Vladimir V. Vantsevich

Vehicle systems: coupled and interactive dynamics analysis

This article formulates a new direction in vehicle dynamics, described as coupled and interactive vehicle system dynamics. Formalised procedures and analysis of case studies are presented. An analytical consideration, which explains the physics of coupled system dynamics and its consequences for dynamics of a vehicle, is given for several sets of systems including: (i) driveline and suspension of a 6×6 truck, (ii) a brake mechanism and a limited slip differential of a drive axle and (iii) a 4×4 vehicle steering system and driveline system. The article introduces a formal procedure to turn coupled system dynamics into interactive dynamics of systems. A new research direction in interactive dynamics of an active steering and a hybrid-electric power transmitting unit is presented and analysed to control power distribution between the drive axles of a 4×4 vehicle. A control strategy integrates energy efficiency and lateral dynamics by decoupling dynamics of the two systems thus forming their interactive dynamics.

Road and off-road vehicle system dynamics. Understanding the future from the past

A detailed analysis of scientific research directions and methods in ground vehicle dynamics and vehicle system dynamics during the past century is presented in this article. What started as peculiarities of vehicle motion, dynamics of vehicles went through extensive research and engineering work and was established as an applied science – vehicle dynamics. Steady motion and transient manoeuvres, multi-flexible-body dynamics, nonlinear and stochastic dynamics, terramechanics, vehicle operational properties and their multi-criterion optimisation, computer modelling and simulation, analysis and optimal synthesis, various controls, inverse vehicle dynamics, open architecture-type, and multi-domain vehicle systems – these are the milestones of developments over the past century. This article considers the subject-matter and the substance of vehicle dynamics in general, and new research directions of modern vehicle dynamics in particular. It is shown that modern vehicle dynamics is acquiring principally new features including agile dynamics of multi-physics mechatronic systems (including cyber-type systems), coupled and interactive vehicle system dynamics.

Wheel Dynamics Fundamentals for Agile Tire Slippage Modeling and Control

One of the technical problems in wheel dynamics is to establish and control the relationship between the tire kinematic and force characteristics related to tire slippage and thus to tire-soil power losses and wheel mobility estimation. This problem has been attracting a lot attention from the research community for decades. The electronization of modern vehicles can enhance their performance in complex and severe vehicle-road/terrain environments by implementing agile control decision within the scale of milliseconds. Thus, agility requires new approaches when considering and analyzing the tire slippage process.This paper presents an analysis of the tire slippage process in stochastic terrain conditions for the purpose of agile tire slip modeling, estimation and control. Based on the introduced relations between the rolling radii of the tire, circumferential wheel force/wheel torque, wheel kinematic parameters and tire slippage, a set of agile tire-terrain characteristics is offered in the paper. The proposed characteristics take in consideration the rate of change of the listed parameters and thus allow a user to estimate the agile dynamics of the tire slip and evidence the closeness to the peak friction coefficient and hence estimate potential mobility loss. The characteristics establish relationships between the stochastic peak friction coefficient, rolling resistance coefficient, and wheel kinematic/force parameters. The characteristics are illustrated by computer simulation results in several terrain conditions.Copyright

AWD Vehicle Dynamics and Energy Efficiency Improvement by Means of Interaxle Driveline and Steering Active Fusion

This paper presents a novel approach to improve both energy efficiency and lateral dynamics of an all-wheel drive (AWD) vehicle by means of active functional/operational fusion of a driveline system, which distributes power between the front and rear driving axles, and a steering system that steers the front driving wheels.The paper starts by presenting the kinematic discrepancy factor, which is a normalized difference of the front and rear theoretical velocities that influences the wheel power distribution, as a mathematical function of the tire rolling radii in the driven mode, the gear ratios of the driveline system, and the steering angle of the front wheels. Using this function, the gear ratios from the transfer case to the front and rear wheels are determined to optimize vehicle energy efficiency by minimizing the kinematic discrepancy at the vehicle’s straight line motion and on a curve.It is also analytically shown that the wheel power distribution leads to the variation of the circumferential force of the front wheels that significantly influences the magnitude and direction of the front wheel lateral force. Thus, the paper introduced the wheel power distribution between the driving axles as an instrument for controlling oversteer-understeer transition of a vehicle, i.e., controlling vehicle lateral dynamics.Finally, the steering angle of the front wheels is considered and analyzed as an input of an active steering system to control the vehicle oversteer-understeer process in combination with the effect of the steering angle on the kinematic discrepancy factor. Longitudinal velocity control is added to constrain the lateral acceleration. Thus, the functional fusion of the active steering and driveline systems for enhancing both AWD vehicle energy efficiency and dynamics is introduced for the first time.Copyright

6x6 UGV: Stochastic Dynamics Fundamentals for Mobility Estimation

Stochastic modeling for mobility estimation has vastly improved through recent research and the advancements in technology, but those advancements haven’t fully been applied to full vehicle mobility control and on-line (real time) analysis of each driving wheel’s contribution and influence.This paper presents an analysis of fundamental mobility dynamics implemented into advanced stochastic estimation methodologies. Based on this analysis, the paper formulates: (i) developed on-line mobility criteria in stochastic conditions from one wheel to full vehicle with six driving wheels in which the contribution of every wheel can be estimated, and (ii) terrain characterization and agile vehicle dynamics information to estimate UGV mobility in real time.This analysis enables on-line mobility estimation for UGVs to make control changes as the event of poor terrain conditions occur (or before it) rather than after the event, causing the vehicle to then optimize its reaction to regain control. These fundamental applications for mobility control in stochastic conditions enable today’s one wheel modeling solutions to be applied to the full vehicle.© 2014 ASME

Mobility and Energy Efficiency of Military Tactical Vehicle With Hybrid-Electric Driveline System

In this paper, a technical concept is described for a power transmitting unit to control the split of power between the drive axles of a 4×4 hybrid-electric vehicle. This new power transmitting unit uses a planetary gear set and eddy current brake to provide a continuously variable gear ratio that can be integrated into the vehicle driveline between the transfer case and front axle. The paper details the electrical and mechanical characteristics of the device, including its operation mode, its mathematical model built from the equations of the planetary gear set and eddy current brake, the optimization equation by which the device will be controlled to improve vehicle slip efficiency, as well as its torque and electrical current usage. Computer simulations are performed on a mathematical model of a 4×4 military truck using the power transmitting unit in conjunction with a series hybrid-electric configuration transmission.Copyright

Driveline Configuration and Terrain Effect on Slippage and Efficiency of a 6×6/6×4 Truck

The power distribution between driving wheels has been shown to have a significant impact on vehicle energy efficiency, but there has only been limited research in this area. As shown in this paper, the wheel power distribution is largely dependent on the power dividing units (PDUs) which split/vector power between the driving wheels. The performance of a particular driveline system will also depend largely on the terrain conditions the vehicle encounters.This paper presents an analysis of PDU configurations in 6×6/6×4 terrain trucks. The vehicle efficiency is evaluated in a wide variety of typical operating conditions including varying surface types, speeds and accelerations, and slope conditions. An analytical method is presented which can be used to determine the tire circumferential forces and slippages. Finally, an analysis of the effects of the driveline configuration, terrain, and surface type on truck transportation efficiency is presented for three PDU combinations.© 2013 ASME

Tire-Terrain Normal and Longitudinal Dynamics and Slip Power Losses of an Unmanned Ground Vehicle

Studies of the tire-terrain interaction have mostly been completed on vehicles with steered wheels, but not much work has been done regarding skid-steered Unmanned Ground Vehicles (UGV). This paper introduces a mathematical model of normal and longitudinal dynamics of a UGV with four skid-steered pneumatic tire wheels. Unlike the common approach, in which two wheels at each side are treated as one wheel (i.e., having the same rotational speeds), all four wheels in this study are independently driven. Thus the interaction of each tire with deformable terrain is introduced as holonomic constraints.The stress-strain characteristics for tire-soil interaction are analyzed based on modern Terramechanics methods and then further used to determine the circumferential wheel forces of the four tires. Contributions of three components of each tire circumferential force to tire slippages are modeled and analyzed when the tire normal loads vary during vehicle straight-line motion. The considered tire-soil characteristics are mathematically reduced to a form that allows condensing the computational time for on-line computing tire-terrain characteristics. Additionally, rolling resistance of the tires is analyzed and incorporated in the UGV dynamic equations.Moreover, the paper describes the physics of slip power losses in the tire-soil interaction of the four tires and applies it to small skid-steered UGV. This study also formulates an optimization problem of the minimization of the power losses in the tire-soil interactions due to the tire slippage.Copyright

Indices and Computational Strategy for Unmanned Ground Wheeled Vehicle Mobility Estimation and Enhancement

The United States Army began developing Unmanned Ground Vehicles (UGV) in the early 1900’s. Concurrently, researchers developed and enhanced passenger and commercial ground vehicles. Although significant progress has been made for improving vehicle mobility for all ground vehicles throughout the past century, mobility has lacked a concise mutually agreed definition and analytical standardized criteria. The implementations of improved technologies, such as vehicle traction control, stability control, and torque vectoring systems require researchers to take a step back and reevaluate mobility criteria. UGVs require additional enhancement to include on-line mobility estimation since the vehicle cannot predict nor anticipate terrain conditions on their own prior to the vehicle traversing those conditions.This paper analyzes methodologies researchers have employed for defining and improving vehicle mobility of wheeled vehicles. The analysis is done from a view point of concurrent mobility methodologies’ enhancement and applicability to wheeled UGVs.This analysis is then used to develop off-line and on-line analytical criterion for mobility estimation, and to derive a strategy which can be applied to wheeled vehicles, both manned and unmanned. The on-line mobility estimation enables the UGV to make control changes as the events occur rather than after the event, causing the vehicle to then optimize its reaction to regain control.Copyright

Interaction between autonomous vehicles and road surface

Todays studies in Vehicle Dynamics are becoming increasingly isolated from one another. They relate to different systems of a vehicle and do not demonstrate an interconnection between these systems. For example, mechatronic systems to control the circumferential wheel forces of vehicles can be divided into two groups: systems of the first group act through the brake system and throttle, and the second groups systems act through the drivetrain. Systems of both groups are not interconnected with one another. This approach is not conducive to moving ahead in the development of novel systems, such as autonomous vehicles. A new approach has been proposed to overcome these difficulties. The proposed approach in vehicle dynamics is aimed at the control of the vehicle properties. Developing of a new direction in vehicle dynamics requires a mathematical model, which would allow design engineers to control the interaction between a wheel and road surface in three dimensions – the normal, longitudinal, and lateral ones. However, the interaction in the real-life system is so complex that a model would be equally complex and thus unmanageable or prohibitively expensive. The development of such a model that would include a certain minimal set of the systems characteristics so that the model approximates the real system yet remains cost-effective and manageable and meets engineering needs, is the aim of this paper.