Path planning,modeling and simulation of an autonomous articulated heavy construction machine performing a loading cycle

This research presents path planning and tracking for an articulated large wheel loader during the travel portion of a loading cycle. The study proposes a methodology for path planning, modeling, simulation and control of such vehicles; the analysis focuses on all of these components together and explains the relation among them. The developed methodology for path planning takes into account the dynamics and the performance characteristics of the heavy construction articulated vehicles, it also takes into account the construction working site constraints. The path optimization criterion is based on distance and cusp minimization without neglecting the constraints imposed by the size of the vehicle and its stable turning radius. The proposed path planning methodology is an extension and an improvement for Reeds and Shepp algorithm for a point shortest path calculation. The optimal path is consisted of circular arcs and straight segments, the radius is constant and identical for each arc in the desired path, the radius assumed to be similar to the minimum turning radius of the machine. When optimizing articulated machine path; to best account for machine size and articulation; more than one approach are discussed and compared. The machine is modeled and simulated during tracing the pre-defined planned path. The machine model includes the main frames, tires and a steering controller. The developed PID controller is used to keep machine lateral position within the pre-defined path while traveling with constant speed. The results showed an acceptable optimized path which the machine is able to track closely.     

When to rush a ‘behind’ in Australian rules football: a dynamic programming approach

In Australian rules football, points are scored when the ball passes over the goal line. Six points are awarded for a goal when the ball passes between the two centre posts, and one point for a ‘behind’, when the ball passes between a centre post and an adjacent outer post. After a behind, the defending team has a free kick from the goal line. It may be worthwhile, particularly in the closing stages of a game, for a defending team voluntarily to concede a behind, by themselves passing the ball between the two outer posts, either to avert the possibility of an imminent goal or to increase the probability of scoring a goal themselves. A dynamic programming model is used to analyse this situation.     

Theoretical and experimental investigation of tyre dynamics

The lateral vibration of towed wheels - also called shimmy - is related to the elasticity of the suspension system or to the elasticity of the wheel. The second case is studied here since the majority of the vehicles has pneumatic tyres. A one degree-of-freedom wheel model is considered with perfect rolling and elastic tyre. To verify the theoretical stability charts, an experimental rig is built and one of the stability boundaries is identified. Close to a double Hopf bifurcation point quasiperiodic vibrations are observed. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Simulation of stiffness analysis of rubber material applied in resilient wheel

Resilient wheels are well-known for their contribution to prevent squealing, impact noise and dynamic stresses on unsprung masses. In this study, a FE model is established in ABAQUS to analyze the stiffness of resilient wheels based on the Mooney-Rivlin hyperelastic material theory. The modes of each part in the resilient wheel and the whole wheel are calculated. The static and dynamic stiffness of the resilient wheel are analyzed. The simulation shows that the resilient wheel can reduce the dynamic loads both in the lateral and vertical directions between the vehicle and the track. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Real-time bus rollover prediction algorithm with road bank angle estimation

The bus rollover warning has achieved many progresses for researcher endeavors in the past decades. But these researches have not taken account for dynamic road bank. To fill up the gap, this paper presents a real-time rollover trend prediction to indicate bus rollover risk with road bank estimation. The prediction algorithm consists of a dynamic roll stability analysis, which is based on a suspended roll plane model, and a real-time warning velocity calculation. An estimator for the dynamic road bank and vehicle sideslip angle estimation using the dynamic simplex algorithm (DSA) is designed to take into account the influence of road bank on rollover trend. By comparing maximum stable lateral acceleration to the affordable lateral acceleration depending on the tire/road friction limit, a warning velocity is determined using the measurement of lateral acceleration and the estimate of instantaneous vehicle turning radius. The proposed rollover trend prediction algorithm is evaluated by TruckSim software. Simulation results show that the proposed warning velocity can represent the vehicle potential to resist rollover and give appropriate prediction of vehicle rollover crashes in typical scenarios.     

Numerical study of the stability of breakwater built on a sloped porous seabed under tsunami loading

Strong earthquake induced huge tsunami has occurred for three times in Pacific ocean in recent ten years; for example, the tsunami triggered by the Sumatra earthquake in 2004, Chile earthquake in 2010 and Tohoku earthquake (Japan) in 2011. Tsunami carrying huge energy always would bring high risks to the population living near to coastline. Breakwater is widely used to dissipate the wave energy, and protect coastline and ports. However, they are vulnerable when being attacked by tsunami wave. At present, the interaction mechanism between tsunami, breakwater and its seabed foundation is not fully understood. In this study, the dynamics and stability of a breakwater under the attacking of tsunami wave is investigated by adopting an integrated model PORO-WSSI 2D, in which the VARANS equation for wave motion, and the Biot’s dynamic equation for soil are used. Based on the numerical results, it is found that offshore breakwater interacts intensively with tsunami wave when it overtopping and overflowing over a breakwater. The impact force on the lateral side of breakwater applied by tsunami wave is huge. The shear failure is likely to occur in the seabed foundation of breakwater. The liquefaction is unlikely to occur due to the fact that there is basically no upward seepage force in seabed foundation in the process of tsunami wave passing through the breakwater.     

Numerical and experimental investigation on stochastic dynamic load of a heavy duty vehicle

Numerical simulation and field test are used to investigate tire dynamic load. Based on multi-body dynamics theory, a nonlinear virtual prototype model of heavy duty vehicle (DFL1250A9) is modeled. The geometric structural parameters of the vehicle system, the nonlinear characteristics of shock absorber and leaf springs are precisely described. The dynamic model is validated by testing the data, including vertical acceleration of driver seat, front wheel, intermediate wheel and rear wheel axle head. The agreement between the response of the virtual vehicle model and the measurements on the test vehicle is satisfactory. Using the reliable model, the effects of vehicle speed, load, road surface roughness and tire stiffness on tire dynamic load and dynamic load coefficient (DLC) are discussed. The results demonstrate that the proposed model can offer efficient and realistic simulation for stochastic dynamic loads, so as to investigate vehicle road-friendliness.     

Stability analysis of data-driven local model networks

This article discusses stability analysis of data-driven dynamic local model networks. In contrast to traditional fuzzy modelling, the structure and complexity of such model architectures is not unique when only observed input- and output data are available for their parametrization. The present article complements the well-known trade-off between accuracy and complexity by the notion of stability. For this purpose, existing Lyapunov stability criteria for local model networks are extended by a decay rate which represents a scalar and quantitative stability measure. It allows to compare models with different degrees of complexity also in view of their stability. For some of the commonly available Lyapunov stability criteria, the individual local model transitions are crucial. Therefore, in this article, an approach is introduced to determine the actually occurring model transitions by means of the identification data. The methods presented in the article are illustrated and discussed by means of a simulation example. It is shown how model complexity and the related approximation quality can have an adverse impact on the stability and how the outcome of different Lyapunov criteria is affected by the proper determination of local model transitions.     

A model of the dynamic of transmission of malaria, integrating SEIRS, SEIS, SIRS and SIS organization in the host-population

In this paper, we propose and analyse a model of dynamics trans-mission of malaria, incorporating varying degrees p of susceptible and ofinfectious that makes the dynamic of the overall host population integrateSEIRS, SEIS, SIRS and SIS at the same time. For this model we compute anew threshold number and establish the global asymptotic stability of thedisease-free equilibrium when R0 < < 1. If < R0 < 1, the system admits aunique endemic equilibrium (EE) and if R0 > 1 depending on case the systemadmits one or two endemic equilibrium. Numerical simulations are presentedfor dierent value of R0, based on data collected in the literature. Finally,the impact of parameters p and of system dynamics are investigated.     

Influence of the rail pad on a vehicle travelling on a straight track

In the following text, the influence of the stiffness of rail fastening systems of high‐speed railway lines on the dynamic stability of a vehicle travelling along a straight track is investigated. The dynamic behaviour of the rail head in lateral direction is incorporated in the model by means of mechanical models derivedfrom a preceding frequency analysis of the track. For the wheel‐rail interface, linear contact mechanics and kinematic relations are applied. The investigation leads to the conclusion that on high‐speed lines the critical velocity of vehicles is reduced as a result of the increased elasticity of the rail pads. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Plastification and Damage in Wheel-Rail Rolling Contact – Case Study on a Crossing

A fully three-dimensional, dynamic model for a wheel running over a crossing is developed using an explicit finite element program. The full mass of the wheel and the crossing and elastic-plastic material behaviour are considered. The damage in the contact area is investigated with a very dense mesh taken from the dynamic model using a submodelling technique. With this kind of calculations the stresses and strains produced in the wheel and the crossing during the cross-over process can be determined, as well as the respective reaction forces in the bedding and the axle. Calculations for different crossing-geometries are performed. Finally a damage indicator is introduced to identify the probable location of crack initiation. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

大范围运动刚体上矩形薄板力学行为分析

采用Hamilton变分原理建立了大范围运动平板的动力学模型．从理论上证明了不同大范围运动状态下平板中既可存在动力刚化效应,也可存在动力软化效应,且动力软化效应还可使板的平衡状态发生分岔而失稳．采用假设模态法验证了理论分析结果并得到了分岔临界值和近似后屈曲解．     

On the stability of evolutionary dynamics in games with incomplete information

In an interaction it is possible that one agent has features it is aware of but the opponent is not. These features (e.g. cost, valuation or fighting ability) are referred to as the agent’s type. The paper compares two models of evolution in symmetric situations of this kind. In one model the type of an agent is fixed and evolution works on strategies of types. In the other model every agent adopts with fixed probabilities both types, and type-contingent strategies are exposed to evolution. It is shown that the dynamic stability properties of equilibria may differ even when there are only two types and two strategies. However, in this case the dynamic stability properties are generically the same when the payoff of a player does not depend directly on the type of the opponent. Examples illustrating these results are provided.     

On the nonlinear dynamics of a high-speed railway vehicle with nonsmooth elements

A comprehensive lateral mathematical model of a high-speed railway vehicle with 17 degrees of freedom is built to study its nonlinear dynamics on a straight line. The hunting stability is explored by using eigenvalue analysis, bifurcation diagrams and the first Lyapunov coefficient. Due to the non-smoothness in the wheel/rail contact table and the secondary suspension elements such as anti-yaw dampers, bump stops, etc., an event-driven strategy is applied in the integration process of the ODEs. As an example, the nonlinear dynamics of a Chinese Railway High-speed (CRH) vehicle (named CRH2) is investigated. The result shows that the stable equilibrium of the high-speed railway vehicle loses its stability through a supercritical Hopf bifurcation with the increase of the forward speed, and the stable periodic solution loses its stability through a grazing bifurcation with the decrease of the forward speed. The influence of primary system parameters on the hunting stability of the high-speed railway vehicle is also investigated.     

库存计划的稳定性和公司激励机制

文章讨论了在制造生产管理中库存计划的稳定性和公司激励机制 .公司通过工资制度激励工人 .构造了一个以公司和工人为目标的双目标规划模型 ,同时模型中考虑了库存计划的稳定性 .最后讨论了模型分别在制造加工速度由市场外部条件决定和由公司内部决策两种情况下的应用 .     

具有动应力、位移和稳定性约束的离散变量桁架结构布局优化设计算法

给出了在动应力、动位移和动稳定约束下离散变量结构布局优化设计问题的数学模型,用“拟静力”算法,将具有动应力约束、动位移约束和动稳定约束的离散变量结构布局优化设计问题化为静应力、静位移和静稳定约束的优化问题,然后利用两级优化算法求解该模型．优化过程由两级组成,拓扑级优化和形状级优化．在每一级,都使用了综合算法,并且在搜索过程中都根据两类设计变量的相对差商值进行搜索．对包含稳定约束和不包含稳定约束的优化结果做了比较,结果显示稳定性约束对优化结果产生较大的影响．     

电力市场实用稳定性的判定条件

首次把实用稳定性的理论用于电力市场稳定性的研究中.结合Alvarado提出的电力市场动态模型,利用微分代数方程与特征值技术,从理论上研究电力市场的实用稳定性,并且给出了判断电力市场实用稳定、一致实用稳定和实用渐近稳定性的充分条件.利用这些实用稳定性条件,对于Alvarado给出的数值算例,可方便地利用初始数据判断电力市场模型的实用稳定性,并通过实例提供了假设模型中某个参数在电力市场变化中起主要作用,如何控制电力市场模型实用稳定性的方法.最后利用Maple软件包给出了参数变化引起模型实用稳定和不稳定的图形演示.     

Cornerning radial tyres

An angular difference between direction of wheel motion and wheel plane produced a lateral force on a rolling tyre. A simple mechanism of shear stress generation in the contact area of tread is used. The coefficient of friction plays a limiting role. The resulting lateral force and self-aligning torque are computed by means of the belt model of a radial tyre. Finally, some numerical results are given to illustrate the theory.