Design of active suspension and electronic stability program for rollover prevention

This paper presents a method for the design of a controller for rollover prevention using active suspension and an electronic stability program (ESP). Active suspension is designed with linear quadratic static output feedback control methodology to attenuate the effect of lateral acceleration on the roll angle and suspension stroke via control of the suspension stroke and tire deflection of the vehicle. However, this approach has a drawback in the loss of maneuverability because the active suspension for rollover prevention produces in vehicles an extreme over-steer characteristic. To overcome this drawback of the active suspension based method, ESP is designed. Through simulations, the proposed method is shown to be effective in preventing rollover.     

Processing and fiber content effects on the machinability of compression moulded random direction short GFRP composites

The random direction short Glass Fiber Reinforced Plastics (GFRP) have been prepared by two compression moulding processes, namely the Preform and Sheet Moulding Compound (SMC) processes. Cutting force analysis and surface characterization are conducted on the random direction short GFRPs with varying fiber contents (25∼40%). Edge trimming experiments are preformed using carbide inserts with varing the depth of cut and cutting speed. Machining characteristics of the Preform and SMC processed random direction short GFRPs are evaluated in terms of cutting forces, surface quality, and tool wear. It is found that composite primary processing and fiber contents are major contributing factors influencing the cutting force magnitudes and surface textures. The SMC composites show better surface finish over the Preform composites due to less delamination and fiber pullouts. Moreover, matrix damage and fiber protrusions at the machined edge are reduced by increasing fiber content in the random direction short GFRP composites.     

Development of an on-line model to predict the in-cylinder residual gas fraction by using the measured intake/exhaust and cylinder pressures

The in-cylinder RGF (residual gas fraction) of internal combustion engines for new combustion concepts, such as CAI (controlled auto ignition) or HCCI (homogenous charged compression ignition), is a major parameter that affects the combustion characteristics. Thus, measurement or prediction of the cycle-by-cycle RGF and investigation into the relation between the RGF and the combustion phenomena are critical issues. However, on-line prediction of the cycle-by-cycle RGF during engine testing is not always practical due to the requirement of expensive, fast response exhaust-gas analyzers and/or theoretical models that are just too slow for application. In this study, an on-line model that can predict the RGF of each engine cycle and cylinder during the experiment in the test cell has been developed. This enhanced model can predict the in-cylinder charge conditions of each engine cycle during the test in three seconds by using the measured dynamic pressures of the intake, exhaust, and cylinder as the boundary conditions. A Fortran77 code was generated to solve the 1-D MOC (method of characteristics). This code was linked to Labview DAQ as a form of DLL (dynamic link library) to obtain three boundary pressures for each cycle. The model was verified at various speeds and valve timings under the CAI mode by comparing the results with those of the commercial code, GT-Power.     

Analysis of neck fractures from frontal collisions at low speeds

Neck fracture is a major cause of death in traffic accidents. This pattern of injury normally occurs in a frontal collision or overturn of a vehicle. This study investigates the case of a neck fracture from a low-speed collision. In the examined case, the passenger in the front seat of the car fractured his neck and died. He did not have his seatbelt on when the vehicle slipped on a frozen road surface on a downward slope of a hill and impacted into the shoulder of the road at low speed. In this type of collision, an occupant’s body will be impacted by the windshield or other interior trim of the car. However, in this case, rather unusually, neither body tissue nor fiber remained although the collision involved a broken windshield. Thus, the reason for the passenger death was unidentified. This study applied the computer simulation package Madymo for analyzing the accident. The result of the simulation was that the passenger, who did not wear a seatbelt, moved forward due to inertia. The upper part of the passenger then rotated and lifted when the knee contacted with the dashboard. By evaluating the structural deformation of the vehicle at the front, we deduced that the collision velocity was 30 km/h. Through a computational experiment that was undertaken using Madymo 7.0, NIC was estimated to be 240 m²/s². This result far exceeded the threshold for neck injuries. In particular, in comparison with whiplash injuries, when the passenger’s head directly impacts the roof following a rear-end collision, the bending moment through hyperextension of the neck is greatly increased. In this study, we concluded that the manner of death was the hyperextension of the neck, as the passenger’s head contacted the roof from underneath.     

Low cost design of parallel parking assist system based on an ultrasonic sensor

This paper presents a low cost design and implementation of a parallel parking assist system (PPAS) based on ultrasonic sensors. Generally, a PPAS requires several types of sensors, such as an ultrasonic sensor, camera sensor, radar sensor and laser sensor for parking space detection. However, our proposed PPAS only requires two ultrasonic sensors on the front and lateral sides for parking space detection. Moreover, a steering angle sensor and wheel speed sensor installed in the vehicle are used to obtain vehicle position information for localization in ultrasonic range data. The hardware architecture of the PPAS based on an electronic control unit (ECU) module, sensor modules and a human machine interface (HMI) module was proposed. Moreover, the software architecture of the PPAS is based on system initialization, scheduling, recognition and a control algorithm. In particular, a novel sensor algorithm was proposed to minimize the vehicle corner error of the ultrasonic sensor. A prototype of the PPAS based on the proposed architecture was constructed. The experimental results demonstrate that the implemented prototype is robust and successfully performs parking space detection and automatic steering control. Finally, the low cost design and implementation of the PPAS was possible due to the cheap ultrasonic sensors, simple hardware design and low computational complexity of the proposed algorithm.     

Analysis of an automotive ground system based on its steady-state model

As more electrical equipment is installed and larger currents are required in vehicles, the automotive ground system becomes more important to guarantee the stable operation of the equipment and efficient power consumption. In this paper, an automotive ground system is analyzed in a steady-state condition, and a simulation model for estimating its ground voltage distribution is described. The automotive ground system is divided into an engine compartment ground and a body ground, and it is modeled as an equivalent resistor network, which is suitable for simulation. By using the developed model, ground voltages are simulated and measurements are taken with a real car. A comparison of the simulation and measurement results shows good agreement, and the validity of the model is confirmed. Then, the factors that dominate the ground voltage level are discussed.     

Estimation of the adhesion force for a disc brake in a skid control condition

The performance of brakes has become important due to increased train speeds. The brake system of a train must possess a large brake force to stop the train safely within a limited stopping distance. However, an excessive brake force deteriorates the ride comfort and causes the train to skid. Therefore, it is necessary to control the brake force within the adhesion force limit. This paper presents an analytical method to estimate the relationship between the brake and adhesion forces of a disc brake system. This method has been applied to the actual disc braking control system of the Korea High-Speed Train (HSR350x), and the adhesion force is estimated in an actual skid condition.     

Model-based control of an electropneumatic brake system for commercial vehicles

A properly functioning brake system is critical for ensuring the safe operation of any vehicle on roadways. Commercial vehicles such as trucks, tractors-trailers and buses are equipped with an air brake system that uses compressed air as the energy transmitting medium. This paper presents a model-based control scheme for an electropneumatic brake system for use in commercial vehicles. A mathematical model for an electropneumatic brake system was developed and corroborated with experimental data. A control scheme was developed based on this model and was used to regulate the pressure of air inside the brake chamber according to a desired pressure trajectory. This control scheme was implemented on an experimental test bench, and its performance was studied for various values of the controller parameter. The control scheme was tested for various desired pressure trajectories reflecting actual brake operation.     

Digital human body model for seat comfort simulation

Using the recent anthropometry of the North American population, human body models were developed for seat comfort simulation. The external geometry of the models was acquired from the three-dimensional whole body laser scan of recruited volunteers in a driving position. The selection criteria for volunteers with standard size and shape were derived from a statistical factor analysis of the Size USA database. As a practical application of the model in a design process, comfortable driving postures were constructed by adopting the cascade prediction model (CPM), which takes into account both interior package layout and the driver’s anthropometry. The detail modeling process of finite element modeling and its validation results against volunteer measurements are introduced.     

Behavior of taxi customers in hailing vacant taxis: a nested logit model for policy analysis

This study models and examines the taxi customers' preferences for hailing vacant taxis on streets. A stated preference survey was conducted to randomly select and interview 1242 taxi customers at taxi stands and pedestrians on streets, who had experiences of taking taxis recently, about their choices under different given hypothetical scenarios. In total, 4968 observations were collected and used for developing the discrete choice models for the analysis. To account for the potential correlations among alternatives, two nested logit models are developed, calibrated, and compared with a standard multinomial logit model in the investigation. The results of likelihood ratio test demonstrate that one of the developed nested logit models is better than the standard multinomial logit model to describe the search behavior of taxi customers. The model results also show that the walking time to and the waiting time at the location for hailing taxis, the extra travel time to the destination because of local circulation for finding a way from the pickup location heading to a passenger's destination, as well as the taxi customers' perceptions for walking to and waiting at taxi stands were found as significant factors to influence their decisions. In addition, the results of market segmentation analysis illustrate the variations in taxi‐search strategies of taxi customers in different districts and regions. Some policy implications on introducing more taxi stands and improving the utilization rates of taxi stands are also discussed. We believe that the proposed models, findings, and discussion are useful for developing micro‐simulation models to evaluate the performance of road traffic networks with taxi services and developing simulation‐based optimization models to answer policy questions related to taxi services. Copyright © 2015 John Wiley & Sons, Ltd.