2017.10.17 SEAGATE TECH LLC

AI summary

Using a high sample rate dPES, together with pulsed heater and lock-in technique, to improve dPES SNR for contact detection between the head and media surface. Steps of powering a transducing head actuator with pulsed input signal at a select data track offset from a previously-written to data track of the storage medium, where the pulsed input signal has select amplitude and duty cycle to simulate a response signal, and further locking in an amplitude with respect to the heater frequency, can lead to a determination of level of heater power for initiating contact between the transducing head and the storage medium.