Direct yaw moment control and power consumption of in-wheel motor vehicle in steady-state turning

Driving force distribution control is one of the characteristic performance aspects of in-wheel motor vehicles and various methods have been developed to control direct yaw moment while turning. However, while these controls significantly enhance vehicle dynamic performance, the additional power required to control vehicle motion still remains to be clarified. This paper constructed new formulae of the mechanism by which direct yaw moment alters the cornering resistance and mechanical power of all wheels based on a simple bicycle model, including the electric loss of the motors and the inverters. These formulation results were validated by an actual test vehicle equipped with in-wheel motors in steady-state turning. The validated theory was also applied to a comparison of several different driving force distribution mechanisms from the standpoint of innate mechanical power.     

Interaction of vehicle and steering system regarding on-centre handling

For the on-centre handling behaviour of vehicles the steering system is absolutely important. To investigate the interaction of the vehicle and steering system a validated, especially tailored simulation model was developed. Some meaningful vehicle and steering system parameters are altered to show the influence on steering wheel torque, steering feel and understeer. The results underline the importance of an accurate steering system model. Identified measures to improve the centre feel and steering response were a stiffer torsion bar, a higher cornering stiffness or a lower overall steering ratio. The steering response, however, suffers when the centre feel is improved by a higher trail. The steering rack friction reduces mainly the steering response while the steering column friction decreases the centre feel whereas a stiffer torsion bar lessens the understeer tendency.     

汽车操纵稳定性与前轮摆振的非线性仿真分析

以某轿车为例,建立3自由度整车系统动力学模型,利用常微分方程稳定性理论和数值仿真计算,详细研究整车的稳态转向特性和系统失稳后的前轮摆振特性。阐明汽车的操纵稳定性与前轮摆振特性同属汽车整车稳定性问题,前者是负刚度系统,后者是负阻尼系统。在一定的参数组合下,具有不同转向特性的汽车都或多或少地存在摆振现象,这与实际情况相符,建议适当增加转向系阻尼和刚度以减小甚至消除摆振的发生。     

车辆动力学控制的模拟

本文用模拟方法研究了车辆动力学控制系统。采用闭环的横摆角速度及车辆侧偏角控制，用它们之间的相平面分析确定控制策略。这一控制集成了基于滑移率控制的ＡＢＳ系统，实施简单，鲁棒性强，模拟结果显示该系统能有效地改善车辆的动力学性能。     

Comparing rear wheel steering and rear active differential approaches to vehicle yaw control

A comparison between two different approaches to vehicle stability control is carried out, employing a robust non-parametric technique in the controller design. In particular, an enhanced internal model control strategy, together with a feedforward action and a suitably generated reference map, is employed for the control of a vehicle equipped either with a rear wheel steering (RWS) system or with a rear active differential (RAD) device. The uncertainty arising from the wide range of operating conditions is described by an additive model set employed in the controller design. Extensive steady state and transient tests simulated with an accurate 14 degrees of freedom nonlinear model of the considered vehicle show that both systems are able to improve handling and safety in normal driving conditions. RAD devices can make the vehicle reach higher lateral acceleration values but they achieve only slight stability improvements against oversteer. On the other hand, 4WS systems can greatly improve both vehicle safety and manoeuvrability in all driving situations, making this device an interesting and powerful stability system.     

基于自适应模糊PI的汽车直接摆力矩控制研究

针对汽车直接横摆力矩控制,论文研究了基于自适应模糊PI的控制方法。设计了基于自适应模糊PI的附加横摆力矩决策控制器和基于规则分配的制动力分配器。横摆力矩决策控制器根据汽车横摆角速度期望值和车辆状态决策出所需的附加横摆力矩,通过规则制动力分配方法进行主动差动制动实现,并采用Matlab/Simulink与CarSim联合仿真对控制方法进行仿真试验验证。结果表明:基于自适应模糊PI的横摆力矩控制方法相对于未控制能够使汽车较好地跟踪期望,有效提高汽车操纵稳定性。     

车辆动力学稳定性控制的理论研究

本文着重探讨了车辆动力学稳定性控制的基本原理,探讨逻辑与控制算法,并在汽车驾驶模拟器所提供的虚拟驾驶环境下进行了试验验证,取得了良好的控制效果。     

基于 MPC 的分布式驱动越野车辆原地转向控制研究

针对轮毂电机分布式驱动越野车辆在狭小空间快速机动的需求,设计了一种分层结构的原地转向控制策略。基于动力学原理分析了各轮载荷、附着条件对原地转向横摆速度的影响机理,并搭建原地转向运动学模型,上层采用模型预测控制算法设计原地转向理想轨迹以及期望的横摆角速度,开发基于PI滑模控制的横摆运动跟踪算法,通过补偿转向横摆力矩以提高方向角控制的鲁棒性和稳定性,下层以最优轮胎利用率为目标,设计二次规划算法优化分配各轮附加横摆力矩。dSPACE硬件在环测试结果表明,所提出的控制算法可在保证稳定性的前提下实现原地转向,大幅提高了车辆的转向机动性,在方向盘动态输入仿真中,车辆最大转弯半径为0.157 m,转向中心的最大偏移量为3.610 m;同时,驾驶员能对转向过程进行闭环控制,实现了原地转向过程中横摆速度的实时调节。     

Rear wheel torque vectoring model predictive control with velocity regulation for electric vehicles

In this paper we propose a constrained optimal control architecture for combined velocity, yaw and sideslip regulation for stabilisation of the vehicle near the limit of lateral acceleration using the rear axle electric torque vectoring configuration of an electric vehicle. A nonlinear vehicle and tyre model are used to find reference steady-state cornering conditions and design two model predictive control (MPC) strategies of different levels of fidelity: one that uses a linearised version of the full vehicle model with the rear wheels' torques as the input, and another one that neglects the wheel dynamics and uses the rear wheels' slips as the input instead. After analysing the relative trade-offs between performance and computational effort, we compare the two MPC strategies against each other and against an unconstrained optimal control strategy in Simulink and Carsim environment.     

Nonlinear PI front and rear steering control in four wheel steering vehicles

Vehicle steering dynamics show resonances, which depend on the longitudinal speed, unstable equilibrium points and limited stability regions depending on the constant steering wheel angle, longitudinal speed and car parameters.

The main contribution of this paper is to show that a combined decentralized proportional active front steering control and proportional-integral active rear steering control from the yaw rate tracking error can assign the eigenvalues of the linearised single track steering dynamics, without lateral speed measurements, using a standard single track car model with nonlinear tire characteristics and a non-linear first-order reference model for the yaw rate dynamics driven by the driver steering wheel input. By choosing a suitable nonlinear reference model it is shown that the responses to driver step inputs tend to zero (or reduced) lateral speed for any value of longitudinal speed: in this case the resulting controlled vehicle static gain from driver input to yaw rate differs from the uncontrolled one at higher speed. The closed loop system shows the advantages of both active front and rear steering control: higher controllability, enlarged bandwidth for the yaw rate dynamics, suppressed resonances, new stable cornering manoeuvres, enlarged stability regions, reduced lateral speed and improved manoeuvrability; in addition comfort is improved since the phase lag between lateral acceleration and yaw rate is reduced.

For the designed control law a robustness analysis is presented with respect to system failures, driver step inputs and critical car parameters such as mass, moment of inertia and front and rear cornering stiffness coefficients. Several simulations are carried out on a higher order experimentally validated nonlinear dynamical model to confirm the analysis and to explore the robustness with respect to unmodelled dynamics.     

斜桩在斜塘河大桥中的应用

该文介绍了斜塘河大桥施工中57m长Ф800PHC管桩在没有专业打桩船的情况下,通过在600t级驳船上临时配装DM100德马克柴油锤和改造船前“龙口”,施打7:1斜率的斜桩。并通过实例对打桩中遇到的问题和处理办法进行了阐述。     

驾驶员PO预瞄模型参数的时域辨识

本文通过斜坡响应不变法实现离荼到连续传递函数间的转换，运用Ｍａｒｑｕａｒｄｔ阻尼最小二乘法辨识驾驶员ＰＯ预瞄模型的物理参数。辨识结果中，当信噪比为２０ｄＢ、４ｄＢ时，最大偏差分别为１．６％及１０％，从而表明斜坡响应不变法具有很高的辨识精度，且因采用阻尼最小二乘法致使物理参数识精度进一步提高。     

Development of a generalised equivalent estimation approach for multi-axle vehicle handling dynamics

This paper devotes analytical effort in developing the 2M equivalent approach to analyse both the effect of vehicle body roll and n-axle handling on vehicle dynamics. The 1M equivalent vehicle 2DOF equation including an equivalent roll effect was derived from the conventional two-axle 3DOF vehicle model. And the 1M equivalent dynamics concepts were calculated to evaluate the steady-state steering, frequency characteristics, and root locus of the two-axle vehicle with only the effect of body roll. This 1M equivalent approach is extended to a three-axle 3DOF model to derive similar 1M equivalent mathematical identities including an equivalent roll effect. The 1M equivalent wheelbases and stability factor with the effect of the third axle or body roll, and 2M equivalent wheelbase and stability factor including both the effect of body roll and the third-axle handling were derived to evaluate the steady-state steering, frequency characteristics, and root locus of the three-axle vehicle. By using the recursive method, the generalised 1M equivalent wheelbase and stability factor with the effect of n-axle handling and 2M equivalent generalised wheelbase and stability factor including both the effect of body roll and n-axle handling were derived to evaluate the steady-state steering, frequency characteristics, and root locus of the n-axle vehicle. The 2M equivalent approach and developed generalised mathematical handling concepts were validated to be useful and could serve as an important tool for estimating both the effect of vehicle body roll and n-axle handling on multi-axle vehicle dynamics.     

主动前轮转向客车的操纵稳定性仿真分析

建立某大型客车的含侧向、横摆及侧倾三自由度动力学模型,通过方向盘角阶跃转向仿真结果和试验数据的比较,验证了仿真分析的准确性。采用横摆角速度跟踪主动前轮转向控制策略,结合比例积分控制方法,在考虑作动器动态特性和前轮转角饱和特性的基础上,对主动前轮转向控制前后的车辆进行直线行驶下的侧向风扰动和湿滑路面急转弯情况下的仿真对比分析。结果表明,主动前轮转向控制后的车辆其操纵稳定性和行车安全性都有较大的提高。