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Considering that tires play a vital role not only in the performance but also in the safety of a vehicle, studying the tire-road interaction has always been a matter of interest, specifically when the tire is travelling on icy roads.... more
Considering that tires play a vital role not only in the performance but also in the safety of a vehicle, studying the tire-road interaction has always been a matter of interest, specifically when the tire is travelling on icy roads. However, most of the existing studies focused on tire performance on ice for traction or braking conditions [1,2] and not many studies have been devoted to the free rolling of a tire. Considering the tire in its free rolling condition is a necessary step in assessing the friction force at the tire-ice interface, which can be used next to predict the torque to be applied on the tire in order to create a zero slip condition in the tire-ice contact patch. The zero slip condition is always difficult to obtain, as it needs a very accurate assessment of the effective rolling radius of the tire. This study is a part of a more comprehensive study to investigate the effects of different tire parameters, such as rubber compounds properties on tire performance on ...
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Mechanical and thermal properties of the rubber compounds of a tire play an important role in the overall performance of the tire when it is in contact with the terrain. Although there are many studies conducted on the properties of the... more
Mechanical and thermal properties of the rubber compounds of a tire play an important role in the overall performance of the tire when it is in contact with the terrain. Although there are many studies conducted on the properties of the rubber compounds of the tire to improve some of the tire characteristics, such as the wear of the tread, there are a limited number of studies that focused on the performance of the tire when it is in contact with ice. This study is a part of a more comprehensive project looking into the tire-ice performance and modeling. In this study, to understand the effect of different rubber compounds on the tire performance, three identical tires from the same company have been chosen. The tires’ only difference is the material properties of the rubber. Two approaches have been implemented in this study. For the first approach, several tests were conducted for the chosen tires at Terramechanics, Multibody, and Vehicle Systems (TMVS) laboratory at Virginia Tech to compare their performance experimentally. For the second approach, a tire-ice model has been used to compute the height of the water film created at the contact patch. As will be shown in this study, an increase in the height of water film results in a decrease in the friction coefficient, which is one of the most critical parameters for the tire performance. By having this knowledge, the performance of the three tires considered in the study was compared using the developed tire-ice model, based on the values obtained for the height of the water film. It is shown that the results obtained by simulation coincide with the results obtained experimentally. The results from this study show the sensitivity of the magnitude of the tractive force with respect to parameters such as tire temperature, normal load, etc. The results also indicate that the tire with the lowest value of Young’s modulus has the highest traction among all three tires used in this study.
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It is very important for designers to ensure the safety and usability of products. In this paper, a gap model between designers and users is first proposed as a framework to detect problems in safety and usability and to analyze the... more
It is very important for designers to ensure the safety and usability of products. In this paper, a gap model between designers and users is first proposed as a framework to detect problems in safety and usability and to analyze the causes. Then methods to describe operations on a product, simulate its behavior as state transitions, and detect safety and effectiveness gaps based on temporal intervals and their qualitative relationships are proposed. The proposed methods are implemented in a gap analysis program (GAP), which is used to analyze the operations of a tractor by eight general participants and four employees of a tractor-manufacturer. As a result, potential safety and effectiveness gaps are correctly detected.
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The mobility of vehicles in off-road environments is critical for many applications. Understanding and predicting the tire-soil interaction is a challenge, especially when the terrain is largely deformable and plastic, and non-linear... more
The mobility of vehicles in off-road environments is critical for many applications. Understanding and predicting the tire-soil interaction is a challenge, especially when the terrain is largely deformable and plastic, and non-linear behavior is expected. This paper presents an overview of the bibliographic references on tires–deformable soil interactions and identifies the gaps present in the literature. The capabilities and challenges of different modeling methods used to assess the traction performance of a vehicle on deformable soil (i.e., analytical, semi-empirical, and numerical are discussed. Also, since the performance of the vehicle highly depends on the soil characteristics, a summary of the different material models used for non-cohesive and cohesive soil and the methods that have been used to characterize the soil is presented. The soil behavior and strength also depend on the water content and permeability along with the soil type. To highlight this, the available works...
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Tire footprint properties have important effects on tire-road contact pressure distribution and, consequently, on the general performance of the tire when it is in contact with the road. Most of the research conducted in this area is... more
Tire footprint properties have important effects on tire-road contact pressure distribution and, consequently, on the general performance of the tire when it is in contact with the road. Most of the research conducted in this area is related to the tire performance under static loading conditions. Past studies show that the slip ratio of the tire plays a significant role on tire footprint characteristics. In this study, to account for the effect of the tire footprint characteristics on the tire performance, a finite element tire model with detailed tread pattern (similar to the tire 205/55R16 used for testing and modeling) has been developed using ABAQUS software. The model has been validated using the experimental methods for both footprint dimensions and vertical stiffness values. The comparison of the results from experiment and simulation show a satisfying agreement within 3.6% error. The model has next been used to simulate tire-road interaction for both, static loading conditi...
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Abstract Tire tractive performance, soil behavior under the traffic, and multi-pass effect are among the key topics in the research of vehicle off-road dynamics. As an extension of the study (He et al., 2019a), this paper documents the... more
Abstract Tire tractive performance, soil behavior under the traffic, and multi-pass effect are among the key topics in the research of vehicle off-road dynamics. As an extension of the study (He et al., 2019a), this paper documents the testing of a tire moving on soft soil in the traction mode or towing mode, with a single pass or multiple passes, and presents the testing results mainly from the aspects of tire tractive performance parameters, soil behavior parameters, and multi-pass effect on these parameters. The influence of tire inflation pressure, initial soil compaction, tire normal load, or the number of passes on the test data has been analyzed; for some of the tests, the analysis was completed statistically. A multi-pass effect phenomenon, different from any phenomenon recorded in the available existing literature, was discovered and related to the ripple formation and soil failure. The research results of this paper can be considered groundwork for tire off-road dynamics and the development of traction controllers for vehicles on soft soil.
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ABSTRACT
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ABSTRACT
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Abstract This study addresses the critical need for computational tools to model complex nonlinear multibody dynamic systems in the presence of parametric and external uncertainty. Polynomial chaos has been used extensively to model... more
Abstract This study addresses the critical need for computational tools to model complex nonlinear multibody dynamic systems in the presence of parametric and external uncertainty. Polynomial chaos has been used extensively to model uncertainties in ...
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ABSTRACT
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Many parameters in mechanical systems cannot be measured physically with good accuracy, which results in parametric and external excitation uncertainties. This paper compares two new computational approaches for parameter estimation. The... more
Many parameters in mechanical systems cannot be measured physically with good accuracy, which results in parametric and external excitation uncertainties. This paper compares two new computational approaches for parameter estimation. The first approach is a polynomial-chaos based Bayesian approach in which maximum likelihood estimates are obtained by minimizing a cost function derived from the Bayesian theorem. The second one uses an Extended Kalman Filter (EKF) to obtain the polynomial chaos representation of the uncertain states and the uncertain parameters. The two methods are illustrated on a nonlinear four degree of freedom roll plane vehicle model, where an uncertain mass with an uncertain location is added on the roll bar. Both approaches can work with noisy measurements and yield results close to the actual values of the parameters, except when different combinations of uncertain parameters lead to essentially the same time response than the measured response. In that case, the aposteriori probability densities of the estimated parameters obtained with the EKF approach cannot be trusted. The Bayesian approach identifies that problem since the Bayesian cost function has an entire region of minima, and can use regularization techniques to yield most likely values in that region based on apriori knowledge.
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Research Interests: Engineering, Mechanical Engineering, Civil Engineering, Mathematics, Monte Carlo, and 15 moreA Priori Knowledge, Decision Theory, Bayesian statistics, Estimation, Design Methodology, Mechanical systems, Mathematical Optimization, Interdisciplinary Engineering, Engineering Computations, Cost Function, Explicit, Mechanical, Bayesian framework, Bayesian Estimator, and maximum likelihood estimate
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... Corina Sandu is an Associate Professor of Mechanical Engineering at Virginia Tech. She received her Engineering Diploma in 1991 from the Bucharest Polytechnic Institute, MS in 1995 and PhD in 2000 in Mechanical Engineering from the... more
... Corina Sandu is an Associate Professor of Mechanical Engineering at Virginia Tech. She received her Engineering Diploma in 1991 from the Bucharest Polytechnic Institute, MS in 1995 and PhD in 2000 in Mechanical Engineering from the University of Iowa. ...
Research Interests: Engineering, Mechanical Engineering, Structural Engineering, Rheology, Automotive Engineering, and 10 moreControllability, Correlation, Acceleration, Experimental Evaluation, Suspension, Magnetorheological Fluid based Structures, Magnetorheological dampers, Shock Wave, Damper, and Vehicle suspension
The primary purpose of this study is to provide a comprehensive experimental analysis of how various popular semiactive control methods perform when used with magneto rheological dampers. Specifically, the performance of five different... more
The primary purpose of this study is to provide a comprehensive experimental analysis of how various popular semiactive control methods perform when used with magneto rheological dampers. Specifically, the performance of five different skyhook control methods is studied experimentally, using a single suspension test rig. The control methods that are analyzed include: skyhook control, groundhook control, hybrid control, displacement skyhook,
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This study addresses the critical need for computational tools to model complex nonlinear multibody dynamic systems in the presence of parametric and external uncertainty. Polynomial chaos has been used extensively to model uncertainties... more
This study addresses the critical need for computational tools to model complex nonlinear multibody dynamic systems in the presence of parametric and external uncertainty. Polynomial chaos has been used extensively to model uncertainties in structural mechanics and in fluids, but to our knowledge they have yet to be applied to multibody dynamic simulations. We show that the method can be applied to quantify uncertainties in time domain and frequency domain.
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Research Interests: Mathematics, Differential Algebra, Stochastic Process, Computer Science, Monte Carlo Simulation, and 11 moreMonte Carlo, Mathematical Sciences, Chaotic Dynamics, Physical sciences, Multibody Dynamics, Polynomial Chaos, Model Complexity, Terrain Modeling, Frequency Domain, Karhunen-Loeve Expansion, and Generalized polynomial chaos
Research Interests: Mathematics, Differential Algebra, Computer Science, Monte Carlo Simulation, Monte Carlo, and 15 moreMathematical Sciences, Chaotic Dynamics, Physical sciences, Multibody Dynamics, Discretization, Nonlinear system, Polynomial Chaos, Parametric Statistics, Model Complexity, Multi Dimensional, Frequency Domain, Engineering System, Generalized polynomial chaos, Parametric Uncertainty, and Polynomial
Parameter estimation for large systems is a difficult problem, and the solution approaches are computationally expensive. The polynomial chaos approach has been shown to be more efficient than Monte Carlo for quantifying the effects of... more
Parameter estimation for large systems is a difficult problem, and the solution approaches are computationally expensive. The polynomial chaos approach has been shown to be more efficient than Monte Carlo for quantifying the effects of uncertainties on the system response. This article compares two new computational approaches for parameter estimation based on the polynomial chaos theory for parameter estimation: a Bayesian approach, and an approach using an extended Kalman filter (EKF) to obtain the polynomial chaos representation of the uncertain states and the uncertain parameters. The two methods are applied to a non-linear four-degree-of-freedom roll plane model of a vehicle, in which an uncertain mass with an uncertain position is added on the roll bar. When using appropriate excitations, the results obtained with both approaches are close to the actual values of the parameters, and both approaches can work with noisy measurements. The EKF approach has an advantage over the Bayesian approach: the estimation comes in the form of a posteriori probability densities of the estimated parameters. However, it can yield poor estimations when dealing with non-identifiable systems, and it is recommended to repeat the estimation with different sampling rates in order to verify the coherence of the results with the EKF approach. The Bayesian approach is more robust, can recognize non-identifiability, and use regularization techniques if necessary.
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This study developed and implemented an efficient computational method to propagate uncertainties through black-box models of mechanical systems. The system of interest was a wheel loader, but the methodology developed can be applied to... more
This study developed and implemented an efficient computational method to propagate uncertainties through black-box models of mechanical systems. The system of interest was a wheel loader, but the methodology developed can be applied to various multibody systems. The technique implemented focused on efficiently modeling stochastic systems for which the equations of motion (EOMs) are not available. The analysis targeted the reaction forces in joints of interest. To validate the stochastic method proposed, it was implemented on a simple linkage mechanism modeled in two different ways: i) using differential algebraic equations (DAEs) coded in Matlab, and ii) using computer aided design (CAD) in ProMechanica (the so-called black-box model). A stochastic model of the simple mechanism was developed using a Monte Carlo approach and a linear/quadratic transformation method, to serve for benchmarking purposes. A collocation method based on the polynomial chaos methodology was then developed for both Matlab and ProMechanica models. The method was validated on the simple linkage mechanism model using the results from the models obtained earlier using traditional stochastic techniques. It was next applied to a complex ProMechanica CAD model of a Cat Wheel Loader. The collocation method implemented proved to be reliable and easier to implement than traditional stochastic methods. Moreover, it has been shown that it can be successfully applied to black-box models
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... DOI: 10.4271/2006-01-3481. Author(s): BJ Chan - Virginia Polytechnic Institute and State University C. Sandu - Virginia Polytechnic Institute and State University M. Ahmadian - Virginia Polytechnic Institute and State University. ...
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This study investigates a control methodology for dynamic systems based on representing all possible system responses under all possible values of the control variables. The underlying idea is to extend the system along the “control... more
This study investigates a control methodology for dynamic systems based on representing all possible system responses under all possible values of the control variables. The underlying idea is to extend the system along the “control dimension” and explicitly account for the dependence of the system state on control variables. A spectral discretization along the “control dimension” is employed. The optimal control values are chosen to obtain the desired system response. Numerical studies for the control of linear and nonlinear quarter car models riding on various terrain profiles show promising results.
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Research Interests: Engineering, Computer Science, Monte Carlo, Collocation, Estimation Theory, and 15 moreParameter estimation, Kalman Filter, Case Study, Method, Estimation, Parameter Identification, Computational Efficiency, Filter, Kalman, Extended Kalman Filter, Off Road Vehicle, Degree of Freedom, Parameter, Monte Carlo Method, and Polynomial
The numerical dynamic simulation of a full vehicle incorporating a magneto-rheological (MR) damper in the primary suspension is studied using the automatic dynamic analysis package ADAMS and the control software SIMULINK. The full vehicle... more
The numerical dynamic simulation of a full vehicle incorporating a magneto-rheological (MR) damper in the primary suspension is studied using the automatic dynamic analysis package ADAMS and the control software SIMULINK. The full vehicle model is built under ADAMS. The interaction between the tire and the road profile is simulated using the ADAMS/TIRE capabilities. The UA tire model is used to model the dynamic characteristics of the tires. A 3-D road profile model is built based on the spatial power spectrum density of a random road profile. This road profile satisfies not only some random distribution law, but also adapts to the numerical simulation requirement of the tire model. In order to model the dynamic characteristics of the primary suspension MR damper, a non-parametric model of an MR damper is proposed which can conveniently be incorporated into the vehicle dynamic model. Two kinds of control policies, a common skyhook and the so-called ‘non-jerk’ skyhook, are adopted to control the current applied to the MR damper. The simulation results imply that either one of the two skyhook control policies can obtain a good compromise between so-called “soft damping” and “hard damping,” and non-jerk skyhook control policy can curb some higher frequency components which are observed in the acceleration response of the chassis. This study also shows that virtual prototype technology is an effective approach for investigating the dynamic behavior of MR dampers for complex systems.