Four-wheel vehicle kinematic and geometric constraints for definition of tire slip angle

When considering vehicle safety, tires and all that they represent are a fundamental topic. Tire studies have received a considerable amount of attention from the research community because their improvement has a direct and strong impact on vehicle handling and braking. Within this eld of analysis lies an important behavioral feature: the tire slip angle, which is a consequence of lateral forces acting on the tire. This characteristic is predicted in some cases and evaluated experimentally in others. This paper addresses another way to assess the slip angle. We propose a mathematical model that describes a constraint linking the slip angle and steering angle that make a vehicle turn. We present a simplied kinematic model (based on the classic bicycle model) and a four-wheel model, which makes all of the angles involved compatible with each other. In our case, the match will be given by the determination of the turning radius. Two different scenarios, understeering and oversteering vehicles, were simulated, and the results and conclusions reached are presented herein.     

Possible experimental method to determine the suspension parameters in a simplified model of a passenger car

Currently, as well as in the past, researchers have shown great interest in developing suspension systems for vehicles and especially in the design and optimization of the suspension parameters, such as the stiffness and the damping coefficient. These parameters are considered to be important factors that have an influence on safety and improve the comfort of the passengers in the vehicle. This paper describes a simplified methodology to determine, in a quick manner, the suspension parameters for different types of passenger cars equipped with passive suspension systems. Currently, different types of passenger cars are produced with different types of suspension systems. Finding a simplified methodology to determine these parameters with sufficient accuracy would contribute a simplified and quick method to the inspection of the working conditions of a suspension system. Therefore, a simple system to determine these parameters is needed. An analysis of the suspension parameters is performed using mathematical modeling and numerical analysis conducted using the Working Model software. The result derived from the developed methodology shows small errors when compared with the generic values, and it can be concluded that the design of the suspension parameter measurement device using the developed methodology is useful, simple, and has sufficient accuracy.     

Fuzzy energy management strategy for a hybrid electric vehicle based on driving cycle recognition

By considering the effect of the driving cycle on the energy management strategy (EMS), a fuzzy EMS based on driving cycle recognition is proposed to improve the fuel economy of a parallel hybrid electric vehicle. The EMS is composed of driving cycle recognition and a fuzzy torque distribution controller. The current driving cycle is recognized by learning vector quantization in driving cycle recognition. The torque of the engine and the motor is controlled by a fuzzy torque distribution controller based on the required torque of the hybrid powertrain and the battery state of charge. The membership functions and rules of the fuzzy torque distribution controller are optimized simultaneously by using particle swarm optimization. Based on the identification results of driving cycle recognition, the fuzzy torque distribution controller selects the corresponding membership function and rule to control the hybrid powertrain. The simulation research based on ADVISOR demonstrates that this EMS improves fuel economy more effectively than fuzzy EMS without driving cycle recognition.     

Robust control for 4WS vehicles considering a varying tire-road friction coefficient

A µ-synthesis for four-wheel steering (4WS) problems is proposed. Applying this method, model uncertainties can be taken into consideration, and a µ-synthesis robust controller is designed with optimized weighting functions to attenuate the external disturbances. In addition, an optimal controller is designed using the well-known optimal control theory. Two different versions of control laws are considered here. In evaluations of vehicle performance with the robust controller, the proposed controller performs adequately with different maneuvers (i.e., J-turn and Fishhook) and on different road conditions (i.e., icy, wet, and dry). The numerical simulation shows that the designed µ-synthesis robust controller can improve the performance of a closed-loop 4WS vehicle, and this controller has good maneuverability, sufficiently robust stability, and good performance robustness against serious disturbances.     

Lateral stability control of dynamic steering for dual motor drive high speed tracked vehicle

In this paper, the torque and power required by dual motors for electric tracked vehicle during dynamic steering maneuvers with different steering radiuses are analyzed. A steering coupling drive system composed of a new type of center steering motor, two Electromagnetic (EM) clutches, two planetary gear couplers, and two propulsion motors is proposed for the dual motors drive high speed electric tracked vehicle (2MHETV), which aims to improve its lateral stability. An average torque direct distribution control strategy based on steering coupling and an optimization-distribution-based close-loop control strategy are designed separately to control the driving torque or regenerative braking torque of two propulsion motors for vehicle stability enhancement. Then models of the 2MHETV and the proposed control strategy are established in Recudyn and Matlab/Simulink respectively to evaluate the lateral stability of dynamic steering for the 2MHETV with different steering radiuses on hard pavement.The simulation results show that the lateral stability of the 2MHETV can be significantly improved by the proposed optimization-distribution-based close-loop control strategy based on steering coupling system.     

Optimal tyre usage for a Formula One car

Variations in track temperature, surface conditions and layout have led tyre manufacturers to produce a range of rubber compounds for race events. Each compound has unique friction and durability characteristics. Efficient tyre management over a full race distance is a crucial component of a competitive race strategy. A minimum lap time optimal control calculation and a thermodynamic tyre wear model are used to establish optimal tyre warming and tyre usage strategies. Lap time sensitivities demonstrate that relatively small changes in control strategy can lead to significant reductions in the associated wear metrics. The illustrated methodology shows how vehicle setup parameters can be optimised for minimum tyre usage.     

Effect of injection timing,injector opening pressure,injector nozzle geometry,and swirl on the performance of a direct injection,compression-ignition engine fuelled with honge oil methyl ester (HOME)

Increasing petroleum prices, increasing threat to the environment from exhaust emissions and global warming have generated intense international interest in developing renewable and alternative non-petroleum fuels for engines. Evolving feasible technology and recurring energy crisis necessitated a continued investigation into the search for sustainable and clean-burning renewable fuels. In this investigation, Honge oil methyl ester (HOME) was used in a four stroke, single cylinder diesel engine. Tests were carried out to study the effect of fuel injection timing, fuel injector opening pressure (IOP) and injector nozzle geometry on the performance and combustion of CI engine fuelled with HOME. Injection timing was varied from 19°bTDC (before top dead centre) to 27°bTDC in incremental steps of 4°bTDC; injector opening pressure was varied from 210 bar to 240 bar in steps of 10 bar. Nozzle injectors of 3, 4 and 5 holes, each of 0.2, 0.25 and 0.3 mm size were selected for the study. It was concluded that retarded injection timing of 19°bTDC, increased injector opening pressure of 230 bar and 4 hole nozzle injector of 0.2 mm size resulted in overall better engine performance with increased brake thermal efficiency (BTE) and reduced HC, CO, smoke emissions. Further air-fuel mixing was improved using swirl induced techniques which enhanced the engine performance as well.     

Novel hybrid optimal algorithm development for DC motor of Automated Manual Transmission

A novel hybrid optimal algorithm for DC motor of electro-mechanical Automated Manual Transmission (AMT) is presented. It combines non-linear time optimal controller and optimal Linear Quadratic Regulator (LQR) consequently used at different shifting stages. The working principle and dynamic characteristics of the AMT system are firstly presented, and the model of the DC motor is analyzed in detail. The non-linear time optimal controller is designed to explore the potential of the motor and minimize the gear shifting time. While the optimal LQR is then adopted at the final shifting stage to avoid overshoot and increase system robustness. Based on the position control algorithm of the actuators, the coordinated shifting control strategy is also proposed. Both simulation and vehicle test results demonstrate that, this control algorithm could decrease the shifting time and improve the shift quality effectively.     

Knock in dual-fuel diesel combustion with an E85 ethanol/gasoline blend by multi-dimensional simulation

In this paper, knocking combustion in dual-fuel diesel engine is modeled and investigated using the CFD code coupled with detailed chemical kinetics. The ethanol/gasoline blend E85 is used as the primary fuel in a dual-fuel combustion concept based on a light-duty diesel engine equipped with a common-rail injection system. The E85 blend is injected and well mixed with intake air in the intake manifold and is ignited by the direct injection diesel fuel. A 46-species, 187-reaction Multicomponent mechanism is adopted to model the auto-ignition process of the E85/air/diesel mixture ahead of the flame front. Based on the model validation, knocking combustion under boost and full load operating condition for 0 %, 20 %, 50 %, as well as 70 % E85 substitute energy is simulated. The effects of E85 substitute rate and two stage injection strategies on knock intensity, power output, as well as location of the auto-ignition initiation is clearly reproduced by the model. The calculation result shows that, for a high E85 rate of 50 % and 70 % with single injection strategies, the most serious knock and the origin of auto-ignition always occurs far away from where the flame of diesel spray is first generated, at the center of combustion chamber, due to higher pressure wave, relatively richer E85 mixture and longer distances of flame propagation. The two stage injection strategies with a small amount of diesel pilot injection ahead of the main injection primarily influence the ignition behavior of the directly injected fuel, leads to a lower pressure rise rate and a reduced propagation distance, both of which contribute to the attenuation of knock intensity for a higher E85 rate.     

基于CML的级联失效下异质多层交通网络节点抵抗特性研究

为了有效刻画拟合实际的多层交通网络级联失效过程,识别多层网络中对整体韧性安全影响显著的对象,提升交通网络抵抗失效的能力,建立一种基于耦合映象格子（Coupled Map Lattice, CML）的级联失效模型。首先,将交通管控措施赋予交通网络节点额外的容纳能力引申为节点抵抗特性,通过为CML添加抵抗参数H,形成考虑抵抗特性的级联失效（HCML）模型,沿常值-拓扑关联-时变拓扑关联的路径深化H的表征方式,并在小世界（Small World, SW）网络上对比3类表征方式的优劣;其次,应用Space H方法建立异质3层公共交通网络,对比度值与介数2种时变拓扑指标关联的抵抗效果,探究不同交通层抵抗系数对网络失效的影响程度;最后,在6组不同的网络结构上进行HCML模型与传统模型的对比,讨论建网方法、网络规模等不同网络性质的差异对模型有效性的影响,并结合实际客运数据验证HCML模型优越性。研究结果表明：3类表征方式中时变拓扑关联可以兼顾其余2类的优点;同等条件中网络在介数关联的抵抗特性作用下失效增速更缓,模型识别得到的对网络整体失效影响更大交通方式符合客流量实际;HCML模型在多种不同类型的多层交通网络中均可以有效实施,相比于传统模型,HCML模型的最终失效比例平均下降了5.78%,与实际交通级联失效过程更加拟合。