Lateral Stability Improvement of Car-Trailer Systems Using Active Trailer Braking Control

An active trailer braking controller to improve the lateral stability of car-trailer systems is presented. The special and complex structures of these types of vehicles exhibit unique unstable motion behavior, such as the trailer swing, jack-knifing and rollover. These unstable motion modes may lead to fatal accidents. The effects of passive mechanical parameters on the stability of car-trailer systems have been thoroughly investigated. Some of the passive parameters, such as the center of gravity of the trailer, may be drastically varied during various operating conditions. Even for an optimal design of a car-trailer system, based on a specific passive parameter set, the lateral stability cannot be guaranteed. In order to improve the lateral stability of car-trailer systems, an active trailer braking controller is designed using the Linear Quadratic Regular （LQR） technique. To derive the controller, a vehicle model with 3 Degrees Of Freedom （DOF） is developed to represent the car-trailer system. A single lane-change maneuver has been simulated to examine the performance of the controller and the numerical results are compared with those of the baseline design. The benchmark investigation indicates that the optimal controller based on the LQR technique can effectively improve the high-speed lateral stability of the car-trailer system.

Stability Analysis on Speed Control System of Autonomous Underwater Vehicle

The stability of the motion control system is one of the decisive factors of the control quality for Autonomous Underwater Vehicle（AUV）.The divergence of control,which the unstable system may be brought about,is fatal to the operation of AUV.The stability analysis of the PD and S-surface speed controllers based on the Lyapunov＇s direct method is proposed in this paper.After decoupling the six degree-of-freedom（DOF）motions of the AUV,the axial dynamic behavior is discussed and the condition is deduced,in which the parameters selection within stability domain can guarantee the system asymptotically stable.The experimental results in a tank and on the sea have successfully verified the algorithm reliability,which can be served as a good reference for analyzing other AUV nonlinear control systems.

A Hybrid Approach to Modeling and Control of Vehicle Height for Electronically Controlled Air Suspension

The control problems associated with vehicle height adjustment of electronically controlled air suspension （ECAS） still pose theoretical challenges for researchers, which manifest themselves in the publications on this subject over the last years. This paper deals with modeling and control of a vehicle height adjustment system for ECAS, which is an example of a hybrid dynamical system due to the coexistence and coupling of continuous variables and discrete events. A mixed logical dynamical （MLD） modeling approach is chosen for capturing enough details of the vehicle height adjustment process. The hybrid dynamic model is constructed on the basis of some assumptions and piecewise linear approximation for components nonlinearities. Then, the on-off statuses of solenoid valves and the piecewise approximation process are described by propositional logic, and the hybrid system is transformed into the set of linear mixed-integer equalities and inequalities, denoted as MLD model, automatically by HYSDEL. Using this model, a hybrid model predictive controller （HMPC） is tuned based on online mixed-integer quadratic optimization （MIQP）. Two different scenarios are considered in the simulation, whose results verify the height adjustment effectiveness of the proposed approach. Explicit solutions of the controller are computed to control the vehicle height adjustment system in realtime using an offline multi-parametric programming technology （MPT）, thus convert the controller into an equivalent explicit piecewise affine form. Finally, bench experiments for vehicle height lifting, holding and lowering procedures are conducted, which demonstrate that the HMPC can adjust the vehicle height by controlling the on-off statuses of solenoid valves directly. This research proposes a new modeling and control method for vehicle height adjustment of ECAS, which leads to a closed-loop system with favorable dynamical properties.

A Simplified Sliding Mode Controlled Electronic Differential for an Electric Vehicle with Two Independent Wheel Drives

This paper presents a simple sliding mode control strategy used for an electronic differential system for electric vehicle with two independent wheel drives. When a vehicle drives along a curved road lane, the speed of the inner wheel has to be different from that of the outer wheel in order to prevent the vehicle from vibrating and travelling an unsteady path. Because each wheel of this electrical vehicle has independent driving force, an electrical differential system is required to replace a gear differential system. However, it is difficult to analyse the nonlinear behaviour of the differential system in relation to the speed and steering angle, as well as vehicle structure. The proposed propulsion system consists of two permanent magnet synchronous machines that ensure the drive of the two back driving wheels. The proposed control structure called independent machines for speed control allows the achievement of an electronic differential which ensures the control of the vehicle behaviour on the road. It also allows to control, independently, every driving wheel to turn at different speeds in any curve. Analysis and simulation results of the proposed system are presented in this paper.

A New Coordinated Fuzzy-PID Controller for Power System Considering Electric Vehicles

With penetration growing of renewable energy sources which integrated into power system have caused problems on grid stability. Electric Vehicles (EV) are one of the renewable energy sources that can bring significant impacts to power system during their charging and discharging operations. This article established a model of single machine infinite bus (SMIB) power system considering EV as a case study of load disturbance for power system oscillation. The objective of this research is to enhance stability and overcome the drawbacks of traditional control algorithms such as power system stabilizer (PSS), PID controller and fuzzy logic controller (FLC). The implementation’s effect of FLC parallel with PID controller (Fuzzy-PID) has been shown in this paper. The speed deviation (?ω) and electrical power (Pe) are the important factors to be taken into consideration without EV (only change in mechanical torque), EV with change in the mechanical torque and sudden plug-in EV. The obtained result by nonlinear simulation using Matlab/Simulink of a SMIB power system with EV has shown the effectiveness of using (Fuzzy-PID) against all disturbances.

Hopf Bifurcation Analysis and Control for Electrical System of Military Vehicle

Electrical system of military vehicle is a typical parameterized nonlinear system where complicated bifurcations may exist and threaten its safe and stable operation. An algebraic criterion for Hopf bifurcation is presented briefly and applied to find Hopf bifurcation point of the electrical system with automatic voltage regulator(AVR) dynamics in military vehicle. Hopf bifurcation controllers are designed for this electrical system by using wash-out filter,linear feedback,nonlinear feedback and their combination. The linear feedback control makes the system bring Hopf bifurcation at preferable parameter,the nonlinear feedback control modifies the type of the bifurcation,and the wash-out filter enhances the system damping,thus,the Hopf bifurcation is eliminated and the electrical system stability is ensured. Simulation results show the controller's validity.

Development of a Low-cost Hardware-in-the-loop Simulation System as a Test Bench for Anti-lock Braking System

Nowadays validation of anti-lock braking systems（ABS） relies mainly on a large amount of road tests.An alternative means with higher efficiency is employing the hardware-in-the-loop simulation（HILS） system to substitute part of road tests for designing,testing,and tuning electronic control units（ECUs） of ABS.Most HILS systems for ABS use expensive digital signal processor hardware and special purpose software,and some fail-safe functions with regard to wheel speeds cannot be evaluated since artificial wheel speed signals are usually provided.In this paper,a low-cost ABS HILS test bench is developed and used for validating the anti-lock braking performance and tuning control parameters of ABS controllers.Another important merit of the proposed test bench is that it can comprehensively evaluate the fail-safe functions with regard to wheel speed signals since real tone rings and sensors are integrated in the bench.A 5-DOF vehicle model with consideration of longitudinal load transfer is used to calculate tire forces,wheel speeds and vehicle speed.Each of the four real-time wheel speed signal generators consists of a servo motor plus a ring gear,which has sufficient dynamic response ability to emulate the rapid changes of the wheel speeds under strict braking conditions of very slippery roads.The simulation of braking tests under different road adhesion coefficients using the HILS test bench is run,and results show that it can evaluate the anti-lock braking performance of ABS and partly the fail-safe functions.This HILS system can also be used in such applications as durability test,benchmarking and comparison between different ECUs.The test bench developed not only has a relatively low cost,but also can be used to validate the wheel speed-related ECU design and all its fail-safe functions,and a rapid testing and proving platform with a high efficiency for research and development of the automotive ABS is therefore provided.

Sensor fault-tolerant observer applied in UAV anti-skid braking control under control input constraint

This paper proposes a method for addressing the problem of sensor fault-tolerant control (FTC) for anti-skid braking systems (ABSs). When the wheel velocity sensor of the ABS for unmanned aerial vehicles (UAVs) becomes faulty, wheel velocity failure and feedback instability may occur. Firstly, a fault diagnosis and isolation (FDI) method based on a sliding mode observer approach is introduced to detect and isolate the fault of the sensor. When the wheel velocity sensor is in healthy conditions, the observer works in a diagnosis mode. If faults occur in the sensor, it acts as a wheel velocity estimator. Secondly, an FTC strategy, adopting a feedback compensation structure, is designed with input control constraints. In addition, based on the FDI result, a terminal sliding mode (TSM) controller is designed to guarantee that slip-ratio tracks its appropriate reference values in situations where runways change conditions during landing. The control system switches automatically from control using a wheel velocity sensor to sensorless control mode, so the observer-based FTC scheme is established. It is logical that the ABS keeps observed-state and remains stable when the wheel velocity sensor is broken and during external disturbance. Finally, simulation results show the effectiveness of the proposed method. © 1990-2011 Beijing Institute of Aerospace Information.

Vehicle path tracking by integrated chassis control

The control problem of trajectory based path following for passenger vehicles is studied. Comprehensive nonlinear vehicle model is utilized for simulation vehicle response during various maneuvers in MATLAB/Simulink. In order to follow desired path, a driver model is developed to enhance closed loop driver/vehicle model. Then, linear quadratic regulator(LQR) controller is developed which regulates direct yaw moment and corrective steering angle on wheels. Particle swam optimization(PSO) method is utilized to optimize the LQR controller for various dynamic conditions. Simulation results indicate that, over various maneuvers, side slip angle and lateral acceleration can be reduced by 10% and 15%, respectively, which sustain the vehicle stable. Also, anti-lock brake system is designed for longitudinal dynamics of vehicle to achieve desired slip during braking and accelerating. Proposed comprehensive controller demonstrates that vehicle steerability can increase by about 15% during severe braking by preventing wheel from locking and reducing stopping distance.

Stabilization of Uncertain Systems With Markovian Modes of Time Delay and Quantization Density

This work studies the stabilization of a class of control systems that use communication networks as signal transmission medium. The lateral motion of independently actuated four-wheel vehicle is modeled as an uncertain-linear system. Time delay and quantization density are modeled as Markov chains.The networked control systems(NCSs) with plants being lateral motion are first transformed to switched linear systems with uncertain parameters. Sufficient and necessary conditions for the stochastic stability of closed-loop networked control systems are then established. By solving the matrix inequalities, this work presents an output-feedback controller that depends on the modes of time delay and quantization density. The controller performance is illustrated via a vehicular lateral motion system.

Scheme for the Balance Between Stability and Maneuverability of Hypersonic Vehicle

Since the aerodynamic center moving backward sharply in hypersonic flight,the stability margin of the hypersonic vehicle increases largely while the maneuverability decreases.We proposed a novel method to solve this contradiction.We used relaxed static stability(RSS)to improve the maneuverability in hypersonic flight,and designed the stability augmentation system(SAS)to ensure the stability in subsonic flight.Therefore,the relationship between static stability and maneuverability was quantitatively analyzed in the first step,and the numerical value of RSS was obtained on the premise of good maneuverability.Secondly,the relationship between static stability and aerodynamic parameters was quantitatively analyzed.We properly adjusted aerodynamic parameters based on the quantitative relationship to achieve the specific static stability set in the first step,and therefore provided the engineering realization methods.The vehicle will be statically unstable in subsonic flight with the specific static stability.Lastly,SAS was needed to ensure the stability of the vehicle in subsonic flight.Simulation studies were conducted by comparing the linear SAS to the nonlinear SAS,and the results showed that the nonlinear dynamicinversion controller can synthesize with proportional-integrall-derivative(PID)controller robustly and stabilize the hypersonic vehicle.

On String Stable Control of Platoon of Automated Vehicles with Predecessor-successor Information Framework

For the constant distance spacing policy,the existing researches of the string stability focus on the single-predecessor information framework（SPIF） and predecessor-successor information framework（PSIF）.The research results demonstrated that the string stability could not be guaranteed with the SPIF,and then the PSIF was proposed to resolve this string instability.But the issue,whether the string stability can be guaranteed when applying the PSIF,is still controversial.Meanwhile,most of the previous researches on the string stability were conducted without consideration of the parasitic time delays and lags.In this paper,the practical longitudinal vehicle dynamics model is built with consideration of the parasitic time delays and lags existing in the actuators,sensors or the communication systems.Secondly,the detailed theoretical analysis of string stability in frequency domain is conducted to demonstrate that the classical linear control laws can not ensure the string stability when applying both the symmetrical PSIF（SPSIF） and asymmetrical PSIF（APSIF）.Thirdly,a control law,which adds the position and velocity information of the leading vehicle,is proposed to guarantee string stability for small/medium platoon,and the other control law,which adds the acceleration information of the controlled vehicle,is proposed to guarantee string stability for large platoon as well as small/medium platoon.Finally,the comparative simulation is conducted to confirm the conducted analysis and the proposed control laws.The conducted research completes the means to analyze the string stability in frequency domain,provides the parameters＇ reference for the design and implementation of the practical automatic following controllers,and improves the reliability and stability of the platoon of automatic vehicles.

面向线控制动车辆单轮制动失效的稳定性控制

基于线控制动系统四轮可独立控制的特点,提出一种协同线控转向与线控制动的制动力实时分配的控制方法。该方法根据三轮富余制动力能否补偿失效轮损失制动力,按制动强度分为轻度、中度和重度制动3种工况,针对重度制动工况下制动力补偿不足问题,基于积分滑模控制方法设计前轮主动转向器,综合考虑单轮制动失效时各轮垂直载荷的变化和前轮转角介入后轮胎力的耦合,采用序列二次规划算法(sequental quadratic programming,SQP),实时分配剩余三轮制动力。仿真结果表明:在不同制动强度及不同轮制动失效下所提控制方法相较于无控制,横向跑偏分别减少了89.98%、91.90%、96.96%、89.62%,制动强度至少达到正常制动时的97.5%。因此,该控制方法在保证横向稳定性的同时最大限度地满足驾驶员的制动期望,有效抑制因单轮制动失效导致的车辆跑偏甩尾等问题。

考虑多维非线性扰动的电子助力制动系统自适应压力控制

针对电子助力制动系统(EBBS)面临的机-电-液多维非线性扰动问题,提出了一种自适应压力控制策略。外层液压控制器引入自适应径向基函数神经网络和鲁棒滑模理论克服液压时变不确定性,中间层位置控制器采用Karnopp摩擦前馈补偿和滑模控制应对传动机构非线性摩擦阻碍,内层电流控制器通过李雅普诺夫理论解决电机电磁特性耦合问题。仿真和硬件在环试验结果表明,设计的压力控制策略能够在多种工况中将EBBS主动制动稳态压力跟随误差维持在0.15MPa之内。

集成式电液制动系统自适应压力控制

针对集成式电液制动系统(integrated electro-hydraulic brake system,IEHB)存在的复杂液压非线性特性和时变摩擦干扰,提出一种自适应压力控制策略。外环压力控制器引入液压特性的动态线性化模型并基于滑模观测器对模型参数实时辨识实现对非线性液压特性的自适应。内环伺服控制器采用基于压力的连续摩擦补偿和反步动态面控制应对传动机构摩擦阻碍。硬件在环实验结果表明,与现有的先进级联压力控制相比,设计的压力控制策略在多种工况下均表现出更高的控制精度和鲁棒性,并显著提升了IEHB在不同液压回路结构下的压力控制效果。

参数扰动对一种先前的车辆制动控制和防护方法的影响

探究了作者早先提出的一种车辆制动控制防护方法在参数扰动下的防护效果。用MADYMO虚拟仿真软件,对4种形状的典型车头开展了仿真,分析了以下参数:人体头部与车体首次接触时间、制动系统协调时间、路面附着因数:扰动时,对该制动控制防护方法的影响。结果显示:在人体头部与车体首次接触时间时为80~100 ms时,对加权伤害费用(WIC)降幅的影响最显著,但不同车型下的参数敏感性排序存在差异。在路面附着因数扰动为0.45~0.80时,人车碰撞损伤未增加;但地面所致WIC降幅均大于零,可有效降低人地碰撞损伤。在制动系统协调时间参数扰动区间为80~350 ms时,该车辆制动控制防护方法仍然保持有效。

基于动态模拟技术的混动车辆发动机电控单元检测系统设计

电控单元是混动车辆发动机中的重要组成部分,对于发动机以及混动车辆的行驶性能产生直接影响,为保证电控单元的运行正常,利用动态模拟技术,优化设计了混动车辆发动机电控单元检测系统;改装温度、转速等传感器设备以及信号处理器设备,调整系统电路的连接方式,实现硬件系统的优化;利用动态模拟技术模拟混动车辆发动机电控过程,结合不同故障类型下电控单元的运行特征,设置系统的检测标准;采集电控单元输出信号,从时域和频域两个方面提取信号特征,最终通过特征匹配确定电控单元状态、故障类型以及故障位置,实现系统的电控单元检测功能;综合混动车辆发动机的3种运行场景,通过系统测试实验得出结论:与传统检测系统相比,优化设计系统的漏检率和误检率分别降低了2.59%和2.05%,由此证明优化设计系统具有良好的检测功能。

构网型变流器:物理本质与特征

全球能源产业变革促进了电力系统电力电子化转型,以新能源为主体的电力电子化电力系统中同步机占比低,系统呈现低惯量、弱阻尼特征,引发了一系列运行问题。构网型变流器本质为电压源,能够主动构建电压频率,为系统提供惯量支撑,有利于改善系统稳定性,是提高新能源主动支撑能力的有效手段,近年来成为研究热点。该文从电力电子化电力系统的运行问题出发,梳理了下垂控制、虚拟同步机控制等典型构网型控制策略的实现原理及内在联系,建立构网型控制策略的统一数学模型;通过类比稳态条件下同步机与构网型变流器的电压频率构建原理,揭示了构网型变流器的物理本质,从电压频率构建、惯量阻尼支撑、同步机制等角度解释了构网型变流器的内涵与特性,可为构网型变流器的稳定与控制提供理论参考。

集成式电子液压线控制动系统建模与仿真

为了解决线控制动系统模型复杂、仿真困难等问题,文章针对一款常见的集成式电子液压线控制动(integrated electronic hydraulic brake,I-EHB)系统,推导其数学模型并进行仿真分析;在MATLAB/Simulink中搭建线控制动系统的仿真模型,设计比例积分微分(proportion integration differentiation,PID)制动控制器,实现对集成式电子液压线控制动系统的压力控制。仿真结果表明:该线控制动系统在PID控制器作用下实际输出压力值能够较好地跟随理想压力值,可以提供较好的制动效果。该文的研究对于线控底盘的开发具有积极推动作用。

朔黄铁路重载列车电控空气制动试验研究

重载列车的制动技术是重载运输发展的关键。针对国内朔黄铁路,对重载列车电控空气制动系统进行试验研究,比较分析有无电控空气制动系统作用下列车制动系统的性能指标。实验结果显示:电控空气制动系统性能指标达到设计要求,在缓解车钩作用力、同步列车管及制动缸压力和缩短制动距离等方面具有明显的优势,该电控空气制动系统能够保证重载长、大列车运行的安全性。