Showing papers on "Vehicle dynamics published in 2003"

Dynamic camera calibration of roadside traffic management cameras for vehicle speed estimation

Abstract: In this paper, we present a new three-stage algorithm to calibrate roadside traffic management cameras and track vehicles to create a traffic speed sensor. The algorithm first estimates the camera position relative to the roadway using the motion and edges of the vehicles. Given the camera position, the algorithm then calibrates the camera by estimating the lane boundaries and the vanishing point of the lines along the roadway. The algorithm transforms the image coordinates from the vehicle tracker into real-world coordinates using our simplified camera model. We present results that demonstrate the ability of our algorithm to produce good estimates of the mean vehicle speed in a lane of traffic.

Decentralized nonlinear model predictive control of multiple flying robots

Abstract: In this paper, we present a nonlinear model predictive control (NMPC) for multiple autonomous helicopters in a complex environment. The NMPC provides a framework to solve optimal discrete control problems for a nonlinear system under state constraints and input saturation. Our approach combines stabilization of vehicle dynamics and decentralized trajectory generation, by including a potential function that reflects the state information of possibly moving obstacles or other vehicles to the cost function. We present various realistic scenarios which show that the integrated approach outperforms a hierarchical structure composed of a separate controller and a path planner based on the potential function method. The proposed approach is combined with an efficient numerical algorithm, which enables the real-time nonlinear model predictive control of multiple autonomous helicopters.

Adaptive, non-singular path-following control of dynamic wheeled robots

Abstract: This paper derives a new type of control law to steer the dynamic model of a wheeled robot of unicycle type along a desired spatial path. The methodology adopted for path following control deals explicitly with vehicle dynamics and plant parameter uncertainty. Furthermore, it overcomes stringent initial condition constraints that are present in a number of path following control strategies described in the literature. This is done by controlling explicitly the rate of progression of a "virtual target" to be tracked along the path, thus bypassing the problems that arise when the position of the virtual target is simply defined by the projection of the actual vehicle on that path. The nonlinear adaptive control law proposed yields convergence of the (closed loop system) path following error trajectories to zero. Controller design relies on Lyapunov theory and backstepping techniques. Simulation results illustrate the performance of the control system proposed.

Nonlinear path following with applications to the control of autonomous underwater vehicles

Abstract: This paper derives a control law to steer the dynamic model of an autonomous underwater vehicle (AUV) along a desired path. The methodology adopted for path following deals explicitly with vehicle dynamics. Furthermore, it overcomes stringent initial condition constraints that are present in a number of path following control strategies described in the literature. Controller design builds on Lyapunov theory and backstepping techniques. The resulting nonlinear feedback control law yields convergence of the path following error trajectories to zero. Simulation results illustrate the performance of the control system proposed.

Cooperative control of multi-vehicle systems using cost graphs and optimization

Abstract: We introduce a class of triangulated graphs for algebraic representation of formations that allows one to specify a mission cost for a group of vehicles. This representation plus the navigational information allows one to formally specify and solve tracking problems for groups of vehicles in formations using an optimization-based approach. The approach is illustrated using a collection of six underactuated vehicles that track a desired trajectory in formation.

A novel driver assist stability system for all-wheel-drive electric vehicles

Abstract: A novel driver-assist stability system for all-wheel-drive electric vehicles is introduced. The system helps drivers maintain control in the event of a driving emergency, including heavy braking or obstacle avoidance. The system comprises a fuzzy logic system that independently controls wheel torque to prevent vehicle spin. Another fuzzy wheel slip controller is used to enhance vehicle stability and safety. A neural network is trained to generate the required reference for yaw rate. Vehicle true speed is estimated by a sensor data fusion method. The intrinsic robustness of fuzzy controllers allows the system to operate in different road conditions successfully. Moreover, the ease of implementing fuzzy controllers gives a potential for vehicle stability enhancement.

Active roll control of single unit heavy road vehicles.

Abstract: Summary Strategies are investigated for controlling active anti-roll systems in single unit heavy road vehicles, so as to maximise roll stability. The achievable roll stability improvements that can be obtained by applying active anti-roll torques to truck suspensions are discussed. Active roll control strategies are developed, based on linear quadratic controllers. It is shown that an effective controller can be designed using the LQG approach, combined with the loop transfer recovery method to ensure adequate stability margins. A roll controller is designed for a torsionally flexible single unit vehicle, and the vehicle response to steady-state and transient cornering manoeuvres is simulated. It is concluded that roll stability can be improved by between 26% and 46% depending on the manoeuvre. Handling stability is also improved significantly.

Fundamentals of Rail Vehicle Dynamics

Abstract: Fundamentals of Rail Vehicle Dynamics lays a foundation for the design of rail vehicles based on the mechanics of wheel-rail interaction as described by the equations of motion. The author advances simple models to elucidate particular challenges and demonstrate innovative systems while using analytical studies to examine novel design concepts. Rather than focusing on a "typical" set of parameters, the book discusses the issues associated with the complete range of parameters available, concentrating on the configuration and parametric design of the bogie in relation to steering, dynamic response, and stability. This is an excellent reference for designers and researchers involved vehicle development.

Modification of vehicle handling characteristics via steer-by-wire

Abstract: This paper presents a physically intuitive method for altering a vehicle handling characteristics through active steering intervention. A full state feedback controller augments the driver steering command via steer-by-wire to achieve desired handling behavior. Accurate estimates of vehicle states are available from a combination of the Global Positioning System (GPS) and inertial navigation system (INS) sensor measurements. By canceling the effects of steering system dynamics and tyre disturbance forces, the steer-by-wire system is able to track commanded steer angle with minimal error. Experimental results verify that with precise steering control and accurate state information, a vehicle handling characteristics can be modified to match driver preference or to compensate for changes in operating conditions.

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An investigation into differential braking strategies for vehicle stability control

Abstract: This paper presents a differential braking strategy for vehicle stability control. The controller has been designed using a three-degree-of-freedom (3DOF) yaw plane vehicle model, and a simulation study has been performed using a full non-linear three-dimensional vehicle model. The brake control inputs have been directly derived from the sliding control law based on a 3DOF yaw plane vehicle model with differential braking. The performance of the sliding controller has been compared with that of the direct yaw moment controller (DYC). Simulation results have shown that the proposed controller can provide a vehicle with superior performance with respect to brake actuation and system smoothness and can minimize the acceleration and jerk without compromising stability at high speed and large steering angle input.

User-appropriate tyre-modelling for vehicle dynamics in standard and limit situations

Abstract: Summary When modelling vehicles for the vehicle dynamic simulation, special attention must be paid to the modelling of tyre-forces and -torques, according to their dominant influence on the results. This task is not only about sufficiently exact representation of the effective forces but also about user-friendly and practical relevant applicability, especially when the experimental tyre-input-data is incomplete or missing. This text firstly describes the basics of the vehicle dynamic tyre model, conceived to be a physically based, semi-empirical model for application in connection with multi-body-systems (MBS). On the basis of tyres for a passenger car and a heavy truck the simulated steady state tyre characteristics are shown together and compared with the underlying experimental values. In the following text the possibility to link the tyre model TMeasy to any MBS-program is described, as far as it supports the ‘Standard Tyre Interface’ (STI). As an example, the simulated and experimental data of a heav...

Coordination of steering and individual wheel braking actuated vehicle yaw stability control

Abstract: Active safety of road transport requires, among other things, the improvement of road vehicle yaw stability by active control. One approach for yaw dynamics improvement is to use differential braking, thereby creating the moment that is necessary to counteract the undesired yaw motion. An alternative approach is to command additional steering angles to create the counteracting moment. The maximum benefit, of course, can be gained through coordinated and combined use of both methods of corrective yaw motion generation in a control strategy. This problem has been approached by using a revised model regulator here as the main controller that utilizes coordinated steering and individual wheel braking actuation, with the aim of achieving better vehicle yaw stability control. Independent use of the individual means of actuation are treated first. Possible strategies for combined and coordinated use of steering and individual wheel braking action in a vehicle yaw dynamics controller are then presented. Simulation results on a nonlinear two track vehicle model are used to illustrate the effectiveness of the coordinated approach.

System dynamics and long-term behaviour of railway vehicles, track and subgrade

Abstract: The DFG Priority Programme 'System Dynamics and Long-Term Behaviour of Vehicle, Track and Subgrade'.- Invited Lectures.- Vehicle/Track Interaction Optimisation within Spoornet.- Active Suspension Technology and its Effect upon Vehicle-Track Interaction.- Rolling-Contact-Fatigue and Wear of Rails: Economic and Technical Aspects.- Vehicle Dynamics.- System Dynamics of Railcars with Radial- and Lateralelastic Wheels.- Distributed Numerical Calculations of Wear in the Wheel-Rail Contact.- Modeling and Simulation of the Mid-Frequency Behaviour of an Elastic Bogie.- Wavy Wear Pattern on the Tread of Railway Wheels.- Rotor Dynamics and Irregular Wear of Elastic Wheelsets.- Contact, Friction, Wear.- On the Numerical Analysis of the Wheel-Rail System in Rolling Contact.- Experimental Analysis of the Cyclic Deformation and Damage Behavior of Characteristic Wheel and Rail Steels.- Friction and Wear of Tractive Rolling Contacts.- Model-Based Validation within the Rail-Wheel-Subgrade Modeling.- Track Dynamics.- Monitoring the Dynamics of Railway Tracks by Means of the Karhunen-Loeve-Transformation.- Combined Modelling of Discretely Supported Track Models and Subgrade Models - Vertical and Lateral Dynamics.- Measurement and Modelling of Resilient Rubber Rail-Pads.- Model-Based Investigation of the Dynamic Behaviour of Railway Ballast.- The Dynamics of Railway Track and Subgrade with Respect to Deteriorated Sleeper Support.- Subgrade Dynamics.- Numerical Model and Laboratory Tests on Settlement of Ballast Track.- Track Settlement Due to Cyclic Loading with Low Minimum Pressure and Vibrations.- Simulation of the Dynamic Behavior of Bedding-Foundation-Soil in the Time Domain.- Dynamic Behavior of Railway Track Systems Analyzed in Frequency Domain.- Experimental and Numerical Investigations on the Track Stability.- Experimental Investigation and Numerical Modelling of Soils and Ballast under Cyclic and Dynamic Loading.- 3D-Simulation of Dynamic Interaction Between Track and Layered Subground.- Rigid Body Dynamics of Railway Ballast.- A Comparative Study of Results from Numerical Track-Subsoil Calculations.

Emergency path planning for autonomous vehicles using elastic band theory

Abstract: In this paper a path planning method for emergency maneuvers of autonomous vehicles is presented. The path planning method is based on the theory of elastic bands. Due to the local disturbances caused by obstacles on the nominal trajectory the elastic behavior allows sufficient flexibility of the emergency trajectory and minimal local changes of curvature. The minimization of local changes of curvature ensures the drivability of the emergency trajectory under vehicle dynamics aspect, which is also considered in this paper. The results of the described method is demonstrated for emergency situations in lane change maneuvers for autonomous vehicles.

Modeling and simulation of autonomous underwater vehicles: design and implementation

Abstract: Autonomous underwater vehicles (AUVs) have many scientific, military, and commercial applications because of their potential capabilities and significant cost-performance improvements over traditional means for performing search and survey. The development of a reliable sampling platform requires a thorough system design and many costly at-sea trials during which systems specifications can be validated. Modeling and simulation provides a cost-effective measure to carry out preliminary component, system (hardware and software), and mission testing and verification, thereby reducing the number of potential failures in at-sea trials. An accurate simulation can help engineers to find hidden errors in the AUV embedded software and gain insights into the AUV operations and dynamics. This paper reviews our research work on real-time physics-based modeling and simulation for our AUVs. The modeling component includes vehicle dynamics, environment and sensor characteristics. The simulation component consists of stand-alone versus hardware-in-the-loop (HIL) implementation, for both single as well as multiple vehicles. In particular, implementation issues with regard to multitasking system resources will be addressed. The main contribution of this paper is to present the rationale for our simulation architecture and the lessons learned.

Road traffic simulation apparatus

Abstract: In a road traffic simulation apparatus that expresses a plurality of mobile units and road traffic environments on a computer to simulate traffic situations in association with a plurality of mobile units, each of the mobile units is expressed by a combination of a driver model, a model of driving operations of a virtual driver, and a vehicle dynamics model, a model of physical behaviors of a mobile unit. The mobile units are programmed to travel independently to each other in a road traffic environment that is expressed on the computer.

Optimization of Vehicle Suspension Systems for Improved Comfort of Road Vehicles Using Flexible Multibody Dynamics

Abstract: Methods that account for the flexibility of multibody systems extend the range of applications to areas such as flexible robots, precision machinery, vehicle dynamics or space satellites. The method proposed here for flexible multibody models allows for the representation of complex-shaped bodies using general finite-element discretizations which deform during the dynamic loading of the system, while the gross rigid body motion of these bodies is still captured using fixed-body coordinate frames. Components of the system for which the deformations are relatively unimportant are represented with rigid bodies. This method is applied to a road vehicle where flexibility plays an important role in its ride and handling dynamic behavior. Therefore, for the study of the limit behavior of the vehicles, the use of flexible multibody models is of high importance. The design process of these vehicles, very often based on intuition and experience, can be greatly enhanced through the use of generalized optimization techniques concurrently with multibody codes. The use of sparse matrix system solvers and modal superposition, to reduce the number of flexible coordinates, in a computer simulation, assures a fast and reliable analysis tool for the optimization process. The optimum design of the vehicle is achieved through the use of an optimization algorithm with finite-differencesensitivities, where the characteristics of the vehicle components are the design variables on which appropriate constraints are imposed. The ride optimization is achieved by finding the optimum of a ride index that results from a metric that accounts for the acceleration in several key points in the vehicle properly weighted in face of their importance for the comfort of the occupant. Simulations with different road profiles are performed for different speeds to account for diverse ride situations. The results are presented and discussed in view of the different methods usedwith emphasis on models and algorithms.

Nonlinear dynamics of vehicle traction

Abstract: SUMMARY The purpose of this study is to understand the nonlinear dynamics of longitudinal ground vehicle traction. Specically , single-wheel models of rubber-tired automobiles under straight-ahead braking and acceleration conditions are investigated in detail. Customarily, the forward vehicle speed and the rotational rate of the tire/wheel are taken as dynamic states. This paper motivates an alternative formulation in which wheel slip, a dimensionless measure of the difference between the vehicle speed and the circumferential speed of the tire relative to the wheel center, replaces the angular velocity of the tire/wheel as a dynamic state. This formulation offers new insight into the dynamic behavior of vehicle traction. The unique features of the modeling approach allow one to capture the full range of dynamic responses of the single-wheel traction models in a relatively simple geometric manner. The models developed here may also be useful for developing and implementing anti-lock brake and traction control control schemes.

Robust motion planning using a maneuver automation with built-in uncertainties

Abstract: In this paper, we extend a recently introduced motion planning framework for autonomous vehicles based on a maneuver automation representation of the vehicle dynamics We bring robustness into the guidance system by accounting for the uncertainties in the motion primitives used by the maneuver automation The uncertainties are taken into account in the offline computation of a guidance function, as well as in a real-time planning policy We illustrate our approach using a high-fidelity simulation model of MIT's autonomous X-Cell miniature helicopter, and present an example that highlights the performance improvement over the original framework We demonstrate that, when uncertainties are present, a nominal planning policy generates suboptimal trajectories in both open- and closed-loop guidance, and that trajectories obtained by applying the robust policy are less sensitive to perturbations in the motion primitives

Toward More Realistic Driving Behavior Models for Autonomous Vehicles in Driving Simulators

Abstract: Autonomous vehicles are perhaps the most encountered element in a driving simulator. Their effect on the realism of the simulator is critical. For autonomous vehicles to contribute positively to the realism of the hosting driving simulator, they need to have a realistic appearance and, possibly more importantly, realistic behavior. Addressed is the problem of modeling realistic and humanlike behaviors on simulated highway systems by developing an abstract framework that captures the details of human driving at the microscopic level. This framework consists of four units that together define and specify the elements needed for a concrete humanlike driving model to be implemented within a driving simulator. These units are the perception unit, the emotions unit, the decision-making unit, and the decision-implementation unit. Realistic models of humanlike driving behavior can be built by implementing the specifications set by the driving framework. Four humanlike driving models have been implemented on the basis of the driving framework: (a) a generic normal driving model, (b) an aggressive driving model, (c) an alcoholic driving model, and (d) an elderly driving model. These driving models provide experiment designers with a powerful tool for generating complex traffic scenarios in their experiments. These behavioral models were incorporated along with three-dimensional visual models and vehicle dynamics models into one entity, which is the autonomous vehicle. Subjects perceived the autonomous vehicles with the described behavioral models as having a positive effect on the realism of the driving simulator. The erratic driving models were identified correctly by the subjects in most cases.

An H-infinity-based control design methodology dedicated to the active control of vehicle longitudinal oscillations

Abstract: This paper deals with the problem of active damping of vehicle oscillations. A complete methodology based on an H/spl infin/ optimization is presented. Several dedicated analysis tools are used in order to analyze the behavior of the closed-loop system. Two tuning parameters allow the design of a controller managing the compromise between performance (in terms of oscillation attenuation and limit cycles) and robustness. Finally, a feedforward component is designed in order to improve the performance without changing the robustness properties or the controller complexity. Simulation results obtained with an experimentally validated model show the efficiency of the resulting controller.

Estimation of Passenger Vehicle Inertial Properties and Their Effect on Stability and Handling

Abstract: Vehicle handling and stability are significantly affected by inertia properties including moment of inertia and center of gravity location. This paper presents an analysis of the National Highway Traffic Safety Administration (NHTSA) Inertia Database and gives regression equations that approximate moments of inertia and center of gravity height given basic vehicle properties including weight, width, length and height. The handling and stability consequences of the relationships of inertial properties with vehicle size will be analyzed in terms of other vehicle dynamics models and the use of a nonlinear maneuvering simulation.

Modelling and analysis of electric power steering system and its effect on vehicle dynamic behaviour

Abstract: While most passenger vehicles equipped with power steering systems are hydraulic power assisted, Electric Power Steering (EPS) systems are becoming wide spread since they can afford higher fuel efficiency. This paper develops an integrated simulation of an EPS control system with a full vehicle model. Using co-simulation technique, a full vehicle model interacting with EPS control algorithm is concurrently simulated on a single bump road condition. The effects of EPS on the vehicle dynamic behaviour and handling responses resulting from steer and road input are analysed and compared with proving ground experimental data. The comparisons show reasonable agreement on tie-rod load, rack displacement, steering wheel torque and tyre centre acceleration. This developed co-simulation capability may be useful for EPS performance evaluation and calibration as well as for vehicle handling performance integration.

A low-cost driving simulator for full vehicle dynamics simulation

Abstract: This paper describes the construction of a low-cost PC-based driving simulator that can perform five degree-of-freedom (DOF) motions similar to a road vehicle. The mathematical equations of vehicle dynamics are first derived from the 2-DOF bicycle model and incorporated with the tire, steering, and suspension subsystems. The equations of motion are then programmed by MATLAB, transferred into C++ code in the MIDEVA environment, and further developed into a motion platform control program by C++Builder. To achieve the simulator functions, a motion platform that is constructed by five hydraulic cylinders is designed, and its kinetics/inverse kinetics analysis is also conducted. Driver operation signals such as steering wheel angle, accelerator pedal, and brake pedal positions are measured to trigger the vehicle dynamics calculation and further actuate the cylinders by the motion platform control program. In addition, a digital PID controller is added to achieve the stable and accurate displacements of the motion platform. The experiments prove that the designed simulator is adequate in performing some special road driving situations discussed in this paper.

Parameter estimation of railway vehicle dynamic model using rao-blackwellised particle filter

Abstract: This paper presents the development of a new method for parameter estimation in linear state space model. The proposed method is based on a Rao-Blackwellised particle filter. The simulation results with a railway vehicle dynamic model are provided which demonstrate the effectiveness of the proposed method in comparison with the conventional EKF-based method.