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Technical Paper

Yaw Stability Control and Emergency Roll Control for Vehicle Rollover Mitigation

2010-10-05
2010-01-1901
In this paper a yaw stability control algorithm along with an emergency roll control strategy have been developed. The yaw stability controller and emergency roll controller were both developed using linear two degree-of-freedom vehicle models. The yaw stability controller is based on Lyapunov stability criteria and uses vehicle lateral acceleration and yaw rate measurements to calculate the corrective yaw moment required to stabilize the vehicle yaw motion. The corrective yaw moment is then applied by means of a differential braking strategy in which one wheel is selected to be braked with appropriate brake torque applied. The emergency roll control strategy is based on a rollover coefficient related to vehicle static stability factor. The emergency roll control strategy utilizes vehicle lateral acceleration measurements to calculate the roll coefficient. If the roll coefficient exceeds some predetermined threshold value the emergency roll control strategy will deploy.
Journal Article

Vehicle System Simulator: Development and Validation

2011-09-13
2011-01-2166
A graphical user interface (GUI) toolbox called Vehicle System Simulator (VSS) is developed in MATLAB to ease the use of this vehicle model and hopefully encourage its widespread application in the future. This toolbox uses the inherent MATLAB discrete-time solvers and is mainly based on Level-2 s-function design. This paper describes its built-in vehicle dynamics model based on multibody dynamics approach and nonlinear tire models, and traction/braking control systems including Cruise Control and Differential Braking systems. The built-in dynamics model is validated against CarSim 8 and the simulation results prove its accuracy. This paper illustrates the application of this new MATLAB toolbox called Vehicle System Simulator and discusses its development process, limitations, and future improvements.
Technical Paper

The Virginia Tech Center for Transportation Research “Smart Truck” - An Instrumented Heavy Vehicle for Evaluation of Intelligent Transportaltion Systems

1997-11-17
973186
The objective of this paper is to describe a Class 8 heavy truck that the Virginia Tech Center for Transportation Research has modified and instrumented for use in evaluating Intelligent Transportation Systems (ITS) technologies. The truck is capable of recording a variety of data, both electronic and video, in real-time from a suite of sensors and cameras that have been inconspicuously mounted on the tractor. The tractor, trailer, and instrumentation package enable Virginia Tech to conduct commercial vehicle ITS research related to safety and human factors, and advanced vehicle control systems (AVCS). This paper will describe the instrumentation package, and address both general and specific types of research that can be performed using this truck.
Technical Paper

The Challenge of Designing a Semiactive Damper for Heavy Truck Seat Suspensions

2005-11-01
2005-01-3544
The close proximity of seat suspensions to human body presents several challenges in terms of the perception of the suspension forces by the vehicle operator. This is particularly true of the suspensions with time-varying forces, such as semiactive seat suspensions. The major challenge in such suspensions is changing the suspension force from one state to under, without causing excessive amounts of dynamic jerk. This paper looks into the cause of dynamic jerk in semiactive suspensions with skyhook control, and presents two alternative implementations of skyhook control, called “no-jerk skyhook,” and “skyhook function,” for the purpose of this study. An analysis of the relationship between absolute velocity of the sprung mass and the relative velocity across the suspension is used to show the damping force discontinuities that result from skyhook control.
Technical Paper

Study of Semiactive Adaptive Control Algorithms with Magneto-Rheological Seat Suspension

2004-03-08
2004-01-1648
This paper presents a parametric study of two semiactive adaptive control algorithms through simulation: the non-model based skyhook control, and the newly developed model-based nonlinear adaptive vibration control. This study includes discussion of suspension model setup, dynamic analysis approach, and controller tuning. The simulation setup is from a heavy-duty truck seat suspension with a magneto-rheological (MR) damper. The dynamic analysis is performed in the time domain using sine sweep excitations without the need to linearize such a nonlinear semiactive system that is studied here. Through simulation, the effectiveness of both control algorithms is demonstrated for vibration isolation. The computation flops of the simulation in the SIMULINK environment are compared, and the adaptability is studied with respect to plant variations and different excitation profiles, both of which come across typically for vehicle suspension systems.
Technical Paper

Semiactive Fuzzy Logic Control for Heavy Truck Primary Suspensions: Is it Effective?

2005-11-01
2005-01-3542
Using a simulation model, this study intends to provide a preliminary evaluation of whether semiactive dampers are beneficial to improving ride and handling in class 8 trucks. One of the great challenges in designing a truck suspension system is maintaining a good balance between vehicle ride and handling. The suspension components are often designed with great care for handling, while maintaining good comfort. For Class 8 trucks, the vehicle comfort is also greatly affected by the cab and seat suspensions. Dampers for passive suspensions are tuned “optimally,” using various metrics that the ride engineer may consider, for the condition in which the truck operates most frequently. In recent years, the popularity of semiactive dampers in passenger vehicles has prompted the possibility of considering them for class 8 trucks. In this study, the vehicle safety versus ride comfort trade-off is studied for a certain class of suspensions with semiactive fuzzy control.
Technical Paper

Robust Optimal Control of Vehicle Lateral Motion with Driver-in-the-Loop

2012-09-24
2012-01-1903
Dynamic “Game Theory” brings together different features that are keys to many situations in control design: optimization behavior, the presence of multiple agents/players, enduring consequences of decisions and robustness with respect to variability in the environment, etc. In previous studies, it was shown that vehicle stability can be represented by a cooperative dynamic/difference game such that its two agents (players), namely, the driver and the vehicle stability controller (VSC), are working together to provide more stability to the vehicle system. While the driver provides the steering wheel control, the VSC command is obtained by the Nash game theory to ensure optimal performance as well as robustness to disturbances. The common two-degree of freedom (DOF) vehicle handling performance model is put into discrete form to develop the game equations of motion. This study focus on the uncertainty in the inputs, and more specifically, the driver's steering input.
Technical Paper

Pneumatically Balanced Heavy Truck Air Suspensions for Improved Roll Stability

2015-09-29
2015-01-2749
This study provides a simulation evaluation of the effect of maintaining balanced airflow, both statically and dynamically, in heavy truck air suspensions on vehicle roll stability. The model includes a multi-domain evaluation of the truck multi-body dynamics combined with detailed pneumatic dynamics of drive-axle air suspensions. The analysis is performed based on a detailed model of the suspension's pneumatics, from the main reservoir to the airsprings, of a new generation of air suspensions with two leveling valves and air hoses and fittings that are intended to increase the dynamic bandwidth of the pneumatic suspensions. The suspension pneumatics are designed such that they are able to better respond to body motion in real time. Specifically, this study aims to better understand the airflow dynamics and how they couple with the vehicle dynamics.
Journal Article

Optimal Direct Yaw Controller Design for Vehicle Systems with Human Driver

2011-09-13
2011-01-2149
Dynamic game theory brings together different features that are keys to many situations in control design: optimization behavior, the presence of multiple agents/players, enduring consequences of decisions and robustness with respect to variability in the environment, etc. In the presented methodology, vehicle stability is represented by a cooperative dynamic/difference game such that its two agents (players), namely, the driver and the direct yaw controller (DYC), are working together to provide more stability to the vehicle system. While the driver provides the steering wheel control, the DYC control algorithm is obtained by the Nash game theory to ensure optimal performance as well as robustness to disturbances. The common two-degree of freedom (DOF) vehicle handling performance model is put into discrete form to develop the game equations of motion.
Technical Paper

On-Vehicle Evaluation of Heavy Truck Suspension Kinematics

2003-11-10
2003-01-3394
This paper presents the setup and test results for evaluating kinematics characteristics of heavy truck suspensions in their actual environment, while installed on the truck. The paper will provide the truck suspension kinematics that are important to the truck dynamics, namely vertical stiffness, roll stiffness, and roll steer. It also presents the nature of the hysteresis that commonly exists in heavy truck suspensions. Next, we present a detailed account of the issues that must be taken into consideration in practice, when measuring various kinematics aspects of a truck suspension. Using a successful laboratory setup for measuring kinematics of heavy truck suspensions, the paper provides an evaluation of a class 8 truck with a trailing arm suspension. The description of the setup provides the details of the instrumentation and means of actuation that are necessary for collecting good kinematics data.
Journal Article

Linear Quadratic Game Theory Approach to Optimal Preview Control of Vehicle Lateral Motion

2011-04-12
2011-01-0963
Vehicle stability is maintained by proper interactions between the driver and vehicle stability control system. While driver describes the desired target path by commanding steering angle and acceleration/deceleration rates, vehicle stability controller tends to stabilize higher dynamics of the vehicle by correcting longitudinal, lateral, and roll accelerations. In this paper, a finite-horizon optimal solution to vehicle stability control is introduced in the presence of driver's dynamical decision making structure. The proposed concept is inspired by Nash strategy for exactly known systems with more than two players, in which driver, commanding steering wheel angle, and vehicle stability controller, applying compensated yaw moment through differential braking strategy, are defined as the dynamic players of the 2-player differential linear quadratic game.
Technical Paper

Laboratory Evaluation of Heavy Truck Dynamics: Are the Test Results Useful?

2003-11-10
2003-01-3395
This paper provides an insight into some of the benefits of evaluating heavy truck dynamics in the laboratory. Recognizing that the vast majority of ride and engineering tests that are commonly conducted on heavy trucks occur in the field or on test tracks, the paper shows that there is much to be gained from dynamic testing of a truck in the laboratory under proper conditions. Of course, the main reasons for considering laboratory testing are that the tests can be conducted a) at much lower costs than field testing, and b) in a much more repeatable manner. The argument against laboratory tests has always been that they may not represent the true dynamic environment that a truck would experience in revenue service. Some of the issues related to properly setting up a truck in the laboratory such that the experiments can relatively accurately emulate what occurs in the field are presented.
Journal Article

Integrating Electromechanical Systems in Commercial Vehicles for Improved Handling, Stability, and Comfort

2014-09-30
2014-01-2408
The 2014 SAE Buckendale Lecture will address the past developments and challenges of electromechanical “smart” systems for improving commercial vehicles' functionality. Electromechanical systems combine traditional mechanical devices with electrical components to provide far higher degree of functionality and adaptability for improved vehicle performance. The significant advances in microprocessors and their widespread use in consumer products have promoted their implementation in various classes of vehicles, resulting in “smart” devices that can sense their operating environment and command an appropriate action for improved handling, stability, and comfort. The chassis and suspension application of electromechanical devices mostly relate to controllable suspensions and vehicle dynamic management systems, such as Electronic Stability Control.
Technical Paper

Field Study to Evaluate Driver Fatigue Performance in Air-Inflated Truck Seat Cushions - Subjective Results

2004-10-26
2004-01-2650
This study reports the subjective results from a project investigating the effectiveness of several newly proposed metrics to compare fatigue performance between two distinct truck seat cushions, specifically standard foam versus air-inflated cushions. We also highlight some of the fundamental differences between air-inflated and foam seat cushion based on driver's perceptions. Road tests were performed using existing commercial trucks in the daily operations of Averitt Express. A retrofit air-inflated seat cushion was installed in the fleet's trucks, and the drivers were allowed to adjust to the seats over approximately one week. After this adjustment period, twelve drivers rode on both the air-inflated seat cushion and their original foam seat cushion during their regularly scheduled routes. Surveys were collected throughout the test sessions and the truck seats were fitted with instrumentation to capture physical measurements of seat pressure distribution.
Technical Paper

Field Study to Evaluate Driver Fatigue Performance in Air-Inflated Truck Seat Cushions - Objective Results

2005-04-11
2005-01-1008
This study reports the objective results from a project investigating the effectiveness of several newly proposed metrics to compare fatigue performance between two distinct truck seat cushions, specifically standard foam versus air-inflated cushions. The subjective results from this project have shown the drivers in our study prefer the air-inflated seat cushion over their normal foam cushion, and that air-inflated seat cushions provide advantages in terms of comfort, support, and fatigue [1]. This study aims to further explore the differences between these two different seat cushions by highlighting the differences in objective pressure distribution measurements. Road tests were performed using existing commercial trucks in the daily operations of Averitt Express. A retrofit air-inflated seat cushion was installed in the fleet's trucks, and the drivers were allowed to adjust to the seats over approximately one week.
Technical Paper

Efficient Empirical Modeling of a High-Performance Shock Absorber for Vehicle Dynamics Studies

2007-04-16
2007-01-0858
Race teams frequently use tools like shock dynamometers (dynos) to characterize the complex behavior of shock absorbers after they are built and before they are put on the race car for testing to make sure they perform as expected. One way to make use of this shock dyno data is to use it to create a model to predict shock absorber performance over a wide range of inputs. These shock models can then be integrated into vehicle simulations to predict how the vehicle will respond to different shock selections, and aid the race engineer to narrow down possible shock setups before track testing. This paper develops an intuitive nonlinear dynamic shock absorber model that can be quickly fit to experimental data and implemented in simulation studies. Unlike other existing dynamic race shock models, it does not suffer from the complexity of modeling complex physical behavior, or the inefficiencies of unstructured black-box modeling.
Technical Paper

Effects of Passive and Semi-Active Suspensions on Body and Wheel Hop Control

1989-11-01
892487
The effect of primary suspensions (shock absorbers) on the body and axle motion of heavy trucks is investigated. A simulation program is used to show how damper tuning of conventional passive dampers and “skyhook” semiactive dampers effect ride, as measured by body acceleration, and axle motion, as measured by tire acceleration and tire deflection. Special attention is made to the coupling and interaction between the body and the axle motion. It is shown that passive and semiactive dampers have a different effect on the axle and body dynamics.
Technical Paper

Effects of Commercial Truck Configuration on Roll Stability in Roundabouts

2015-09-29
2015-01-2741
This paper presents the results of a study on the effect of truck configurations on the roll stability of commercial trucks in roundabouts that are commonly used in urban settings with increasing frequency. The special geometric layout of roundabouts can increase the risk of rollover in high-CG vehicles, even at low speeds. Relatively few in-depth studies have been conducted on rollover stability of commercial trucks in roundabouts. This study uses a commercially available software, TruckSim®, to perform simulations on four truck configurations, including a single-unit truck, a WB-67 semi-truck, the combination of a tractor with double 28-ft trailers, and the combination of a tractor with double 40-ft trailers. A single-lane and multilane roundabout are modeled, both with a truck apron. Three travel movements through the roundabouts are considered, including right turn, through-movement, and left turn.
Technical Paper

Effect of Panhard Rod Cab Suspensions on Heavy Truck Ride Measurements

2004-10-26
2004-01-2710
This study provides an experimental account of the effect of panhard rod suspensions on heavy truck ride, as evaluated by the B-post vertical and fore-aft accelerations. After describing the test setup, the paper will describe the details of two rear cab suspensions that are commonly used in North American trucks. Cab suspensions with dampers or similar elements that are used to provide lateral forces at the rear of the cab (called “baseline” cab suspension for the purpose of this study) and those that use a lateral link with a torsion spring at one end-commonly called “panhard rod”-are the two classes of rear cab suspensions that are considered in this study. The tests are performed on a class 8 truck that is setup in the laboratory for the purpose of providing good test repeatability and conducting an accurate design of experiment. The test results, which are analyzed in frequency domain, are compared for the two cab suspensions.
Technical Paper

Dynamic Influence of Frame Stiffness on Heavy Truck Ride Evaluation

2004-10-26
2004-01-2623
This experimental study determines the effect of truck frame stiffness on truck ride, as measured by B-post vertical and fore-aft accelerations. After describing the test setup, the paper will describe the details of two truck frames that are used in a series of tests conducted on a class-8 truck in the laboratory. The frames that are used for the tests include what commonly is used in production trucks in North American markets (called “baseline” frame), and a frame that is 15% thinner (called “thin” frame). The test results, which are analyzed in frequency domain, are compared for the two frames. They indicate that the thin frame performs similar to the baseline frame when the truck is subjected to heave inputs. For roll inputs, the thin frame causes an increase in B-post accelerations, mostly at frequencies associated with the frame beaming and the primary (axle) suspension resonance.
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