scispace - formally typeset
Search or ask a question

Showing papers on "Vehicle dynamics published in 2007"


Journal ArticleDOI
TL;DR: The effectiveness of the proposed MPC formulation is demonstrated by simulation and experimental tests up to 21 m/s on icy roads, and two approaches with different computational complexities are presented.
Abstract: In this paper, a model predictive control (MPC) approach for controlling an active front steering system in an autonomous vehicle is presented. At each time step, a trajectory is assumed to be known over a finite horizon, and an MPC controller computes the front steering angle in order to follow the trajectory on slippery roads at the highest possible entry speed. We present two approaches with different computational complexities. In the first approach, we formulate the MPC problem by using a nonlinear vehicle model. The second approach is based on successive online linearization of the vehicle model. Discussions on computational complexity and performance of the two schemes are presented. The effectiveness of the proposed MPC formulation is demonstrated by simulation and experimental tests up to 21 m/s on icy roads

1,184 citations


Journal ArticleDOI
30 Apr 2007
TL;DR: Different modeling methods such as physics-based Resistive Companion Form technique and Bond Graph method are presented with powertrain component and system modeling examples to discuss the need for modeling and simulation of electric and hybrid vehicles.
Abstract: This paper discusses the need for modeling and simulation of electric and hybrid vehicles. Different modeling methods such as physics-based Resistive Companion Form technique and Bond Graph method are presented with powertrain component and system modeling examples. The modeling and simulation capabilities of existing tools such as Powertrain System Analysis Toolkit (PSAT), ADvanced VehIcle SimulatOR (ADVISOR), PSIM, and Virtual Test Bed are demonstrated through application examples. Since power electronics is indispensable in hybrid vehicles, the issue of numerical oscillations in dynamic simulations involving power electronics is briefly addressed

432 citations


Journal ArticleDOI
TL;DR: In this paper, the adaptive nature of the guidance method makes its stability independent of vehicle velocity, and the stability analysis is also extended to show robust stability in the presence of saturated lateral acceleration, which is an inherent limitation of flight vehicles.
Abstract: Performance and stability are demonstrated for a nonlinear path-following guidance method for unmanned air vehicles. The method was adapted from a pure pursuit-based path following, which has been widely used in ground based robot applications. The method is known to approximate a proportional-derivative controller when following a straight line path, but it is shown that there is also an element of anticipatory control that enables tight tracking when following curved paths. Ground speed is incorporated into the computation of commanded lateral acceleration, which adds an adaptive capability to accommodate vehicle speed changes due to external disturbances such as wind. Asymptotic Lyapunov stability of the nonlinear guidance method is demonstrated when the unmanned air vehicle is following circular paths. The adaptive nature of the guidance method makes its stability independent of vehicle velocity. The stability analysis is also extended to show robust stability of the guidance law in the presence of saturated lateral acceleration, which is an inherent limitation of flight vehicles. Flight tests of the algorithm, using two small unmanned air vehicles, showed that each aircraft was controlled to within 1.6 m root mean square when following circular paths. The method was used to perform a rendezvous of the two aircraft, bringing them into very close proximity, within 12 m of along track separation and 1.4 m root mean square relative position errors.

389 citations


Journal ArticleDOI
TL;DR: An algorithm is presented for wheeled mobile robot trajectory generation that achieves a high degree of generality and efficiency and is efficient enough to use in real time due to its use of nonlinear programming techniques that involve searching the space of parameterized vehicle controls.
Abstract: An algorithm is presented for wheeled mobile robot trajectory generation that achieves a high degree of generality and efficiency. The generality derives from numerical linearization and inversion of forward models of propulsion, suspension, and motion for any type of vehicle. Efficiency is achieved by using fast numerical optimization techniques and effective initial guesses for the vehicle controls parameters. This approach can accommodate such effects as rough terrain, vehicle dynamics, models of wheel-terrain interaction, and other effects of interest. It can accommodate boundary and internal constraints while optimizing an objective function that might, for example, involve such criteria as obstacle avoidance, cost, risk, time, or energy consumption in any combination. The algorithm is efficient enough to use in real time due to its use of nonlinear programming techniques that involve searching the space of parameterized vehicle controls. Applications of the presented methods are demonstrated for planetary rovers.

375 citations


Journal ArticleDOI
TL;DR: In this article, a dual-mode control strategy for UAVs flying in a formation in a free and an obstacle-laden environment is proposed, where a safe mode is defined as an operation in an obstacle free environment and a dangerous mode is activated when there is a chance of collision or when there are obstacles in the path.
Abstract: Navigation problems of unmanned air vehicles (UAVs) flying in a formation in a free and an obstacle-laden environment are investigated in this brief. When static obstacles popup during the flight, the UAVs are required to steer around them and also avoid collisions between each other. In order to achieve these goals, a new dual-mode control strategy is proposed: a "safe mode" is defined as an operation in an obstacle-free environment and a "danger mode" is activated when there is a chance of collision or when there are obstacles in the path. Safe mode achieves global optimization because the dynamics of all the UAVs participating in the formation are taken into account in the controller formulation. In the danger mode, a novel algorithm using a modified Grossberg neural network (GNN) is proposed for obstacle/collision avoidance. This decentralized algorithm in 2-D uses the geometry of the flight space to generate optimal/suboptimal trajectories. Extension of the proposed scheme for obstacle avoidance in a 3-D environment is shown. In order to handle practical vehicle constraints, a model predictive control-based tracking controller is used to track the references generated. Numerical results are provided to motivate this approach and to demonstrate its potential.

335 citations


Journal ArticleDOI
TL;DR: In this article, a system-oriented framework for developing computer-vision technology for safer automobiles is presented, which considers three main components of the system: environment, vehicle, and driver.
Abstract: This paper presents investigations into the role of computer-vision technology in developing safer automobiles. We consider vision systems, which cannot only look out of the vehicle to detect and track roads and avoid hitting obstacles or pedestrians but simultaneously look inside the vehicle to monitor the attentiveness of the driver and even predict her intentions. In this paper, a systems-oriented framework for developing computer-vision technology for safer automobiles is presented. We will consider three main components of the system: environment, vehicle, and driver. We will discuss various issues and ideas for developing models for these main components as well as activities associated with the complex task of safe driving. This paper includes a discussion of novel sensory systems and algorithms for capturing not only the dynamic surround information of the vehicle but also the state, intent, and activity patterns of drivers

320 citations


Journal ArticleDOI
TL;DR: In this paper, a nonlinear feedback control law is developed to steer an AUV along a desired path, which overcomes initial condition constraints that are present in a number of path-following control strategies described in the literature.

314 citations


Proceedings ArticleDOI
13 Jun 2007
TL;DR: In this article, the authors presented a model of a four rotor vertical take-off and landing (VTOL) unmanned air vehicle known as quadrotor aircraft and explained its control architecture including vision-based control.
Abstract: In this paper, we present a model of a four rotor vertical take-off and landing (VTOL) unmanned air vehicle known as quadrotor aircraft. And we explained its control architecture including vision based control. Quadrotors have generated considerable interest in both the control community due to their complex dynamics and military because of their advantages over regular air vehicles. The proposed dynamical model which comprises gyroscopic effects and its control strategies can be source for future works.

285 citations


Book
23 Jul 2007
TL;DR: In this article, the authors present a computational multibody-system approach that can be used to develop complex models of railroad vehicle systems, including derailment and accident scenarios, design issues, and performance evaluation.
Abstract: The methods of computational mechanics have been used extensively in modeling many physical systems. The use of multibody-system techniques, in particular, has been applied successfully in the study of various, fundamentally different applications. Railroad Vehicle Dynamics: A Computational Approach presents a computational multibody-system approach that can be used to develop complex models of railroad vehicle systems. The book examines several computational multibody-system formulations and discusses their computer implementation. The computational algorithms based on these general formulations can be used to develop general- and special-purpose railroad vehicle computer programs for use in the analysis of railroad vehicle systems, including the study of derailment and accident scenarios, design issues, and performance evaluation. The authors focus on the development of fully nonlinear formulations, supported by an explanation of the limitations of the linearized formulations that are frequently used in the analysis of railroad vehicle systems. The chapters of the book are organized to guide readers from basic concepts and definitions through a final understanding of the utility of fully nonlinear multibody- system formulations in the analysis of railroad vehicle systems. Railroad Vehicle Dynamics: A Computational Approach is a valuable reference for researchers and practicing engineers who commonly use general-purpose, multibody-system computer programs in the analysis, design, and performance evaluation of railroad vehicle systems.

285 citations


Journal ArticleDOI
01 May 2007
TL;DR: In this paper, the authors present a methodology for online tracking and diagnosis of hybrid systems that combine digital (discrete) supervisory controllers with analog (continuous) plants, and demonstrate the effectiveness of the approach with experiments conducted on the fuel transfer system of fighter aircraft.
Abstract: Techniques for diagnosing faults in hybrid systems that combine digital (discrete) supervisory controllers with analog (continuous) plants need to be different from those used for discrete or continuous systems. This paper presents a methodology for online tracking and diagnosis of hybrid systems. We demonstrate the effectiveness of the approach with experiments conducted on the fuel-transfer system of fighter aircraft

245 citations


Journal ArticleDOI
TL;DR: In this article, the authors present a survey of the application of these technologies to suspensions and running gear, focused upon the complementary issues of control and monitoring, from which they identify the key trends and conclude with a forward look at what is likely to develop over the next few years.
Abstract: Over the last twenty to thirty years, railway vehicle dynamics has changed from being an essentially mechanical engineering discipline to one that is increasingly starting to include sensors, electronics and computer processing. This paper surveys the application of these technologies to suspensions and running gear, focused upon the complementary issues of control (which has been reviewed within Vehicle System Dynamics previously) and monitoring (which has not previously been reviewed). The theory, concepts and implementation status are assessed in each case, from which the paper identifies the key trends and concludes with a forward look at what is likely to develop over the next years.

Journal ArticleDOI
TL;DR: This paper addresses the combined problem of trajectory planning and tracking control for underactuated autonomous underwater vehicles (AUVs) on the horizontal plane by using vehicle dynamics to compute the reference orientation and body-fixed velocities.

Proceedings ArticleDOI
01 Dec 2007
TL;DR: A predictive control problem in order to best follow a given path by controlling the front steering angle, brakes and traction at the four wheels independently, while fulfilling various physical and design constraints, is formulated.
Abstract: A Model Predictive Control (MPC) approach for controlling active front steering, active braking and active differentials in an autonomous vehicle is presented. We formulate a predictive control problem in order to best follow a given path by controlling the front steering angle, brakes and traction at the four wheels independently, while fulfilling various physical and design constraints. At each time step a trajectory is assumed to be known over a finite horizon, and an MPC controller computes the system inputs in order to best follow the desired trajectory on slippery roads at a given entry speed. We start from the results presented in [1], [2] and formulate the MPC problem based on successive on-line linearization of the nonlinear vehicle model (LTV MPC). Simulative results are presented, interpreted and compared against LTV MPC schemes which make use only of steering and/or braking.

Journal ArticleDOI
TL;DR: The proposed approach is a hierarchical-structured algorithm that fuses traffic environment data with car dynamics in order to accurately predict the trajectory of the ego-vehicle, allowing the active safety system to inform, warn the driver, or intervene when critical situations occur.
Abstract: Path prediction is the only way that an active safety system can predict a driver's intention. In this paper, a model-based description of the traffic environment is presented - both vehicles and infrastructure - in order to provide, in real time, sufficient information for an accurate prediction of the ego-vehicle's path. The proposed approach is a hierarchical-structured algorithm that fuses traffic environment data with car dynamics in order to accurately predict the trajectory of the ego-vehicle, allowing the active safety system to inform, warn the driver, or intervene when critical situations occur. The algorithms are tested with real data, under normal conditions, for collision warning (CW) and vision-enhancement applications. The results clearly show that this approach allows a dynamic situation and threat assessment and can enhance the capabilities of adaptive cruise control and CW functions by reducing the false alarm rate.

Journal ArticleDOI
TL;DR: An algorithm that drives a unicycle type robot to a desired path, including obstacle avoidance capabilities, which relies on Lyapunov theory, backstepping techniques and deals explicitly with vehicle dynamics and overcomes the initial condition constraints present in a number of path-following control strategies described in the literature.
Abstract: This paper proposes an algorithm that drives a unicycle type robot to a desired path, including obstacle avoidance capabilities. The path-following control design relies on Lyapunov theory, backstepping techniques and deals explicitly with vehicle dynamics. Furthermore, it overcomes the initial condition constraints 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 path target point is simply defined as the closest point on the path. The obstacle avoidance part uses the Deformable Virtual Zone (DVZ) principle. This principle defines a safety zone around the vehicle in which the presence of an obstacle induces an “intrusion of information” that drives the vehicle reaction. The overall algorithm is combined with a guidance solution that embeds the path-following requirements in a desired intrusion information function, which steers the vehicle to the desired path while the DVZ ensures minimal contact with the obstacle, implicitly bypassing it. Simulation and experimental results illustrate the performance of the control system proposed.

Journal ArticleDOI
TL;DR: This paper provides a complete analysis of the formation stability for this class of decentralized control problems and relates the complete closed-loop system poles to the transmitter and receiver gains, and the spectral properties of the Laplacian of the graph describing the communication links within the formation.
Abstract: The control of cooperative formations of vehicles can be based on parallel estimation, where each vehicle determines its control action from a locally maintained estimate of the entire observable formation state. Vehicles may communicate with one another allowing the local estimates to incorporate information from other estimators in the formation. This paper studies the dynamics that arise in this situation and provides a complete analysis of the formation stability for this class of decentralized control problems. In the absence of communication, the local estimator-controllers' open-loop dynamics necessarily appear in the closed-loop system dynamics, giving a more stringent closed-loop stability condition than in the single controller case. The estimators achieve consensus if and only if the controllers' open-loop dynamics are stable. Communication amongst the estimators can be used to specify the complete system dynamics and we present a framework for the analysis and design of communicated information links in the formation. We relate the complete closed-loop system poles to the transmitter and receiver gains, and the spectral properties of the Laplacian of the graph describing the communication links within the formation. These results also apply to parallel estimation problems in other applications including power system control and redundant channel control architectures.

Dissertation
01 Jan 2007
TL;DR: In this article, a method to derive the tire forces for simultaneous braking, cornering and camber, by combining empirical models for the pure behavior of each of respective action is presented.
Abstract: New system technologies are continuously improving the performance of vehicles regarding comfort, stability, environmental stresses, and safety. Novel sensors are developed and used together with advanced control algorithms and faster and more accurate actuators to help the driver to maneuver the vehicle in a safer way. The physical traction limit set by the friction between the tires and the road can, however, not be overridden. The behavior of tires is, therefore, an important issue since it determines the possibilities to control the vehicle. One essential task for the vehicle control system is to be able to fully utilize these limits. Another is to assist the driver to choose an adequate driving style, adapted to the actual conditions. A method to derive the tire forces for simultaneous braking, cornering and camber, by combining empirical models for the pure behavior of each of respective action is presented in the thesis. The method is based on the physical foundation brought by the simple, but well-suited brush model theory. The pure-slip tire models can be given as empirical models or as raw tabular data. The implementation is verified to be well-working and computationally sound and good results are obtained in validation with the available empirical data. A new type of on board brush-model based friction-estimator using the local measurements on the vehicle is also proposed. A major invention is the way of collecting the measurements into bins, such that the available data used for optimization is evenly weighted along the force and slip axis. Experimental data has been collected and evaluated to ensure the validity of the brush model during certain conditions. The estimator has been implemented and validated on a personal car. The wheel speed signal is an essential signal in many system applications. Based on problems observed during performed measurements, a few ways to reduce the noise on the signal, without adding any phase shift or time delay, are discussed in the thesis. (Less)

Journal ArticleDOI
TL;DR: In this paper, a 14 DOF vehicle model that includes dynamics of roll center and nonlinear effects due to vehicle geometry changes is developed, and the limitations, validity of simplified equations, and various modeling assumptions are discussed by analyzing their effect on the model roll responses in various vehicle maneuvers.
Abstract: An accurate and realistic vehicle model is essential for the development of effective vehicle control systems. Many different vehicle models have been developed for use in various vehicle control systems. The complexity of these models and the assumptions made in their development depend on their application. This article looks into the development and validity of vehicle models for prediction of roll behavior and their suitability for application in roll control systems. A 14 DOF vehicle model that includes dynamics of roll center and nonlinear effects due to vehicle geometry changes is developed. The limitations, validity of simplified equations, and various modeling assumptions are discussed by analyzing their effect on the model roll responses in various vehicle maneuvers. A formulation of the popular 8 DOF vehicle model that gives good correlation with the 14 DOF model is presented. The possible limitations of the 14 DOF model compared with an actual vehicle are also discussed.

Journal ArticleDOI
TL;DR: In this article, a robust non-parametric approach to improve vehicle yaw rate dynamics by means of a rear active differential is introduced, where an additive model set is used to describe the uncertainty arising from the wide range of the vehicle operating situations.

Proceedings ArticleDOI
10 Apr 2007
TL;DR: A new planning heuristic for 3D motions of fixed-wing UAVs based on 2D Dubins curves, along with precomputed sets of motion primitives derived from the vehicle dynamics model are introduced in order to achieve high efficiency.
Abstract: We present an efficient two-phase approach to motion planning for small fixed-wing unmanned aerial vehicles (UAVs) navigating in complex 3D air slalom environments. A coarse global motion planner first computes a kinematically feasible obstacle-free path in a discretized 3D workspace which roughly satisfies the kinematic constraints of the UAV. Given a coarse global path, a fine local motion planner is used to compute a more accurate trajectory for the UAV at a higher level of detail. The local planner is iterated as the vehicle traverses and refines the global path as needed up to its planning horizon. We also introduce a new planning heuristic for 3D motions of fixed-wing UAVs based on 2D Dubins curves, along with precomputed sets of motion primitives derived from the vehicle dynamics model in order to achieve high efficiency.

Journal ArticleDOI
TL;DR: A sensitivity-based methodology is presented to choose the best possible gains parameterization in a state Riccati dependent equation (SDRE) feedback controller and results will be validated and compared with other nonlinear optimal feedback controllers, from a realistic industrial simulator environment for vehicle dynamics.
Abstract: This paper presents a feedback steering control strategy for a vehicle in an automatic driving context. Two main contributions in terms of control are highlighted. On the one hand, the automatic reference trajectories generation from geometric path constraints (obstacles). Thanks to the flatness property of the considered model, the longitudinal velocity will be controlled around a quasi-constant value while lateral and yaw dynamics targets will allow to avoid obstacles. On the other hand, a sensitivity-based methodology will be presented to choose the best possible gains parameterization in a state Riccati dependent equation (SDRE) feedback controller. Both direct and adjoint sensitivity methods are used, together with a dynamic inversion of the system, in order to optimize the performances of the controller. Obstacle avoiding simulation results will be validated and compared with other nonlinear optimal feedback controllers, from a realistic industrial simulator environment for vehicle dynamics

Journal ArticleDOI
TL;DR: In this article, a fuzzy-logic procedure was implemented to identify the side-slip angle of a single-track vehicle using the information provided by the kinematic formulation during a transient manoeuvre.
Abstract: Sideslip angle could provide important information concerning vehicle's stability. Unfortunately direct measurement of sideslip angle requires a complex and expensive experimental set-up, which is not suitable for implementation on ordinary passenger cars; thus, this quantity has to be estimated starting from the measurements of vehicle lateral/longitudinal acceleration, speed, yaw rate and steer angle. According to the proposed methodology, sideslip angle is estimated as a weighted mean of the results provided by a kinematic formulation and those obtained through a state observer based on vehicle single-track model. Kinematical formula is considered reliable for a transient manoeuvre, while the state observer is used in nearly quasi-state condition. The basic idea of the work is to make use of the information provided by the kinematic formulation during a transient manoeuvre to update the single-track model parameters (tires cornering stiffnesses). A fuzzy-logic procedure was implemented to identify stea...

Journal ArticleDOI
Stefan Gehrig1, F.J. Stein1
TL;DR: A planning and decision component to generalize vehicle following to situations with nonautomated interfering vehicles in mixed traffic by treating the path of the leader vehicle as an elastic band that is subjected to repelling forces of obstacles in the surroundings.
Abstract: The vehicle-following concept has been widely used in several intelligent-vehicle applications. Adaptive cruise control systems, platooning systems, and systems for stop-and-go traffic employ this concept: The ego vehicle follows a leader vehicle at a certain distance. The vehicle-following concept comes to its limitations when obstacles interfere with the path between the ego vehicle and the leader vehicle. We call such situations dynamic driving situations. This paper introduces a planning and decision component to generalize vehicle following to situations with nonautomated interfering vehicles in mixed traffic. As a demonstrator, we employ a car that is able to navigate autonomously through regular traffic that is longitudinally and laterally guided by actuators controlled by a computer. This paper focuses on and limits itself to lateral control for collision avoidance. Previously, this autonomous-driving capability was purely based on the vehicle-following concept using vision. The path of the leader vehicle was tracked. To extend this capability to dynamic driving situations, a dynamic path-planning component is introduced. Several driving situations are identified that necessitate responses to more than the leader vehicle. We borrow an idea from robotics to solve the problem. Treat the path of the leader vehicle as an elastic band that is subjected to repelling forces of obstacles in the surroundings. This elastic-band framework offers the necessary features to cover dynamic driving situations. Simulation results show the power of this approach. Real-world results obtained with our demonstrator validate the simulation results

Journal ArticleDOI
TL;DR: A review of the dynamics of heavy road-vehicle systems emphasizing directional performance is presented in this paper, where the authors present information on the following topics: why are articulated vehicles used; units, hitches, and combination vehicles; multiple axle suspensions and steering systems; important performance issues; models and simulation tools; and controlling directional performance.
Abstract: This review of the dynamics of heavy road–vehicle systems emphasizes directional performance. The review presents information on the following topics: why are articulated vehicles used; units, hitches, and combination vehicles; multiple axle suspensions and steering systems; important performance issues; models and simulation tools; and controlling directional performance. The concluding section summarizes the material presented and provides ideas regarding the application of vehicle system dynamics concepts in developing controllers for road trains.

Journal ArticleDOI
01 Apr 2007
TL;DR: In this paper, an integrated control system of active front steering and normal force control using fuzzy reasoning to enhance the vehicle-handling performance was presented. But the performance of individual control systems were first developed, and then their performances were compared with that of the integrated system.
Abstract: Integration of vehicle chassis control system has gained increasing attention since it can improve the vehicle safety and performance through effective coordination of individual control systems. This paper presents the development of an integrated control system of active front steering and normal force control using fuzzy reasoning to enhance the vehicle-handling performance. Individual control systems were first developed, and then their performances were compared with that of the integrated system. The simulation results indicate that the integrated chassis control scheme utilizing the steering and suspension controllers has proven to be more effective in attaining the desired performance that would not be attained individually.

Journal ArticleDOI
TL;DR: In this paper, an adaptive tire force model that takes variations in road friction into account is proposed to calculate lateral tire forces, vehicle sideslip angle, and road friction. But the adaptive observer is evaluated in comparison with two nonadaptive observers that use tire force models with fixed parameters.
Abstract: The estimation of vehicle dynamic variables is essential for the enhancement of safety, in particular for braking and trajectory-control systems. This paper proposes a new estimation process to calculate lateral tire forces, vehicle sideslip angle, and road friction. The estimation process (an adaptive observer) is constructed by combining a vehicle model and a tire force model. More specifically, this study proposes an adaptive tire force model that takes variations in road friction into account. The adaptive observer is evaluated in comparison with two nonadaptive observers that use tire force models with fixed parameters. This study also proposes a road friction identification method operating in an online context. The observers and the road friction identification method are first evaluated using vehicle simulator software. Subsequently, observers are compared to real data acquired using an experimental vehicle. This paper also includes a description of the experimental platform. Results show the accuracy and potential of the estimation process.

Journal ArticleDOI
TL;DR: In this article, a new VDC system for a four motorized-wheels electric vehicle has been developed, for which the traction of each wheel can be controlled individually, which can improve the vehicle handling and active safety of driver and passengers considerably.
Abstract: It is shown that the vehicle dynamic control (VDC) system can improve the vehicle handling and active safety of driver and passengers considerably. The control of vehicle yaw moment through differential braking, based on the vehicle dynamic state feedbacks, is a traditional way of VDC. In this study, a new VDC system for a four motorized-wheels electric vehicle has been developed, for which the traction of each wheel can be controlled individually. Using this feature, the new VDC system provides the desired tractive force of vehicle and the desired external yaw moment through the integrated control of wheel motors. The structure of the control system is a multilayer type, which has been developed by using independent controllers, designed in accordance with the appropriate theories.

Journal ArticleDOI
TL;DR: In this paper, a systematic methodology is applied in an effort to select optimum values for the suspension damping and stiffness parameters of two degrees of freedom quarter-car models, subjected to road excitation.
Abstract: A systematic methodology is applied in an effort to select optimum values for the suspension damping and stiffness parameters of two degrees of freedom quarter-car models, subjected to road excitation. First, models involving passive suspension dampers with constant or dual rate characteristics are considered. In addition, models with semi-active suspensions are also examined. Moreover, special emphasis is put in modeling possible temporary separations of the wheel from the ground. For all these models, appropriate methodologies are employed for capturing the motions of the vehicle resulting from passing with a constant horizontal speed over roads involving an isolated or a distributed geometric irregularity. The optimization process is based on three suitable performance criteria, related to ride comfort, suspension travel and road holding of the vehicle and yielding the most important suspension stiffness and damping parameters. As these criteria are conflicting, a suitable multi-objective optimization ...

Journal ArticleDOI
TL;DR: Numerical simulation shows that the 4WS vehicle equipped with the mu-synthesis robust controller has better maneuverability and a stronger ability to resist disturbances; it is not sensitive to the variations in vehicle parameters.
Abstract: A mu-synthesis robust controller of a four-wheel steering (4WS) vehicle is designed with the optimized weighting functions to attenuate the external disturbances while the yaw rate is chosen as the only feedback signal. Numerical simulation shows that the 4WS vehicle equipped with the mu-synthesis robust controller has better maneuverability and a stronger ability to resist disturbances; it is not sensitive to the variations in vehicle parameters. The mu-synthesis controller has an advantage over the Hprop controller; the latter is thought to be relatively conservative for normal ambient disturbances.

Journal ArticleDOI
TL;DR: In this article, a joint-point locus approach is proposed to study the dynamics and stability of a vehicle planar motion system, where the difference between the front and the rear steering angles plays a key role in vehicle system dynamics.
Abstract: In this article, the problems of dynamics and stability for vehicle planar motion systems have been investigated. By introducing a so-called joint-point locus approach, equilibria of the system and their associated stability properties are given geometrically. With this method, it is discovered that the difference between the front and the rear steering angles plays a key role in vehicle system dynamics and that the topological structure of the phase portrait and the types of bifurcations are different from those published previously. In particular, the vehicle system could still be stabilized even when pushed to work in a certain severely nonlinear region, by applying extremely large steering angles. However, it is worth noticing that the attractive domain of the stable equilibrium is very narrow. These developments might prove to be important in active steering control design. Numerical experiments are carried out to illustrate the potentials of the proposed techniques.