Showing papers in "Vehicle System Dynamics in 1997"
TL;DR: In this article, the steady-state empirical "Magic Formula" tire model was used to model the acceleration and braking properties of the Delft Tyre 97, and a full set of equations of the steady state part of the model of the new version was presented.
Abstract: The tyre force and moment generating properties connected with the vehicle's horizontal motions are considered. Knowledge of tyre properties is necessary to properly design vehicle components and advanced control systems. For this purpose, mathematical models of the tyre are being used in vehicle simulation models. The steady-state empirical ‘Magic Formula tyre model’ is discussed. The aligning torque description is based on the concepts of pneumatic trail and residual torque. This facilitates its combined slip description. Following Michelin, weighting functions have been introduced to model the combined slip force generation. A full set of equations of the steady-state part of the model of the new version ‘Delft Tyre 97’ is presented. The non-steady state behaviour of the tyre is of importance in rapid transient maneuvres, when cornering on uneven roads and for the analysis of oscillatory braking and steering properties. A relatively simple model for longitudinal and lateral transient responses...
458 citations
TL;DR: In this paper, an overview of the methods to describe the catenary and the pantograph system dynamics is presented, including the interaction between current collectors and overhead equipment, the acquisition of the model data and the verification are presented.
Abstract: SUMMARY The pantograph-catenary system with its dynamic behaviour turned out to be a crucial component for new train systems required to run at higher speeds. With the present systems, operational limitations have to be accepted when running with several pantographs in the train set, when tilting trains are employed, when running on low quality catenary sections or when stricter noise reduction regulations are forcing lower noise emissions also for the pantographs. This paper gives an overview of the methods to describe the catenary and the pantograph system dynamics. Furthermore, aspects concerning the interaction between current collectors and overhead equipment, the acquisition of the model data and the verification are presented. Finally various constructions of passive pantographs and proposals for active control concepts are discussed.
196 citations
TL;DR: In this paper, an attempt to introduce the use of computer-based analyses to predict wear-caused wheel and rail profile alterations and to maximize the mileage performance by selecting the optimum vehicle system parameters for running gears.
Abstract: SUMMARY The alteration in wheel and rail profiles due to wear involves considerable vehicle and track-maintenance costs, and influences the loading capacity of the rails, as well as the operation safety and riding comfort of the vehicles. In the past twenty years a vehicle dynamics, contact mechanics and tribology based research work has emerged which is also recently continuous in an international scale, and this research is more and more intensive. Parallel to the growing possibilities of computer based analyses, several algorithms and numerical procedures have been elaborated, as well as measurement based experiments have been carried out to establish the reliable prediction of wear-caused wheel and rail profile alterations and to maximise the mileage performance by selecting the optimum vehicle system parameters for running gears operating on a selected railway line or a whole network under specified -in general inherently stochastic - traffic conditions. This paper takes an attempt to introduce the e...
158 citations
TL;DR: In this paper, the ground-hook concept is extended to the several variants which enable to decrease criteria of road damage as well as to increase driver's comfort for a broad range of road unevennesses.
Abstract: SUMMARY This paper deals with the novel control concept, so called ground-hook for active and mainly semi-active suspension of vehicles with the ultimate objective to minimize the tyre-road forces and thus the road damage. The basic ground-hook concept is extended to the several variants which enable to decrease criteria of road damage as well as to increase driver's comfort for a broad range of road unevennesses. Parameters of control law are determined by the parameter optimization for generally nonlinear model. The influence and interaction of the damping rate limits and time constants of variable shock absorbers are also taken into account. The influence of implementation of more complicated truck models is also discussed.
149 citations
TL;DR: In this paper, an integrated control system of active rear wheel steering (4WS) and direct yaw moment control (DYC) is presented, which makes the vehicle follow the desired dynamic model by the state feedback of both yaw rate and side slip angle.
Abstract: SUMMARY An integrated control system of active rear wheel steering (4WS) and direct yaw moment control (DYC) is presented in this paper. Because of the tire nonlinearity that is mainly due to the saturation of cornering forces, vehicle handling performance is improved but limited to a certain extent only by steering control. Direct yaw moment control using braking and/or driving forces is effective not only in linear but also nonlinear ranges of tire friction circle. The proposed control system is a model matching controller which makes the vehicle follow the desired dynamic model by the state feedback of both yaw rate and side slip angle. Various computer simulations are carried out and show that vehicle handling performance is much improved by the integrated control system.
144 citations
TL;DR: In this article, an on-line friction estimation method is presented using a simple brush type tyre model, which is verified by outdoor experiments using a tyre test trailer and results from both simulations and outdoor experiments are presented.
Abstract: SUMMARY Continuously updated knowledge of the friction potential and the friction demand can help to improve manoeuvrability and thereby safety of vehicles under slippery road conditions. An on line friction estimation method is presented using a simple brush type tyre model. First the method is verified by outdoor experiments using a tyre test trailer. Then the setup of a low-cost measurement system in a vehicle is discussed and results from both simulations and outdoor experiments are presented. Neural networks have been used both for modelling and identification of friction potential and friction demand.
135 citations
TL;DR: In this article, a non exhaustive overview of shock absorber models is presented and two physical models are presented that are able to extract the internal valve parameters from data without hysteresis.
Abstract: SUMMARY A non exhaustive overview of shock absorber models is presented. The ability of the models to match experimental data is emphasized. Two physical models are presented that are able to extract the internal valve parameters from data without hysteresis. In order to implement a model that copes with hysteresis, most models require the numerical solution to a set of nonlinear differential equations. The use of an alternative restoring force method can get round the time consuming iterative simulation and identification routines. The alternative nonparametric method models the force as a function of velocity and acceleration. The theoretical relevance of the model is studied.
122 citations
TL;DR: In this paper, the authors reviewed the effectiveness and limit of 4WS and DYC for vehicle handling and active safety and pointed out that DYC is more effective in vehicle motion with larger side-slip and/or higher lateral acceleration.
Abstract: SUMMARY In this paper chassis controls for vehicle handling and active safety have been reviewed. In particular, we have observed the effectiveness and limit of 4WS and DYC. It is pointed out that DYC is more effective in vehicle motion with larger side-slip and/or higher lateral acceleration and taking the nonlinearity of tire and vehicle dynamics into consideration is essential for introducing the control law for the chassis controls and their integration/coordination. We wish to emphasize that there is a need to further propose control laws based on deeper observation and understanding on the tire and vehicle dynamics.
110 citations
TL;DR: In this article, a comprehensive survey of active railway suspensions is provided, covering both basic concepts and significant practical implications around the world, and a critical review of technological opportunities, both current and future, is included, and the final section takes a speculative look at long term trends.
Abstract: SUMMARY The paper provides a comprehensive survey of active railway suspensions, covering both basic concepts and significant practical implications around the world. A critical review of technological opportunities, both current and future, is included, and the final section takes a speculative look at long term trends.
110 citations
TL;DR: In this article, a preliminary investigation into the integration of particular subsystems of an automobile's chassis is presented to determine the effect of modeling accuracy on the potential performance improvement of an anti-lock braking system.
Abstract: SUMMARY This work presents a preliminary investigation into the integration of particular 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. Several models, of varying degrees of complexity, are presented to determine the effect of modeling accuracy on the potential performance improvement. In the most detailed model, a four 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. The tire-road interface is modeled using the Magic Formula tire model. 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, for each...
99 citations
TL;DR: In this paper, the authors give an overview of the landing gear requirements and illustrate landing gear operational conditions, i.e., the shimmy problem, the dynamics at touch down and at ground roll.
Abstract: SUMMARY The landing gear is an inevitable system for the aircraft. It absorbs the energy of the landing impact and carries the aircraft weight at all ground operations, including take off, taxiing, and towing. Numerical simulation has become an invaluable tool for the assessment of landing gear dynamics as well as of aircraft/landing gear interaction. This paper gives an overview of the landing gear requirements and illustrates landing gear operational conditions, i.e., the shimmy problem, the dynamics at touch down and at ground roll. Furthermore, three software packages used in the simulation of aircraft ground dynamics are presented. A look at flight simulators and landing gear test facilities follows. Finally, the possible application of controlled landing gears is discussed.
TL;DR: In this article, a vehicle control scheme is presented which combines the Lotus modal decomposition with Karnopp's skyhook damper, allowing nearly optimal ride and simultaneously permitting modification of vehicle handling properties.
Abstract: SUMMARY In practice most active vehicle suspension work can be traced to two sources, Lotus' modal control and Karnopp's skyhook damper. A model is developed which allows comparison of different active suspension control algorithms. The Lotus modal control algorithm is reviewed, and compared with Karnopp's skyhook damper. It is shown that a tight inner closed loop allows the Lotus algorithm to achieve the inertial damping described by Kamopp for a single comer or quarter car. It is suggested that to achieve simultaneously high inertial damping and good disturbance rejection an inner force loop is desirable. A vehicle control scheme is presented which combines the Lotus modal decomposition with Karnopp's skyhook damper, allowing nearly optimal ride and simultaneously permitting modification of vehicle handling properties.
TL;DR: In this paper, an analysis of contact problem of free-rolling of pneumatic tires on a flat road is presented, where the tire is modeled as an elastic ring supported on a viscoelastic foundation and additional elastic spring elements on the outer surface of the ring are included to model the compliance of the tread rubber.
Abstract: The paper describes an analysis of contact problem of free-rolling of pneumatic tires on a flat road. The tire is modelled as an elastic ring supported on a viscoelastic foundation. Additional elastic spring elements on the outer surface of the ring are included to model the compliance of the tread rubber. The contact problem of a free-rolling tire is formulated for prescribed normal deflection and subjected to constraints of both normal contact and friction. The equations of motion for the treadband displacements are expressed in terms of modal expansion and non-linear boundary conditions of rolling contact are solved numerically to determine the region of contact, the distribution of normal and shear tractions and the effective rolling radius of the free-rolling tire. The contributions of tire hysteresis and frictional sliding in the contact region to the rolling resistance are determined. The influence of damping and Coriolis acceleration at higher rolling speeds on the asymmetric distribution...
TL;DR: In this article, an in-plane tyre model to study the tyre responses to brake torque variations is presented, which is based on the relaxation length principle and can handle zero velocity conditions.
Abstract: An in-plane tyre model to study the tyre responses to brake torque variations is presented. This model conceives a rigid ring (representing the tyre tread band) on an elastic foundation (representing the tyre sidewalls). The contact of the ring with the road is governed by a vertical residual stiffness representing the large deformation of the tyre in the contact patch and a slip model that generates the horizontal forces in the contact patch. This slip model, which is based on the relaxation length principle, is formulated such that it can handle zero velocity conditions. Experiments were carried out on a test drum. The tyre was excited by applying variations of brake torque. The measured frequency response functions of the longitudinal force show clearly two modes of vibration of the tyre at 33 and 77 Hz. The frequency response functions are used to estimate the tyre parameters. Large variations of brake torque are used to validate the tyre model. Two responses are discussed: successive step in...
TL;DR: In this paper, the use of controlled traction rods to give active yaw relaxation of coned wheelsets is investigated, and is shown to give significant improvements in curving performance without compromising stability, even on curves for which there is flange contact.
Abstract: SUMMARY The use of controlled traction rods to give active yaw relaxation of coned wheelsets is investigated, and is shown to give significant improvements in curving performance without compromising stability, even on curves for which there is flange contact. An assessment of practical implications such as power, actuator and control requirements is included.
TL;DR: In this paper, the authors investigated the use of several different inputs for the control of a vehicle, in the context of URD, and provided an intervention in the event of the vehicle leaving the road.
Abstract: SUMMARY This paper investigates the use of several different inputs for the control of a vehicle, in the context of URD. In this investigation, the goal of the URD controller is to provide an intervention in the event of the vehicle leaving the road. The types of inputs that will be considered are (i) Four Wheel Steering, (ii) Front Wheel Steering, (iii) Four Wheel Brake Steering, (iv) Front Wheel Brake Steering, and (v) Rear Wheel Brake Steering. The controller design is an LQ controller based on the simplified dynamics of a 2 degree of freedom bicycle model. However, the analysis of the different strategies are performed on a 7 degree-of-freedom nonlinear vehicle model. The key contribution of this paper is the quantitative evaluation of the relative efficiencies of each of these input strategies being examined. Unlike most control schemes, the performance measure to be used will not be the output tracking error of the system. Instead, the metric of performance is the ratio of peak tire force used versu...
TL;DR: In this paper, a computer model of an automotive monotube damper is developed based on fundamental principles of mechanics, which can identify the required damper valve and/or size for the desired performance and hence speed the design process.
Abstract: SUMMARY A computer model of an automotive monotube damper is developed based on fundamental principles of mechanics. The model can identify the required damper valve and/or size for the desired performance and hence speed the design process. Also, a parametric study can be easily conducted to understand the effects of parameters on the performance. A typical monotube damper is introduced and numerical formulations are described. Satisfactory agreement is achieved between model results and test data for a wide range of parameters including stroke conditions, valve combinations, and gas charge pressure. Some of these results are presented including the correlation at low and high speed strokes, cavitation simulation, and thermal effects on the performance.
TL;DR: In this paper, the authors present a vehicle model that includes the vehicle dynamics and a vehicle tire model and test the developed model on a step lane change maneuver and propose a model-reference based controller for remote control of a vehicle.
Abstract: SUMMARY We present a vehicle model that includes the vehicle dynamics and a vehicle tire model. The model developed is then used for conducting steering analysis of an automated vehicle. We test the developed model on a step lane change maneuver and propose a model-reference based controller for remote control of a vehicle. Stability analysis of the closed-loop system using die Lyapunov approach is included.
TL;DR: In this article, the same steady state tilt can be achieved with either system, but the transient behavior of the systems is studied separately and it is shown that even though the same stability can be obtained with both systems, the transient behaviour of the system is different.
Abstract: SUMMARY Small, narrow commuter vehicles have attracted considerable interest in recent years as a means to increase the utilization of existing freeways and parking facilities. However, conventional narrow track vehicles are likely to have reduced stability against overturning during hard cornering. A possible solution to this problem lies in vehicles which tilt toward the inside of a turn. Two different ways to achieve this tilt will be analyzed. For direct tilt control (DTC) an actuator forces the upper part of the vehicle to tilt. Steering tilt control (STC) uses steering to control the tilt as is done by motorcycle or bicycle riders. At low speeds, only the DTC system is effective while at high speeds the STC offers less lateral acceleration for the passenger during transient cornering and may seem more natural. The two methods of control will be studied separately and it will be shown that even though the same steady state tilt can be achieved with either system, the transient behavior of the systems...
TL;DR: In this paper, the authors developed a model to understand the transient force and moment characteristics of tyres involving large wheel slip and camber, and developed the tyre model which is capable of describing those characteristics.
Abstract: The objective of this study is to understand the transient force and moment characteristics of tyres involving large wheel slip and camber, and to develop the tyre model which is capable of describing those characteristics. Various kinds of experiments are performed including large slip angles, camber, and also combined cases of side slip and camber. Some particular characteristics are found such as non-lagging part in side force response and an apparent peak in aligning torque response to a stepwise camber change. It is confirmed that the stretched string tyre model is able to reflect major fundamental characteristics of tyres with sufficient accuracy under conditions of relatively small slip quantities. Some aspects on the analogy of turn slip to camber are also discussed. The tyre model combines a dynamic part based on the physical aspect using the relaxation length concept of stretched string theory, and a steady state part which is often described empirically such as the Magic Formula. In co...
TL;DR: In this paper, a sliding mode controller was developed for a wheel slip ratio control system for commercial vehicles with sluggish braking actuators to replace conventional if-then rule-like ABS control laws.
Abstract: SUMMARY A sliding mode controller has been developed for a wheel slip ratio control system for commercial vehicles with sluggish braking actuators to replace conventional if-then rule-like ABS control laws. New techniques overcome the tendency of sliding mode controllers to chatter. Computer simulation (hardware-in-the-loop simulation) and actual vehicle tests verified the effectiveness of this method to suppress chattering and keep the wheel slip ratio in a desirable range during braking on low-friction road surfaces.
TL;DR: In this paper, the authors investigated the use of several different inputs for the control of a vehicle, in the context of Obstacle Avoidance for autonomous vehicles, where the goal of the controller is to provide an intervention in the event of the vehicle detecting an obstacle in its path.
Abstract: SUMMARY In Alleyne (1996) several vehicle control options were considered for Unintended Roadway Departure (URD) prevention and conclusions were drawn as to the efficacy of each method. This companion paper investigates the use of several different inputs for the control of a vehicle, in the context of Obstacle Avoidance for autonomous vehicles. In this investigation, the goal of the controller is to provide an intervention in the event of the vehicle detecting an obstacle in its path. The five types of inputs that will be considered are (i) Four Wheel Steering; (ii) Front Wheel Steering; (iii) Four Wheel Brake Steering; (iv) Front Wheel Brake Steering; and (v) Rear Wheel Brake Steering. The controller design is an LQ controller based on the simplified dynamics of a 2 degree of freedom bicycle model. However, the analysis of the different strategies are performed on a more complete, nonlinear vehicle model. A key contribution of this paper is the quantitative evaluation of the relative efficiencies of eac...
TL;DR: In this paper, an enhanced tyre model is presented which could be useful both for vehicle dynamics analysis and for tyre design, and the physical phenomena involved in tyre-ground force generation are described mathematically in a semi-analytical form.
Abstract: On the basis of previous research papers, an enhanced tyre model is presented which could be useful both for vehicle dynamics analysis and for tyre design. The physical phenomena involved in tyre-ground force generation are described mathematically in a semi-analytical form. Given the main mechanical parameters of the tyre, the friction coefficients and the running conditions, the model returns the values of the forces generated at the tyre-ground interface either at steady- or at transient-state condition. Comparisons between experimental and computed data have been performed with satisfactory results.
TL;DR: In this paper, the authors provide a brief review of the state-of-the-art of tracked vehicle dynamics, including mobility over soft terrain, ride dynamics over rough surfaces and manoeuvrability.
Abstract: SUMMARY This paper provides a brief review of the state-of-the-art of tracked vehicle dynamics, including mobility over soft terrain, ride dynamics over rough surfaces and manoeuvrability. It is fo...
TL;DR: In this paper, a linear full-car model is used for the design of active suspension of a vehicle, where the dampers of the passive system are totally replaced by actuators.
Abstract: SUMMARY In order to present a useful method for designing active suspension of a vehicle, a linear full-car model is used in this investigation. In this model, the dampers of passive system are totally replaced by actuators. The actuators are controlled with optimal full state vector feedback. After determining feedback coefficients, the responses of active and passive systems were compared and it was found that performance of active system is much superior. It is desired that, changes in vehicle parameters would not affect the system's performance and hence should not violate its optimality. In other words, the system should behave adaptively using Model Reference Adaptive Control. The optimally controlled active suspension was used as a model for the active suspension of vehicle. In this way, the suspension of vehicle is controlled in such a way that its output approaches to that of the optimal active model. Thus the suspension should behave just like the optimal one.
TL;DR: In this paper, the authors presented an analytical approach for estimating the friction coefficient between a tire and the road, based on a brush type tire model with unlimited carcass stiffness, and validation experiments were conducted on wet and dry surfaces on an indoor drum type tire testing machine.
Abstract: This paper presents an analytical approach for estimating the friction coefficient between a tire and the road. We analyzed the friction coefficient in real time, based on a brush type tire model with unlimited carcass stiffness. The validation experiments were conducted on wet and dry surfaces on an indoor drum type tire testing machine. The calculated friction coefficients agreed well with the measured values.
TL;DR: In this article, an analytical transfer function based on a simple linear tyre model was used to estimate the relaxation length from pendulum experiments, which was compared to that determined from frequency response functions and from step responses of a non-linear tyre model.
Abstract: With an analytical transfer function based on a simple linear tyre model, the relaxation length can be estimated from pendulum experiments. This relaxation length is compared to that determined from frequency response functions and from step responses of a non-linear tyre model.
TL;DR: In this paper, several alternatives in modeling contact and friction within tyre models are discussed, focusing on existing models for the calculation of ride comfort, and the different approaches concerning contact, friction and friction have been used in serveral combinations.
Abstract: In this paper, several alternatives in modeling contact and friction within tyre models are discussed. Focusing on existing models for the calculation of ride comfort, the different approaches concerning contact and friction have been used in serveral combinations. These models do not differ very much in results, but in computational effort, which can be influenced by choice of modeling methods. As an example, a tyre model for computation of ride comfort is introduced, in which the model's dynamic characteristics (modes to be modeled) and geometric characteristics (wavelength of road disturbance) are decoupled.
TL;DR: In this article, the authors presented an extension of PELOPS about some specific models for the analysis of Adaptive Cruise Control (ACC) systems inside the PROMETHEUS program.
Abstract: SUMMARY In the last five years the IKA (Institut fur Kraftfahrwesen Aachen) and BMW created the microscopic traffic simulation program PELOPS. It simulates the traffic flow on motorways with a specific view on vehicle affairs. One application for PELOPS was the assessment of ACC (Adaptive Cruise Control) systems inside the PROMETHEUS program. It was shown, that PELOPS is a powerful tool for the analysis of new technologies. A new research period will extend the use of ACC about the functionality in urban areas. This requires an extension of PELOPS about some specific models. With this extension it is possible, to analyse new traffic technologies for the individual vehicles or the infrastructure. In a first step, PELOPS is extended about functions for suburban areas. This effects mainly the modelling of the driver behaviour. The driver behaviour is related to the traffic situation. In contrast to the normal traffic flow on motorways, the driver has to stop and go in the suburban area, he has to control low...