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Journal Article

Driver's Preview Strategy and its Impact on NATO Double Lane Change Maneuver

In this study, a closed-loop driver-vehicle system model is established with ADAMS/CAR. A double lane change maneuver path boundary is setup based on NATO AVTP 03-160W requirement. Multiple choices of driver preview path are derived from optimization of the closed-loop driver-vehicle-road system, where the objective is to successfully pass the double lane change maneuver at a given forward speed without violating the boundary. With the multiple choices of preview path, the vehicle dynamic responses, such as tire patch load, vehicle lateral acceleration, yaw velocity, steering wheel angle and roll angle, will vary associated with each driver's preview path. The relationship between the path clearance and vehicle dynamic responses as well as the forward speeds is further investigated. Finally a methodology to predict the maximum forward speed to successfully pass double lane change is proposed.
Journal Article

Handling and Ride Performance Sensitivity Analysis for a Truck-Trailer Combination

A truck-trailer combination is modeled using ADAMS/Car from MSC Software for handling and ride comfort performance simulations. The handling events include a double lane change and lateral roll stability. The ride comfort performance events include several sized half-rounds and various RMS courses. The variables for handling performance evaluation include lateral acceleration, roll angles and tire patch normal loads. The variables for ride performance evaluation are absorbed power and peak acceleration. This study considers the trailer spring stiffness, anti-roll bar and jounce bumper gap as the design variables. Through DOE simulations, we derived the response surface models of various performance variables so that we could consider the performance sensitivities to the design variables.
Journal Article

Impact of Driver's Steer Control on Truck-Trailer Combination when Negotiating NATO Double Lane Change Maneuver

In this study, a closed-loop driver-truck-trailer system model is established with ADAMS/Car. A double lane change maneuver (DLCM) path boundary is set up based on the NATO AVTP 03-160W requirement. The best driver preview path at a given speed to pass the DLCM is derived from optimization of the closed-loop driver-vehicle-road system, where the objective is to successfully pass the DLCM at the given forward speed. This must be done without violating the maneuver boundary, lifting any tires off the ground, as well as staying within the Driver's steering effort limit. Depending upon the Driver's control strategy, which is reflected by the formulation of the optimal objective, the dynamic responses of the truck-trailer combination will vary. Two extreme conditions are discussed in this study: full and no consideration of trailer, respectively, when negotiating the DLCM.
Technical Paper

In-Plane Flexible Ring Tire Model Development for Ride Comfort & Braking/Driving Performance Analysis under Straight-line Driving Condition

Vehicle tire performance is an important consideration for vehicle handling, stability, mobility, and ride comfort as well as durability. Significant efforts have been dedicated to tire modeling in the past, but there is still room to improve its accuracy. In this study, a detailed in-plane flexible ring tire model is proposed, where the tire belt is discretized, and each discrete belt segment is considered as a rigid body attached to a number of parallel tread blocks. The mass of each belt segment is accumulated at its geometric center. To test the proposed in-plane tire model, a full-vehicle model is integrated with the tire model for simulation under a special driving scenario: acceleration from rest for a few seconds, then deceleration for a few seconds on a flat-level road, and finally constant velocity on a rough road. The simulation results indicate that the tire model is able to generate tire/road contact patch forces that yield reasonable vehicle dynamic responses.
Technical Paper

Sensitivities of Suspension Bushings on Vehicle Impact Harshness Performances

In this paper, we study the sensitivity of a vehicle impact harshness (IH) performance to the suspension bushing rates. A mid-sized uni-body SUV is selected for this study, with the acceleration responses at the driver seat track and the steering wheel as objective functions. A sensitivity study is conducted using an ADAMS full vehicle model including a tire model and flexible body structure representation over an IH event. The study resulted in the identification of key bushings that affect the IH performance and its sensitivity to the bushing rates. Based on the results, we came-up with an “optimal” bushing set that minimizes impact harshness, which was subjectively verified to result in significant improvement in IH.
Technical Paper

Study of Directional Analysis of a Closed-Loop Driver/Tractor-Semitrailer Vehicle

A closed-loop articulated vehicle-driver model, incorporating the path errors, lateral accelerations of the two units and the rate of steering, is proposed to study the directional control behavior of the driver. The closed-loop driver-vehicle model is formulated upon integrating the yaw-plane model of a five-axle articulated vehicle and a comprehensive driver model. The driver model, incorporating the delays associated with the limb movement and muscle activities, is developed with an objective to minimize the lateral acceleration of vehicle, and the lateral position and orientation errors between the previewed and the actual path of the tractor. Various parameters required to describe the driver's contributions are identified through minimizing a weighted performance index subject to an array of limit constraints established from the reported data.
Technical Paper

Suitable Load Case for Structural Analysis of Outriggers Applied for Vehicle Handling and Stability Field Test

An outrigger is the device that is mounted on a test vehicle to protect it and/or its driver during handling test maneuvers, such as double lane change, constant radius cornering, J-turn, etc. The design of the outrigger is challenged by the constraints associated with its size, installation flexibility, strength, weight, and moment of inertia for a minimum or negligible impact on the test vehicle dynamics. To achieve an appropriate design of an outrigger for a specific vehicle, it is essential to determine the appropriate dynamic loads that the outrigger needs to support after its geometry and installation scheme have been determined. In this study, a flexible representation of an outrigger is mounted on a military vehicle that is simulated on a NATO double lane change maneuver at the given forward speeds.
Technical Paper

Suspension Tuning Parameters Affecting Impact Harshness Performance Evaluation

In this paper, a comprehensive evaluation index for impact harshness (IH) is proposed. A mid-sized uni-body SUV is selected for this study, with the acceleration responses at the various vehicle body locations as objective functions. A sensitivity study is conducted using an ADAMS full vehicle model with flexible body structure representation over an IH event to analyze the influence of various suspension tuning parameters, including suspension springs, shock damping, steer gear ratio, unsprung mass, track-width, and bushing stiffness.
Journal Article

Tire Model Application and Parameter Identification-A Literature Review

A tire may be one of the most critical and complex components in vehicle dynamics and road loads analyses because it serves as the only interface between the road surface and the vehicle. Extensive research and development activities about vehicle dynamics and tire models have been published in the past decades, but it is still not clear about the applications and parameter identification associated with all of these tire models. In this literature review study, various published tire models used for vehicle dynamics and road loads analyses are compared in terms of their modeling approaches, applications and parameters identification process and methodologies. It is hoped that the summary of this literature review work can help clarify and guide the future research and development direction about tire modeling.
Journal Article

Understanding Measured Spindle Loads Differences with Advanced Tire Model

In this study, a full vehicle with advanced LMS comfort and durability tire (CDT) model was established with ADAMS software to predict the spindle loads of the vehicle under a severe proving ground rough road event. From a series of simulations with various design changes, the spindle loads sensitivities to those design changes were identified. The simulated results were also compared with the measured data and a good correlation was achieved.