Power Requirements for Vehicle Suspension Systems

This paper attempts to analyze the power requirements of a vehicle due solely to its suspension system, neglecting the important powers associated with air and rolling resistance. Power requirements for active and passive suspensions are compared using the simplest possible mathematical model. A mass in a gravity field moves at constant velocity over a surface and is supported by a point contact on the surface by a massless but otherwise arbitrary suspension system. It is shown that the average propulsive power required is equal to the average power lost in the suspension. In the limit cases of very stiff or very soft suspensions this power vanishes. Passive suspensions require no other power, but active suspensions may require significant extra power from the prime mover to generate the suspension forces.     

An analysis of the commuter departure time decision

Transportation planners and transit operators alike have become increasingly aware of the need to diffuse the concentration of peak period travel in an effort to improve gasoline economy and reduce peak load requirements. An evaluation of the potential effectiveness of strategies directed to achieve this end requires an understanding of factors which affect commuter trip timing decisions. The research discussed in this article addresses this particular problem through the development and estimation of a commuter departure time (to work) choice model.A number of conclusions were drawn based on the departure time model results and related analyses. It was found that work schedule flexibility, mode, occupation, income, age, and transportation level of service all influence departure time choice. The uncertainty in work arrival time and the consequences of various work arrival times may also be determinants of commuter departure time choice.The estimated model represents improvements over previous work in that it more explicitly considers work arrival time uncertainty and travelers' perceived loss associated with varying work arrival times, and additional socio-demographic factors which can potentially affect departure time choice. Furthermore, the estimated model includes consideration of transit commuters, in addition to single occupant auto and carpool work travelers. The inclusion of transit commuters represents a particularly important contribution for policy analysis, since the model could potentially be used to study the effect of service and employment policies on transit system peak load requirements.     

IN VITRO GLYCATION OF HEMOGLOBIN (HB):CHOOSING THE APPROPRIATE MODEL

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Crosswind Sensitivity of Passenger Cars and the Influence of Chassis and Aerodynamic Properties on Driver Preferences

Results of vehicle crosswind research involving both full-scale driver-vehicle tests and associated analyses are presented. The paper focuses on experimental crosswind testing of several different vehicle configurations and a group of seven drivers. A test procedure, which utilized wind-generating fans arranged in alternating directions to provide a crosswind “gauntlet”, is introduced and described. Driver preferences for certain basic chassis and aerodynamic properties are demonstrated and linked to elementary system responses measured during the crosswind gauntlet tests. Based on these experimental findings and confirming analytical results, a two-stage vehicle design process is then recommended for predicting and analyzing the crosswind sensitivity of a particular vehicle or new design.     

Application of Inverse Models to Vehicle Optimization Problems

This paper presents a nonlinear inverse model of a road vehicle which simulates combined steering and braking/driving. The inputs to the model are the lateral and longitudinal acceleration of the vehicle's sprung mass center. The simulation returns the steering wheel angle and brake/drive torques required to obtain the desired accelerations. An example is presented which demonstrates the utility of inverse models for optimization purposes.     

Development of Vehicle-following Behavior for Automated Vehicle Systems

Automation of vehicular traffic in different forms has been considered by many people. It offers many advantages. Vehicular traffic dynamics for automated vehicle systems are developed here using calculus of variations and optimal control theory. Using such an optimization approach, the relationship of the traffic dynamics developed here and the traffic dynamics which have been used extensively before for non-automated systems is also shown. Such an approach considers multiple objective functions for the system.     

Automobile Directional Characteristics and Driver Steering Performance

Driver steering performance in a simple circular lane-keeping task, as dependent on the directional response characteristics of the vehicle, was measured. Response Surface Methodology models of steering performance are presented. Several canonical variables describe the drivers responses to vehicle changes. Clear-cut optimum vehicle characteristics cannot be determined, but certain combinations of vehicle characteristics are seen to be undesirable for various reasons related to theoretical mechanisms of driver steering control.