Vehicle System

Heavy vehicles exiting (or entering) a tunnel at high speed under a strong crosswind is a particularly critical condition since the aerodynamic load changes drastically, greatly affecting the lateral stability of the vehicle. Often, active control systems (active suspensions, active front steering, etc.) and infrastructure elements (e.g., wind fences) are proposed to reduce the induced risks. To help the design of these devices, the present paper investigates the response of the vehicle–driver system in the case of a high-sided lorry exiting a tunnel under crosswind, by using Driver-In-the-Loop simulations. The study was performed using the dynamic driving simulator of Politecnico di Milano and 28 test drivers. Vehicle and aerodynamic models have been developed to reproduce the phenomenon in a highly immersive environment. During the tests, several combinations of vehicle and wind speed were considered. The effect of vehicle loading condition (Empty and Laden) was also investigated....

This paper investigates the feasibility of a semiactive suspension of the cabin of a fork lift truck as a way of reducing the effect of harmful vibrations on the health of truck drivers. A suspension based on MR fluid dampers has been designed and implemented on an actual vehicle and heuristic control strategy has been developed, which preserves the filtering properties of the passive suspension when the vehicle moves in a straight line with a constant velocity and suppresses the large amplitude pitch and roll motion during turns and braking. Field tests have demonstrated a substantial comfort improvement with respect to the passive suspension, during the braking and turning phases, without any noticeable detrimental effects.

A methodology for validating computer simulations of physical systems is applied to vehicle stability and control simulations. Validation is defined, within some specified operating range of the system, as a simulation's predictability of system responses' being able to agree with actual measured system responses within some specified level of accuracy. The method uses repeated experimental runs at each test condition to generate sufficient data for statistical analyses. Acquisition and reduction of experimental data and the processing path for simulation data are described. Usefulness of time-domain validation for steady state and slowly varying transients is discussed. Importance of frequency domain validation for thoroughly validating a simulation is shown. Both qualitative and quantitative methods for comparison of simulation predictions with actual test measurements are developed. In order to illustrate the validation methodology, experimental testing of four different vehicles was performed. Comparisons between actual test measurements and simulation predictions are shown. During the past 30 years, substantial effort has gone into development of numerous vehicle stability and control computer simulations. Unfortunately, much less effort has gone into answering the important question of the validity of these simulations. Because experimental testing of full-scale vehicles for validation procedures is quite expensive and time consuming, many vehicle dynamics simulations have had little or no validation work performed. Many modified and new simulations have been compared with predictions from existing simulations as the sole check of their validity. Others have been experimentally substantiated only for limited vehicle operating conditions and then assumed to be valid for all other operating conditions. NHTSA desires a vehicle stability and control simulation that can simulate a wide range of light vehicles (passenger cars, pickup trucks, vans, and utility vehicles) in a broad range of cornering and braking maneuvers. NHTSA is studying existing simulations, selecting the most appropriate one for its purposes, and improving it to resolve problems identified during the selection process. Simulation validation methodology and procedure described were developed as part of this work. For a particular application, the validation methodology described can distinguish the most appropriate simulation out of a group of simulations. In addition, it has proven itself to be useful for identifying measurement errors in simulation

This paper investigates the application of Model Predictive Control (MPC) technology based on mixed H 2 /H∞ control approach for active suspension control of a railway vehicle, the aim being to improve the ride quality of the railway vehicle. Comparisons are made with more conventional control approaches, and the applicability of the linear matrix inequality approach is illustrated via the railway vehicle example.

This paper describes the development of a hybrid approach to estimate the states and parameters of a vehicle. The parameter estimator is based on a genetic algorithm in conjunction with a bank of extended Kalman filters, which are simultaneously utilised to estimate the states of the system. This paper shows results of the approach when applied to a four-wheel-vehicle model and the advantages and limitations are discussed.

In vehicle development, rating vehicle reactions to external disturbances such as aerodynamic excitations are important for improving safety and comfort of passengers. Vehicle motion reactions under such conditions are dependent on both disturbance and drivers' steering actions. A predictive model has been developed to correctly anticipate the drivers' ability to identify unexpected external disturbances for straight-line, high-speed driving in a driving simulator. The measured variables were band-pass filtered to desired frequency ranges. Excess yaw and roll velocities, defined as the difference between actual rotations and rotations predicted with a dynamic model from the cause of actual steering, were calculated. The standard deviations of the measured variables in a time window around disturbances were used in a regression model to predict the driver responses. Replacing actual rotations with excess rotations reduced the importance of steering input as a predictor by approximately 2/3, thus improving the accuracy of the predictive model. The model showed the change in driver sensitivity to rotations at different frequency intervals. It also showed that only driver input in around 1 ~ 2 Hz reduces driver sensitivity and that drivers are not necessarily sensitive to high rotational accelerations, but rather to large differences between actual vehicle yaw and roll and expected vehicle yaw and roll responses from the steering input The result from this study were later compared to succeeding on-road tests which confirmed that the predictive model was improved with the use of excess motion variables.

The automotive trends of vehicles with lower aerodynamic drag and more powerful drivetrains have caused increasing concern regarding stability issues at high speeds, since more streamlined bodies show greater sensitivity to crosswinds. This is especially pronounced for high vehicles, such as sports utility vehicles. Besides, the competitiveness in the automotive industry requires faster development times and, thus, a need to evaluate the high speed stability performance in an early design phase, preferable using simulation tools. The usefulness of these simulation tools partly relies on realistic boundary conditions for the wind and quantitative measures for assessing stability without the subjective evaluation of experienced drivers. This study employs an on-road experimental measurements setup to define relevant wind conditions and to find an objective methodology to evaluate high speed stability. The paper focuses on the events in proximity to the drivers' subjective triggers of instability. Wind direction and magnitude, vehicle motion response, along with the subjective event triggering were measured at different conditions of the natural wind. A statistical approach was utilized to analyze the correlation between the vehicle response and subjective triggers together with the wind conditions. A correlation was established between the subjective triggers and a rapid change in lateral acceleration and yaw velocity response. The paper also proposes a set of four crosswind gust profiles of interest for driving stability, combining results from previous research and the experimental data of the natural wind obtained in this study. These findings can be used as objective measures for virtually assessing stability performance and as realistic boundary conditions for simulating wind gusts.

Bu çalışmada, sistemin lineer olmayan yapısına bağlı olarak tasarlanan geri adımlamalı kontrol yöntemi ile dört rotorlu bir İnsansız Hava Aracı (İHA) olan Quadrotor'un gerçek zamanlı yörünge takibi gerçekleştirilmiştir. Deneysel çalışmada kullanılan Quadrotor, donanımsal olarak (GPS, sonar, kamera, atalet sensörleri vb.) oldukça düşük maliyetlidir. Tasarlanan geri adımlamalı kontrolcü, donanımsal açıdan zayıf bir sistem üzerinde yüksek verimle çalışmış ve gelecekte tasarlanacak donanımsal açıdan yüksek hassasiyette ölçüm yapabilen sistemler için iyi bir kontrolcü referansı olmuştur. Quadrotor'un kapalı ortamda eğik çember ve zigzag formunda iki ayrı yörüngeyi takibi ile elde edilen sonuçlar incelendiğinde, kontrolcünün meydana gelen hataları istenilen düzeyde elimine ettiği ve sistemdeki sapmaları minimumda tuttuğu görülmüştür.

Disturbances decrease vehicle stability and increase driver's mental and physical workload. Especially unexpected disturbances such as lateral winds have severe effect on vehicle stability and driver's workload. This study aims at building a driver model of steering operations in lateral wind toward developing effective driver assistance system. First, the relationship between the driver's lateral motion and its reactive quick steering behavior is investigated using driving simulator with lateral 1dof motion. In the experiments, four different wind patterns are displayed by the simulator. As the results, strong correlation was found between the driver's head lateral jerk by the lateral disturbance and the angular acceleration of the steering wheel. Then, we build a mathematical model of driver's steering model from lateral disturbance input to steering torque of the reactive quick feed-forward steering based on the experimental results. Finally, validity of the proposed model is shown by comparing the steering torque of experimental results and that of simulation results.

In this study, the adaptive control of a time-varying nonlineer system is achieved by using Fuzzy Model Reference Learning Control (FMRLC) method. The FMRLC method provides a systematic procedure for the design of fuzzy controllers. In the FMRLC method, a knowledge-base modification algorithm which reduces the computation time and memory requirements by utilizing a rule base array table instead of a fuzzy relation table. While some parameters of the membership functions are determined by trial and error method in the most classical fuzzy control systems, these parameters are determined by a learning mechanism in FMRLC method. In this study, the proposed FMRLC algorithm is used in the nonlineer control of the tanker ship steering. Simulation results demonstrating the effectiveness of the proposed control structure are given in this paper.

Bu çalışmada, Otomatik Yönlendirmeli Aracın (OYA) gövde hızı ve gövde açısı kontrolü gerçek zamanlı olarak bulanık mantık kontrolcü ile gerçekleştirilmiştir. OYA'nın gövde hızı ve gövde açısı denetimi ile aracın iki boyutlu düzlemde istenilen yörüngeyi takip etmesi sağlanmıştır. Ayrıca, bulanık mantık kontrolcünün performansı PI kontrolcü ile mukayese edilmiş ve deneysel sonuçlar bulanık mantık kontrolcünün PI kontrolcüye oranla daha kararlı ve daha uygun kontrol işaretleri ürettiğini ve dinamik değişimlere daha hızlı cevap verdiğini göstermiştir. Kontrolcü performansları ayrıca ani harici bozucu etki ve ekstra yük için incelenmiş ve başarılı sonuçlar elde edilmiştir. In this paper a fuzzy controller is applied to velocity and direction angle control of a certain type of wheeled mobile robots called Automated Guided Vehicles (AGVs). The velocity and direction angle of the AGV are controlled to keep the vehicle on desired path. A PI controller is also applied to AGV in order to show the robustness of the fuzzy controller. Experimental results prove that the fuzzy controller shows better tracking performance than the PI controller in terms of robustness, smoothness and fast dynamics. Results are also given for sudden disturbance and extra load conditions and satisfied results are obtained.

This paper presents a novel control strategy for real-time controlled restraint systems. Today's restraint systems typically include a number of airbags, and a three-point seat belt with load limiter and pretensioner. In the class of realtime controlled restraint systems, the restraint actuator settings are continuously manipulated during the crash. The control strategy developed here is based on reference management, in which a nonlinear device -a reference governor -is added to a primal closed loop controlled system. This governor determines an optimal setpoint in terms of injury reduction and constraint satisfaction by solving a constrained optimization problem. Prediction of the vehicle motion, required to predict future constraint violation, is included in the design and is based on linear regression of past crash data. Simulation results with a MADYMO model show that a significant injury reduction is possible, without prior knowledge of the crash. Furthermore, it is shown that the algorithms are sufficiently fast to be implemented on-line.

The automotive trends of vehicles with lower aerodynamic drag and more powerful drivetrains have caused increasing concern regarding stability issues at high speeds, since more streamlined bodies show greater sensitivity to crosswinds. This is especially pronounced for high vehicles, such as sports utility vehicles. Besides, the competitiveness in the automotive industry requires faster development times and, thus, a need to evaluate the high speed stability performance in an early design phase, preferable using simulation tools. The usefulness of these simulation tools partly relies on realistic boundary conditions for the wind and quantitative measures for assessing stability without the subjective evaluation of experienced drivers. This study employs an on-road experimental measurements setup to define relevant wind conditions and to find an objective methodology to evaluate high speed stability. The paper focuses on the events in proximity to the drivers' subjective triggers of instability. Wind direction and magnitude, vehicle motion response, along with the subjective event triggering were measured at different conditions of the natural wind. A statistical approach was utilized to analyze the correlation between the vehicle response and subjective triggers together with the wind conditions. A correlation was established between the subjective triggers and a rapid change in lateral acceleration and yaw velocity response. The paper also proposes a set of four crosswind gust profiles of interest for driving stability, combining results from previous research and the experimental data of the natural wind obtained in this study. These findings can be used as objective measures for virtually assessing stability performance and as realistic boundary conditions for simulating wind gusts.

The use of electromagnetic dampers (ED) in vehicle active suspension systems has drawn considerable attention in the past few years, attributed to the fact that active suspension systems have shown superior performance in improving ride comfort and road handling of terrain vehicles, ...

Results of vehicle crosswind research involving both full-scale driver-vehicle tests and associated analyses are presented. The paper focuses on experimental crosswind testing of several different vehicle configurations and a group of seven drivers. A test procedure, which utilized wind-generating fans arranged in alternating directions to provide a crosswind "gauntlet", is introduced and described. Driver preferences for certain basic chassis and aerodynamic properties are demonstrated and linked to elementary system responses measured during the crosswind gauntlet tests. Based on these experimental findings and confirming analytical results, a two-stage vehicle design process is then recommended for predicting and analyzing the crosswind sensitivity of a particular vehicle or new design.