阅读说明：本技术 磁盘装置用的热致动器控制值的设定方法 (Method for setting control value of thermal actuator for magnetic disk device ) 是由 渡边彻 于 2018-12-14 设计创作，主要内容包括：实施方式提供磁盘装置用的热致动器控制值的设定方法，在设定磁盘用的热致动器的控制值的情况下，能够高精度地检测异常接触。在实施方式的设定方法中，在设定热致动器的控制值的情况下，在磁盘的半径方向上至少五个以上半径位置处进行曲线拟合，所述曲线拟合是使用通过热致动器使磁头与磁盘接触时向热致动器提供的电力和二次以上的曲线的曲线拟合，在各电力与二次以上的曲线的拟合残差的RMS的Z值超过了预定值的情况下，判定为检测到异常接触。(An embodiment provides a method for setting a control value of a thermal actuator for a magnetic disk device, which can detect abnormal contact with high precision when setting the control value of the thermal actuator for the magnetic disk. In the setting method of the embodiment, when the control value of the thermal actuator is set, curve fitting using electric power supplied to the thermal actuator when the magnetic head is brought into contact with the magnetic disk by the thermal actuator and a curve of a quadratic or more curve is performed at least five or more radial positions in the radial direction of the magnetic disk, and when the Z value of RMS of a fitting residual between each electric power and the curve of the quadratic or more curve exceeds a predetermined value, it is determined that abnormal contact is detected.)

1. A method for setting a control value of a thermal actuator for a magnetic disk apparatus,

performing curve fitting at least at five or more radial positions in a radial direction of a magnetic disk, the curve fitting being curve fitting using power supplied to the thermal actuator when a magnetic head is brought into contact with the magnetic disk by the thermal actuator and a function of a quadratic or more,

and determining that abnormal contact is detected when the Z value of the RMS of the fitting residual between each electric power and the quadratic or higher function exceeds a predetermined value.

2. The setting method of the control value of the thermal actuator according to claim 1,

it is also determined that the abnormal contact is detected when the Z value of the coefficient of the function exceeds the predetermined value.

3. The setting method of the control value of the thermal actuator according to claim 1 or 2,

it is also determined that the abnormal contact is detected when a Z value, which is a deviation amount from a distance of an inter-coefficient correlation line of the function, exceeds the predetermined value.

4. The setting method of the control value of the thermal actuator according to claim 1,

the curve fitting is performed by sequentially excluding the values of the radial positions for each of the radial positions, the Z value of the RMS of the fitting residual is evaluated,

and determining the radius position of the RMS, at which the Z value is evaluated as the minimum value, as the abnormal contact radius position.

5. The setting method of the control value of the thermal actuator according to claim 4,

the curve fitting is performed by sequentially excluding the values of the radial positions for each of the radial positions, the sum of the Z value of the RMS of the fitting residual and the Z value of the coefficient of the curve is evaluated,

and determining the radius position of which the sum Z value is evaluated as the minimum value as the abnormal contact radius position.

6. The setting method of the control value of the thermal actuator according to claim 4 or 5,

the curve fitting is performed by sequentially excluding the values of the radial positions for each of the radial positions, the sum of the Z value of RMS of the fitting residual and the Z value of the distance which is a correlation with the coefficient of the curve is evaluated,

and determining the radius position of which the sum Z value is evaluated as the minimum value as the abnormal contact radius position.

Technical Field

Background

In a conventional magnetic disk device, when detecting abnormal contact between a magnetic head and a recording medium when a thermal actuator control value is set, contact detection is tried a plurality of times at the same radial position of a magnetic disk, and contact is performed until the deviation of the detection result becomes a certain degree or less, thereby determining whether abnormal contact is detected.

However, according to the method of contact detection, the contact detection is shifted due to its algorithm, and although the repeatability is good, it cannot be excluded that the contact detection is erroneous. In addition, in the case of using a function (polynomial) with a high degree of order, the gap between the magnetic head and the recording medium can be controlled to be more constant, but in the case of abnormal contact between the magnetic head and the recording medium, it is difficult to accurately determine abnormal contact detection only by fitting errors obtained by using a function with a high degree of order.

Disclosure of Invention

Embodiments of the present invention provide a method for setting a control value of a thermal actuator for a magnetic disk device, which can detect abnormal contact with high accuracy when setting the control value of the thermal actuator for the magnetic disk.

The method for setting the control value of the thermal actuator for a magnetic disk device according to one embodiment performs the following processing. In the case of setting a control value of a thermal actuator, curve fitting is performed at least at five or more radial positions in a radial direction of a magnetic disk, the curve fitting being curve fitting using a power supplied to the thermal actuator when a magnetic head is brought into contact with the magnetic disk by the thermal actuator and a function of a quadratic or more. When the Z value of the RMS of the fitting residual between each electric power and the quadratic or higher function exceeds a predetermined value, it is determined that abnormal contact is detected.

Drawings

Fig. 1 is a diagram showing an example of a schematic configuration of a magnetic disk device according to an embodiment.

Fig. 2 is a cross-sectional view showing an example of the structure of the head according to the embodiment.

Fig. 3 (a) and 3 (b) are diagrams for explaining an example of adjustment of the floating height according to the present embodiment in detail.

Fig. 4 is a flowchart showing an example of the process of acquiring the contact detection data according to the embodiment.

Fig. 5 is a flowchart showing an example of the abnormal contact determination process when setting the control value of the thermal actuator according to the embodiment.

Fig. 6 is a diagram showing an example of a residual error in 4-degree function fitting according to the embodiment.

Fig. 7 is a diagram showing the RMS distribution of residuals when 4-degree function fitting is performed for a plurality of sliders according to this embodiment.

Fig. 8 is a diagram showing an example of the correlation between coefficients according to the embodiment.

Fig. 9 is a diagram showing an example of the correlation between coefficients according to the embodiment.

Fig. 10 is a diagram showing an example of the correlation between coefficients according to this embodiment.

Fig. 11 is a diagram showing an example of the correlation between coefficients according to this embodiment.

Fig. 12 is a diagram for explaining an example of the case of performing 4-degree function fitting including an abnormal contact radius position according to the embodiment.

Fig. 13 is a diagram for explaining an example of the case where the 4-degree function fitting is performed excluding the abnormal contact radius position according to the embodiment.

Fig. 14 is a graph showing an example of abnormal contact detection based on the evaluation function according to the embodiment.

Fig. 15 is a graph showing an example of the abnormal contact position detection with respect to the error amount according to the embodiment.

Embodiments relate to a method of setting a thermal actuator control value for a magnetic disk device.