Yaw Moment Control Strategy for Four Wheel Side Driven EV

When four wheel side driven EV travals in steering or changes lanes in high speed, the vehicle is easy to side-slip or flick due to the difference of wheel hub motor and a direct effect of vehicle nonlinear factors on vehicle yaw motion, which would affect vehicle handling and stability seriously. To solve this problem, a joint control strategy, combined with the linear programming algorithm and improved sliding mode algorithm, which combines the exponential reaching law and saturation function was proposed. Firstly, the vehicle dynamics model and the reference model according with the structure and driving characteristics of four wheel side driven EV were set up. Then, introduced the basic method of the improved sliding mode variable structure control and complete the sliding mode variable structure controller design basic on vehicle sideslip angle and yaw velocity.The controller accomplish optimal allocation of vehicle braking force through a linear programming algorithm, according to yaw moment produced by the vehicle motion state. Single lane driving simulation results show that the proposed control strategy can not only control vehicle sideslip angle and yaw velocity well, but also accomplish good controlling of the vehicle yaw moment, so as to significantly improve the handling and stability of vehicle.     

汽车横摆的动态模型

建立横摆动态模型是汽车横摆稳定控制的基础．本文根据汽车横摆稳定控制的特点,综合车身横摆动态,车轮动态和轮胎的非线性特性,建立了非线性离散横摆动态模型,其中轮胎摩擦力为时变参数．为了估计本模型中的时变参数,本文进而设计了离散滑模估计器估计轮胎摩擦力．最后,在一个高精度的汽车动力学仿真环境中,证实了本估计方法可有效地估计车轮摩擦力,所建立模型较为准确地反映汽车横摆动态．     

Integrated vehicle dynamics management for distributed‐drive electric vehicles with active front steering using adaptive neural approaches against unknown nonlinearity

This paper proposes a new integrated vehicle dynamics management for enhancing the yaw stability and wheel slip regulation of the distributed‐drive electric vehicle with active front steering. To cope with the unknown nonlinear tire dynamics with uncertain disturbances in integrated control problem of vehicle dynamics, a neuro‐adaptive predictive control is therefore proposed for multiobjective coordination of constrained systems with unknown nonlinearity. Unknown nonlinearity with unmodeled dynamics is modeled using a random projection neural network via adaptive machine learning, where a new adaptation law is designed in premise of Lyapunov stability. Given the computational efficiency, a neurodynamic method is extended to solve the constrained programming problem with unknown nonlinearity. To test the performance of the proposed control method, simulations were conducted using a validated vehicle model. Simulation results show that the proposed neuro‐adaptive predictive controller outperforms the classical model predictive controller in tracking nominal wheel slip ratio, desired vehicle yaw rate and sideslip angle, showing its significance in vehicle yaw stability enhancement and wheels slip regulation.     

考虑高速公路横向坡道转向行驶操纵稳定性的汽车轴距和轮距分析

为分析汽车轴距和轮距设计对操纵稳定性的影响,建立高速公路横向坡道转向行驶的汽车转向动力学模型,并在MATLAB/Simulink软件中建立相应的仿真模型.采用某型汽车设计轴距和轮距进行仿真,得到以不同速度在不同横向坡度道路上转向行驶时的横摆角速度、侧向加速度和质心侧偏角.根据该型汽车的转向特性和侧翻阈值评价其在高速公路横向坡道转向行驶时的操纵稳定性,结果表明该型汽车的设计轴距和轮距满足操纵稳定性要求.计算方法和仿真结果对整车设计具有指导意义.     

Studies on improving vehicle handling and lane keeping performance of closed-loop driver–vehicle system with integrated chassis control

This study proposes a new integrated robust model matching chassis controller to improve vehicle handling performance and lane keep ability. The design framework of the H_∞ controller is based on linear matrix inequalities (LMIs), which integrates active rear wheel steering control, longitudinal force compensation and active yaw moment control. To comprehensively evaluate the performance of the integrated chassis control system, a closed-loop driver–vehicle system is used. The effectiveness of the integrated controller on handling performance improvement is tested by a vehicle without driver model under a crosswind disturbance. At the same time, both the handling and lane keeping improving performance of the closed-loop driver–vehicle system is evaluated by tracking an S shape winding road. The simulation results reveal that the integrated chassis controller not only achieves preferable handling performance and stability, but also improves the vehicle lane keep ability significantly, and can alleviate the working load of the driver.     

Robust vehicle steering control design based on the disturbance observer

A robust steering controller is introduced for improving the yaw dynamics of a passenger car. A specific two degree of freedom control architecture known as the disturbance observer is adapted to the vehicle yaw dynamics control problem and shown to robustly improve performance. The relevant design specifications are formulated in terms of eigenvalues (Γ-stability) and in frequency domain as bounds on weighted sensitivity and complementary sensitivity functions (β-stability). The parameter space method is used to map the specifications for controller design. A Popov criterion based nonlinear stability analysis is also carried out to prove robust absolute stability (Φ-stability) in the presence of actuator rate limitation. Simulations are used to demonstrate the effectiveness of the final design.     

An intelligent approach to the lateral forces usage in controlling the vehicle yaw rate

A direct yaw moment control system (DYC) is designed to improve the handling and stability of a four‐wheel‐drive electric vehicle. The main task of this paper is to use the lateral forces in the process of optimally controlling vehicle stability. This is performed by defining a variable optimum region for the slip ratio of each wheel. A hierarchical structure is selected to design the control system. The higher‐level control system controls the yaw rate of the vehicle based on the fuzzy logic technique. The lower‐level control system, installed in each wheel, maintains the slip ratio of the same wheel within an optimum region using the fuzzy logic technique. This optimum region for each wheel is continuously modified based on the impact of the lateral force on the generated control yaw moment and the friction coefficient of the road. Therefore, an algorithm for estimation of the friction coefficient is proposed. Computer simulations are carried out to investigate the effectiveness of the proposed method. This is accomplished by comparison of the results of control methods with a fixed slip ratio region and the results of the proposed method with a variable slip ratio region in some maneuvers. The robustness of the proposed controller against hard braking and noise contamination, as well as the effect of steering wheel angle amplitude, is verified. The simulation results show that the influence of the proposed method on enhancing vehicle performance is significant. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

基于UIO的EPS系统状态反馈最优控制

准确地获知电动助力转向（Electric powering steering,EPS）系统阻力矩是提高行车安全的一个重要因素.针对车辆转向过程中,由不同附着路面上EPS 系统所需辅助力矩与转向路感之间的差别而可能导致的误操纵问题,本文基于2自由度整车动力学的EPS系统模型,结合轮胎特性,以轮胎侧偏角和理想路面附着系数为输入,通过设计非线性观测器估计当前路面的附着系数,以获取EPS系统阻力矩;进而,根据EPS 系统模型,运用未知输入观测器（Unknown input observer,UIO）估算方向盘输入转矩,并基于EPS系统状态反馈以实现对EPS系统的无传感器最优控制.最后,对基于永磁同步电机（Permanent magnet synchronous motor,PMSM）的EPS系统进行仿真实验分析.结果表明: 在以电机q轴电流闭环误差最小为指标函数情形下,本设计的方向盘回正残留角从25°降到0°,能有效抑制系统外界干扰,提高了转向时人-车系统的鲁棒性.     

Nested PID steering control for lane keeping in autonomous vehicles

In this paper a nested PID steering control in vision based autonomous vehicles is designed and experimentally tested to perform path following in the case of roads with an uncertain curvature. The control input is the steering wheel angle: it is designed on the basis of the yaw rate, measured by a gyroscope, and the lateral offset, measured by the vision system as the distance between the road centerline and a virtual point at a fixed distance from the vehicle. No lateral acceleration and no lateral speed measurements are required. A PI active front steering control based on the yaw rate tracking error is used to improve the vehicle steering dynamics. The yaw rate reference is computed by an external control loop which is designed using a PID control with a double integral action based on the lateral offset to reject the disturbances on the curvature which increase linearly with respect to time. The proposed control scheme leads to a nested architecture with two independent control loops that allows us to design standard PID controls in a multivariable context (two outputs, one input). The robustness of the controlled system is theoretically investigated with respect to speed variations and uncertain vehicle physical parameters. Several simulations are carried out on a standard big sedan CarSim vehicle model to explore the robustness with respect to unmodelled effects. The simulations show reduced lateral offset and new stable μ-split braking maneuvres in comparison with the model predictive steering controller implemented by CarSim. Finally the proposed control law is successfully tested by experiments using a Peugeot 307 prototype vehicle on the test track in Satory, 20 km west of Paris.     

Vehicle Dynamics Modeling and Electronic Stability Program/ Active Front Steering Sliding Mode Integrated Control

Chassis integrated control can significantly improve vehicle handling stability and comfort. Because of the complexity of the problem, it has attracted significant research attention. We built a vehicle nonlinear dynamic model with multi‐degree freedom, including body movement, wheel movement, and electronically controlled hydraulic power steering system. We compared the magic formula tire model, Dugoff tire model, brush tire model, and LuGre dynamic friction tire model and steady model. The precision of the model was verified by a comparison between simulation results and the real vehicle test results. Then, based on the vehicle dynamics model, an AFS (active front steering) controller was designed based on sliding mode variable structure control, and an AFS and ESP (electronic stability program) integrated coordination controller was proposed. Finally, based on the nonlinear tire model and multi‐DOF (degree of freedom) vehicle model, sinusoidal and step steering angle input simulation analysis was proposed on different road friction coefficients. The results show that the vehicle has better response characteristics with coordinated control strategy when compared with AFS and ESP only control. The evidence suggests that the proposed integrated control system in this paper can improve vehicle stability and safety.     

Nonlinear decoupling control of four-wheel-steering vehicles with an observer

This paper studies the input-output decoupling control for the nonlinear vehicle model consisting of three degrees of freedom. The technique of quasi-linearization is used to simplify the vehicle model, which preserves inherent coupling effects between longitudinal acceleration/braking force, steering angles and the vehicle states. By choosing the combined control inputs, the input-output map of the vehicle dynamical system is reconstructed. Based on the model, the input-output decoupling controller is proposed. Furthermore, an asymptotically stable observer is presented. A modified form of mean value theorem is used to design the observer for the nonlinear vehicle system with bounded Jacobian. The observer gain can be obtained by solving linear matrix inequalities (LMIs). Several simulations are carried out to show the improvements in vehicle handling and stability due to the inputoutput decoupling control.     

基于光滑二阶滑模的可重复使用运载器有限时间再入姿态控制

针对可重复使用运载器(reusable launch vehicle,RLV)的六自由度再入模型,考虑模型不确定和外界干扰对再入姿态控制的影响,提出了一种非线性鲁棒控制策略.首先,根据多时间尺度特性将RLV的再入姿态模型分为姿态角子系统和姿态角速率子系统.其次,对每个子系统分别设计光滑二阶滑模控制器和滑模干扰观测器实现子系统的有限时间稳定.利用干扰观测器可以实现对不确定和外界干扰的精确估计,从而对控制器进行有效的补偿.进而,基于Lyapunov理论证明了整个系统的有限时间稳定.最后,通过仿真验证了提出的控制策略具有良好的控制性能和鲁棒性.     

一种基于前馈－反馈复合控制方式的制动稳定性控制方法

设计了一种前馈—反馈复合控制结构，将直接横摆力矩控制和主动前轮转向控制相结合以提高制动稳定性．控制器将前轮转向角视为输入，将外部侧向干扰力和力矩作用视为扰动，通过前馈校正补偿转向角引起的状态变化；同时建立扰动状态观测器，采用反馈控制校正消除外部扰动引起的状态误差．仿真试验证实这种控制方法在提高制动稳定性方面有良好的效果．     

四轮转向车辆操纵稳定性仿真分析

对四轮转向车辆的转向特性进行了理论分析,并对某控制策略的四轮转向车辆为例进行了仿真.建立了四轮转向车辆操纵动力学模型,分析了前轮角阶跃输入下四轮转向车辆的稳态响应和瞬态响应与传统前轮转向车辆的主要区别;在四轮转向车辆状态方程的基础上二求解出横摆角速度和侧向加速度与前轮转角的传递函数,与前轮转向车辆对比分析了传递函数零、极点位置对响应特性的影响.借助Matlab/Simulink,对四轮转向车辆进行仿真,发现仿真结果与理论分析吻合.将仿真结果与前轮转向车辆进行比较,阐明了四轮转向车辆的性能优势.研究结果可为评价四轮转向车辆的系统设计提供理论依据.     

Active steering control strategy for articulated vehicles

To improve maneuverability and stability of articulated vehicles, we design an active steering controller, including tractor and trailer controllers, based on linear quadratic regulator (LQR) theory. First, a three-degree-of-freedom (3-DOF) model of the tractor-trailer with steered trailer axles is built. The simulated annealing particle swarm optimization (SAPSO) algorithm is applied to identify the key parameters of the model under specified vehicle speed and steering wheel angle. Thus, the key parameters of the simplified model can be obtained according to the vehicle conditions using an online look-up table and interpolation. Simulation results show that vehicle parameter outputs of the simplified model and TruckSim agree well, thus providing the ideal reference yaw rate for the controller. Then the active steering controller of the tractor and trailer based on LQR is designed to follow the desired yaw rate and minimize their side-slip angle of the center of gravity (CG) at the same time. Finally, simulation tests at both low speed and high speed are conducted based on the TruckSim-Simulink program. The results show significant effects on the active steering controller on improving maneuverability at low speed and lateral stability at high speed for the articulated vehicle. The control strategy is applicable for steering not only along gentle curves but also along sharp curves.     

后轴双电机扭矩矢量控制研究

车辆的横摆响应受到转向系统、悬架系统、制动系统及驱动系统影响,传统车辆主要以转向输入进行主动控制,随着线控底盘的发展,ESC、后轮转向、扭矩矢量等技术逐步参与到车辆横摆的主动控制中;相对于ESC以制动力差产生横摆力矩,扭矩矢量可在不降低总驱动力的前提下产生横摆力矩,不会引起车辆的制动效应;通过后轴双电机扭矩矢量控制（TVC）产生主动横摆力矩,旨在改善车辆横摆响应,TVC采用前馈与反馈结合控制,基于二自由度车辆模型、目标稳态增益K及横摆角速度-速度修正因子K1建立目标横摆角速度;利用车辆模型逆函数计算横摆力矩前馈值,PID计算横摆力矩反馈值,总横摆力矩转换得到左右车轮纵向力调整量;纵向力调整量与驱动力分量叠加获得左右轮总纵向力;左右轮驱动力过大时可能会受到滑移率、电机扭矩等限制,为保证横摆力矩偏差在要求范围内,需要根据限制情况对左右轮纵向力进行调整;通过仿真验证,TVC可明显改变车辆横摆响应     

基于模糊控制的分布式电动车辆横摆力矩研究

为提高多轮分布式电驱动车辆在不同工况下的操纵稳定性,设计了一种基于直接横摆力矩控制的分层控制策略。上层以横摆角速度和质心侧偏角为控制变量,采用模糊控制进行目标运动状态跟踪,决策出所需要的横摆力矩。下层按设计的规则进行转矩分配。应用TruckSim和Matlab/Simulink建立车辆和控制器模型,分别在高、低附着等工况下进行联合仿真。仿真结果表明,设计的模糊控制方法能对车辆目标状态进行良好跟踪,相较于无控制状态能够提高车辆的操纵稳定性。     

非匹配扰动干扰下的无人直升机轨迹跟踪控制

针对小型无人直升机在飞行过程中容易受到非匹配扰动影响的特点,本文设计了一种基于新型滑模控制方法的轨迹跟踪控制器.首先,建立了无人直升机系统的非线性数学模型,并对该模型进行近似反馈线性化处理,同时将模型分为位置和偏航两个子系统;然后,利用扩展扰动观测器对复合扰动以及非匹配扰动的各阶导数的估计值,设计新型时变滑模面,得到滑模控制律,并给出了控制系统的稳定性分析;最后,仿真结果验证了控制方法的有效性和优越性.该新型滑模控制方法的优越性主要体现在:对非匹配扰动具有较强的鲁棒性,以及能有效地抑制抖振现象.     

载人潜水器的干扰特性分析与自适应滑模控制

针对在实际运行中会受到未知外部环境干扰和模型不确定性等因素影响的蛟龙号载人潜水器系统,本文设计了一种基于干扰特性指标的新型自适应滑模控制方法,实现对有益干扰的利用和有害干扰的补偿.首先,文章给出载人潜水器系统的运动学和动力学模型;然后,本文设计非线性干扰观测器估计系统所受的集总扰动,并提出一种扇形区域干扰特性指标,用于判断干扰对系统的影响;其次,文章设计一种基于干扰特性指标的自适应滑模控制方法,并且根据李雅普诺夫理论进行严格的稳定性分析;最后,通过数值仿真,验证所设计的滑模控制方法的优越性.其优越性主要体现在:不仅能够有效缓解抖振现象,并且避免控制增益高估的问题.     

基于改进型非线性干扰观测器的爬壁机器人轨迹跟踪

针对爬壁机器人建模不准确及容易受外部扰动的影响造成位置及姿态误差的问题,提出了一种基于改进型非线性干扰观测器的轨迹跟踪控制方案.首先通过反演控制设计了一个运动学控制器为机器人动力学控制提供参考质心速度与角速度.其次应用改进型非线性扰动观测器作为前馈控制对建模误差及外部扰动进行估计,并保证扰动误差以指数形式收敛.最后针对引入干扰观测器的动力学模型设计了滑模控制器.该方案对外界干扰进行了快速补偿,并通过Lyapunov定理证明了其稳定性.仿真结果表明该控制方法对于克服建模误差及外界干扰具有较好的效果.