Slit design for the thermal flying height control slider

In this work, we propose a novel thermal flying height control (TFC) slider, by designing a slit near the thermal heater in the slider. Design of the slit can reduce the mechanical constraints on the head elements and concentrate the heat around head elements. In turn, head elements can achieve more thermal protrusion and flying height reduction compared to the traditional TFC slider. The simulation results show that the application of the slit achieves a flying height reduction of 1.4 nm at writer and 1.7 nm at reader. Parametric study indicates that a trade off among the slit thickness (a), the distance of the slit to ABS (d) and thermal heater (t) should be optimized to achieve both large flying height reduction and small difference of flying height between reader and writer.     

An efficient thermal actuator design for the thermal flying height control slider

In this work, we propose a novel thermal actuator by designing a thermal insulator, a thermal conductor, and their combination to the traditional thermal heater. The thermal-structure simulation coupled with air bearing simulation is used to simulate the actuation by the thermal actuator, as well as the effects on flying performance of slider being actuated. The simulation results show that an additional 0.8–1.1 nm flying height reduction can be obtained by applying the proposed thermal actuator when the flying height of TFC slider is about several nanometers.     

Simulation of thermal flying height control slider with built-in contact sensor

This work investigates the piezoelectric contact sensor in the thermal flying height control (TFC) slider. A finite element model is built for the thermal flying height control slider with a piezoelectric contact sensor, which is used to detect the contact between the slider and disk. A constant force is applied at the maximum thermal protrusion point of air bearing surface. The simulation results show that the ZnO sensor with shear-mode is more sensitive to contact force than that with transverse-mode. The sensitivity of contact sensor can be increased by reducing the cross-sectional area of sensor, increasing the thickness of sensor, and choosing a short distance of sensor to air bearing surface. In addition, the thermal-stress effects from TFC heater on contact sensor are significantly large and the amplitude of thermal-stress inducing output voltage is orders larger than that induced by contact force. However, by optimizing the distance of sensor to ABS, it is possible to eliminate the thermal-stress effects. Finally, the response time of thermal-stress induced electrical voltage of contact sensor is about 0.3?ms.     

Contact between a thermal flying height control slider and a disk asperity

Contact between a thermal flying height control slider and an asperity on a disk is investigated using finite element analysis. The finite element model developed accounts for transient elastic–plastic deformation and heat generation due to frictional heating. Plastic deformation and temperature rise of the read/write element are determined as a function of flying height of the slider, location of the read/write element as well as material properties of typical disk asperities. The model shows good agreement with experimental data. Significant plastic deformation and temperature rise were observed in the shield and alumina regions of the slider. Hard and stiff disk asperities, such as alumina asperities, result in more damage to the slider than soft and compliant nickel-phosphorus ones.     

Numerical simulation of thermal flying height control sliders in heat-assisted magnetic recording

Heat assisted magnetic recording (HAMR) is one of the most promising techniques to extend the recording density in hard disk drives beyond 1?Tb/in². Although the diameter of the spot on the disk that is heated by the laser beam is very small, on the order of nanometers, high local temperatures on the disk and the heat dissipated in the slider during the light delivery process can cause thermal deformations of both the disk and the slider, thereby affecting the flying characteristics at the head-disk interface. In this paper, a finite element model is developed which incorporates a HAMR optical system into a thermal flying height control (TFC) slider with dual heater/insulator elements to study the effect of heat dissipation in the wave guide on the thermal deformation and flying characteristics of a HAMR-TFC slider. In addition, the power input of the laser and design parameters of the heaters are investigated.     

Adaptive flying height modulation control of hybrid active slider with thermal and piezoelectric actuators

Hybrid active slider is an effective means to increase the storage density of hard disk, but its effectiveness is compromised by the flying height modulation (FHM), the bounding vibrations associated with the slider. There is a need to reduce the FHM through real time control. The hybrid active slider exhibits a very complex dynamic behavior which causes a big challenge for the traditional controller relying on an exact dynamic model. Without the requirement of an exact knowledge of the dynamics of the slider, this paper proposes an adaptive control scheme to control the flying height modulation. It is designed from the model with uncertain parameters and can guarantee the convergence of FHM. The details of the controller design and the proof of its performance are presented, and simulation results are provided to verify the effectiveness of the controller.     

Experimental set-up for simultaneously measuring changes in LD temperature and flying height of HAMR-HGA

Heat-assisted magnetic recording (HAMR) is a promising technology for overcoming the performance limit of the conventional magnetic head in a hard disk drive. The HAMR-HGA consists of a HAMR-head slider, a suspension, and a laser diode (LD) mounted on the slider. An optical near-field transducer (NFT) and a waveguide are near the write-pole in the head slider. During the HAMR process, current is applied to an LD, and the laser beam is coupled into the waveguide and delivered to the NFT. The NFT further concentrate the focused optical spot and the optical spot locally heats the recording medium, thereby reducing the media coercivity. The temperature of the LD and the slider, however, increases. The slider is, moreover, locally deformed, and the flying-height (FH) changes. Therefore, an experimental set-up to simultaneously evaluate the FH change and LD temperature of the HAMR-HGA was required to develop the HAMR technology. We developed a novel experimental set-up for simultaneously evaluating laser characteristics (power, voltage, and wavelength), the increase in LD temperature, and the FH change of a HAMR-HGA. By using this set-up to measure these characteristics of our prototype, the HAMR-HGA showed that the FH decreased as the LD temperature increased. The LD temperature is directly related to the laser characteristics. The change in laser characteristics affects the read-write performance of HAMR. The FH change also affects the performance. Therefore, the developed experimental set-up should be useful in improving HAMR-HGA.     

The effect of write current on thermal flying height control sliders with dual heater/insulator elements

The effect of write induced pole tip protrusion on the magnetic spacing of the head/disk interface has to be taken into consideration as flying heights approach the spacing regime of a few nano-meters. Thermal flying height control (TFC) sliders are presently in common use in hard disk drives to control the flying height at the read/write element during drive operations. In this paper the flying characteristics of TFC sliders with dual heater/insulator elements are investigated. Simulation results are shown for situations where the write current is ??on?? and where the write current is ??off??. The effect of design parameters of two heater/insulator elements is studied to optimize the performance of TFC slider.     

Time dependent simulation of active flying height control of TFC sliders

A time-dependent numerical simulation procedure is implemented to simulate the flying height response of a typical thermal flying height control (TFC) slider as a function of the power input to the heater element. The Reynolds equation is used in conjunction with a TFC slider finite element model to determine the change in the thermal protrusion and flying height of the slider. The power input signal to the heater element is optimized using convex optimization to minimize flying height variations of the slider. The optimization procedure is applied to a typical experimentally measured flying height profile. The numerical simulation results are in excellent qualitative agreement with experimental measurements.     

温湿度传感器抗腐蚀研究

针对在化学腐蚀性气体环境的生产过程中存在的温湿度传感器易被化学气体腐蚀而损坏的问题,研制了一种基于干湿球法测量温度和湿度的抗腐蚀方案。阐述了温度传感器和温度变送器的抗蚀制作方法,介绍了干湿球法测量湿度的具体应用实例。实验证明：本方案有效解决了在具有化学腐蚀性气体环境里温湿度传感器易被化学气体腐蚀的难题。     

Effects of environmental temperature on the performance of a micromachined gyroscope

This paper presents the modeling of the detection capacitance analysis for a tuning fork vibratory microgyroscope fabricated by the bulk silicon micromachining technology. The dynamic characteristics of the detection capacitance of the microgyroscope are calculated based on the model. Then the effects of environmental thermal fluctuations on the microgyroscope are considered. Non-linear analysis and numerical simulations show that the frequencies and output of the microgyroscope have slight deviations when the microgyroscope works at different environmental temperature. The deviations of the frequencies and dynamic characteristics are calculated accurately, which provides a reference for the design of temperature compensation method and robust structural design for the microgyroscope.     

Parametric simulation of piezoelectric flying height control slider using shear-mode deformation

The piezoelectric flying height control slider has recently been implemented in magnetic recording disk drives to reduce the flying height. This paper performs the electromechanical simulation and air-bearing simulation to investigate the effects of the shear-model deformation on the static flying attitude of PZT slider. The location of PZT sheet and air bearing surface of slider are investigated to achieve a low flying height and robust head-disk interface. The results show that a short distance of the PZT sheet to the trailing edge of the slider can help to achieve a low flying height. A small center-trailing pad of the slider can also help to achieve a low flying height, but cannot prevent the reduction in pitch angle. The depth of the center-trailing pad does not change the reduction ratio of the pitch angle when increasing the drive voltage. A big pitch angle value is needed to avoid the pitch angle falling below zero at a high drive voltage.     

Influence of high ambient temperature and humidity on visual sensitivity

Abstract

The visibility of sinusoidally modulated gratings was measured psychophysically during 3 hours of exposure to either (i) a control, (ii) a warm-humid or (iii) a hot-dry atmosphere. No significant loss of contrast sensitivity in the heat conditions could be demonstrated for low spatial frequencies (≤ 3·0 c/deg) but an increasing loss with increasing frequencies (maximal above 10 c/deg). The heat-induced performance change appeared within 30min of exposure.     

Effects of different flying altitudes on biophysical stand properties estimated from canopy height and density measured with a small-footprint airborne scanning laser

Canopy height distributions were created from small-footprint airborne laser scanner data collected over 133 georeferenced field sample plots and 56 forest stands located in young and mature forest. The plot size was 300-400 m² and the average stand size was 1.7 ha. Spruce and pine were the dominant tree species. Canopy height distributions were created from both first and last pulse data. The laser data were acquired from two different flying altitudes, i.e., 530-540 and 840-850 m above ground. Height percentiles, mean and maximum height values, coefficients of variation of the heights, and canopy density at different height intervals above the ground were computed from the laser-derived canopy height distributions. Corresponding metrics derived from the two different flying altitudes were compared. Only 1 of 54 metrics derived from the first pulse data differed significantly between flying altitudes. For the last pulse data, the mean values of the height percentiles were up to 50 cm higher than the corresponding values of the low-altitude data. The high-altitude data yielded significantly higher values for most of the canopy density measures. The standard deviation for the differences between high and low flying altitude for each of the metrics was estimated. The standard deviations for the height percentiles ranged from 0.07 to 0.30 cm in the forest stands, indicating a large degree of stability between repeated flight overpasses.The effect of variable flying altitude on mean tree height (h_L), stand basal area (G), and stand volume (V) estimated from the laser-derived height and density measures using a two-stage inventory procedure was assessed by randomly combining laser data from the two flying altitudes for each individual sample plot and forest stand. The sample plots were used as training data to calibrate the models. The random assignment was repeated 10,000 times. The results of the 10,000 trials indicated that the precision of the estimated values of h_L, G, and V was robust against alterations in flying altitude.     

湿度传感器温度补偿法的研究

通过对湿敏电阻器的特性分析,找出湿敏电阻阻值随温度的指数变化关系,采用附加对数运算电路进行硬件补偿,使其脱离指数状态,低湿性能得到改善;基于EE06型高分子湿敏电容器特性的研究分析,分别在0℃以上和0℃以下分段采用数学模型拟合的软件算法进行温度补偿,使湿敏元件的测湿方程的显著度分别为5 668.579 0和2 416.919 00,均大于F0.01(9,8),在0.01显著水平上是高度显著的。2种温度补偿措施都使湿敏元件的测湿准确度大大提高。     

低成本现场总线温湿度变送器

总线式温湿度变送器可同时完成对温湿度参数的测量,同时采用脉宽调制电路代替传统的传感器信号调理电路,提高了变送器测量系统的精度和可靠性,具有较强的抗干扰能力,且降低了设计成本。     

温度湿度无线测控系统设计

介绍了具有无线功能的温度湿度测控系统的工作原理、硬件结构设计、试验结果。该系统以温度湿度传感器为核心,利用无线收发器构成无线扫描控制系统,实现了温度0.6℃误差和湿度5%RH误差的测量。该系统体积小、功耗低、电路简单,可以方便安装和实现实时监控。     

湿敏电容器的温度补偿方法研究

为了精确辨识湿敏电容器的温度补偿模型,减小系统测量误差,分析了湿敏电容器的温度补偿原理,提出了一种基于改进的遗传算法(GA)和支持向量机(SVM)相结合的补偿算法.基于湿敏电容器,建立了GA-SVM补偿模型,并与BP神经网络方法进行了比较.共144个样本点,经过补偿后GA-SVM和BP模型的相对误差绝对值小于3％的个数分别为143,110;最大分别为0.34％,19.68％.结果表明:改进的GA-SVM算法有效地补偿了温度影响,提高了湿敏电容器的测量精度,同时该算法的逼近能力和泛化能力均要优于BP神经网络.因此,该方法用于湿度传感器温度补偿是有效可行的.