Showing papers on "Vehicle dynamics published in 1996"

Adaptive Control

Abstract: This book, written by two major figures in adaptive control, provides a wealth of material for researchers, practitioners, and students. While some researchers in adaptive control may note the absence of a particular topic, the book‘s scope represents a high-gain instrument. It can be used by designers of control systems to enhance their work through the information on many new theoretical developments, and can be used by mathematical control theory specialists to adapt their research to practical needs. The book is strongly recommended to anyone interested in adaptive control.

Estimation of vehicle lateral velocity

Abstract: Two techniques for the estimation of vehicle lateral velocity using state observers are considered. The first method uses a physical model of the vehicle handling. The physical model based observer produces noise free lateral velocity estimates, but can be sensitive to changes in the vehicle parameters. It produces reliable estimates in the vehicle linear handling region only. We show that the observer gain can be selected to make the observer insensitive to certain parameter variations. The second method uses a kinematic model relating longitudinal velocity, lateral velocity, longitudinal acceleration, lateral acceleration and yaw rate. This model contains no vehicle parameters, and hence the kinematic model based observer is unaffected by changes in the vehicle parameters. The observer produces reliable lateral velocity estimates throughout the linear and nonlinear handling regions, the estimates however are more noisy than those produced by the physical model based observer. The techniques are compared using simulated data for manoeuvers in the linear and nonlinear handling regions of the vehicle.

Motion generation and control for parking an autonomous vehicle

Abstract: Practical aspects of motion generation and control for parking a nonholonomic autonomous vehicle are considered. An iterative algorithm for the parallel parking maneuver is proposed. It is based on ultrasonic range data processing. To control the steering angle and longitudinal velocity of the vehicle during the parking maneuver, sinusoidal reference functions are used. To prevent collisions, the maneuver is carried out as a reactive motion. The developed control is experimentally verified for a LIGIER electric autonomous vehicle.

A single-wheel, gyroscopically stabilized robot

Abstract: We are developing a novel concept for mobility, and studying fundamental research issues on dynamics and control of the mobile robot. The robot, called Gyrover, is a single-wheel vehicle with an internal gyroscope that provides mechanical stabilization and steering capability. This configuration conveys significant advantages over multi-wheel, statically stable vehicles, including good dynamic stability and insensitivity to attitude disturbances; high manoeuvrability; low rolling resistance; ability to recover from falls; and amphibious capability. In this paper we present the design, analysis and implementation of the robot, as well as the associated research issues and potential applications.

Adaptive vehicle traction force control for intelligent vehicle highway systems (ivhs)

Abstract: This paper focuses on the application of adaptive vehicle traction force control to the robust longitudinal control of vehicles. Adaptive fuzzy logic control and adaptive sliding mode control are applied to the fastest stable acceleration/deceleration and robust vehicle platooning problems. Results indicate that both controllers show good performance under time-varying operating conditions.

Vehicle dynamics : theory into practice

Abstract: The paper reviews the contributions of vehicle dynamics theory to practical vehicle design. In particular, it focuses on actively controlled components, for example active suspension, four wheel steering, and their impact on vehicle performance and safety.

A simplified dynamics model for autonomous underwater vehicles

Abstract: This paper deals with the derivation and validation of a simplified dynamics model for streamlined underwater vehicles. The model is derived in a form which only requires the specification of the vehicle's geometry, and the lift and drag characteristics of its constituent elements. The vehicle is decomposed into these elements, including hull, individual control surfaces, and propulsion system. The forces and moments acting on the vehicle are determined through a summation of the component effects, with correction factors to account for interference effects. Because the model is not linearized, it retains the vehicle's fundamental nonlinear behaviour. The approach is validated by comparing the model results to those measured on an existing AUV.

Practical point stabilization of a nonholonomic mobile robot using neural networks

Abstract: A control structure that makes possible the integration of a kinematic controller and a neural network (NN) computed-torque controller for nonholonomic mobile robots is presented. This control algorithm is applied to the practical point stabilization problem i.e. stabilization to a small neighborhood of the origin. The NN controller proposed in this work can deal with unmodelled bounded disturbances and/or unstructured unmodelled dynamics in the vehicle. Online NN weight tuning algorithms that do not require off-line learning yet guarantee small tracking errors and bounded control signals are utilized.

Experimental study on a learning control system with bound estimation for underwater robots

Abstract: Underwater robotic vehicles (URVs) have become an important tool for numerous underwater tasks due to their greater speed, endurance, depth capability, and a higher factor of safety than human divers. However, most vehicle control system designs are based on simplified vehicle models and often result in poor vehicle performance due to the nonlinear and time-varying vehicle dynamics having parameter uncertainties. Conventional proportional-integral-derivative (PID) type controllers cannot provide good performance without fine-tuning the controller gains and may fail for sudden changes in the vehicle dynamics and its environment. Conventional adaptive control systems based on parameter adaptation techniques also fail in the presence of unmodeled dynamics. This paper describes a new vehicle control system using the bound estimation techniques, capable of learning, and adapting to changes in the vehicle dynamics and parameters. The control system was extensively “wet-tested” on the Omni-Directional Intelligent Navigator (ODIN)-a six degree-of-freedom, experimental underwater vehicle developed at the Autonomous Systems Laboratory, and its performance was compared with the performance of a conventional linear control system. The results showed the controller's ability to provide good performance in the presence of unpredictable changes in the vehicle dynamics and its environment, and it's capabilities of learning and adapting.

Modelling and control of the longitudinal and lateral dynamics of a series hybrid vehicle

Abstract: This paper presents models and control structures for series hybrid drive trains. For the longitudinal dynamics of the series hybrid drive train, models of different components are introduced. On the basis of these models, control structures for the different subsystems are presented. Selected simulations show the potential of these control structures. As for the lateral dynamics, the potential to influence the vehicle dynamics by electric single-wheel motors is also investigated. For this purpose, an extended single-track model and approaches to the robust control of vehicle dynamics are used. Side-wind tests are presented as well as a hardware-in-the-loop testbed for the series hybrid drive train.

Apparatus and method for enhancing performance of an occupant restraint system in a vehicle

Abstract: An apparatus enhances performance of an occupant restraint system of a vehicle. A signal is generated based on vehicle dynamics and selectively places at least one safety module in a heightened state of awareness in response to the signal. The vehicle dynamics can include at least one parameter based on wheel movement. The parameter based on wheel movement can be provided by an anti-lock brake control system and/or a traction control system, or the like. The safety module capable of being placed in a heightened state of awareness can include a three-point seatbelt, an airbag, a pyrotechnic buckle pretensioner and/or an electro-mechanical retractor pretensioner or the like.

Vehicle/Guideway Dynamic Interaction in Maglev Systems

Abstract: The importance of vehicle/guide way dynamics in maglev systems is discussed. The particular interests associated with modeling vehicle/guideway interactions and ex­ plaining response characteristics of maglev systems for a multicar, multiload vehicle traversing on a single- or double-span flexible guideway are considered, with an emphasis on vehicle/guide way coupling effects, comparison of concentrated and distributed loads, and ride comfort. Coupled effects of vehicle/guideway interactions over a wide range of vehicle speeds with various vehicle and guideway parameters are investigated, and appropriate criteria for decoupling at critical vehicle speeds or crossing frequencies are identified.

R-ALOHA protocol for SS inter-vehicle communication network using head spacing information

Abstract: The purpose of the studies is to improve the safety of road traffic systems and the smooth control of the traffic flow by providing information to vehicles. This paper assumes that the vehicles incidentally close to each other, form and manage a locally autonomous decentralized dynamic network. An R-ALOHA (reservation-ALOHA) protocol for the spread spectrum (SS) inter-vehicle communication network using head spacing information is proposed which improve the conventional slot reservation methods. Since the near-far problem in SS communication is one reason for the degradation of system performance, this proposed scheme is shown to improve the efficiency of communication. The performance of the proposed system in the environment where vehicles are assumed to run freely on a highway is verified by computer simulation. It is shown that inter-vehicle communication can be smoothly carried out between one vehicle and the surrounding vehicles using the propose method.

Two Degree of Freedom/H∞ Controller Synthesis for Active Four Wheel Steering Vehicles

Abstract: SUMMARY This paper proposes an active front and rear wheel steering control system that simultaneously achieves both lateral acceleration and yaw rate responses always desirable regardless of changes in vehicle dynamics. First, this paper describes a method to accurately estimate physical parameters in the four wheel steering vehicle model, including the dynamics of a steering actuator, by applying the maximum likelihood estimation method. Next, the structure of the proposed front and rear steering control system is described. This control system has for its purpose to coincide both the lateral acceleration and yaw rate responses of the vehicle with the responses of the respective desirable reference models, as well as to make it a robust system against changes in vehicle dynamics and external disturbances. To achieve both objectives, a two-degree-of-freedom control system theory is employed. Then the paper shows the viability of the proposed steering control system through computer simulations. Finally, ...

Examination of Different Control Strategies of Heavy-Vehicle Performance

Abstract: Heavy vehicles play an economically important role in the transportation process, and their numbers have been increasing for several decades. The active safety of the highway system is an important consideration in the design of a heavy vehicle combination. In this paper, the handling characteristics of a 5-axle tractor-semitrailer is examined and used to test for the desired features of the vehicle's handling and stability. Using these results the optimal control criterion is derived for the vehicle. Four different control strategies are examined by using the Linear Quadratic Regulator (LQR) approach. These are, active steering of the rear wheels of the tractor; active steering of the wheels of the trailer; active torque control in the fifth-wheel joint; and active yaw torque acting on the tractor. These controllers are designed and examined using a simplified linear vehicle model. In addition to discussing the above-mentioned approaches, this paper discusses a method of modifying the slip angles at the tractor's rear (driven) axles, however the yaw torque at the tractor cg also can be controlled using what is called unilateral braking. As well, the replacement of the active torque control at the fifth wheel joint, by a control strategy based on the usage of controllable dampers at the fifth-wheel joint, will also be examined. In this case, a nonlinear mathematical model of the vehicle is used and a modified control strategy called the RLQR/H∞ approach is used to ensure the vehicle's performance in the presence of parametric uncertainties. The examination of these control strategies is conducted by using a sophisticated non-linear vehicle model, and the influence of these control strategies on the vehicle's directional and roll stability during severe path-follow lane-change manoeuvre is discussed.

A Tool for Lap Time Simulation

Abstract: The top Formula 1 and Indycar teams make large use of computer simulation to improve the performance of their cars and make the set-up process quicker on the circuit. The paper aims to present a lap time simulation software dedicated to racing cars. It is based on the background of vehicle dynamics research developed at the University of Brescia, Italy (see [1]). It should be stated that racecar dynamics is strongly nonlinear due to the fact that tyres are always very near the limit of adhesion. Moreover this makes the effect of lateral load transfer fundamental for the general balance of the car. Therefore Pacejka's Magic Formula has been used for lateral force/slip while longitudinal force computation is based on the assumption of a maximum longitudinal coefficient of friction μ. This is not only for simplicity but it is also due to lack of available data. The combined case is then based on the so-called "traction circle". Lateral and longitudinal load transfer and downforce as well as their effects on tyre load are taken into account. The vehicle model is capable of following a trajectory acquired with the on-board instrumentation. Also, the use of genetic algorithms enables the program to find the optimum cornering line for any given track. Some results are shown and compared with real world data.

Sliding mode control of an AUV in the diving and steering planes

Abstract: The problem of controlling an autonomous underwater vehicle (AUV) in the diving and steering planes is addressed. For each plane of motion, a controller is designed using sliding mode control theory. Each controller design is based on a nonlinear model of the vehicle that is valid for the respective plane. The paper provides a short review of sliding mode control theory, and describes the models of a prototype vehicle in the diving and steering planes. Numerical simulations illustrate the performance of the controllers developed.

Optimal Preview Control of a Two-dof Vehicle Model Using Stochastic Optimal Control Theory

Abstract: SUMMARY An optimal preview control algorithm is applied to a two degree of freedom(dof) vehicle model travelling with constant velocity on a randomly profiled road. The road roughness is modelled as a homogeneous random process being the output of a linear first order filter to white noise. The input from the road irregularity is assumed to be measured at some distance in front of the vehicle and this measured infonnation is utilized by the active controller to prepare the system for the ensuing input. The preview control algorithm is obtained by minimizing a quadratic performance index and by describing the average behaviour of the system by the covariance matrix of the vehicle response state vector. Results are presented for full state feedback and significant improvements in sprung mass acceleration, suspension working space and road holding are observed.

Kinematic Geometry of Wheeled Vehicle Systems

Abstract: This paper utilizes a kinematic-geometric approach to study the first-order motion characteristics of wheeled vehicles on even and uneven terrain. The results obtained from first-order studies are compared to those obtained from second order kinematic analyses, and special situations where the first-order analysis is inadequate are discussed, This approach is particularly suited for studying actively actuated vehicles since their designs typically do not include intentional passive compliances. It is shown that if a vehicle-terrain combination satisfies certain geometric conditions, for instance when a wheeled vehicle operates on even terrain or on a spherical surface, the system possesses a singularity-it possesses finite range mobility that is higher than the one obtained using Kutzbach criterion. On general uneven terrain, the same vehicles require undesirable 'kinematic slipping' at the wheel-terrain contacts to attain the mobility that it possesses on these special surface The kinematic effects of varying the vehicle and/or terrain geometric parameters from their nominal values are discussed. The design enhancements that are required in existing off-road vehicles to avoid kinematic slipping are presented for a class of vehicles that include two-wheel axles in their designs.

Robust stabilization of vehicle dynamics by active front wheel steering control

Abstract: The study of designing steering control systems for vehicles has attracted much attention, with the purpose of improving maneuverability and stability. Most of the vehicles models used to represent the dynamics were linear ones. Because of this, the control has to be restricted, at least theoretically, within a small range of steering angle, and may not be enough to compensate stability in critical motions. The purpose of this paper is to present a control strategy of the active front wheel steering system to protect the vehicle from spin and to realize the improved cornering performance. For this, the mechanism of vehicle spin behavior is analyzed and explained using concepts of bifurcation theory. The vehicle destabilization is shown to be caused by a saddle-node bifurcation and it depends heavily on a rear tire side force saturation. Based on these observations, the saturation characteristics of rear tires are modeled by a linear function with uncertainty terms of a special structure. Then the linear H/sup /spl infin// control theory is applied to design a front wheel steering controller which compensates the instability against the nonlinear uncertainty.

Experimental study on a learning control system with bound estimation for underwater robots

Abstract: Underwater robotic vehicles (URVs) have become an important tool for various underwater tasks because of their greater speed, endurance, depth capability and a lower risk factor than human divers. However, most vehicle control system designs are based on simplified vehicle models and often result in poor vehicle performance due to the nonlinear and time-varying vehicle dynamics having parameter uncertainties. This paper describes a new vehicle control system capable of learning and adapting to changes in the vehicle dynamics and parameters. This control system is compared with a conventional linear control system through extensive wet tests. Results show the learning and adapting capabilities of the presented control system.

Neural-adaptive nonlinear autopilot design for an agile anti-air missile

Abstract: Previous research has shown that neural networks can be used to improve upon approximate dynamic inversion controllers in the case of uncertain nonlinear systems. In the one possible architecture, the neural network adaptively cancels linearization errors through on-line learning. Learning may be accomplished by a simple weight update rule derived from Liapunov theory, thus assuring the stability of the closed-loop system. In this paper, the authors apply this methodology to design a bank-to-turn autopilot for an agile anti-air missile. First, a control scheme based on approximate inversion of the vehicle dynamics is presented. This nonlinear control system is then augmented by the addition of a feedforward neural network with on-line learning. Finally, the resulting control law is demonstrated in a nonlinear simulation, and its performance is evaluated relative to a more traditional gain-scheduled linear autopilot. (Author)

Impact dynamics of Space long reach manipulators

Abstract: The problem of impact dynamics of Space robotic systems that consist of a rigid manipulator supported by a flexible deployable structure is addressed. Due to joint back-drivability and the dynamic coupling between the manipulator and its supporting structure, unknown motion of the system occurs after it makes impulsive contact with the environment. A method that uses the system's dynamic model is proposed to estimate the motion of the system after impact. This method which can be used to find ways to minimize the impact effect and vibrations of the supporting structure due to impact, is verified experimentally using the MIT Vehicle Emulation System (VES II). The experimental results show that the impact force and the system motion after impact can be reduced if the manipulator configuration prior to impact and the controller gains are properly selected.

Passive and Semi-Active Airspring Suspensions for Rail Passenger Vehicles—Theory and Practice

Abstract: The performance of passive and semi-active secondary airspring suspension systems on rail passenger vehicles has been studied theoretically and experimentally. Classical and modern optimal control ...

Stabilization of steady motions of an underwater vehicle

Abstract: We show how to stabilize underwater vehicle dynamics for a six degree-of-freedom vehicle modeled as a neutrally buoyant, submerged rigid body in an ideal fluid. Stabilization is achieved by applying external torques to the vehicle that mimic the kind of torques that are naturally induced when the vehicle's center of gravity is lower than its center of buoyancy. This approach makes the controlled system resemble the uncontrolled system in structure, and we can mimic our analysis of open-loop stability of a bottom-heavy underwater vehicle to study closed-loop stability of the controlled vehicle. We show that the closed-loop system has Lie-Poisson form and prove closed-loop stability using extensions to the energy-Casimir method. A resulting property of the control law is robustness to model parameter uncertainty.