基于事件驱动的环形编队多智能体系统

研究了控制器采用事件驱动机制时,多智能体系统的环形编队控制问题.事件驱动控制机制用来降低个体控制更新的频率,以此减少整个系统的能量消耗.假设所有智能体始终在一固定的圆环上运动,并且每个智能体只能感知到其前后两个紧邻智能体的信息.利用邻居的信息,对每个智能体设计分布式控制律,在事件驱动控制机制下,所提控制策略可以使多智能体系统形成给定的期望环形编队,并将环形编队扩展到特殊的均匀环形编队形式.数值的仿真验证了所提控制策略的有效性.     

输入饱和受限的多个四旋翼飞行器分布式编队控制

研究了多个四旋翼飞行器在主从结构下的分布式同步协调编队控制问题.基于反步法的设计思想,文章提出了一种有界的分布式一致性控制算法,以保证满足输入饱和受限条件.首先,对于位置控制子系统,基于比例微分控制和一致性理论,设计了一种多个四旋翼飞行器的协调编队控制律,来使所有的四旋翼飞行器都可以向领导者收敛,并沿着理想的编队轨迹运动.针对位置系统设计的分布式一致控制律将为姿态控制子系统的参考姿态输入信息.其次,针对基于四元数描述的姿态控制子系统,设计了一种饱和的全局姿态跟踪控制律,可以使飞行器跟踪上所期望的姿态.最后,通过数值仿真来验证所提方法的有效性.     

基于选择策略的移动机器人视觉伺服镇定方法

针对单目视觉非完整移动机器人系统,提出了一种基于选择策略的视觉伺服镇定控制方法.具体而言,首先在视觉位姿估计的基础上,将相对位置及指向角度作为系统误差量,利用Lyapunov方法设计了视觉镇定控制律;然后,为解决该控制律在某些初始位置下导致机器人产生较大旋转角度的问题,文章对误差形式进行调整得到负向镇定控制律,进而对上述两种控制律制定相应的选择策略;同时结合主动视觉使目标特征处于摄像机的视野(field-of-view,FOV)内.仿真与实验结果表明,视觉镇定控制律能以相同控制参数在不同初始位姿下高效完成镇定任务,并且该选择控制策略可使云台旋转角处于合理的运动范围内.     

高阶非完整系统的适应调节

通过综合利用“加幂积分器”的方法、“不连续投影”技巧和state scaling技巧构造出了一个不连续的动态适应控制律,解决了一类高阶参数非完整系统的适应调节问题．且所求控制律能确保未知参数的估值在一个预先给定范围内．     

粘弹性板混沌振动的输出变量反馈线性化控制

研究了粘弹性板混沌振动的控制问题·　应用非线性系统精确线性化控制理论导出了一类非仿射控制系统的非线性反馈控制律·　建立了描述材料非线性的粘弹性板运动的数学模型并利用Ｃａｌｅｒｋｉｎ 方法进行简化·　采用相空间曲线和频率谱密度函数说明了在特定参数条件下系统将出现混沌振动,并以位移为输出变量将混沌振动控制为给定的周期运动·     

网络化Euler-Lagrange系统的分布式编队机动控制北大核心CSCD

研究了网络化Euler-Lagrange系统自适应编队机动控制问题.针对参数不确定的Euler-Lagrange系统,利用滑模控制方法提出了一种自适应编队机动控制算法.基于Lyapunov稳定性理论,证明了闭环系统的稳定性.该算法的显著特点是通过引入一种特殊的有向网络拓扑来描述智能体之间的通信交互行为,使得系统中跟随者在不需要知道或估计时变机动参数的情况下,能够实现编队的方向、平移、形状的连续改变.最后对提出的自适应编队机动控制算法进行数值模拟以验证该控制方案的有效性.     

具有外部干扰的非线性多智能体系统的编队控制

多智能体系统编队控制因广泛应用于军事,航天,生物学等领域,成为国内外学者的关注热点.在实际应用中,当系统受到环境噪声等外部干扰时,利用领航者-跟随者的相对状态信息构造控制器无法形成预期队形.为解决这个问题,文章针对一类带有外部干扰的非线性多智能体系统,研究了领航-跟随编队控制问题.首先设计干扰观测器补偿外部干扰.其次利用自适应方法,给出了完全分布式的控制协议.再次选取适当的参数,证明了该分布式控制协议能实现系统的编队控制.最后通过仿真算例,验证了协议的有效性.     

利用太阳光压力进行Halo轨道编队控制

利用太阳光压力可以实现地日限制性三体问题中L2点附近编队控制.该编队需要的控制力量级小,常规的推进方式难以实现.太阳帆能产生微小的连续光压力,可以用于Halo轨道附近的编队控制.由于太阳光压力的方向受到限制,只有部分编队构型可以利用太阳光压力实现.该文主要讨论了两种常见的编队构型--直线编队和圆编队,给出了太阳帆能实现的编队构型需要满足的条件.最后,对每种构型的编队进行了数值仿真,仿真结果表明太阳帆能有效的进行编队控制.     

行星悬浮轨道附近的编队

研究了不同类型的地球和火星悬浮轨道附近的相对运动．首先,推导了悬浮轨道附近的相对运动方程并将相对运动方程在悬浮轨道附近线性化．利用两种半自然编队控制率进行编队控制,其中一种为被动控制,对工程应用有很大的价值．在两种控制率下,讨论了每种悬浮轨道的稳定区域．由于两种控制率都不能满足特殊的火星悬浮轨道任务要求,于是,根据该任务的要求设计了一种特殊的半自然控制率．该控制率既能满足编队任务的要求也能使相对运动稳定．     

DoS攻击下多智能体系统的事件触发编队控制

文章研究了拒绝服务(DoS)攻击情况下多智能体系统基于事件触发的编队控制问题.首先,基于系统状态构造了一种滑模编队控制算法,有效地克服外部干扰并实现时变编队.为了避免控制资源浪费,将事件触发策略应用于多智能体系统的编队控制中,并对奇诺(Zeno)现象的避免进行了详细的分析.假设DoS攻击是周期性发生的,针对具有DoS攻击的多智能体系统,提出了一种改进的触发机制,使其仍然能完成编队控制任务,并通过Lyapunov函数法和归纳法证明了控制系统的稳定性.最后,仿真结果验证了该方案的有效性.     

A posteriori error estimates for an optimal control problem of laser surface hardening of steel

The main focus of this article is on the development of a posteriori error estimates for an optimal control problem of laser surface hardening of steel, governed by a dynamical system consisting of a semi-linear parabolic equation and an ordinary differential equation. A posteriori error estimators are developed for the variables representing temperature, formation of austenite, and laser energy using residual method when a continuous piecewise linear discretization has been used for the finite element approximation of space variables and a discontinuous Galerkin method has been used for time and control discretizations. The error indicators are used in the implementation and numerical results are obtained.     

Optimal resource consumption control of perturbed systems

A method for calculating the optimal resource consumption control of perturbed dynamic systems is developed. This method includes both normal and singular solutions. According to the method proposed, the problem is subdivided into three independent tasks: (1) consideration of the effects of perturbations on the system, (2) computation of the optimal control structure, and (3) computation of the switching instants of the optimal control. The consideration of the influence of perturbations on the system and the transfer to a nonzero final state are reduced to the transformation of the initial and final states of the system. The control structure calculation is based on a specific method of quasi-optimal control formation. The control switching instants are found by using the relationship between deviations in the initial conditions of the conjugate system and deviations of the phase trajectory at the final instant. An iterative algorithm is developed, and its characteristics are considered. Results of modeling and numerical calculations are presented.     

基于遗传算法的割缝衬管防砂多目标优化

割缝衬管防砂是油田重要的防砂方式之一,过去的研究往往专注于一个目标来设计割缝衬管参数,从而在参数设计上不能使多个参数在整体上达到最优.基于遗传算法中的gamultiobj多目标优化算法,以衬管使用寿命、地层流动阻力、产能和衬管强度为目标,建立了割缝衬管防砂优化设计模型,得出了高产能,长使用寿命,低流动阻力的割缝参数防砂的最优组合.结果表明,制定多目标适应性分析,建立评价模型,在给定的取值范围内得到的工艺参数,该技术有助于优选和优化调整防砂方法,提高防砂成功率,增强油田寿命和降低开采成本.     

航天器编队飞行多目标姿态快速跟踪鲁棒控制

研究了航天器编队飞行多目标姿态跟踪鲁棒控制问题．主航天器装有一个快速机动天线和一个星载相机．考虑相机对地面目标跟踪,同时考虑天线与从航天器通信的空间任务．通过引入角速度约束和姿态角约束,分别推导了相机和天线的参考姿态角、角速度和角加速度．提出期望逆系统的概念,将三维空间姿态跟踪问题转化为调节问题,简化了控制器的设计．考虑存在参数摄动和外部干扰力矩的情况,基于期望逆系统和滑模控制,设计了鲁棒姿态跟踪控制器,并利用Liapunov稳定性理论证明了控制系统的渐近稳定性．以两航天器编队飞行多目标跟踪为例进行数值仿真,结果表明所设计的控制器具有良好的鲁棒性和优越的跟踪性能．     

Attractors of dynamical systems with control: topology of purposeful formation

The definitions of homogeneous and mosaic attractors of codimension one are given. A topological method for their purposeful formation by using the feedback control laws of controlled dynamical systems is suggested.Published in Ukrainskii Matematicheskii Zhurnal, Vol. 47, No. 1, pp. 129–132, January, 1995.     

神经激肽1受体拮抗剂对大鼠脑缺血再灌注的神经保护作用

目的观察大鼠局灶性脑缺血再灌注后神经激肽1受体拮抗剂对脑梗死体积、脑组织含水量及神经行为学变化的影响,探讨减轻神经源性炎症反应对脑缺血再灌注的保护作用。方法将54只大鼠分为药物组、假手术组、对照组,用线栓法建立右侧大脑中动脉缺血再灌注大鼠模型,药物组和对照组大鼠在再灌注时经尾静脉分别注入神经激肽1受体拮抗剂及生理盐水,假手术组只分离右侧颈总、颈内、颈外动脉。缺血再灌注后24h时采用免疫组化法检测P物质表达,氯化三苯基四氮唑染色法测定脑梗死体积,干-湿称重法检测脑组织含水量;分别于再灌注24h及72h时利用转棒试验和肢体不对称试验检测神经行为学变化。结果脑缺血再灌注后24h大鼠脑缺血区P物质的表达明显升高,脑组织含水量明显增加。药物组与对照组比较,脑组织含水量减少,神经功能改善。结论神经激肽1受体拮抗剂可通过抑制神经源性炎症反应而达到缺血再灌注损伤时的脑保护作用。     

Origin and Control of Dynamics of HexagonalPatterns in a Photorefractive Feedback System

We investigate the origin of dynamics of hexagonal pattern formation in aphotorefractive single feedback system. By introducing an asymmetry, we induced differentcomplex motion behaviours. A visualization method is presented and means to control thedynamics in the case of fixed external parameters are discussed.     

Distributed adaptive formation tracking using quantized feedback communication for networked mobile robots with unknown wheel slippage

In this study, we consider a quantized-feedback-communication-based control design problem for the distributed adaptive formation tracking of multiple nonholonomic mobile robots with unknown slippage constraints under capacity-limited network control environments. Uniform-hysteretic quantizers are employed to quantize all the inputs and states of robots and the quantized position information of each robot is only transmitted to neighboring robots through directed networks. Compared with existing literature related to the robot formation, the primary contribution of this paper lies in establishing a novel local adaptive control design methodology to deal with the discontinuity problem caused by using the quantized states of each follower and the quantized position communication of neighboring robots. In the proposed strategy, the communication of the orientations and velocities of neighboring robots is not required for the local control design of follower robots. Moreover, quantized-states-based adaptive compensation schemes are constructed for the effects of signal quantization and wheel slippage. Based on the analysis of quantization errors, the practical stability strategy of the overall closed-loop formation system is derived with the convergence of local tracking errors. Simulation results clarify the proposed formation strategy.     

Structure-sensitive liquid flowable compositions based on polyvinyl alcohol and silicotungstic acid

Conditions of the formation of structure-sensitive liquid flowable media based on 1.5 and 10% aqueous solutions of polyvinyl alcohol containing silicotungstic acid and water-soluble carboxy-methylcellulose in the form of its potassium salt (Na-CMC) are examined. Rheological, optical, and dielectric relaxation methods revealed the formation of several types of interpolymer complexes in the examined liquid flowable media. This leads to the formation of associates and an increase in the molecular mobility of the macromolecules and their fragments. The structure and properties of the complexes depend on the composition of the media as well as the method of introducing polyacids. It was found that it was possible to control the structure of such solutions by applying a mechanical of magnetic field. The compositions obtained can be used for producing anisotropic light-, electric-, and heat-sensitive film materials, as well as sensors of different types.Presented at the 10th International Conference on the Mechanics of Composite Materials (Riga, April 20–23, 1998).Institute of General and Inorganic Chemistry, Belarus Academy of Sciences, Minsk, Belarus. Translated from Mekhanika Kompozitnykh Materialov, Vol. 34, No. 3, pp. 413–424, May–June, 1998.     

A theoretical evaluation method for mechanical sealing integrity of cementing sheath

The sealing integrity of cement sheath directly affects the service life of oil and gas wells, and plays an important role in oil well operation and production. In this paper, the evaluation of sealing integrity of cement sheath was divided into two parts: the integrity of formation and cement sheath, and the integrity of cement sheath and casing. Based on the convergence-constraint theory, the effect of convergence stress generated by formation on cement slurry during the hardening process was considered. And the evaluation method for casing-cement-formation sealing integrity was established. In addition, a quantitative relationship between compressive strength of cement sheath and formation characteristic parameters was proposed to determine the cement-formation sealing integrity. Besides, the integrity evaluation method of casing-cement-formation combination was verified by tensile strength, compressive strength and plastic zone of cement. The field application analysis showed that this method is valid to predict the cement failure. During the cementing operation, the integrity of casing-cement-formation interface can be controlled by adjusting the properties of the cement sheath.