Key Engineering Materials Vols. 562-565

Abstract: The liquid floating rotor gyro is a gyroscope using electrostatic or electromagnetic forces to levitate rotor, and filling rotor-stator cavities with liquid in order to improve stability of motion. Under influence of the relative surface roughness, rotor velocity, dimension of flow field and fluid nature, flow characteristics of cavity flow field vary under different boundary conditions and geometrical conditions. This paper adopts three-dimensional model and periodic boundary conditions to conduct numerical modeling on cavity flow field. Its results show that, with velocity rising, distribution of flow field speed and pressure manifests partial fluctuations in turbulent-flow-intensive area; resistance torque amid rotor rotation is nonlinearly correlated with velocity, whose rules can be obtained through high-order curve fitting.

Abstract: The micro in-pipe robot is widely used in the industrial inspection, maintenance, and cleaning of petrochemical, refrigeration and nuclear power plants. The mobile mechanism, data acquisition and processing technology of micro in-pipe robot have high practical value and academic significance. A 60mm diameter in-pipe robot with spiral wheel structure is designed, which has the advantages of simple principle, compact structure and convenient control. Its screw wheel moving structure ensures the robot has a large traction and movement speed. DSTJ-3000 intelligent differential pressure sensor is equipped with the micro in-pipe robot, which collects action data to the microcontroller C8051F330. Data is transferred to the PC through the wireless Bluetooth module, processed and displayed by Visual Basic application program. Screw wheel micro in-pipe robot control system can freely control its forward, backward, speed adjustment, and self-locking through the PC software.

Abstract: The paper mainly designs an efficient MEMS electrothermal actuator, with lower voltage input but large displacement output. The calculation method of the actuator considers the convection and radiation besides heat conduction mentioned in most literatures. With the multiphysics simulation by the software Comsol of electrothermal bimorph actuator, the transient effects of thermal convection and thermal radiation on the actuator displacement and the response characteristics of an actuator with a separate heating layer were studied.

Abstract: This paper is concerned with the parametric identification based on immune particle swarm optimization (IPSO) algorithm for Bouc-Wen model of piezoelectric ceramic actuators (PCA). IPSO algorithm is an algorithm that introduces the immunological memory and selection mechanism of concentration of antibody of immune system to PSO algorithm. It is used to identify unknown parameters of Bouc-Wen model, one of the most widely used parametric models of hysteresis in mechanics. The experimental results reveal that IPSO algorithm has better precision and convergence.

Abstract: This paper mainly proposes a chaos particle swarm optimization (CPSO) to estimate the parameters of piezoelectric actuator (PEA), in which Bouc-Wen model is employed to describe the hysteresis phenomenon. By introducing chaotic disturbance to the simple PSO, this method can obtain optimal solution with high calculation efficiency. Finally some experiments are conducted to demonstrate its feasibility and effectiveness.

Abstract: For the problems of the oversized voltage and undersized displacement in the electrostatic micro actuator of transverse loading recently, a silicon micro actuator model with characteristics of large-displacement and low-voltage is presented based on the principle of vertically-horizontally bending. The deflection equation of the micro actuator is derived. The axial static electricity, temperature stress and axial squeezing pressure on the deformation of micro-beam are analyzed. The simulation shows that the displacement is as big as 17.5μm when the driving voltage is as low as 5V. The displacement is much larger than the deformation of the current micro actuator.

Abstract: As the power producer, the micro actuator is an important part of the micro electro- mechanical system, which is used as the conversion of energy, motion and force producing. In this paper, the mechanical models of three bent beam electrothermal actuators are summarized to make comparison with each other and analyze mechanical performance. For Π-shaped actuators, the tip displacements are proportional to temperature increment and length, having no relationship with the beam width and thickness. However, the displacement of Π-shaped actuators is smaller than the one of V-shaped actuators with the same parameters. For V-shaped actuators, the tip displacements of cascaded V-shaped actuators are larger than the ones of single V-shaped actuators with the same parameters. Especially, cascaded V-shaped actuator with secondary beam having no current has the largest displacement.

Abstract: A novel microactuator based on photothermal expansion is introduced, which is actuated by laser beam eliminating external circuit. The mechanism of the photothermal expansion is theoretically analyzed, and the working principle of a U-shaped photothermal microactuator with two arms is introduced and the lateral deflection is calculated. LIGA technology involving X-ray lithography and electroplating is introduced to fabricate photothermal microactuators. The fabrication process with LIGA technology is introduced and important details such as X-ray mask and electroplating are discussed. Photothermal microactuators with different structures are fabricated by LIGA technology at Beijing Synchrotron Radiation Facility (BSRF) and tests are carried out with laser beam. The deflection of a V-shaped photothermal microactuator of Ni material can reach 25.8 μm under the control of a 1064 nm, 800 mW laser and a U-shaped can reach about 11 μm at an 808 nm, 600 mW laser.

Abstract: A smooth and flexible carbon film was prepared via liquid exfoliation method followed by liquid evaporation using the natural flake graphite as the starting material. The XRD and Raman results demonstrated that the obtained film is composed of chemically reduced graphene, graphene oxide and graphite. The thermal transport property of the as-obtained film was investigated by light flash measurements. It is found that the as-obtained graphene-containing composite film has a high in-plane thermal diffusivity (2157 m²/s), and the corresponding thermal conductivity (754 W/m K) is higher than the other metal and normal graphite materials, which is very promising for applications requiring 2D heat conduction.

Abstract: In₂O₃/multi-walled carbon nanotube (MWCNT) nanocomposites containing different MWCNT contents were synthesized via direct growth of In₂O₃ nanoparticles on the functionalized MWCNTs. The nanocomposites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The results exhibited that In₂O₃ nanoparticles with a diameter of approximate 10 nm were densely decorated on the surface of the MWCNTs. The gas sensitive performance of the nanocomposites to ethanol was also investigated. It was found that In₂O₃/MWCNTs sensor showed much higher response than that of the pure In₂O₃ sensor. Moreover, the sensing mechanism was discussed.