Novel piezoelectric actuator control slider using transverse-mode deformation

This work proposes a novel structure design of active slider with a piezoelectric actuator at the top of the slider body and a soft layer between the substrate and head elements, to efficiently control the flying height of slider. A parametric simulation was performed to obtain an optimize dimension of PZT actuator and the most efficient soft material. Then three types of slider structures were designed and investigated with considering air bearing effects to achieve large actuation efficiency.     

Microfabricated Lamb wave device based on PZT sol-gel thin film formechanical transport of solid particles and liquids

The fabrication using silicon micromachining and characterization of an acoustic Lamb wave actuator is presented. The intended use of the device is for mass transport and sensor applications. The device consists of dual interdigitated transducers patterned on a thin-film composite membrane of silicon nitride, platinum, and a sol-gel-derived piezoelectric ceramic (PZT) thin film. The acoustic properties of the device are presented along with preliminary applications to mechanical transport and liquid delivery systems. Improved acoustic signals and improved mass transport are achieved with PZT over present Lamb wave devices utilizing ZnO or AlN as the piezoelectric transducer     

Design and experimental validation of a linear piezoelectric micromotor for dual-slider positioning

In this paper, a linear piezoelectric micromotor for dual-slider positioning by a single piezoelectric element (PZT) is proposed. A slider 1 and a permanent magnet are connected by the PZT, and a slider 2 is placed on the permanent magnet by the magnetic force. The slider 1 is a small steel cuboid and can be clamped and released by an electromagnet base. When it is released, it can be driven by impact friction force generated by the PZT. When it is clamped, it keeps stationary, and the slider 2 can be positioned based on the smooth impact friction drive of the micromotor. Both the sliders can be positioned independently with a long motion range as well as a high positioning resolution. Due to a single PZT used in the micromotor and miniaturized design of the mechanism, the proposed micromotor has been constructed with a compact size as well as a relatively high loading capacity.

     

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.     

What happens turning a 250-μm-thin piezo-stack sideways?

Usually when piezoelectric membrane actuators are mentioned, one classically thinks of a passive membrane with a piezoelectric actuator on top. In this paper omitting the passive membrane will be suggested. Therefore, the piezoelectric actuator will not be commonly designed as plate capacitor structure, such as that the piezoelectric material sitting between two plate electrodes. Rather will the actuation be caused by structured surface electrodes on only one side of the piezoelectric material, leaving the opposite side free of potential. Several surface electrode designs, starting with interdigital parallel structures, known from surface acoustic wave transducers, spiral and ring structures, ending with star-shaped structures, are tested. The main advantage of this actuation principle is that with the varying electrode design it became possible to also generate an upward movement, i.e., in the direction of electrode side of the membrane. This upward movement has not been achieved with any piezoelectric membrane actuator so far.     

Piezoelectric linear motor with unimorph structure by co-extrusion process

A new piezoelectric linear motor was developed using a ring-shaped, unimorph stator composed of a piezoelectric active layer (0.3PZN–0.7PZT/Mn) and a conductive passive layer (0.3PZN–0.7PZT/Mn/Ag). The stator was prepared by co-extrusion followed by the thermoplastic green machining (TGM) process. After co-extruding the piezoelectrically active and passive layers together, they were machined into a ring shape and then sintered at 930 °C for 4 h. The stator was poled in the thickness direction and operated in radial vibration mode. A glass rod was used as the moving shaft. When a saw-tooth electric field was applied, the shaft moved linearly as a result of the stator's bending motion. When an inverted saw-tooth electric potential was applied, the shaft moved linearly in the opposite direction. The velocity of the piezoelectric linear motor was about 4 mm/s at an applied voltage of 80 V_p–p and a resonance frequency of 36.5 kHz.     

Modal analysis of a unimorph piezoelectrical transducer

Piezoelectric transducers are widely applied to MEMS devices as actuators or sensors due to their simple structure and easy control. A micromachined piezoelectric microjet is introduced and modal analysis of its piezoelectric actuator has been thoroughly presented. Both numerical analysis and experimental measurement are implemented in this study. In numerical analysis, an approximate method is established to evaluate the first vibration mode and finite-element methods are used to simulate higher order vibration modes of the transducer. An experimental system was also set up to measure the axisymmetric vibration modes of the transducer. Compared with experimental results, good correlation was found between the numerical and experimental results, which proved the validation and reliability of the models. Through these models, further optimal design of the transducer can be carried out.Financial support by National Natural Science Funds (29833070) and National 973 Basic Research Projects (G1999033106) of China is deeply appreciated.     

Design and control of a single-stage dual-actuator system for high-precision manufacturing

This paper proposes a design for the linear state feedback control of the dual-actuator system, which is a dual-input single-output system for the high-precision manufacturing stage. The proposed control prevents saturation or reduces the unnecessary movement of the piezoelectric (PZT) actuator at the transient response by tracking the error between the estimated and actual positions of the coarse-actuator system at each control sample. Also, a new mechanism of the single-stage dual actuator is introduced. The axes of the stepper motor and the PZT actuator are co-axial. The coupling effects between the stepper motor and the PZT actuator are considered. Both the simulation and experiment results show that the proposed algorithm successfully prevents unwanted motions of the PZT actuator at the transient response. The experiment results show that the settling time and overshoot were enhanced by 45.7 and 95.9 %, respectively, for the proposed algorithm when the reference distance was 10 μm, which exceeds the stroke of the PZT actuator.     

Design and simulation of an ultrasonic linear motor with dual piezoelectric actuators

In this study, an ultrasonic linear motor with dual piezoelectric (PZT) actuators is developed. A traveling wave motion is generated on the stator by a double-sided excitation of the stator of the ultrasonic linear motor, which drives the slider that is connected to the stator. The development and design processes are described. In this paper, the principle of using an ultrasonic motor to drive a traveling wave type is presented. The structure for the ultrasonic linear motor is then demonstrated with its dimensions, driving conditions and material parameters, so that Computer-Aided Engineering (CAE) can be used to simulate the driving performance. The simulation results show the differences to the characteristics that are achieved by adjusting the critical parameters, such as the PZT boned positions, the excitation frequency and the preload, in order to derive the best design. A prototype that uses the best parameter design is presented, and a method to improve development processes is presented in the final section.

     

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.     

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.

     

Modeling characterization and optimization design for PZT transducer used in Near Field Acoustic Levitation

An acoustic actuator with large radiation surface has been used in a non-contact levitation system. The actuator is composed of a Langevin transducer and a disk-shape radiator. A comprehensive modeling approach has been developed to simulate electrical and mechanical characterization. A coupled-field finite element analysis has been performed considering the vibrator with flexural mode. Identical experimental conditions were used in the simulation to investigate size effect and optimize the transducer design. The stimulated results show good agreement with experimental measurements. This model may be employed to facilitate the analysis and optimization of Near Field Acoustic Levitation transducer assemblies. Moreover, this paper demonstrated the important role that modeling plays in the design, fabrication and optimization of coupled transducers.     

Swing-arm-type PZT dual actuator with fast seeking for optical disk drive

 In this paper, a swing-arm-type dual positioning mechanism using a voice coil motor (VCM) and bimorph PZT actuators is proposed for the possible application to the future optical disc drive actuator. A VCM is used as a coarse motion actuator, and a set of piezoelectric actuators is used for fine motion. The two pairs of PZT actuators are arranged in parallel and are carefully designed to deflect in `S' shape such that tension and compression forces are generated simultaneously and thus the hysteresis is minimized. The static and dynamic analyses are performed and the parameter studies on the key dimensions of the set of PZT actuators are investigated. For fast seeking motion, time optimal control scheme combined with PD algorithm is adopted for the fast seeking motion of VCM. Positive position feedback (PPF) control is used to suppress residual vibration for the PZT actuator beams by activating it at the end of VCM swing motion. The feasibility of the suggested actuator system and the control scheme is demonstrated through simulations and experiments. Received: 5 July 2001/Accepted: 21 December 2001     

Integration of displacement sensor into bulk PZT thick film actuator for MEMS deformable mirror

Bulk PZT thick film actuator integrated with displacement sensor, the so-called self-sensing actuator, is presented in this paper. The PZT film is used as not only an actuating layer but also a displacement sensor, which is achieved by dividing the electrode on the top surface of the PZT film into two parts: central top electrode for actuating and outer annular sensor electrode for piezoelectric displacement detection. When the actuator moves, the piezoelectric charge is induced in the outer annular PZT due to the piezoelectric effect. The total amount of accumulated charge is proportional to the stress acting on the PZT, which is in turn proportional to the actuator displacement. By collecting the piezoelectric charge, the actuator displacement can be detected. A theoretical model is proposed to determine the structure parameters of the sensor and predict the sensor sensitivity. Experiments were performed on the micro-fabricated sensor integrated PZT thick film actuator, and the measured piezoelectric charge is close to the theoretical predictions. The integrated piezoelectric sensor has a displacement sensitivity of approximately 4 pC/nm. In addition, the integration of displacement sensor into the actuator needs no additional fabrication process and has no influence on the actuator performances.     

Enhancing displacement of lead-zirconate-titanate (PZT) thin-film membrane microactuators via a dual electrode design

A common design of piezoelectric microactuators adopts a membrane structure that consists of a base silicon diaphragm, a layer of bottom electrode, a layer of piezoelectric thin film, and a layer of top electrode. In particular, the piezoelectric thin film is often made of lead-zirconate-titanate (PZT) for its high piezoelectric constants. When driven electrically, the PZT thin film extends or contracts flexing the membrane and generating an out-of-plane displacement. Many manufacturing defects, however, could significantly reduce the designed actuator displacement. Examples include residual stresses, warping, non-uniform etching of the silicon diaphragm, and misalignment between the top electrode and the silicon diaphragm. The purpose of this paper is to develop a dual top-electrode design to enhance the actuator displacement. In this design, the top electrode consists of two disconnected (thus independent) electrode areas, while a continuous bottom electrode serves as the ground. The two top electrodes are located in two regions with opposite curvature when the diaphragm deflects. When the two top electrodes are driven in an out-of-phase manner, the actuator displacement is enhanced. Finite element analyses and experimental measurements both confirm the feasibility of this design. When manufacturing defects are present, experimental results indicate that the actuator displacement can be optimized by adjusting the phase difference between the dual top electrodes.     

Distributed structural identification and control of shells using distributed piezoelectrics: Theory and finite element analysis

Distributed dynamic identification and vibration control of high-performance flexible structures has drawn much attention in recent years. This article presents an analytical and finite-element study on a distributed piezoelectric sensor and distributed actuator coupled with flexible shells and plates. The integrated piezoelectric sensor/actuator can monitor the oscillation as well as actively control the structural vibration by the direct/converse piezoelectric effects, respectively. Based on Maxwell's equations and Love's assumptions, new theories on distributed sensing and active vibration control of a generic shell using the distributed piezoelectrics are derived. These theories can be easily simplified to account for plates, cylinders, beams, etc. A new piezoelectric finite element is also formulated using the variational principle and Hamilton's principle. A piezoelectric micropositioning device was first studied; analytical solutions are compared closely with experimental and finite-element results. Distributed vibration identification and control of a zero-curvature shell-a plate-are also investigated.     

压电谐振驱动三足机器人的平面运动

设计并实现了一类利用压电陶瓷片作动,由三条曲梁足支撑的振动驱动机器人.建立了在一条足共振驱动下机器人水平运动的动力学方程,数值计算解释了摩擦作用下的运动机理,寻找到异性摩擦对运动方向、速度的影响和压电激励频率与运动速度间的关系.通过建立圆弧曲梁控制方程求解圆弧型足面内振动的固有频率及振型,设计了三组不同频率的圆弧曲梁足参数,实验制作了机器人模型,利用压电控制三足间振动的共振切换,实现了预想的三个方向的运动以达到平面运动的效果,实验测量了机器人的运动速度与理论计算吻合得较好.     

采用复合磁电换能器的振动能量采集器研究

采用Teffenol-D/PZT/Terfenol-D复合磁电换能器,设计了一种新型振动能量采集器.采集器由悬臂梁、磁电换能器和永磁体三部分组成,环境振动引起换能器与永磁体相对运动,使得作用到换能器的磁场变化,变化的磁场引起Tedenol-D产生应变,应变传递到PZT得到电输出.采用等效磁荷理论分析了影响换能器与永磁体相对运动的磁场力;并用林滋泰德-庞加莱法分析了永磁体的非线性运动情况.实验结果表明,在振动激励频率为33 Hz,加速度为0.5 gn时,输出电压峰峰值45.1 V,输出功率112.1μW.     

Active-head slider with piezoelectric actuator using shear-mode deformation

The active-head slider technology for hard disk drive is one of the most promising means to decrease flying height. This paper describes a piezoelectric flying height control slider which has a faster dynamic response compared with conventional active-head sliders. This slider can be also adapted to the conventional slider-fabrication process. PZT layer located near the magnetic head has shear mode deformation by applying electric voltage between the upper and lower electrodes when the flying height of magnetic head needs to be decreased or increased. We fabricated a prototype with single crystal Si substrate for feasibility study. Our evaluation of the prototype revealed that the piezoelectric constant of the shear mode deformation was 0.88 nm/V, and the dynamic response was 50 kHz. The shape of the air bearing surface was optimized by simulations using a robust design method. We found that the stroke was 8 nm for an applied voltage of 11 V if the flying height was 11 nm with no deformation in PZT.     

Settling control with reference redesign for dual actuator hard disk drive systems

This paper considers settling control of a recording head for a dual actuator system for hard disk drives consisting of a coarse actuator (voice coil motor, VCM) and a fine actuator (peizoelectric transducer, PZT). The design method proposed in this paper is called the dual actuator reference trajectory re-design (RTRD). In this method, the design is divided into three steps. In the first step, the coarse actuator loop is designed to achieve stability and basic performance. In the second step, the fine actuator path is designed by loop shaping for superior performance of the overall system. Finally, the reference signals are generated for both the coarse and fine actuators by minimizing the square integral of jerk during the transition. The reference signals are updated or redesigned in real time as the recording head approaches the target track for smooth landing and minimal residual vibration. The “soft switching” technique is applied for gradually introducing the fine actuator (PZT actuator), which may shorten the settling time and achieve a smooth settling response. The effectiveness of the proposed approach is evaluated by simulations.