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Countering the Destabilizing Effects of Shifted Loads through Pneumatic Suspension Design

SAE International Journal of Vehicle Dynamics, Stability, and NVH

Virginia Tech, USA-Yang Chen, Mehdi Ahmadian
  • Journal Article
  • 10-04-01-0001
Published 2019-11-08 by SAE International in United States
This article proposes a novel approach to reduce the destabilizing impacts of the shifted loads of heavy trucks (due to improper loading or liquid slosh) by pneumatic suspension design. In this regard, the pneumatically balanced suspension with dual leveling valves is introduced, and its potential for the improvement of the body imbalance due to the shifted load is determined. The analysis is based on a multi-domain model that couples the suspension fluid dynamics, shifted-load impacts, and tractor-semitrailer dynamics. Truck dynamics is simulated using TruckSim, which is integrated with the pneumatic suspension model developed in AMESim. This yields a reasonable prediction of the effect of the suspension airflow dynamics on vehicle dynamics. Moreover, the ability of the pneumatic suspension to counteract the effects of two general shifted loads - static (rigid cargo) and dynamic (liquid) - is studied. The simulation results indicate that the dual-leveling-valve suspension results in a reduction in roll angle and roll rate of the vehicle body for both static and dynamic load-shifting cases, as compared to the conventional single-leveling-valve suspension. Suppression of…
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A Simulation-Based Study on the Improvement of Semi-Truck Roll Stability in Roundabouts

Virginia Tech-Yunbo Hou, Yang Chen, Mehdi Ahmadian
Published 2016-09-27 by SAE International in United States
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. In this study, the cross-sectional geometry of circulatory roadway, a key roundabout segment, is studied to evaluate its effect on roll stability of a WB-67 semi-truck with three longitudinal load conditions, when the truck is equipped with conventional OE suspensions and a balanced pneumatic system. TruckSim is used to develop various configurations of roundabout models, as…
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Effects of Commercial Truck Configuration on Roll Stability in Roundabouts

Virginia Tech-Yunbo Hou, Mehdi Ahmadian
Published 2015-09-29 by SAE International in United States
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. Different paths followed by trucks to perform through-movement or left turns are simulated. The simulation results indicate that (1) traveling on a truck apron increases the risk of rollover, (2) different movements and paths result in different dynamic responses, and…
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Pneumatically Balanced Heavy Truck Air Suspensions for Improved Roll Stability

CVeSS, Virginia Tech.-Yang Chen, Mehdi Ahmadian, Andrew Peterson
Published 2015-09-29 by SAE International in United States
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. The pneumatic model is coupled with a roll-plane model of the truck to evaluate the effect of the suspension pneumatic dynamics on the body roll, as well as the force transmission to the sprung mass. The results of the study show that maintaining a…
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Integrating Electromechanical Systems in Commercial Vehicles for Improved Handling, Stability, and Comfort

SAE International Journal of Commercial Vehicles

Virginia Tech.-Mehdi Ahmadian
  • Journal Article
  • 2014-01-2408
Published 2014-09-30 by SAE International in United States
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. Controllable suspensions include an active or semiactive element-most commonly, damper-that enables changing the dynamic characteristics of the suspension in real time, to adapt to the instantaneous driving dynamics of the vehicle. Such suspensions most often use an electromagnetic actuator, mechanically adjustable damper, or magneto-rheological fluid to change the damping force at the suspension with sufficiently high dynamic bandwidth to respond to every bump and each steering maneuver of…
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Robust Optimal Control of Vehicle Lateral Motion with Driver-in-the-Loop

Virginia Tech-Seyed Hossein Tamaddoni, Saied Taheri, Mehdi Ahmadian
Published 2012-09-24 by SAE International in United States
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. A robust control strategy based on Integral Sliding Mode control is proposed to make the optimal controller robust to disturbances in the steering angles. The resultant robust optimal controller…
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Vehicle System Simulator: Development and Validation

SAE International Journal of Commercial Vehicles

Virginia Tech-Seyed Hossein Tamaddoni, Hedieh Alavi , Saied Taheri, Mehdi Ahmadian
  • Journal Article
  • 2011-01-2166
Published 2011-09-13 by SAE International in United States
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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Optimal Direct Yaw Controller Design for Vehicle Systems with Human Driver

SAE International Journal of Commercial Vehicles

Virginia Polytechnic Inst & State Univ-Saied Taheri
Virginia Tech-Mehdi Ahmadian
  • Journal Article
  • 2011-01-2149
Published 2011-09-13 by SAE International in United States
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. To evaluate the developed control algorithm, CarSim with its built-in nonlinear vehicle model along with the Pacejka tire model is used. The control algorithm is evaluated for a lane change maneuver, and the optimal set of steering angle and corrective yaw moment is calculated and fed to the…
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Linear Quadratic Game Theory Approach to Optimal Preview Control of Vehicle Lateral Motion

SAE International Journal of Passenger Cars - Mechanical Systems

Virginia Tech-Seyed Hossein Tamaddoni, Saied Taheri, Mehdi Ahmadian
  • Journal Article
  • 2011-01-0963
Published 2011-04-12 by SAE International in United States
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. The optimal preview feedback gains are obtained, and the resulting controllers are evaluated by the nonlinear vehicle model of CarSim7 for the standard lane change maneuver.
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Study on Squeeze Mode Magneto-Rheological Engine Mount with Robust H-Infinite Control

ASCL, Jilin University-Xinjie Zhang, Konghui Guo
University of Victoria-Hui Zhang
Published 2011-04-12 by SAE International in United States
Magneto-rheological fluid squeeze mode investigations at CVeSS have shown that MR fluids show large force capabilities in squeeze mode. A novel MR squeeze mount was designed and built at CVeSS, and a dynamic mathematical model was developed, which considered the inertial effect and was validated by the test data. A variant engine mount that will be used for isolating vibration, based on the MR squeeze mode is proposed in the paper. The mathematical governing equations of the mount are derived to account for its operation with MR squeeze mode. The design method of a robust H✓ controller is addressed for the squeeze mount subject to parameter uncertainties in the damping and stiffness. The controller parameter can be derived from the solution of bilinear matrix inequalities (BMIs). The displacement transmissibility is constrained to be no more than 1.05 with this robust H✓ controller. The MR squeeze mount has a very large range of force used to isolate the vibration.
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