Output feedback H ∞/GH 2 preview control of active vehicle suspensions: a comparison study of LQG preview

This study concerns with multi-objective H _∞/GH ₂ preview control of active vehicle suspensions. This control scheme has two main aspects: first, it allows constrained outputs of the system to vary freely as long as they remain within their given bounds, in order that the best possible performance could be delivered. Secondly, the optimisation as well as constraint fulfilment is done for the worst-case road disturbances to cover all road types. To design a system to perform satisfactorily for a wide range of road irregularities, H _∞-norm is used wherever minimisation is required, and generalised H ₂-norm is used to care for the constraints on suspension working space. Moreover, to ensure desired stability margins for the system, pole location constraints are considered in the design. The proposed approach is evaluated on a quarter-car model and compared with the state-of-the-art preview control algorithm in the literature, namely, Linear quadratic Gaussian preview. Simulation results demonstrate the effectiveness of the proposed approach.     

一类连续切换系统的渐近稳定性

针对一类连续时变时滞切换系统,通过构造适当的Lyapunov函数,提供适当的能量函数.利用线性矩阵不等式方法,讨论系统的能量递减,证明该系统在任意切换下的稳定性.通过MATLAB数值仿真,结果表明该系统是渐近稳定的,表明该方法是有效的.     

具有输入滞后的不确定系统时滞依赖鲁棒H∞可靠控制

讨论了一类具有输入时变时滞不确定系统,研究了在执行器发生故障情况下系统全局渐进稳定的鲁棒H∞可靠控制设计的问题.首先建立了包含参数不确定、控制输入滞后、执行器故障等的系统状态模型;然后根据Lya-punov稳定性理论,推导出系统存在时滞依赖型鲁棒H∞可靠控制器应满足的矩阵不等式,并将其转化为线性矩阵不等式.数值仿真结果表明:提出的控制器设计方法具有满意的控制性能要求.     

一类非线性不确定时滞系统鲁棒控制器的设计

利用LMI方法,针对不确定时滞系统的鲁棒模糊控制器设计及稳定性,提出了基于T—S的模糊模型,得到了使系统渐近稳定且具有H∞-扰动抑制度的模糊状态反馈控制器存在的充分条件,此充分条件以线性矩阵不等式的形式给出,因而具有数值易解性．     

Constrained H∞ control of urban transportation network

Because transportation systems involve massive complex human activities, there exist substantial unpredictable uncertainties of the traffic demands. This paper aims at presenting an H_∞ control method for transportation network that can enhance the tolerance of the system due to these uncertainties. In particular, the store‐and‐forward approach is applied to model the system into a linear form. Then, a detailed controllability analysis shows that the system is not completely controllable by taking the constraints on the green times into account. This makes difficult to apply directly the H_∞ method. To overcome this difficulty, this paper isolates the fully controllable part of the transportation system, and the problem of disturbance attenuation is then solved by means of a convex optimization with linear matrix inequality. Finally, the simulation of a large‐scale hypothetical network is carried out to illustrate the results. Copyright © 2014 John Wiley & Sons, Ltd.     

Vehicle dynamics and road curvature estimation for lane departure warning system using robust fuzzy observers: experimental validation

This paper describes a new approach to estimate vehicle dynamics and the road curvature in order to detect vehicle lane departures. This method has been evaluated through an experimental set-up using a real test vehicle equipped with the RT2500 inertial measurement unit. Based on a robust unknown input fuzzy observer, the road curvature is estimated and compared to the vehicle trajectory curvature. The difference between the two curvatures is used by the proposed lane departure detection algorithm as the first driving risk indicator. To reduce false alarms and take into account driver corrections, a second driving risk indicator based on the steering dynamics is considered. The vehicle nonlinear model is deduced from the vehicle lateral dynamics and road geometry and then represented by an uncertain Takagi–Sugeno fuzzy model. Taking into account the unmeasured variables, an unknown input fuzzy observer is proposed. Synthesis conditions of the proposed fuzzy observer are formulated in terms of linear matrix inequalities using the Lyapunov method.     

Vehicle dynamic stability improvements through gain-scheduled steering and braking control

This paper is concerned with the synthesis of a robust gain-scheduled ?_∞ MIMO vehicle dynamic stability controller (VDSC) involving both steering and rear braking actuators. This VDSC aims at improving automotive vehicle yaw stability and lateral performances. The aim of this work is to provide a methodology to synthesise such a controller while taking into account the braking actuator limitations and use the steering actuator only if it is necessary. These objectives are treated in an original way by the synthesis of a parameter-dependent controller built in the LPV framework and by the solution of an LMI problem. The proposed solution is coupled with a local ABS strategy to guarantee slip stability and make the solution complete. Nonlinear time and frequency domain simulations on a complex full vehicle model (which has been validated on a real car), subject to critical driving situations, show the efficiency and robustness of the proposed solution.     

Vehicle dynamic estimation with road bank angle consideration for rollover detection: theoretical and experimental studies

This article describes a method of vehicle dynamics estimation for impending rollover detection. This method is evaluated via a professional vehicle dynamics software and then through experimental results using a real test vehicle equipped with an inertial measurement unit. The vehicle dynamic states are estimated in the 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 the rollover detection, a new method is proposed in order to compute the time-to-rollover using the load transfer ratio. The used nonlinear model is deduced from the vehicle lateral dynamics and is represented by a Takagi–Sugeno (TS) fuzzy model. This representation is used in order to take into account the nonlinearities of lateral cornering forces. The proposed TS observer is designed with unmeasurable premise variables in order to consider the non-availability of the slip angles measurement. Simulation results show that the proposed observer and rollover detection method exhibit good efficiency.     

时延网络控制系统的保性能控制研究

针对网络控制系统中存在的不确定时延,在传感器采用时间驱动,执行器与控制器采用事件驱动、时延小于一个采样周期的条件下,将网络控制系统建模为一类具有不确定性的线性离散系统并且其标称模型可控。围绕该标称模型,利用Lyapunov方法,基于相应的LMI可行解,给出网络控制系统保性能控制律的设计方法。通过仿真证明了该方法的有效性。