Abstract:Taking the battery module bus-bars of an electric vehicle as the research object, the 3D digital of bus-bar, working boundary conditions, connection relationships between bus-bar and battery cells were extracted. The influence rules of current size, convective heat transfer coefficient and pole welding process on the temperature of bus-bar were studied by numerical method of thermoelectric coupling. In order to ensure the accuracy of the numerical calculation, the dynamic battery pack test system was used to investigate the temperature variance of the specified working condition. The test condition was consistent with the boundary setting in the numerical calculation. The results show that the grid partition, boundary condition, current size, convective heat transfer coefficient and pole welding process have different effects on the temperature rise of the bus-bar. As the error between the numerical calculation and test result occurs in some working conditions, the reason was analyzed in detail. The correlation between the factors and the influence law of the error were also further studied, and then the numerical calculation model was modified. Finally, under the new working conditions, the numerical calculation and experimental measurements of bus-bar were carried out. Through using factor association and the influence rule on the error, the error between numerical calculation and experimental measurement was within 3.7%.

Abstract:The vibration characteristics of the bend pipe were studied by means of vibration power flow, as the problems of transmission efficiency reduction and structure damage for the hydraulic bend pipe of Hard Rock Tunnel Boring Machine (TBM) occur under the environment of strong vibration. Firstly, the calculation model of the elbow vibration power flow was established by the relationship between stress and power. Then, the influence rules of different basic vibration parameters and the elbow structure parameters on the stress were investigated through simulation, and the calculation method of total power and vibration power flow was given. Finally, the structure parameters of pipeline were optimized to reduce the vibration power flow of pipeline by 30.52%, and the design process of bend pipeline was proposed. The results show that the analytical method can provide the theoretical basis for the design and selection of the bend pipe.

Abstract:As a key component of a torsion beam, the transverse beam has an important influence on the modal frequency of the torsion beam. In order to explore the mechanism of the modal frequency under large deformation of the beam structure in essence, this study provided the design reference for the torsion beam structure in the conceptual design stage and carried out the analysis on the influence of the parameters of the torsion beam cross beam on the modal frequency. The torsion beam model was abstracted as a simplified model with qualitative characteristics, and the corresponding finite element model was established by Hypermesh. The main parameters of the transverse beam such as beam horizontal position, opening direction and opening angle were selected as the research objects. The parameters of the beam structure were changed by using the Hypormorph mesh deformation and model reconstruction. The influence of the parameters on the torsion and vertical bending modal frequencies of the torsion beam was analyzed, and then the characteristic curves of the above cross beam parameters and the related modal frequencies were obtained. The analysis results indicated that the modal frequencies of the torsion beam decreased linearly with the increase of the opening angle of the beam. With the change of the opening direction of the beam, the modal frequencies of the torsion beam showed different sine. For the beam away from the Bush, the modal frequencies of torsion beams showed a downward trend. According to the analysis of the mechanism, the simplified model of the torsion beam was optimized. The modal frequency of the torsion beam can be greatly improved by optimizing the three beam structure parameters without changing the mass of the beam. The accuracy of the mechanism analysis was proved effectively.

Abstract:In this paper, referring to the uneven distribution of the grinding harden layer along the grinding direction and the deformation of the workpiece surface after grinding, a kind of grinding method was put forward based on the temperature compensation to improve the uniformity of the grinding harden layer. The workpiece was electrically heated by a copper electrode with a 304 stainless steel gasket mounted at the cut-in zone of the workpiece, and a closed loop was formed after electrifying. Because the 304 stainless steel is of the high resistivity and low thermal conductivity, the high temperature on the cut-in zone appeared. Thus, the increased harden layer was formed on the cut-in zone, and the uniformity for the grinding harden layer distribution can be also improved. The distribution of grind-hardening layer and the workpiece deformation were studied under the different preheating temperature and different thickness of the 304 stainless steel. The results show that the grinding force and the grinding harden layer depth can be increased under the preheating condition. With the increasing thickness of the stainless steel gasket at the cut-in zone of the workpiece, the deformation of the ground workpiece is reduced. At the same time, the uniformity for the harden layer depth distribution is also improved.

Abstract:Aiming at improving the uniformity of sealant′s contact pressure distribution for the proton exchange membrane fuel cells, the contact pressure distribution in the four stacks with different layers was tested using a Fujifilm pressure membrane. The test results were visualized by using the platform built in Matlab. Based on the Mooney-Rivilin super-elastic material constitutive model, finite element models of the sealant plane and the stack cross section were established, which were used to design the sealant structure with arcs and rings. Equations for correcting the initial sealant thickness were given in which the uniformity of contact pressure along the integrated force was improved. The results show that the maximum difference in the contact pressure of the sealant in the plane is 1.2 MPa. Along the integrated force, the contact pressure near the end plate is greater than that in the intermediate layers and the more layer results in the lower contact pressure at the same layer. When the contact area is the same, the standard deviation of sealant pressure in plane with the arc structure is 41% less than that of the original structure, and the ring is 30% less than the original structure. For different layers of the stack, the contact pressure after correcting the initial thickness of the sealant maintains around the best. This study can provide a kind of sealing structure that maintains the consistent performance in the fuel cell stack.

Abstract:To evaluate and optimize the performance of the serial production lines with multiple rework loops, according to the principles of quality management and lean production, a novel inspection mechanism, "Instant Checking", different from the traditional ones, was introduced in this paper. The PSM problems to the systems with multiple machines and buffers were investigated. Based on the probability theory and the Markov chain, a dynamic probability transition matrix was built to disclose the relationships between the production performance (WIP: work-in-process inventory and PR: production rate) and the status of machines and buffers. Further, the transient analysis on the machines and buffers was conducted with iterative computation. The results of the analysis show the feasibility to improve the production performance by optimizing the system′s scale and buffer capacity. The numerical experiments were conducted to verify the effectiveness of this model.

Abstract:In order to solve the problem of vehicle stability control after single wheel brake failure in the brake-by-wire system, the control strategy of optimal braking force distribution was proposed by cooperating the steer-by-wire and brake-by-wire systems. To meet the driver's desired deceleration as closely as possible, the braking force of the remaining three wheels was redistributed initially by the sequential quadratic programming method. The front steering controller was designed by sliding mode control method in order to prevent the vehicle from deflection and spin caused by the braking force reconstruction. Considering the influence of the front steer on the longitudinal force of the tire, the mathematical model of tire lateral force based on the magic formula was established. The braking force was optimized in the real time under the side slippery condition by the sequential quadratic programming method. A co-simulation experiment established by Simulink and Carsim was carried out to analyze the strategy, and the result showed that the yaw rate of the vehicle quickly converged to 0 and the lateral deviation displacement was less than 0.1 m. The result verifies that the proposed method of optimal braking force distribution can improve the braking stability of single wheel brake failure vehicle under different braking conditions.

Abstract:With the development of automotive active safety technology, this paper studied the protective performance of Integrated Active and Passive Seatbelt (IAPS) for occupants, and carried out a robust optimization design in order to further promote the development of Integrated Active and Passive Seatbelt (IAPS) technology and the wide application of IAPS. First of all, this paper compared and analyzed the protection performance of IAPS Conventional Pyrotechnic Seatbelt (CPS) and reversible pretension seat belt (RPS) for occupants by Madymo software. Then, taking the occupant head injury (HIC15) and Chest compression (Cdef) as the objective function, the Kriging agent model was constructed. The Multi-objective Particle Swarm Optimization (MPSO) was used to optimize 6 key parameters of IAPS, including reversible pretightening force, reversible pretightening time, pyrotechnic seat belt pretightening time, expansion rate of seat belt, limited force value of seat belt and activation time of airbag. Based on the iSIGHT multi-disciplinary optimization platform, the optimal Latin square was used to sample the optimized Pareto non inferior solution, and the Monte Carlo method was used to simulate the samples to meet the 6 Sigma robustness design criteria. Finally, the optimal solution was selected based on the risk of occupant injury. The results show that IAPS is superior to CPS and RPS in occupant protection. In addition, the multi-objective 6 Sigma robustness optimization design not only significantly reduces the head damage value (HIC15) and Chest compression (Cdef) of occupants, but also reduces the mean and variance of IAPS quality characteristics, making the design variables far away from the boundary constraints. Therefore, the consistency and reliability of product quality for IAPS are improved.

Abstract:A mixed elastohydrodynamic lubrication (mixed-EHDL) numerical model was established considering the microgroove bottom shapes of water lubricated journal bearings. The effects of different microgroove bottom shapes including semi-ellipse, rectangle, isosceles triangle, left triangle and right triangle on the mixed lubrication performance of water lubricated journal bearings were studied. The result showed that the ability to improve the mixed lubrication performance and load capacity can be ranked in the sequence of right triangle, isosceles triangle, left triangle, semi-ellipse, and rectangle. In the elastohydrodynamic lubrication stage, the microgroove bottom shapes had little influence on the friction coefficient of the water lubricated journal bearings, while in the mixed lubrication stage, with the increase of rotation speed, the effects of microgroove bottom shapes on the contact load and friction coefficient presented a regularity that it increased first, then decreased and finally tended to be uniform. In the bearing area, the right triangle bottom shapes involved a micro-step bearing effect which can significantly improve the lubrication performance, comparing to semi-ellipse, isosceles triangle, left triangle and rectangle bottom shapes.

Abstract:In the grid-connected inverter based on the deadbeat current control, the filter inductance variation and one-step-delay control delay affect the distortion of the grid current, stability and dynamic response speed of the system. In this paper, a deadbeat grid-connected control method based on robust PWM is proposed, which reduces the distortion of the grid current caused by the filter inductance variation, effectively solves the delay of the one-step-delay control, reduces the characteristic root equation order of the closed-loop transfer function of the system, and improves the stability and dynamic response speed of the system. The influence of the filter inductance deviation coefficient on the system performance is analyzed, and the filter inductance deviation coefficient of the system critical stability increases with the increase of the parasitic resistance of the filter inductance and the line equivalent resistance and decreases with the increase of the sampling frequency. Considering the stability and dynamic response speed of the system, the optimal selection range of the key control parameters is given. Simulation and experimental results verify the effectiveness of the proposed method.

Abstract:In order to achieve the goal of the effective path planning and trajectory tracking of UAV (Unmanned Aerial Vehicle), one approach based on the RRT (Rapidly Exploring Random Trees) algorithm proposes a path planning algorithm for UAV in the environment of electric towers. Under the combination of the dynamics characteristics of UAV and the randomness of RRT, the algorithm with constraint of the maximum path angle and path height plans a path which gradually approximates to the target point and overcomes the failure problem of RRT in the narrow space planning. The simulation experiment is established in the ROS (Robot Operating System)-Gazebo and verifies the practicability of the algorithm.

Abstract:This paper proposed a position compensation method for brushless DC motors with trapezodial back-EMFs. The conventional compensation method of Hall sensors is very complex because of its moving hall sensors on motor body .In this paper, the bus voltage and bus current were used to obtain the commutation time of the BLDC motor, and the optimal advance angle of Hall sensors was determined to achieve the purpose of correcting the Hall position. Finally, the simulation results based on BLDCM with three Hall sensors in the three-phase two-conduction mode effectively and reasonably verify that the proposed methods can modify deviation angle of Hall sensors, make the phase current stable and run up to normal operation mode through the Matlab simulation platform,which validates the feasibility and effectiveness of the proposed strategies.

Abstract:A low-power adaptively biased output-capacitor-free low-dropout linear regulator was designed. In order to tackle the problem that the inversion coefficients of different types of input transistors in each error amplifier stage may vary asynchronously under adaptive bias caused by mismatches in the design and process, an error amplifier comprised of the recycling folded cascode amplifier and transconductance-boosting amplifier was proposed. The driving ability for the power transistor was improved by the adopted pull-push output structure. Nested Miller compensation and adaptive bias were used to solve the stability problem of output-capacitor-free low-dropout regulator and improve the current efficiency at light loads. The regulator chip was implemented in SMIC 0.18 μm CMOS process with a layout area of 0.019 9 mm2. The Monte Carlo post-simulation results show that the load current range is 10 μA~100 mA with the maximum load parasitic capacitance of 100 pF, and the quiescent current is 1 μA at the minimum load condition. The load regulation and line regulation are 3.5 μV/mA and 0.372 mV/V, respectively. The designed low-dropout regulator has the merits of low power consumption, no off-chip capacitor and small area, which indicates that it is a good choice as intellectual property core of the power management for the system on chip.

Abstract:By the frequency domain analysis of phase noise, the optimization model of Lesson noise was established and the parameters in the circuit were improved. Meanwhile, the small signal model was established to optimize the parameters in the pre-suppression circuit. In this way, the phase noise and stability were studied for the cross-coupled integrated quartz crystal oscillator with RC filter. Furthermore, the circuit and layout were designed, simulated and optimized by Cadence with NUVOTON 0.35 μm process. Subsequently, the fabrication and test were carried out under the supply voltage of 3.3 V. The results indicated that the frequency of output was 20 MHz and the phase noise of the oscillator can reach -135 dBc/Hz @ 1 Hz, -156.4 dBc / Hz @ 10 kHz, and -169.2 dBc/Hz @ 1 Hz, respectively. The ripple wave was less than 81 ppm and 71 ppm, respectively, with the variation of the supply voltage in the range of ± 10% and the temperature range from -25 ℃ to 85 ℃ .

Abstract:In order to deal with the problems of redundant and failed coverage in the traditional random stimuli for cache coherence verification, a high level structural stimuli generation algorithm and the corresponding functional coverage model were presented. Firstly, conflict memory accesses were categorized into basic/complex synchronizations, and thus abstracted into general bipartite graph model. Consequently, a general layered equivalence partition algorithm of ISS and the corresponding high level HSPC (Host Slave Pair Coverage) functional coverage model were proposed. Finally, two structural stimuli generation algorithms based on the search of ISS tree were presented. Experiments were performed in the functional verification of the cache system of IME-Diamond SoC, and the result indicates the HSPC coverage model can help uncover functional bugs more easily when compared with code coverage, and structural stimuli generation can reduce 96.3% stimuli for coverage convergence when compared with random stimuli generation.

Abstract:This paper proposed an improved hierarchical flow for physical design in deep sub-micron technology. This flow can reduce routing congestion and improve timing delay. The key point of this flow is to use the external connectivity information of the target block to design the floorplan, which could achieve a good place and route result in one iteration using quantitative analysis, saving time and efforts from multiple failed iterations. The proposed flow was tested on a large mux block in DSP design in SMIC 65 nm low leakage process, and the result showed it improved 20% in area and 35% in timing delay compared with the traditional flow.

Abstract:Traditional image segmentation methods based on superpixel still have many problems in terms of consistency of edge segmentation, computational efficiency and adaptability of merging algorithms. We combine domestic and foreign research advances and propose a novel superpixel merging image segmentation method, which adopts ERS superpixel over-segmentation algorithm and uses intensity and gradient histogram as superpixel features. Additionally, EMD method is used to calculate feature distance and the merging self-adaptive threshold is obtained by mixing Weibull model to complete the segmentation. As a result, the time complexity of proposed algorithm is reduced to O(N), and the segmentation process is not required to manually select the region to be segmented. Compared with current methods, experiment results show that the proposed method has better performance on boundary accuracy and processing efficiency.

Abstract:A particle filter method based on fruit fly optimization algorithm is proposed to alleviate the sample impoverishment caused by resampling. When fruit flies forage, they usually fly from low concentration areas to high concentration areas efficiently and constantly. This optimum process is introduced into the particle filter to drive particles towards the high likelihood areas ceaselessly, and thus improves the overall quality of the particle swarm. Considering that the premature convergence is always associated with the fruit fly optimization algorithm, crossover and mutation operations of genetic algorithms are applied herein adaptively to keep the diversity of samples. Firstly, the particle distribution is improved by cross operation. When the algorithm falls into the local optimum, the Cauchy mutation perturbation is then used to help the fruit fly optimization algorithm jump out of the local optimal point effectively and continue searching for global extremum. The nonlinear simulations and target tracking experiments show that the proposed algorithm improves the estimation accuracy of the nolinear systems state, and it has better stability and reduces the number of particles required for state estimation at the same time.

Abstract:Stereoscopic image quality evaluation is widely employed in the field of stereo image processing. Based on accurate resolution of wavelet-packet, a novel algorithm for no-reference stereoscopic image quality assessment is proposed. It evaluates stereo image quality via fusion map, which consists of cyclopean map and difference map. First, the stereo image pair is decomposed by wavelet-packet, and afterwards the decomposed left and right views are fused to obtain cyclopean map and difference map based on the principle of binocular rivalry and binocular suppression. Then, Natural Scene Statistics (NSS) features and information entropy are extracted on the fusion map; besides, the structural similarity feature is extracted by taking into account the internal relations between the left and right views. Finally, the Support Vector Regression (SVR) is used to establish model between the perception features and subjective scores, which can predict the objective evaluation score. The experimental results on LIVE 3D image databases show that the proposed algorithm has high consistency with the subjective evaluation results, and it outperforms state-of-the-art stereoscopic image quality assessment algorithms and is in accordance with the human visual perception characteristics.

Abstract:This paper proposed a SAH-KD tree construction method for ray tracing to solve the problem of low parallel degree and low efficiency in the existing algorithms. The algorithm first obtains the ordered index on the three latitudes by sorting the primitive bounding boxes according to the left value. Then, according to the node bounding box, we choose the dimension to be divided and generate the candidate partition points of each node under this dimension. Finally, the SAH value of each candidate point was calculated based on the spatial tree in GPU, and the minimum SAH value of each node was selected for partitioning. Four common scenarios were used for testing performance of the algorithm, and compared the efficient serial and parallel GPU algorithm. The results show that the proposed algorithm can achieve 4~6 and 1.3~1.5 times faster than the contrast method when generating the same quality KD tree. When the number of GPU cores fold increases, the speedup ratio reaches a near multiple.

Abstract:The selection of kernel functions has an important influence on the classification results of support vector machines. This paper proposed a kernel functions selection method based on rank sum test in order to enhance the selection objectivity, where the error degree adopted in the rank sum test was represented by the distance between the error instance and the interface of support vectors. By comparing with other statistical methods, such as K-folding cross validation and paired t test, the classification abilities of nine common kernel functions were quantitatively studied based on 15 datasets. Different from parameter test methods, the rank sum test does not assume the data distribution(in some cases data cannot satisfy the assumed distribution), the experimental data proves that the rank sum test not only can objectively evaluate the classification abilities of kernel functions, but also can produce better selection results on some data sets.