Feasibility study of thermal positioning control actuator for hard disk drives

We have developed an actuator with a heater embedded in the head slider. This actuator, called the thermal positioning control (TPC) actuator, is integrated next to the read write elements in the head slider. By applying electric power to the TPC actuator, the actuator causes thermal expansion and the read write elements then move in the positioning direction. We demonstrated its feasibility in terms of the stroke and frequency response. We designed and fabricated head sliders that integrated a TPC actuator and a read element. We also conducted an experimental evaluation at the spin-stand. The results of 5?nm stroke and a 5-kHz bandwidth were experimentally demonstrated. These results showed the feasibility of the TPC actuator for future 550?kilo?track per inch class hard disk drives.     

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.     

Active-head sliders using piezoelectric thin films for flying height control

This paper describes design and fabrication of a MEMS-based active-head slider using a PZT thin film for flying height control in hard disk drives. A piezoelectric cantilever integrated in the air bearing slider is used to adjust the flying height individually. An air bearing surface (ABS) geometry that minimizes the aerodynamic lift force generated beneath the head has been designed based on the molecular gas film lubrication (MGL) theory. The sliders with PZT actuators were fabricated monolithically by silicon micromachining process. Performance of the actuator was tested by using an optical surface profiler. Furthermore, the fabricated slider was mounted on a suspension and the flying height of the slider above a spinning disk has been measured by multiple wavelength interferometry. Change in the head-disk spacing has been successfully confirmed by applying voltage to the actuator.     

Active flying-height control slider using MEMS thermal actuator

Today’s head/disk interface design has a wide flying height distribution due to manufacturing tolerances, environmental variations, and write-induced thermal protrusion. To reduce the magnetic spacing loss caused by these effects, we developed an active head slider with a nano-thermal actuator. The magnetic spacing of these sliders can be controlled in situ during drive operations. After simulating the heat transfer in the slider to obtain the thermal deformation of the air-bearing surface, we fabricated a thermal actuator using thin-film processing. An evaluation done using a read/write tester showed a linear reduction in the magnetic height as electric power was applied to the actuator. The actuator’s stroke was 2.5 nm per 50 mW with a time constant of 1 ms. There was no significant impact on the reliability of the read element.     

Thermal actuator for accurate positioning read/write element in hard disk drive

Flying height control (TFC) sliders with thermal actuation, which make it possible to control head disk spacing, have been introduced in commercial products for compensating the flying height loss and reducing the risk of head disk contacts, thus to increase the bit density (Gupta et al. in ASME J Tribol 123:380–387, 2001; Juang and Bogy in ASME J Tribol 129:570–578, 2007; Kurita et al. in Microsyst Technol 12:369–375, 2006; Shiramatsu et al. in IEEE Trans Magn 42:2513–2515, 2006). However, with the increasing of areal density, it is also necessary to increase the track density. To increase track density, it is required to improve the performances of head positioning system in terms of fast transition from one track to another (track seeking), fast and accurate settling, and precise track following of the target track. Dual-actuator systems (Choe in A thermal driven micro actuator for hard disk drive. In: Proceedings of the APMRC 2010, Nov 10–12, 2010, Singapore, 2010; Bain et al. in Electrothermal actuator for hard disk drive application. In: Proceedings of the APMRC 2010, Nov. 10–12, 2010, Singapore, 2010; Furukawa et al. in Fabrication and test of thermal actuator. In: ISPS 2011, Jun. 13–14, Santa Clara, CA, USA, 2011) have been proposed to meet these requirements. These dual-actuator systems consist of a voice-coil-motor (VCM) as a first-stage actuator and a transducer (piezoelectric, electromagnetic, electrostatic and thermal) as a second-stage actuator. The second-stage actuator could be designed to actuate the movement of suspension (suspension driven), slider (slider driven) or head element (head driven). Most of reported dual-actuator systems were made to be suspension driven or slider driven. Recently, Choe by (A thermal driven micro actuator for hard disk drive. In: Proceedings of the APMRC 2010, Nov. 10–12, 2010, Singapore, 2010) and Bain et al. by (Electrothermal actuator for hard disk drive application. In: Proceedings of the APMRC 2010, Nov. 10–12, 2010, Singapore, 2010) reported to use thermal actuators for driving head movement. They attained a thermal transient of less than 10?μs using 2-D finite element simulation. Using thermal actuators to accurately position read/write element could be a promising technology for mass production for future HDD. This kind of control theme was termed as thermal positioning control (TPC). The objective of TPC actuator design is to achieve large actuation stroke as well as increase frequency bandwidth. In our studies, the design procedure may involve several steps: (1) Fundamental studies with simple TPC slider structure by finite element simulations to explore the feasibility of TPC actuation and estimate working frequency range. Also we may be able to find out the problems which induced by TPC actuator. (2) Prototyped TPC slider, and tested its frequency characteristics to confirm the feasibility and achievability of TPC actuation. (3) Increases TPC actuation stroke and frequency bandwidth by improving TPC slider structures and servo control schemes. This paper explores the feasibility studies of TPC slider by finite element simulation. The principle and structural modeling of slider with TPC heater was first introduced. Then static–static simulation was carried out to study the steady deformation displacement at read/write element and transient analysis was conducted to estimate the deformation displacement response. It was found that 7?nm deformation stroke at read/write element could be attained at steady state with 50?mW input power, and the deformation displacement was about 1.7?nm after power was applied to TPC heater 1.5?ms (frequency of 1?kHz based on first order delay system). Meanwhile, it was found that protrusion on the air bearing surface (ABS) becomes a problem for the slider’s flying performance, thus the ABS design was improved to reduce protrusion’s effect, and cross-talk effect between TFC and TPC actuators was then investigated.     

Nanoscale dynamics of MEMS TFC active slider

With enabling of a thermal actuator, an air bearing slider can fly at sub-nanometer level spacing on a magnetic disk while the recording elements are functioning. At such spacing, the slider stability and head-disk interface reliability remains to be understood. In this study, a novel understanding on dynamics of the MEMS thermal flying-height control (TFC) slider in touchdown process is developed. By using average and variational-iteration methods, closed-form spectrum estimations of slider vibration are derived. The derived formulation offers an insight of the relationship between spectrum and interface parameters. Physics-based simulation is also conducted to quantify the spectrum of slider vibrations as a function of varied interfacial parameters. To further extend the analytical and numerical analysis, the experimental study of a TFC slider while flying on a rotating disk at sub-nanometer spacing are performed. The analysis reveals the dominance of the air bearing force among other interfacial forces at sub-nanometer spacing.     

MEMS milliactuator for hard-disk-drive tracking servo

This paper describes the design, fabrication, and operational characteristics of a MEMS milliactuator designed for servo tracking in a hard-disk drive (HDD). The actuator is designed to increase the bandwidth of an HDD tracking servo and pack more recording tracks on a disk. An Invar (low thermal expansion metal) electrode position process was developed to meet the thermal stability requirement. The electroplated Invar's thermal coefficient of expansion is as low as 6.3×10^-6/K, which is almost half of that of pure nickel. For the plating mold pattern definition, a high-aspect-ratio polymer etching technique was developed. A high-aspect-ratio structure line-and-gap definition is required to achieve both a high directional stiffness ratio and electrode efficiency for the actuator. The etching technique described can etch through a thick (<40 μm) polymer layer with an aspect ratio of 16:1 at an etch rate of <2 μm/min. Low-cost/high-volume manufacturing is achievable by this batch fabrication technique. A milliactuator was fabricated and assembled with a suspension and a slider weighted at around 2 mg. The slider was successfully driven by the milliactuator while the slider was flying on a spinning disk. The operational characteristics (frequency response) of the in-flight milliactuator were measured, and the results indicate that the actuator is suitable for high-bandwidth HDD servo-tracking applications     

Robust design of a shape memory actuator with slider and slot layout and passive cooling control

Microsystem Technologies - This work proposes a new shape memory actuator based on a slider and slot mechanism. The device is composed by two couples of opposed SMA coil elements. The SMA elements...     

Resonant-Type Smooth Impact Drive Mechanism Actuator with Two Langevin Transducers

A smooth impact drive mechanism (SIDM) is a unique piezoelectric actuator that is widely used as a camera focusing mechanism, cell phone lens movement mechanism, etc. This principle enables a compact driving mechanism; however, it cannot generate high-speed movement because a soft-type multilayered piezoelectric transducer (PZT) is utilized at off-resonant movement. This paper proposes a resonant-type SIDM actuator driven with hard-type PZTs to realize high-speed and powerful operation. The fundamental principle is also based on the conventional SIDM; therefore, a saw-shaped movement is required. To generate a high-power ultrasonic output, two Langevin transducers are adopted instead of a soft-type multilayered PZT. One Langevin transducer was a stator and the other was slider whose tip was adhered to a carbon fiber reinforced plastic (CFRP) rod. The CFRP rod was connected to the stator transducer with the frictional force. To obtain quasi-saw-shaped vibration, the longitudinal vibration for each Langevin transducer was excited and these movements were added at the connection point at the CFRP rod. In order to combine these vibration modes, the lengths of the stator and slider Langevin transducers were designed to make the resonant frequencies ratio to be 1:2. By using the proposed principle, the slider Langevin transducer was successfully driven with the speed of 0.11 m/s and the output force was 1.8 N with no load.     

Visualisation of size-dependent particle deposition in a slider/disk interface

 As contamination will play a significant role in slider-based magneto-optical (MO) data storage systems, a novel experimental technique is proposed to enhance contamination visualisation. This technique is based on using mixtures of different sizes of monodisperse, fluorescent, spherical, polystyrene-latex particles, each size having a different fluorescent colour. Apart from the relatively easy visualisation of size-dependent particle deposition, validation of numerical simulations of particle deposition is also enhanced. The experimental results obtained with the fluorescent particles, which are soft, are compared with results obtained when harder, spherical, silicate particles are used. It is demonstrated that these hard particles are simply embedded in the polycarbonate disk, and cause no significant damage to, or contamination of, the slider. The soft fluorescent particles are not embedded, but smears and scratches on the disk surface are observed. The slider contamination is much more severe with the soft particles than with the hard silica particles, however, also when a hard glass disk is used. This indicates that the MO slider cannot simply be protected from contamination with soft particles by increasing the hardness of the disk. As many soft particles are present in the atmosphere, additional slider features will be needed to reduce slider contamination, and thereby the risk of system malfunction. Future numerical support of the development of such features is believed to be enhanced with the described experimental validation method. Received: 14 February 2002/Accepted: 24 April 2002 The author would like to thank, in random order, Jaap den Toonder, Guus Braun, Frank Penning, Gerard Hoeymans, Bas van Rens, Ferry Zijp, Martin van der Mark, and Geert Koenen, without whom this work would not have been possible.     

A numerical simulation on a pneumatic air table realized bymicro-EDM

This paper presents a numerical simulation of the flow field on a one-dimensional pneumatic actuator. Unlike conventional actuators, this model uses dynamic pressure instead of friction to drive a slider. The objective of this simulation is to find the detail of the flow field under the slider as well as the influence of its levitation on the horizontal transportation. Secondary vortices to be formed under the slider may cause an instability of the slider movement. To further assure a stable transportation of the slider, absence of secondary vortices in the gap is desirable, which can be achieved by narrowing the gap width. However, a too narrow gap might cause a significant increase of flow impedance and thus sacrifice the horizontal transportation. Here, two cases with gap width of 100 and 50 μm were investigated. With a gap width of 50 μm, there was no secondary vortex formed; however, the horizontal transportation was greatly sacrificed. In contrast, with a gap width of 100 μm, several secondary vortices of a size one to two times the gap width were formed. However, the horizontal driving force was about eight times larger than that in the case of a gap width of 50 μm     

A pneumatic air table realized by micro-EDM

This paper presents a one-dimensional (1-D) pneumatic actuator fabricated by combining several micromachining technologies such as microelectrodischarge machining (micro-EDM) as well as isotropic and anisotropic wet etching. Unlike the existing pneumatic actuators, which usually convey the object by means of friction, this device employs the dynamic pressure of inclined driving jets in order to enhance the horizontal transportation performance. Typical slider speeds of up to 5 cm/s can be obtained. Comparisons between different types of sliders are presented. By an appropriate patterning of the slider bottom surface, the speed could be increased by 50%-60%. Similarly, a maximum tangential force of 20 μN (equivalent shear stress: 2.2 μN/mm²) was obtained using this dynamic pressure concept. The latter is about two times larger than that of a slider with a smooth surface     

软体仿蛙游动机器人关节式气动致动器研制

为实现仿蛙游动机器人的微小型化,增强其环境适应能力,结合软体材料的优势特点和青蛙划动推进的游动方式,提出了一种关节式气动软体致动器,该致动器在满足软体仿蛙机器人游动过程中的运动性能和力学性能的同时,使得其肢体结构更加紧凑、轻量．利用Yeoh本构模型和虚功原理,结合关节式气动软体致动器的几何参数,建立了致动器的形变分析模型．进而,在致动器总体尺寸受约束的情况下,以一定弯曲角度下致动器输出恢复力矩最大为目标,确定了致动器的具体结构参数．融合3D打印、模塑成型等加工工艺方法,加工制备了关节式气动软体致动器,并通过对比分析,确定了采用纤维线限制致动器径向凸起效应时纤维线的绕线形式和绕线密度．最后经过实验测试分析,该致动器质量约7.5 g,可实现由180°弯曲状态至伸直状态的形态变化,并且在弯曲角度一定时通过调整充入气压的大小可以匹配一定范围内不同大小的负载力矩,从而验证了针对软体仿蛙游动机器人设计的关节式气动软体致动器的可行性．     

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.     

Adaptive neuro-fuzzy modeling of a soft finger-like actuator for cyber-physical industrial systems

Soft robotics is a trending area of research that can revolutionize the use of robotics in industry 4.0 and cyber-physical systems including intelligent industrial systems and their interactions with the human. These robots have notable adaptability to objects and can facilitate many tasks in everyday life. One potential use of these robots is in medical applications. Due to the soft body of these robots, they are a suitable replacement for applications like rehabilitation and exoskeletons. In this paper, we present the neuro-fuzzy modeling of a soft pneumatic finger-like actuator. This actuator is a fiber-reinforced soft robot with the shape and dimensions of a real finger and moves in planar motion. A bending sensor is used as a feedback for curvature motion of this actuator. In order to model this actuator, an adaptive neuro-fuzzy inference system is utilized to overcome the hardship in the modeling of the nonlinear performance of the soft materials. An experimental setup is designed to obtain suitable input–output data needed for modeling. The results show the applicability of the utilized method in the modeling of the soft actuator.

     

Dynamics Modelling of Hexaslides using the Decoupled Natural Orthogonal Complement Matrices

In this paper, dynamic model of a class of parallel systems, namely, the hexaslides, is proposed. The model developed is based on the concept the decoupled natural orthogonal complement (DeNOC) matrices, introduced elsewhere. The dynamic model of hexslides, though complex due to the existence of multi-loop kinematic chains, is required for actuator power estimation, computed-torque control, optimum tool trajectory generation, etc. The use of DeNOC offers many physical interpretations, recursive algorithms, and parallel computations. Using the proposed dynamic model, a parallel inverse dynamics algorithm has been presented to compute the actuator forces. This is useful to choose suitable motors for an application. An illustration is provided using an existing machine tool based on hexaslides, namely, the HexaM, while it is carrying out a circular contouring. Secondly, the effect of leg and slider inertias is also studied, which clearly suggests that neither of these can be neglected while finding the actuator forces.     

Analysis of a 0.1-μm stepping bi-axis piezoelectric stage using a 2-DOF lumped model

Piezoelectric stages are widely used for parts manipulation, including micro-component assembly and bio-cell manipulation. This paper proposes a bi-axis piezoelectric stage based on a friction driven mechanism. The carrier slides on a supporting frame and slider constructed in the same plane as a low-profile stage. The dynamic model of the friction driven is based on a 2-DOF lumped model considering the impact and separation behavior. The first mass is the bulk piezoelectric actuator (slab)—as a vibrator—and the second is the driven slider. The stiffness ratio of the piezoelectric slab-to-the driven slider affects the output force of the slider because of the contact time ratio. Moreover, the stepping size is adjusted according to the duty ratio of the pulse width of the driving signal. The stepping size of 0.1 μm is achieved in the X and Y axes corresponding to 3% and 5% of the duty ratio, respectively, of 512-Hz carrier frequency in 20-Vpp driving signal. When the duty ratio is 100%, the full speed of 18 and 16 mm/s are achieved in the X- and Y-axes, respectively. The dimensions of the piezoelectric stage are 61 × 58 × 21.3 (high) mm³.

     

自传感介电弹性体执行器的动力学设计及应用

本文提出了一种传感与作动一体化的介电弹性体(DE)软执行器,可用于薄膜结构形面变形的同步测量和控制.首先,建立DE软执行器电致驱动过程的动力学模型,描述其力电耦合行为.其次,通过开展动态作动实验,辨识该动力学模型的参数.第三,分析不同参数对作动器动态响应的影响,以理解其基本动力学特性.第四,建立DE软执行器自传感过程的简化电路模型,并对其电学参数与位移之间的关系进行实验标定.最后,开展平面薄膜结构的形面位移自适应调整实验,并设计相应的控制策略.实验结果表明,该DE软执行器在作动和传感方面均具有较高精度.因此,其在构建高精度空间薄膜天线方面具有较好的应用前景.     

Fabrication of electrostatic MEMS microactuator based on X-ray lithography with Pb-based X-ray mask and dry-film-transfer-to-PCB process

Lithographie Galvanoformung Abformung (LIGA) is a promising approach for fabrication of high aspect ratio 3D microactuator for dual-stage slider in hard disk drive. However, this approach involves practically challenging X-ray lithography and structural transfer processes. In this work, electrostatic MEMS actuator is developed based on a LIGA approach with cost-effective X-ray lithography and dry-film-transfer-to-PCB process. X-ray lithography is performed with X-ray mask based on lift-off sputtered Pb film on mylar substrate and photoresist application using casting-polishing method. High quality and high aspect ratio SU8 microstructures with inverted microactuator pattern have been achieved with the interdigit spacing of ~5 μm, vertical sidewall and a high aspect ratio of 29 by X-ray lithography using the low-cost Pb based X-ray mask. A new dry-film-transfer-to-PCB is employed by using low-cost dry film photoresist to transfer electroplated nickel from surface-treated chromium-coated glass substrate to printed circuit board (PCB) substrate. The dry film is subsequently released everywhere except anchor contacts of the electrostatic actuator structure. The fabricated actuator exhibits good actuation performance with high displacement at moderate operating voltage and suitably high resonance frequency. Therefore, the proposed fabrication process is a promising alternative to realize low-cost MEMS microactuator for industrial applications.     

Servo signal processing for flying height control in hard disk drives

A novel method of measuring the relative head-medium spacing based on a measurement in the servo sectors is developed and simulated using a read back signal model. The spacing measurement is tested experimentally on a spin stand where the flying height is varied using the resistance heater element in a thermal flying height control slider. In addition, voltage step response measurements were obtained. The data were used to perform system identification and estimate the dynamics of the thermal actuator. The model can potentially be used for thermal flying height control.