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SAE 2004 Automotive Dynamics, Stability & Controls Conference and Exhibition
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Dana Torque Vectoring Differential Dynamic Trak™

Dana Corporation-John Park, William J. Kroppe
Published 2004-05-04 by SAE International in United States
This paper presents a novel torque-vectoring (biasing) differential system Dynamic Trak™ that can be applied to both the inter-axle and the inter-wheel differential systems. The Dynamic Trak™ has three multi-plate clutches. The center clutch located inside the differential case provides a limited-slip or complete lock-up capability. The two outboard clutches positioned at either sides of the differential case selectively adjust the torque flow to the left or right shafts/wheels. An electronic control unit and a hydraulic circuit unit control the three clutches, realizing the active management of the torque to the two output shafts/wheels. The Dynamic Trak™ can provide maximum of 100% torque add or subtraction to the wheels, while maintaining the open differential feature. A virtual model representing a passenger car equipped with the Dynamic Trak™ has been developed. The simulation results show the handling and stability enhancements by the Dynamic Trak™.
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Study of DSP-Based Measuring Technique of Jerk

State Key Laboratory of Automotive Safety and Energy, Tsinghua University, Beijing, P.R. China-Quanan Huang, Huiyi Wang
Published 2004-05-04 by SAE International in United States
A DSP-based (digital-signal-processing-based) measuring technique of jerk is proposed in this paper. By analyzing the frequency characteristics of jerk, we design a low pass digital differentiator suitable for jerk measuring. The digital differentiator is a linear-phase FIR system, and has the advantages of low order, favorable low frequency performance and good suppression of upper band frequencies. A measuring device has been developed based on this measuring technique, and has been used in practical applications. The accuracy and stability of the measuring device have been verified by experiments, which also approved the good performance of our DSP-based measuring technique of jerk.
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Improvement of Vehicle Lateral Dynamics by Active Front Steering Control

Helwan University, Cairo, Egypt-W. A. H. Oraby, S. M. El-Demerdash, A. M. Selim
University of Leeds, Leeds, UK-D. A. Crolla
Published 2004-05-04 by SAE International in United States
In this work, the active front steering control is studied using linear three degrees of freedom handling model incorporating the driver’s operation model and vehicle suspension derivatives. The active steering control strategy is based on the optimal control theory. In this design, the active front steering angle is determined based on minimizing all model state variables and full state feedback gains. The results are generated when the model is excited by random wind excitation, which was modeled as quasi-static approach with statistical properties taken from previous work, and presented in frequency domain as power spectral density as well as root mean square values in tables. Significant improvements are achieved for the vehicle handling characteristics using active front steering control in comparison with active four wheel steering and conventional two wheel steering.
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Investigation of Active Steering/Wheel Torque Control at the Rollover Limit Maneuver

Design Research Engineering-Daniel Toomey
University of Michigan-Dearborn-Taehyun Shim
Published 2004-05-04 by SAE International in United States
It is well understood that driver's steering input strongly affects lateral vehicle dynamics and excessive steering command may result in unstable vehicle motion. In a certain driving condition, it is possible for a skilled driver to prevent vehicle rollover with better perceptive capability of judging conditions and responding faster with smooth compensatory actions. This paper investigates the possibility of using active steering and wheel torque control to assist drivers in avoiding vehicle rollovers in emergency situations. The effectiveness of steering control alone and combination of steering/wheel torque control in recovery from unstable vehicle roll condition was demonstrated through simulation of both low and high vehicle speeds.
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On the Optimal Predictive Control Algorithm for Comfort-Oriented Semi-Active Suspensions

Dipartimento di Elettronica e Informazione, Politecnico di Milano, ITALY-Sergio M. Savaresi, Enrico Silani
Published 2004-05-04 by SAE International in United States
The problem considered in this paper is the design and analysis of the optimal control strategy for comfort-oriented semi-active suspensions in road vehicles. The goal of this work is to study and analyze the best control algorithm, and to use it as a benchmark. It is shown that the best control algorithm is an on-off switching strategy, which is designed using the principles of optimal and predictive control, under the assumption that the road disturbance can be predicted over a short time-horizon. Even though this optimal control strategy can be computationally intensive in a real-time application, it sets a lower bound on the best possible attenuation performance achievable by semi-active damping control.
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Can Semiactive Dampers with Skyhook Control Improve Roll Stability of Passenger Vehicles?

Vibration and Sound Solutions, Ltd-David E. Simon
Virginia Tech-Mehdi Ahmadian
Published 2004-05-04 by SAE International in United States
Skyhook control has been used extensively for semiactive dampers for a variety of applications, most widely for passenger vehicle suspensions. This paper provides an experimental evaluation of how well skyhook control works for improving roll stability of a passenger vehicle. After discussing the formulation for various semiactive control methods that have been suggested in the past for vehicle suspensions, the paper includes the implementation of a semiactive system with magneto-rheological (MR) dampers on a sport utility vehicle. The vehicle is used for a series of road tests that includes lane change maneuvers, with different types of suspensions. The suspensions that are tested include the stock suspension, the uncontrolled MR dampers, skyhook control, and a new semiactive control method called “SIA skyhook.” The SIA Skyhook augments the conventional skyhook control with steering input, in order to account for the suspension requirements during a lateral maneuver. The results of the study show that although conventional skyhook control does not provide any significant roll stability, SIA skyhook can improve the suspension travel and lateral forces at the vehicle…
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Feasibility Study for a Vehicle-Trailer Backing Up Control

General Motors R&D and Planning Center-Yong H. Lee, Weiwen Deng, Yuen-Kwok Steve Chin, Neil McKay
Published 2004-05-04 by SAE International in United States
A rear-wheel steer-by-wire mechanism has been applied to assist driver on backing up a vehicle with trailer. To address the issues related to the mechanical limitation on the rear-wheel steering angle, a comprehensive feasibility study has been conducted using analysis and simulation. Four modes of steering (front-wheel only steering, rear-wheel only steering, rear-wheel angle which is slave to front-wheel angle, and four wheel steering for backing control) are compared in terms of various parameters, such as achievable path curvature and hitch angle. Four wheel steering achieves the largest curvature range. Sensitivity to the variation in trailer tongue length also has been investigated. It is concluded that a proper driver interaction mechanism is needed to further assist the driver, since the ±12 degree limitation on rear-wheel only steering may not provide full counter-steer capability.
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Control of an Electromechanical Brake for Automotive Brake-By-Wire Systems with an Adapted Motion Control Architecture

The University of Melbourne-Chris Line, Chris Manzie, Malcolm Good
Published 2004-05-04 by SAE International in United States
A disk brake clamp force controller for electromechanical brakes (EMB) in automotive brake-by-wire systems may be obtained from a standard motion control architecture with cascaded position, speed and current control loops by replacing the outer position control loop with a force control loop. When implemented with proportional, integral and differential (PID) controllers this architecture generally performs well for standard motion control problems, but the EMB control problem is differentiated by a large operating range in which non-linear load disturbances such as friction become significant at high clamp forces of up to 30kN. This paper investigates the feasibility of a cascaded PI control architecture for an EMB with the intention of establishing a baseline standard against which the performance of future control schemes may be compared. Simulation results are presented based on an accepted EMB model.
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A Study of the Effect of Various Vehicle Properties on Rollover Propensity

Department of Mechanical Engineering, Auburn University-Randy Whitehead, William Travis, David M. Bevly, George Flowers
Published 2004-05-04 by SAE International in United States
This paper investigates the effect of various vehicle parameters on rollover propensity using computer simulation. The computer simulation’s accuracy is verified by comparing it to experimental data from NHTSA’s Phase IV testing on rollover of passenger vehicles. The vehicle model used in the simulation study considers the non-linear, transient dynamics of both yaw and roll motion. The vehicle model is subjected to a specific steering input defined by NHTSA, the Fishhook 1a. A correlation between the vehicle parameter of center of gravity location and rollover propensity is found using the validated vehicle simulation.
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Control of Sideslip and Yaw Rate in Cars Equipped with 4-Wheel Steer-by-Wire

DaimlerChrysler Research and Technology, Germany-Jens Kalkkuhl
Hamilton Institute, National University of Ireland-Miguel A. Vilaplana, Douglas J. Leith, William E. Leithead
Published 2004-05-04 by SAE International in United States
This paper presents a new steering controller for cars equipped with 4-wheel steer-by-wire. The controller commands the front and rear steering angles with the objective of tracking reference sideslip and yaw rate signals describing the desired car lateral dynamics. In addition, the controller automatically rejects any disturbances in sideslip and yaw rate caused, for example, by μ-split braking manoeuvres or lateral wind gusts. The structure of the controller is based on a simplified model of the lateral dynamics of 4-wheel steering cars. This structure allows an originally complex multivariable control design problem to be broken down into two simpler single-input, single-output (SISO) control design problems by means of the Individual Channel Design (ICD) methodology. Within the proposed structure, individual sideslip and yaw rate controllers, valid for varying vehicle speed, can be designed using classical linear control design techniques. An anti-windup scheme has been incorporated into the steering controller to mitigate the effects of the saturation or failure of the rear steering actuators. Results from a detailed non-linear simulation model are given to illustrate the controller's…
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