Abstract:A simulation model of turbocharged gasoline engine with electronically controlled waste valve system was built with the software of GT power. Based on the condition of boost pressure changing with the waste valve opening, characteristic values of the control system were obtained. According to the change rules of exhaust back pressure under different boost pressures, the waste valve opening was calibrated on the basis of the requirements of power performance of the engine, the matching performance between the turbocharger and the gasoline engine was analyzed, and then, test verification was conducted.The results have shown that matching a small diameter turbine can ensure the engine performance at low speed condition; the electronically controlled system can realize the continuous control of boost pressure target value; and the problems of deflagration and turbocharger super speed caused by too high boost pressures can be resolved at high speed conditions.

Abstract:Spray simulation using Lagrangian Droplet and Eulerian Fluid (LDEF) method and the Discrete Droplet Model (DDM) has been proved to be of grid dependency. The grid effects on the spray simulation of an asymmetric three hole nozzle were studied. First, the sources of grid dependency were analyzed. The effects of grid types and different grid sizes of radial, azimuthal and axial directions on the spray process were investigated by comparing the spray shape and liquid penetration distance with experiment data. And the grid effect on the Sauter Mean Diameter (SMD) was studied. Finally, the aspect ratio between the radial and the axial directions of the grid was optimized. The result has shown that, for the asymmetric three hole nozzle spray simulation, the polar mesh has better performance among the different mesh forms. With the decrease of the grid size on three directions, the spray tip penetration and SMD basically present the tendency of increase, while the radial grid size shows greater influence than the axial size. The spray tip penetration fits best with experimental data when the grid size and the aspect ratio are optimized.

Abstract:In order to ensure the reliability of the accelerator pedal signal, non contact Hall sensor was adopted as an electronic accelerator pedal position sensor. In order to ensure the acceleration pedal signal reliability with a non contact Hall sensor as the electronic accelerator pedal position sensor and the pedal position sensor signal, an improved first order low pass filtering algorithm was proposed and combined with the motor driving characteristics of the accelerator pedal position sensor signal fault diagnosis. Through the establishment of the pedal signal control simulation model, the reliability of the whole control process was tested. The results have shown that pedal signal glitches, too high, too low or synchronous error can accurately identify various fault conditions. This control method can meet the reliability control requirements of pure electric automobile electronic acceleration pedal.

Abstract:An analytic method of demand torque was designed for a plug in hybrid electric vehicle equipped with continuously variable transmission (CVT), which is based on the external characteristic curve of the power source and the signal from the driver's operation. Then, energy management strategy minimizing instantaneous economic cost under drive and brake condition was proposed, with the demand torque, vehicle speed and state of charge (SOC) of battery as the state variables, and the throttle opening of the engine, motor torque and speed ratio of CVT as the control variables. Further research was carried out on the influence of whether the engine driving alone is allowed at the charge depleting stage on economic cost. Through simulation with self built forward model, the results have shown that the strategy that does not allow engine driving alone at the charge depleting stage is better in comprehensive economy.

Abstract:Due to the impact of the elastic deformation of tools and press, and the blank thinning and other factors, the die surface gap is not consistent with the thickness distribution of the stamped part, which leads to low spot rate. With regard to the problem mentioned above, a new mesh mapping algorithm based on binary search was presented, which can realize the accurate mapping between different meshes，and then, a new methodological scheme was developed for the compensation of the die surfaces. In the early design stage, the new methodology can guide the engineer to modify the die surface, thus offsetting the influence on quality caused by the deformation of tools. Application example has shown that the new mapping algorithm not only improves the accuracy but also improves the search speed. The methodology can solve the problem of low spot rate and noticeably improve the first time contacting ratio.

Abstract:In order to solve bad roll stability problem of partially filled tanker in the process of steering, the liquid sloshing equivalent mechanical model and the partially filled tanker vehicle motion model were developed. Two models were coupled by dynamics of solid fluid interaction. Five different size proportions of elliptical tankers cross section were selected to simulate, it is concluded that the tanker has better roll stability because it has minimum sloshing force and moment, when long axis (2a) and short axis (2b) of the elliptical is the ratio of 1.5. The results provide technical support for the tanker’s driving roll stability research and vehicle design.

Abstract:The aim of the present study was to develop and validate an FE model of neck muscle system according to human anatomy structure in order to analyze the influence of neck muscle activation on head neck dynamic responses and biomechanical responses under rear impact loading condition. A three dimensional neck muscle model was developed on the basis of the MRI data of a 50th percentile male. The model was then combined with a previously developed and well validated head neck FE model in Kriging method. The passive and active behavior of a single neck muscle was defined by coupling Ogden and Hill material models. The neck muscle FE model was validated through volunteer tests of rear impact conducted in Chalmers University of Technology. The result has shown that, compared with non activation muscle behavior, the displacement of head CDG to T1 decreases by 12mm while the angle displacement decreases by 4°, which indicates the significant effect of muscle activation on head kinetic responses. The head neck dynamic responses from the simulations are consistent with the test results. The current neck muscle FE model is of a good biofidelity and can further be used for occupant neck biomechanical research in rear impact loading conditions.

Abstract:The technique of the load identification of mass variable system was studied. The generalized modal concept applied on time varying system was introduced, and the method of modal superposition was used to give dynamic equations with partially decoupled in initial modal space defined at initial instant. Based on both virtual distortion method (VDM) accounting for the effect of mass change and the Duhamel integration in initial modal space, two approaches to identify modal forces were constructed: one is the recursive calculation pattern formulated on the basis of modal acceleration, and the other is the regularized solution by the direct discretization of Duhamel integration with modal displacement and acceleration. A mass variable system with 16 degrees of freedom subjected to two external loads was analyzed. The responses were calculated by applying Euler midpoint symplectic difference method and added with random noise to simulate measured signals. Two dynamic loads were identified by two inversion approaches of modal forces. The comparison of results has indicated that regularized solution format has a higher numerical robust than the recursive calculation pattern, but the latter is sensitive to the noise of measurement.

Abstract:The nonlinear pull in behavior of piezoelectric laminated micro beam was studied with consideration of the size effect and damage effect. Based on the theories of continuum mechanics and Euler Bernoulli beam hypothesis, the nonlinear governing equation of piezoelectric laminated micro beam with damage was established and solved in Galerkin method and Runge Kutta method. The influence of various parameters on the pull in voltage of the micro beam was discussed, and the results have shown that the geometry nonlinearity can improve the value of critical pull in voltage of the micro beam; the changes of governing voltage, micro beam length and other parameters have influences on the critical pull in voltage of the micro beam. Besides，the FEM software was used to carry out the check up calculations, and the results were compared with the theoretical results. The findings of this research can offer guidance to the design of micro structures.

Abstract:The background value coefficient α of the non equidistant GM (1, 1) model has great influence on the predictive capability, but it is difficult to determine its optimal value. For these problems, the bacterial foraging algorithm and a GM (1, 1) model were combined and the BFA GM (1, 1) optimization model was proposed. Taking the experiment of empennage fatigue life prediction as an example, the performances of the BFA GM (1, 1) model, the PSO GM (1, 1) model and the GA GM (1, 1) model were analyzed and compared. The results have shown that the BFA GM (1, 1) model consumes the least time and obtains the lowest average prediction error, and that the BFA GM (1, 1) model proposed is competent to find the optimal background value coefficient α quickly and accurately, thereby increasing the empennage fatigue life prediction accuracy under the conditions of “small samples” and “poor information”.

Abstract:The friction performance of water lubricated bearing depends on the lubricated conditions, hardness, dynamic viscoelasticity of rubber, and so forth. After the surface was modified with silane coupling agent KH 550, palygorskite (AT) nano powder was added to NBR rubber to prepare AT/NBR rubber liner vulcanizate sample and AT/NBR water lubricated bearing sample. Proved by testing results, the comprehensive mechanical properties and the hardness of AT/NBR rubber liner vulcanizate sample were enhanced. Detected by dynamic mechanical analyzer (DMA), the loss factor values at 0 ℃ of NBR and AT/NBR rubber liner vulcanizate samples were approximately the same, and the wet sliding properties almost remained unchanged. When tested with friction wear test machine of bearing, the water lubricated friction coefficient of AT/NBR bearing sample decreased. Those experiments have shown that the performance index of AT/NBR bearing sample is better than that of the NBR bearing sample and meets the requirements of MIL DTL 17901C (SH) specification.

Abstract:An algorithm for optimally allocating Permanent magnet biased Saturation based Fault Current Limiter (PMFCL) in large power grid was presented. The current limiting mechanism of PMFCLs was briefly introduced. Short circuit current margin was defined and can be used as the criteria of over standard bus selection. Bus self impedance was regarded as the measurement index of short circuit level. On account of the increment of bus self impedance, an optimal allocation evaluation function with consideration of the overall current limiting effect and economy was built. It is proposed that the starting condition of PMFCLs and the sensitivity index of bus self impedance with respect to the branch impedance can be utilized to greatly decrease the searching space. Finally, the algorithm for optimally allocating PMFCLs was concluded on the basis of evaluation function and sensitivity index. Simulation of IEEE 39 bus system was completed by using the proposed optimal allocation algorithm and genetic algorithm function of Matlab. The result suggests that the process of optimal allocation has relatively higher efficiency when compared with the method, in which sensitivity is not considered, the short current of over standard substations is restrained successfully and some abundant values are reserved. Furthermore, the effect of current limiting is better when the current exceeds the standard one more seriously. It verifies the feasibility and effectiveness of the proposed optimal allocation algorithm.

Abstract:In low voltage microgrid, traditional power droop control will cause active and reactive power coupling problem. Virtual power droop control based on coordinate transformation was adopted and its decoupling characteristics, power sharing and restriction problems were studied. Relative gain analysis method was used to analyze the power coupling degree after adopting coordinate transformation. It is theoretically proved that the virtual power droop control can realize total power decoupling characteristics when the coordinate transformation matrix and line impedance have the same resistance and inductance ratio. Aiming at the problem that line impedance difference can cause uneven power sharing, a strategy was proposed, which aimed to improve power sharing accuracy by adding virtual negative impedance. In the light of the limitation of the existing power restriction range of virtual power droop control which is not equal to the actual power restriction range of the inverter, a new power restriction control strategy was proposed. Eight sections were divided for the operation points, in which the power exceeds the limits. The section number was determined according to the inverter output power and the corresponding adjustment measures were taken. Simulation results have verified the correctness and effectiveness of the proposed control strategy.

Abstract:Through the establishment of multi flicker sources circuit equivalent model, the theoretical background of tracing flicker sources by flicker power was analyzed. To accurately estimate flicker power, the flicker envelope parameters were obtained by using improved Teager Kaiser energy operator and the improved FFT. The direction of flicker flow was determined by the sign of flicker power, and pollution assessment was achieved with the magnitude of flicker power. The simulation analysis and experiment results show that this approach can trace flicker sources effectively and rapidly and assess the pollution level of different flicker sources accurately. The tracing results are computed fast and correctly and the misdiagnosis rate is reduced.

Abstract:The realization of SVPWM rapidly is a key issue in expanding the application of multilevel converter. To solve this problem, different multilevel SVPWM algorithms based on different coordinates were studied. But there was no comparison analysis report on the speed of these algorithms. For this purpose, a rapidity analysis of 4 typical multilevel SVPWM algorithms in different coordinates was researched. Theoretical analysis and experiment results have shown that the multilevel SVPWM algorithm in 45° coordinate has fewer calculations and is suitable for optimal control. So the multilevel SVPWM in 45°coordinate is recommended.

Abstract:As the key module of fractional N PLL(Phase Locked Loop), the Sigma Delta modulator can significantly improve the performance of the fractional N PLL by the way of noise shaping. However, when it comes to the three most important specifications: the output sequence cycle, the range and the error, the now existing modulators cannot improve them at the same time. As a contrast, the proposed novel Sigma Delta modulator ameliorates the aforementioned three specifications simultaneously by adding a feed forward between two adjacent stages and adjusting the modulus of adders to prime number. Regardless of the input value and initial conditions, the presented modulator guarantees a sequence length of M3, which is almost M2/2 times of that in traditional modulator, where M is the largest prime number smaller than 2n0, and n0 is the bit width of adders. The simulation results show that, compared with the existing modulators, the proposed modulator can effectively remove the spur in the output spectrum and make it more close to the ideal Sigma Delta modulator.

Abstract:To solve the problem of fewer beacon nodes and unknown transmission time in Time of Arrival (ToA) based localization, a new linear programming algorithm was proposed to approximate nonlinear localization estimation problems. We consider the least mean absolute errors of the residual and formulate the nonconvex localization problem as a simple linear programming by using linear approximation. Simulation results demonstrate that the proposed algorithm can maintain good positioning accuracy under fewer beacon nodes and achieve better performance by using less node resources than the existing algorithms.

Abstract:The effective microseismic signals are disturbed by noises, so the precision of time delay estimation is affected. Because time delay estimation is the key to determine location accuracy, one dimensional slice method based on third order cumulants was proposed for microseismic signal time delay estimation. Firstly, the three order self accumulation and mutual accumulation of the signals were calculated, then, one dimensional slice was obtained in order to reduce the computation and to satisfy the field real time requirements. Finally, the time delay value was obtained by the criterion function. Compared with the traditional cross correlation method, this method has less sensitivity to the Gauss noise with unknown correlation and has stronger inhibition ability to the correlated Gauss noise. The simulation results show that the detection probability and root mean square error are better than the traditional method under the influence of Gauss random noise and correlated noise with SNR=-5 dB to SNR=15 dB. In the implementation of real data, the real microseismic noise probability statistic characteristics were analyzed and the data in the well were selected as references, and then the time delay value to the ground data was calculated on the basis of the surface and borehole observation. The validity and the practicability of this method were verified.

Abstract:Block based copy move image forgery detection methods usually have problems such as high dimensional feature vector, high computational complexity and low detection rate.So, this paper proposed a new method for image copy move forgery detection based on color invariants, which extracts density characteristics from each channel of opponent color space converted from RGB. The k d tree is constructed to speed up approximate nearest neighbors matching for tampering detection. The experiment results show that the proposed local color invariants feature with low dimension and simple computation can represent the image block feature effectively. When compared with typical block based methods, this method has some advantages, such as lower computational complexity, more accurate and robust to post processing for forgery regions such as rotation and scaling.

Abstract:As the direction of edges in images is not taken into account, the original geometric nonlinear diffusion filter (GNLDF) is not in the best state for images denoising, which diffuses only in the horizontal and vertical directions. In this study, we detected the edges and their directions in images based on the magnitude of the gradient in the direction of the eight neighborhoods of each pixel, then conducted GNLDF at the edge pixel just along the directions of the edges while at any no edge pixel along all four directions. Experiment results of five typical images with five levels of noise intensity show that the proposed method can not only effectively remove the noise but also better protect the edges in images.

Abstract:This paper borrowed the idea of molecular diffusion and proposed a proactive caching scheme based on content diffusion. In this mechanism, the conception of content concentration was introduced to analyze user demands for different contents in different network regions. In order to achieve fast content placement and increase the probability of providing responses to user requests by the nearer caching nodes, the content replicas were proactively pushed forward or migrated according to the content concentration difference between nodes. Furthermore, by synthetically considering the content popularity, a probabilistic content placement method was also implemented. The simulation results have shown that this scheme can effectively decrease the average access cost and improve the cache hit ratio.

Abstract:This paper presented an improved scheduling algorithm for dynamic heterogeneous chip multicore processors(Heterogeneous Scheduling Genetic Algorithm,HSGA ).The proposed scheduling algorithm uses time slices of OS scheduler to complete the iterative procedure of HSGA, which can obtain efficient task scheduling results and choose the best process core for each application task. The experiments using SESC simulator show that the ED2s of the proposed algorithm are only 0.4%, 1.1% and 1.3% higher than those of a baseline classic Hungarian Algorithm with 4 cores, 8 cores and 16 cores chip multiprocessor respectively with random degradation. And the proposed algorithm can generate more stable and adaptive results for unpredictable heterogeneity, compared with Hungarian Algorithm and Local Search Algorithm.