A comparative study of hybrid electric vehicle fuel consumption over diverse driving cycles

Environmental pollution and declining resources of fossil fuels in recent years, have increased demand for better fuel economy and less pollution for ground transportation. Among the alternative solutions provided by researchers in recent decades, hybrid electric vehicles consisted of an internal combustion engine and an electric motor have been considered as a promising solution in the short-term. In the present study, fuel economy characteristics of a parallel hybrid electric vehicle are investigated by using numerical simulation. The simulation methodology is based on a fast forward facing simulation model of a parallel hybrid and an internal combustion engine powertrains. The objective of this study is to present the main parameters which result in an optimum combination of hybrid powertrain components in order to obtain a better fuel economy of hybrid powertrains regarding different driven cycles and hybridization factors. Then, the fuel consumption of the parallel hybrid electric vehicles are compared considering various driven cycles and hybridization factors. The results showed that the better fuel economy of hybrid powertrains increases by decreasing average load of the test cycle and the point of the best fuel economy for a particular average load of the cycle moves towards higher hybridization factors when the average load of the test cycle is reduced.     

Mobility analysis of off-road vehicles: Benefits for development, procurement and operation

Nowadays the requirements on off-road vehicles are rising steadily. The ideal vehicle has to provide excellent off-road capability with low fuel consumption, offer a high customizability for each specific mission and, last but not least, it has to be easy to operate. To meet these demands, on the development side a lot of parameter studies have to be carried out. The customer has to compare offers from a multiplicity of suppliers to decide which vehicle fulfills the designated mission task best. And finally, the operator needs the best training on the vehicle to cope with all possible situations in off-road mobility. In response to these needs, the presented simulation program WinMaku was developed to offer a tool to facilitate development, procurement and operator training. Exemplary simulation results show, on the one hand, the influence of specific design parameters, e.g. tire size, engine power, torque characteristics, gear shifting, and engine working conditions, and on the other hand the (beneficial or adverse) effects of operational parameters like driving with maximum/partial engine load, gear selection, engine speed, tire inflation pressure or track tension, on mobility performance. Furthermore results of vehicle comparison analysis are presented. These types of analysis show comparisons of mobility performance of different vehicle types or vehicle concepts (e.g. wheel vs. track) in fulfilling a certain mission profile, characterized by passing a sequence of different soils with various inclines. Endowed with such capability, the presented simulation tool serves as a training tool for operators, provides a cost effective method to assess possible development steps, allows customers to run a pre-selection process prior to expensive and time-consuming field tests, and finally supports mission planning by providing data like expected fuel consumption or time needed to pass a certain mission profile.     

The user and terrain-machine system research

Designing off-road equipment to meet user requirements assumes that research results are brought to bear on real design problems, that the user has been identified, and that the user's needs are communicated to the designer. In the area of military vehicles, these conditions are met. The U.S. Army Mobility Model is an example of how this is done.The Army Mobility Model, a computer simulation technique, allows terrain, vehicle, and driver characteristics to be combined to predict the performance of vehicles according to various criteria such as speed, fuel consumption, etc. The results of the computer analysis appear in map form, and there are also special techniques for finding the optimum route between two points. The data base has been validated by actual vehicle performance measurements.Several recent applications of the Army Mobility Model are discussed. These applications demonstrate that the need for a systematic application of terrain-vehicle research results to vehicle design has been at least partly fulfilled. This simulation technique has developed a stronger communication link between the vehicle designer and user. Establishing this link has created a new demand for a wide variety of vehicle performance predictions for which many predictive relations are not yet fully developed and validated. Adequate research will be necessary to ensure further progress in this direction.     

Gear shifting multi-objective optimization to improve vehicle performance,fuel consumption,and engine emissions

In the present work, the Adaptive-Weight Genetic Algorithm was employed in order to determine the gear shifting strategies that allow an automobile to work in the best compromise among fuel consumption, engine emissions, and vehicle performance. For the assessment of each of the three objective functions, a simulation model based on engine data and on the well-established equations of the longitudinal dynamics was developed. The driving cycle chosen for the calculations was the FTP-75, which takes into account both cold and hot starts, meaning that the transient operation during the warm-up of the catalyst is also considered.     

Nozzle design study for a quasi-axisymmetric scramjet-powered vehicle at Mach 7.9 flight conditions

A nozzle shape optimization study for a quasi-axisymmetric scramjet has been performed for a Mach 7.9 operating condition with hydrogen fuel, aiming at the application of a hypersonic airbreathing vehicle. In this study, the nozzle geometry which is parameterized by a set of design variables, is optimized for the single objective of maximum net thrust using an in-house CFD solver for inviscid flowfields with a simple force prediction methodology. The combustion is modelled using a simple chemical reaction code. The effects of the nozzle design on the overall vehicle performance are discussed. For the present geometry, net thrust is achieved for the optimized vehicle design. The results of the nozzle-optimization study show that performance is limited by the nozzle area ratio that can be incorporated into the vehicle without leading to too large a base diameter of the vehicle and increasing the external drag of the vehicle. This study indicates that it is very difficult to achieve positive thrust at Mach 7.9 using the basic geometry investigated.     

带滑移铰空间机械臂运动规划的双向逼近方法

以双向逼近方法为基础,讨论了载体姿态与位置均不受控制的带滑移铰空间机器臂的运动规划问题．该方法利用系统的非完整动力学性质,仅通过对空间机器臂关节铰运动的控制,即可达到对载体姿态及机械臂关节位置的双重控制效果,从而减少了载体姿态控制燃料的消耗,有效延长了空间机械臂系统的使用寿命．系统数值仿真证明了该方法的有效性．     

Fuzzy evaluation for an intelligent air-cushion tracked vehicle performance investigation

This paper presents the fuzzy logic expert system (FLES) for an intelligent air-cushion tracked vehicle performance investigation operating on swamp peat terrain. Compared with traditional logic model, fuzzy logic is more efficient in linking the multiple units to a single output and is invaluable supplements to classical hard computing techniques. Therefore, the main purpose of this study is to investigate the relationship between vehicle working parameters and performance characteristics, and to evaluate how fuzzy logic expert system plays an important role in prediction of vehicle performance. Experimental values are taken in the swamp peat terrain for vehicle performance investigation. In this paper, a fuzzy logic expert system model, based on Mamdani approach, is developed to predict the tractive efficiency and power consumption. Verification of the developed fuzzy logic model is carried out through various numerical error criteria. For all parameters, the relative error of predicted values are found to be less than the acceptable limits (10%) and goodness of fit of the predicted values are found to be close to 1.0 as expected and hence shows the good performance of the developed system.     

Terramechanics and its influence on the concepts of tractors, tractor power development, and energy consumption

Through the foundation and work of ISTVS, a forum and a megaphone have been provided to allow an interchange of terramechanics ideas among the Society's members. The important achievements in the science of terramechanics, which have been assisted by the Society's membership, are reviewed.The role of terramechanics in machine design has an effect on vehicle component geometry and selection. As an example, five agricultural tractor types are compared with respect to their tractive performance, based on an analysis of soil properties tire design, and ground pressure distribution. An analysis is also presented concerning traction-slip curves of radial and diagonal tires by accounting for the various componets of traction force and rolling resistance.Tractor development in the U.S.A. and Germany is discussed, together with the factors that have influenced this development since 1950. Consumption of energy in agriculture is analyzed, and the need for conservation of energy through more efficient fuel use, cultivation, and stabilization of energy consumption per worker is developed. The contribution that terramechanics can make to this effort by improving traction efficiences, optimal tractor design, soil cultivation practices, and off-road transportation is identified.     

Differences in tractor performance parameters between single-wheel 4WD and dual-wheel 2WD driving systems

Vertical wheel load and tire pressure are both easily managed parameters which play a significant role in tillage operations for limiting slip which involves energy loss. This aspect to a great extent affects the fuel consumption and the time required for soil tillage. The main focus of this experiment was to determine the effect on the wheels’ slip, the fuel consumption and the field performance of a tractor running in a single-wheel 4WD driving system and in a dual-wheel 2WD driving system, due to the variations in air pressure of the tires as well as in the ballast mass. With no additional mass, the lowest fuel consumption was reached by a tractor with the least air pressure in the tires and running in a dual-wheel 2WD driving system. It was determined that for a stubble cultivation with a medium-power (82.3 kW) tractor running in a dual-wheel 2WD driving system, the hourly fuel consumption was by 1.15 L h⁻¹ (or 7.3%), the fuel consumption per hectare by 0.35 L ha⁻¹ (or 7.9%) and the field performance by 0.05 ha h⁻¹ (or 1.25%) lower compared to a single-wheel 4WD driving system, when driving wheels’ slip for both modes was the same, i.e., at 8–12%.     

Rural road characteristics and vehicle operating costs in developing countries

The primary phase of transportation at the smallholder level, from village to local market, is a particularly important aspect of increasing agricultural production in developing countries. The realistic prediction of vehicle operating costs on the (largely) unsurfaced roads in this sector is a useful input to development planning and a computer program has been developed to produce such predictions from first principles. When compared with survey results obtained by the Transport and Road Research Laboratory in Kenya, it is found that correlation is satisfactorily close. The program can also be used to predict the effects, on the operating costs of various vehicles, of changing road characteristics (gradient, curvature, roughness, rolling resistance and traction). It is found that rolling resistance and road roughness are the factors most likely to influence operating costs, due to their effects on vehicle speeds, fuel consumption and service/repair costs. Small, cheap machines are not necessarily superior to larger vehicles in terms of costs per tonne kilometre and fuel, particularly where the available load is sufficient to allow the larger vehicle to be utilized reasonably fully.     

Torque control strategy for a parallel hydraulic hybrid vehicle

Hydraulic hybrid system is an important branch of hybrid technology, which has the advantage of high power density and the ability to accept the high rates/high frequencies of charging and discharging, therefore hydraulic hybrid technology is well suited for off-road vehicles and heavy-duty trucks. Relatively lower energy density and complicated coordinating operation between two power sources require a special energy control strategy to maximize the fuel saving potential. This paper presents a new configuration of parallel hydraulic hybrid vehicle (PHHV) to improve the braking energy regenerated potential and engine work efficiency. Based on the analysis of optimal energy distribution for the proposed PHHV over a representative urban driving cycle, a fuzzy torque control strategy based on the vehicle load changes is developed to real-time control the energy distribution for the proposed PHHV. Simulation results demonstrate that the proposed PHHV with torque control strategy takes advantage of the high power density and efficiency characteristics of the hydraulic hybrid system, minimizes the disadvantages of low energy density and effectively improves the fuel economy of PHHV.     

Speed advice for power efficient drawbar work

Tractor manufacturers already offer engine - transmission control systems in which the operator decides whether low fuel consumption or high output is the priority and let a control system provide engine and transmission management. Less sophisticated tractors, as well as older equipment, still rely on the operator awareness upon what driving parameters most enhance efficiency. The objective of this study is to analyse the effect of driving parameters, namely forward speed and engine speed on the overall power efficiency. The overall power efficiency of a tractor performing drawbar work is the ratio between the output power at the drawbar and the energy equivalent of the fuel consumed per unity of time. Experimental data obtained from tractor field tests in real farm conditions, within the range of 0.2-0.4 for the vehicle traction ratio (ratio of the drawbar pull to the total weight of the tractor), show that increments of 10-20% on the overall power efficiency can be obtained by throttling down from 2200 min⁻¹ to 1750 min⁻¹ (idle speed). The reduction in ground speed and therefore in the work rate, may be overcome by shifting up the transmission ratio.     

柴油爆炸性能外场实验研究

通过Ø30 mm杀爆燃弹外场炮击实验,模拟车辆、装备油箱被炮火击中后二次爆炸场景,采用高速照相机、红外热成像仪分别记录引爆柴油过程和爆炸火球的温度场,对比评估普通柴油、含水型柴油和抑爆型柴油的爆炸特性。实验结果显示：炮弹射击油箱瞬间,柴油液滴被抛撒出油箱,与空气快速混合形成气溶胶,并在炸药能量作用下引发爆炸,形成爆炸火球;不同类型柴油的爆炸火球均经历3个发展阶段,但其尺寸、扩展速率和表面温度等有较大差别,普通柴油和含水型柴油的火球这3个参数比较接近,都大于抑爆型柴油;含水型柴油的油箱毁伤容积为108.00 dm³,远高于普通柴油的57.65 dm³和抑爆型柴油的38.15 dm³。研究表明,抑爆柴油中的高分子聚合物能起到较好的抑爆作用。

     

Adaptive sliding-mode control for two-wheeled inverted pendulum vehicle based on zero-dynamics theory

The two-wheeled inverted pendulum vehicle yields wide application prospects due to its compact construction, convenient operation, high maneuverability, and low fuel consumption. However, influenced by the underactuated characteristic, it is very difficult to achieve satisfactory control performances besides holding the vehicle body to be stable. In this study, based on the nonlinear dynamic model, the overall system is considered as three subsystems: rotational motion, longitudinal motion, and zero dynamics. Particularly, the tilt angle of the vehicle is treated as zero dynamics where the longitudinal acceleration is taken as the control input. With the control effects, the zero-dynamics subsystem could come up to be stable. Based upon the zero dynamics, the controllers for rotational and longitudinal subsystems are constructed in the following. In addition, the sliding-mode control techniques are used to derive the controllers since their insensitive characteristic to parameter variation and disturbance rejection.     

Numerical study of attack angle characteristics for integrated hypersonic vehicle

The two-dimensional coupled implicit Navier-Stokes equations and standard k-ε viscous models are used to simulate the angle of attack characteristics of an inte- grated hypersonic vehicle with a hark head configuration under three kinds of working conditions： inlet cut-off, engine through-flow, and engine ignition. Influence of each com- ponent on aero-propulsive performance of the vehicle is discussed. It is concluded that the longitudinal static stability of the vehicle is good, and there is enough lift-to-drag ratio to satisfy the flying requirement of the vehicle. At the same time, it is important to change configurations of engine and upper surface of airframe to improve aero-propulsive ~erformance of the vehicle.     

Robust adaptive speed control of uncertain hybrid electric vehicle using electronic throttle control with varying road grade

The design objective of this paper is to apply various control techniques to control the speed of a hybrid electric vehicle (HEV) using an electronic throttle control system (ETCS). The DC servo motor is used for controlling the angular position of the throttle valve. A proportional-integral-derivative (PID), a self-tuning fuzzy PID (STF-PID) controller and a model reference adaptive system (MRAS) with a sliding mode (SM) adaptation mechanism are used for controlling the speed of the nonlinear vehicle. The integral error performance indices (IEPI) such as the integral of the absolute error (IAE), the integral of the square of error (ISE) and the time domain performance specifications such as overshoot (OS), settling time (ST) and rise time (RT) are taken into consideration for the performance analysis of HEV. The robust H_∞ controller using mixed sensitivity approach is designed and implemented for the linearized HEV. The robust stability of uncertain HEV with H_∞ controller using Kharitonov’s theorem is analyzed, and the stability margin of the linearized vehicle system is determined. These control techniques are developed to achieve the robust performance of the throttle controlled HEV with the target to achieve a wide range of speed, fuel economy, reduced pollution and improved efficiency.     

Di Diesel Engine with Variable Geometry Turbocharger (VGT): A Model Based Boost Pressure Control Strategy

The use of a variable geometry turbocharger (VGT) is a very efficienttechnology to improve performance of passenger car direct injection (DI)Diesel engines. In order to take full advantage of the potential of VGT,without penalty on fuel consumption and driveability, electronic control ofboost pressure is desirable. Standard control techniques (i.e.Proportional-Integral) do not assure a reliable VGT behaviour. This paperdescribes a new boost pressure control strategy developed to improve PItechnique, and based on a simplified modelling of VGT operation. Severaltests were carried out on engines to point out which physical quantitiesdirectly influence VGT dynamics, and to find out VGT operation modes (OMs).Simplified models for each OM were developed and model parameters wereidentified. Experimental tests provided a basis to design a control strategyable to meet general performance requirements. Since two different OMs wererecovered, two separate governors were developed, each active under certainconditions. A switching logic was created to manage transitions between thetwo governors. Finally, the new control strategy was validated on the enginewith good results.     

Multi-wheel drive vehicle energy/fuel efficiency and traction performance: Objective function analysis

This paper presents the results of a mathematical analysis, computational results, and experimental data related to the multi-wheel drive vehicle energy/fuel efficiency and vehicle tractive and velocity operational properties evaluation.Power distributions to the drive wheels provided by vehicle driveline systems are the major factors in pre-determining the vehicle energy/fuel efficiency. The objective function mathematical analysis has led to some important practical recommendations for designing better driveline systems. Generally, the maximum efficiency of a vehicle is provided by wheel power distributions that are under unequal slips of the vehicle tires. However, optimum driveline systems are expected to be designed in a way that leads to the same slips for all the tires.The mathematical analysis, computational results, and experimental data are presented in a combination with the results of a century-long scientific discussion on the problem under consideration. Details are in the paper.