Design and validation of a slender guideway for Maglev vehicle by simulation and experiment

Normally, Maglev (magnetic levitation) vehicles run on elevated guideways. The elevated guideway must satisfy various load conditions of the vehicle, and has to be designed to ensure ride quality, while ensuring that the levitation stability of the vehicle is not affected by the deflection of the guideway. However, because the elevated guideways of Maglev vehicles in South Korea and other countries fabricated so far have been based on over-conservative design criteria, the size of the structures has increased. Further, from the cost perspective, they are unfavourable when compared with other light rail transits such as monorail, rubber wheel, and steel wheel automatic guided transit. Therefore, a slender guideway that does have an adverse effect on the levitation stability of the vehicle is required through optimisation of design criteria. In this study, to predict the effect of various design parameters of the guideway on the dynamic behaviour of the vehicle, simulations were carried out using a dynamics model similar to the actual vehicle and guideway, and a limiting value of deflection ratio of the slender guideway to ensure levitation control is proposed. A guideway that meets the requirement as per the proposed limit for deflection ratio was designed and fabricated, and through a driving test of the vehicle, the validity of the slender guideway was verified. From the results, it was confirmed that although some increase in airgap and cabin acceleration was observed with the proposed slender guideway when compared with the conventional guideway, there was no notable adverse effect on the levitation stability and ride quality of the vehicle. Therefore, it can be inferred that the results of this study will become the basis for establishing design criteria for slender guideways of Maglev vehicles in future.     

A comprehensive study on the stability analysis of vehicle dynamics with pure/combined-slip tyre models

In this paper, a vehicle's lateral dynamic model is developed based on the pure and the combined-slip LuGre tyre models. Conventional vehicle's lateral dynamic methods derive handling models utilising linear tyres and pure-slip assumptions. The current article proposes a general lateral dynamic model, which takes the linear and nonlinear behaviours of the tyre into account using the pure and combined-slip assumptions separately. The developed methodology also incorporates various normal loads at each corner and provides a proper tyre–vehicle platform for control and estimation applications. Steady-state and transient LuGre models are also used in the model development and their responses are compared in different driving scenarios. Considering the fact that the vehicle dynamics is time-varying, the stability of the suggested time-varying model is investigated using an affine quadratic stability approach, and a novel approach to define the critical longitudinal speed is suggested and compared with that of conventional lateral stability methods. Simulations have been conducted and the results are used to validate the proposed method.     

Robust control and actuator dynamics compensation for railway vehicles

A robust controller is designed for active steering of a high speed train bogie with solid axle wheel sets to reduce track irregularity effects on the vehicle’s dynamics and improve stability and curving performance. A half-car railway vehicle model with seven degrees of freedom equipped with practical accelerometers and angular velocity sensors is considered for the H_∞ control design. The controller is robust against the wheel/rail contact parameter variations. Field measurement data are used as the track irregularities in simulations. The control force is applied to the vehicle model via ball-screw electromechanical actuators. To compensate the actuator dynamics, the time delay is identified online and is used in a second-order polynomial extrapolation carried out to predict and modify the control command to the actuator. The performance of the proposed controller and actuator dynamics compensation technique are examined on a one-car railway vehicle model with realistic structural parameters and nonlinear wheel and rail profiles. The results showed that for the case of nonlinear wheel and rail profiles significant improvements in the active control performance can be achieved using the proposed compensation technique.     

仿人形机器人运动的自适应控制

用Danevit-Hartenberg坐标变换法推导了仿人机器人的动力学与运动学方程,建立了仿人机器人的广义雅可比矩阵.设计了自适应控制器,以保证该仿人机器人系统的渐近稳定.给出了该机器人在做高难度舞蹈动作时各关节的运动轨迹以及仿真截图.结果验证了该方法的可行性和有效性.     

汽车非线性悬架的混沌研究

采用基于实测数据建立的非线性悬架模型,分析了汽车悬架中的非线性弹簧力和阻尼力,对非线性悬架系统的混沌运动进行了研究.在单频正弦路面、拟周期路面以及随机路面激励情况下,仿真计算得到了系统的响应.分析各激励下系统的相轨迹、庞加莱(Poincaré)截面、时间历程曲线、功率谱图及李亚谱诺夫(Lyapunov)指数图,结果表明非线性悬架系统中存在混沌现象.     

钢筋混凝土结构锈胀裂缝的计算机模拟

根据钢筋混凝土锈胀动力学原理,推导出锈蚀钢筋周围混凝土锈胀位移场的表达式。并用基于虚拟裂缝模型（ＦＭ）的非线性有限元方法,建立了钢筋混凝土结构的锈胀裂缝开裂过程的分析模型,利用编制的程序,对钢筋混凝土构件的锈裂过程进行了计算机模拟,结果表明,该模型为获得了锈胀开裂条件以及锈蚀量与锈胀裂缝宽度之间的定量关系提供了可能。     

Controlling Strange Attractor in Dynamics

A nonlinear system which exhibits a strange attractor is considered, with the goal of illustrating how to control the chaotic dynamical system and to obtain a desired attracting periodic orbit by the OGY control algorithm.     

轨道横向动力特性振型叠加法分析

本文对包括两根钢轨、轨枕、道床的点支承欧拉梁轨道横向振动力学模型,用振型叠 加法进行了分析,得到了20一500比频率范围内的位移响应.它与轨道实际情况有良 好的一致性。计算结果表明,本方法分析频率范围广,计算量小,是分析软道横向动力 特性的有效方法。      

高速客车对轨道的垂向动力作用研究

本文从系统工程的观点出发,将车辆与轨道二个子系统作为一个总体系 统来考虑,建立了车辆一轨道藕合系统的垂向动力学模型及其详细的健 图模型。应用这一模型研究了高速客车对轨道的垂向动力作用问题。结 果表明:当轨道存在垂向不平顺时,高速列车时轨道将产生剧烈的动力 作用;为降低这种作用,必须要使车辆与执道参数合理匹配,并衬轨道 维护质量提出较高要求。