Key Engineering Materials Vols. 609-610

Abstract: This paper presents a micro induction heater based on the principle of induction heating. The liquid contact with the micro heater core directly and heated by the eddy current effect. The heating effect of the micro heater is simulated with the software of COMSOL. The simulation results indicate that the temperature of the micro heater core can reach to 540K in 0.9s while the current is 0.7A and the power frequency is 200 kHz. The relations between the heating effect and the micro induction heaters parameters such as the current, the AC power frequency and the coils parameters are studied in the simulation respectively. The prototype of the micro heater has been fabricated and the experimental test has carried with the micro heater. The experiments indicated that the micro heater can generate thermal bubble in 0.3s while the 1.0A high frequency current passes through the heater coil. The micro induction heater can be applied to a variety of thermal bubble devices, such as micro injector, micro switch and micro pump.

Abstract: This paper presents an efficient methodology for automated optimal tailoring actuation voltage waveform of MEMS switches aiming at eliminating the detrimental contact bouncing effect to speed up the switching process and improve the mechanical reliability. This is a simulation-based approach where genetic algorithm (GA) is used in combination with a dedicated mechanical model of MEMS switch to derive optimal actuation waveform. The proposed technique has been implemented in SystemC-A, which is extremely well suited for complex modeling, implementation of post-processing of simulation results and optimization algorithms. Effectiveness of proposed approach is corroborated by a practical case study of automated actuation waveform design for a prefabricated DC-contact MEMS switch. The experimental results show that the switching time of the switch by employing optimized actuation voltage waveform is dramatically reduced to 60μs from 95μs, while the bouncing effect is successfully eliminated.

Abstract: In order to improve the conventional industrial brake temperature measurement and put forward new methods, measurement schemes can apply nanotechnology and nanomaterials to industrial brake temperature measurement, so that the researchers would get more accurate temperature field for analyzing the effect of temperature change on braking performance in experimental environment, and in engineering field, it can also measure and monitor braking process in real time to prevent accidents. In this paper, the author analyzes the advantages and disadvantages of the conventional industrial brake temperature measurement, and then puts forward a infrared temperature measurement scheme based on nanostructured ceramic coatings, and some suggestions on the application of nanofilm and thermoelectric conversion nanomaterials in new sensor field.

Abstract: In the Precision control industry, Due to a strong hysteresis characteristics of MSMA actuators between input and output , the positioning accuracy of the drive have been affected seriously, and its wider application limited.In order to improve the positioning accuracy of MSMA actuators, to eliminate or reduce the hysteresis characteristic,in this paper ,hysteresis compensation for MSMA actuators is proposed ,three methods like traditional PID feedback ,and feed-forward compensation ,and composite control with PID and feed-forward compensation ,these three methods are compared . results show that the composite control has better control performance,the MSMA actuators control accuracy kept in 0.8% range.

Abstract: In this paper a high-order sigma-delta modulator applied in micro-accelerometer is designed. The modulator chooses the distributed feedback structure. And the signal bandwidth is 500Hz, the oversampling ratio is 250 and sampling frequency is 250KHz. By the MATLAB Simulink simulation, when the input signal is 1g, and the signal frequency is 250Hz, the simulation result is that the noise level is-160dBV at the signal frequency in the ideal situation. And when considering the non-ideal factors, the simulation result shows that the noise level at the input accelerated signal is 20dBV higher than the ideal. The overall circuit was implemented under 0.5 um CMOS process and simulated in Cadence Spectre. The final simulation results show that the signal to noise ratio (SNR) is 97.1dB.

Abstract: A sliding-mode control (SMC) scheme based on hysteresis observer is designed in this paper for precision trajectory tracking of piezoelectric actuators. A mathematical model considering the dynamics of a mass-spring-damper trio and the hysteresis friction force describing the parameters of bristle stiffness, damping and viscous is proposed. A lumped uncertain function composed of the mechanical parameters, displacement and its deriviation, hysteresis friction force and external load force is estimated by a hysteresis observer. An asymptotically stable sliding surface is defined. Lyapunov stability theory is applied to guarantee the asymptotical stability for the trajectory tracking error. Experiments are conducted to validate the effectiveness of the proposed method. Results show that a satisfied tracking response to a sinusoidal trajectory is achieved, and the positioning errors under a triangle scanning contour are dramatically reduced compared with the traditional SMC.

Abstract: We report here the design and fabrication of an electromechanical tunable grating on silicon-on-insulator (SOI) wafer. The tunable grating consists of a submicron electrostatic comb actuator and an expandable freestanding grating. Rigorous coupled-wave analysis (RCWA) method is utilized to analyze the optical responses of freestanding grating with different periods and filling factors. Obvious shift of the resonant peaks is obtained by changing the grating period and the grating filling factor. The electromechanical tunable grating is realized on the silicon device layer by a combination of electron beam (EB) lithography, deep reactive ion etching (DRIE) and wet etching. Scanning electron microscope (SEM) micrographs indicate that the grating is well fabricated. Via applying biased voltage, the force generated by the electrostatic comb actuator can modulate periods and filling factors of the freestanding grating. The electromechanical tunable grating with simple fabrication process shows bright prospects for optical telecoms and miniaturized spectrometers.

Abstract: Sliding Mode Control (SMC) based on exponential switching law for electromagnetic actuation MOEMS mirror was proposed. This technique relies on the movable mass and the dynamics of the sliding surface. In such a way, the generated actuation tracks possible changes in the mechanical behavior induced by external factors (humidity, temperature, pressure, etc.). Stability of the proposed method is proved by Lyapunov second method. The system level model is established and simulated using MATLAB/Simulink. Simulation results show that: the scanning angle converges to reference value in only 0.45 seconds when using exponential switching law, which is decreased 55% compared with that using proportional switching law, and the sliding surface is much smooth too; the tracking error less than 0.25%, and sliding surface jittering in the range of 0.5. The proposed SMC controller can realize accurate control of mirror and having high performance and robustness in the presence of external disturbances and also can be applied to the closed-loop control of other vibrating devices.

Abstract: A novel type of single use bi-stable MEMS solid off-on switch based on metal bridge igniter is described and its performance test results are presented. The switch mechanically connects a couple of comb electrodes which belong separately to different metallic lines. Switching between the two stable states (off and on) is accomplished by a voltage pulse supplied by an energy storage capacitance through a metal bridge igniter above the electrical lines to be connected. The switch can be driven by external signal and its predicted lifetime is very long, therefore the switch can be used for long term store systems.

Abstract: An orthotropic piezoelectric fiber composite (OPFC) element and related OPFC ultrasonic phased array transducer which applied in damage detection of metal structures are investigated by theoretical analysis, numerical simulation and experimental verification methods. Based on electromechanical coupling, the influence of the material characteristics and geometry parameters on actuation performance is studied for the thickness expansion type OPFC elements. In view of lack in the mechanic-electronic parameter design of the existing single PZT element for modern ultrasonic phased array transducer, the related OPFC ultrasonic phased array transducer which used in metal structural damage detection is designed, which have the merits such as low voltage and limit the effects on grating lobe. The focusing acoustic field distribution is analyzed by finite element method together with directivity analysis in metals. The optimal array parameters such as phased array element interval, array element width and number of element are obtained by studying the total displacement changes as various parameters changes at focus point. The preparation of OPFC actuator used in metal structural damage detection is studied. The performance of interdigital OPFC element is also obtained by testing and comparing with the traditional PZT element. The experimental results displayed good agreement with the theoretical predictions.