Cornering Stiffness Estimation Research Articles

Electric Vehicle Lateral Dynamics Control based on Instantaneous Cornering Stiffness Estimation and an Efficient Allocation Scheme

AbstractBeyond the establishment of a polution free mobility, electric vehicles show attractive features as far as vehicle motion control is concerned. In this work an electric vehicle equipped with four independent In-Wheel-Motors and active front and rear steering system is considered. The 6 actuators should be controlled in a way to guarantee safe, comfortable and low energy consumption drive. Generally, Linear Time Invariant (LTI) vehicle models are appropriate if the motion of the vehicle does not approach the physical limits of the tire force saturation and road conditions remain constant. Otherwise, they fail to predict the vehicle dynamics. On the other hand the control design approach based on LTI models is straightforward. The approach taken in this contribution is the following: use a robust sliding mode controller based on a slowly linear time varying model, together with an efficient estimation scheme for the instantaneous cornering stiffness in order to prevent the vehice to reach lateral tire force saturation by restricting the possible actuator outputs in a control allocation scheme. Computer simulation runs with the professional vehicle dynamics environment CarSim show good performance of the control scheme. Further work will be the validation with real vehicle experiments and modelling of consumed energy for consideration of energy efficency in the control scheme.

Estimation of vehicle sideslip, tire force and wheel cornering stiffness

This paper presents a process for the estimation of tire–road forces, vehicle sideslip angle and wheel cornering stiffness. The method uses measurements (yaw rate, longitudinal/lateral accelerations, steering angle and angular wheel velocities) only from sensors which can be integrated or have already been integrated in modern cars. The estimation process is based on two blocks in series: the first block contains a sliding-mode observer whose principal role is to calculate tire–road forces, while in the second block an extended Kalman filter estimates sideslip angle and cornering stiffness. More specifically, this study proposes an adaptive tire-force model that takes variations in road friction into account. The paper also presents a study of convergence for the sliding-mode observer. The estimation process was applied and compared to real experimental data, in particular wheel force measurements. The vehicle mass is assumed to be known. Experimental results show the accuracy and potential of the estimation process.

Running stabilization control of electric vehicle based on cornering stiffness estimation

AbstractIn this paper, novel direct yaw moment control (DYC) with road condition estimation and anti‐slip control is proposed for electric vehicles. An inner‐loop observer controls the vehicle traction, and an outer‐loop observer stabilizes the yawing motion of the vehicle. An immeasurable parameter known as cornering stiffness is estimated from the detected yaw‐rate, steering angle, wheel speed and yaw moment observer output in real time. Thus, the accurate control input can be generated with the estimated parameters. The proposed adaptive control is compared with a conventional robust control method under dry and snowy terrain conditions. Experimental results show that the proposed control algorithm properly attenuates the yaw‐rate error. ©2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(4): 97–104, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20569

Integrating INS Sensors With GPS Measurements for Continuous Estimation of Vehicle Sideslip, Roll, and Tire Cornering Stiffness

This paper details a unique method for estimating key vehicle states-body sideslip angle, tire sideslip angle, and vehicle attitude-using Global Positioning System (GPS) measurements in conjunction with other sensors. A method is presented for integrating Inertial Navigation System sensors with GPS measurements to provide higher update rate estimates of the vehicle states. The influence of road side-slope and vehicle roll on estimating vehicle sideslip is investigated. A method using one GPS antenna that estimates accelerometer errors occurring from vehicle roll and sensor drift is first developed. A second method is then presented utilizing a two-antenna GPS system to provide direct measurements of vehicle roll and heading, resulting in improved sideslip estimation. Additionally, it is shown that the tire sideslip estimates can be used to estimate the tire cornering stiffnesses. The experimental results for the GPS-based sideslip angle measurement and cornering stiffness estimates compare favorably to theoretical predictions, suggesting that this technique has merit for future implementation in vehicle safety systems

Cornering stiffness estimation based on vehicle lateral dynamics

In this article, the cornering stiffness estimation problem based on the vehicle bicycle (one-track) model is studied. Both time-domain and frequency-domain-based methods are analyzed, aiming to estimate the effective cornering stiffness, defined as the ratio between the lateral force and the slip angle at the two axles. Several methods based on the bicycle model were developed, each having specific pros/cons related to practical implementations. The developed algorithms were evaluated on the basis of the simulation data from the bicycle model and the CarSimTM software. Finally, selected algorithms were evaluated using experimental data.