Tracking control of electrostatically actuated micromirror with closed-loop feedback circuit

Presented is a closed-loop feedback control of an electrostatically actuated micromirror to track a moving light source and to stabilise fast the tilting angle. The micromirror has been designed and fabricated with single crystalline silicon. Tracking and tilt-angle stabilisation has been tested using a position-sensing detector and analogue feedback control circuit. Successful tracking of a moving light source was achieved. The feedback control has been also verified to improve the tilt-angle stabilisation time of the micromirror significantly.     

An electrostatically actuated 1/spl times/2 moving-fiber switch

A 1/spl times/2 moving-fiber switch for optical protection switching is presented. A detailed measurement of the optical performance is given. A coupling loss of 0.5 dB is achieved in the lensless optical path based on butt-coupled standard single-mode fibers. The actuation voltage is approximately 30 V. Both the electrostatic parallel-plate actuators and the fiber alignment structures are realized by anisotropic machining of crystalline silicon. This type of switch is designed for compact rows of switches.     

Effect of temperature on pull-in voltage and natural frequency of an electrostatically actuated microplate

In this paper a model based on distributed parameters has been presented to study temperature effects on the mechanical behavior of an electrostatically actuated microplate. This work consists of two major parts. First part deals with the effect of temperature, stretching and residual stresses on the static instability of an electrostatically actuated microplate. To do this, the governing nonlinear integro differential equation has been derived using Kirchhoff thin plate theory and linearized using step-by-step linearization method (SSLM). The obtained linearized differential equation has been discretized applying finite difference method (FDM). The results obtained have been compared to other existing experimental results and good agreement is observed. In the second part, in order to study the natural or eigenfrequencies of the system, small vibrations of the electrostatically deflected microplate about the equilibrium position have been studied. Here, the governing linear eigenvalue partial differential equation has been solved using a Galerkin based reduced-order model, and the natural frequencies of the microplate have been determined. The results show that temperature changes and residual stress have considerable effects on the system characteristics such as pull-in voltage and natural frequencies.     

Small-signal gain calculations for electrostatically focused klystrons

The small-signal gain of an electrostatically focused klystron (ESFK) will be different from that of a conventional klystron because the drift tube is not dc field free and the RF bunching process is altered. A method for calculating the small-signal gain of an ESFK, based on a space-charge wave analysis of the lens cell, is presented. Calculated and measured values of small-signal gain for several different ESFK's are given.     

Online payload estimation for hydraulically actuated manipulators

Hydraulically actuated manipulators are commonly used for material handling or at construction sites due to the high power density of hydraulic systems. Dig assistance systems or payload monitoring systems for excavators become more common to increase the efficiency and productivity. In this paper, a novel approach for estimating the dynamic parameters of a payload (including the mass) attached to the last link of a hydraulically actuated rigid body manipulator is proposed. Motion equations for the open chain rigid body system including the payload are derived. The motion equations are formulated as a linear regression model exploiting the linearity in the base dynamic parameters. Furthermore, a dynamic model for the neglected closed kinematic chains and the friction is proposed. A least squares optimization problem for minimizing the error between the model based torque and measured torque with respect to the payload parameters is defined. The optimization problem is simplified with assumptions on the center of gravity and the inertia of the payload, which leads to a more robust estimation of the payload mass with a recursive least squares algorithm. Post processing of the estimated payload is suggested and heuristics for the calculation of characteristic values like the accumulated handled mass are shown for the special case of a material handling and an earthmoving excavator. Finally, the novel approach for the payload estimation is validated on both experimental excavators for typical working cycles. The overall performance meets the requirements of  ± 3%.     

Laterally actuated torsional micromirrors for large static deflection

We report on the implementation of laterally electrostatically actuated, torsionally suspended silicon-on-insulator (SOI) micromirrors with a static optical deflection angle of over 40/spl deg/ peak-to-peak. Decoupling the actuator and mirror design allows for large actuator arrays, allowing large dc deflection angle and high resonant frequency to coexist in the same device. The micromirror structures are fully monolithic, micromachined from the front side and back side of an SOI wafer-device layer. In-plane actuation is transformed into out-of-plane motion and rotation, enabling integration of a wide variety of SOI-MEMS sensors, actuators, and micromirrors. When operated in resonance at 1321 Hz, a typical device measured up to 92/spl deg/ peak-to-peak optical deflection at 127 Vdc with 15 Vac amplitude.     

Ultrasonically actuated silicon microprobes for cardiac signal recording

In this paper, we report on ultrasonically actuated silicon thin microprobes that successfully penetrated canine cardiac tissue in vitro, and recorded the electrophysiological signals from multiple sites simultaneously within the heart wall. The penetration force--maximum force encountered by the probe during penetration--is found to reduce with increasing ultrasonic driving voltage, on both excised canine right ventricular muscle and chicken breast muscle. The rate of force decrease varies with tissue type and microprobe dimension. With ultrasonic actuation, the silicon microprobes are inserted into isolated perfused canine heart without breakage or significant buckling, under 10Vpp actuating voltage. Recordings were obtained from isolated perfused canine heart during pacing, following the induction of ventricular tachycardia, and during the transition from ventricular tachycardia to ventricular fibrillation. Local conduction velocity of 0.60 +/- 0.03 m/s was observed from the multichannel recordings from the canine right ventricular wall under epicardial pacing. The application of the ultrasonic microprobes in cardiac electrophysiology study can provide information for reconstruction of electrical wave propagation within the heart, which is important to understanding the mechanisms of cardiac arrhythmias.     

MEMS actuated spherical retroreflector for free-space optical communications

An optical MEMS retroreflective phase modulator comprising a silicon MEMS microactuated platform to which a spherical retroreflector is attached has been investigated. The steady state and dynamic behaviour of the MEMS modulator have been experimentally measured when two different sizes of spherical retroreflectors are used. Dynamic testing shows a dominant resonant frequency response at around 200 Hz, which matches finite-element analysis for the structure.     

Torque-balancing algorithm for the redundantly actuated parallel mechanism

In this work, a joint torque distribution algorithm of parallel mechanism (PM) with one redundant actuator is suggested. The algorithm is effective in avoiding the joint torque saturations. In the algorithm, the force equations are modified into the line equations representing the joint torque solutions. Then, the optimal joint torque distribution is found only by searching the intersections among the line equations. A comparative study of the suggested algorithm with the other typical actuator redundancy resolution algorithms, such as the minimum-norm (MN) torque algorithm, the weighted MN torque algorithm, and a task-priority algorithm, is conducted through simulations and experiments with a 3-DOF planar PM with one actuator redundancy. The simulations and experiments confirm that the suggested redundant actuation algorithm shows an enhanced performance in terms of joint torque limit avoidance and minimum output force/torque distortion over other preexisting algorithms.     

微小型高压力流体电磁控制阀

用于航空航天领域微流量控制系统中的微小型阀,需要具有耐高压、低泄漏、高频响和高控制精度等综合性能。本文提出了一种可控高压力微流体的常闭微小型阀的设计方案用于满足该系统需要,其特点在于采用以较小的致动力控制较高的流体压力的结构原理,并以弹性材料薄膜作为阀芯的支承结构件同时作为密封件。该阀由其本体结构和外置致动器两部分构成,其本体结构的设计在制作工艺上适合进一步的微小型化,外置致动器的设计具有较大灵活性。初步研制了采用电磁致动的小型常闭阀样机既可控气体又可控液体的特性。实验测试其工作压力范围为0～5atm,阀的驱动响应时间小于5ms,流量控制分辨率达到9μL／pulse,无泄露。     

微小型高压力流体电磁控制阀

用于航空航天领域微流量控制系统中的微小型阀 ,需要具有耐高压、低泄漏、高频响和高控制精度等综合性能。本文提出了一种可控高压力微流体的常闭微小型阀的设计方案用于满足该系统需要 ,其特点在于采用以较小的致动力控制较高的流体压力的结构原理 ,并以弹性材料薄膜作为阀芯的支承结构件同时作为密封件。该阀由其本体结构和外置致动器两部分构成 ,其本体结构的设计在制作工艺上适合进一步的微小型化 ,外置致动器的设计具有较大灵活性。初步研制了采用电磁致动的小型常闭阀样机既可控气体又可控液体的特性。实验测试其工作压力范围为 0～5atm ,阀的驱动响应时间小于 5ms,流量控制分辨率达到 9μL/ pulse ,无泄露     

Capacitance engineering for InP-based heterostructure barriervaractor

We investigate new schemes of InP-based heterostructure barrier varactors with the aim of enhancing the capacitance nonlinearity of the devices. Starting from a generic step-like InGaAs/InAlAs/AlAs single barrier heterostructure, planar-doped and buried InAs quantum-well barrier heterostructures were successfully fabricated. It is shown that both solutions lead to more efficient screening of electric field near equilibrium and hence to improvement in the capacitance-voltage ratios with values as high as ~7:1. Under bias, the capacitance modulation is governed by an escaping mechanism in contrast to the conventional depletion operation mode observed for conventional varactors     

Fuzzy tuning PI control for initial levitation of micromachined electrostatically levitated gyroscope

A novel microgyroscope based on UV-LIGA technology is described, in which the wheel-like rotor is levitated and rotated by the electrostatic forces. A simple fuzzy logic scheme for online tuning of PI (proportional integral) controller parameters to improve system robustness of initial levitation is outlined. Experimental results indicate that, with fuzzy tuning, the overshoot is reduced to 17% compared with 27% of the conventional PI controller. The rise time for the two channels of the four is 3.6 ms and the settle time is nearly 25.6 ms, which shows a quick response time and good steady-state performance. From the experiment of 0.5 g pulse acceleration input, sensitivity along axial direction is 1 V g when it acts as an accelerometer.     

Mechanical fatigue analysis of gold microbeams for RF-MEMS applications by pull-in voltage monitoring

This work is focused on the reliability of gold microcantilevers under the effect of mechanical fatigue. A dedicated device for testing the material is designed and built; the material degradation is monitored during the tests by means of a novel technique based on the control of the pull-in voltage of the device, which was demonstrated to be related to the loss of mechanical strength. The fatigue effect is produced through the excitation of the device at a frequency near the resonance; the excitation frequency and the time of actuation are used as a counter for the number of cycles. The lifetime of the device is measured under variable levels of vibration amplitudes; the number of cycles to failure is estimated within a specific range of actuation voltages by means of the W?hler diagram obtained by experiments. The fatigue limit is also estimated following the stair-case method.     

Spindt阴极电容模型

本文用数值方法，计算了Ｓｐｉｎｄｔ阴极的电容，给出了—族曲线，与实验结果比较接近，对真空微电子微波三极管的设计有一定意义。     

用于流体压力测量的电容传感器

叙述了电容应变式流体压力传感器的基本原理，给出了一种电容应变式流体压力传感器的检测电路，并分析了流体压力大小与传感器输出电压的关系。实验结果表明，该传感器具有精度高、线性度好、灵敏度大等优点，尤其适于微压力和大动态力的测量。     

先进的阻抗与电容测量转换器

本次在线座谈主要介绍了ADI先进的阻抗与电容测量转换器的原理及应用。本文包括两部分内容：第一部分主要讨论阻抗转换器,第二部分主要讨论电容转换器。在这两部分中,我们先回顾电阻和电容测量方法的主要特点,然后介绍ADI针对这两种应用推出的先进的阻抗数字转换器及电容数字转化器。     

Real-time state estimation for spatial six-degree-of-freedom linearly actuated parallel robots

This paper presents a novel numerical method, Global Newton–Raphson with Monotonic Descent algorithms (GNRMD), to solve the effectively real-time spatial 6-DOF states of parallel robots in practice. Based on geometrical frame of parallel robots, the highly nonlinear equations of system states estimation are obtained using analytical approach. GNRMD algorithms modified from Global Newton–Raphson method are developed to solve the nonlinear equations in real-time application. The procedure of GNRMD algorithms are programmed in MATLAB/Simulink, and then compiled to a real-time PC with Microsoft Visual Studio .NET for implementation. Applying the proposed algorithms, the real-time spatial 6-DOF states of the parallel robots are estimated. In addition, the performances, accuracy, convergence, property of real-time and effectiveness, of the proposed method are analyzed and verified in experiment and theory. Furthermore, the presented algorithms are used in a DOF control scheme of parallel robots. Simulation and experimental results show the proposed algorithms are effective and feasible for spatial states estimation of parallel robots, and are suitable for a real-time control system required accurate feedback of system states.     

Model-based feedback controller design for dual actuated atomic force microscopy

In atomic force microscopy (AFM) the imaging speed is strongly limited by the bandwidth of the feedback loop that controls the interaction force between the measurement tip and the sample. A significant increase in closed-loop bandwidth without sacrificing positioning range can be achieved by combining a long-range, low-bandwidth actuator with a short-range, high-bandwidth actuator, forming a dual actuated system. This contribution discusses the design of a model-based feedback controller that controls the tip-sample force in dual actuated AFM. Special emphasis is given on guaranteeing robust stability of the feedback loop under influence of variations in the dynamical behavior of the system, and to prevent strong destructive interference between both actuators. To prevent instability of the feedback loop due to saturation of the short-range actuator, an anti-windup controller is presented that robustly stabilizes the system under all imaging conditions. The designed feedback controller is implemented on a prototype dual actuated AFM system, and demonstrates a disturbance rejection bandwidth of 20 kHz, which is about 20 times faster than the model-based controlled single actuated system. AFM images are obtained verifying a significant reduction of force variations between the tip and the sample while imaging. The faster control of the tip-sample force reduces the residual tracking error and, thus, reduces the chance of damage or wear of the tip and the sample, and allows for faster imaging.