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Journal Article

Effect of Cab Suspension Configuration and Location on Tractor Semi-Trailer Driver Comfort

It is well known that the ride quality of trucks is much harsher than that of automobiles. Additionally, truck drivers typically drive trucks for much longer duration than automobile drivers. These two factors contribute to the fatigue that a truck driver typically experiences during long haul deliveries. Fatigue reduces driver alertness and increases reaction times, increasing the possibility of an accident. One may conclude that better ride quality contributes to safer operation. The secondary suspensions of a tractor have been an area of particular interest because of the considerable ride comfort improvements they provide. A gap exists in the current engineering domain of an easily configurable high fidelity low computational cost simulation tool to analyze the ride of a tractor semi-trailer. For a preliminary design study, a 15 d.o.f. model of the tractor semi-trailer was developed to simulate in the Matlab/Simulink environment.
Technical Paper

Driver Models for Virtual Testing of Automotive Run-Off-Road and Recovery Control Systems and Education Strategies

Driver modeling is essential to both vehicle design and control unit development. It can improve the understanding of human driving behavior and decrease the cost and risk of vehicle system verification and validation. In this paper, three driver models were implemented to simulate the behavior of drivers subject to a run-off-road recovery event. Target path planning, pursuit behavior, compensate behavior, physical limitations, and neuromuscular modeling were taken into consideration in the feedforward/feedback driver model. A transfer function driver model and a cost function based driver model from a popular vehicle simulation software were also simulated and a comparison of these three models was made. The feedforward/feedback driver model exhibited the best balance of performance with smallest overshoot (0.226m), medium settling time (1.20s) and recovery time (4.30s).
Technical Paper

Automotive Simulator Based Novice Driver Training with Assessment

Motor vehicle crashes involving novice drivers are significantly higher than matured driver incidents as reported by the National Highway Traffic Safety Administration Fatality Analysis Reporting System (NHTSA-FARS). Researchers around the world and the United States are focused on how to decrease crashes for this driver demographic. Novice drivers usually complete driver education classes as a pre-requisite for full licensure to improve overall knowledge and safety. However, compiled statistics still indicate a need for more in-depth training after full licensure. An opportunity exists to supplement in-vehicle driving with focused learning modules using automotive simulators. In this paper, a training program for “Following Etiquette” and “Situational Awareness” was developed to introduce these key driving techniques and to complete a feasibility study using a driving simulator as the training tool.
Journal Article

Hydrostatic Wheel Drives for Vehicle Stability Control

Hydrostatic (hydraulic hybrid) drives have demonstrated energy efficiency and emissions reduction benefits. This paper investigates the potential of an independent hydrostatic wheel drive system for implementing a traction-based vehicle lateral stability control system. The system allows an upper level vehicle stability controller to produce a desired corrective yaw moment via a differential distribution of torque to the independent wheel motors. In cornering maneuvers that require braking on any one wheel of the vehicle, the motors can be operated as pumps for re-generating energy into an on-board accumulator. This approach avoids or reduces activation of the friction brakes, thereby reducing energy waste as heat in the brake pads and offering potential savings in brake maintenance costs. For this study, a model of a 4×4 hydrostatic independent wheel drive system is constructed in a causal and modular fashion and is coupled to a 7 DOF vehicle handling dynamics model.
Technical Paper

An Investigation into the Effects of Suspension Tuning on the Cornering of a Winston Cup Race Car

Many of the suspension adjustments that are made to improve the handling of asymmetric cars racing on banked oval tracks are not intuitively obvious to the engineer who is used to thinking of symmetric cars on relatively flat roads. This paper investigates the effects of typical suspension adjustments on the steady state handling of a Winston Cup race car. A relatively simple nonlinear car model is combined with a sophisticated tire model to predict steady-state handling on a banked track. The concept of dynamic wedge is explained, and its effects on handling of asymmetric race cars on banked ovals are examined. Results are presented that show the sensitivity of the handling to changes in various suspension characteristics.
Technical Paper

Thermal Optimization of the ECS on an Advanced Aircraft with an Emphasis on System Efficiency and Design Methodology

Two methods for analyzing and evaluating the environmental control system on an advanced aircraft as described in this paper include the conventional first law energy conservation technique and the second law entropy generation minimization technique. Simplified analytical models of the ECS are developed for each method and compared to determine the validity of using the latter to facilitate the design process in optimizing the overall system for a minimum gross takeoff weight (GTW). Preliminary results have illustrated the importance of taking into account system optimization based on system (or component) efficiency. For instance, even though different values were obtained for the rate of entropy generation, the second law analysis of a shell-in-tube heat exchanger led to an optimum tube diameter of 0.12 in (3.05 mm) when both R-12 and R-114 were used as the refrigerant in the vapor cycle.
Technical Paper

Simulation and Evaluation of Semi-Active Suspensions

A simulation of the vertical response of a nonlinear 1/4 car model consisting of a sprung and an unsprung mass was developed. It is being used for preliminary evaluation of various suspension configurations and control algorithms. Nonlinearities include hysteretic shock damping and switchable damping characteristics. Road inputs include discrete events such as bumps and potholes as well as randomly irregular roads having specified power spectral densities (PSDs). Fast Fourier transform data analysis procedures are used to process data from the simulation to obtain PSDs, rms values, and histograms of various response quantities. To aid in assessing ride comfort, the 1/3 octave band rms acceleration of the sprung mass is calculated and compared with specifications suggested by the International Standards Organization (ISO). Cross plots of the rms values of acceleration, suspension travel, and the force of the road on the tire are used to compare the performance of various suspensions.
Technical Paper

Development of a Simulation for Assessment of Ride Quality of Tractor Semi-Trailers

Providing acceptable ride quality of tractor semi-trailers is essential to their viability in the freight transport business. This paper describes the development of a design tool that may be used to investigate the vertical dynamic response and ride comfort of these vehicles. A 12 degrees-of-freedom (DOF) model of the vertical dynamic response was developed and simulated in MATLAB [1]. The model is analyzed in the frequency domain. The input to the model is a user-specified power spectral density (PSD) of the vertical road irregularities. Outputs include modal frequencies, damping ratios and mode shapes, frequency response functions, PSDs and root mean square (rms) vertical and longitudinal accelerations in 1/3 octave bands. The rms values are compared with the specifications for ride comfort cited in ISO 2631 [2].