基于物理的虚拟手交互碰撞力觉生成和反馈

提出一种考虑摩擦的虚拟手交互碰撞力觉生成和反馈方法，以让用户手指感受到逼真的冲击，增强虚拟操作的真实性和沉浸感．该方法首先运用冲量定理和弹性恢复系数，求得质点刚体在二维空间碰撞后的运动状态，然后结合库仑定理，生成质点刚体有摩擦的碰撞力，并拓展到三维空间的虚拟环境中，计算非质点的虚拟刚体碰撞的力矩，再通过虚拟手静力抓持力觉生成模型，将碰撞力和碰撞力矩作用到虚拟手上，求得每个虚拟手指受到的冲击力．当虚拟手抓持的物体与其它虚拟物体发生碰撞时，利用CyberGrasp力觉反馈数据手套，用户手指可感受到逼真的冲击力．实验结果表明运用所提出的方法，用户在虚拟装配时可感受到真实的碰撞力．     

伺服系统摩擦的支持向量回归建模与反步控制

研究了一种伺服系统摩擦建模和控制的新方法.首先,根据实验数据,提出了基于支持向量机回归的自适应库仑摩擦和固定库仑摩擦建模方法,以解决在速度为零时摩擦力矩不连续导致的建模不准确问题.然后应用所建立的摩擦模型,使用反步法设计了控制器从而实现了摩擦的自适应补偿.通过使用Lyapunov理论证明了闭环系统的稳定性.仿真结果验证了该方法的有效性.     

含摩擦滑移铰及驱动约束多刚体系统数值算法

研究了具有驱动约束及非光滑滑移铰多体系统动力学方程的建模与数值计算方法．将驱动约束视为非定常约束，非光滑滑移铰视为双边定常约束，滑移铰的摩擦模型采用库仑摩擦模型；应用第一类Lagrange方程建立系统的动力学方程，应用距离函数建立滑移铰的约束方程；将线性互补方法和Baumgarte约束稳定化方法引入，以解决滑移铰法向约束力的计算以及约束方程违约问题．最后应用曲柄摇杆机构作为算例，说明该方法的有效性．     

用态势模型预测基因表达式编程的进化难度

在基因表达式编程(gene expression programming,简称GEP)中,由于不同问题得到的适应度-距离相关系数(fitness-distance correlation,简称FDC)值很相近,所以难以用FDC预测GEP求解不同问题的进化难度.为了解决该问题,提出了态势模型及其区间密度指标来预测GEP的进化难度.主要工作包括:(1)提出了GEP染色体之间的距离和态势模型的新概念;(2)提出了态势模型中的区间密度指标;(3)从动力学角度证明了态势模型是对GEP原搜索空间的一种映射,并且该映射保持了种群在原搜索空间中移动的动力学性质;(4)分析了用态势模型区间密度预测GEP进化难度的合理性;(5)用实验验证了区间密度能够准确预测GEP求解问题的进化难度.     

核电厂电气设备陶瓷部件受风生飞射物的冲击破坏

为研究沿海台风中的风生飞射物对核电厂电气设备的冲击破坏，以核电厂户外高压电气设备的陶瓷绝缘材料为研究对象，基于LS-DYNA和HyperMesh，分析陶瓷部件在小球和钢管打击下的破坏情况。结果表明：在受到钢管垂直打击时，陶瓷部件很容易发生破坏；在受到小球冲击时，陶瓷部件局部表面发生破坏。进一步计算得到小球对陶瓷部件的临界破坏冲击速度，可为后续设计和研究提供参考。     

一个求解非线性方程组的区间检验算法

引言非线性方程组的数值求解一直是计算数学的中心任务之一，越来越受到人们的重视．以Newton迭代法为代表的点迭代方法一直是被广泛运用的求解方法．但是，点迭代方法难以进行可靠的误差估计，且对迭代初值有较为苛刻的要求．本世纪七十年代以后兴起的区间分析方法可用于求解非线性方程组，特别在解的误差估计和解的存在性检验方面是卓有成效的．但是，区间方法的致命缺点是计算速度慢，运算量大；而且由于区间运算的复杂性，其程序的实现难度很大，有时甚至难以用于实际计算．这些缺点严重地限制了区间方法的应用和发展．因此，人们自然…     

空间太阳能电站的轨道、姿态和结构振动的耦合动力学建模及辛求解

作为一种从太空获得清洁能源的系统,空间太阳能电站(SPS)吸引着许多国家和科研机构的关注.由于其超大、超轻的柔性结构特点,研究其在轨动力学行为时需要考虑轨道、姿态和结构振动的耦合作用.本文在考虑地球的非球形摄动影响下,建立了集成对称聚光系统(ISC)的动力学模型.通过Legendre变换引入广义动量,在Hamilton体系下建立了其轨道、姿态、轴向振动耦合的动力学方程.采用辛Runge-Kutta方法对耦合动力学方程进行数值求解.根据数值结果,分别研究了其在地球同步轨道下二阶摄动项对轨道、姿态和结构振动的影响,并分析了总能量的变化情况.     

基于重心动力学及虚拟模型的负载型四足步行平台对角步态控制方法

为提高负载型四足步行平台对角步态行走的稳定性,减小较大的腿部质量及偏心质量对稳定行走的影响,提出融合重心动力学及虚拟模型的控制方法．应用虚拟模型控制方法对机身及摆动腿加速度进行求解．结合平台重心动力学模型得到其所受合外力,而后应用二次规划将平台合外力分配到支撑腿足端．接着运用逆向动力学和关节空间PD控制得到步行平台关节力矩．通过Adams和Simulink对负载型四足步行平台对角步态行走进行仿真,并将该方法与虚拟模型控制算法进行对比．结果表明重心动力学及虚拟模型控制方法能够使平台姿态角稳定在目标值附近,在平台受到侧向冲击情况下横滚角、俯仰角分别减小约42%、21.8%,在机身偏心全向行走过程中减小50%、89%．证明了所提控制方法能够有效应对较大的腿部质量及偏心质量的影响,提高负载型四足步行平台对角步态行走的稳定性和鲁棒性．     

缸套-活塞系统中DAE与PDE联合求解方法

针对内燃机缸套-活塞系统中DAE(Differential-Algebraic Equation)和PDE(Partial Differential Equation)难以用专业软件进行求解的问题,提出一种联合求解该系统中DAE与PDE的新方法。首先,在Dymola平台上建立该系统的DAE模块,同时在Matlab平台上构建它的PDE部分,然后通过建立DAE和PDE模块之间连接通信接口实现联合求解。这里,以某型号汽油机为实例,在考虑其活塞二阶运动、缸套-活塞之间油膜厚度变化、摩擦力及摩擦功耗等因素的条件下,建立了缸套-活塞系统模型,并对该模型进行了数值分析求解。通过对求解结果的分析,验证了这种求解方法的可行性。结果表明,采用上述方法求解,大大减少了缸套-活塞系统建模工作量,避免了活塞动力学方程变量代换,减少建模中方程编辑出错,同时也保证求解过程中算法的稳定性和求解结果的正确性。     

旧混凝土路面共振破碎力学机理

采用有限元法建立旧混凝土路面的动力学模型,运用ANSYS进行模态分析和谐响应求解.基于混凝土破坏的莫尔-库仑准则判定使路面产生共振破坏的激振力的临界力幅.结果表明:考虑基层影响所得到的模型基频比单纯面层小;路面缺陷会使频率减小;在给定参数下,随着激振力的增大,在路面板中心处产生剪切破坏.     

一类脉冲动力系统的状态反馈控制

对一类具有状态反馈控制的脉冲动力系统的动力学性质进行了研究．由周期解的扰动解得到了一个Poincare映射，利用Poincare映射讨论了系统周期解的分岔，并得到了半平凡周期解和正周期-1解存在和稳定的充分条件．定性分析和数学模拟表明，半平凡周期解通过fold分岔分钻出正周期-1解，正周期-1解通过flip分岔分岔出正周期-2解，再通过一系列flip分岔通向混沌，此外，讨论了脉冲状态反馈控制的效果．     

Impact controllability of an air hockey puck

In this paper, we investigate the controllability of an air hockey puck sliding on a frictionless table and subject to impacts from a mallet. This problem is a special case of the more general problem of impulsive manipulation. We first characterize the set of velocities reachable with arbitrary impulsive inputs. In reality, one cannot specify impulsive forces as inputs but rather only the velocity of a mallet impacting the puck. Therefore, we refine the characterization to the case that the impulsive forces arise through impacts with a mallet whose velocity can be arbitrarily controlled. The characterization of the reachable puck velocities then depends on the material properties of the impacting objects. We use the two-dimensional Routh impact model to determine these reachable velocities in terms of the coefficients of friction and restitution. We show that the system satisfies an accessibility-like property as long as the coefficient of friction is nonzero.     

Dynamic analysis of impact in swing-through crutch gait using impulsive and continuous contact models

The dynamics associated with the impact of the crutch with the ground is an important topic of research, since this is known to be the main cause of mechanical energy loss during swing-through gait. In this work, a multibody system representing a subject walking with crutches is used to investigate the behavior of two different contact models, impulsive and continuous, used for impact analysis. In the impulsive (discrete) approach, the impact interval is considered to be negligible and, therefore, the system configuration is constant. The postimpact state is directly obtained from the preimpact one through algebraic equations. In the continuous approach, the stiffness and dissipation characteristics of the contact surfaces are modeled through nonlinear springs and dampers. The equations of motion are integrated during the impact time interval to obtain the postimpact state, which, in principle, can differ from that obtained by means of the impulsive approach. Although both approaches have been widely used in the field of biomechanics, we have not found any comparative study in the existing literature justifying the model chosen for impact analysis. In this work, we present detailed numerical results and discussions to investigate several dynamic and energetic features associated with crutch impact. Based on the results, we compare the implications of using one contact model or the other.     

一类自治脉冲微分方程的动力学研究

对一类自治脉冲微分方程的动力学性质进行了研究,给出了半平凡周期解的存在与稳定的充分条件,建立Poincare映射将周期解问题转化为不动点问题．理论分析及数值模拟表明,半平凡周期解通过跨临界分岔获得稳定的正周期-1解．数值模拟显示,随着控制参数的变化,正周期-1解通过倍周期分岔出正周期-2解,再通过一系列倍周期分岔通向混沌．     

Stability and stabilization of Boolean networks with impulsive effects

This paper investigates the stability and stabilization of Boolean networks with impulsive effects. After giving a survey on semi-tensor product of matrices, we convert a Boolean network with impulsive effects into impulsive discrete-time dynamics. Then, some necessary and sufficient conditions are given for the stability and stabilization of Boolean networks with impulsive effects. Finally, examples are provided to illustrate the efficiency of the obtained results.     

Dynamics of planar rocking-blocks with Coulomb friction and unilateral constraints: comparisons between experimental and numerical data

This paper concerns the dynamics of planar rocking blocks, which are mechanical systems subject to two unilateral constraints with friction. A recently introduced multiple impact law that incorporates Coulomb friction is validated through comparisons between numerical simulations and experimental data obtained elsewhere by other authors. They concern the free-rocking motion with no base excitation, and motions with various base excitations for the study of the onset of rocking and of the overturning phenomenon. The comparisons made for free-rocking and for the onset of rocking demonstrate that the proposed impact model allows one to correctly predict the block motions. Especially the free-rocking experiments can be used to fit the impact law parameters (restitution and friction coefficients, block width). The free-rocking fitted parameters are then used in the excited-base cases.     

非光滑系统的混沌同步

通过广义哈密顿系统和观测器法，本文将非光滑混沌系统的同步问题转化成了研究光滑系统零解的稳定性，从而给出了混沌同步的条件．对具体的带于摩擦，碰撞的Duffing振子分别进行研究，使其达到了完全同步，表明该方法的正确性．     

Frequency-domain iterative learning control of a marine vibrator

To the purpose of marine seismic acquisition, new acoustic sources have been developed to reduce the environmental impact. The use of marine vibrators makes it possible to define emission frequency ranges, consequently allowing limitation of the frequencies that disturb marine animal life. Constructing marine vibrators with high efficiency and linear dynamics is however difficult, and the vibrators suffer from both friction, backlash and high-order harmonics. These nonlinear effects, in combination with drifting dynamics, make the required control a crucial and challenging problem. This paper presents a model-based iterative learning control solution, performed in the frequency-domain. Additionally, an adaptive reidentification algorithm is developed to cope with drifting dynamics. The proposed solutions are successfully evaluated in experiments with a marine vibrator.     

Stochastic input-to-state stability for impulsive switched stochastic nonlinear systems with multiple jumps

In this study, we investigate the stochastic input-to-state stability (SISS) of impulsive switched stochastic nonlinear systems. In this model, the impulse jumps are component multiple maps that depend on time. Thus the model differs from traditional impulsive systems with single impulse between two adjacent switching times. We provide sufficient conditions in three cases with the SISS system by using the Lyapunov function and average impulsive interval approach. The destabilising impulses cannot destroy the SISS properties if the impulses do not occur too frequently when all the subsystems that control the continuous dynamics are SISS. In other words, the average impulsive interval satisfies a lower bound restraint. Conversely, when all subsystems that control the continuous dynamics are not SISS, impulses can contribute to stabilising the system in the SISS sense when the average impulsive interval satisfies an upper bound. Then, we investigate the SISS property of impulsive switched stochastic nonlinear systems with some subsystems that are not SISS under certain conditions such that the property remains obtained. Finally, we show three examples to demonstrate the validity of the main result.     

Closed-form solution of an idealized,optimal, highly eccentric hyperbolic rendezvous problem

Closed-form solutions of optimal impulsive rendezvous problems are difficult to obtain, even using linearized equations. An idealized model of a highly eccentric hyperbolic impulsive rendezvous problem is constructed by considering the limit as the eccentricity tends to infinity. In this manner, a closed- form solution of an idealized hyperbolic rendezvous problem can be obtained. This idealized solution establishes an arbitrarily good approximation to a solution of the problem of optimal impulsive rendezvous of a spacecraft near a satellite in hyperbolic orbit of sufficiently high eccentricity.