Papers by Author: Yu Hou Wu

Abstract: The quality of high-speed machining workpiece is determined by drive control performance of motorized spindle. Vector control is one of high-speed motorized spindle control method, but the traditional controller is difficult to effectively overcome parameter disturbances caused by parameter variations from internal and external system. So it is necessary to use intelligent control. In this paper, a model of a speed and flux-closed-loop vector control system with an inner torque-closed loop is established, and a fuzzy controller is used to adjust the speed. MATLAB is used for load simulation of high-speed segment of motorized spindle, and then the simulation results show that high-speed motorized spindle can be increased in to the high-speed segment using a short period of time, and it has strong anti-interference ability and excellent performance at the same time in the control system presented in this paper.

Abstract: Use special-shaped stone turn-milling machining center (HTM50200) to achieve the production of complex relief. Through the ArtCAM establish the three dimensional relief model of Riverside Scene at Qingming Festival. Analysis of blank material characteristics and features of NC machining center, select the appropriate tool, calculate cutting depth 、cutting speed 、feed rate 、spindle speed and other process parameters by formulas. With ArtCAM/CAM module to make process of the preparation of the rough finishing, the semi-finishing and finishing, and then generate the tool path file. Simulation in VERICUT can optimize the potential collision, over-cutting and owe cut of the machining process, and the adoption of special-shaped stone machining center for milling to finalize production of the relief, summarize the experience in special-shaped stone processing.

Abstract: In order to verify the processability of a special-shaped stone machining center’s horizontal working portion, to process complex stone products. On the basis of analysis of the physical characteristics of diamond cutting tool and stone, create a model and use UG software to program, making this machine center’s dedicated post processor. Simulate NC code that is generated with VERICUT software, optimize the cutting parameters and analyse its surface quality. Avoid interference in the program, gouge, collisions and other phenomena by adjusting the tool axis’s attitude and the tool paths. Actual process verified the reliability of the program, technological parameter is rational, quality of the parts’ surface is well. Make precisely outline and tool wear is small, overcome the drawbacks of CNC system, get a higher efficiency.

Abstract: PEM fuel cell is the most promising application as an automotive power. Proton transfer in PEM is one of important factors to understand the performance of PEM fuel cell. In this paper, the proton transfer mechanisms are analyzed by the molecular simulation based on the basic principle of molecular dynamics. Effects of water content in the proton exchange membrane and cell temperature on the proton transfer in the membrane are studied by the radial distribution function (RDF). Results show that proton transfers in the Nafion polymer by water bridges between two sulfonic groups of adjacent side chains. There are more water bridges supporting proton transfer with the increase of water content in membrane. The increase of cell temperature speeds up the form and break of O-H bond, which promotes the proton transfer. The research results are very helpful to understanding the proton transfer mechanism in proton exchange membrane and promoting the applications of PEM fuel cell.

Abstract: Along with building decoration industry and stone industry development, special-shaped stone equipments develop to high speed and efficiency, intelligent, compound function directions. Special-shaped stone multi-function compound machining center was designed, realized stone turning function and carving and milling function compound in a perpendicular saddle, analyzed machining center motion function. Kinetic simulation research on machining center was performed using COSMOSMotion, tracked spindle tool output displacement, speed and acceleration data by trajectory tracking, indicated mathematic model correct. Structure design was optimized through analysis of crossbeam and bed. This had important practical value to dynamic design of NC equipment and prototype research.

Abstract: Cathode catalyst layer plays an important role in PEMFC. Electrochemical reaction in cathode catalyst layer is a control process for the performance in PEMFC. In this paper, oxygen reduction reaction (ORR) is studied by molecular simulations based on a series pathway which consist of four steps. We calculated the free energy of four steps respectively by molecular simulations. Comparing free energy of our steps, we found that the fourth step can release more energy than the other steps. At the same time, we found that the energy released in ORR is decreased with the increase of temperature. The process of the first step in the series pathway release less energy than that of other steps. The results are very helpful for optimization of construction in the cathode and improving performance of PEM fuel cell.

Abstract: A two-phase flow, multi-component model has been optimized for a PEM (Proton Exchange Membrane) Fuel Cell. The modeling domain consists of the membrane, two catalyst layers, two diffusion layers, and two channels. Both liquid and gas phases are considered in the entire cathode and anode, including the channel, the diffusion layer and the catalyst layer. The Gravity effect on liquid water was considered in channels. Typical two-phase flow distributions in the cathode gas channel, gas diffuser and catalyst layer are presented. Source term and porosity term were optimized. Based on the simulation results, it is found that two-phase flow characteristics in the cathode depend on the current density, operating temperature, and cathode and anode humidification temperatures. Water mass fraction for the fuel cell with anode upward is higher than that the case with cathode-upward. Liquid water with the case of cathode-upward blocks pores in the gas diffuser layer leading to increasing the concentration polarization. Gravity of liquid water exerts the effect on the water mass fraction in the cathode.

Abstract: A molecular dynamics model was performed to study the proton transport of Nafion series membrane which is often used in low temperature fuel cells. The simulations intents to investigate the microstructure and the phenomenon of the proton transport processing. The model includes all-atom of main and side chains. The force field includes intermolecular Coulomb and Lennard-Jones terms and intra-molecular terms for harmonic bond stretch potentials, harmonic angle bend potentials and cosine terms for the torsions. The simulations were carried out in two cube systems at different temperature where water content differed from 5 and 10 water molecules per acid group in the polymer, respectively. The results showed that proton transport affected with water content by analyses of snap- shots of the MD simulation, the radial distribution functions between the sulfur atoms of SO3− groups, between the oxygen atoms of H3O+ ions, between oxygen atoms of water molecules and Nafion atoms at various stages.

Abstract: With the increase of the quantity demanded, stone products with high quality, really artsy and diversification become more and more best-selling. The special-shaped stone machining equipments with numerical control, single machine intelligent, high speed, high efficiency and multi-function combination must be manufactured to produce these stone products. In this paper, 3D design and project optimization for special-shaped stone composite machining center are carried by Solid Works and innovative design. Model analysis of the crossbeam in this machining center is carried by ANSYS and the maximum deformation value in the crossbeam is found. The crossbeam structure is optimized by comparison and analysis. The design and manufacture of special-shaped stone combined machining center is very helpful for development of manufacturing.

Abstract: Full face rock tunnel boring machine (TBM) plays an important role in boring rock of tunnel. The failure of disc cutter is the main reason leading to low efficiency of TBM. In this paper, analysis of force and motion for disc cutter are carried by using ABAQUS to study stress distribution and concentration in disc cutter and rocks. Influence of different rocks on stress in disc cutter is analyzed. By combination the failure modes of disc cutter and its stress distribution, methods of decreasing failures of disc cutter are presented. Wear resistance and service life of disc cutter are improved by matching the materials of disc cutters with rocks. The results are useful for structural optimization and strengthening treatment of material of disc cutter.