Design of power split transmission: Design of dual mode power split transmission

The power split type hybrid system transmits engine power by dividing it into the electrical unit and the mechanical unit. Its power transmission efficiency is highest at the mechanical point (MP), where the full power is transmitted to the mechanical unit. In this study, the equation for the MP was derived for the gear ratios of a general 4-node lever model. The MP characteristics for the transmission ratio (TR) of the input split and compound split structures were examined using the equation derived. Using the examined input split and compound split structures, a systematic design method for the dual mode power split transmission was proposed. In the dual mode power split transmission, the MP could be positioned at the desired TR, and the input split and compound split modes could be selectively used according to the clutch combination, which leads to the operation of the vehicle within a high system efficiency range.     

Robust lane markings detection and road geometry computation

Detection of lane markings based on a camera sensor can be a low-cost solution to lane departure and curve-over-speed warnings. A number of methods and implementations have been reported in the literature. However, reliable detection is still an issue because of cast shadows, worn and occluded markings, variable ambient lighting conditions, for example. We focus on increasing detection reliability in two ways. First, we employed an image feature other than the commonly used edges: ridges, which we claim addresses this problem better. Second, we adapted RANSAC, a generic robust estimation method, to fit a parametric model of a pair of lane lines to the image features, based on both ridgeness and ridge orientation. In addition, the model was fitted for the left and right lane lines simultaneously to enforce a consistent result. Four measures of interest for driver assistance applications were directly computed from the fitted parametric model at each frame: lane width, lane curvature, and vehicle yaw angle and lateral offset with regard the lane medial axis. We qualitatively assessed our method in video sequences captured on several road types and under very different lighting conditions. We also quantitatively assessed it on synthetic but realistic video sequences for which road geometry and vehicle trajectory ground truth are known.     

Effects of injection parameters on the spray characteristics of swirl and slit injectors using the Mie-scattering method

We investigated the effects of injection parameters such as injection pressure, ambient pressure, and ambient temperature on spray characteristics. We calculated the turbulence occurring point (t _c ), defined as the time required to generate a vortex, and the deceleration point (t _b ), defined as the time when spray penetration begins to decelerate, to elucidate the breakup mechanism of the test injectors. The spray velocity coefficient (C_v) was obtained to evaluate the spray characteristics. As the ambient pressure increases in the case of a slit injector, C_v decreases. We investigated the effects of nozzle tip shape according to injection pressure, ambient pressure, and fuel properties on spray characteristics and provide a C_v value of 0.38 for the swirl injector with a spray angle of 60° and the slit injector under atmospheric conditions. The value of C_v in the case of a slit injector was reduced by increasing the ambient pressure. Our results suggest that C_v of a swirl injector is constant regardless of changes in ambient pressure, injection pressure, and fuel properties. On the other hand, C_v of a slit injector is altered by changes in ambient pressure.     

Design and optimization of an LPG roller vane pump for suppressing cavitation

A roller vane type liquefied petroleum gas (LPG) pump was developed for a liquid phase LPG injection (LPLi) engine. Most of the LPG pumps used in the current LPLi engines are installed inside of the LPG tank, but this pump is intended to be installed outside of the LPG tank to overcome the difficulty of fixing an in-tank pump. Because LPG has a low boiling point and high vapor pressure, it usually causes cavitation in the pump and consequently deteriorates the flow rate of the pump. The purpose of this work is to optimize the design of the roller vane pump in order to suppress cavitation and increase the fuel flow rate by using a computational fluid dynamics (CFD) analysis. In order to achieve these goals, the intake port configuration and the rotor of the roller vane pump were redesigned and simulated using STAR-CD code. Computation was performed for six different models to obtain the optimized design of the roller vane pump at a constant speed of 2600 rpm and a constant pressure difference between the inlet and outlet of 5 bar. The computation results show that an increased intake port cross-section area can suppress cavitation, and the pump can achieve a higher flow rate when the rotor configuration is changed to increase its chamber volume. When the inlet pressure difference is 0.1 bar higher than the fluid saturation pressure, the pump reaches its maximum flow rate.     

Robust optimization design method for powertrain mounting systems based on six sigma quality control criteria

This paper presents a robust optimization design method based on Six Sigma quality control criteria to improve the design of a powertrain mounting system (PMS). The powertrain is modeled as a rigid body having six degrees of freedom (DOF) connected to a rigid base by four rubber mounts, and each mount is simplified as a three-dimensional spring-damper element in its local coordinate system (LCS). The calculation method based on energy decoupling is used to estimate the decoupling ratios of a PMS. The location and static stiffness of each mount and the orientations of the two anti-torsion mounts are selected as uncertain design variables, and the nominal values of these design variables are optimized to obtain a robust Six Sigma design for a PMS. The uncertain design variables are characterized by a perturbation or percent variation around their nominal values. The generalized reduced gradient (LSGRG2) optimization method is employed to solve the robust optimization problem, and a second-order Taylor series expansion is used to estimate the statistical properties of the performance constraints and objectives. The optimization results show that the robust design ensures good robustness or high reliability for the natural frequencies, decoupling ratios, and frequency separation constraints of a PMS.     

Simple estimation of high-frequency radiation from a muffler shell

The acoustic design of exhaust mufflers has mainly focused on reducing the discharge noise from the tailpipe. However, the noise that is transmitted through the muffler jacket and the endplate becomes important since the muffler reduces the amount of discharge noise when it has an optimized design. It is known that the contribution to the overall exhaust noise of the muffler shell is significant in the mid- and high-frequency ranges. The current problem is that there are no appropriate computational tools at high frequencies. A simple method to analyze the 1/3-octave band of sound radiating from an arbitrary shape (like a muffler) was employed to predict the band spectrum of the radiated noise. The calculation method included formulating the boundary integral, which was modified into a quadratic form in order to enable the prediction of the intensity levels in a band analysis. Monopole and dipole source terms in the conventional BEM were transformed into the auto- and cross-spectra of the two vibrating sources, in which the cross-spectra could be eventually omitted by assuming that the correlation coefficients were negligible. The method was adopted in an abrupt calculation of the shell noise in 1/3-octave band levels without nonuniqueness problem. In comparison with the measured data, the simulation result showed roughly 3-dB errors at most of the field points, excluding several special points that were normal to the shell and exhibited a maximum 5-dB error.     

Modeling,parameter estimation and nonlinear control of automotive electronic throttle using a Rapid-Control Prototyping technique

An electronic throttle consists of a DC motor, spur gears, a return spring, a position sensor, power electronics and an electronic control unit. Fast and precise position control of this electromechanical system is relatively difficult due to very high friction and the strong nonlinearity of the spring. Simple application of linear control, such as PID, fails. In this paper, two new controller structures suitable for different reference signal types are described. The key component of the position controller is the friction compensator based on either/both feedforward or feedback principles. The quality of the resulting behavior was measured using several criteria including the measure of control activity around the equilibrium position. The control activity directly influences the vibration, the noise and the wear of the servo system. The proposed controllers demonstrated superior behavior compared with other published structures.     

前后多车影响的跟驰模型及稳定性分析

驾驶员在跟车行驶过程中,通常会通过视野前后车辆的行驶状态来调整自己的跟驰行为,基于此本文提出了一种考虑驾驶员视野内双前车和后车对跟驰车辆影响的改进跟驰模型.根据线性稳定分析方法,得到了改进模型的中性稳定性条件,并通过计算机仿真模拟进行了验证.为了进一步加强验证结果及说明改进模型的优越性,同经典FVD模型进行了数值仿真对比.仿真结果表明：灵敏度α越大越有利于提高改进跟驰系统的稳定性;同经典FVD跟驰模型相比,改进模型抵抗干扰的能力更突出,能够消散交通系统中的微小扰动,具有抑制交通拥堵和稳定交通流的有利作用.     

Research on control strategy for differential steering system based on H mixed sensitivity

The differential steering system (DSS) of electric wheel vehicle gets rid of the restrictions of traditional steering system completely. As an ideal steering technology, it not only realizes the perfect combination of the road feel and the steering portability, but also realizes the harmony and unification between the steering maneuverability and safety. The structure and basic theory of the DSS of electric wheel vehicle are discussed in this paper. Based on these, the dynamic model of the steering system is built. Considering of the uncertainties and disturbances existing in the model, the H_∞ mixed sensitivity control theory is applied to achieve better tracking performance and road feel in the process of steering. Then, a H_∞ mixed sensitivity controller is designed to restrain the effect of the road disturbance and model uncertainties. The simulation results indicate that the DSS with the designed controller can effectively restrain the effect of noises and disturbances caused by random motivation from road, torque sensor measurement and model parameter uncertainty, and enable the driver to obtain satisfactory road feel.     

Modeling and control strategy development of a parallel hybrid electric bus

This paper presents the system modeling, control strategy design, and experiment validation of a parallel hybrid electric bus with an automatic manual transmission (AMT) and a dry clutch. The mathematical model representation and the system architecture of the powertrain are first described. Next, a complete control scheme including energy management strategy and coordinated control of the AMT and the clutch is presented. The controller and powertrain models are then integrated in a way that the power management and the hybrid driveline perform in real world. The analysis and validation through model simulation and comparison with experiment data are conducted. A good agreement between the model and experiment demonstrates the efficacy and credibility of the integrated model. The integrated model is employed in both simulation and bench-test assessments for the development of a hybrid control unit. The results indicate that the model-based design methodology is beneficial to systematically analyzing and understanding the dynamics of hybrid electric powertrain.