Symmetry and asymmetry from MEMS variable capacitor by nonlinear micro stoppers

Mechanical stoppers in MEMS capacitive systems can dramatically affect electrical performances and result in complicated mechanical dynamic responses. This paper introduces electromechanical coupling nonlinear dynamic responses in MEMS variable dual-capacitor with an effect of nonlinear and asymmetrical stoppers. We found that the capacitance in the electrical circuit system related to the first-order derivative of the output voltage on a load resistor, and the variable dual-capacitor was strongly affected by the coupling of up and down superposition instantaneous electrostatic force and limited space by the length of nonlinear stoppers. The numerical calculation results and the experimental results in our analysis based on our system had a good agreement, and the numerical simulation results presented rich nonlinear impacts dynamic responses through the imposed voltage and the height of stoppers in MEMS variable dual-capacitive device. The device in operation cannot reach the 0.6 time's initial gap due to small forcing amplitude (1.026 g). However, we observed that the movable plate and stoppers (across the 0.6 time's initial gap) had fierce impacts due to big forcing amplitude (4 g) on to the device. With asymmetric stopper each impact, we also concluded that the movable plate would experience attenuations of the displacement until the moment to the next impacts. Moreover, the height of stoppers can not only result in complicated dynamic motion of the movable plate, but also can modulate a voltage of the fixed plate with its asymmetry structure.

Study on the formability by TPIF technology for aluminium sheet at room temperature

Two Point Incremental Forming technology (TPIF) is one forming method of incremental sheet forming technology (ISF) which is an innovation sheet forming process with potential advantages such as simplicity, less-time consumption, and high flexibility. This technology using a hemispherical-end tool under CNC movement deforms a metal sheet which is fixed on simple frame. The sheet metal clamped between movable plate and clamp plate, under the metal sheet has a support die which is fixed on bottom plate. The lower plate is firmly positioned on the CNC machine table in while upper plate (included sheet material, movable plate and clamp plate) is able to move easily up and down along guide bars. The sheet material is plastically deformed layer by layer until final-shape product by CNC tool path. This technology is very suit for the rapid prototyping process and the low batch production. In this research, formability of the TPIF process due to operating parameters was investigated with aluminum sheet at room temperature. Four operating parameters such as depth step, feed rate, tool diameter, and spindle speed, was considered their effects on the formability of TPIF process through DOE strategy. The forming results showed that TPIF process for metal sheet material at room temperature has potential applicability in the metal sheet-product manufacturing.

Error Comparison and Analysis of Parallel and Constraint Mechanism for 3-TPS Hybrid Machine Tool

This paper establishes position error model based on parallel robot kinematics theory, and analyses position error of the 3-TPS hybrid machine tool. Firstly, to calculate position error of the movable plate caused by the parallel mechanism links, through error model of the parallel mechanism which is established through inverse kinematics of the hybrid machine tool. Then, according to the error model of constraint mechanism established by transformation matrix method, the position error has been simulated and calculated. Finally, this paper compares the effects of both mechanisms. The analysis indicates the link error of constraint mechanism has more influence on movable plate posture than parallel mechanism, and provides help with motion error compensation and kinematic calibration.

Active Sloshing Control by Using Movable Plates Device Based on Flow Control Method

This paper deals with an experimental study of an active control technique for the suppression of sloshing based on flow control in the tank. In this paper, we proposed the active feedback control method by using movable plates which are set in liquid. In the experiment, the present method is applied to the 2-dimensional problem of sloshing which occurs in the rectangular tank due to a horizontal excitation. The sloshing are suppressed by the active feedback to the rotation of the movable plate installed in liquid. The suppression performances are examined by changing the phase difference between the control signal of rotation angles of the movable plate and the liquid surface displacement (phase-shift). The performance of proposed method is evaluated by the time history, the root mean square value and frequency-response of the surface wave displacement under the active feedback control. Moreover, the effects of movable plate number and installation position on the suppression performance are clarified. On the other hand, the visualization experiment is conducted to obtain the flow pattern in the tank when the sloshing is controlled by the present method. The decreasing mechanism of the surface wave is discussed by the result of the visualization experiment. As a result, it is shown that the proposed control devics and active control method suppress the sloshing effectively. Furthermore, it is found that the changes of flow pattern by the drive of movable plate cause the suppression of sloshing in the visualization experiment.