Modeling and analysis of a 2-DOF bidirectional electro-thermal microactuator

In this paper, a four hot-arm U-shape electro-thermal actuator that can achieve bidirectional motion in two axes is introduced. By selectively applying voltage to different pairs of its four arms, the device can provide actuation in four directions starting from its rest position. It is shown that independent in-plane and out-of-plane motions can be obtained by tailoring the geometrical parameters of the system. The lumped model of the microactuator was developed using electro-thermal and thermo-mechanical analyses and validated using finite element simulations. The device has been fabricated using PolyMUMPs and experimental results are in good agreement with the theoretical predictions. Total in-plane deflections of 4.8 μm (2.4 μm in either direction) and upward out-of-plane deflections of 8.2 μm were achieved at 8 V of input voltage. The large achievable deflections and the higher degree-of-freedom of the proposed device compared to its counterparts, foresee its use in diverse MEMS applications.     

A universal electromagnetic microactuator using magneticinterconnection concepts

This paper describes a new universal electromagnetic microactuator that makes use of novel magnetic interconnection concepts. In order to realize the universal actuator, planar microinductors are fabricated on a substrate which already contains anisotropically etched Ni/Fe permalloy-electroplated magnetic vias or through-holes. The inductor, which acts as a flux generator, is physically located on one side of the wafer, but is magnetically connected to the opposite side of the wafer where actuation occurs. This approach to actuator design provides for maximum flexibility in the range of applications. In addition, it allows the actuator to be readily connected to driving circuitry without interfering with the actuating device. Multi-layer 3D inductive components are fabricated using a LIGA-like thick photoresist lithography process. The fabricated coils consist of a horseshoe-shaped permalloy-electroplated magnetic core and electroplated copper conductor lines that form the windings around the core. Initial testing using a prototype cantilever beam structure has proven functionality and indicates that the new device has much potential as a low power magnetic microactuator. Many magnetic MEMS applications require an electromagnetic actuator with high efficiency, and some areas which this device is expected to impact include microfluidics, micromotors, optics, and resonating devices     

Fabrication, experiment of a microactuator using magnetic fluid for micropump application

This paper presents the characteristics of the first microactuator using magnetic fluid (MF). MF actuators with flat and corrugated diaphragms are fabricated by the micromachining technique and their deflections are measured. The MF actuator consists of an inductor, a fluid chamber filled with magnetic fluid, and a parylene diaphragm. In the presence of the magnetic field, magnetic fluid easily deforms its shape and generates some pressure. The relation between the MF pressure and magnetic flux density is obtained by the comparison of the deflection for the applied air pressure with that for the MF pressure. At 110 Gauss, the deflection of MF actuator with corrugated parylene diaphragm is more than 200 μm and the generated MF pressure is 2.8 kPa. The successful operation of the first MF actuator shows the high potential for the application to the micromachined devices.     

Piezoelectric unimorph microactuator arrays for single-crystal silicon continuous-membrane deformable mirror

Micromachined deformable mirror technology can boost the imaging performance of an otherwise nonrigid, lower-quality telescope structure. This paper describes the optimization of lead zirconium titanate (PZT) unimorph membrane microactuators for deformable mirrors. PZT unimorph actuators consisting of a variety of electrode designs, silicon-membrane thickness, and membrane sizes were fabricated and characterized. A mathematical model was developed to accurately simulate the membrane microactuator performance and to aid in the optimization of membrane thicknesses and electrode geometries. Excellent agreement was obtained between the model and the experimental results. Using the above approach, we have successfully demonstrated a 2.5-mm-diameter PZT unimorph actuator. A measured deflection of 5 /spl mu/m was obtained for 50 V applied voltage. Complete deformable mirror structures consisting of 10-/spl mu/m-thick single-crystal silicon mirror membranes mounted over the aforementioned 4/spl times/4 4 PZT unimorph membrane microactuator arrays were designed, fabricated, assembled, and optically characterized. The fully assembled deformable mirror showed an individual pixel stroke of 2.5 /spl mu/m at 50 V actuation voltage. The deformable mirror has a resonance frequency of 42 kHz and an influence function of approximately 25%.     

Polymeric magnetic microactuator with efficient permalloy loop design

In the study, two types of polyimide (PI) magnetic microactuator with different geometries were designed, fabricated and tested. Mathematic model is created by ANSYS software to design the two microactuators, respectively. The magnetic field generated by the planar coil with permalloy circuit loop design was simulated by ANSYS software. The simulation result shows that the magnetic force can be up to 34.69 mN. Fabrication of the electromagnetic microactuator combines with 10 m thick Ni/Fe (80/20) permalloy circuit loop deposition, 10 m thick permalloy plate with 800 × 800 m in area on PI diaphragm, high aspect ratio electroplating of copper planar coil with 10 m in thickness, bulk micromachining, and excimer laser ablation. They were fabricated by a novel concept avoiding the etching selectivity and residual stress problems during wafer etching. First, PI diaphragm with micro-electroplated Ni/Fe permalloy was released by anisotropic wet etching, followed by mask projection of 248 nm excimer laser ablation. The new concept of excimer laser ablation process demonstrates that microstructure can be post-ablated after bulk micromachining. By applying a current through planar coil, the PI diaphragm will be actuated. ANSYS software was used to predict the deflection angle of the two types of microactuators. The preliminary theoretical simulation shows a good agreement with experimental result.The authors would like to thank Dr. Tung-Chuan Wu and Mr. M.-C. Chou at MIRL of ITRI in Taiwan for their guidances, and National Science Council (NSC) for their financial supports to the project (granted number: NSC92-2622-E110-009-CC3 and NSC92-2212-E110-029).     

An electrostatic microactuator using LIGA process for a magnetic head tracking system of hard disk drives

 We demonstrate an electrostatic micro actuator which is fabricated by LIGA process. The actuator is designed for a magnetic head tracking system of hard disk drives (HDDs). The actuator is essential to achieve very high track density of HDDs. We realize the aspect ratio of 125 by the LIGA process using a Si-Au mask. We propose to use PMMA molds both as the mechanical structure and as the insulator between electrodes. We believe there are great opportunity for the LIGA process in making micro actuators of HDDs. Received: 25 August 1997 / Accepted: 24 October 1997     

Robust design optimization of electro-thermal microactuator using probabilistic methods

Micromachining of microelectromechanical systems which is similar to other fabrication processes has inherent variation that leads to uncertain dimensional and material properties. Methods for optimization under uncertainty analysis can be used to reduce microdevice sensitivity to these uncertainties in order to create a more robust design, thereby increasing reliability and yield. In this paper, approaches for uncertainty and sensitivity analysis, and robust optimization of an electro-thermal microactuator are applied to take into account the influence of dimensional and material property uncertainties on microactuator tip deflection. These uncertainties include variation of thickness, length and width of cold and hot arms, gap, Young modulus and thermal expansion coefficient. A simple and efficient uncertainty analysis method is performed by creating second-order metamodel through Box-Behnken design and Monte Carlo simulation. Also, the influence of uncertainties has been examined using direct Monte Carlo Simulation method. The results show that the standard deviations of tip deflection generated by these uncertainty analysis methods are very close to each other. Simulation results of tip deflection have been validated by a comparison with experimental results in literature. The analysis is performed at multiple input voltages to estimate uncertainty bands around the deflection curve. Experimental data fall within 95 % confidence boundary obtained by simulation results. Also, the sensitivity analysis results demonstrate that microactuator performance has been affected more by thermal expansion coefficient and microactuator gap uncertainties. Finally, approaches for robust optimization to achieve the optimal designs for microactuator are used. The proposed robust microactuators are less sensitive to uncertainties. For this goal, two methods including Genetic Algorithm and Non-dominated Sorting Genetic Algorithm are employed to find the robust designs for microactuator.     

A linear microactuator with enhanced design

 Based on a previously developed three phase variable reluctance (VR) linear microactuator design features, improving the dynamic properties, were investigated. The active part exhibits, as in the case of its predecessor, permalloy yokes and stator poles with teeth, and is fabricated using thin film technology. Improvements regarding the dynamic motor range were made by varying the number of phases. The new design has substantially improved the dynamic properties, due to the fact that the six phase design greatly reduced the location dependent driving force ripple. Received: 21 May 2001 / Accepted: 30 July 2001     

Performance improvement of an electrothermal microactuator fabricated using Ni-diamond nanocomposite

In this paper, a low-temperature stress-free electrolytic nickel (EL) deposition process with added dispersed diamond nanoparticles (diameter <0.5 /spl mu/m) is developed to synthesize Ni-diamond nanocomposite for fabricating electrothermal microactuators. Device characterization reveals dramatic performance improvements in the electrothermal microactuator that is made of the nanocomposite, including a reduction in the input power requirement and enhanced operation reliability. In comparison with the microactuator made of pure nickel, the nanocomposite one can save about 73% the power for a 3 /spl mu/m output displacement and have a longer reversible displacement range, which is prolonged from 1.8 /spl mu/m to more than 3 /spl mu/m. Furthermore, the nanocomposite device exhibits no performance degradation after more than 100 testing cycles in the reversible regime. The enhancements increase with the incorporation of the nanodiamond in a nickel matrix, so the Ni-diamond nanocomposite has potential for application in MEMS fabrication.     

A micromachined impact microactuator driven by electrostatic force

This paper presents a novel micromachined actuator which is developed to produce precise and unlimited displacement. The actuator is driven by impact force between a silicon micro-mass and a stopper. The suspended silicon micro-mass is encapsulated between two glass plates and driven by electrostatic force. When the mass hits the stopper which is fixed on glass plates, impact force is generated to drive the whole actuator in a nano size step (/spl sim/10 nm). The overall dimension of the device is 3 mm /spl times/3 mm. The driving voltage is 100 V and average speed is 2.7 /spl mu/m/s. The total thickness is 600 /spl mu/m.     

A novel bending microactuator with integrated flexible electro-rheological microvalves using an alternating pressure source for multi-actuator systems

This paper presents a novel bending microactuator with integrated flexible electro-rheological microvalves (FERVs) using an alternating pressure source for multi-actuator systems. The proposed bending microactuator is a fluidic elastomer actuator that has two fluidic chambers inside and can bend with the chamber pressures controlled by the integrated FERVs, each of which has a flexible structure and changes a flow of electro-rheological fluid (ERF) through its viscosity change due to an applied electric field. The utilization of the FERVs in the actuator reduces the overall size, while the benefits of the alternating pressure source are reduction of the number of pipes in a multi-actuator system and removal of the fluid reservoir tank. The mathematical models were demonstrated and utilized for optimizing and designing the dimensions of the actuator to obtain the maximum bending angle, the fast response, and the highest output force. The designed actuator was successfully fabricated using MEMS technologies and experiments were conducted to investigate the bending angle and the response time of the successfully fabricated actuator. The results showed good agreement between the experimental results and the simulation results, which proved the validity of the proposed models. Comparing with the previously proposed microactuator with an FERV, the proposed actuator had 4.5 times larger bending angle. From the results, the optimized actuator showed the feasibility for use in e.g. micro gripper application.

     

A nodal analysis model for the out-of-plane beamshape electrothermal microactuator

This paper introduces a nodal analysis model for the out-of-plane beamshaped electrothermal microactuators. The electrothermal microactuator is traditionally simulated with finite element method (FEM) due to the complex coupling of the electrical, thermal and mechanical problem. This complex problem is classified into two parts in this paper: the coupling electrothermal problem and the coupling thermomechanical problem. By utilizing the characteristic of the temperature distribution, the nodal analysis model for the coupling electrothermal behavior of the electrothermal microactuator is built. The model scale is much smaller than the finite element model, which results in less computational consumption. Then the coupling thermomechanical behavior, such as the shift of the heat flow from the bottom of each part of the actuator to the substrate due to its out-of-plane movement, is modeled to make the model more reasonable. Many other effects which remarkably influence the behavior of the actuator are also taken into account. This model is verified by available experimental results, and achieves an agreement.     

Dynamic bidirectional associative memory using chaotic neurons

A dynamic bidirectional associative memory (DBAM) with chaotic neurons as nodes is proposed. A learning algorithm based on Pontryagin’s minimum principle makes the DBAM equivalent to any other BAM so far reported. The input selection mechanism gives the DBAM the additional ability of multiple memory access, which is based on the dynamics of the chaotic neuron. This work was presented, in part, at the Fourth International Symposium on Artificial Life and Robotics, Oita, Japan, January 19–22, 1999     

A novel radial orientation treatment of nematic liquid crystals using magnetic field lines with permanent magnet and applying the assisted electric field

Recently, there has been considerable research on optical devices, such as liquid crystal (LC) lenses and special optical plates, using LCs. In such devices, relatively small LC cells are frequently used, or unique LC orientations are required. As an LC orientation process, we focused on the LC director's orientation induced by the magnetic force line distribution of a small neodymium magnet. We propose a simple method for obtaining radial orientation, which is rather difficult to obtain using the ordinary rubbing method. The initial orientation in the LC cell is a vertical orientation cell with almost zero azimuth anchoring. With the proposed method, the reorientation process is performed with an assisting electric field and a small permanent magnet, unlike the conventional magnetic field orientation process that requires a large electromagnet. Furthermore, a polymer stabilization treatment is used to fix the obtained radial orientation pattern in the LC cell. After the treatment, the applying voltage can control the tilt angle of the director in weak polymer treatment, and a completely fixed orientation pattern can be obtained that in strong.     

Robot guidance using ultrasonic arrays

The flexibility of robots can be considerably increased by having sensors that can detect the location and orientation of the components that are being manipulated by the robots. Vision systems have been widely applied to this problem, but there has been very little reported work on the use of ultrasonic sensors. This article reports the use of novel ultrasonic sensors that have been manufactured in-house to measure the range and bearing of a target and guide the robot in a pick and place operation. The configuration of the transducer is described as well as the signal processing method employed. Experimental results are given and future developments and applications of the system are described. © 1994 John Wiley & Sons, Inc.     

Romberg integration using systolic arrays

A systolic array is presented to improve numerical approximations to integrals using Richardson's extrapolation procedure in the form of Romberg integration. Two designs are presented, the first is an intuitive linear systolic array, the second, a systolic ring using approximately 1/3 of the cells of the first array. Both systolic arrays have a computation time of 3n cycles, which is a significant improvement on the O(n²) steps required to construct the extrapolation table sequentially.     

Tool wear prediction using convolutional bidirectional LSTM networks

The Journal of Supercomputing - Machine health monitoring systems are vital components of modern manufacturing industries. As advanced sensors collecting machine health-related data become...     

一种新型双向DC—DC变换器

针对传统Buck-Boost变换器存在的输出电压有限、稳定性较差、增益较低等问题,设计了一种采用Z源网络连接直流输入电源和负载的新型双向DC-DC变换器,分析了该新型变换器在功率正向传输和功率反向传输时的工作过程。实验结果表明,该新型变换器能够实现功率双向传输,且在2种功率传输模式下都能实现升压、降压功能;与传统Buck-Boost变换器相比,该新型变换器输出电压更稳定,电压增益较高。     

A feedforward bidirectional associative memory

In contrast to conventional feedback bidirectional associative memory (BAM) network models, a feedforward BAM network is developed based on a one-shot design algorithm of O(p(2)(n+m)) computational complexity, where p is the number of prototype pairs and n, m are the dimensions of the input/output bipolar vectors. The feedforward BAM is an n-p-m three-layer network of McCulloch-Pitts neurons with storage capacity 2(min{m,n}) and guaranteed perfect bidirectional recall. The overall network design procedure is fully scalable in the sense that any number p=/<2(min{m,n}) of bidirectional associations can be implemented. The prototype patterns may be arbitrarily correlated. With respect to inference performance, it is shown that the Hamming attractive radius of each prototype reaches the maximum possible value. Simulation studies and comparisons illustrate and support these theoretical developments.