Search Results

An energy management strategy is needed to optimally allocate the driver's power demands to different power sources in the fuel cell hybrid vehicles. The driver's power demand is modelled as a Markov process in which the transition probabilities are estimated on the basis of the observed sample paths. The Markov Decision Process (MDP) theory is applied to design a stochastic energy management strategy for fuel cell hybrid vehicles. This obtained control strategy was then tested on a real time simulation platform of the fuel cell hybrid vehicles. In comparison to the other 3 strategies, the constant bus voltage strategy, the static optimization strategy and the dynamic programming strategy, simulations in the Beijing bus driving cycle demonstrate that the obtained stochastic energy management strategy can achieve better performance in fuel economy in the same demand of dynamic.

The ethanol has potential to be a renewable alternative fuel for internal combustion engines and contributes to lower global CO2 emission. In this study, vegetable methyl ester is added in the ethanol-diesel fuel to prevent separation of the ethanol from diesel, thus the ethanol blend ratio can be set up to 30% in volume. This work pays more attention on its spray, effects of the ethanol percentage on the detailed PM components. To investigate the spray behavior of ethanol, diesel and their blends, experiments in a constant volume chamber were carried out combining numerical simulation. Properties of the ethanol-diesel blended fuels were obtained through some measurements and empirical calculations. The breakup sub-model, Wave-KH model considering the blend fuel properties were adopted in an engine simulation code KIVA-3V. The simulation had a good agreement with experiments.

The large amount of controllable fuel injection parameters of Diesel engine equipped with high pressure common-rail fuel injection system makes the control of combustion more flexible, and also makes the workload of calibration and optimization much heavier. For higher efficiency, model-based approaches are presented and researched. This contribution presents a new method for modeling which is constituted by Neural Network and Adaptive Network-based Fussy Inference System (ANFIS). The experiment is carried out on a 6-cylinder common rail diesel engine. The analysis and experiment show that effective modeling can be achieved using this method.

The internal combustion engine and motor should be controlled coordinately to meet the demand of smooth power transfer and good drivability especially during transient conditions for parallel hybrid powertrain system. This paper presents the essential technology of how to estimate the engine torque by the measurement and processing of instantaneous crankshaft speed. One multi-injection gasoline engine and one turbocharged diesel engine are selected to manifest the algorithm of engine torque estimation and the experiments show fairly good results for both engines. Consequently an engine torque sensor can be easily calibrated and applied to feedback engine torque in coordinating control.

Battery is a vital part of a fuel cell hybrid vehicle, and also the most difficult part to model due to its nonlinearity. Therefore, This paper presents an integrated software-hardware solution to simulate the fuel cell vehicle power train more accurately based on battery-in-the-loop, with the aid of RT-LAB™. Moreover, the average modeling technique is used together with RT-LAB's distributed cluster technology to realize real-time simulation of the Field-Oriented Controlled induction motor drive, and the Boost DC/DC converter. As a result, a virtual test bed, which is very similar to actual power train, is set up. Finally, on this test bed some tests are performed to verify the existing battery model and soc estimation method, and to give more accurate fuel consumption results.

This paper presents a preliminary design and analysis of an optimal energy management and control system for a power-split hybrid electric vehicle (HEV) using hybrid dynamical control system theory and design tools. The hybrid dynamical system theory is applied to formulate HEV powertrain dynamical system in which the interactions of discrete and continuous dynamics are involved. The Sequential Quadratic Programming (SQP) method is applied to optimize power distribution. An improved dynamic programming method is employed to determine the optimal power distribution and the vehicle operating mode transitions.

It's important to monitor the longitudinal friction at the tire/road interface for automotive dynamic control systems like ABS and ASR. Of all the tire friction models the empirical model provides a good illustration on longitudinal wheel forces. An improved exponential friction model based on vehicle driving states was proposed in this paper, the model can monitor the friction characteristics between the tire and road surface for longitudinal braking. Its validity was proven using experiments and comparison with the Pacejka Magic Formula (MF) model and others.

Hydraulic Engine Mount (HEM) is now widely used as a highly effective vibration isolator in automotive powertrain. A lumped parameter model is a traditional model for modeling the dynamic characteristics of HEM, in which the system parameters are usually obtained by experiments. In this paper, Computational Fluid Dynamics (CFD) method and nonlinear Finite Element Analysis (FEA) are used to determine the system parameters. A Fluid Structure Interaction (FSI) FEA technique is used to estimate the parameters of volumetric compliances, equivalent piston area, inertia and resistance of the fluid in the inertia track and decoupler of a HEM. A nonlinear FEA method is applied to determine the dynamic stiffness of rubber spring of the HEM. The system parameters predicated by FEA are compared favorably with experimental data and/or analytical solutions.

A mathematical model of vehicle fuel cell system thermal management has been developed to investigate the effects of various design and operating conditions on the thermal management and to understand the underlying mechanism. The fuel cell stack structure is represented by a lumped thermal mass model, which has the heat transfer and pressure loss characteristics of the fuel cell stack structure. The whole thermal management system is discretized into many volumes, where each flowspit is represented by a single volume, and every pipe is divided into one or more volumes. These volumes are connected by boundaries. The model is solved numerically to analyze thermal management system performance. The effects of coolant flow rates and air flow rates on the system thermal performance, the stack thermal capacity on the transient thermal performance have been investigated in detail.

A hybrid unstructured Navier-Stokes method is presented for the simulation of the incompressible turbulent flows around vehicle bodies. The hybrid grid system is composed of a structured or semistructured grid for the near-wall viscous region, and an unstructured grid for the remainder of the computational domain. By using prismatic cells, the number of cells in the boundary-layer region becomes approximately one-third of the tetrahedral grid. And the laminated grid rather than the tetrahedral grid is more suitable in the boundary-layer region for accurately computing the viscous terms. The incompressible Navier-Stokes equations are solved on the hybrid grid by a cell-vertex, central differencing finite volume method. The numerical accuracy of the present method is discussed by comparing with the experimental data for the cases of flows around a car model at different ground clearances.

Hydraulically damped rubber engine mounts (HDM) are an effective means of providing sufficient isolation from engine vibration while also providing significant damping to control the rigid body motions of the engine during normal driving conditions. This results in a system which exhibits a high degree of non-linearity in terms of both frequency and amplitude. The numerical simulation of vibration isolation characteristics of HDM is difficult due to the fluid-structure interaction between the main supporting rubber and fluid in chambers, the nonlinear material properties, the large deformation of rubber parts, structure contact problems among the inner parts, and the turbulent flow in the inertia track. In this paper an integrated numerical simulation analysis based on structural FEM and a lumped-parameter model of HDM is carried out.

As important members of the STATCOM (Static Synchronous Compensator), the passive elements play an indispensable role in the transient and steady state performance of STATCOM. The harmonics resonant phenomena have been pointed out in some papers. However from the engineering design point of view, a more detailed investigation should be conducted to give an insight into the effects of passive parameter selection on the system performance. Based on the experience in developing STATCOM, the authors proposed a modified mathematical model in a per-unit system as the base of parameter evaluation. With the proposed model, the authors analyze the influence of the per-unit passive parameters on the performance of STATCOM systematically. Simplified algebraic expressions for the magnitudes of the harmonic current as well as the dc voltage regarding the particular harmonics are derived, which can be used as an indication of the preference for the passive elements.

Use of a hydraulic lash adjuster (HLA) in the valve train has some problems as well as several advantages. One of the problems is less stiffness of valve train, which may be further reduced when aeration of the oil in the oil circuit occurs. The much lower stiffness will lead to malfunction, noise and damage with the valve train. So the aeration of oil in HLA high pressure chamber must be considered in modeling and simulation of the valve train. Since air dissolved capacity in the oil varies with pressure, aeration (undissolved air content) in the high pressure chamber is different from that in the oil circuit. So far, only the air content in the oil circuit has been measured, and few reports have been found on determining the aeration in HLA of an operating valve train. Based on knowledge that HLA collapse is caused by compressibility and leakage of oil, a method of determining the aeration of the oil in the high pressure chamber is introduced.

A quasi-dimensional multi-zone model for diesel spray combustion has been developed. The model contains most of the physical processes of diesel spray combustion, and is simplified and economical. The zone formation is based on the fuel injection parameters. For the wall jet penetration velocity, a new equation is used based on the effect of the impinging free jet on the wall jet. For the fuel evaporation, an approximate solution of the instantaneous variations of droplet diameter is given in the simple algebraic equations based on the individual effect of the evaporation and the heat transfer from ambient gas. The soot emission sub-model calculates the soot concentration. This model has been applied for a direct injection diesel engine. The calculated results have shown a reasonable agreement with the experimental results. A parametric study has been carried out.

Injection rate control is considered as an effective way to optimize diesel combustion process, decrease emission and improve fuel economy. There are many injection rate shaping devices, but most of them still suffer from structure complexity and parameter sensitivity which limit their effectiveness and practicality. A new initial injection rate control method in solenoid-controlled diesel injection systems is introduced in this paper. The basic idea of this method is to maintain a small spill passage between plunger chamber and inlet port during initial injection period. The initial injection rate can be regulated by changing the closing timing of the solenoid-controlled spill valve. This method has the advantages of simple construction, flexible adjustment and stable performance. Computer aided analysis and design based on a simulation program of the system is conducted to compare and select the sizes of the small spill passage according to their effect on injection characteristics.

At first, the dynamic electromagnetic characteristics of a pulsed solenoid valve is analyzed by experiments. The fast valve response is obtained by material modifications. Then, the intelligent solenoid driving method is discussed. The new techniques of the “active” PWM and the “d2i/dt2” detection are developed for feedback control of the solenoid holding current and the valve closure timing. Finally, the control and diagnosis method for the valve closure duration is investigated. A sensing mechanism utilizing momentary camshaft speed fluctuations of fuel injection pump is presented, which provides the basis for feedback control and diagnosis of the valve closure duration and diesel fuel injection process.