Showing papers in "Vehicle System Dynamics in 1996"
TL;DR: In this article, a new dynamic model of vehicle/track interaction is presented, which considers the vehicle and the track as a whole system and couples the vertical interaction with the lateral interaction.
Abstract: SUMMARY A new dynamic model of vehicle/track interaction is presented. The model considers the vehicle and the track as a whole system and couples the vertical interaction with the lateral interaction. The vehicle subsystem is modeled as a multi-body system with 37 degrees of freedom, which runs on the track with a constant velocity. The track substructure is modeled as a discretely supported system of elastic beams representing the rails, sleepers and ballasts. The normal contact forces between wheels and rails are described by Hertzian nonlinear elastic contact theory and the tangential wheel/ rail forces are decided by the creep theory. Numerical results are compared with those of conventional dynamic models of railway vehicles. Applications of the coupling model to the investigation of safety limits against derailment due to the track twist and the combined alignment and cross-level irregularities are reported at the end of the paper.
135 citations
TL;DR: In this paper, the steering control for passenger cars on automated highways is analyzed, concentrating on look-down reference systems, and the limitations of pure output-feedback of lateral vehicle displacement from the road reference are examined under practical constraints and performance requirements like robustness, maximum lateral error and comfort.
Abstract: SUMMARY In this paper, steering control for passenger cars on automated highways is analyzed, concentrating on look-down reference systems. Extension of earlier experimental results for low speed to highway speed is shown to be non-trivial. The limitations of pure output-feedback of lateral vehicle displacement from the road reference are examined under practical constraints and performance requirements like robustness, maximum lateral error and comfort. The in-depth system analysis directly leads to a new alternative design direction which allows to preserve look-ahead reference systems for highway speed automatic driving.
125 citations
TL;DR: In this article, an energy regenerative damper system which converts vibration energy into useful energy is proposed to achieve good performance of vibration reduction with few energy consumption in active and passive suspension systems.
Abstract: SUMMARY This paper proposes new control concept of suspension, i.e. a hybrid control system with active control and energy regeneration. In ordinary passive suspension system, damper converts vibration energy into heat energy by its viscosity, so that the vibration energy is dissipated. This dissipated energy is not used practically at all. On the other hand, active suspension system has great performance of vibration isolation but it consumes extra energy. This paper presents a method to solve these problems in active imd passive control systems as follows: In passive suspension an energy regenerative damper system which converts vibration energy into useful energy is proposed. The hybrid system combines this energy regenerative system and active control in order to achieve good performance of vibration reduction with few energy consumption. By numerical simulations and basic experiments it was found that the proposed hybrid control system had satisfactory performance in both vibration reduction and ener...
116 citations
TL;DR: In this article, a lane departure warning system is proposed to project vehicle trajectory, and compare with the perceived road geometry to calculate a performance metric termed "time to lane crossing" (TLC), when the calculated TLC is less than a threshold value.
Abstract: This paper is part of an on-going research toward the development of a lane-departure warning system. The basic concept of the lane- departure warning system is to project vehicle trajectory, and compare with the perceived road geometry 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. An on-line estimation of road/tire characteristics is crucial for the TLC calculation and the overall lane-departure warning system. 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.
100 citations
TL;DR: In this article, two situations of the tyre rolling over unevennesses are analysed using experiments and simulations: quasi-static rolling at very low velocity and dynamic rolling at high velocity. But the results of these experiments were not used to simulate the dynamic behaviour of the tire rolling over the unevennesses, also at higher velocity.
Abstract: SUMMARY The excitation of the tyre by short wavelength road unevennesses (e.g. cleats) is very complex. The tyre, which acts as a geometric filter due to its finite dimensions, smoothens the sharp edges of the unevenness. In this paper two situations of the tyre rolling over unevennesses are analysed using experiments and simulations: quasi-static rolling at very low velocity and dynamic rolling at high velocity. For the quasi-static rolling simulations an elaborate tyre model is used: the flexible ring model. This model is able to describe the deformation of the tyre tread-band. The responses of the tyre measured and simulated at quasi-static conditions are transferred into effective inputs. These effective inputs are used in a more simple tyre model: the rigid ring model. This model is used to simulate the dynamic behaviour of the tyre rolling over the unevennesses, also at higher velocity
79 citations
TL;DR: In this paper, the application of optimal control theory to time-optimal inverse simulation of car handling is investigated, which involves the calculation of driver actions required to perform specified manoeuvres, in as short a time as possible.
Abstract: SUMMARY The application of Optimal Control Theory to time-optimal inverse simulation of car handling was investigated. Time-optimal inverse simulation of car handling involves the calculation of driver actions required to perform specified manoeuvres, in as short a time as possible. Driver actions consist of time-histories of front wheel steer rate and longitudinal force. Optimal time-histories of these quantities were calculated using the Gradient method after formulating the problem as one of optimal control. Simulation results are presented for two different cars performing similar lane-changes. These results show significant differences in necessary driver actions for different cars and demonstrate the suitability of the approach taken.
75 citations
TL;DR: A vehicle system dynamics model is presented that captures the essential braking and handling behavior of an automobile with independent suspensions on a flat surface and is described in sufficient detail for an engineer to reproduce it with a multibody simulation program.
Abstract: SUMMARY A vehicle system dynamics model is presented that captures the essential braking and handling behavior of an automobile with independent suspensions on a flat surface The model, which has 18 degrees of freedom, is described in sufficient detail for an engineer to reproduce it with a multibody simulation program Further, a stand-alone computer program based on the model has been put on the internet for interested readers to download and run The model has a simple generic representation of suspension kinematics that can represent the behavior of most independent suspensions The generic model is demonstrated using a previously published vehicle description (the IAVSD Iltis multibody benchmark) and compared with a detailed multibody model Close agreement was found between the two models both for eigenvalues and for nonlinear time history responses
73 citations
TL;DR: This paper demonstrates the use of elementary neural networks for modelling and representing driver steering behaviour in path regulation control tasks and uses by vehicle simulation experts and human factors specialists.
Abstract: SUMMARY This paper demonstrates the use of elementary neural networks for modelling and representing driver steering behaviour in path regulation control tasks. Areas of application include uses by vehicle simulation experts who need to model and represent specific instances of driver steeringcontrol behaviour, potential on-board vehicle technologies aimed at representing and tracking driver steering control behaviour over time, and use by human factors specialists interested in representing or classifying specific families of driver steering behaviour. Example applications are shown for data obtained from a driver/vehicle numerical simulation, a basic driving simulator, and an experimental on-road test vehicle equipped with a camera and sensor processing system.
67 citations
TL;DR: In this article, the authors address the problem of automation of heavy-duty vehicles and develop nonlinear controllers with adaptation, first for speed control and then for vehicle follower longitudinal control.
Abstract: SUMMARY In this paper we address the problem of automation of heavy-duty vehicles. After a brief description of the dynamic model used in our design and simulations, we develop nonlinear controllers with adaptation, first for speed control and then for vehicle follower longitudinal control. We consider both autonomous operation as well as intervehicle communication, and evaluate the stability and performance properties of our controllers in several different scenarios through analysis and simulation.
66 citations
TL;DR: In this paper, the design of a modem active tilting suspension and control law for a small narrow, one-half width, commuter vehicle is presented, and the static and dynamic tipping limits illustrate which vehicles are considered tall and narrow.
Abstract: SUMMARY There are many problems that face transportation systems as the twenty-first century approaches, and many solutions will be required. Mass transportation systems are one large area of research that will provide some solutions. This paper presents another possible solution at the other end of the spectrum, small relatively tall and narrow tilting commuter vehicles for individual transportation. A historical overview of the various types of tilting vehicles built or proposed over the last forty years is shown and the results of these studies are discussed. If one considers a relatively tall and narrow vehicle, (under 1.0 meters or 40“ wide), to maintain high speed performance in cornering it becomes necessary to bank the vehicle into a corner to prevent overturning. The design of a modem active tilting suspension and control law for a small narrow, one-half width, commuter vehicles is presented. Analysis of the static and dynamic tipping limits illustrates which vehicles are considered tall and narr...
62 citations
TL;DR: In this paper, the authors describe an investigation into active roll control of articulated vehicles, where the objective is to minimise lateral load transfer using anti-roll bars incorporating low bandwidth hydraulic actuators.
Abstract: SUMMARY This paper describes an investigation into active roll control of articulated vehicles. The objective is to minimise lateral load transfer using anti-roll bars incorporating low bandwidth hydraulic actuators. Results from handling tests performed on an articulated vehicle are used to validate a nonlinear yaw/roll model of the vehicle. The methodology used to design lateral acceleration controllers for vehicles equipped with active anti-roll bars is developed using a simplified linear articulated vehicle model. The hardware limitations and power consumption requirements of the active elements are studied. The controller is then implemented in the validated articulated vehicle model to evaluate the performance of an articulated lorry with active anti-roll bars. The simulation results demonstrate the possibility of a significant improvement in transient roll performance of the vehicle, using a relatively low power system (10 kW), with low bandwidth actuators (5 Hz).
TL;DR: In this paper, a mathematical model is used to analyse the influence of vehicle and track parameters on the dynamic behaviour of the vehicle-track system, focusing on the effect of spatially varying track stiffness.
Abstract: SUMMARY In this paper a mathematical model is used to analyse the influence of vehicle and track parameters on the dynamic behaviour of the vehicleltrack system. Particular attention is given to the influence of spatially varying track stiffness on the performance of the vehicle and the dynamic loading between the wheel and the track at low frequencies. Differential track settlement, due to the dynamic loading of the track and due to spatial stiffness variations in the track, is also predicted.
TL;DR: In this paper, the optimal tire force distribution to maximize acceleration/deceleration of a four-wheel vehicle during cornering is studied, and the optimization involves equality and inequality constraints and are solved by nonlinear programming techniques.
Abstract: SUMMARY The optimal tire force distribution to maximize acceleration/deceleration of a four-wheel vehicle during cornering is studied. The objective of this research is to investigate the improvement one can expect from the implementation of different vehicle steering and driving mechanisms. We first identify the upper limit imposed by physical laws by assuming all the four wheels can be individually steered and driven. Practical vehicle configurations such as four-wheel-steering (4WS) and four-wheel-drive (4WD) are then considered. The optimization involves equality and inequality constraints and are solved by nonlinear programming techniques.
TL;DR: In this paper, the authors used the cormgation formatting model considering with the characteristic of creep between wheel and rail interface, and successfully fixed the formation mechanism of Cormgation.
Abstract: SUMMARY Many researches on the problem of cormgation formatting on the track of railway have been reported in the world. But most of those researches are carried out by phenomena analyzing which occurred on real track or by just using theoretical model and scaled model simulation. For the reason of technical difficulties, theoretical researches proved by practical experiment are very rare. By using the cormgation formatting model considering with the characteristic of creep between wheel and rail interface we successfully fixed the formation mechanism of cormgation. Theoretical analyzing results agree well with the phenomena measured on stand experiment and on commercial line.
TL;DR: In this paper, the authors compared eight contributions to a benchmark test which was written for programs developed to examine the high frequency dynamic interaction of railway vehicles and the track, and concluded that substantially identical results can be obtained from both types of model in the majority of conditions considered in the test.
Abstract: SUMMARY Results have been compared of eight contributions to a benchmark test which was written for programs developed to examine the high frequency dynamic interaction of railway vehicles and the track. Participants were requested to consider a vehicle passing over uniform, sinusoidal corrugation, and to calculate the vertical rail acceleration and various forces and bending moments in rail and sleeper. From the results for the wide variety of time and frequency domain models which were used it is concluded that substantially identical results can be obtained from both types of model in the majority of conditions considered in the test. There is a greater variation in results between the 5 frequency domain models used in these submissions than between the 2 high frequency time domain models.
TL;DR: A Direct Yaw Moment Control for Improving Limit Performance of Vehicle Handling - Comparison and Cooperation with 4WS- Vehicle System Dynamics: Vol. 25, No. sup1, pp. 3-23 as discussed by the authors.
Abstract: (1996). A Direct Yaw Moment Control for Improving Limit Performance of Vehicle Handling - Comparison and Cooperation with 4WS- Vehicle System Dynamics: Vol. 25, No. sup1, pp. 3-23.
TL;DR: In this article, the authors investigated the braking characteristics of a tractor-tank-semitrailer vehicle by incorporating the influence of liquid load shift occurring within the partially filled tank.
Abstract: SUMMARY Braking characteristics of a tractor-tank-semitrailer vehicle is investigated by incorporating the influence of liquid load shift occurring within the partially filled tank. The tank vehicle model is developed by integrating a steady state model of a partially filled tank and a pitch plane model of the vehicle. The liquid load shift occurring in the pitch plane of the vehicle during a braking maneuver is characterized using the change in the gradient of the free surface of liquid and the corresponding shift in the center of gravity of the fluid bulk. The change in normal load on the various axles of the vehicle during the maneuver is then computed to analyze the braking behavior of the partially filled tank vehicle. The braking characteristics of the tank vehicle are then compared to those of an equivalent rigid cargo vehicle in order to study the impact of liquid load shift. Influence of various vehicle and tank design parameters on the braking behavior and wheel lock-up condition is also investi...
TL;DR: In this article, the authors proposed an active front and rear wheel steering control system that simultaneously achieves both lateral acceleration and yaw rate responses always desirable regardless of changes in vehicle dynamics and external disturbances.
Abstract: SUMMARY This paper proposes an active front and rear wheel steering control system that simultaneously achieves both lateral acceleration and yaw rate responses always desirable regardless of changes in vehicle dynamics. First, this paper describes a method to accurately estimate physical parameters in the four wheel steering vehicle model, including the dynamics of a steering actuator, by applying the maximum likelihood estimation method. Next, the structure of the proposed front and rear steering control system is described. This control system has for its purpose to coincide both the lateral acceleration and yaw rate responses of the vehicle with the responses of the respective desirable reference models, as well as to make it a robust system against changes in vehicle dynamics and external disturbances. To achieve both objectives, a two-degree-of-freedom control system theory is employed. Then the paper shows the viability of the proposed steering control system through computer simulations. Finally, ...
TL;DR: In this paper, two fuzzy logic traction controllers are presented for longitudinal platoon systems and their performance degrades in the presence of time-varying uncertainties, and the controller is robust against changing road conditions and uncertainties.
Abstract: SUMMARY This paper presents two fuzzy logic traction controllers and investigates their effect on longitudinal platoon systems. A fuzzy logic approach is appealing for traction control because of the nonlinearity and time-varying uncertainty involved in traction control systems The fuzzy logic traction controllers we present regulate brake torque to control wheel slip, which is the normalized difference between wheel and vehicle speed. One fuzzy controller estimates the peak slip corresponding to the maximum tire-road adhesion coefficient and regulates wheel slip at the peak slip. The controller is attractive because of its ability to maximize acceleration and deceleration regardless of road condition. However, we find through simulations the controller's performance degrades in the presence of time-varying uncertainties. The other fuzzy logic controller regulates wheel slip at any desired value. Through simulations we find the controller robust against changing road conditions and uncertainties. The targ...
TL;DR: In this paper, the authors developed and verified a dynamic model of a seated cyclist riding an off-road bicycle up a smooth road, with the absence of terrain irregularities, all suspension motion was rider induced.
Abstract: SUMMARY The energy dissipated by the suspension systems used for off-road bicycles is a major concern due to the limited power source in cycling. Rider induced energy losses are those that arise from the muscular action of the rider. The purpose of this study was to develop and verify a dynamic model of a seated cyclist riding an off-road bicycle up a smooth road. With the absence of terrain irregularities, all suspension motion was rider induced. Knowing the stiffness and dissipative characteristics of the suspension elements, the power dissipated by the suspensions was calculated. Simulation results were compared to suspension deflections that were experimentally measured for a cyclist riding a commercially available dual suspension bicycle up a 6% grade at 6.5m/s. For this particular case, no fork motion was observed in the experiments which was consistent with the simulation results. For the rear suspension, the mean and amplitude of the largest harmonic were experimentally determined to be 6.6 and ±2...
TL;DR: In this article, the optimal control laws for different actuator bandwidths and various amounts of road preview are generated, and estimates of power consumption are made, and two possible layouts of a slow-active suspension model are analyzed.
Abstract: SUMMARY Two possible layouts of a slow-active suspension model are analysed. Optimal control laws for different actuator bandwidths and various amounts of road preview are generated, and estimates of power consumption are made. Higher bandwidth systems (10Hz) require less preview to obtain a given level of performance than those with a lower bandwidth (3Hz) but use more energy in doing so. Similar performance is available from the two systems considered, although the second uses considerably less energy to obtain that performance.
TL;DR: In this article, the authors present a merge maneuver in which the cars in the trail platoon are moving faster than those in the lead platoon, while the gap separating the two platoons is smaller than usual.
Abstract: SUMMARY The IVHS 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, the merge and the split. A third longitudinal maneuver, decelerate to change lane, allows a platoon switching from one lane to another to enter its new lane at a safe spacing and speed. The maneuvers, particularly the merge, can be potentially hazardous. In a merge, the cars in the trail platoon are moving faster than those in the lead platoon, while the gap separating the two platoons is smaller than usual. A sudden deceleration by the lead platoon could cause a high-speed collision. If the relative velocities of the merging platoons can be constrained so that they are guaranteed never to collide at a high relative velocity, the merge can be considered safe. A maximum safe velocity for the trail platoon can be found for any given spacing and lead-platoon velocity. This paper presents a merge maneuver in which the ...
TL;DR: In this article, an optimal preview control algorithm is applied to a two-degree of freedom (dof) vehicle model travelling with constant velocity on a randomly profiled road, where the road roughness is modelled as a homogeneous random process being the output of a linear first order filter to white noise.
Abstract: SUMMARY An optimal preview control algorithm is applied to a two degree of freedom(dof) vehicle model travelling with constant velocity on a randomly profiled road. The road roughness is modelled as a homogeneous random process being the output of a linear first order filter to white noise. The input from the road irregularity is assumed to be measured at some distance in front of the vehicle and this measured infonnation is utilized by the active controller to prepare the system for the ensuing input. The preview control algorithm is obtained by minimizing a quadratic performance index and by describing the average behaviour of the system by the covariance matrix of the vehicle response state vector. Results are presented for full state feedback and significant improvements in sprung mass acceleration, suspension working space and road holding are observed.
TL;DR: In this article, an adaptive linear quadratic Gaussian (LQG) controller is calculated at each time step of the identification phase as an estimate of the plant parameters from which the parameters of the LQG controller are updated.
Abstract: SUMMARY In this paper a new procedure is proposed to predict the vehicle behaviour when the vehicle is approaching to some critical point (roll-over, jackknifing). The on-board computer automatically identifies some of the vehicle's parameters, and runs the vehicle model getting the information from the sensors installed on the vehicle. When the vehicle approaching to some stability limit the safety system is activated. An adaptive linear quadratic Gaussian (LQG) controller is calculated at each time step of the identification phase as an estimate of the plant parameters from which the parameters of the LQG controller are updated. Meanwhile the parameters of the controller are modified in order to get an adaptive robust controller with the attractive properties of the linear quadratic (LQ) controller in such a way that loop transfer recovery (LTR) of the original state feedback is achieved.
TL;DR: In this article, an optimal control design method is introduced and then applied to the optimum design of active and passive suspension systems, where every suspension unit can have its own feedback measurements and the criterion function can be related to all state and control variables.
Abstract: SUMMARY An optimal control design method is introduced and then applied to the optimum design of active and passive suspension systems. A basic three-dimensional 7-DOF car riding model subjected to four correlated random road inputs is considered. The design method is basically developed to allow arbitrary choice of sensors for various car state variables to be used for feedback control of each suspension unit. Previous studies show that full-state control laws and even some limited-state control laws often include feedback gains which are almost zero. Some other gains, although not zero, don't play an important role in improving the system performance measures. With the method proposed in this work, every suspension unit can have its own feedback measurements and the criterion function can be related to all state and control variables. Thus a large number of active and semi-active suspension systems with full- or limited-state control laws based on different measurement combination can be suggested, stud...
TL;DR: In this paper, a numerical analysis of liquid load in elliptical road containers undergoing a steady-state turning manoeuvre is presented for containers of unrestricted size and for containers with fixed capacity.
Abstract: SUMMARY A numerical analysis of liquid load in elliptical road containers undergoing a steady-state turning manoeuvre is presented for containers of unrestricted size and for containers of fixed capacity. The liquid load is expressed in terms of the horizontal and vertical forces and the overturning moment created by these forces around the middle bottom point of the container. The moment is obtained by integrating the liquid free-surface equation and using numerical calculation of the resulting expressions. An optimization study with an objective to minimize the peak overturning moment is performed on containers of fixed capacity to identify the optimal height/width ratio of the container. The results of this investigation being of a general nature, i.e. with no restriction for an application, are particularly intended for road tankers under a steady turning manoeuvre, where they can be applied with high degree of accuracy.
TL;DR: In this paper, the overhead electrification system for high speed trains is modeled by a three degree of freedom pantograph and an infinite homogeneous and elastically supported beam, and the results show that transverse zig-zag effects are the primary expected motion in this system.
Abstract: SUMMARY The overhead electrification system for high speed trains is modeled by a three degree of freedom pantograph and an infinite homogeneous and elastically supported beam. Travelling wave solutions for the beam with a moving load are used to derive an equivalent stiffness for the pantograph model. The model is new in that it takes account of transverse motion due to catenary zig-zag effects. Finite element solutions are also obtained for the moving load problem. The results show that transverse zig-zag effects are the primary expected motion in this system. The calculations also show the expected importance of critical wave speeds in these systems.
TL;DR: In this paper, a driver assistance system is described which provides an automatic road-departure warning and intervention function, intended for drivers who are drifting off the roadway at a shallow angle of departure due to inattention, drowsiness, intoxication, or other causes.
Abstract: SUMMARY A driver assistance system is described which provides an automatic road-departure warning and intervention function. The system is intended for drivers who are drifting off the roadway at a shallow angle of departure due to inattention, drowsiness, intoxication, or other causes. An integrated set of model-based estimation algorithms serves to anticipate imminent road departures. Interventions are achieved using differential braking -- the application of unequal brake torques at the right and left wheels. The driver remains in the loop, always able to provide the primary steering commands. A driver state assessment module is being developed to further adapt to individual driven and to identify changes in driver behavior. We describe the algorithms, present simulation results, and include preliminary experimental data from a prototype vehicle.
TL;DR: In this paper, a method is developed for minimization of steered wheel shimmy and its wear also during the straight-line drive of heavy vehicles, which can also be used in the phase of designing the heavy vehicles.
Abstract: SUMMARY In choosing the steering system parameters the tendency is towards the minimization of kinematic errors that appear during turning. For that developed procedures exist that take into account also the influence of kinematic of the suspension system on kinematic parameters of vehicle turning. Besides that, maintenance tests have shown, that increased deflections of the suspension system lead to increased wear of tires of steered wheels. In this paper, a method is developed for minimization of steered wheel shimmy and its wear also during the straight-line drive of heavy vehicles. The procedure can also be used in the phase of designing the heavy vehicles.
TL;DR: In this article, the authors present the results of dynamic analyses conducted to investigate the performance of a rail vehicle system consisting of a passenger car, an inertial measurement unit for measuring accelerations related to the dynamic movement of the vehicle and for measuring the tilting angle of the car body, a digital control unit, and actuators to reduce the accelerations felt by the passengers.
Abstract: SUMMARY This paper presents the results of dynamic analyses conducted to investigate the performance of a rail vehicle system consisting of a passenger car, an inertial measurement unit for measuring accelerations related to the dynamic movement of the vehicle and for measuring the tilting angle of the car body, a digital control unit, and actuators to reduce the accelerations felt by the passengers. The control strategies are described. The method of multibody systems has been used to design the control systems. The nonlinear dynamics of a virtual vehicle system has been analyzed on the computer synchronously to the hardware realization of the vehicle system. The paper focuses on how advanced software tools can be applied by the rail vehicle engineer for designing advnnced rail vehicle suspensions and performing vehicle system dynamic analyses.