Coordinated control of ESC and AFS with adaptive algorithms

This paper presents a coordinated control of electronic stability control (ESC) and active front steering (AFS) with adaptive algorithms for yaw moment distribution in integrated chassis control (ICC). In order to distribute a control yaw moment into control tire forcres of ESC and AFS, and to coordinate the relative usage of ESC to AFS, a LMS/Newton algorithm (LMSN) is adopted. To make the control tire forces zero in applying LMS and LMSN, the zero-attracting mechanism is adopted. Simulations on vehicle simulation software, CarSim®, show that the proposed algorithm is effective for yaw moment distribution in integrated chassis control.     

Fault-tolerant yaw moment control with steer — and brake-by-wire devices

This paper presents an fault-tolerant yaw moment control for a vehicle with steer-by-wire (SBW) and brake-by-wire (BBW) devices. SBWs and BBWs can give active front steering (AFS) and electronic stability control (ESC) functions, respectively. Due to motor-driven devices, actuator and sensor faults are inherent in SBW and BBW, and can cause a critical damage to a vehicle. Simple direct yaw moment control is adopted to design a vehicle stability controller. To cope with actuator failure, weighted pseudo-inverse based control allocation (WPCA) with variable weights is proposed in yaw moment distribution procedure. Simulations on vehicle simulation software, CarSim®, show the proposed method is effective for fail safety.     

智能汽车轨迹跟踪与横摆稳定性协同控制

为了提高四轮独立驱动智能电动汽车在变曲率弯道下的轨迹跟踪精度和横摆稳定性,提出了一种模型预测控制与直接横摆力矩控制协同的综合控制方法。建立了横纵向耦合的车辆动力学模型,采用2阶龙格库塔离散法保证了离散模型的精度,并基于简化的2自由度动力学模型推导了车辆横摆稳定性约束,设计了非线性模型预测控制器;利用直接横摆力矩控制能够改变车辆横摆角速度和航向角的特点,考虑模型预测控制器的预测状态、控制量以及跟踪误差,设计了协同控制规则。仿真结果表明,协同控制方法解决了考虑横摆稳定性约束的模型预测控制器中存在的稳定性约束与控制精度相矛盾的问题,并补偿了模型预测控制器没有可行解时对横摆稳定性的约束,同时提高了智能汽车的轨迹跟踪精度和横摆稳定性。     

Electronic stability control for electric vehicle with four in-wheel motors

The electric vehicle with four direct-driven in-wheel motors is an over actuated system. A three-level control strategy of electronic stability control (ESC) is proposed to achieve optimal torque distribution for four in-wheel motors. The first level is a gain-scheduled linear quadratic regulator which is designed to generate the desired yaw moment command for ESC. Control allocation is the second level which is used to distribute the desired longitudinal tire forces according to the yaw moment command while satisfying the driver’s intent for acceleration and deceleration. The associated weighting matrix is designed using the work load ratio at each wheel to prevent saturating the tire. The third level is slip ratio control (SRC) which is employed at each wheel to generate the desired longitudinal tire force based on a combined-slip tire model. Simulation results show that the proposed method can enhance the ESC performance for the test maneuvers. Since the tire model is often unknown for practical implementation, the effectiveness of the SRC is studied using the sine with dwell test. It is found that the SRC is not crucial for achieving performance similar to the proposed method with SRC, if the slip ratio can be maintained in the stable region using traction control system/anti-lock braking system.     

基于蚁狮算法的UKF车辆状态参数估计器

为了准确获取分布式驱动电动汽车状态参数信息,满足车辆稳定性控制系统的需求,提出一种基于蚁狮算法的无迹卡尔曼滤波状态参数估计器。针对无迹卡尔曼滤波（UKF）过程中噪声协方差矩阵的不确定性,采用蚁狮优化算法（ALO）对其进行寻优,并引入奇异值分解（SVD）的方法来维持噪声协方差矩阵的正定性,此外,基于指数加权最小二乘法对车辆侧偏刚度进行辨识并将其作为状态参数估计器输入。基于MATLAB/Simulink和CarSim联合仿真平台,建立分布式驱动电动汽车参数估计模型,分别进行双移线工况和正弦迟滞工况仿真,并基于A&D5435快速原型开发平台进行双移线工况实车试验。仿真与试验结果表明：相比于SVDUKF算法估计结果,双移线仿真工况下,基于ALO-SVDUKF算法估计得到的质心侧偏角和横摆角速度的均方根误差分别降低了55.7%、30.7%,正弦迟滞仿真工况下,均方根误差分别降低了58.1%、85.1%,且在车辆处于极限失稳状态时仍能维持较好的估计效果;双移线试验工况下,横摆角速度的估计值与实际测量值之间的均方根误差仅为0.938 4（°）·s^-1;提出的基于ALO-SVDUKF算法的分布式驱动电动汽车状态参数估计器能够有效提高质心侧偏角和横摆角速度的估计精度,可为车辆稳定性控制提供精确的状态信息。     

Vehicle Dynamic Control for In-Wheel Electric Vehicles Via Temperature Consideration of Braking Systems

?Vehicle dynamic control (VDC) systems play an important role with regard to vehicle stability and safety when turning. VDC systems prevent vehicles from spinning or slipping when cornering sharply by controlling vehicle yaw moment, which is generated by braking forces. Thus, it is important to control braking forces depending on the driving conditions of the vehicle. The required yaw moment to stabilize a vehicle is calculated through optimal control and a combination of braking forces used to generate the calculated yaw moment. However, braking forces can change due to frictional coefficients being affected by variations in temperature. This can cause vehicles to experience stability problems due an improper yaw moment being applied to the vehicle. In this paper, a brake temperature estimator based on the finite different method (FDM) was proposed with a friction coefficient estimator in order to solve this problem. The developed braking characteristic estimation model was used to develop a VDC cooperative control algorithm using hydraulic braking and the regenerative braking of an in-wheel motor. Performance simulations of the developed cooperative control algorithm were performed through cosimulation with MATLAB/Simulink and CarSim. From the simulation results, it was verified that vehicle stability was ensured despite any changes in the braking characteristics due to brake temperatures.     

Optimisation of active suspension control inputs for improved performance of active safety systems

A collocation-type control variable optimisation method is used to investigate the extent to which the fully active suspension (FAS) can be applied to improve the vehicle electronic stability control (ESC) performance and reduce the braking distance. First, the optimisation approach is applied to the scenario of vehicle stabilisation during the sine-with-dwell manoeuvre. The results are used to provide insights into different FAS control mechanisms for vehicle performance improvements related to responsiveness and yaw rate error reduction indices. The FAS control performance is compared to performances of the standard ESC system, optimal active brake system and combined FAS and ESC configuration. Second, the optimisation approach is employed to the task of FAS-based braking distance reduction for straight-line vehicle motion. Here, the scenarios of uniform and longitudinally or laterally non-uniform tyre–road friction coefficient are considered. The influences of limited anti-lock braking system (ABS) actuator bandwidth and limit-cycle ABS behaviour are also analysed. The optimisation results indicate that the FAS can provide competitive stabilisation performance and improved agility when compared to the ESC system, and that it can reduce the braking distance by up to 5% for distinctively non-uniform friction conditions.     

轻型汽车ESC国家标准研究与制定

为使汽车行业充分理解轻型汽车电子稳定性控制系统（ESC）国家标准,引导和规范ESC测试评价,文章对轻型汽车ESC全球技术法规的主要内容和特点进行系统剖析,针对ESC过度转向评价和路面摩擦因数测定开展验证试验,并探索不足转向试验方案。在ESC国家标准中明确了路面摩擦因数测定方法,并通过冰雪路面上的双移线试验和稳态圆周试验对ESC不足转向特性进行评价。轻型汽车ESC国家标准弥补了全球技术法规在不足转向评价上的不足,为我国规范与完善ESC性能测试奠定了基础。     

Novel stability control strategy for distributed drive electric vehicle based on driver operation intention

In this paper, a novel direct yaw control method based on driver operation intention for stability control of a distributed drive electric vehicle is proposed. It was discovered that the vehicle loses its stability easily under an emergency steering alignment (EA) problem. An emergent control algorithm is proposed to improve vehicle stability under such a condition. A driver operation intention recognition module is developed to identify the driving conditions. When the vehicle enters into an EA condition, the module can quickly identify it and transfer the control method from normal direct yaw control to emergency control. Two control algorithms are designed. The emergency control algorithm is applied to an EA condition while the adaptive control algorithm is applied to other conditions except the EA condition. Both simulation results and real vehicle results show that: The driver module can accurately identify driving conditions based on driver operation intention. When the vehicle enters into EA condition, the emergent control algorithm can intervene quickly, and it has proven to outperform normal direct yaw control for better stabilization of vehicles.     

Dynamics analysis of an omni-directional vehicle

In a modern society, traffic congestion is a major problem in every metropolis. To solve the problem of traffic congestion an innovative omni-directional vehicle is proposed. This research has mainly focussed on developing the comprehensive vehicle dynamics model for an omni-directional road vehicle. Then the stability of the vehicle in the yaw plane was analysed under different scenarios based on the response of the side slip angle. Finally an active steering PID controller was suggested and which, according to the results of the simulation, improved the yaw plane stability.     

基于扰动观测的客车ESC自适应神经网络滑模控制

为了提高客车电子稳定性控制系统（ESC）的控制精度,针对实际车辆系统建模中存在各种非线性扰动项以及传统滑模控制（Sliding Mode Control,SMC）中抖振较大的问题,提出一种自适应神经网络滑模控制算法。基于2自由度车辆模型,首先设计一个二阶滑模（Second-order Sliding Mode,SOSM）估计器对车辆的质心侧偏角进行估计,然后利用径向基（Radial Basis Function,RBF）神经网络对车辆系统建模中的各种非线性扰动项进行实时估计,并进行Lyapunov稳定性证明,RBF神经网络估计车辆系统建模的各种非线性扰动项可以有效减小滑模控制符号项的系数,从而减小滑模抖振水平。为了更进一步优化传统滑模控制的参数调节过程,减小滑模抖振并提高系统控制精度,再次利用RBF神经网络对传统滑模控制中的关键参数进行自适应调节。最后为了验证算法的有效性,搭建客车电控气压制动系统硬件在环试验台,在硬件在环试验台上对算法的有效性和精度进行试验验证。研究结果表明：客车ESC在自适应神经网络滑模算法的控制下,横摆角速度和质心侧偏角能够较好地跟随上理想的横摆角速度和理想质心侧偏角,横摆角速度和质心侧偏角的跟随误差降低;利用RBF神经网络估计客车建模中的各种非线性扰动项和利用RBF神经网络自适应调节传统滑模控制的关键参数,可以有效提高客车ESC的控制精度。     

Lateral handling improvement with dynamic curvature control for an independent rear wheel drive EV

The integrated longitudinal and lateral dynamic motion control is important for four wheel independent drive (4WID) electric vehicles. Under critical driving conditions, direct yaw moment control (DYC) has been proved as effective for vehicle handling stability and maneuverability by implementing optimized torque distribution of each wheel, especially with independent wheel drive electric vehicles. The intended vehicle path upon driver steering input is heavily depending on the instantaneous vehicle speed, body side slip and yaw rate of a vehicle, which can directly affect the steering effort of driver. In this paper, we propose a dynamic curvature controller (DCC) by applying a the dynamic curvature of the path, derived from vehicle dynamic state variables; yaw rate, side slip angle, and speed of a vehicle. The proposed controller, combined with DYC and wheel longitudinal slip control, is to utilize the dynamic curvature as a target control parameter for a feedback, avoiding estimating the vehicle side-slip angle. The effectiveness of the proposed controller, in view of stability and improved handling, has been validated with numerical simulations and a series of experiments during cornering engaging a disturbance torque driven by two rear independent in-wheel motors of a 4WD micro electric vehicle.     

Active approach to Electronic Stability Control for front-wheel drive in-wheel motor electric vehicles

Recently, motion control for electric vehicles has gradually gained respect in automotive society due to increased strictness of vehicle safety evaluation over time. Electronic Stability Control (ESC) is the kernel technology, which refers to two-dimensional motion stabilization. Many investigations have demonstrated that Direct Yaw-moment Control (DYC) is an effective and practical way to carry out the ESC of electric vehicles. However, based on the drive train of conventional steering, conventional approaches are using braking to achieve the DYC. This paper proposes a new ESC based on the construction of DYC. The presented approach is based on a core of individual traction control measures for propulsion wheels. This approach not only constrain the longitudinal slip, but also ensure the performance and the effectiveness of two-dimensional motion control. With a proper control, the vehicle can be maintained to a nearly neutral-steering under high speed turning. Hence, the vehicle’s dynamic stability can be enhanced under aggressive driving by yaw-moment control. Evaluation of the entire control system is performed by well-acknowledged software, which demonstrates that the vehicle’s dynamic stability can be enhanced under aggressive driving by the proposed approach.     

Robustness analysis of ESC ECU to characteristic variation of vehicle chassis components using HILS technique

The ESC system, since its introduction in the mid 90s, has greatly contributed to prevention of vehicle accidents with its capability of maintaining vehicle stability in severe driving conditions. Due to its significant advantages, many nations are now adopting regulations that mandate installation of the ESC system in all classes of passenger vehicles — from mini to luxury. Accordingly it became important to know whether an ESC ECU can yield good performance on a wide range of vehicle parameter changes. In this paper, robustness analysis was conducted to study how characteristic variation of the main chassis components affect the performance of the ESC ECU. This analysis was carried out using a HILS system built on an actual ESC ECU. The variation range of each chassis component was carefully selected considering the component’s design criteria adopted in automotive industries. Based upon the robustness analysis results, the allowable variation ranges of the chassis components for ensuring sound performance of an ESC ECU were proposed.     

An Emergency Obstacle Avoidance Control Strategy for Automated Highway Vehicles

Summary This paper presents an emergency obstacle avoidance control strategy that may be used in automated highway vehicles. In the proposed control strategy, an inverse vehicle dynamics problem is solved on the selected emergency lane-change path to find out the nominal feedforward control inputs such as the steering wheel angle and the braking force. Then the overall vehicle lateral and yaw motion is controlled additionally in the feedback path by an active yaw moment for stability augmentation as well as a corrective steering angle that is added to the nominal steering angle in order to compensate for uncertainties involved in the nominal control input computation. The proposed control strategy has been tested by an ABS Hardware-In-the-Loop Simulation (HILS) system for rapid and safe control prototyping in a lab. Simulation results with a sample emergency avoidance distance (45 m) show that the proposed control strategy may be used as a feasible obstacle avoidance strategy for automated highway vehicles.     

基于驾驶人转向意图的双电机驱动电动汽车稳定性控制策略

为了使双电机驱动电动车在车辆稳定性控制过程中能够精确解读驾驶意图,使车辆实际行驶状态与驾驶意图期望的车辆行驶状态尽可能相符合,提出一种基于驾驶人意图辨识的稳定性控制策略.利用基于支持向量机递归特征消除(SVM-RFE)得到的特征参数构建基于长短期记忆(LSTM)模型的驾驶人转向意图辨识模型;基于转向意图识别结果,以方向...     

An Emergency Obstacle Avoidance Control Strategy for Automated Highway Vehicles

Summary This paper presents an emergency obstacle avoidance control strategy that may be used in automated highway vehicles. In the proposed control strategy, an inverse vehicle dynamics problem is solved on the selected emergency lane-change path to find out the nominal feedforward control inputs such as the steering wheel angle and the braking force. Then the overall vehicle lateral and yaw motion is controlled additionally in the feedback path by an active yaw moment for stability augmentation as well as a corrective steering angle that is added to the nominal steering angle in order to compensate for uncertainties involved in the nominal control input computation. The proposed control strategy has been tested by an ABS Hardware-In-the-Loop Simulation (HILS) system for rapid and safe control prototyping in a lab. Simulation results with a sample emergency avoidance distance (45 m) show that the proposed control strategy may be used as a feasible obstacle avoidance strategy for automated highway vehicles.     

Integrated evasive manoeuvre assist for collision mitigation with oncoming vehicles

Development and deployment of steering based collision avoidance systems are made difficult due to the complexity of dealing with oncoming vehicles during the evasive manoeuvre. A method to mitigate the collision risk with oncoming vehicles during such manoeuvres is presented in this work. A point mass analysis of such a scenario is first done to determine the importance of speed for mitigating the collision risk with the oncoming vehicle. A characteristic parameter was identified, which correlates well with the need to increase or decrease speed, in order to reduce the collision risk. This finding was then verified in experiments using a Volvo XC90 test vehicle. A closed-loop longitudinal acceleration controller for collision mitigation with oncoming vehicles is then presented. The longitudinal control is combined with yaw stability control using control allocation to form an integrated controller. Simulations in CarMaker using a validated XC90 vehicle model and the proposed controller showed consistent reductions in the collision risk with the oncoming vehicle.     

基于动态门限值的分布式驱动电动汽车驱动力矩控制研究

为改善分布式驱动电动汽车高速行驶稳定性，避免频繁驱动控制操作对汽车行驶安全性的影响，提出了一种适应不同驾驶工况的参数动态门限值算法，设计了汽车附加横摆力矩滑模控制策略和驱动力矩二次规划优化分配控制策略，并进行了角阶跃输入工况和双正弦输入工况的仿真分析。结果表明，所设计的控制策略能有效控制汽车的质心侧偏角与横摆角速度，在保证汽车行驶稳定性的前提下，使质心侧偏角与理想值偏差减小了3.6%以上，轮胎附着利用率减少19.5%以上，有效地降低了轮胎附着利用率，提高了汽车的行驶安全性。     

Disturbance Observer-Based Sideslip Angle Control for Improving Cornering Characteristics of In-Wheel Motor Electric Vehicles

In this paper, a robust sideslip angle controller based on the direct yaw moment control (DYC) is proposed for in-wheel motor electric vehicles. Many studies have demonstrated that the DYC is one of the effective methods to improve vehicle maneuverability and stability. Previous approaches to achieve the DYC used differential braking and active steering system. Not only that, the conventional control systems were commonly dependent on the feedback of the yaw rate. In contrast to the traditional control schemes, however, this paper proposes a novel approach based on sideslip angle feedback without controlling the yaw rate. This is mainly because if the vehicle sideslip angle is controlled properly, the intended sideslip angle helps the vehicle to pass through the corner even at high speed. On the other hand, the vehicle may become unstable because of the too large sideslip caused by unexpected yaw disturbances and model uncertainties of time-varying parameters. From this aspect, disturbance observer (DOB) is employed to assure robust performance of the controller. The proposed controller was realized in CarSim model described actual electric vehicle and verified through computer simulations.