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Viewing 1 to 20 of 20
2004-03-08
Technical Paper
2004-01-1648
Xubin Song, Mehdi Ahmadian
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.
2010-10-05
Technical Paper
2010-01-1903
Xinjie Zhang, Mehdi Ahmadian, Konghui Guo
Inerters have become a hot topic in recent years, especially in vehicle, train, and building suspension systems. The performance of a passive inerter and a semi-active inerter was analyzed and compared with each other and it showed that the semi-active inerter has much better performance than the passive inerter, especially with the Hybrid control method. Eight different layouts of suspensions were analyzed with a quarter car model in this paper. The adaptation of dimensionless parameters was considered for a semi-active suspension and the semi-active inerters. The performance of the semi-active inerter suspensions with different layouts was compared with a semi-active suspension with a conventional parallel spring-damper arrangement. It shows a semi-active suspension, with more simple configuration and lower cost, has similar or better compromise between ride and handling than a semi-active inerter with the Hybrid control.
2012-09-24
Technical Paper
2012-01-1903
Seyed Hossein Tamaddoni, Saied Taheri, Mehdi Ahmadian
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.
2016-09-27
Technical Paper
2016-01-8038
Yunbo Hou, Yang Chen, Mehdi Ahmadian
Abstract This paper studies the effect of different longitudinal load conditions, roundabout cross-sectional geometry, and different semi-truck pneumatic suspension systems on roll stability in roundabouts, which have become more and more popular in urban settings. Roundabouts are commonly designed in their size and form to accommodate articulated heavy vehicles (AHVs) by evaluating such affects as off-tracking. However, the effect of the roadway geometry in roundabouts on the roll dynamics of semi-tractors and trailers are equally important, along with their entry and exit configuration. , Because the effect of the roundabout on the dynamics of trucks is further removed from the immediate issues considered by roadway planner, at times they are not given as much consideration as other roadway design factors.
2005-11-01
Technical Paper
2005-01-3544
Mehdi Ahmadian
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.
2003-11-10
Technical Paper
2003-01-3395
Mehdi Ahmadian
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.
1997-11-17
Technical Paper
973186
Andrew W. Gellatly, Andrew Petersen, Mehdi Ahmadian, Thomas A. Dingus
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.
2011-09-13
Journal Article
2011-01-2149
Seyed Hossein Tamaddoni, Saied Taheri, Mehdi Ahmadian
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.
2014-09-30
Journal Article
2014-01-2408
Mehdi Ahmadian
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.
1989-11-01
Technical Paper
892487
Mehdi Ahmadian, Robert H. Marjoram
Abstract 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.
2005-11-01
Technical Paper
2005-01-3542
Mehdi Ahmadian
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.
2004-10-26
Technical Paper
2004-01-2623
Mehdi Ahmadian, Paul S. Patricio
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.
2004-10-26
Technical Paper
2004-01-2650
Christopher M. Boggs, Mehdi Ahmadian
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.
2004-10-26
Technical Paper
2004-01-2710
Mehdi Ahmadian, Paul S. Patricio
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.
2004-10-26
Technical Paper
2004-01-2711
Mehdi Ahmadian, Wei Huang
This study provides a numerical evaluation of the dynamic coupling that exists between the powertrain, suspensions, and tire dynamics in class 8 trucks. The spatial dynamics of the driveline, including the offset angels that commonly exist in practice, are modeled along with a lumped-parameter representation of the suspension and tire dynamics in vertical, longitudinal, and torsional directions. The model is used to show how the suspension dynamics and the angle change that it causes in driveline geometry can affect the vibrations resulting from the powertrain. The numerical model is also used for a parametric study in which the effect of various suspension and powertrain parameters on the dynamic coupling that exists between the two is evaluated.
2003-11-10
Technical Paper
2003-01-3394
Mehdi Ahmadian, Young Kong Ahn
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.
2003-11-10
Technical Paper
2003-01-3413
Mohammad H. Elahinia, Mehdi Ahmadian
The primary purpose of this paper is to evaluate how various time-domain system identification techniques, which have been successfully used for different dynamic systems, can be applied for identifying heavy truck dynamics. System identification is the process by which a model is constructed from prior knowledge of a system and a series of experimental data. The parameters obtained from the identification process can be used for developing or improving the mathematical representation of a physical system. In contrast to lighter vehicles, heavy trucks have considerably more flexible frames. The frame can exhibit beaming dynamics in a frequency range that is within the range of interest for evaluating the ride and handling aspects of the truck. Understanding the dynamic contributions of the truck frame is essential for improving the ride characteristics of a vehicle. This understanding is also needed for designing new frame configurations for the existing or new production trucks.
2015-09-29
Technical Paper
2015-01-2741
Yunbo Hou, Mehdi Ahmadian
Abstract 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.
2015-09-29
Technical Paper
2015-01-2749
Yang Chen, Mehdi Ahmadian, Andrew Peterson
Abstract 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.
2011-09-13
Journal Article
2011-01-2166
Seyed Hossein Tamaddoni, Hedieh Alavi, Saied Taheri, Mehdi Ahmadian
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.
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