Multiple-Sense Thermo-Resistive Sensor for Head Touchdown Detection
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Solution Overview
Problem
Current disk drive systems face challenges in accurately detecting touchdown events between the head and magnetic media, which can lead to prolonged contact and potential drive failure due to environmental changes or contamination, necessitating improved detection methods.
Innovation Solution
A disk drive system equipped with multiple touchdown sensors located at the air bearing surface (ABS) of the head, connected in series or parallel to a detection circuit, measures voltage or current changes to accurately detect contact with the magnetic medium, enhancing the likelihood of timely detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single touchdown sensor is used, then the device complexity is reduced, but the reliability of touchdown detection deteriorates
Solution Approach 1:
The touchdown detection function is segmented into multiple independent sensors (first touchdown sensor and second touchdown sensor) located at different positions on the air bearing surface. This segmentation ensures that if one sensor fails or does not detect a touchdown event, the other sensor can still detect it, thereby improving reliability without requiring a single complex sensor system.
Solution Approach 2:
Different regions of the air bearing surface are equipped with touchdown sensors having potentially different characteristics or positions. The first and second sensors are positioned at different locations to detect touchdowns at different areas, allowing the system to account for local variations in contact conditions and improve overall detection reliability.
2Reliability
If multiple touchdown sensors are used, then the reliability of touchdown detection is improved, but the device complexity increases
Solution Approach 1:
The first touchdown sensor and second touchdown sensor are electrically connected in series or parallel to form a combined resistance that is measured by the touchdown sensing circuit. This merging approach allows multiple sensors to work together as a unified detection system, improving reliability while using a relatively simple electrical connection scheme rather than complex individual sensor processing.
Solution Approach 2:
The touchdown sensing circuit serves multiple functions: it measures the combined resistance of both sensors, detects touchdown events, and can determine which specific sensor detected the event. This multi-functionality reduces the need for separate processing circuits for each sensor, thereby limiting the increase in device complexity despite using multiple sensors.
3Measurement precision
If touchdown sensors are positioned away from the ABS, then the manufacturing process is simplified, but the measurement precision of touchdown detection deteriorates
Solution Approach 1:
The touchdown sensors are pre-positioned at specific locations on the air bearing surface during the manufacturing process. The first and second sensors are placed at predetermined positions that are optimized for detecting touchdowns, allowing the system to achieve high measurement precision while following a standardized manufacturing procedure that does not require complex post-processing or precision adjustment steps.
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
The use of multiple sensors at the ABS increases the reliability of detecting touchdown events, reducing the risk of prolonged contact and potential drive failure by ensuring prompt detection of frictional heat changes, thereby protecting the disk drive from damage.
Implementation Method 1
Heat generated by the thermal actuator causes thermal expansion of the head which locally reduces the spacing between the head and magnetic media
Implementation Method 2
The thermal actuator can produce heating sufficient enough to cause contact between the head and media—i.e., a touchdown event
Implementation Method 3
measuring a voltage across, or a current through, a combined resistance of the first and second touchdown sensors
Data Source
AI summary
Techniques of the present invention include detecting a touchdown between a read/write head of a disk drive and a surface of a magnetic disk using multiple touchdown sensors located at an air-bearing surface (ABS). The multiple sensors increase the likelihood that a touchdown event—i.e., a portion of the ABS of the head contacting the underlying magnetic disk surface—will be detected. During touchdown, the portion of the head contacting the magnetic disk generates frictional heat which changes a characteristic (e.g., the electrical resistance) of at least one of the sensors located at the ABS. When the sensors are connected to a detection circuit, the changing characteristic may be monitored to identify a touchdown event. The touchdown sensors may be, for example, electrically connected in either series or parallel to the detection circuit. Thus, as long as the electrical resistance of one of the sensors is changed, a touchdown event may be detected.