Vehicle System Dynamics

Published by Taylor & Francis
Online ISSN: 1744-5159
Print ISSN: 0042-3114
Presents a model reference adaptive control strategy for active steering of 2WS cars which is realized by steer-by-wire technology. The ideal fixed property of a steering system which is provided by a reference model is attained by D* control. The proposed method can treat the nonlinear relationships between the slip angles and the lateral forces on tires, and the uncertainties on the friction of the road surface, whose compensations are proved to be very important under critical situations. Some results of real time simulation with a steering equipment show the effectiveness of the proposed method
This paper investigates the integration of various subsystems of an automobile's chassis. The specific focus of this research is the integration of active suspension components with anti-lock braking (ABS) mechanisms. The performance objective for the integrated approach is defined as a reduction in braking distance over just anti-lock brakes. A two degree of freedom half car vehicle model is developed along with models for a hydraulic active suspension and an ABS system. For both subsystems, actuator dynamics are included. Individual controllers are developed for the subsystems and a governing algorithm is constructed to coordinate the two controllers. Simulations of the integrated controller and an ABS system demonstrate a significant increase in performance
This paper introduces the concept of regenerative damping in vibration control, the storage of energy normally dissipated by a passive viscous damper. A device, the Variable Linear Transmission, is proposed to accomplish this task. Analysis of the proposed device as a damper in a typical passenger vehicle is conducted for the cases in which the device's active component operates ideally and with actuation dynamics included. Results indicate that regenerative vibration control is feasible and can provide damping nearly identical to that of a passive viscous damper while storing the damped energy.
This paper describes a computer simulation study on performance of lateral guidance system for dual mode truck. A stability limit of vehicle lateral motion is analyzed by using 9 DOF vehicle dynamic model. Relations between DMT steering system and stability limit are shown. Experiments with actual dual mode truck is carried out to show the effectiveness of the simulation study. Both the simulation study and experiment show that lateral guidance with one side guide rail causes unstable vehicle motion. It is shown that the unstable motion can be suppressed by cutting off the power steering equipment in the guideway
The problem of linear preview control of vehicle suspension is considered as a continuous time optimal control problem. The proposed strategy does not use any a priori information about the second order statistics of the road irregularities. Thus the detailed stochastic models of the road inputs, usually not available in practice, are not required by the controller. The problem formulation and the analytical solution are given in a general form. The solution is applied to a two-degree-of-freedom vehicle model. The effects of preview information on ride comfort, road holding, working space of the suspension, and power requirements are examined. The results show potential in improving road holding properties. It is also demonstrated that the presence of preview drastically reduces power requirements, relieving the performance versus actuator power dilemma
In this paper, the authors design an adaptive control scheme for electronic throttle that achieves good tracking of arbitrary constant speed commands in the presence of unknown disturbances. The design is based on a simplified linear vehicle model which is derived from a validated nonlinear one. The designed control scheme is simulated using the validated full order nonlinear vehicle model and tested on an actual vehicle. The simulation and vehicle test results are included in this paper to show the performance of the controller. Due to the learning capability of the adaptive control scheme, changes in the vehicle dynamics do not affect the performance of the controller in any significant manner.
To enable a realistic assessment of the aeroelastic phenomena of aircraft, a simultaneous application of computational fluid dynamics (CFD), computational structural mechanics and flight mechanics has to be performed. Each discipline has developed powerful specialized tools which have to be adapted for multidisciplinary applications. The combination of CFD and elastic multibody systems is well suited for the simulation of a range of aircraft applications, especially for aircraft ground dynamics. Approaches to a coupling of elastic multibody systems and computational fluid dynamics have been performed using close coupling, that is a modal approach, and loose coupling, that is by co-simulation. In the article the applied programs and the coupling methods are presented. Advantages and limits of using multibody simulation as compared to the direct use of FEA methods for the representation of structural dynamics are discussed. Results of coupled steady and unsteady simulations are presented. Finally, an approach to the aeroelastic trim problem is shown.
This report gives a preview to a state-of-the-art paper and a special session which are devoted to the problem of the applicability of multibody computer codes to vehicle system dynamics. These activities were initiated at the 11th IAVSD Symposium 1989 in Kingston, CAN, followed by a workshop in Herbertov, CSR, and to be reported at the 12th IAVSD Symposium in Lyon, 1991. The concluding documentation well be a special issue of the VSD journal. The status of this report is what has been achieved up to May 1991.
The development of advanced railway vehicles requires an efficient modelling and simulation of wheel-rail systems under complex conditions and maneuvers. For that reason, the multibody system simulation software SIMPACK was enhanced recently with a generally applicable wheel-rail contact modeule to be outlined in this paper. This module comprises the possibility of applying a constrained or an elastic contact model, single or multiple contact locations per wheel-rail element, analytic or measured track geometries including irregularities and rail profiles, varying in longitudinal direction (switches). A simulation study of a passenger car running through a switch demonstrates the efficiency of the constrained wheel-rail contact model extended for the simulation of multiple contacts. As a second example a freight train is investigated and its simulation results are compared to measurements in order to validate the simulation tool as well as the model.
For identifying the long time behaviour of nonlinear dynamical systems with respect to the influence of one or more system parameters, numerical bifurcation analysis is an ideal method. The objective of the paper is to describe a software environment for such an analysis basing on the principles of path-following or continuation under the specific viewpoint of an application on mechanical systems or more specifically, on railway vehicles being modelled as multibody system. Their stationary as well as their periodic behaviour is considered. Three major topics are of primary interest: The integration of the bifurcation software into a software package for the simulation of arbitrary mechanical systems; the direct calculation of periodic solutions (limit cycles), and the handling of differential algebraic equations (DAE). The algorithms are applied finally on the “realistic” simulation model of a railway vehicle running on a straight track.
For dynamically loaded lightweight structures fatigue strength is an important design criteria. In this paper a new method to predict fatigue lifetime is shown. This is based on the combination of frequency domain and time domain calculations, which allow lifetime prediction with reduced computational effort. The method is implemented to work in a concurrent engineering software environment together with a computer aided design (CAD), a finite-element-method (FEM) and a multibody system (MBS) program. The benefits of the new approach are demonstrated by applications to the bogie of a freight locomotive. The dynamic loads acting on the bogie are computed by multibody simultaion. The bogie frame is considered as an elastic body of the MBS and the highly nonlinear wheel rail contact is modeled quasi-elastically. For the ride on a straight track the equations of motion can be linearized and nonlinear differential equations. FEM yields the stresses in the most stressed locations of the bogie prediction is carried out in the MBS post-processing program FATIGUE.
It is a frequently observed phenomenon that curving of railway vehicles can involve friction-induced oscillations. The study presented in this paper investigates vibrations with a frequency of 80 Hz occurring at a light rail vehicle in Stuttgart in curves with radii between 50 and 200 m. The aim of the investigation was to identify the oscillation and transmission mechanism, and the dominant parameters within this. As the cause could not be clearly identified from the measurements, a multi-body simulation in the time domain was used. The model consisted of both vehicle and track and considered the structural dynamics of the wheelset and bogie frame up to 200 Hz. The system was modelled using the commercial MBS software SIMPACK. The identified model describes the oscillations observed at the real vehicle. The results proved to be useful in minimising the vibrations at the real vehicles.
This work proposes to approach Global Chassis Control (GCC) by means of model inversion based feedforward with allocation directly on the actuator commands. The available degrees of freedom are used to execute the desired vehicle motion while minimizing the utilization of the tyre's grip potential. This is done by sampled constrained least-squares optimization of the linearized problem. For compensation of model errors and external disturbances, high gain feedback is applied by means of an Inverse Disturbance Observer. The presented method is applied on a comparison of eight vehicles with different conguration of actuators for steer, drive, brake and load distribution. The approach shows a transparent and effective way to deal with the complex issue of GCC in a unitized way. It gives both a base for controller design and a structured way to compare different configurations. In practice, the transparency supports automatic on-board reconfiguration in case of actuator hardware failure.
Co-Simulation gives a suitable framework for coupling software-tools specialized for the application in different fields of mechanics and/or physics, particularly if based on different mathematical methods. For the computational analysis of a vehicle’s running behaviour usually a Multibody System approach is used while flexible tracks – representing for example a bridge - are best examined with the help of Finite Element software. Now, for the simulation of a vehicle running on a flexible track without neglecting the inherent interaction, an obvious and promising strategy is to simulate each of the two subsystems (vehicle and flexible track) with the appropriate software concurrently and to exchange the interfacing data at discrete communication points. To minimize the numerical effort, the track’s finite element model can be reduced modally to a linear description in a pre-processing step additionally; the resulting linear equations of motion of the track can then be solved analytically with high efficiency. An application of the strategy is demonstrated by a truck and the encounter of two railway vehicles each running on bridges.
Nowerdays, crosswind stability is a key topic for the homologation of railway vehicles and thus a pivotal boundary condition in their design proccess. In most countries the safety proof is based on the numerical multibody simulation of the driving behaviour of the vehicle assuming a worst case wind scenario. The conservativeness of this approach is aggravated by the uncertainties in the parameters of the simulation models. In this work some possible improvement of the safety proof are firstly discussed, mainly concerning the computational model of the vehicle. An alternative approach based on reliability techniques is then presented and discussed, finally leading to a more efficient assessment of the risk and thus to a reduction of the safety factors.
In modern railway industry the simulation of the behaviour of railway vehicles has become an important design method during the last years. Modern simulation packages offer modelling elements that are highly adapted for standard and unusual simulation scenarios. A specific application case is the simulation of a railway vehicle travelling through a switch. It makes high demands on the simulation software due to the inconvenient modelling elements needed: the changing rail profiles on the blade rail and in the crossing vee area as well as the guard rail with its additional contact at the back of the wheel. The article gives an overview over the state of the art in railway vehicle simulation and presents a simulation of a passenger car running through a switch as an application example.
This paper represents one of the results of the second Herbertov Workshop in 1992 on “Research Issues in Automotive Integrated Chassis Control Systems”. It was decided to bring together engineers who are actively involved in current software developments to report on the progress in integrated system analysis and design software for controlled vehicles. Therefore, after mentioning some of the principal requirements for such software, the state-of-the-art is summarized. Promising recent research and software developments are described and the application of some of these concepts to an actively controlled vehicle with preview is discussed. Throughout the article the ideas of concurrent analysis and design strategies are emphasized.
This paper presents fuzzy logic traction controllers and their effect on longitudinal vehicle platoon systems. A fuzzy logic approach is appealing for traction control because of the non-linearities and time-varying uncertainties in traction control systems. One fuzzy controller estimates the "peak slip" corresponding to the maximum tire-road adhesion coefficient and regulates wheel slip at that value. The other fuzzy logic controller regulates wheel slip at any desired value. The controllers' performance and robustness against changing road conditions and time- varying uncertainty is evaluated by simulation. The effect of traction control on longitudinal vehicle platoon systems is studied by simulation also.
The role of Computer Aided Engineering in vehicle development has been significantly increased during the last decade. Specialised simulation tools became very complex, however, growing demands on complexity and particularly interdisciplinary of vehicles and their simulation models have led to a number of approaches trying either to develop multidisciplinary simulation tools or to connect various specialised simulation tools by interfaces. This paper addresses some aspects of interconnection of the specialised simulation tools as one possibility for simulating complex mechatronic vehicle systems. It classifies the interfaces between specialised software packages in general, mentions some historical development of the interfacing and further discusses the examples of the implemented couplings between the Multibody System codes and Computer Aided Control Engineering tools. Finally, the performance of selected interfaces is compared on an example simulation of a controlled vehicle suspension.
We consider a simple model of a wheelset that supports one end of a railway freight wagon by springs with linear characteristics and dry friction dampers. We extend our earlier results to more realistic models, so in this presentation the linear kinematic contact relation in an earlier paper [True and Asmund, 2002] is replaced by the nonlinear rail/wheel contact geometry between a UIC60 rail and an S 1002 wheel profile. In addition we add a linear restoring force to control the yaw motion and finally add the axle side bearings to limit the maximum amplitude of the yaw oscillations. Stick-slip and hysteresis are included in our model of the dry friction. The resulting dynamics is nonperiodic and most likely chaotic. A bifurcation diagram and some interesting types of apparently chaotic motion are presented and discussed.
This paper presents design of the semi-active suspensions of trucks in order to fulfil conflicting demands: road friendliness and comfort. The spatial decomposition approach is proposed to design the suspension structure. The contribution of the semi-active suspension is verified by the experiments including cornering and braking with a complex truck simulation model.
In this paper a parameter identification method for multibody systems is applied to a 1:5-scaled two-axled railway vehicle with conical wheels on a roller rig with UIC 60 roller profiles. The aim is to demonstrate how parameter identification in connection with constrained multibody systems and dynamical measurements can be performed. The process of mathematical modelling and solution approach is described, where emphasis is laid on the structure of equations, modelling of the wheel-roller contact, numerical methods and the representation of the parameter identification method for the determination of the unknown stiffness and damping parameters as well as uncertain parameters like the coefficient of friction and manufacturing; imperfections of the vehicle. Additionally it is indicated that the 1:5-scaled railway vehicle can be utilized for running behaviour experiments with unconventional wheelset designs.
A generic wheelset structure is introduced allowing investigations with conventional as well as advanced unconventional wheelsets. The axles of this generic model can include variable camber angle and coupling. The coupling can be modelled rigidly or elastically, as a passive element with rotational damping or actively with creep control.The wheel profile is simplified by a dicone whereas the rail profile is that of a UIC 60-rail. Simulations are performed for the suspended single wheelset structure as well as for a simple bogie with two wheelset structures. The results indicate the influence of the parameters velocity, cone angle and camber angle on the tangent track response of several types of passive wheelset designs. For a bogie, so far being equipped with two conventional wheelsets, the simulation results are compared with experiments on a 1:5-sccaled roller rig.
Simulation in vehicle system dynamics has its historical origin in the analysis of the purely mechanical behaviour using mechanical multibody system models. In multibody dynamics very efficient numerical methods for the evaluation and for the time integration of the equations of motion are available. These methods have been extended step-by-step to more complex engineering systems that may contain e.g. flexible bodies and mechatronic or adaptronic devices. Multidisciplinary problems like the interaction of mechanical and hydraulic components or the interaction of vehicle dynamics and aerodynamics are handled conveniently by co-simulation techniques. The present paper summarizes some of these recent extensions of classical multibody dynamics such as multifield problems in the simulation of adaptronic devices, advanced models of contact mechanics and coupled problems including multibody dynamics, aerodynamics and structural mechanics.
Simulation in vehicle system dynamics has its historical origin in the analysis of the purely mechanical behaviour using mechanical multibody system models. In multibody dynamics very efficient numerical methods for the evaluation and for the time integration of the equations of motion are available. These methods have been extended step-by-step to more complex engineering systems that may contain e.g. flexible bodies and mechatronic or adaptronic devices. Multidisciplinary problems like the interaction of mechanical and hydraulic components or the interaction of vehicle dynamics and aerodynamics are handled conveniently by co-simulation techniques. The present paper summarizes some of these recent extensions of classical multibody dynamics such as multifield problems in the simulation of adaptronic devices, advanced models of contact mechanics and coupled problems including multibody dynamics, aerodynamics and structural mechanics.
Roller rigs have been built world-wide to research into the dynamics of railway vehicle and they have particularly been applied to the development of high-speed trains. This survey takes into consideration both full scale as well as small scale model roller rigs. Besides performance, most important experimental work and the emphasis of application, the scaling strategie of model test rigs and the differences involved in roller rig experiments are treated. Suggestions and analysis of railway vehicle dynamic behaviour.
Today, the simulation of the running behaviour of railway vehicles is usually carried out on the base of a multi-body system approach and under the assumption that the wheelsets and the rails are rigid bodies. Considering the strongly nonlinear characteristics of the wheel-rail contact which can be very sensitive even to small relative shifts, the question arises, whether elastic deformations of the wheelsets and the rails can have an influence on this contact and thereby on the running behaviour of the entire vehicle. Moreover, for a description of the vehicle-track interaction in the higher frequency range in which phenomena like noise and wear are located, the consideration of the structural dynamics of the wheelsets and the rails is essential. First, a simulation model of a railway vehicle is presented with special focus on the modelling of the wheelsets and rails as elastic bodies and their coupling by a nonlinear wheel-rail contact. Finally, the impact of these structural elasticities on the running behaviour of the vehicle is investigated; as an example, their influence on the critical speed and the limit cycle behaviour is presented.
This paper presents examples and indicates open problems for two different kinds of vehicle guideway interaction, their modelling and their computer simulation. The examples deal with low frequency interactions between vehicle and guideway (bridge crossing) as well as with vibrations in the acoustic range caused by eccentric rotating wheelsets.
This article presents models for wheels and tyres in the application field of real-time multi-body systems. For this rather broad class of applications it is difficult to foresee the right level of model complexity that is affordable in a specific simulation. Therefore we developed a tyre model that is adjustable in its degree of complexity. It consists of a list of stepwise developed sub-models, each at a higher level of complexity. These models include semi-empirical equations. The stepwise development process is also reflected in the corresponding implementation with the modelling language Modelica. The final wheel model represents a supermodel and enables users to select the right level of complexity in an unambiguous way.
In this paper a time-domain direct identification method is presented for the identification of vehicle system mass, damping and stiffness matrices, as well as for parameters of nonlinear componentswhich are "linear-in-the-parameters". The method is based on least-square type of error costs which are constructed from system dynamic equation. The estimated system parameters are then tuned to minimize each of these cost functions. The parameters are directly identified from the deduced algorithm without iteration. To demonstrate the proposed identification procedure, the method is applied to a four degree-of-freedom vehicle; different nonlinear suspension components, such as cubic springs, nonlinear hydraulic and frictional dampers and their combinations are considered. It can be seen that by using the proposed method, all the unknown system parameters are identified with sufficient accuracy, low memory and computation time.
This paper describes the modelling of an integrated mechatronic railway vehicle which results from the Mechatronic Train project. The vehicle model includes the use of some advanced control functions such as actively controlled independently rotating wheels and secondary suspension. Therefore an integrated approach for suspension, traction and steering control is needed.
This paper addressees the aspect of computer aided analysis and design of mechatronic systems with emphasis on their system dynamics and control. At first a rather general, however, perhaps also somewhat subjective definition of mechatronic systems is given. Focussing on ground vehicle systems (road, rail or aircraft on ground) the basic properties describing their system dynamics (handling, stability, vibrations) are characterized. The major mathematical models as well as analysis and design requirements are concluded from these properties. The main CAE tools under consideration are Multibody Systems (MBS) simulation, Finte Element Analysis (FEA) and Computer Aided Control Engineering (CACE). It is then argued that MBS is the proper choice for an integrating or synthesizing tool. However, the other CAE tools such as FEA, CACE, CFD (Computational Fluid Dynamics) and, last but not least, CAD (Computer Aided Design) are also needed. The paper therefore suggests using a connected “tool box” with MBS as the kernel and with bi-directional interfaces to and from the other CAE standard packages. The state-of-the-art of a tool chain is described and illustrated for a complex analysis and design issue of a “Mechatronic Train”.
An enhanced model of a passenger coach running on a straight track is developed. This model includes wheelsets modelled as rotating flexible bodies, a track consisting of flexible rails supported on discrete sleepers and wheel-rail contact modules, which can describe non-elliptic contact patches based on a boundary element method (BEM). For the scenarios of undisturbed centred running and permanent hunting, the impact of the structural deformations of the wheelsets and the rails on the stress distribution in the wheel-rail contact is investigated.
The article describes the application of a 1:5-scaled roller rig with a two-axled experimental vehicle to the design of a torque-controlled railway wheelset. Particular attention is drawn to the scaling problem and the dynamic similarity laws behind it and in addition to the chosen scaling strategy. For the controller design of the active wheelset the experiments with the scaled vehicle were combined with multibody computer simulations. The complete mechatronic system has therefore been modelled using the SIMPACK-MATLAB/Simulink interface. The steering behaviour, typical for this particular active wheelset, is demonstrated by results from roller rig experiments.
this paper. At the upper level, desired vehicle acceleration is computed based on vehicle range and range rate measurement. At the lower (servo) level, an adaptive control algorithm is designed to ensure the vehicle follows the upper level acceleration command accurately. It is shown that the servo-level dynamics can be included in the overall design and string stability can be guaranteed. In other words, the proposed control design produces minimum negative impact on surrounding vehicles. The performance of the proposed ACC algorithm is examined by using a microscopic simulation program---ACCSIM created at the University of Michigan. The architecture and basic functions of ACCSIM are described in this paper. Simulation results under different ACC penetration rate and actuator/engine bandwidth are reported. 1. INTRODUCTION Adaptive Cruise Control (ACC) systems were proposed as an enhancement to classical cruise control systems for ground vehicle speed regulation. ACC system controls the vehicle speed to follow a driver's set value when no lead vehicle is in sight. When a slower leading vehicle is present, the ACC controlled vehicle will follow the lead vehicle at a safe distance. ACC research first began in the 1960s [1], and has received evergrowing attention in the last decade. Their commercial implementation is not possible until recently with significant progresses in sensors, actuators, and other enabling technologies. It has been shown that PID or its variations produce satisfactory control results [2]. ACC algorithms of more complex forms have also been proposed and analyzed ([3], [4], [5]). Two large-scale field tests were also performed recently ([8], [9]), with regular drivers driving ACC vehicles on normal highways. Preliminary test results have shown that th...
This paper is part of an on-going research toward the development of a lane-departure warning system [1], one of the most technology-demanding active safety systems. The basic concept of the lane-departure warning system is to project vehicle trajectory, and compare with the perceived road geometry (obtained from vision systems) to calculate a performance metric termed "time to lane crossing" (TLC). When the calculated TLC is less than a threshold value, the control system will either issue warning signals or take intervention actions. To project the vehicle future trajectory accurately, we need to update vehicle parameters (speed, cornering stiffness, etc.) and estimate external disturbances (road super-elevation, wind gust, etc.). The estimation of external disturbances further depends on the vehicle parameters. Therefore, on-line estimation of road/tire characteristics is crucial for the TLC calculation and the overall lane-departure warning system. It is important to note that accurate road/tire friction estimation can also improve the performance of many other vehicle control/safety systems such as ABS, traction control, and 4WS systems. Recently, various methods to identify the road friction coefficients have been developed. Dieckmann [2] developed a method which allows the exact measurement of wheel-slip in the order of 10 -4 . From the information of measured wheel slip the road surface variation is detected. Eichhorn and Roth [3] used optical and noise sensors at the front-end of the tire and stress and strain sensors inside the tires tread and studied both "parameter-based" and "effect-based" road friction estimation methods. Ito et al. [4] uses the applied traction force and the resulting wheel speed difference between driven and non-driven wheels to estima...
Baseline closing-in, range time histories and phase plane trajectories The range versus range rate diagram in Figure 2 shows differences in how the control strategies operate. For the H&S controller, the straight-line trajectory to the final range for following at T h is simply the control objective function, (T dR/dt + R = R h ). Since the control action starts below the objective function, the vehicle simply coasts down in speed until the trajectory reaches the objective function and then the subordinate sliding control keeps the trajectory on the objective function with unobservable error in the figure. Since the objective function represents a first order linear differential equation with a time constant of 10 seconds, the time history of R is approximately an exponential function once the vehicle's trajectory in the phase plane fits the objective function. In comparison, the H ∞ control quickly goes through a few control iterations before it establishes a trajectory that takes the vehicle to the desired range with very small amounts of undershoot in R and overshoot in dR/dt. Once it gets organized the H ∞ control provides a smooth transition to the desired headway situation. There is only a very small amount of acceleration needed at the end to bring the speed of the headway-controlled vehicle up to the speed of the preceding vehicle. In contrast to the other controllers, use of the Fuzzy controller produces a fairly large undershoot in range which entails a fair amount of acceleration to bring the range rate to zero at the end of the closing-in maneuver. (See Figure 2.)
This paper compares design approaches for achieving a headway control functionality for trucks and buses. The approaches considered are fuzzy logic [1], H [2], and a strategy based on headway range and its derivative (range-rate) [3]. For heavy vehicles, the control unit has a number of nonlinearities to compensate for, including full accelerator saturation, engine characteristics, and a limited deceleration capability as may be influenced by rolling resistance, aerodynamic drag, and retarder capabilities. Performance properties of the controllers are derived from simulations of basic operational situations such as closing-in on a preceding vehicle that is traveling at a slower speed or following a vehicle whose speed varies. 1. HEADWAY-CONTROL CONSIDERATIONS The basic objective of headway control is to maintain a satisfactory separation between a preceding vehicle and a following vehicle equipped with a device that provides information concerning the range d
A temporal and spatial re-parameterization of the wellknown linear vehicle Bicycle Model is presented. This parameterization utilizes non-dimensional ratios of vehicle parameters called pi-groups. Investigation of these pigroups using compiled data from 44 published sets of Vehicle Dynamics reveals that the data does not span the pi-space, but instead follows a multi-dimensional line through pi-space with a Guassian distribution about this line. This Guassian distribution suggests numerical values for an `average' vehicle as well a maximum perturbation about the average. Stability analysis in the pi-space is then considered. A state-feedback controller is designed that utilizes the pi-space curve and the expected pi-perturbations to robustly stabilize the class of all vehicles subject to the distribution of vehicle parameters observed in the literature. Experimental verification is obtained using a scaled vehicle. I. Motivation The field of Robust Control made large advances in the 1980's and a framework for formally dealing with system uncertainty is fairly well understood (Zhou and others 1996). However, in most of the approaches to Robust Control, there has been little work done to utilize a specific non-dimensional structure to the problem in order to define plant deviations. An example of a system where a specific structure could be exploited is that of vehicle control. With extensive previous work that has been done on Automated Highway systems or Intelligent Vehicles (Shladover 1995), it has been found that repeated manipulation of the various controllers is necessary to achieve adequate performance for different vehicles. This re-calibration of vehicle controllers is expected since the actual vehicle plant is changing from vehicle-to-vehicle. In this work we co...
A worst-case vehicle evaluation methodology is presented in this paper. This evaluation method identifies worst-case excitation signals so that the vehicle performance under extreme conditions can be assessed. Two case study examples are presented to illustrate the design procedure and potential benefits of this method: the rollover and jackknifing of an articulated truck, and the evaluation of an active yaw control system. In both cases, the worst-case method was able to produce unstable results at very modest steering/braking levels.
The AVHS architecture of the California PATH program organizes traffic into platoons of closely spaced vehicles. Platoons are formed and broken up by two longitudinal control maneuvers, merge and split. A third longitudinal maneuver, decelerate to change lanes, allows a platoon switching from one lane to another to enter its new lane at a safe spacing and speed. This paper presents a robust control strategy for these maneuvers. Safety is assured by forcing the velocity of the trail platoon to remain under a maximum safe velocity boundary. When safety is not threatened, the vehicles' jerk and acceleration remain within comfort limits. Because no timed nominal trajectories are used, completion of the maneuvers does not depend on vehicles meeting prescribed acceleration capabilities. 1. Introduction The Automated Vehicle/Highway System architecture of the California PATH program organizes traffic into platoons of closely spaced vehicles [1]. The tight spacing between cars within a plato...
This paper describes how a multibody symbolic code generator, AutoSim^TM, was used to generate Sayers 2/6 comprehensive vehicle dynamics models for RTS applications with HITL using an ordinary PC. AutoSim takes as input a description of the multibody system mostly in geometric terms such as body degrees of freedom (DOF), point locations, directions of force vectors, etc. [5, 6]. From this information, it derives equations of motion as ODEs, and generates computer source code (C or Fortran) to solve them. The source code is well-suited for RTS applications, as will soon be demonstrated.
Overall assessment of control strategies 
This paper presents work on a set of novel strategies for achieving local (or vehicle-based) tilt control. A linearised dynamic model is developed for a modern tilting railway vehicle. It addresses the problems associated with straightforward feedback control, and presents the currently used command-driven with precedence strategy. Two new advanced schemes are proposed, a model-based estimation, and a robust H# based approach. The performance of the control schemes is assessed via appropriate simulation results and a recently proposed tilt control assessment method
A traffic accident is a complex phenomenon with vehicles and human beings involved. During a collision, the vehicle occupant is exposed to substantial loads, which can cause the occupant injuries that depend on the level of passive safety, as well as on the occupant's individual characteristics. Correct estimation of injury severity demands a validated human body model and known impact conditions. A human body modelling procedure for the purpose of accident analysis is introduced. The occupant body has been modelled as a multibody system with rigid body segments connected. Geometrical and inertial properties of individual body segments were estimated using computed tomography. Frontal impact conditions were simulated on a sled test facility, while the human body dynamic response was measured. Comparison of experimental data and computer simulation revealed an influence of joint resistive properties on the occupant motion in collisions. The difference between measured and simulated response was minimised using optimisation method. Individualised human body modelling procedure enabled better prediction of the occupant motion during vehicle collision and thus more precise estimation of possible injuries in real-life traffic accidents.
This paper presents a new methodology for suspension control in view of global chassis control, developed in particular to guarantee greater driving safety and comfort. The control of the suspension subsystem allows the vehicle road holding (safety) and passenger comfort to be improved, but not at the same time. In order to reach them for every driving situation, an 'adaptive' two-degrees-of-freedom controller for active suspensions is proposed. This control architecture is 'open' and could be linked and aggregated to many other controllers of vehicle dynamics. This control strategy ensures, on the one hand, the robustness in performances with respect to parameter uncertainties and, on the other hand, the trade-off between road holding and comfort. The proposed design is based on the LPV/[image omitted] ∞ theory. Robust stability and performances are analysed within the μ-analysis framework.
Summary In this paper, the sensitivity analysis is applied to the development of high performance adaptive hydraulic mounts. The analysis allows us to select the most effective design parameters for tuning an adaptive mount to different road and engine conditions. It is shown that in the low frequency road excitation, the upper chamber compliance and inertia of the fluid column in the inertia track are the most influential properties in changing the dynamic stiffness of the hydraulic mount. These properties for the high frequency engine excitations are the upper compliance and the inertia of the fluid column of the decoupler. For tuning the adaptive mount to different road and engine excitation, a global optimization technique is used to find the magnitude of the adjusting parameters to minimize objective functions in low and high frequency excitations. The results indicate significant improvement over conventional hydraulic mounts. It is further shown that when the upper compliance is used as the adjusting parameter, a simple on-off control which is triggered by the engine revolution and vehicle speed is sufficient for tuning the adaptive mount.
Summary This paper describes a flexible and modular 9-degrees-of-freedom nonlinear dynamic handling model for a tractor-semitrailer combination vehicle. The equations of motion are derived from the fundamental equations of dynamics in Euler's formulation, with the use of general computer-algebra software. The primary aim of the model is simulation of handling scenarios with active yaw control, using unilateral braking. However, it may also prove useful in other areas of tractor-semitrailer handling analysis or hardware-in-the-loop simulations. The model is formulated as a state-space model that may be implemented in standard simulation environments. A Simulink implementation is presented, and simulation results are compared with experiments to validate the model.
Collision warning/collision avoidance (CW/CA) systems must be designed to work seamlessly with a human driver, providing warning or control actions when the driver's response (or lack of) is deemed inappropriate. The effectiveness of CW/CA systems working with a human driver needs to be evaluated thoroughly because of legal/liability and other (e.g. traffic flow) concerns. CW/CA systems tuned only under open-loop manoeuvres were frequently found to work unsatisfactorily with human-in-the-loop. However, tuning CW/CA systems with human drivers co-existing is slow and non-repeatable. Driver models, if constructed and used properly, can capture human/control interactions and accelerate the CW/CA development process. Design and evaluation methods for CW/CA algorithms can be categorised into three approaches, scenario-based, performance-based and human-centred. The strength and weakness of these approaches were discussed in this paper and a humanised errable driver model was introduced to improve the developing process. The errable driver model used in this paper is a model that emulates human driver's functions and can generate both nominal (error-free) and devious (with error) behaviours. The car-following data used for developing and validating the model were obtained from a large-scale naturalistic driving database. Three error-inducing behaviours were introduced: human perceptual limitation, time delay and distraction. By including these error-inducing behaviours, rear-end collisions with a lead vehicle were found to occur at a probability similar to traffic accident statistics in the USA. This driver model is then used to evaluate the performance of several existing CW/CA algorithms. Finally, a new CW/CA algorithm was developed based on this errable driver model.
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 steady state or transient conditions.
In this article, two kinematics-based observers are proposed to estimate the vehicle roll and pitch angles by using an inertial measurement unit. The observers are mathematically proven to be stable if the vehicle yaw rate is not zero. With a design variation of the observer gains, the estimated roll or pitch angle is shown to further asymptotically converge to the true value, eliminating possible errors caused by the biases of the acceleration signals. Simulation results show that accurate estimation of both pitch and roll angles can be achieved without the help of external sensors such as global positioning systems, either by using the accelerometer-based reference pitch or roll angle as the maneuver varies, or by using an observer with zero steady-state error property.
Top-cited authors
Huei Peng
  • University of Michigan
Stuart L. Grassie
Wanming Zhai
  • Southwest Jiaotong University
Sebastian Stichel
  • KTH Royal Institute of Technology
Stefano Bruni
  • Politecnico di Milano