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.     

Measurement of hydrocarbon and carbon monoxide emissions during the starting of automotive DI Diesel engines

Most of hydrocarbon (HC) and carbon monoxide (CO) emissions from automotive DI Diesel engines are produced during the engine warm-up period and are primarily caused by difficulties in obtaining stable and efficient combustion under these conditions. Furthermore, the contribution of engine starting to these emissions is not negligible; since this operating condition is highly unfavorable for the combustion progress. Additionally, the catalytic converter is ineffective due to the low engine temperature. In conjunction with adequate engine settings (fuel injection and fresh air control), either the glow plugs or the intake air heater are activated during a portion of the engine warm-up period, so that a nominal engine temperatures is reached faster, and the impact of these difficulties is minimized. Measurement of gaseous pollutants during engine warm-up is currently possible with detectors used in standard exhaust gas analyzers (EGA), which have response times well-suited for sampling at such transient conditions. However, these devices are not suitable for the measurement of exhaust emissions produced during extremely short time intervals, such as engine starting. Herein, we present a methodology for the measurement of the cumulative pollutant emissions during the starting phase of passenger car DI Diesel engines, with the goal of overcoming this limitation by taking advantage of standard detectors. In the proposed method, a warm canister is filled with an exhaust gas sample at constant volumetric flow, during a time period that depends on the engine starting time; the gas concentration in the canister is later evaluated with a standard EGA. When compared with direct pollutant measurements performed with a state-of-art EGA, the proposed procedure was found to be more sensitive to combustion changes and provided more reliable data.     

Dynamic analysis of seatbelt systems with anti-inertial release mechanisms

In order to prevent the uncontrolled release of seatbelt buckles due to high acceleration caused by pretensioners, anti-g buckles that have pendulum-shaped g-masses to block the releasing motion are commonly adopted in seatbelt systems. However, even with the wide applications of anti-g buckles, the underlying operational principles of anti-g buckles have yet to be investigated. This work studies conditions for the engagement of the g-mass to prevent inertial release, and conditions for maintaining a blocked state under very high acceleration. Using a multibody model of an anti-g buckle, the effects of various design parameters on the performance of the anti-g buckle have been examined. It turns out that design variables associated with the geometry of the g-mass and its contacting surface configuration play important roles. In order to account for the dynamic interaction between driver and seatbelt, a multibody model of a seatbelt system is combined with a dummy model to form a single dynamic system. Using the measured displacement of the buckle during the explosion of a pretensioner as the driving condition for simulation, dynamic analysis of the seatbelt with driver interaction has been carried out. Through comparison with measured and computed accelerations of webbing, which shows good agreement, the validity of the model has been demonstrated. The dynamic model for seatbelt and driver can be used as a design tool for the development of anti-g buckles.     

Optimising a Car Chassis

This paper presents a method to optimise a car chassis fitted either with passive or active suspensions. Provided that a full vehicle model is available for accurate simulations of many different driving situations (J-turn, lane-change, power-on/power-off on even/rough, dry/wet roads), the method allows to tune the parameters of the chassis system (suspension elastokinematics, stiffnesses, dampings, actuator gains, tyre pressures...) in order to achieve the desired dynamic behaviour of the car in all of the considered driving situations. According with the Global Approximation approach, the original physical car model is substituted by another purely numerical mathematical model (backpropagating Artificial Neural Network). This reduces the simulation time dramatically and enables the optimisation process to come to successful results. The computation of the Pareto-optimal set is performed by using Genetic Algorithms. The method is validated by optimising the parameters of the suspension system of an actual car.     

A Two DOF Model for Jerk Optimal Vehicle Suspensions

Researchers have proposed various active suspension concepts to optimize the tradeoff between ride and handling in passenger vehicles. A few investigators suggested inclusion of the passenger jerk, the derivative of the passenger acceleration, as a measure of ride quality in the performance index. Minimization of a performance index then optimizes both the acceleration and jerk as well as other outputs representing handling quality and design constraints. This approach is called jerk optimal control.

This paper compares two different vehicle models of increasing complexity (the one and two DOF quarter car) using jerk optimal control. Different aspects of suspension performance are investigated, including the structure of the system transfer functions, the structure of the force control laws, and the tradeoffs between the various root mean square (rms) outputs defining system ride and handling performance. Tables compare the numerical results of the two models, allowing predictions of actual vehicle performance.

The results of the two models show the same basic trend for the tradeoff between ride and handling quality: at a constant level of rms passenger acceleration the rms passenger jerk can be reduced significantly, but only at a cost of increased rms tire deflections. In physical terms, a softer ride results in degraded handling performance. For a chosen level of ride improvement, the more realistic two DOF quarter car model predicts more severe degradation of handling. The latter nevertheless predicts a substantial increase in vehicle ride quality is possible through a 55% reduction in jerk. It is expected that actual suspensions could also produce significant increases in ride quality through jerk reduction. Jerk optimal suspensions could find use both in higher end passenger vehicles and in transports for vibration sensitive cargo.     

铁路发展的新机遇

铁路行业发展的关键在于基础设施方面的持续投资.今后几年内机车车辆方面投资的增长也将令人瞩目.     

电力电子装置在混合电动汽车中的应用

混合电动汽车由于其性能和经济上的优势,比纯电动汽车得到更多的用户认可.现在全球两大汽车公司在世界上大多数地区销售的混合电动汽车累计超过12万辆.尽管纯电动汽车在道路运输和短途交通中可得到适当应用,但与非混合的汽车相比,混合电动汽车非常实用,燃料可节省5%～50%,甚至更多.现在由于交流传动使用寿命长,易于采用电力电子控制,它普遍用于混合动力系.但是,因为汽车推进系统独特的应用要求,目前的交流传动还难以满足整个驱动系统性能要求,且达不装置的体积目标.所以,目前混合动力系仍然使用容量过大的电机或电力电子装置的交流传动.本文基于这样的前提:解决混合电动汽车交流传动的宽恒功速比(CPSR)和整体性能最经济的办法是建立在电力电子装置基础上的.文章主要介绍变速装置方面的现状,以及为了提供与客运汽车更好匹配的交流传动装置正在作哪些努力.     

Compressive sensing reconstruction based on weighted directional total variation

Directionality of image plays a very important role in human visual system and it is important prior information of image. In this paper we propose a weighted directional total variation model to reconstruct image from its finite number of noisy compressive samples. A novel self-adaption, texture preservation method is designed to select the weight. Inspired by majorization-minimization scheme, we develop an efficient algorithm to seek the optimal solution of the proposed model by minimizing a sequence of quadratic surrogate penalties. The numerical examples are performed to compare its performance with four state-of-the-art algorithms. Experimental results clearly show that our method has better reconstruction accuracy on texture images than the existing scheme.