On-road assessment of in-vehicle driving workload for older drivers: Design guidelines for intelligent vehicles

There has been recent interest in intelligent vehicle technologies, such as advanced driver assistance systems (ADASs) or in-vehicle information systems (IVISs), that offer a significant enhancement of safety and convenience to drivers and passengers. However, the use of ADAS- and IVIS-based information devices may increase driver distraction and workload, which in turn can increase the chance of traffic accidents. The number of traffic accidents involving older drivers that are due to distraction, misjudgment, and delayed detection of danger, all of which are related to the drivers’ declining physical and cognitive capabilities, has increased. Because the death rate in traffic accidents is higher when older drivers are involved, finding ways to reduce the distraction and workload of older drivers is important. This paper generalizes driver information device operations and assesses the workload while driving by means of experiments involving 40 drivers in real cars under actual road conditions. Five driving tasks (manual only, manual primarily, visual only, visual primarily, and visual-manual) and three age groups (younger (20–29 years of age), middle-aged (40–49 years of age), and older (60–69 years of age)) were considered in investigating the effect of age-related workload difference. Data were collected from 40 drivers who drove in a real car under actual road conditions. The experimental results showed that age influences driver workload while performing in-vehicle tasks.     

Development of a fiber-reinforced plastic armrest frame for weight-reduced automobiles

This paper presents the design optimization process of a short fiber-reinforced plastic armrest frame to minimize its weight by replacing the steel frame with a plastic frame. The analysis was carried out with the equivalent mechanical model and design of experiment (DOE) method. Instead of considering the whole structure, it is divided into three simpler regions to reduce the complexity of the problem through examining its structural characteristics and load conditions. The maximum stress and deflection of the regions that carry the normal load are calculated by the analytical mathematical form derived from an equivalent model. The other regions loaded by contact stress are handled by FEM (finite element method), the DOE method, and the RSM (response surface model). To optimize the design variables in both cases, the object functions derived from these calculations are solved with a CAE (computer aided engineering) tool. This method clearly shows the mechanical and mathematical representation of structural optimization and reduces the computing costs. After design optimization, the weight of the optimum plastic-based armrest frame is reduced by about 18% compared to the initial design of a plastic frame and is decreased by 50% in comparison with the steel frame. Some prototypical armrest frames were also made by injection molding and tested. The research results fulfilled all of the design requirements.     

Automobile defrosting system analysis through a full-scale model

Adequate visibility through the automobile windshield is of paramount practical significance, most often at very low temperatures when ice tends to form on the windshield screen. But the numerical simulation of the defrost process is a challenging task because phase change is involved. In this study numerical solution was computed by a finite volume computational fluid dynamics (CFD) program and experimental investigations were performed to validate the numerical results. It was found that the airflow produced by the defrost nozzle is highly nonuniform in nature and does not cover the whole windshield area. The nonuniformity also severely affected the heating temperature pattern on the windshield. The windshield temperature reached a maximum in the vicinity of the defroster nozzle in the lower part of the windshield and ranged from 9∼31°C over a period of 30 min, which caused the frost to melt on the windshield. The melting time was under 10 minutes, which satisfied the NHTSA standard. The numerical predictions were in close agreement with the experimental results. Thus, CFD can be a very useful design tool for an automobile HVAC system.     

Development of a semi-empirical program for predicting the braking performance of a passenger vehicle

Since the invention of automobiles, the need to know the braking performance of vehicles has been acknowledged. However, because there are numerous design variables as well as nonlinearities in the braking system, it is difficult to predict the performance accurately. In this paper, a computational program is developed to estimate the braking performance numerically. This synthetic braking performance program accounts for pedal force, pedal travel and deceleration of braking parts, such as master cylinder, booster, valve, brake pad, rotor, and hoses. To improve the accuracy of program, a semi-empirical model of a braking system is introduced by using the empirical test data of pad compression, hose expansion and the friction coefficient between the pad and rotor. The accuracy of the estimation is evaluated by comparing it to the actual vehicle test results. The developed program is easy for the brake system engineers to manipulate and it can be used in the development of new vehicles by incorporating the graphical presentations.     

Design methodology of hybrid electric vehicle energy sources: Application to fuel cell vehicles

This paper presents a methodology to optimize the sizing of the energy and power components in a fuel cell electric vehicle from the driving mission (which includes driving cycles, a specified acceleration and autonomy requirements). The fuel cell and the Energy Storage System associated (battery or/and ultra capacitor) design parameters are the numbers of series and parallel branches respectively Nsi and Npi. They are set so as to minimize the objective function that includes mass, cost, fulfilling the performance requirements and respect the technological constraints of each power component through a penalty function. The methodology is based on a judicious combination of Matlab-Simulink® for the global simulation and a dedicated software tool Pro@Design®. Both are well suited to treat inverse problems for the optimization. An application for a fuel cell/battery powertrain illustrates the feasibility of the proposed methodology.     

Sideslip angle estimation considering short-duration longitudinal velocity variation

The accurate estimation of sideslip angle is necessary for many vehicle control systems. The detection of sliding and skidding is especially critical in emergency situations. In this paper, a sideslip angle estimation method is proposed that considers severe longitudinal velocity variation over the short period of time during which a vehicle may lose stability due to sliding or spinning. An extended Kalman filter (EKF) based on a kinematic model of a vehicle is used without initialization of the inertial measurement unit to estimate vehicle longitudinal velocity. A dynamic compensation method that compensates for the difference in the locations of the vehicle velocity sensor and the IMU in on-road vehicle tests is proposed. Evaluations with a CarSim™ 27-degree-of-freedom (DOF) model for various vehicle test scenarios and with on-road tests using a real vehicle show that the proposed sideslip angle estimation method can accurately predict sideslip angle, even when vehicle longitudinal velocity changes significantly.     

Proper PD steering assistance constant based on the driving situation

Proportional derivative (PD) steering assistance can greatly improve the control stability of a vehicle. However, for all PD steering methods, the discomfort associated with the need to continuously turn the steering wheel during cornering is significant. Because the steering return phenomenon of the steering wheel stop like this is not preferable, PD steering assistance should be extremely weak (almost 0) during normal cornering. Alternatively, during drift cornering, during which the grip area of the tires is exceeded, PD steering assistance is helpful because the driver has good control over counter-steering. Moreover, the use of PD steering assistance is preferable during lane changes because the response and settling of a vehicle is greatly improved when PD steering assistance is used. Based on these considerations, a previous report examined steering method controls in which the PD steering assistance constant was incorporated along with the drivers’ perception changes in certain driving situations. This study aimed to determine a suitable PD steering assistance constant in relation to the driving situation. A proper PD steering assistance constant was found to exist for specific driving situations. Based on the results of gaze detection using an eye mark recorder, the study was able to reduce the right and left difference of the gaze at the driver by controlling PD steering assistance using a proper PD steering assistance constant for various driving situations.     

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.     

Structural design of an outer tie rod for a passenger car

This study proposes a structural design method for an outer tie rod installed in a passenger car. The weight of the outer tie rod is optimized by using the aluminum alloy Al6082M, which is developed as a steel-substitute material, and applying structural optimization techniques. The high strength aluminum with improved mechanical properties was developed to reduce the weight of the outer tie rod. The newly developed aluminum alloy Al6082M is applied as the material of the outer tie rod. The static strength due to inertia force, durability and buckling performances are considered in the structural design of the outer tie rod. At the proto design stage of a new outer tie rod, it is cost-effective to utilize FE (finite element) analysis to predict each of these performances. In addition, the current trend in the structural design of automobile parts is to use optimization techniques to reduce the weights of the parts. First, for an arbitrary base design, the static strength, the life cycle and the buckling load are calculated to check whether the design satisfies its criteria. Then, the critical performance is selected so as to include its loading condition only in the optimization process. In this study, the metamodel based optimization process using kriging is adopted to obtain the minimum weight satisfying the critical design requirement. Then, the feasibility of the determined optimum shape is investigated against the other performances. Finally, the optimum design of outer tie rod is modified by considering forging efficiency. The performances of the final design are investigated through simulation and experiment.     

Performance measurements of a tracked vehicle system

To improve crossing ability, the most important performance factor for tracked vehicle systems operating on low-bearing capacity peats, and to minimize income losses that result from downtime and maintenance costs, a vehicle was designed in order to adapt to operating condition changes. This article describes the mobile performance of a novel vehicle with segmented rubber tracks on a low-bearing capacity peat. At an equivalent travelling speed, the novel vehicle’s tractive performance in a variable operating environment caused by changes in terrain cohesiveness and hydrodynamic responses was superior to that of the previous model. The new vehicle, which could be operated on the Sepang peat, showed a tractive effort of 42.2% of the gross vehicle weight in field experiments; the recommended minimum tractive effort is between 30 and 36% of the gross vehicle weight.