基于粒子群优化PID控制的高速列车主动稳定性控制研究

为研究高速列车动力学与控制系统的稳定性,采用粒子群优化PID的高速列车稳定性主动控制方法,运用SIMPACK软件建立整车动力学仿真模型,并搭建整车PID主动控制系统。利用粒子群算法优化PID控制参数,结合相应的控制策略,建立新轮无故障、磨耗轮无故障以及新轮有故障3种不同的仿真工况对其主动稳定性进行仿真分析,提出以构架横向振动位移和速度状态为反馈,在构架梁位置施加控制力的主动稳定的方案,研究在不同速度下粒子群优化PID控制系统直线运行性能的影响。仿真结果表明:粒子群优化PID主动控制明显改善车体平稳性和减小轮对轮轴的横向力,在新轮和磨耗轮工况下其轮轨系数在大部分速度下均大于无控制状态;当磨耗轮运行速度大于400km/h或者新轮单侧抗蛇行减振器运行速度大于320km/h时,粒子群优化PID控制可明显减小轮对脱轨系数。

基于强度折减法的浅埋隧道掌子面三维主动稳定性上限解析

隧道掌子面常常易发生坍塌事故,为有效评估其主动稳定性,文章构建其三维多滑块破坏模型,开展了基于强度折减法的掌子面三维主动稳定性上限分析。结合极限分析上限法,构建了安全系数的目标函数,通过非线性优化程序得到其最优上限解。通过对比分析,验证了该方法的有效性;并分析了不同参数对安全系数和破坏模式的影响规律。研究表明:安全系数FS随粘聚力c、内摩擦角φ的增加而线性增加,随地面荷载ss及重度γ的增加而减小,随超负荷比C/D的增加而非线性减小。超负荷比C/D和内摩擦角φ对主动破坏模式影响显著,而粘聚力c、地面超载ss及重度γ则影响较小;当主动破坏区域不能延伸到地表时,超负荷比C/D和地面超载ss对计算结果无影响。

一种基于发动机喘振实时模型的主动稳定性控制方法

提出了涡扇发动机喘振实时模型建立方法,该模型考虑了发动机容腔的容积动力学效应,风扇、压气机的失速区特性,燃烧室的熄火特性,同时建立了发动机进口总温畸变、总压畸变及组合畸变模型;提出了一种基于压力相关度测量的发动机主动稳定性控制技术,通过测量压气机转子叶片尖端区域的压力相关度,得到相关度值穿越阈值的次数,根据穿越阈值次数与喘振裕度值固有的特性关系,得到压气机的喘振裕度,进而通过鲁棒控制方法设计了主动稳定性控制律,并进行了仿真研究,结果表明:相比于常规控制,基于压力相关度测量主动稳定性控制可以实现发动机过渡态过程中压缩系统不进喘,明显提高了发动机过渡态的动态性能.

基于分层控制的车辆主动制动稳定性分析

为提高车辆行驶的主动安全性,引入分层控制思想。建立名义横摆角速度和名义质心侧偏角为输出的线性二自由度车辆模型。基于线性二次型调节器设计上层控制器,得到附加横摆力矩,采用差动制动原理,设计中层控制器对附加横摆力矩进行分配,根据中层控制器分配的附加横摆力矩计算滑移率增量,基于PID控制理论设计下层滑移率控制器,以控制车轮的制动压力;最后联合MATLAB/Simulink和Car Sim进行鱼钩转向和双移线转向仿真试验。结果表明,采用分层控制能够有效地提高车辆行驶的主动制动稳定性。

氯沙坦对载脂蛋白E基因缺陷小鼠氧化应激及动脉粥样硬化斑块稳定性的影响

目的观察血管紧张素Ⅱ1型受体拮抗剂氯沙坦对载脂蛋白E基因缺陷小鼠氧化应激及主动脉粥样斑块中血管平滑肌细胞、巨噬细胞数量影响,探讨氯沙坦稳定斑块的作用及可能机制。方法27只8周龄雄性载脂蛋白E基因缺陷小鼠随机等分三组:对照组、氯沙坦低剂量组[5 mg/(kg.d)]及氯沙坦高剂量组[25 mg/(kg.d)],20周后处死动物。常规生物化学法测定血清一氧化氮含量、超氧化物歧化酶活性、丙二醛及血脂水平;采用HE染色法观察小鼠主动脉粥样硬化病变形成;免疫组织化学法分析粥样斑块中血管平滑肌细胞和巨噬细胞数量。结果三组间血脂水平无显著性差异;与对照组相比,氯沙坦低、高剂量组血清一氧化氮水平和超氧化物歧化酶活性均明显升高(P<0.01)、丙二醛水平显著减低(P<0.05和P<0.01),且氯沙坦低剂量和高剂量组间也有明显差异(P<0.01);氯沙坦干预后动脉粥样斑块纤维帽厚,脂质核心小;氯沙坦治疗组斑块中平滑肌细胞数量显著增加(P<0.01)、巨噬细胞数量明显降低(P<0.01),且氯沙坦高剂量组较低剂量组作用更明显(P<0.01)。结论氯沙坦在不影响血脂水平情况下,可通过减轻载脂蛋白E基因缺陷小鼠氧化应激,增加斑块中平滑肌细胞数量,降低巨噬细胞数量,可能起到稳定粥样斑块作用,且随剂量增加作用增强。

种植初期稳定性的意义及其参数标准

通过文献复习,梳理明确种植初期稳定性的性质、意义、测试、参数以及影响因素。种植初期稳定性即种植体⁃骨界面的锚固力,是一种纯粹的机械现象,其意义在于维持种植体静立不动状态,使新骨不受干扰地生长附着在种植体表面,避免纤维组织生长,最终达到骨整合。临床比较常见的初期稳定性测试方法有植入扭力(insertion torque,IT)、共振频率分析(resonance frequency analysis,RFA)的种植体稳定指数(implant sta⁃bility quotient,ISQ)、叩诊试验Periotest等,以IT值更为常用,直接以IT值代替初期稳定性。目前未能就预示骨整合的初期稳定性具体参数标准形成统一认识,各个数值段初期稳定性的种植均有可能达到骨整合,但过高的初期稳定性有形成界面骨质微骨折导致骨坏死进而种植失败的可能。影响初期稳定性的因素有种植体的设计、牙槽骨骨质条件以及手术技巧三个方面。临床上在初期稳定性欠佳的情况下,即刻种植仍有获得成功骨整合的可能,需要重新审视现有测量初期稳定性手段的准确性,这直接关联临床是否能够选择正确合适的种植治疗路径。

Simulation Study on Active Roll Control of Vehicles

The effects of active control on the vehicle roll were studied. Based on the theory that distributing the greater roll stiffness to the rear axle can improve tracking trajectory capacity and increase maneuver stability, an eight degrees of freedom vehicle model was established and feedforward feedback control strategy was devised to control distribution of lateral load transfer on the front axle and the rear one. Simulation results showed that the proposed control strategy can improve comfort, maneuver stability and safety effectively.

Active Vibration Control and Stability Analysis of Cantilever Plate

Active vibration control and stability analysis of cantilever plate are discussed. Based on the analysis of characteristic equation of the closed loop control system, it is shown that such an active control may increase damping properties of the system, meanwhile it may result in instability of the system. It is stable when the feedback only occurs between the collocated sensors and actuators, but it may be unstable when there exists the feedback between sensors and actuators, which mainly depends on the property of the gain matrix of feedback. If the gain matrix is symmetric and definitely positive, the system is stable.

Integrated yaw and rollover control based on differential braking for off-road vehicles with mechanical elastic wheel

Aiming at the issue of yaw and rollover stability control for off-road vehicles with non-pneumatic mechanical elastic wheel(MEW),an integrated control system based on fuzzy differential braking is developed.By simplifying the structure of the MEW,a corresponding fitting brush tire model is constructed and its longitudinal and lateral tire force expressions are set up,respectively.Then,a nonlinear vehicle simulation model with MEW is established to validate the proposed control scheme based on Carsim.The designed yaw and rollover control system is a two-level structure with the upper additional moment controller,which utilizes a predictive load transfer ratio(PLTR)as the rollover index.In order to design the upper integrated control algorithm,fuzzy proportional-integral-derivative(PID)is adopted to coordinate the yaw and rollover control,simultaneously.And the lower control allocator realizes the additional moment to the vehicle by differential braking.Finally,a Carsim-simulink co-simulation model is constructed,and simulation results show that the integrated control system could improve the vehicle yaw and roll stability,and prevent rollover happening.

Different Types of Projective Synchronization in a Class of Time-Delayed Chaotic Systems Using Active Control Approach

We study different types of projective synchronization （projective-anticipating, projective, and projectivelag synchronization） in a class of time-delayed chaotic systems related to optical bistable or hybrid optical bistable devices. We relax some limitations of previous work, where the scaling factor a can not be any desired value. In this paper, we achieve projective-anticipating, projective, and projective-lag synchronization without the limitation of a. A suitable controller is chosen using active control approach. Based on the Lyapunov stability theory, we derive the sufficient stability condition through theoretical analysis. The analytical results are validated by the numerical simulations using Ikeda model and Mackey-Glass model.

Robust control of hand wheel torque for active front steering system

Active front steering(AFS)system has been used as a promising technology which improves the steering portability and handing stability of vehicles.It employs a steering motor to realize the functions of variable steering ratio and vehicle stability control.However,it has a serious problem of unexpected reaction hand wheel torque caused by the additional steering angle.In this paper,the optimum hand wheel torque is designed based on the linear tire model.Considering the uncertainty and disturbance of the steering system and vehicle,an H∞controller is developed to make sure the hand wheel torque follows the reference torque accurately and quickly.The simulation shows that the proposed controller can compensate the unnatural reaction torque and provide a good steering feel for the driver.

Path planning and stability control of collision avoidance system based on active front steering

Vehicle collision avoidance system is a kind of auxiliary driving system based on vehicle active safety,which can assist the driver to take the initiative to avoid obstacles under certain conditions,so as to effectively improve the driving safety of vehicle.This paper presents a collision avoidance system for an autonomous vehicle based on an active front steering,which mainly consists of a path planner and a robust tracking controller.A path planner is designed based on polynomial parameterization optimized by simulated annealing algorithm,which plans an evasive trajectory to bypass the obstacle and avoid crashes.The dynamic models of the AFS system,vehicle as well as the driver model are established,and based on these,a robust tracking controller is proposed,which controls the system to resist external disturbances and work in accordance with the planning trajectory.The proposed collision avoidance system is testified through CarSim and Simulink combined simulation platform.The simulation results show that it can effectively track the planning trajectory,and improve the steering stability and anti-interference performance of the vehicle.