Vehicle Stability

Autor: Dean Karnopp
Publisher: CRC Press
ISBN: 9780203913567
File Size: 78,40 MB
Format: PDF
Read: 8093
Download or Read Book
This reference offers a systematic approach to the dynamics and stability of vehicles such as cars, bicycles, trailers, motorcycles, and trains and shows how mathematical models of varying degrees of complexity can be used to suggest design guidelines for assurance of vehicle stability. Based on more than 30 years of teaching experience from a renowned authority in mechanical systems modeling, this volume illustrates the derivations of equations of motion using Newton's laws, Lagrange's equations, and bond graphs through a series of examples dispersed throughout the text and describes the similarities and differences in the stability properties of various vehicle types.

Vehicle Stability

Autor: Abigail Kolagani
Publisher:
ISBN:
File Size: 49,48 MB
Format: PDF, ePub
Read: 9493
Download or Read Book
Abstract: Over the years vehicle models had been developed based on vehicle dynamics only. There was a never a model developed taking human response into consideration although the human plays a vital role in determining the stability of the vehicle. The current research was developed to close the loop between the human response and the vehicle response. The underlying assumption of this research is that the time required to attenuate the dynamic response of the steering system, compared to the time response frequency of the driver, may have a significant impact on the driver's perception of the handling character (understeer vs. oversteer) of the vehicle. Therefore, the objective of this research is to utilize a simple 2-wheeled "bicycle" dynamic steering system model to evaluate steering system performance when perturbed by inputs at typical driver frequencies and amplitudes. This promoted the current research to develop a vehicle model which included a function for human responses. The developed model takes driver responses into consideration, and predicts the dynamic stability of the vehicle. The model was developed using the theory of a simple bicycle vehicle system, when disturbed by typical driver inputs and the simulated results were compared with real world data to illustrate that the model is able to predict the behavior of the vehicle in the case of a step steer, and in the case of a detread step steer. The model was developed in Java and Excel and tested for these step steer inputs.

Integrated Vehicle Stability Control And Power Distribution Using Model Predictive Control

Autor: Milad Jalaliyazdi
Publisher:
ISBN:
File Size: 58,57 MB
Format: PDF, ePub
Read: 1234
Download or Read Book
There is a growing need for active safety systems to assist drivers in unfavorable driving conditions. In these conditions, the behavior of the vehicle is different than the linear response during everyday driving. Even experienced drivers usually lose control of the vehicle in such situations and that often results in a car accident. Stability control systems have been developed over the past few decades to assist drivers in keeping the vehicle under control. Most of these control systems are comprised of separate modules, each responsible for one task such as yaw rate tracking, sideslip control, traction control or power distribution. These objectives may be in conflict in some driving situations. In such cases, individual controllers fight over priority and produce conflicting control commands, to the detriment of the vehicle performance. In addition, in most stability control systems, transferring the controller from one vehicle to another with a different driveline and actuator configuration requires significant modifications in the controller and major re-tuning to obtain a similar performance. This is a major disadvantage for auto companies and increases the controller design and tuning costs. In this thesis, an integrated control system has been designed to address vehicle stability, traction control and power distribution objectives at the same time. The proposed controller casts all of these objectives in a single objective function and chooses control actions to optimize this objective function. Therefore, the output of the integrated controller is not altered by another module and the optimality of the solution is not compromised. Furthermore, the designed controller can be easily reconfigured to work with various driveline configurations such as all-wheel drive, front or rear-wheel drive. In addition, it can also work with various actuator configurations such as torque vectoring, differential braking or any combination of them on the front or rear axles. Moving from one configuration to another does not change the stability control performance and major re-tuning can be avoided. The performance of the designed model predictive controller is evaluated in software simulations with a high fidelity model of an electric Equinox vehicle. The stability and wheel slip control performance of the controller is evaluated in various driving and road conditions. In addition, the effect of integrated power distribution is studied. Experimental tests with two different electric vehicles are also carried out to evaluate the real-time performance of the MPC controller. It is observed that the controller is able to maintain vehicle and wheel stability in all of the driving scenarios considered. The power distribution system is able to improve vehicle efficiency by approximately 1.5% and acts in cooperation with the stability control objectives.

Reconfigurable Integrated Vehicle Stability Control Using Optimal Control Techniques

Autor: Seyedeh Asal Nahidi
Publisher:
ISBN:
File Size: 29,85 MB
Format: PDF, Docs
Read: 8703
Download or Read Book
The motivation for the development of vehicle stability control systems comes from the fact that vehicle dynamic behavior in unfavorable driving conditions such as low road-tire adhesion and high speed differs greatly from its nominal behavior. Due to this unexpected behavior, a driver may not be successful in controlling the vehicle in challenging driving situations based only on her/his everyday driving experience. Several noteworthy research works have been conducted on stability control systems over the last two decades to prevent car accidents due to human error. Most of the resultant stability controllers contain individual modules, where each perform a particular task such as yaw tracking, sideslip control, or wheel slip control. These design requirements may contradict each other in some driving scenarios. In such situations, inconsistent control actions can be generated with individual modules. The development of a stability controller that can satisfy diverse and often contradictory requirements is a great challenge. In general, transferring a control structure from one vehicle to another with a different drivetrain layout and actuation system configuration requires remarkable rectifications and repetition of tuning processes from the beginning to achieve a similar performance. This can be considered to be a serious drawback for car manufacturing companies since it results in extra effort, time, and expenses in redesigning and retuning the controller. In this thesis, an integrated controller with a modular structure has been designed to concurrently provide control of the vehicle chassis (yaw rate and sideslip control) and wheel stability (wheel slip ratio control). The proposed control structure incorporates longitudinal and lateral vehicle dynamics to decide on a unified control action. This control action is an outcome of solving an optimization problem that considers all the control objectives in a single cost function, so integrated wheel and vehicle stability is guaranteed. Moreover, according to the particular modular design of the proposed control structure, it can be easily reconfigured to work with different drivetrain layouts such as all-wheel-drive, front-wheel-drive, and rear-wheel-drive, as well as various actuators such as torque vectoring, differential braking, and active steering systems. The high-level control module provides a Center of Gravity (CG) based error analysis and determines the required longitudinal forces and yaw moment adjustments. The low-level control module utilizes this information to allocate control actions optimally at each vehicle corner (wheel) through a single or multi-actuator regime. In order to consider the effect of the actuator dynamics, a mathematical description of the auction system is included in distribution objective function. Therefore, a legitimate control performance is promised in situations requiring shifting from one configuration to another with minimal modifications. The performance of the proposed modular control structure is examined in simulations with a high-fidelity model of an electric GM Equinox vehicle. The high-fidelity model has been developed and provided by GM and the use of the model is to reduce the number of labor-intensive vehicle test and is to test extreme and dangerous driving conditions. Several driving scenarios with severe steering and throttle commands, then, are designed to evaluate the capability of the proposed control structure in integrated longitudinal and lateral vehicle stabilization on slippery road condition. Experimental tests also have been performed with two different electric vehicles for real-time implementation as well as validation purposes. The observations verified the performance qualifications of the proposed control structure to preserve integrated wheel and vehicle chassis stability in all track tests.

Vehicle Dynamics Stability And Control Second Edition

Autor: Dean Karnopp
Publisher: CRC Press
ISBN: 146656086X
File Size: 54,76 MB
Format: PDF, Docs
Read: 3023
Download or Read Book
Anyone who has experience with a car, bicycle, motorcycle, or train knows that the dynamic behavior of different types of vehicles and even different vehicles of the same class varies significantly. For example, stability (or instability) is one of the most intriguing and mysterious aspects of vehicle dynamics. Why do some motorcycles sometimes exhibit a wobble of the front wheel when ridden "no hands" or a dangerous weaving motion at high speed? Why does a trailer suddenly begin to oscillate over several traffic lanes just because its load distribution is different from the usual? Other questions also arise: How do humans control an inherently unstable vehicle such as a bicycle and how could a vehicle be designed or modified with an automatic control system to improve its dynamic properties? Using mainly linear vehicle dynamic models as well as discussion of nonlinear limiting effects, Vehicle Dynamics, Stability, and Control, Second Edition answers these questions and more. It illustrates the application of techniques from kinematics, rigid body dynamics, system dynamics, automatic control, stability theory, and aerodynamics to the study of the dynamic behavior of a number of vehicle types. In addition, it presents specialized topics dealing specifically with vehicle dynamics such as the force generation by pneumatic tires, railway wheels, and wings. The idea that vehicles can exhibit dangerous behavior for no obvious reason is in itself fascinating. Particularly obvious in racing situations or in speed record attempts, dynamic problems are also ubiquitous in everyday life and are often the cause of serious accidents. Using relatively simple mathematical models, the book offers a satisfying introduction to the dynamics, stability, and control of vehicles.

Vehicle Stability Control Considering The Driver In The Loop

Autor: Saeid Khosravani
Publisher:
ISBN:
File Size: 66,93 MB
Format: PDF, ePub, Mobi
Read: 5657
Download or Read Book
A driver-in-the-loop modeling framework is essential for a full analysis of vehicle stability systems. In theory, knowing the vehicle's desired path (driver's intention), the problem is reduced to a standard control system in which one can use different methods to produce a (sub) optimal solution. In practice, however, estimation of a driver's desired path is a challenging - if not impossible - task. In this thesis, a new formulation of the problem that integrates the driver and the vehicle model is proposed to improve vehicle performance without using additional information from the future intention of the driver. The driver's handling technique is modeled as a general function of the road preview information as well as the dynamic states of the vehicle. In order to cover a variety of driving styles, the time- varying cumulative driver's delay and model uncertainties are included in the formulation. Given that for practical implementations, the driver's future road preview data is not accessible, this information is modeled as bounded uncertainties. Subsequently, a state feedback controller is designed to counteract the negative effects of a driver's lag while makes the system robust to modeling and process uncertainties. The vehicle's performance is improved by redesigning the controller to consider a parameter varying model of the driver-vehicle system. An LPV controller robust to unknown time-varying delay is designed and the disturbance attenuation of the closed loop system is estimated. An approach is constructed to identify the time-varying parameters of the driver model using past driving information. The obtained gains are clustered into several modes and the transition probability of switching between different driving-styles (modes) is calculated. Based on this analysis, the driver-vehicle system is modeled as a Markovian jump dynamical system. Moreover, a complementary analysis is performed on the convergence properties of the mode-dependent controller and a tighter estimation for the maximum level of disturbance rejection of the LPV controller is obtained. In addition, the effect of a driver's skills in controlling the vehicle while the tires are saturated is analyzed. A guideline for analysis of the nonlinear system performance with consideration to the driver's skills is suggested. Nonlinear controller design techniques are employed to attenuate the undesirable effects of both model uncertainties and tire saturation.

A Model Free Approach To Vehicle Stability Control

Autor: Chinmay Milind Pandit
Publisher:
ISBN:
File Size: 71,15 MB
Format: PDF, ePub, Mobi
Read: 8335
Download or Read Book
Abstract: This project explored the feasibility of using measured responses of a passenger car together with a fuzzy logic based control algorithm to sense the onset of under-steer (or loss of steering control) and mitigate or eliminate it. The controller is simple and robust and, unlike existing controllers, instead of comparing the vehicle response to that of an idealized model it makes decisions based solely upon the measured response of the car. Simulations were conducted (using CarSim) of various vehicles executing the skid pad and the double lane change tests to characterize the vehicle behavior. Consistent and qualitatively similar patterns in vehicle response during the inception of and at limit under-steer were observed. A fuzzy logic routine was developed that analyzes real-time measurements of steering wheel angle (SWA) and lateral acceleration (Ay). Based on the relative `trends' of the signals, the control algorithm decides upon the presence and extent of under-steer in the vehicle. The degree of under-steer then defines the corrective action. The fundamental concept is to measure a drop in the instantaneous lateral acceleration gain, i.e., Ay/SWA, indicating a lack of response. It is quantified as a normalized error and transformed into an under-steer number between 0 and 10 using a pair of fuzzy inference systems. Once incipient under-steer is detected, the brakes and engine throttle are managed to limit the lateral deviation from the travel lane. The controller also senses vehicle velocity, master cylinder brake pressure and normalized throttle input to improve controllability. This approach eliminates the need for either a simple or a complex vehicle model and the associated dependence on the model parameters. Controller performance was validated using a braking-in-turn maneuver developed by the author and the standard double lane change maneuver. The results have shown clear improvement in the tracking ability of a vehicle. The simulations were conducted at different speeds with each of several vehicles and with different tire-to-ground friction values without any changes to the control algorithm. This has shown that the controller is robust across different conditions. The controller is successful in increasing the maximum safe speed for a negotiating a curve for all vehicles on various road conditions. The last part of the controller was to combine it with an existing over-steer controller, developed at Clemson University, which also uses fuzzy logic. This was successfully completed to obtain a fully functional ESC system, independent of a vehicle model. Future work will include tuning the controller based on track data from real vehicles.

Theory Of Ground Vehicles

Autor: J. Y. Wong
Publisher: John Wiley & Sons
ISBN: 0470170387
File Size: 34,49 MB
Format: PDF
Read: 7243
Download or Read Book
Technology/Engineering/Automotive Engineering for advancing ground vehicle mobility A standard text and reference for both the educational and professional communities, Theory of Ground Vehicles gives aspiring and practicing engineers a fundamental understanding of the critical factors affecting the performance, handling, and ride essential to the development and design of ground vehicles. In view of the growing concerns over environmental impact, energy efficiency, and safety, this new Fourth Edition has been revised and expanded to address these issues and other developments in the field. Retaining the contents and format of previous editions, the Fourth Edition introduces new material to reflect recent advances in ground transportation technology, including: * Computer-aided methods for design and performance evaluation of off-road vehicles and their practical applications * Emissions and fuel economy * Hybrid electric drives and fuel cells and their operating principles * Selection of vehicle configurations for off-road operations * Road vehicle stability control * ISO 2631-1:1997 and its applications to evaluating vehicle ride characteristics As in previous editions, this book focuses on applying engineering principles to the analysis of vehicle behavior. A large number of practical examples and problems are included throughout to help readers bridge the gap between theory and practice. With its broad coverage and pedagogical aids, Theory of Ground Vehicles, Fourth Edition remains the text of choice for students, engineers, and researchers wishing to master and apply basic theory to solve real-world, road and off-road vehicle mobility problems.