Papers by Author: Ying Hu

Abstract: Based on the proposed 4PUS-1RPU parallel mechanism a 5-axis Parallel Kinematic Machine (PKM) scheme has been developed and the dynamic characteristics of the PKM have been investigated in detail. To avoid the intensive computation caused by finite element analysis in the research, two typical metamodeling techniques of Response Surface Methodology (RSM) and its artificial neural network enhanced technique were employed as the robust design approaches. Comparing the results obtained from the direct RSM the modeling accuracy by the artificial neural network enhanced RSM can be improved.

Abstract: In this paper, a novel parallel mechanism (3-RRRS/UPR) used in flexible fixture with configuration composed of two parallel robots (2-RR and 3-RRRS/ UPR) is presented. First, system modeling including the mobility study is conducted. Then a novel methodology is proposed that makes use of screw theory to analyze the deformation and stiffness of the mechanism: firstly we identified the existence of the deformation of the subchain, in terms of the relationship between the effective screw and deformation screw; then we took the deformation as an infinitesimal motion of the mechanism, and the stiffness matrix corresponding to the deformation can be deduced. Finally the global stiffness matrix of the whole mechanism is modeled by assembling different stiffness characters based on the presented methodology.

Abstract: A new class of 4-DOF Parallel Manipulator (PM) with five supporting subchains is synthesized based on enumeration method. Targeting at 4PUS-1PPU PM, the inverse kinematics and dexterity analysis are developed, and the geometric parameters are determined.

Abstract: To meet the high speed and high precision requirements of machining freeform workpieces, a 4-DOF parallel kinematic platform with the configuration of 4 actuated legs plus a passive leg is proposed in this paper. Inverse kinematics and the calibration algorithm are developed, and virtual prototype modeling and kinematic simulation using MSC/ADAMS are carried out. The simulation results exhibit that the proposed structure is capable of implementing the high-precision machining requirements of freeform parts.

Abstract: For reducing the machining difficulty and increasing the conjunction precision, an automatic sorting system is presented. The system combines the backpressure pneumatic measurement with a pneumatic-electric transfer technology. A semiconductor pressure sensor is used for the pneumatic-electric transfer. The air chamber pressure is converted to an electrical signal. The merits of the semiconductor pressure sensor include high conversion precision, high frequency response, and small volume. But it has a relatively big temperature drift if no compensation is provided. The sensor can compensate temperature drift. But the null shift and sensitivity shift still exist. Reducing supply voltage using an electric bridge or reducing supply current using a constant current source can reduce the shift. The null shift and sensitivity shift can be further reduced by auto-compensation using a calibrated gauge. The automatic sorting system can automatically sort injector valves and orifices quickly with a resolution of 0.2µm. The sorting accuracy is 0.5µm and the speed is approximately thirty pieces per minute. The system has the function of auto-control and error auto-compensation and has a high measuring efficiency and high precision.

Abstract: Magnetic tunnel junctions(MTJ) are fabricated as a function of the input power of Al thin film. Al thin films have pseudo-crystalline structure at 30, 60, 90 W and transform into amorphous like smooth nanocrystalline state at 120 W. Junction resistance increases as the annealing temperature increases up to 250 􀀀 and decrease at 300 􀀀 at the pseudo-crystalline barrier. When the barrier has amorphous like nanocrystalline structure, optimum annealing temperature increases up to 300 􀀀 . The barrier characteristics are strongly related with the microstructure of AlOx barrier.