Virtual product development for an automotive universal joint

Constant velocity universal joints play a very important role in automotive drivelines. The traditional development method, based on a physical prototype and experimenting, is time consuming and costly. This test-based method does not easily identify rational design clues. Therefore, a virtual product development method, which is based on dynamics modeling and simulation, is necessary. Virtual prototyping for a universal joint has been developed using the simulation software package MSC.ADAMS. Dynamics simulation has been performed to predict and evaluate joint behaviors. This virtual product development method has been implemented by the WanXiang Group Co., which is one of the most famous Chinese automotive component manufacturers.     

Objectification of on-center handling characteristics based on spring-mass-damper system

As one of the major handling performance factors of vehicles and tires, on-center handling is very important at high speeds where safety and refinement are major concerns for the driver. In this paper, the steering wheel torque and vehicle response characteristics that play an important role in on-center handling performance were quantified using a spring-mass-damper (SMD) system. Using this system, the characteristics of steering wheel torque and vehicle response could be objectified with SMD parameters such as those for the spring and damping. Experimental objective tests were performed by considering the process by which the on-center handling is evaluated subjectively, and the SMD parameters were extracted from the measurement data. From a statistical analysis of the subjective and SMD parameters for several vehicles and professional drivers, it was found that the subjective assessment of on-center handling could be successfully explained using the suggested parameters.     

Neural-empirical tyre model based on recursive lazy learning under combined longitudinal and lateral slip conditions

The behaviour of the tyre plays an important role in the vehicle handling. An accurate tyre model that estimates these forces and moments it is highly essential for the studies of vehicle behaviour. For the last ten years neural networks have attracted a great deal of attention in vehicle dynamics and control. Neural networks have been effectively applied to model complex systems due to their good learning capability. In this paper a recursive lazy learning method based on neural networks is considered to model the tyre characteristics under combined braking and cornering. The proposed method is validated by comparison with experimental obtained responses. Results show the estimated model correlates very well with the data obtained experimentally. Moreover, the neural model proposed allows to include the asymetric tyre behaviour in the tyre model without difficulty.     

Comparative study between Korea and UK: relationship between driving style and real-world fuel consumption

It is known that differences in driving styles have a significant impact on fuel efficiency and driving styles are affected by various factors such as driver characteristics, street environment, traffic situation, vehicle performance, and weather conditions. However, existing knowledge about the relationship between driving style and fuel consumption is limited. Thus, the aim of this study was to analyze the relationship beteen driving style and fuel consumption. The analysis presented in this paper used data from three on-road experiments were conducted independently in two different countries, i.e. South Korea and the United Kingdom. In this study, 91 participants, consisting 44 UK drivers and 47 Korean drivers, were asked to drive approximately 28 km of UK road and 21 km of Korean road, respectively. Driving data, including real-time fuel consumption, vehicle speed, and acceleration pedal usage were collected. The results suggested that driving styles including average vehicle speed and average throttle position were highly correlated with the real-world fuel consumption, and the cultural factors, e.g. road environment, traffic design, and driver’s characteristics affected the driving styles and, consequently, fuel efficiency.     

Optimal power distribution of front and rear motors for minimizing energy consumption of 4-wheel-drive electric vehicles

In this paper, the optimal power distribution of the front and rear motors for minimizing energy consumption of a 4WD EV is investigated. An optimal power distribution control is developed based on the mathematical energy consumption model of an EV. The objective function is defined while ignoring time. And, the time effect is applied by considering the objective function for every single driving point which consists of the vehicle driving force and velocity. From the optimization problem, the optimal torque distribution maps of the front and rear motors can be obtained for all vehicle driving force and velocity ranges. These maps can be expressed using a 3-dimensional map. If the vehicle driving force and velocity are determined, the optimal front and rear motor torques can be determined using these maps. These maps can distribute the front and rear motor torques for the entire velocity range. Thus, these maps can perform the optimal power (torque times speed) distribution of the front and rear motors for minimizing the energy consumption of the 4WD EV. The performance of the optimal power distribution is evaluated by comparing the energy consumption to that of simple power distribution control. For obtaining the energy consumption, a vehicle driving simulation is performed. For the simulation, the driving cycle is required, and the NEDC (New European Driving Cycle) is used. From the simulation results, it is found that the energy consumption of simple power distribution is 4.8 % larger than the optimal one. Thus, the optimal power distribution can minimize the 4WD EV energy consumption as the optimization objective function.     

Application of rack type motor driven power steering control system for heavy vehicles

The Electric Power Steering (EPS) or Motor Driven Power Steering (MDPS) mechanism proves to be a bright prospect among passenger vehicles ensuring better vehicle safety and fuel economy. The car manufacturers are focusing on the production of Rack type EPS system (REPS). This paper describes the development of concurrent simulation technique using TruckSim and control strategy for analysing RMDPS control system with a dynamic vehicle system. A full Truck vehicle model interacting with RMDPS control algorithm was concurrently simulated on a sinusoidal steering input. The dynamic responses of vehicle chassis and steering system resulting were evaluated and compared with proving ground experimental data. The comparisons show reasonable agreement on steering wheel torque, lateral acceleration and yaw rate. This concurrent simulation research leads the possibility of RMDPS performance evaluation of Truck and Semi-bonnet cars.     

Effect of tumble-home on roof strength of a vehicle

This study reports on the effect of vehicle tumble-home (side body inclination) on roof strength. The steep inclination of the side body of a vehicle increases its roof strength. Comprehensive analysis of the impact of high roof strength driven by the steep inclination on dynamic roof strength in rollover is described. Here, we have developed a numerical model using the ADAMS, which is capable of characterizing both of the static and the dynamic roof strength. According to the FMVSS 216 protocol, we achieve the strength to weight ratio (SWR; static roof strength) by applying loading plates to the roof of a vehicle. The Controlled Rollover Impact System (CRIS) allows us to quantitatively characterize the displacements of the top end of A-pillar and B-pillar, thus determining the dynamic roof strength by comparing the results. We demonstrated that the roof intrusion was one of the most critical causes which lead to injuries of occupants fastening seat belts. Our analysis revealed that the increase of the side body inclination of vehicles enhanced the static roof strength whereas it could not reduce the roof displacement (intrusion) in the dynamic rollover.     

Loosening analysis for fastening screw of automotive door trim parts

While a screw is a fastening element that can tighten the two parts at low cost, the loosening of the screw is generated due to external forces such as repetitive load, vibration, and thermal stress. This phenomenon decreases the initial clamping force, and this can be a serious problem to the safety of the product. However, while fastening parts are handled through experiment and experience, there is a lack of research on the screw loosening of plastic fastening parts. For example, vehicles have various fastening parts. Among the fastening elements, screws are typically used for tightening parts of the vehicle door trim. Vehicle interior materials are mainly composed of plastic parts. Especially, the temperature of the vehicle interior changes from a sub-zero temperature to 100 degrees (°C) due to solar radiation. Unlike metals, plastic materials are commonly susceptible to the environment. In this study, the fastening screw of automotive door trim parts is selected. First, a screw loosening mechanism is implemented through Computer Aided Engineering (CAE) analysis and the influences of degradation are then analyzed. Secondly, the selecting method of clamping force is suggested through the analysis result of reduction according to the tightening torque.     

Effect of radial interference on torque capacity of press- and shrink-fit gears

Some gears in an automobile transmission have to be mounted by being press-fitted on a shaft instead of splines. The torque capacity of the press-fitted gear will be proportional to the radial interference. The excessive interference, however, will increase the gear radial deformation. In this paper, the press- and shrink-fit and the subsequent torque capacity test were investigated by finite element analysis, theoretically and experimentally. The static and dynamic coefficient of friction were determined.     

Automotive window seal design considering external aerodynamic load and surrogate constraint modeling

Installed between metallic DIW (Door in White) panel and nonmetallic door glass, automotive window seals has great influence on customers’ perception of NVH (Noise-Vibration-Harshness) performance. Recently, aerodynamic effect on ride comfort attracts increasing research interest. The external load causes unsteady pressure on glass, which is finally transferred to window seals and leads to complicated vibration and increases interior noise level. However, non-linearities of hyper-elastic material, rubber-glass contact and large deformation behavior make the construction of window seals constraint model much more difficult, thus impeding further analysis and optimization. A new window seal design method is proposed featuring in considering aerodynamics-induced load and nonlinear constraint. Firstly, by SST ? k ? ε (Shear Stress Transport) turbulence model, external flow field of full-scale automotive is established by solving three-dimensional, steady and uncompressible Navier-Stokes equation. With re-exploited mapping algorithm, the overall aerodynamic pressure is extracted and matched to local window as external loads for seals, thus taking into account high speed fluid-structure interaction. Secondly, based on functional equivalence and mathematical fitting, new surrogate constraint model is presented. The unitedseal CLD (Compression Load Deflection) curve is synthesized after translations and transformations from two semi-seal CLD experimental measurements of inner and outer lips. It is then fit to complex exponential function, making seal constraint equivalent to a surrogate elastic constraint with variable stiffness. Experiment is performed to verify the constraint surrogation effectiveness. Finally, case study of window seal design under high speed is investigated. After seal optimization based on the new method, windows seals’ maximal displacements have decreased. The improved seal-glass fitting status shows better NVH quality of window seal in high-speed condition.