The Experts below are selected from a list of 165 Experts worldwide ranked by ideXlab platform
Noel C. Perkins - One of the best experts on this subject based on the ideXlab platform.
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A Super-Element of Track-Wheel-Terrain Interaction for Dynamic Simulation of Tracked Vehicles
Multibody System Dynamics, 2006Co-Authors: Zheng-dong Ma, Noel C. PerkinsAbstract:A track-wheel-terrain interaction model is presented in this paper, which can be used as a “force” super-element in a multibody dynamics code for dynamic simulation of tracked vehicles. This model employs a nonlinear finite element representation for the track segment that is in contact with the terrain and Roadwheels, which can be used to simulate two different track systems, namely a continuous rubber band track and a multi-pitched metallic track, provided the finite element mesh in the track model is properly defined. The new track model accounts for the tension variations along the track (due to the non-uniformly distributed normal pressure and traction), track extensibility, and geometrically large (nonlinear) track deflections. A new solution algorithm is then proposed that includes an adaptive meshing method for representing track movement during the simulation for the multi-pitch tracks. Doing so produces a track model that captures high-frequency content of the track-wheel-terrain interaction, and it can more accurately describe the mechanics of a multi-pitch track as the vehicle negotiates rough terrain. The resulting track-wheel-terrain model combines approximate and known constitutive laws for terrain response with the new track representation, which allows the computation of the normal and shear forces, as well as the passage frequency, at the track-terrain interface. The track model and solution algorithm are further illustrated in this paper using a simple two-wheel system model and a full vehicle model of an M1A1 tank.
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A Track-Wheel-Terrain Interaction Model for Dynamic Simulation of Tracked Vehicles
Vehicle System Dynamics, 2002Co-Authors: Noel C. PerkinsAbstract:A mathematical model of track-wheel-terrain interaction is presented that supports the dynamic simulation of tracked vehicles. This model combines approximate and known constitutive laws for terrain response with a new representation for the track segment. The resulting track-wheel-terrain model allows the computation of the track tension and the normal and shear forces at the track-terrain interface as the track negotiates terrain of arbitrary profile. A key feature of this model is the uniform treatment of contact between the track and the Roadwheels and the track and the terrain. Treating both contact problems in the same manner significantly simplifies the problem formulation and also reduces difficulties in computing points of track-wheel and track-terrain separation. The model takes the form of a two-point nonlinear boundary value problem that accounts for tension variations along the track (due to the non-uniformly distributed normal pressure and traction), track extensibility, and geometrically la...
J.y. Wong - One of the best experts on this subject based on the ideXlab platform.
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Computer-Aided Method RTVPM for Evaluating the Performance of Vehicles with Long-Pitch Link Tracks
Terramechanics and Off-Road Vehicle Engineering, 2010Co-Authors: J.y. WongAbstract:Publisher Summary A computer-aided method—RTVPM—has been developed to provide a comprehensive method for design and performance evaluation of tracked vehicles with relatively long-pitch link tracks. RTVPM takes into account all major design parameters of the vehicle, including the vehicle weight, location of the center of gravity, number of Roadwheels, Roadwheel dimensions and spacing, locations of the sprocket and idler, supporting roller arrangements, track width, track pitch, initial track tension, and drawbar hitch location. The prime objective for the development of RTVPM is to establish an analytical procedure with which the interaction between the long-pitch link track and the terrain under steady-state operating conditions may be predicted in a realistic manner. In the analysis, the track system is divided into four sections: the upper run of the track supported by rollers, sprocket, and idler; and the lower run of the track in contact with the terrain; the section in contact with the idler; and the section in contact with the sprocket. The tractive performances of the three track system configurations with tracks of various pitches predicted using RTVPM indicates that for given overall dimensions of a track system, the ratio of Roadwheel spacing to track pitch is one of the design parameters that have significant effects on its tractive performance.
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Computer-Aided Method NTVPM for Evaluating the Performance of Vehicles with Flexible Tracks
Terramechanics and Off-Road Vehicle Engineering, 2010Co-Authors: J.y. WongAbstract:A computer-aided method known as NTVPM has been developed for vehicles with link tracks having relatively short track pitch or with rubber belt (band) tracks. NTVPM is based on a detailed analysis of the physical nature of track–terrain interaction and on the principles of terramechanics. It focuses on the prediction of the normal and shear stress distributions on the track–terrain interface under steady-state operating conditions, from which the tractive performance of a tracked vehicle is evaluated. It can be used to predict the mobility of single-unit or two-unit articulated tracked vehicles. The characteristics of Roadwheel suspensions are fully taken into consideration in NTVPM. Pivot-arm suspensions, such as torsion bar suspensions and hydro-pneumatic suspensions, and translational spring suspensions, with linear or nonlinear load–deflection characteristics, can be simulated. The nonlinear behavior of the suspension may be characterized using a polynomial up to the fifth order. NTVPM provides the engineer with a comprehensive and realistic tool for performance, and design evaluation of vehicles with flexible tracks, from a traction perspective. It has been successfully employed by off-road vehicle manufacturers in the development of new products and by governmental agencies in the evaluation of vehicle candidates in North America, Europe, and Asia.
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Characterization of the Shearing Behaviour of Terrains
Terramechanics and Off-Road Vehicle Engineering, 2010Co-Authors: J.y. WongAbstract:This chapter describes the results of the measurement and characterization of the shearing behavior of a variety of terrains, including mineral terrain, muskeg, and snow-covered terrain. The measurements are made using a vehicle-mounted bevameter with the associated computerized data acquisition and processing system. When a multiaxle wheeled vehicle (or a tracked vehicle) is in straight-line motion over an unprepared terrain, an element of the terrain is subject to the repetitive shearing of the consecutive wheels (or Roadwheels). In order to predict the shear stress distribution on the vehicle–terrain interface, the response to repetitive shear loading of the terrain should be known. The response of a frictional terrain (a dry sand) to repetitive shear loading under a constant normal load indicates that when the shear loading is reduced to zero and is then reapplied, the shear stress–displacement relationship during reshearing is similar to that when the terrain is being sheared in its virgin state. The variation of the shearing force beneath a rectangular shear plate on dry sand subject to a vertical harmonic load with a frequency of 10.3 Hz indicates that during the loading portion of each cycle, the shearing force S does not reach its maximum value instantaneously.
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optimization of design parameters of rigid link track systems using an advanced computer aided method
Proceedings of the Institution of Mechanical Engineers Part D: Journal of Automobile Engineering, 1998Co-Authors: J.y. WongAbstract:This paper describes the applications of a computer aided method known as RTVPM to the selection and optimization of the basic design parameters of track systems with rigid links, commonly in use in agricultural and industrial vehicles. It is found that the ratio of Roadwheel spacing to track pitch is a significant parameter that affects the tractive performance, particularly on soft terrain. For a given track system configuration and Roadwheel spacing, it is important to select an appropriate track pitch to ensure good tractive performance on the one hand and minimal vehicle speed fluctuation on the other. It is also shown that the initial track tension has a considerable effect on tractive performance when the ratio of Roadwheel spacing to track pitch is high and that its effect decreases with the decrease of the Roadwheel spacing to track pitch ratio. The effect on tractive performance of the ratio of Roadwheel spacing to track pitch becomes less significant with the increase of soil strength. It is demonstrated that by selecting the appropriate ratio of Roadwheel spacing to track pitch, initial track tension, location of the centre of gravity and other design parameters, an optimum track system configuration for a given operating environment can be evolved.
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On the role of mean maximum pressure as an indicator of cross-country mobility for tracked vehicles
Journal of Terramechanics, 1994Co-Authors: J.y. WongAbstract:Abstract The role of mean maximum pressure (MMP) as an indicator of cross-country mobility is reviewed. The values of MMP under a tracked vehicle are predicted using an empirical formula proposed by Rowland and a computer-aided method, known as NTVPM-86. It is shown that values predicted using NTVPM-86 are in closer agreement with measured data than those predicted using Rowland's formula. The variations of MMP with vehicle weight, track width, number and diameter of Roadwheels are predicted using both methods over a clayey soil, snow and muskeg. It is found that in most cases, there is a significant difference in the values of MMP predicted using the two methods. It is also shown that Rowland's method takes into account only a limited number of vehicle design parameters and that it can only be employed to predict vehicle mobility in a qualitative manner. On the other hand, NTVPM-86 takes into account all major vehicle design features and terrain characteristics and can be used to predict quantitatively vehicle tractive performance over soft terrain. It is hoped that this paper will stimulate vehicle engineers in the use of advanced computer-aided methods in their practice and that it will encourage further research in this vital area.
J.h. De Klerk - One of the best experts on this subject based on the ideXlab platform.
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Mathematical modelling of the interaction between a tracked vehicle and the terrain
Applied Mathematical Modelling, 1996Co-Authors: D.j. Van Wyk, J. Spoelstra, J.h. De KlerkAbstract:Abstract A new mathematical model for the forces on the track of a tracked vehicle moving over terrain with semielastic behavior is constructed. This model is in the form of systems of differential equations: a system governing the forces on those parts of the track in contact with Roadwheels, and another system for the parts in contact with the terrain but not with a wheel. The intervals on which the different systems have to be solved are in themselves determined by the solutions to the systems. This problem is solved numerically and the numerical results are presented.
Jerzy Ejsmont - One of the best experts on this subject based on the ideXlab platform.
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Engineering method of tire rolling resistance evaluation
Measurement, 2019Co-Authors: Jerzy Ejsmont, Wojciech OwczarzakAbstract:Abstract Tire rolling resistance is one of the most difficult tire parameters to measure. The reason is that for modern tires the force of rolling resistance corresponds to 0.5–1% of tire load, thus measurements of very small forces must be performed in a heavily loaded system. This constitutes great problems, especially in road conditions. Laboratory measurements are easier to perform, as the environment may be better controlled, but Roadwheel facilities based on outer drums, in general cannot be equipped with real road pavements. Typically they have steel drums or drums covered by replicas at best. This article describes a laboratory method of rolling resistance evaluation that may be used in preliminary assessment of road pavements (based on small pavement samples) and tires. The method is based on impact induced tire oscillations and gives good ranking of tires and road pavements related to the energy losses that control rolling resistance.
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The influence of road surface unevenness on tyre rolling resistance
2015Co-Authors: Jerzy Ejsmont, Grzegorz Ronowski, Stanisław Taryma, Beata Świeczko-ŻurekAbstract:The geometric characteristics of road surface substantially affect the interaction between tyre and road. Depending on pavement texture wavelength, the texture chiefly affects tyre/road friction, rolling resistance, interior and exterior noise, tyre wear, and ride comfort. The article presents results of investigations on the influence of road surface unevenness on the rolling resistance of passenger car and truck tyres. The tests were carried out on a Roadwheel facility being a part of the test equipment of the Automotive Tyre Testing Laboratory of the Gdansk University of Technology, where a specially made replica road surface with a sinusoidal unevenness profile was mounted on the drum, and on a test road. The unevenness profile under test was characterized by a wavelength of 0.8 m and amplitude of 10 mm, which corresponded to the road surface type commonly referred to as “washboard”. The objective of the experiments was to ascertain whether the increase in rolling resistance observed on uneven road surfaces is exclusively caused by an increase in the energy losses in suspension system damping elements or the energy losses in the tyre actually rise as well. The tests revealed that, on the sinusoidal road surface as defined above in comparison with the “Safety Walk” smooth sandpaper like surface, the rolling resistance of passenger car tyres grew by about 10 % and rolling resistance of truck tyres increased about 30 %.
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LOW NOISE TIRES FOR HYBRID AND ELECTRIC VEHICLES
2014Co-Authors: Jerzy Ejsmont, Beata Świeczko-Żurek, Stanisław TarymaAbstract:Low Emission Vehicles that are hybrid and electric cars may benefit from specially designed tires that are optimized for driving conditions typical for such vehicles. It is possible that in the future Low Emission Vehicles, especially passenger cars, will substitute conventional vehicles in all applications, however for the time being they are mostly used in urban and suburban areas. Urban traffic has a rather low demand for grip performance of tires due to relatively low speeds. At the same time it imposes high demands for low noise emission of tires, as traffic noise is one of the most difficult environmental problem in towns. For electric vehicles there is also a very high need to ascertain necessary vehicle's range of operation by lowering the rolling resistance of tires as much as possible. The paper discusses selected aspects of hybrid and electric tires’ use and presents results of noise measurements performed for tires that are specially designed for LEV's or that are commonly used in such vehicles. The measurements were performed both at the laboratory using Roadwheel facilities with drums covered by replica road surfaces and on the road by the Close Proximity Method. As supplementary information, to prove that there is no conflict between low noise and low rolling resistance tires, rolling resistance of tested tires is presented.
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Comparison of road and laboratory measurements of tyre/road noise
2014Co-Authors: Beata Świeczko-Żurek, Grzegorz Ronowski, Jerzy Ejsmont, Stanisław TarymaAbstract:Tyre/road noise is one of the major environmental problems related to road traffic. There are several measuring methods of tyre/road noise that may be carried out on the road (for example Coast-down and Close Proximity Method) or in the laboratory (Drum Method). Road measurements are preferred for evaluations of pavement properties while laboratory methods are mostly used to evaluate tyres. One of the biggest problems associated with laboratory methods is to ascertain that tyre interfaces with pavement that has texture, porosity and mechanical impedance the same as with the real road surface. The paper presents results of tests performed by the Close Proximity Method (with test trailer Tiresonic Mk.4) and drum method where very similar or exactly the same surfaces are used. The reported measuring program includes tests performed on an innovative poroelastic road surface called PERS. Tyre/road noise is nowadays one of the most important issues related to the tyre and road interface. Intensive investigation of noise generated by rolling tyres started in the sixties of the twentieth century. At that time every researcher used his/her own methodology of measurements so comparison of the results was not easy. Basically two different groups of measuring methods started to evaluate after a while. One group, preferred by tyre manufacturers was based on indoor measurements with use of Roadwheel (drum) facilities, and road measurements preferred by road constructors and road authorities. Drum measurements were relatively easy to perform and all measuring conditions were straightforwardly controllable, with exception of pavement characteristics. A lot of early measurements were made on plain steel drums or at the best on drums covered with sand-paper like material called "Safety Walk". Of course results obtained on plain steel surface or "Safety Walk" were not at all representative to real road conditions but equipping drums with replica road surfaces was very difficult and expensive. Road measurements at first were based on ISO 362 standard that was intended to evaluate overall noise from different types of vehicles. In order to separate noise generated by tyre/road interaction from other noise sources the acceleration pass-by required by the standard was being replaced by coast-by. In the 1970s first trailers intended for tyre/road noise measurements began to appear (1, 2). At present, the following methods are in use: the Drum Method (tyre rolls on the test drum, usually on its outer surface that is covered by replica road surfaces having the same texture as real road pavement of a certain kind, microphones are placed close to the tyre/pavement interaction zone); the Coast-By Method (vehicle equipped with test tyres coasts-down on the test pavement, microphones are placed 7.5 m or 15 m from the centre of the test track); the Close Proximity Method "CPX" (test tyre is mounted on trailer or on ordinary vehicle and the microphones are mounted "on-board", very close to the tyre/road interaction zone; the Trailer Coast-By (a hybrid method using a specially designed trailer that coasts-by during measurements and microphones positioned on the road side). All measurements reported in this paper were performed on facilities owned by the Technical University of Gdansk, Poland. Laboratory tests were performed on three different drum facilities:
J. Christian Gerdes - One of the best experts on this subject based on the ideXlab platform.
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Intelligent Vehicles Symposium - Creating predictive haptic feedback for obstacle avoidance using a model predictive control (MPC) framework
2015 IEEE Intelligent Vehicles Symposium (IV), 2015Co-Authors: Avinash Balachandran, Stephen M. Erlien, Matthew Brown, J. Christian GerdesAbstract:New sensing technologies allow modern vehicles to perceive the environment around them even when human visual perception is limited due to poor lighting or fog. Steer-by-wire technology enables active steering capability in which the driver's command to the Roadwheels is augmented for maintaining safety. Predictive controllers can leverage both of these technologies to create shared control safety systems that work with the driver to ensure a safe and collision-free vehicle trajectory. The earlier the system intervenes, the smoother the intervention but the more it interferes with the driver's control authority. Ideally, predictive controllers should still intervene late but also indicate upcoming environmental threats to the driver as early as possible. Haptic feedback provides a good means of communicating information to the driver early. Together with a controller still providing a late intervention fallback, this regime provides an ideal framework for predictive shared control systems. This paper presents a novel technique for creating haptic steering feedback, based on future differences between the predictive controller and the driver. This feedback mirrors the tension between the sometimes competing controller objectives of following the driver and maintaining a feasible path. The paper uses simulation and experiment to investigate the inherent trade-offs of predictive haptic feedback and qualitatively discuss its impact.
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The Virtual Wheel Concept for Supportive Steering Feedback During Active Steering Interventions
Volume 2: Dynamic Modeling and Diagnostics in Biomedical Systems; Dynamics and Control of Wind Energy Systems; Vehicle Energy Management Optimization;, 2014Co-Authors: Avinash Balachandran, Stephen M. Erlien, J. Christian GerdesAbstract:Active steering systems allow for improved vehicle safety and stability through steering interventions that augment a driver’s steering command. In a conventional steering system, steering feedback torque depends on the tire forces and corresponding moments that act on the Roadwheels. During active steering interventions, there are differences between the driver’s command and the actual Roadwheel angle. The steering feedback can now be based on either the moments acting on the actual Roadwheels or the moments acting on a virtual wheel following the driver’s intended steering command. With small interventions, the difference between these two approaches is negligible. However, when the intervention is large (e.g. obstacle avoidance maneuvers), basing handwheel moments on the actual Roadwheel position results in a handwheel torque that acts in opposition to the intervention. The virtual wheel concept produces a more supportive, and potentially more intuitive, handwheel torque. This reduces the discrepancy between the driver command and the active steering system in simulation and experiments.© 2014 ASME
