Abstract:In order to optimize the performance of engine bleeding brake, a three-dimensional model was built with UG. The model was divided into grid by the dynamic mesh technique. Besides, the motion rule of the intake valve and piston was set and defined. By applying the three-dimensional transient numerical simulation in the process of engine brake working by Fluent, the changes of pition pressure were analyzed. According to the piston's instantaneous force, the engine average braking power in different conditions was calculated, and then the influence of exhaust valve lash, engine speed and exhaust back pressure on engine braking performance was also obtained. By optimizing working parameters, the performance of engine bleeding brake was enhanced, and the simulation results were verified with experiments. The results have shown that the maximum error is 5.2%, and the smallest error is only 4.1%. It is shown that the simulation results are of high precision and accuracy.

Abstract:A simple peak junction working temperature predicting model on the pulse width modulation working condition was established in order to accurately estimate the temperature rise of power MOSFET within engine controller. The model can make an accurate prediction of the peak junction temperature under pulse width modulation operation based on the components DATASHEET parameter. The measured temperature-rise results with experiments were provided to verify the model prediction accuracy. The prediction results match the experiment results very well and the maximum error is less than 2.3%. Although temperature prediction is based on the solenoid valve drive circuit, the analysis results can be easily extended to other power device drive circuitry topology.

Abstract:In order to study the active control methods to improve the crosswind stability of high-speed vehicle, we established the eight degrees of freedom nonlinear vehicle dynamic model under crosswind, and two degrees of freedom model based on piecewise linear tire features as the reference model. We designed an Active Front Steering (AFS) controller based on flexible PID control and a Direct Yaw moment Control (DYC) controller based on LQR Optimal control. Comparative analysis of the two kinds of typical operating conditions in two different active control methods for high-speed vehicle crosswind stability control was conducted. The results show that, on driving straight crosswind conditions, DYC on performances of maneuverability, stability, ability to keep track is superior to AFS, but AFS is superior to DYC in longitudinal dynamic; on crosswind front corner condition, AFS and DYC have little difference in the performance of maneuverability, stability and ability to keep track, but AFS is significantly better than DYC.

Abstract:A suspension roll mechanic model was set up, and by using the initial parameter method of structural mechanics, the analytical solution of the torsional stiffness of torsion beam with stabilizer bar was deduced, on the basis of which the mathematical model of its equivalent roll stiffness at the wheels was established. The mathematical model was verified by simulating the corresponding model set up with ABAQUS software. Then, combined with NSGA-Ⅱ algorithm, an optimization was conducted on the roll stiffness and the total quality of the beam. The results have shown that the roll stiffness and total quality of the beam get a good balance and the optimization method is reliable, which has theoretical guidance for the design and choice of characteristic parameters of the torsion beam rear axle in the primary stage of development.

Abstract:To solve the problem of the low precision of collision detection in the turn-mill combined machining simulation, a rapid collision detection algorithm based on the improved theory of Oriented Bounding Box was proposed. This algorithm, based on the improved oriented bounding box, and using the collision detection result as the input, creates the oriented bounding box and hierarchical bounding box tree of the collision unit group. During the rough detection phase, the intersecting nodes are detected. In the following precise detection phase, the triangular patches of the objects in collision are detected. With the application of feedback technology, the initial time and position of the collision are calculated. A case study shows that this algorithm increases the efficiency and precision of the collision detection in numerical control simulation.

Abstract:This paper proposed a new high-dimension model representation (HDMR) based on back propagation neural network (BPNN), which is called BPNN-HDMR. The most remarkable advantage of this method lies in its ability to integrate the nonlinear function approximation capability of BP neural network and the hierarchy structure theory of high dimensional model to build an approximation model. Moreover, this method can reveal the inherent linearity or nonlinearity relationship as well as correlation with respect to input variables. The problem of modeling high dimension model is effectively tackled by reducing the computation cost from exponential growing to polynomial. Testing and comparative analysis confirm the efficiency and capability of BPNN-HDMR for high dimension nonlinear problems. Furthermore, the algorithm was applied to optimize the ROPS of Mining Dump Truck's Safety Cab. The optimized results verify the feasibility and effectiveness of the method proposed.

Abstract:At high speed, the calculated result has deviation compared with that of practical situation if the smaller stiffness parts are regarded as pure rigid body. Based on rigid-flexible coupling dynamic theory, a dynamic model of pusher device system with rigid-flexible coupling of a packaging machine was built in the finite element method and modal superposition method, and the smaller stiffness parts were softened. The dynamic stress of the pushing hands during pushing and folding procedures were calculated according to the above model. The validity of this method was verified by comparing the results with the conclusion in ABAQUS. A comparative study of the pusher device's multi-rigid-body calculation model and rigid-flexible coupling dynamics model has shown that the distortion of flexible pushing hands causes positional deviation, which verifies that the calculation result of the rigid-flexible coupling dynamics model is more accurate at high speed.

Abstract:To simplify the mathematical model for the "S" edge curves of a ball end mill and derive the composite edge curve equations of the intersection of two space planes and the sphere，this paper proposed and applied the "Single Sphere Method" and "Dual Spheres Method" to deduce the mathematical expressions of the deflection angle and helical angle of the flat edge curves on a ball end mill's spherical part. The results have shown that the mathematical relationship between the deflection angle and the helical angle is equal, thus simplifying the mathematical model of the plane edge curves on the spherical part with an equal relationship between the two angles. This reduces the complexity of the derivation process of the plane edge curves and provides an effective method for the composite edge curves' modeling of the intersections of two or more space planes and the spherical part of the ball end mill.

Abstract:To achieve optimization rapidly and automatically in the process of product development, an integrated optimization system platform was established by modeling with the implicit parametric software SFE CONCEPT, and integrating SFE CONCEPT, the solver LS-DYNA, and the data processor Matlab with the multidisciplinary design optimization software iSIGHT. For an example, the lightweight optimization of the shape in space, the section, and the thickness of the front bumper beam was carried out with the premise of ensuring the safety of collision. With minimizing the mass of beam as the objective , the compressed displacement and the peak of acceleration as the constrains, the optimization under three low-speed crash simulation analysis, 40% offset barrier, rigid wall and the rigid pillar, was conducted in optimal Latin hypercube design and adaptive simulated annealing method, and the result was satisfactory.

Abstract:This paper presented a multi-domain boundary face method (MD-BFM) to solve steady-state heat conduction problems in large-scale engineering structures. Based on BFM, and using a similar approach as that in single-domain problems, this paper derived the matrix assembly process in multi-domain problems. Then, temperature and other unknown quantities can be drawn from the discrete boundary integral equation. The multi-domain BFM was developed and applied to the steady state heat conduction analysis of an actual gravity dam, which contained 62 concrete layers (totally 125 domains). In order to verify the result, the temperature contours of the dam were compared with the result obtained from FEM (using Abaqus). The comparison chart has shown that the maximum temperature value of both results is 20.7 ℃. Moreover, the contours are highly consistent. Numerical results have demonstrated that our method can achieve comparable accuracy than other methods (e.g. the FEM) at much lower cost in terms of both computer resources and human labor.

Abstract:This paper presented a new method to suppress vortex-induced vibration by controlling the phase of fluctuation aerodynamic loads with synthetic jet. In order to verify the phase control function of synthetic jet and study the parameters range in which the phase control can be implemented, the two-dimensional unsteady flow around E214 airfoil was simulated numerically with CFD software. The time history of lift coefficient was obtained. The fast Fourier transform (FFT) was performed to get the fundamental frequency of fluctuation aerodynamic loads under large attack angle without synthetic jet control. The method to judge whether the synthetic jet can control the phase of fluctuation aerodynamic loads was obtained. Based on the data of a series of numerical simulation, the velocity- frequency ranges in which the synthetic jet can control the phase of fluctuation aerodynamic loads were obtained. The results have shown that the velocity and frequency of the synthetic jet can influence the phase control function of the synthetic jet significantly. When the frequency of the synthetic jet is close to the frequency of fluctuation aerodynamic loads without synthetic jet control, the synthetic jet can achieve phase control with lower control energy. On the contrary, much control energy is needed.

Abstract:In the permanent magnet brushless DC motor (BLDCM) control system, a new ADRC brushless DC motor control system was propsed in order to enhance the robustness and adaptability of the control system and to simplify the controller structure and the debugging process. In motor control, auto disturbance rejection controller (ADRC) is the effective means to improve the robustness of a system, but it has a lot of parameters to be adjusted, which is not good for practical application. This paper used fuzzy control technology to facilitate ADRC parameter self-tuning. This method not only maintains the original excellent performance of ADRC, but also improves the adaptive capacity. Combined with the characteristics of brushless DC motor itself, this paper deduced the second-order equation of BLDCM by using only one parameter fuzzy self-tuning ADRC to achieve a brushless DC motor operation control system. Simulation results have shown that this control system has strong adaptability and robustness in the condition of BLDCM internal parameter perturbation and external disturbances. Experiment results have also shown the feasibility and effectiveness of this system.

Abstract:To overcome the shortcomings of the conventional SVM for diode clamped multilevel inverter, a classification algorithm based on Kohonen's competitive NN was propsed. Although the algorithm is an NN-based one, it does not need a training stage. The proposed SVM switching strategy eliminates the time consuming operations, so the whole procedure for the implementation of the algorithm is carried out with simple mathematical operations. The validity of mathematical analysis and the feasibility of the proposed algorithm were verified with simulation studies for both a three-level DCI and a five-level DCI. The simulation studies also verify that the proposed algorithm is a generalized one for an n-level DCI and does not need any modification when the number of levels increases.

Abstract:The variable weights analysis method was used to evaluate the charging equipment performance. A comprehensive evaluation index system for EV charging equipment performance was established. And the method for indexes to get evaluated value and to be quantified uniformly was discussed, which was followed by principle and procedure of weight calculation by using variable weight analysis method. Finally, a software was designed to analyze and evaluate the test data, and the software was used to analyze the test data of two chargers, and then, the final result was obtained by using variable weight analysis method. The analysis results have shown that variable weight analysis method can be used efficiently to evaluate EV charging equipment performance, and the results highlight the role of the weak part, making the evaluation more reasonable. This method can not only be applied to the evaluation of EV charging equipment performance, but also to the comprehensive evaluation of other complex systems.

Abstract:Load forecasting is one of the basic issues of the electric power industry. However, because load has a certain social attributes, the improvement of the accuracy of load forecasting result is a difficult issue. This paper first used k-means cluster method to find similar data from historical date and weather data, and then used support vector machine (SVM) for forecasting. Seen from the result, the proposed method's MAPE is 0.88%, but BP-ANN and ARMA are 1.66% and 3.81% respectively. It is proved that this method has a high accuracy.

Abstract:In order to decrease the measurement error of the traditional dual-energy γ-ray method and reduce the impact of the ash component on detection accuracy in ash determination, a new coal ash measurement model based on fuzzy neural network and the dual-energy γ-ray was established, and then the model was applied on online testing of coal ash content. The application of the traditional and new coal ash measurement model was analyzed by online testing, and the measurement results of both were comparatively analyzed. The results show that the relative error of ash content using the new method was less than 1%, while the average relative error of the traditional measurement was about 3%, and the measurement accuracy of the new method is not affected by the ash component. Meanwhile, the relationship between the chemical composition of coal ash and ash content was analyzed by using X-ray fluorescence spectrometry (XRF), and the results indicate that the content of Fe, Ca, Mg and S elements in coal can affect the detection accuracy of traditional dual-energy γ-ray dialysis, the greater fluctuations of their ingredient content result in greater measurement error.

Abstract:Query suggestion is an interactive approach for search engines to better understand user information need. A Term-Query bipartite graph was trained by extracting semantic relationships from snippet clicked by query. With the combination of Query-URL graph and Query-Flow graph, a heterogeneous Term-Query-URL information network was constructed. Random walk with restart (RWR) was performed on the information network for query suggestion. The relevance of long tail query suggestion was greatly improved by taking into account semantic information and log information. Term vector of query was constructed on the basis of probabilistic language model for query suggestion of new query. The experiment results have shown that our approach outperforms baseline methods by about 3% to 10%.

Abstract:In high-speed integrated power units, vibration signal coupling is very serious, which makes it difficult to determine the number of vibration sources by using traditional methods. In order to cope with this problem, this paper proposed an improved blind source signal processing method. Based on the traditional blind source separation method, this method used prior knowledge of failure mechanism to enhance the effect of blind source separation. Experiment results show that signal after separation fits well with fault characteristics. This method is very effective in the fault diagnosis of integrated power unit and it can improve the accuracy of fault diagnosis.

Abstract:Most current modeling systems do not guarantee the 2-manifold structures and may generate non-manifold structures. In this paper, a new vertex-based representation for mesh structures was proposed, and a formal proof was given to show that this representation characterizes precisely 2-manifold structures. It has been shown that the new proposed mesh modeling operations are more intuitive, more efficient, and more user-friendly, compared with previously proposed methods in related literatures.