Showing papers on "Vehicle dynamics published in 1992"

Kinematics, dynamics and control of wheeled mobile robots

Abstract: The controllability of nonholonomic robot systems is proved for six common wheel and axle configurations that possess two or three degrees of freedom. After the kinematics and dynamics were modeled using the synchro-drive vehicle as an example, it was proved that continuous feedback stabilization of the vehicle to an equilibrium point is impossible. The dynamic model so developed is also used to prove that simple controllers are sufficient to guarantee stability for the drive- and steering-angle components of synchro-drive vehicles. Although the underlying control systems are stable, the experimental results demonstrated that potential-field navigation can lead robot trajectories to an unexpected invariant set. The results reported can easily be extended to the modeling and control of other mobile robot systems. >

A system level study of the longitudinal control of a platoon of vehicles

Abstract: This paper presents a preliminary system study of a longitudinal control law for a platoon of nonidentical vehicles using a simplified nonlinear model for the vehicle dynamics This study advances the art of automatic longitudinal control for a platoon of vehicles in the sense that is considers longer platoons composed of nonidentical vehicles; furthermore, the longitudinal control laws presented in this study take advantage of communication possibilities not available in the recent past

Dynamics of rigid bodies undergoing multiple frictional contacts

Abstract: Two key problem areas in the dynamics of rigid bodies with multiple frictional contacts are solved. First, the modeling of rigid body collisions is addressed. Second, an accurate model that will predict the contact forces is sought. The emphasis is on correct phenomenological and quantitative modeling. An approach to the simulation of mechanical systems with multiple, frictional constraints is proposed which is free of inconsistencies. This method is illustrated with the help of a simple planar example. >

Modeling and Model Simplification of Aeroelastic Vehicles: An Overview

Abstract: The rigid-body degrees of freedom and elastic degrees of freedom of aeroelastic vehicles are typically treated separately in dynamic analysis. Such a decoupling, however, is not always justified and modeling assumptions that imply decoupling must be used with caution. The frequency separation between the rigid-body and elastic degrees of freedom for advanced aircraft may no longer be sufficient to permit the typical treatment of the vehicle dynamics. Integrated, elastic vehicle models must be developed initially and simplified in a manner appropriate to and consistent with the intended application. This paper summarizes key results from past research aimed at developing and implementing integrated aeroelastic vehicle models for flight controls analysis and design. Three major areas will be addressed; 1) the accurate representation of the dynamics of aeroelastic vehicles, 2) properties of several model simplification methods and 3) the importance of understanding the physics of the system being modeled and of having a model which exposes the underlying physical causes for critical dynamic characteristics.

Integrated simulation for rapid development of autonomous underwater vehicles

Abstract: The autonomous underwater vehicle (AUV) integrated simulator has been designed to support complete scientific visualization of AUV vehicle performance. High-resolution 3D graphics workstations can provide real-time representations of vehicle dynamics, control system behavior, mission execution, sonar processing and object classification. Use of well-defined, user-readable mission log files as the data transfer mechanism allows consistent and repeatable simulation of all AUV operations. Examples of integrated simulation are provided using the Naval Postgraduate School AUV, an eight-foot, 387-pound untethered robot submarine designed for research in adaptive control, mission planning, mission execution, and post-mission data analysis. >

Rapid prediction of high-alpha unsteady aerodynamics of slender-wingaircraft

Abstract: Most aerospace vehicles, although designed for hypersonic cruise at low angles of attack, often have to perform rapid maneuvers at high angles of attack from low supersonic down to low subsonic speeds. There is, therefore, a need for rapid prediction of the nonlinear high-alpha vehicle dynamics of slender-wing aircraft in that speed range. The present paper describes such a prediction method, which can account for the nonlinear dynamic effects of leading-edge vortices at angles of attack, yaw, and roll. A comparison with existing experimental results shows that the accuracy of the prediction is satisfactory for preliminary design as long as breakdown of the leading-edge vortices does not occur.

Sensor system for dynamic control of vehicle - has pair of sensors straddling each axis and with central processor

Abstract: Pairs of sensors are mounted each side of each of the three axes through the centre of gravity of the vehicle. The sensor outputs are collected by a central processing unit and the rotational and linear movements about and along each axis are computed. This enables the vehicle dynamics to be controllled, e.g. steering, active suspensions etc. The sensor pairs are directed in opposite ways and thus together provide the required information for each axis. The system can compute the dynamic condition for any selected point of the vehicle to enable, e.g. the separate suspension elements to be controlled. USE/ADVANTAGE - Predicting behaviour of motor vehicle. Centrallised control; min. of sensors; active dynamic control.

Impact of dynamic fluid slosh loads on the directional response of tank vehicles

Abstract: SUMMARY A comprehensive directional dynamics model of a tractor-tank trailer is developed by integrating a non-linear dynamic fluid slosh model to the three-dimensional vehicle dynamics model. The nonlinear fluid slosh equations are solved in an Eulerian mesh to determine dynamic fluid slosh loads caused by the dynamic motion of the vehicle. The dynamic fluid slosh forces and moments are coupled with the vehicle dynamics model to study the directional response characteristics of tank vehicles. The directional response characteristics of partially filled tank vehicles employing dynamic slosh model are compared to those employing quasi-dynamic vehicle model, for steady as well as transient directional maneuvers. Simulation results reveal that during a steady steer maneuver, the dynamic fluid slosh loads introduce oscillatory directional response about a steady-state value calculated from the quasi-dynamic vehicle model. The directional response characteristics obtained using the quasi-dynamic and dynamic fl...

A neural network approach to failure diagnostics for underwater vehicles

Abstract: The author addresses the proposed use of Kalman filters and artificial neural networks to provide the detection and isolation of impending system failures. Such system health diagnosis is necessary for the overall success of mission controllers for autonomous underwater vehicles (AUVs). Two examples of network designs are given. The first addresses the identification of anomalous changes to the vehicle's acceleration behavior resulting from possible propulsion system changes or loss of propulsion efficiency from fouling. The second example relates to the identification of excessive frictional loads in the propulsion drive train that may cause motor failure. In each case, the training method and the resulting decision surface characterization of the networks so designed are described. >

Combined Longitudinal and Lateral Control of a Platoon of Vehicles

Abstract: In this paper, we consider the problem of combined longitudinal and lateral control of a platoon of non-identical vehicles on a curved lane of a highway. Based on nonlinear models of vehicles' combined longitudinal and lateral dynamics, we propose nonlinear control laws for a platoon of vehicles accelerating on a curved lane of highway. The implementation issues regarding the needed sensors, estimators, guidance system, and communication link are discussed. Simulation results show that the proposed control laws perform well, for roads with suitably large radius of curvature, under nominal operation.

Modeling and feedback control of nonholonomic mobile vehicles

Abstract: A complete dynamic model of mobile vehicles moving on nonplanar surfaces under nonholonomic and dynamic constraints is presented. The kinematic control of such systems is examined, and the invariant manifold technique is introduced for steering a nonholonomic mobile vehicle to an invariant manifold which is relatively locally-locally controllable. A closed-loop control strategy based on the invariant manifold technique is formulated and applied to the control of nonholonomic vehicles. Tracking control of such vehicles is demonstrated with both holonomic and nonholonomic reference trajectories. >

The Application of Time Delay Control to an Intelligent Cruise Control System

Abstract: This paper presents an application of Time Delay Control to an intelligent automotive cruise control system. In this system, a vehicle is equipped with a ranging sensor which measures the distance between a preceding car and itself. The relative distance between the two vehicles is the control output [the state] of the system and the dynamics of the leading car are treated as a disturbance. The performance of the Time Delay Control Method in this intelligent longitudinal cruise control system was evaluated using a one-fifth scale car model. Through simulations and experiments, the Time Delay Control technique is shown to be well suited for intelligent cruise controls because of its rapid estimation of system dynamics changes and ease of implementation.

Modelling The Dynamics Of Route Guidance

Abstract: This paper concentrates on simulation modelling aimed at studying the relative benefits of the dynamic elements of route guidance systems within the two DRIVE projects CARGOES and LLAMD.

Dynamics and Controls in Maglev Systems

Abstract: The dynamic response of magnetically levitated (maglev) ground transportation systems has important consequences for safety and ride quality, guideway design, and system costs. Ride quality is determined by vehicle response and by environmental factors such as humidity and noise. The dynamic response of the vehicles is the key element in determining ride quality, and vehicle stability is an important safety-related element. To design a proper guideway that provides acceptable ride quality in the stable region, vehicle dynamics must be understood. Furthermore the trade-off between guideway smoothness and the levitation and control systems must be considered if maglev systems are to be economically feasible. The link between the guideway and the other maglev components is vehicle dynamics. For a commercial maglev system, vehicle dynamics must be analyzed and tested in detail. In this study, the role of dynamics and controls in maglev vehicle/guideway interactions is discussed, and the literature on modeling the dynamic interactions of vehicle/guideway and suspension controls for ground vehicles is reviewed. Particular emphasis is placed on modeling vehicle/guideway interactions and response characteristics of maglev systems for a multicar, multiload vehicle traveling on a single- or doublespan flexible guideway, including coupling effects of vehicle/guideway, comparison of concentrated and distributed loads, and ride comfort. Different control-law designs are introduced into vehicle suspensions when a simple two-degree-of-freedom vehicle model is applied. Active and semiactive control designs for primary and secondary suspensions do improve the response of vehicle and provide acceptable ride comfort. Finally, future research associated with dynamics and controls of vehicle/guideway systems is identified.

Real-Time Simulation of Drive Chaines for Use in Dynamical Engine Test Stands

Abstract: In this paper, a dynamical engine test stand is presented which may be used as an advanced tool for combustion engine optimization and control. To simulate the dynamics of load changes occuring in a driving vehicle, a model of the car body including drive line, differential and wheels and a driver simulation have been developed and implemented on the test stand. Simulation results are presented and discussed.

The active suspension between customer benefit and technological competition

Abstract: This paper presents the attempts of BMW, in Germany, to define an appropriately designed active suspension system, based on vehicle dynamics measurement and subjective driver rating. It first surveys existing types of suspension systems systematically, and discusses the theoretical scope for their improvement. The following BMW vehicles were investigated: (1) a series production vehicle with active hydro- pneumatic suspension; (2) a test set-up with fully active suspension; (3) a test set-up with active hydro-pneumatic suspension; and (4) a different series production vehicle. Subjective and objective functional assessments were given of the following features of the vehicles: (1) vertical vibrational comfort; (2) handling (lateral and rolling movements); and (3) superimposed dynamics. The hardware requirements for active suspension are discussed. Finally, several findings are presented, based on measurements and on the subjective assessments of a considerable number of drivers. Customers seem to appreciate active suspension, if it is sufficiently effective. However, the costs of such suspension systems are still very high. For the covering abstract see IRRD 870290.

Prospects of the german multibody system research project on vehicle dynamics simulation

Abstract: SUMMARY The German Research Council (DFG) decided 1987 to establish a nationwide research project devoted to dynamics of multibody systems. In this project 14 universities and research centers are cooperating with the goal to develop a general purpose multibody system software package. This concept provides the opportunity to use a modular structure of the software, i.e. different multibody formalisms may be combined with different simulation programmes via standardized interfaces. For the DFG project the database RSYST was chosen using standard FORTRAN 77 and an object oriented multibody system datamodel was defined. According to the modular concept the requirements of vehicle system dynamics as tire models or railway wheel-rail models, respectively, are easily met. The Iitis benchmark problem is used to demonstrate some features of the object oriented datamodel.

A Controller For Autonomous Intelligent Cruise Control - A Preliminary Design

Abstract: This paper presents a preliminary design for an Autonomous Intelligent Cruise Control (AICC). Part of the Swedish RTI program, the goals for the AICC are to adapt the velocity of the host car in order to keep the cruise speed desired by the driver. This new system will also be able to detect a preceding vehicle, measure the distance to it and adapt the velocity of the host car, thus maintaining a safe distance to the vehicle ahead.

Indirect adaptive fuzzy controllers

Abstract: Many classical control methods are based upon assumptions of linearity and stationarity of the process to be controlled. For the case of motion control of a land vehicle in an unstructured outdoor environment these assumptions do not hold, due to complex vehicle interactions with its surroundings and time--varying environmental conditions. The large number of possible future platforms leads to the desire to produce motion controllers which are generally applicable to a wide range of vehicles with little a priori knowledge of vehicle dynamics. Intelligent, self--learning, systems promise many of the desired features for such controllers. This thesis investigates the use of intelligent controllers for autonomous land vehicle motion control. A new class of fuzzy controller, the indirect adaptive fuzzy controller is proposed as a possible solution to this problem. This controller is then developed by combining on--line adaptive modelling with model causality inversion and on--line controller design. The resulting controller is an analogue of the indirect adaptive algebraic controller. A major advantages of this method is the separation of model convergence and control loops enabling the two aspects to be analysed separately. Demonstration of this work has been achieved by a series of simulation tests using a variety of vehicle models. A conventional front wheel steer road vehicle model has been used as well as two IFAC benchmark control problems (ship autopilot and passenger bus) to investigate the properties of the controller. To test the controller with realistic demand signals, a static rule-based piloting system has also been developed. These simulations have demonstrated i) the successful control of systems with little a priori vehicle knowledge ii) ability to adapt to continuous and sudden parametric changes in the process iii) good noise rejection properties iv) good disturbance rejection properties and v) ability to adapt to stationary loop non--linearities.

Minimum-Time Motion Planner for Mobile Robots on Uneven Terrains

Abstract: This paper presents a method for generating the minimum-time path and motions of a vehicle, taking into account, the relief, the obstacles, the ground surface characteristics, and the vehicle dynamics, including engine and gear.

CCD-based optical tracking loop design trades

Abstract: The design of a CCD-based pointing, acquisition, and tracking (PAT) system is discussed together and with the design of a CCD-based tracking loop architecture for a cost-effective PAT system which would be applicable to the full spectrum of lasercom link possibilities. Four separate CCD systems are considered, with sample rates of 30 Hz, 300 Hz, 1 kHz, and 10 kHz; in each case, the CCD architecture is designed to meet a set of performance goals in the presence of host-induced disturbance environments representative of the disturbance environments that might be expected on orbit due to typical spaceborne actuators and vehicle dynamics. The paper describes the PAT base architecture, the performance goals of the CCD, the component analysis models, and the rejection loop designs using the different CCD systems. The results demonstrate that it is possible to increase the system efficiency and decrease its complexity by using a faster sampling CCD rather than relying on inertial measurements to meet tight pointing requirements.

Handling control with additional rear wheel steering

Abstract: This paper shows how vehicle safety can be improved by fitting additional rear wheel steering. Details are provided of: a) lateral vehicle dynamics; and b) controller design. The results using a simulation were compared with results obtained when driving a car. The items measured included: a) steering response, including steering response during a double lane change; b) disturbance response; and c) robustness, including vehicle reaction when cornering. For the covering abstract see IRRD 870290.

Analysis of large truck crashes on freeway-to-freeway connectors

Abstract: An investigation into the relative safety of freeway-to-freeway connectors with respect to heavy trucks is undertaken. Using a three-dimensional, time- domain, force-based simulation model of heavy vehicle dynamics, boundaries are established relating various vehicle configurations, connector geometries, and driver behaviors to dynamic responses describing potential vehicle loss-of-control. A series of case studies is examined, attempting to position current driver/vehicle/roadway interactions within the proposed envelopes of safety. Results include a method for predicting vehicle performance in response to roadway design enhancements that improves existing margins of safety at freeway-to-freeway connectors.

Evaluation of nhtsa light vehicle handling simulations. final report

Abstract: This report contains evaluations of four light vehicle stability and control simulations developed for the National Highway Traffic Safety Administration (NHTSA): FOROL developed by Dynamic Research Inc., the "Intermediate Maneuver Induced Rollover Simulation" (IMIRS) and the "Advanced Dynamic Vehicle Simulation" (ADVS), both developed by the University of Missouri, and "Vehicle Dynamics Analysis, Non-Linear" (VDANL) developed by System Technology, Inc. The focus of these evaluations is each simulation's ability to accurately predict light vehicle responses during flat road handling and crash avoidance maneuvers. Each simulation is first described on an analytical basis. The overall modeling approach is described along with detailed descriptions of the modeling of the vehicle subsystems. For each simulation, any areas found to be inadequately modeled are reported. The ability of each simulation to predict flat road vehicle responses is evaluated by comparing the simulation predictions to experimentally measured vehicle responses. These comparisons are done in both the time and frequency domains. The intent of this report is only to evaluate the capabilities of each simulation in its current form, and recommend a direction for future work in this area. It is not the intent of these evaluations to determine if the developers of the simulations met the requirements of their contracts.

Inclusion of steering system freeplay in open-loop vehicle dynamic simulations

Abstract: SUMMARY This paper discusses the importance of properly modeling steering system compliance and freeplay in open-loop, fixed control vehicle dynamics simulations. A compliant steering system model is developed that can include power assisted steering effects. A second-order system representation of steering system dynamics is included in the model. Overall steering system freeplay, which includes contributions from the steering gear, steering linkage, and wheel bearings, is then included to more accurately represent the steering system of an actual vehicle. The techniques used to measure the parameters for this model are also presented. The steering system model, implemented in a nonlinear, 13 degree-of-freedom vehicle dynamics simulation, is presented and the simulation predictions compared with experimentally measured vehicle responses.