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Bushing elasticity is one of the most important compliance factors that significantly influence driving behavior. The deformations of the bushings change the wheel orientations under external forces. Another important factor of bushing compliance is to provide a comfortable driving experience by isolating the vibrations from road irregularities. However, the driving comfort and driving dynamics are often in conflict and need to be balanced in terms of bushing compliance design. Specifically, lateral force steer and brake force steer are closely related to safety and stability and comprises must be minimized. The sensitivity analysis helps engineers to understand the critical bushing for certain compliance attributes, but optimal balancing is complicated to understand. The combination of individual bushing stiffness must be carefully set to achieve an acceptable level of all the attributes.

The automotive industry continues to increase the utilization of computer-aided engineering. This put demands on finding reliable objective measures that correlate to subjective driver assessments on driving stability performance. However, the drivers’ subjective perception of driving stability can be difficult to quantify objectively, especially on test tracks where the wind conditions cannot be controlled. The advancement in driving simulator technology may enable evaluation of driving stability with high repeatability. The purpose of this study is to correlate the subjective assessment of driving stability to reliable objective measures and to evaluate the usefulness of a driving simulator for the subjective assessment. Two different driver clinic studies were performed in a state-of-the-art driving simulator. The first study included 38 drivers (professional, experienced and common drivers) and focused on crosswind gust sensitivity.

In vehicle development, a subjective evaluation of the vehicle’s behavior at high speeds is usually conducted by experienced drivers with the objective of assessing driving stability. To avoid late design changes, it is desirable to predict and resolve perceived instabilities early in the development phase. In this study, a mathematical model is developed from measurements during on-road tests to predict the driver’s ability to identify vehicle instabilities under excitations such as aerodynamic excitations. A vehicle is fitted with add-ons to create aerodynamic excitations and is driven by multiple drivers on a high-speed track. Drivers’ evaluation, responses, cabin motion, and crosswind conditions are recorded. The influence of yaw and roll rates, lateral acceleration, and steering angle at various frequency ranges when predicting the drivers’ evaluation of induced excitation is demonstrated. The drivers’ evaluation of vehicle behavior is influenced by driver-vehicle interactions.

The automotive trends of vehicles with lower aerodynamic drag and more powerful drivetrains have caused increasing concern regarding stability issues at high speeds, since more streamlined bodies show greater sensitivity to crosswinds. This is especially pronounced for high vehicles, such as sports utility vehicles. Besides, the competitiveness in the automotive industry requires faster development times and, thus, a need to evaluate the high speed stability performance in an early design phase, preferable using simulation tools. The usefulness of these simulation tools partly relies on realistic boundary conditions for the wind and quantitative measures for assessing stability without the subjective evaluation of experienced drivers. This study employs an on-road experimental measurements setup to define relevant wind conditions and to find an objective methodology to evaluate high speed stability.

Energy saving in general and less polluting vehicles in specific, become more and more urgent topics. One reason is that, in a world where the demand for fast transportation is increasing, the risk of global warming is a fact. Hybrid Vehicles (HV:s) are proposed as a more environmentally friendly candidate than conventional vehicles. Nowadays, there are numerous different types of HV:s and the components can, in theory, be sized in infinite ways. There is no simple answer to how to choose driveline configuration and size components in a HV. This paper describes one method, Driveline Synthesis (DS), that systematically presents a suitable driveline, on the basis of demands and conditions. Examples of demands are driving cycle and emission free zones. Some conditions are fuel price, tax on pollution and discount rate. The most suitable driveline is defined as the most cost effective.

The objective of this paper is to demonstrate a possibility of optimizing the fixed gear ratios of an automatic transmission by using a special modeling and simulation technique. It is a problem to design the set of ratios in general, and especially for transient driving situations. Sometimes there is a lack of systematic methods to optimize dynamic systems, and particularly vehicle powertrain systems, which is the focus of this paper. The techniques used involve a dynamic engine model and a refined gearbox model. To give each set of ratios a fair judgement, the gearbox control system is calibrated for each new set. The influence of a set of ratios on the vehicle acceleration performance and fuel economy in a given driving cycle is evaluated against an optimization criterion. Calibration of the gearbox control system is performed with stationary analysis. This is the most suitable way with respect to the input signals of gearbox control systems of today.

In order to estimate vehicle energy consumption and emissions, it is common to carry out a driving cycle simulation. In a conventional analysis for this purpose, the vehicle speed is prescribed to follow a function of time exactly. Such an analysis is quasi-stationary, i.e., the transient behavior of the system is not fully taken care of. The direction of cause and effect is unnatural. The opposite is a driver controlled model, where an active driver model tries to achieve the driving cycle speed by choosing a proper accelerator pedal position. Such a model requires transient analysis. Need of more accurate simulations and studies of new driveline concepts call for transient driving cycle analysis. Examples on and classification of such cases are presented in this paper. The paper also presents a DAE approach to the modelling and analysis.