The Influence of Tire Factors on the Stability of Trucks and Tractor Trailers

The mechanical properties of tires and trucks are contrasted with comparable properties of the motor car to explain why the motor truck and the tractor-trailer can exhibit fixed-control instability at moderate levels of lateral acceleration. The (1) rearward bias in the distribution of roll stiffness, (2) large ratio of e.g. height to track, and (3) low torsional stiffness of the parallel-rail frame (as typically employed in heavy commercial vehicles) are found to be the major factors implicated in this phenomenon. Experimental and analytical evidence is provided to show how tire inflation pressure and mixes of (a) tire-carcass construction and (b) tread design also influence stability at moderate levels of lateral acceleration. Conclusions relating to the safety of commercial vehicle operations are drawn.     

Aerodynamics of Road- and Rail Vehicles

The technical state-of-the-art of aerodynamics of ground transportation vehicles is reviewed. Currently available theoretical calculation methods and experimental simulation techniques as well as typical results illustrating the impact of aerodynamics on vehicle performance and running characteristics are summarized and the interactions between vehicle system dynamics and aerodynamics are adressed. Correlation of theoretical and experimental data show the present potential of vehicle aerodynamics and point to fields in which further research work is necessary.     

Design of a Stroke Dependent Damper for the Front Axle Suspension of a Truck Using Multibody System Dynamics and Numerical Optimization

Summary A stroke dependent damper is designed for the front axle suspension of a truck. The damper supplies extra damping for inward deflections rising above 4 cm. In this way the damper should reduce extreme suspension deflections without deteriorating the comfort of the truck. But the question is which stroke dependent damping curve yields the best compromise between suspension deflection working space and comfort. Therefore an optimization problem is defined to minimize the maximum inward suspension deflection subject to constraints on the chassis acceleration for three typical road undulations. The optimization problem is solved using sequential linear programming (SLP) and multibody dynamics simulation software. Several optimization runs have been carried out for a small two degree of freedom vehicle model and a large full-scale model of the truck semi-trailer combination. The results show that the stroke dependent damping can reduce large deflections at incidental road disturbances, but that the optimum stroke dependent damping curve is related to the acceleration bound. By means of vehicle model simulation and numerical optimization we have been able to quantify this trade-off between suspension deflection working space and truck comfort.     

Aeroelastic Effects in Multibody Dynamics

To enable a realistic assessment of the aeroelastic phenomena of aircraft, a simultaneous application of computational fluid dynamics (CFD), computational structural mechanics and flight mechanics has to be performed. Each discipline has developed powerful specialized tools which have to be adapted for multidisciplinary applications. The combination of CFD and elastic multibody systems is well suited for the simulation of a range of aircraft applications, especially for aircraft ground dynamics. Approaches to a coupling of elastic multibody systems and computational fluid dynamics have been performed using close coupling, that is a modal approach, and loose coupling, that is by co-simulation. In the article the applied programs and the coupling methods are presented. Advantages and limits of using multibody simulation as compared to the direct use of FEA methods for the representation of structural dynamics are discussed. Results of coupled steady and unsteady simulations are presented. Finally, an approach to the aeroelastic trim problem is shown.     

Overview of Coupling of Multibody and Control Engineering Tools

The role of Computer Aided Engineering in vehicle development has been significantly increased during the last decade. Specialised simulation tools became very complex, however, growing demands on complexity and particularly interdisciplinarity of vehicles and their simulation models have led to a number of approaches trying either to develop multidisciplinary simulation tools or to connect various specialised simulation tools by interfaces. This paper addresses some aspects of interconnection of the specialised simulation tools as one possibility for simulating complex mechatronic vehicle systems. It classifies the interfaces between specialised software packages in general, mentions some historical development of the interfacing and further discusses the examples of the implemented couplings between the Multibody System codes and Computer Aided Control Engineering tools. Finally, the performance of selected interfaces is compared on an example simulation of a controlled vehicle suspension.     

Wheel/rail interface management in heavy haul railway operations—applying science and technology

The primary objective of the paper is to review science and technologies that have been developed by various scientists and engineers over the years and that have made it possible to push the limits within the wheel/rail interface in the heavy haul railway environment. After describing the wheel/rail stress-state and its consequences, preventative and corrective measures that can assist in optimising wheel and rail life, and thus reduce costs, are reviewed. The significant contribution of measurement and monitoring technologies to quantify the stress-state of the wheel/rail system is highlighted. Finally, a brief review of the fundamentals of contact mechanics, vehicle dynamics and wheel/rail interface analysis software is given.     

Stabilization of Passenger Car-Caravan Combination Using Four Wheel Steering Control

This study aims to stabilize the trailer at high speed. The behavior of passenger cars with four wheel steering system, vehicles with rear wheel steering and of trailer and passenger car are similar. This is regarded as an optimal regulator problem with linear equation of motion, and a state variables feedback control system is adopted. The problem of stability at high speed on a straight course can be solved. Therefore, the passenger car-trailer system can be stabilized. Furthermore, this study indicates the way forward to stabilize a passenger car-trailer system.     

Labour relations in the Hong Kong merchant navy

This paper discusses the role of ratings' and officers unions, and that of boarding-house keepers, in relation to the recruitment and supply of seamen for the Hong Kong Merchant Navy