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Technical Paper

Vehicle Braking System Calculation and Simulation Software Platform

The brake performance is one of the most important performances in the automotive active safety, and it is the main measure of automotive active safety. Thus, to develop a platform for the braking system is quite significant. Based on the object-oriented technology, the platform for braking system is developed by making use of Visual C++ 6.0 development tool. By using the VC++ development tool and doing secondary development on other softwares, the software possesses powerful features, such as brake plan selection, performance calculation, parametric modeling, finite element analysis and kinematics simulation, etc. An initial brake system can be designed, calculated and analyzed all in one. The living instance shows that the platform has friendly user interfaces, powerful functions and it can improve the precision and efficiency of brake design. The platform has been of great applied value and can also positively promote the design automation of vehicle's braking system.
Technical Paper

Nonlinear System Identification of Road Simulation Platform

On road simulation, both the traditional iterative method based on frequency response function (FRF) and adaptive control method based on the CARMA model are realized by using linear model to identify the target test system. However the real test system is very complicated because of various nonlinear factors. Linear models approximately describe the system only in a small range. Therefore, system simulation methods can not be used to validate the developed control algorithm and the uncertainty of test accordingly increases. As mentioned above, this paper presents a model to identify the nonlinear test system using NARMA dynamic neural network and discusses how to make the model parameters in detail. Using the test input-output series data, this network was trained by Levenberg-Marquardt method. Results of verification simulation show the validation of the nonlinear model.
Technical Paper

The Combined Braking Energy Management Strategy to Maximize Energy Recovery

Eddy current retarder (ECR) shares a large market of auxiliary brakes in China, but shortcomings of the short continuous braking time and the high additional energy consumption are also obvious. The propose of combined braking partakes the braking torque of ECR. However, the existed serial-parallel braking strategy could hardly balance well the relationship between the braking stability and the energy recovery efficiency. This research puts forward an energy management strategy of combined braking system which aims to maximize energy recovery while ensure the brake stability. The motor speed, the braking request and the state of charge (SoC) of the storage module are analyzed synthetically to calculate the reasonable braking torque distribution proportion. And the recovered energy is priority for using in the braking unit to reduce the additional energy consumption in this strategy.
Technical Paper

Simulation Analysis on Controllability of Hydraulic Electrical Energy Regenerative Semi-Active Suspension

A vehicular hydraulic electrical energy regenerative semi-active suspension(HEERSS) was presented, and its working principle and performance were analyzed. Firstly, configuration and working principle of the HEERSS were described; Secondly, kinetic equation of HEERSS was deduced, and a skyhook controller was designed for HEERSS. The traditional skyhook control strategy should be changed for the characteristic of HEERSS, because the damping force during extension stroke could be controlled, but not in compression stroke. Thirdly, the performance of HEERSS was compared with passive suspension(PS), traditional semi-active suspension(TSS). The simulation results indicated that the performance of HEERSS would be compromise between TSS and PS, but the HEERSS could harvest vibration energy which was advanced than TSS and PS.
Technical Paper

Effect of Circumferential Magnetic Field on Braking Performance of a Direct Vane Magnetorheological Fluid Retarder

The hydraulic retarder used in commercial vehicles can provide hydraulic damping to generate braking torque, reducing the pressure of the braking system on the slope section and increasing the safety. In this paper, the magnetorheological fluid with fast magnetic field reflection characteristics is used to increase the response speed of the hydraulic retarder, which can effectively reduce the response time of the hydraulic retarder. In this paper, the influence of the change of circumferential magnetic field on the braking torque of the magnetorheological fluid retarder is studied.
Technical Paper

Modeling, Simulation and Experimental Analysis of Brake Pedal Feel for Passenger Car

Brake pedal feel plays an important role in the driver's comprehensive subjective feeling when braking, which directly affects the active safety and riding comfort of passenger car. A systematical mathematical model of the vehicle brake system is built in according with the structure and system characteristics of hydraulic servo brake system. A complete hydraulic servo brake system simulation model composed of brake pedal, vacuum booster, brake master cylinder, brake pipe, brake wheel cylinders, brake calipers is established in AMESim. The effects of rubber reaction plate stiffness, rubber valve opening, brake master cylinder piston, brake caliper, brake pipe deformation and friction liner deformation on brake pedal feel are considered in this model. The accuracy of this model is verified by real road vehicle tests under static and dynamic two different conditions.
Technical Paper

Airflow and Fuel Spray Interaction in a Gasoline DI Engine

Two optical techniques together with a CFD simulation have been used to study the interaction of intake airflow with the injected fuel spray in a motored direct injection gasoline engine. The combustion chamber was of a pent-roof construction with the side-mounted injector located low down between the inlet valves injecting at a 54° angle to the cylinder axis. The two-dimensional piston bowl shape allowed optical access for the Mie scatter technique to be used to investigate the liquid fuel behaviour in the central axial plane of the cylinder lying midway between the two inlet valves and passing through the centre line of the injector nozzle. A second set of images was obtained using backlighting, this time looking through the glass cylinder liner directly towards the injector. The in-cylinder simulation was run using the VECTIS software. Measurements and simulations were conducted for a range of early SOI timings between 20° and 80° ATDC.
Technical Paper

Application of Optical Techniques to the Study of Mixture Preparation in Direct Injection Gasoline Engines and Validation of a CFD Model

The performance of a direct injection gasoline engine (G-DI) is highly dependent on the quality of the air-fuel mixture preparation. This is of particular importance when operating at a stratified charge condition, where the ideal mixture distribution would be a stoichiometric region around the spark plug, surrounded by air. To achieve this ideal situation over a wide range of speeds and loads is extremely difficult, requiring an understanding of the fuel spray, the in-cylinder air motion and their interactions. This paper presents the results of Phase Doppler Anemometry (PDA) and Laser Induced Fluorescence (LIF) measurements made both within an optically accessed direct injection gasoline engine and under atmospheric conditions. The experimental results are compared with those of a VECTIS Computational Fluid Dynamics (CFD) simulation of the same engine.
Technical Paper

CFD Simulation of DI Diesel Truck Engine Combustion Using VECTIS

CFD simulations have been conducted to investigate the combustion in a direct-inject (DI) diesel engine using the Ricardo engine CFD program VECTIS and the Ricardo Two-Zone Flamelet (RTZF) combustion model. The simulation program covers full load and part load operating conditions, each including 6 to 7 cases forming an injection timing swing. CFD simulation results are compared against engine tests for the in-cylinder pressures and NOx emissions. The comparison shows that the RTZF combustion model performs well in all cases studied with no tuning of model coefficients necessary. The detailed time history of spray, fuel distribution and flame development obtained from the CFD simulation provides useful information towards gaining a better understanding of the features of combustion in DI diesel engines.
Technical Paper

Multiple-Cylinder Diesel Engine CFD Simulation Using VECTIS

This paper presents the CFD simulation performed on a 4-cylinder in-line Diesel engine using Ricardo's engine focused commercial CFD code VECTIS. Simulation run through multiple cycles and covered processes of intake, compression, spray, combustion and exhaust. The cyclically converged solution is compare to the engine test data for cylinder pressure, charge distribution and EGR distribution, etc… Technical issues concerning multiple-cylinder analysis are discussed.
Technical Paper

Fuzzy Control of Semi-active Air Suspension for Cab Based on Genetic Algorithms

Semi-active suspension has been widely applied in commercial vehicle suspension in order to get good riding comfortableness. Fuzzy logic control (FLC) has been widely applied in the field of kinetic control because control rule of FLC is easy to understand. But the gain of fuzzy rules and adjustment of membership functions usually depend on experts' experiences and repeated experiments, thus the fuzzy rules and membership functions has strong subjectivity, also are easily affected by environment of experiments, so the main problem of fuzzy logic controller design is selection and optimization of fuzzy rules and membership functions. Genetic Algorithms (GA) is the algorithm that searches the optimal solution through simulating natural evolutionary process and is one of the evolution algorithms which have most extensive impact.
Technical Paper

Driving Path Planning System under Vehicular Active Safety Constraint

Path planning system, which is one of driver assistance systems, can calculate the driving paths and estimate the driving time through the road information provided by information source. Traditional path planning systems calculate the driving paths through Dijsktra's algorithm or A* algorithm but only consider the road information from electronic maps. It is not safe enough for operating vehicles because of the insufficient information of vehicle performance as well as the driver's willingness. This study is based on the Dijsktra's algorithm, which comprehensively considered vehicular active safety constraints such as road information, vehicle performance and the driver's willingness to optimize the Dijsktra's algorithm. Then the path planning system can calculate the optimal driving paths that would satisfy the safety requirement of the vehicle. This study used LabVIEW as a visual host computer and MATLAB to calculate dynamic property of the vehicle.
Technical Paper

Co-simulation Based Hydraulic Retarder Braking Control System

Hydraulic retarder has been widely applied on military vehicles and heavy commercial vehicles because of it could provide great brake torque and has lasting working time [1]. In order to reduce driver's frequent actions in braking process and prevent hydraulic retarder system from overheating, it is need to apply constant braking torque control, this control target has a strict requirement to hydraulic control system design. Many parameters often require repeated test to determine, which increases the R&D cost and extends the research cycle. This paper tries to find a time-efficient research method of hydraulic retarder control system through studying on a heavy military vehicle hydraulic retarder system. Hydraulic retarder model is set up through test data. The hydraulic control system is built based on AMESim. Controller model is set up based on PID control. The whole vehicle brake model is built based on MATLAB/Simulink.
Technical Paper

Research on Road Simulator with Iterative Learning Control

Road simulation experiment in laboratory is a most important method to enhance the design quality of vehicle products. Presently, two main control techniques for road simulation—remote parameter control (RPC) and minimum variance adaptive control—are both defective: the former becomes an open-loop control after generating the drive signals, however the latter is essentially a kind of gradual control. To realize the closed-loop control and increase the control quality, this article brings forward a PID open-closed loop control method. Firstly taking the original road simulator as a group to identify, a nonlinear autoregressive moving average (NARMA) model was built with the dynamic neural network. Subsequently, this plant model was used to build the open-closed loop control system mentioned above. In the closed-loop a discrete PID controller was introduced to stabilize the system, while a P-type iterative learning control (ILC) was adopted to increase the control quality.
Technical Paper

Strength Analysis and Modal Analysis of Hydraulic Retarder

Hydraulic retarder is one of main auxiliary braking devices of the vehicle. When the vehicle is braking, a great pressure from high-speed fluid is received by hydraulic retarder blades. It is difficult to predict rational hydraulic retarder strength, owing to the complexity of the internal flow of oil. An optimal calculation way of hydraulic retarder strength is proposed based on CFD and FEA, concluding a reasonable result. The 3-D model of hydraulic retarder is built in the general CAD software. The model of fluid passage is extracted, according to the condition when the whole flow passage is filled with oil, and imported to CFD software. The inner flow field of hydraulic retarder is analyzed and the hydraulic surface pressure distribution of the hydraulic retarder blade is obtained at the highest rotary speed of turbine wheel.
Technical Paper

Multidisciplinary Design Optimization of BEV Body Structure

Blade Electric Vehicle (BEV) with a light body plays an important role in saving the energy and reducing the exhaust emission. However, reducing the body weight need to meet the heterogeneous attributes such as structural, safety and NVH (Noise, Vibration and Harshness) performance. With the rapid development of finite element (FE) analysis technology, simulation analysis is widely used for researching the complex engineering design problem. Multidisciplinary Design Optimization (MDO) of a BEV body is a challenging but meaningful task in the automotive lightweight. In present research, the MDO is introduced to optimize a BEV Body-in-White (BIW).
Journal Article

Boiling Coolant Vapor Fraction Analysis for Cooling the Hydraulic Retarder

The hydraulic retarder is the most stabilized auxiliary braking system [1-2] of heavy-duty vehicles. When the hydraulic retarder is working during auxiliary braking, all of the braking energy is transferred into the thermal energy of the transmission medium of the working wheel. Theoretically, the residual heat-sinking capability of the engine could be used to cool down the transmission medium of the hydraulic retarder, in order to ensure the proper functioning of the hydraulic retarder. Never the less, the hydraulic retarder is always placed at the tailing head of the gearbox, far from the engine, long cooling circuits, which increases the risky leakage risk of the transmission medium. What's more, the development trend of heavy load and high speed vehicle directs the significant increase in the thermal load of the hydraulic retarder, which even higher than the engine power.
Journal Article

Fuzzy-PID Speed Control of Diesel Engine Based on Load Estimation

In order to improve the anti-disturbance performance of engine-load and the effect on speed control for the diesel engine, the paper presents the fuzzy-PID speed control strategy in the architecture of torque-based control. The engine-load estimation algorithm is designed based on the mean-value-model and crankshaft dynamics model, and the estimation precision is validated by engine test in both steady and dynamic conditions. Through the experiment verification of the diesel engine, the fuzzy-PID control strategy based on load estimation can significantly improve the anti-disturbance performance of engine-load in the speed control.
Technical Paper

Four-Wheel Independently Driven In-Wheel Motors Electric Vehicle AFS and DYC Integrated Control

For four-wheel independently driven in-wheel motors electric vehicle, an integrated control algorithm of active front steering and direct yaw moment control based on model predictive control is proposed in this paper. The algorithm adopts hierarchical integrated control structure. The model predictive controller is designed and the driving force allocation is controlled by rules. The algorithm is verified by the simulation at last. The results show that the algorithm can make the vehicle track the desired response effectively and enhance the vehicle stability in critical running condition.
Technical Paper

Differential Speed Steering Control for Four-Wheel Distributed Electric Vehicle

In order to perform differential control instead of the mechanical differential and improve the steering performance of distributed electric vehicles, a two-level differential speed steering control strategy is proposed. Firstly, an upper-layer controller to track the yaw rate is designed based on PID feedback and 3-D lookup table model, which could shorten the response time and reduce the impact of model parameters mismatch. Then, in order to improve the robustness to external disturbances and parameter uncertainties, a lower-layer controller to track the wheel speed is proposed based on integral sliding mode control. Moreover, three simulations are conducted to validate the proposed strategy. The first simulation results indicate that the driving torques of the inner and outer wheels are distributed properly to avoid wheel slip. In the second simulation, when the conventional steering system fails, the proposed control strategy could avoid vehicle losing steering function.