Xie Q.,Shanghai JiaoTong University |
Li Y.,Southwest University |
Chen X.,Shanghai JiaoTong University |
Hu J.,Northwest Institute of Mechanical and Electrical Engineering |
And 2 more authors.
Journal of Power Sources | Year: 2015
The phosphosilicate sol/sulfonated poly(ether ether ketone) (SPEEK) composite membranes are fabricated by using a simple mechanical mixing process. The performance of the composite membranes is investigated, including their morphology, thermal and mechanical properties, water adsorption and swelling ratio, proton conductivity and fuel cell performance. The composite membranes obtain the advantages of both components while avert their disadvantages, showing excellent comprehensive performance. The utilization of SPEEK endows the composite membranes with good mechanical properties even if the proportion of inorganic components in the membranes is as high as 40 wt.%. The incorporation of phosphosilicate sol not only enhances the dimensional and thermal stability of the composite membranes, but also improves their conductivity significantly. A maximum of proton conductivity of 0.138 S cm-1, higher than that of Nafion 212 membrane (0.124 S cm-1), is obtained from the composite membrane 6SPEEK/4(P-Si) under the conditions of 70 °C and 95% relative humidity, owing to its enhanced hygroscopicity and functional groups. Besides, a single fuel cell equipped with the composite membrane 7SPEEK/3(P-Si) releases a peak power density of 449.9 mW cm-2 at 60°C, higher than that of cells equipped with SPEEK and Nafion 212 membrane measured under the same conditions. © 2015 Elsevier B.V.
Liang T.,Xidian University |
Liang T.,Northwest Institute of Mechanical and Electrical Engineering |
Chen J.,Xidian University |
Zhao H.,Hengyang Normal University
International Journal of Systems Science | Year: 2013
In this article, by using the fractional order PIλ controller, we propose a simple and effective method to compute the robust stability region for the fractional order linear time-invariant plant with interval type uncertainties in both fractional orders and relevant coefficients. The presented method is based on decomposing the fractional order interval plant into several vertex plants using the lower and upper bounds of the fractional orders and relevant coefficients and then constructing the characteristic quasi-polynomial of each vertex plant, in which the value set of vertex characteristic quasi-polynomial in the complex plane is a polygon. The D-decomposition method is used to characterise the stability boundaries of each vertex characteristic quasi-polynomial in the space of controller parameters, which can obtain the stability region by varying λ orders in the range (0, 2). These regions of each vertex plant are computed by using three stability boundaries: real root boundary (RRB), complex root boundary (CRB) and infinite root boundary (IRB). The method gives the explicit formulae corresponding to these boundaries in terms of fractional order PIλ controller parameters. Thus, the robust stability region for fractional order interval plant can be obtained by intersecting stability region of each vertex plant. The robustness of stability region is tested by the value set approach and zero exclusion principle. Our presented technique does not require sweeping over the parameters and also does not need linear programming to solve a set of inequalities. It also offers several advantages over existing results obtained in this direction. The method in this article is useful for analysing and designing the fractional order PIλ controller for the fractional order interval plant. An example is given to illustrate this method. © 2013 Taylor & Francis Group, LLC.
Yunhua G.,Wuhan University of Technology |
Deqian S.,Northwest Institute of Mechanical and Electrical Engineering
Applied Mechanics and Materials | Year: 2012
A generalized assignment problem under the special constraints is proposed, which can be solved by the ant colony algorithm (ACA). But the ACA for the problem is easy to fall in local optima because the constraints are relatively complicated. In this paper, the diversity in the results is maintained and the convergent speed is elevated by an adaptive method of updating pheromone and a mutation strategy for clearing up invalid assignment. The computer experiments demonstrate that the optimization performance is improved by the proposed algorithm, which is more suitable for the real-time application. © (2012) Trans Tech Publications, Switzerland.
Su Y.-W.,Northwest Institute of Mechanical and Electrical Engineering |
Chen W.,Xi'an Jiaotong University |
Guo C.-X.,Northwest Institute of Mechanical and Electrical Engineering
Mocaxue Xuebao/Tribology | Year: 2012
Wear of clearance revolute joints is commonly coupled with mechanical dynamics. Winkler surface model is utilized to calculate joints reaction and contact pressure rather than Hertz model and finite element method (FEM) because Hertz model is not suitable for conformal contact. And FEM leads to the high computational cost. An analysis scheme of wear coupling with mechanical dynamics is established and validated by an exemplary crank slider mechanism with one clearance joint. Results show that wear prediction based Winkler's model can provide an acceptable accurate wear results compared with FEM although the later produces more accurate prediction. The proposed method is also an efficient tool for tribological design of mechanism with clearance joints.
Huang N.,Nanjing University of Science and Technology |
Ma J.,Northwest Institute of Mechanical and Electrical Engineering |
Wang Z.,Nanjing University of Science and Technology
Proceedings - 29th International Symposium on Ballistics, BALLISTICS 2016 | Year: 2016
Projectile shape coefficient, initial velocity and angle of fire determine the only trajectory of projectile for aeroballistics, so trajectory control can be realized exactly by changing these parameters. Cross-section interception technology has been proposed to carry out the saturation attack on group targets at long range. Applying the method of ballistics stim ulation, the large caliber can non weap on system's efficiency of saturation attack is analyzed. The efficiency is determined by two main factors, the total mass of projectors and the attacking efficiency of single projectile. Thus trajectory control can realize that projectiles fire in turn, arrive in the predicted cross-section at the same time to destroy the target completely. Compared with missiles and rocket weapon, high-muzzle-velocity super large caliber recoilless weapon system with simple guidance device and high energy explosive has longer range, tactical surprise. It can destroy group targets completely on the ground or surfaces ships.
Li F.-Y.,Northwestern Polytechnical University |
Zhang Y.-W.,Northwestern Polytechnical University |
Du X.-Z.,Northwest Institute of Mechanical and Electrical Engineering
Applied Mechanics and Materials | Year: 2013
In the experiment of cavitation, the same water tunnel with different model size will get cavity shape that is different from the result of the empirical formula under the same cavitation number. In this article, we studied the impact of wall effect on natural cavity shape and the resistance of cavitator. We get the cavity shape and resistance of cavitator under different diameter ratio. We also get the law how cavity shape and resistance of cavitator change with the diameter ratio. The results provide a reference for experiment in water tunnel and the simulation model. © (2013) Trans Tech Publications, Switzerland.
Han G.,Xianyang Normal University |
Li Y.,Northwest Institute of Mechanical and Electrical Engineering
Advanced Materials Research | Year: 2012
In an embedded system, a large amount of high real-time data processing is required. A TrueFFS method on the embedded VxWorks system is put forward to improve the data access speed and saving storage space of the embedded system. In this paper, the TrueFFS structure is analyzed, its establishing process is realized based on VxWorks. As an embedded operating system's main storage medium to build the TrueFFS, flash can improve system access speed and facilitate the upgrade of follow-up procedures.
Li C.,Northwest Institute of Mechanical and Electrical Engineering |
Chen M.,Northwest Institute of Mechanical and Electrical Engineering
Diangong Jishu Xuebao/Transactions of China Electrotechnical Society | Year: 2014
For those permanent magnet synchronous motors(PMSM) in which d-axis inductance is not equal to q-axis inductance, an optimum torque-angle compensation control method is presented on the basis of vector control coordinate transform. Expression of torque to compensation angle is obtained according to the PMSM electromagnetic torque equation in d-q axis. Characteristic of compensation angle to current when PMSM electromagnetic torque reaches its maximum value is derived via extremum principle. Simulation study is carried out to the optimum torque-angle compensation control and Id=0 control. The simulation results show that larger electromagnetic torque can be achieved when using the optimum torque-angle compensation control. The system has fast dynamic response. Last, experimental verification on DSP based PMSM control platform is implemented and the experimental results demonstrate the effectiveness and engineering realizability of the method proposed.
Li C.,Northwest Institute of Mechanical and Electrical Engineering |
Chen M.,Northwest Institute of Mechanical and Electrical Engineering |
Gao S.,Xi'an Technological University
Proceedings of the World Congress on Intelligent Control and Automation (WCICA) | Year: 2015
In this paper, a fractional order proportional and integral (FOPI or PIα) speed control method for permanent magnet synchronous motor (PMSM) is presented. Based on the modeling of current loop in PMSM vector control, the speed PIα controller is designed which fulfills specifications of the given phase margin and open loop gain crossover frequency. Numerical solution of phase crossover frequency is executed for each integral order by using Newton iteration method. The corresponding gain margin is achieved afterwards. Furthermore, the parameters of PIα controller are tuned by selecting the maximum gain margin of speed loop. The simulation results show that the speed step has small overshoot and fast response, which can verify the effectiveness of the proposed control strategy. © 2014 IEEE.
Gao Y.,Northwest Institute of Mechanical and Electrical Engineering |
Wang R.,Northwest Institute of Mechanical and Electrical Engineering |
Yuan J.,Northwest Institute of Mechanical and Electrical Engineering
Applied Mechanics and Materials | Year: 2013
Based on interest point detection, a feature preserving mesh simplification algorithm is proposed. The Harris operator values of all vertices in the mesh were computed firstly. On the base of Garland's simplification algorithm, we combine the Harris operator value with quadric error metric and change the order of edge collapsing in the simplification. The experimental results show that the proposed algorithm is effective and feature preserving. © (2013) Trans Tech Publications, Switzerland.