New adaptive approaches to real-time estimation of vehicle sideslip angle

This paper presents new approaches to the identification of the vehicle sideslip angle and the road bank angle in real-time. The major challenge is that the vehicle sideslip angle and the road bank angle are coupled together with the system uncertainties, such as variations in the vehicle parameters and the tire cornering stiffness. To resolve this difficulty, the proposed estimation algorithms identify the uncertain vehicle parameters using the sensor measurements such as the steering angle, the lateral acceleration and the yaw rate, and then estimate the vehicle sideslip angle and the road bank angle via a simple algebraic relationship in real time. In particular, the use of the lateral G sensor signal makes it possible to identify the cornering stiffness and vehicle sideslip angle without any a priori knowledge on the road bank angle. The performance of the proposed algorithms is verified through simulation and experimental results.     

Enhanced postural stability following driver training is associated with positive effects in vehicle kinematics during cornering

OBJECTIVE: The purpose of the study was to examine the effects of a specific post-license driver training program on postural stability and vehicle kinematics during cornering. BACKGROUND: Inertial forces experienced during driving can perturb a driver's posture, which may in turn diminish a driver's perceptual sensitivity and corresponding control actions. METHODS: A trainee group (n=21) and control group (n=12) participated in the study. The trainee group participated in a 2-day driver training program that included instruction on how to enhance perceptual sensitivity, postural stability, and vehicle kinematics during common driving maneuvers, including cornering. Postural stability and vehicle kinematics were assessed during cornering maneuvers performed on a closed-circuit track using an instrumented vehicle prior to and following training. RESULTS: Trainee drivers experienced enhanced postural stability and reduced the magnitude and onset of peak vehicle lateral accelerations following training. Prior to training, drivers who were more posturally unstable tended to experience higher lateral vehicle accelerations, and drivers with the biggest improvements in postural stability following training tended to experience the greatest reductions in lateral accelerations of the vehicle. CONCLUSION: Training led to changes in postural stability that were associated with reduced lateral accelerations during cornering. APPLICATION: The reduction in lateral accelerations following training in the present study indicates a greater dynamic margin of safety for cornering. Overall findings suggest that the driver training programs produced beneficial effects on cornering kinematics and that these effectswere associated with enhanced postural stability.     

Tire–road friction coefficient and tire cornering stiffness estimation based on longitudinal tire force difference generation

A sequential tire cornering stiffness coefficient and tire–road friction coefficient (TRFC) estimation method is proposed for some advanced vehicle architectures, such as the four-wheel independently-actuated (FWIA) electric vehicles, where longitudinal tire force difference between the left and right sides of the vehicle can be easily generated. Such a tire force difference can affect the vehicle yaw motion, and can be utilized to estimate the tire cornering stiffness coefficient and TRFC. The proposed tire cornering stiffness coefficient and TRFC identification method has the potential of estimating these parameters without affecting the vehicle desired motion control and trajectory tracking objectives. Simulation and experimental results with a FWIA electric vehicle show the effectiveness of the proposed estimation method.     

A method to improve the stability of adaptive steering driver-vehicle systems

If the behavior of a combined vehicle tracks the behavior of an ideal vehicle model, the good handling performance can be maintained with large variations in the dynamics of the combined vehicles. Based on this notion, we have developed an adaptive steering controller which achieves good tracking performance. However, we designed an ideal vehicle model without considering variations in the abilities of the driver. If an adequate ideal vehicle model can be designed which can adapt to variations in the abilities of the drivers, a better handling performance of an adaptive combined driver-vehicle system can be realized. In this article, attention is focused on the lane change maneuver and the cornering maneuver, and we propose a new scheme to design an ideal vehicle model which can adapt to variations in the abilities of the driver. Finally, by carrying out numerical simulations, it is shown that the ideal vehicle model which was designed is very effective.     

轮式移动机器人滑移量重建与滑移补偿控制

为解决轮式移动机器人的滑移补偿控制问题,首先推导出车体侧滑角的表达式,然后将时变侧滑角的重建问题转化为对地面特性参数的辨识问题.利用Luenberger观测器设计出自适应辨识律,并证明了当控制输入满足持续激励条件时,可以准确辨识出地面特性参数.基于链式系统模型设计出滑移补偿控制器,在滑移角精确已知的条件下,可以保证位置误差收敛,姿态误差有界.仿真结果表明,基于所设计的自适应辨识律,可以准确地重建出滑移角,提高滑移控制精度.     

智能车辆横向控制研究

本文分析了智能车辆横向控制特性，说明了目前一些研究中的不足，并探讨了 模糊控制方法．仿真结果表明，该算法对纵向速度、轮胎侧偏刚度以及载荷等明显影响车辆 横向运动特性的三个关键因素具有良好的适应性能．     

采用神经网络轮胎模型的汽车操纵稳定性仿真

运用人工神经网络理论中的多层前向ＢＰ网络,建立轮胎侧偏特性模型,进而将人工神经网络轮胎代人车模型中进行操纵稳定性仿真研究。     

汽车操纵稳定性稳态响应参数的单位与量纲

针对表征汽车操纵稳定性状态的稳定性因数等参数的单位规定比较混乱的现状,根据角度物理量有单位但无量纲的特点,在轮胎侧偏刚度取两种不同单位的情况下,对汽车转向稳态响应的稳定性因数及稳态横摆角速度增益等重要参数的单位及量纲进行了全面分析.     

非独立悬架车辆自激摆振的数值仿真分析

基于一个三自由度的转向系统模型,利用数值仿真方法分析了横拉杆刚度、主销后倾角、转向机刚度、轮胎侧偏刚度、轮胎拖距、转向机阻尼、绕主销当量阻尼等参数对载重汽车自激型摆振的影响.仿真分析的结果表明,上述参数发生变化时,可诱发自激摆振,但车速也是影响摆振的关键因素之一.在确定的系统参数和车速下,初始激励不仅可能诱发稳定的自激摆振,还可能是发散的运动.与受迫型自激摆振不同,自激型摆振的频率变化与车速的变化并不一致.     

Estimation of Light Commercial Vehicles Dynamics by Results of Road Tests and Simulation

The chassis of LCV could be used for creating a wide range of vehicles modifications with the similar base （chassis）, but really different performance in wide range of maneuvers. The differences could be explained by a variety of design parameters. It means that the design of LCV modifications needs some effective approach that will provide an engineer by necessary data that could help to estimate the performance of new vehicles in particular active safety characteristics. This paper presents the combination of experiment and simulation methods that could be used for estimation of LCV active safety characteristics （first of all cornering stability）. The experimental method of estimation of cornering stability is shown, that is based on regulations of the Russian Standard GOST R 31507-2012 that presupposes different types of testing： static rollover and dynamic maneuvering on a road （line changing and running into the corner）. The multi-body simulation method with using MSC. ADAMS/CAR software was also used in a study. The approval of developed LCV multi-body model was made on a basis of good correlation between simulation results and experimental data. The relationship between LCVs design parameters （axle load distribution, height of the center of gravity, vertical and angular suspension stiffiaess） and active safety characteristics are received.     

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.     

Relaxed static stability based on tyre cornering stiffness estimation for all-wheel-drive electric vehicle

A novel dynamics control approach for all-wheel-drive electric vehicle (EV), relaxed static stability (RSS) approach is proposed with two advantages. Firstly, it allows vehicle lateral dynamics system to be inherent unstable to improve configuration flexibility. Secondly, handling performance could be improved based on closed-looped pole assignment with additional yaw moment. In this paper, basic control framework of RSS is proposed, including ‘Desired Pole Location’, ‘Pole Assignment’ and ‘Tyre Cornering Stiffness Estimation’ modules. The tyre cornering stiffness is estimated online to improve the robustness of the controller. The experiments based on an EV testbed show the performance and efficiency of RSS.     

Evaluation of a sliding mode observer for vehicle sideslip angle

This paper presents a sliding mode observer of vehicle sideslip angle, which is the principal variable relating to the transversal forces at the tire/road interface. The vehicle is first modelled, and the model is subsequently simplified. This study validates the observer using both a validated simulator and real experimental data acquired by the Heudiasyc laboratory car, and also shows the limitations of this method. The observer requires a yaw rate sensor and data about vehicle speed are required in order to estimate sideslip angle. Some properties of the nonlinear observability matrix condition number are discussed, and relations between this variable and observation error, vehicle speed and tire cornering stiffness are presented.     

A Tire Stiffness Backstepping Observer Dedicated to All-Terrain Vehicle Rollover Prevention

Most active devices focused on vehicle stability concern on-road cars and cannot be applied satisfactorily in an off-road context, since the variability and the non-linearities of tire/ground contact are often neglected. In previous work, a rollover indicator devoted to light all-terrain vehicles accounting for these phenomena has been proposed. It is based on the prediction of the lateral load transfer. However, such an indicator requires the on-line knowledge of the tire cornering stiffness. Therefore, in this paper, an adapted backstepping observer, making use only of yaw rate measurement, is designed to estimate tire cornering stiffness and to account for its non-linearity. The capabilities of such an observer are demonstrated and discussed through both advanced simulations and actual experiments.     

Detection of Impending Vehicle Rollover with Road Bank Angle Consideration Using a Robust Fuzzy Observer

 This article describes a method of vehicle dynamics estimation for impending rollover detection. We estimate vehicle dynamic states in presence of the road bank angle as a disturbance in the vehicle model using a robust observer. The estimated roll angle and roll rate are used to compute the rollover index which is based on the prediction of the lateral load transfer. In order to anticipate rollover detection, a new method is proposed to compute the time to rollover (TTR) using the load transfer ratio (LTR). The nonlinear model, deduced from the vehicle lateral and roll dynamics, is represented by a Takagi-Sugeno (T-S) fuzzy model. This representation is used to account for the nonlinearities of lateral cornering forces. The proposed T-S observer is designed with unmeasurable premise variables to cater for non-availability of the slip angles measurement. The proposed approach is evaluated using CarSim simulator under different driving scenarios. Simulation results show good efficiency of the proposed T-S observer and the rollover detection method.     

Experimental Verification of a Drift Controller for Autonomous Vehicle Tracking: a Circular Trajectory Using LQR Method

This study develops an autonomous vehicle control method that enables it to perform a drift maneuver which is an expert driving technique consisting of sliding the rear wheel intentionally for fast cornering. By developing an autonomous control algorithm for such an agile maneuver, the safety of the future autonomous vehicle on extreme conditions such as slippery road, will be increased. Drift equilibrium states are derived to find the suitable feedforward control input for the scale car to enter the drifting region. In addition, a feedback controller is designed based on the linear quadratic regulator method in order to track the circular trajectory and maintain drift equilibrium states. To validate the performance of the developed control algorithm a 1:10 scale car experimental platform is developed with on-board control and sensor system. The feasibility of the developed method for the autonomous vehicle is confirmed through both simulation and experiments following circular trajectories while maintaining the desired equilibrium states.

     

基于参数估计的半挂汽车列车稳定性控制研究

车辆参数估计是半挂汽车列车稳定性控制研究的关键,通过递推最小二乘法（RLS）估计整车质量和轮胎侧偏刚度,进而获取挂车横摆转动惯量,将估计的车辆参数应用于稳定性控制系统,修正控制系统参数.基于商用车动力学仿真软件TruckSim建立了某半挂汽车列车的非线性整车仿真模型,在Matlab/Simulink中设计建立了稳定性控制逻辑和参考响应模型,通过TruckSim-Simulink的联合仿真对控制方案进行了验证分析.结果表明,基于名义参数设计的控制系统受载重变化的影响较大,而带有参数估计的控制系统由于能够对控制参数进行修正,可以较好地适应载运工况的变化,受载运工况的影响较小.     

无人陆地车辆的自学习PD迭代纵向控制器

本文研究自动汽车速度跟踪问题，由于汽车纵向动力学中存在严重非线性和不确定性，本文提出设计一种自学习ＰＤ迭代非线性控制器。只要选择合适的控制器增益和训练因子，可使跟踪误差足够小。增益的选择几利不依赖于动力学，只与状态量变化范围有关。因此，此方法对许多控制对象均可施用。有理论和实验结果证明此方法的有效性。     

Local asymmetrical corner trajectory smoothing with bidirectional planning and adjusting algorithm for CNC machining

The linear motion command (G01) is a widely used command format in CNC machining. However, the tangential direction discontinuity at the corner junction will cause velocity fluctuations and excite the structural vibration of machine tools. Corner smoothing methods with controlled tolerance are used to obtain continuous smooth motion. Typically, most methods generate a symmetrical cornering trajectory around the angle bisector, and the trajectory generally decelerates first and then accelerates, which limits the velocity increase. In this paper, a novel local asymmetrical corner trajectory smoothing method is proposed, which can realize accelerated/decelerated cornering transition. The proposed method can obtain the analytical solution in one step, which is different from two-step geometric-based corner path smoothing, and can generate the same cornering trajectory in back-and-forth parallel toolpath. In addition, this paper proposes a bidirectional planning and adjusting algorithm for the situation where smoothed cornering paths are close to each other or even overlap. The algorithm can generate a jerk-limited trajectory by coordinating the cornering error of adjacent corners, while respecting the user-specified tolerance. Experimental results demonstrate the effectiveness of the proposed method in contour accuracy and cycle time for CNC machining along short-segmented toolpath.     

Integrated Dynamics Control and Energy Efficiency Optimization for Overactuated Electric Vehicles

A large number of studies have been conducted on the dynamics control of electric vehicles or on the optimization of their energy efficiency but few studies have looked at both of these together. In this study, an integrated dynamics control and energy efficiency optimization strategy is proposed for overactuated electric vehicles, where the control of both longitudinal and lateral dynamics is dealt with while the energy efficiency is optimized. First, considering the trade‐off between control performance and energy efficiency, criteria are defined to categorize the vehicle motion status as linear pure longitudinal motion and non‐linear motion or turning motion. Then different optimization targets are developed for different motion status. For the pure linear longitudinal motion and cornering motion, the energy efficiency and vehicle dynamics performance are equally important and a trade‐off control performance between them needs to be achieved. For the non‐linear turning motion, vehicle handling and stability performance are the primary concerns, and energy efficiency is a secondary target. Based on the defined targets, the desired longitudinal and lateral tyre forces and yaw moment are then optimally distributed to the wheel driving and steering torques. Finally numerical simulations are used to verify the effectiveness of the proposed strategies. The simulation results show that the proposed strategies can provide good dynamics control performance with less energy consumption.