Design methodology to reduce the chest deflection in US NCAP and EURO NCAP tests

There have not been many studies on the factors that affect chest deflection, although the US NCAP thoracic injury criterion was recently shifted from the 3-msec clip to chest deflection. This study explored these factors and proposed a design methodology for the factors to minimize chest deflection. Because injuries can become severe if the driver crashes against the vehicle interior, this study also sought a solution using a penalty function to prevent crashes with the interior and minimize injuries. First, a MADYMO model was made to simulate US NCAP and EURO NCAP tests by one-to-one and stochastic verifications. Second, a sensitivity analysis was conducted to find the major factors that affect chest deflection. Lastly, the factors identified via the sensitivity analysis were optimized to propose design guidelines that helped vehicles receive high star ratings in US NCAP and EURO NCAP tests and helped minimize the possibility of hard contact between the driver and the vehicle interior by utilizing a penalty function and the Taguchi method.     

Development of a control strategy based on the transmission efficiency with mechanical loss for a dual mode power split-type hybrid electric vehicle

In this study, a control strategy for a dual mode power split-type hybrid electric vehicle (HEV) is developed based on the powertrain efficiency. To evaluate the transmission characteristics of the dual mode power split transmission (PST), a mechanical loss model of the transmission (TM loss) is constructed. The transmission efficiency, including the TM loss, is evaluated for the dual mode PST. Two control strategies for the dual mode PST are proposed. An optimal operation line (OOL) control strategy is developed to maintain a high engine thermal efficiency by controlling the engine operation point on the OOL. A speed ratio (SR) control strategy is proposed to obtain a greater transmission efficiency by shifting the engine operation point when the dual mode PST operates near the mechanical points. Using the TM loss and the proposed control strategies, a vehicle performance simulation is conducted to evaluate the performance of the two control strategies for dual mode PST. The simulation results demonstrate that, for the SR control strategy, the engine efficiency decreases because the engine operates beyond the OOL. However, the transmission efficiency of the dual mode PST increases because the PST operates near the mechanical point where the PST shows the greatest transmission efficiency. Consequently, the fuel economy of the SR control strategy is improved by 3.8% compared with the OOL control strategy.     

Forme urbaine et mobilité domicile-travail dans 13 aires urbaines françaises : une analyse multiéchelle

This article provides a multi-scale analysis of the links between commuting patterns and urban form by using both morphological and more classical indicators of urban form (like density). Thirteen French urban areas of more than 500,000 inhabitants (excluding Paris) are compared. The findings highlight the complexity of the links between urban form and commuting patterns because the same indicators of urban form do not have the same influence according to the spatial scale. Even if the influence of the morphological indicators is lower than that of more classical socioeconomic variables (income level, motorization rate), our study discusses the various and multi-scale consequences of urban development on daily travel behaviour.     

Designing a non-linear tracking controller for vehicle active suspension systems using an optimization process

In this paper, a new non-linear tracking controller for vehicle active suspension systems is analytically designed using an optimization process. The proposed scheme employs a realistic non-linear quarter-car model, which is composed of a hardening spring and a quadratic damping force. The control input is the external active suspension force and is determined by minimizing a performance index defined as a weighted combination of conflicting objectives, namely ride quality, handling performance and control energy. A linear skyhook model with standard parameters is used as the reference model to be tracked by the controller. The robustness of the proposed controller in the presence of modeling uncertainties is investigated. The performed analysis and the simulation results indicate that both vehicle ride comfort and handling performance can be improved using the minimum external force when the proposed non-linear controller is engaged with the model. Meanwhile, a compromise between different objectives and control energy can easily be made by regulating their respective weighting factors, which are the free parameters of the control law.     

Robust design optimization of suspension system by using target cascading method

This study presents the robust design optimization process of suspension system for improving vehicle dynamic performance (ride comfort, handling stability). The proposed design method is so called target cascading method where the design target of the system is cascaded from a vehicle level to a suspension system level. To formalize the proposed method in the view of design process, the design problem structure of suspension system is defined as a (hierarchical) multilevel design optimization, and the design problem for each level is solved using the robust design optimization technique based on a meta-model. Then, In order to verify the proposed design concept, it designed suspension system. For the vehicle level, 44 random variables with 3% of coefficient of variance (COV) were selected and the proposed design process solved the problem by using only 88 exact analyses that included 49 analyses for the initial meta-model and 39 analyses for SAO. For the suspension level, 54 random variables with 10% of COV were selected and the optimal designs solved the problem by using only 168 exact analyses for the front suspension system. Furthermore, 73 random variables with 10% of COV were selected and optimal designs solved the problem by using only 252 exact analyses for the rear suspension system. In order to compare the vehicle dynamic performance between the optimal design model and the initial design model, the ride comfort and the handling stability was analyzed and found to be improved by 16% and by 37%, respectively. This result proves that the suggested design method of suspension system is effective and systematic.     

Plug-in HEV with CVT: configuration,control, and its concurrent multi-objective optimization by evolutionary algorithm

Plug-in Hybrid Electric Vehicle (Plug-in HEV) has dramatic improvements in fuel economy and emission reduction. It is most important to decide its optimal configuration, energy management strategy, powertrain sizes, and control logic parameters. For multi-objective optimization, we present a concurrent optimization methodology based on an optimal Plug-in HEV powertrain configuration with continuous variable transmission (CVT). The novelty is using evolutionary algorithm in conjunction with an instantaneous optimal energy management strategy. Simulation results indicate the proposed method can significantly reduce fuel consumption and emissions by simultaneously optimizing the propulsion system parameters as well as the energy control parameters.     

Design of 2-speed transmission for electric commercial vehicle

As environmental and economic interests increase, the need for eco-friendly vehicle such as an electric vehicle (EV) has increased rapidly. Various research of enhancing EV powertrain efficiency and relibility have been studied. In this study, 2-speed shift gears mechanism is designed by using simpson type planetary gear train. This transmission has two planetary gear unit. Gear position is determinded by which ring gear is fixed. Internal components of the transmission are designed for satisfying the required specification of EV. We analyze gear strength, gear mesh efficiency, and transmission efficiency. By manufacturing the transmission prototype and performing some experiments, we verify the application suitability of this transmission.     

Novel evaluation method of fuel consumption and emission for heavy-duty hybrid electric vehicles

This paper is a continuation of a previous paper titled “A novel way to calculate energy efficiency for rechargeable batteries” published on Journal of Power Sources/2012 describing a new method to calculate energy efficiency for rechargeable batteries. The present paper further describes the application of energy efficiency model on the evaluation of fuel consumption and emission for the heavy-duty hybrid electric vehicles (HD-HEVs). A more accurate calculation method of net energy change for power battery pack is proposed based on energy efficiency model of power battery pack. A more simplified and accurate correction method of fuel consumption and emission is also presented based on equivalent mileage. The fuel consumption and emission on chassis dynamometer are measured in the HD-HEVs. The experiment results show that relative errors of fuel consumption and emission between equivalent mileage correction results and linear regression correction results are less than 3%, which verifies accuracy and validates the proposed evaluation method for HD-HEVs fuel consumption and emission.     

Transient modeling and validation of lithium ion battery pack with air cooled thermal management system for electric vehicles

A transient numerical model of a lithium ion battery (LiB) pack with air cooled thermal management system is developed and validated for electric vehicle applications. In the battery model, the open circuit voltage and the internal resistance map based on experiments are used. The Butler-Volmer equation is directly considered for activation voltage loss estimation. The heat generation of cells and the heat transfer from cells are also calculated to estimate temperature distribution. Validations are conducted by comparison between experimental results at the cell level and the pack level. After validations, the effects of module arrangement in a battery pack are studied with different ambient temperature conditions. The configuration that more LiB cells are placed near the air flow inlet is more effective to reduce the temperature deviation between modules.