漂浮基双臂空间机器人姿态与末端抓手惯性空间轨迹协调运动的模糊滑模控制

本文讨论了载体姿态受控、位置不受控制的双臂空间机器人系统的控制问题.利用拉格朗日方法并结合系统动量守恒关系,建立了双臂空间机器人系统的非线性系统动力学模型.以此为基础,考虑到空间机器人系统结构的复杂性及其某些参数的变动性,根据具有较强鲁棒性的变结构控制理论,设计了双臂空间机器人载体姿态与两机械臂末端抓手惯性空间轨迹协调运动的滑模变结构控制方案.为了克服滑模变结构控制器抖振的缺点,附加设计了一个模糊控制器,以便根据系统的输出来动态调节滑模变结构控制器等速趋近率的系数,从而既确保了系统的快速响应而又消除了原有的抖振.系统数值仿真,证明了上述控制方案良好的控制效果.     

基于首超破坏机制的大跨斜拉桥抖振动力可靠性分析

分别采用泊松分布和马尔可夫过程，给出了在一次强风作用下以及在设计基准期内桥梁结构某一特定截面或节点的抖振动力可靠性分析方法。然后，考虑斜拉桥的结构特点及其承受风荷栽的具体情况，确定了以斜拉桥的主梁系统为研究对象的结构体系抖振动力可靠性分析模型。在此基础上，采用串联失效模式，建立了斜拉桥主梁系统抖振动力可靠性分析过程。本文采用有限元法分析结构的空气静力响应。为了快速、准确地计算结构的抖振响应，考虑气弹力与抖振力的联合作用以及多模态耦合效应，采用有限元法和虚拟激励法相结合分析结构的抖振响应。最后，以某大跨斜拉桥为工程背景，对其主梁系统进行了基于刚度要求的抖振动力可靠性分析。     

雷诺数效应对翼型抖振特性的影响

飞行器抖振是一种非线性气动弹性问题,当飞行器进入抖振阶段时,将会对飞行器的性能产生严重影响。而在跨声速条件下,激波附面层相互作用会诱导机翼抖振。本文开展了跨声速条件下翼型抖振特性雷诺数效应的实验研究,揭示了翼型跨声速抖振起始迎角、激波运动前缘边界、频谱特性、抖振频率与雷诺数变化的基本规律。结论如下:雷诺数变化会导致抖振起始边界的改变,对抖振起始迎角下的功率谱密度峰值有明显影响;随着雷诺数的增大,激波运动的前缘后移。雷诺数变化对抖振频率有明显影响,随着马赫数增大,雷诺数效应增强。     

桥梁多模态耦合抖振控制方法研究

目前已证实调谐质量阻尼器(TM D)可以有效控制桥梁抖振响应,并已在工程中得到应用。然而,传统桥梁抖振被动控制理论是基于单模态叠加SRSS法,无法考虑多模态参与作用和模态间气动耦合效应,本文基于Scan lan多模态耦合抖振理论和多重调谐质量阻尼器(M TM D)被动控制理论,提出一种桥梁多模态耦合抖振M TM D控制方法,该方法可以考虑多模态参与作用、模态间气动耦合效应和单模态中各模态位移分量的气动耦合,且对各TM D在主梁上的安装位置没有任何限制。本文最后采用时域仿真方法对该方法进行了验证,两者计算结果吻合良好,表明本文所提出的方法的正确性。     

安装固定气动翼板的大跨桥梁抖振分析

建立了安装固定气动翼板的大跨桥梁多模态耦合抖振分析框架，推演了作用在整个桥梁-气动翼板系统上的抖振力和自激力的显式表达式，考虑了多模态耦合效应．基于有限元法，作用在主梁-气动翼板系统上的抖振力转化为节点力，进一步得到作用在整个桥梁上的抖振力并导出了其功率谱密度矩阵；作用在主梁．气动翼板系统上的气弹自激力转化为节点力，并将其表达为气弹刚度矩阵和气弹阻尼矩阵．通过组集得到系统的运动方程，然后运用虚拟激励法在频域计算系统的抖振响应．以某大跨斜拉桥为例进行研究，结果表明：在主梁下方安装-对固定气动翼板后，主梁的扭转角位移、角加速度以及侧向加速度响应能够得到有效控制。     

基于滑模理论的建筑结构分散稳定控制

基于大系统分散控制思想,将大尺度高阶建筑结构系统分解为多个子结构系统;子结构之间的相互耦合作用视为有界广义力,得到以状态方程形式的子结构模型。利用滑模理论的抗摄动条件,设计具有全局稳定的子结构滑动模态轨迹,利用子结构系统局部状态实现全局稳定的控制力条件,并以参数ρi实现各子结构间的调节,建立稳定的分散控制格式。在控制算法中采用了准滑模控制方法,克服变结构滑动模态中的抖振影响。利用本文方法,对20层钢结构基准模型在地震激励下的控制进行设计并数值仿真,验证了该方法的有效性。     

基于虚拟激励法的大跨桥梁抖振内力分析

桥梁抖振内力分析是大跨桥梁抗风设计中的一项重要课题。目前，通常采用等效静风荷载的方法来计算桥梁抖振内力。本文将虚拟激励法应用到桥梁抖振内力分析中来，考虑多模态耦合效应，建立了直接应用随机振动方法计算桥梁抖振内力的快速算法。最后，以主跨为628m的某大跨斜拉桥为例进行了多模态耦合抖振内力分析，结果表明：高阶模态的参与将使主梁抖振内力增大，主梁抖振内力的峰因子介于3．4至4．0之间。     

飞机抖振问题研究进展

介绍了目前国内外对于飞机抖振问题研究的进展.主要介绍了目前国外对于飞机跨音速激波-附面层相互作用诱导的机翼抖振、低速大攻角下分离流诱导的机翼抖振、垂尾抖振的试验和理论研究方法、研究成果以及发展趋势.另外,也简单介绍了垂尾抖振减缓的几种方法,并对这些方法作了评述.     

基于模糊滑模控制的挠性航天器姿态机动及抖振抑制研究

针对挠性航天器姿态机动控制问题,设计了一种模糊滑模控制律。在原有的滑模控制基础上,用连续光滑的双曲正切函数代替了符号函数,并采用模糊控制对切换增益进行了改进,以抑制系统的抖振。考虑到挠性航天器初始阶段控制力矩过大的情况,引入了滞后因子,减小了控制力矩输出,避免了由此引起的挠性附件的振动问题。数值仿真结果表明:所设计的模糊滑模控制律不仅能够实现挠性航天器的姿态机动,而且有效抑制了挠性附件的抖振,具有更好的控制性能。     

大跨悬索桥三维非平稳耦合抖振分析

基于Priestley(1967)演变功率谱模型，并采用Lin和Yang(1983)的建议，建立了脉动风速的非平稳功率谱模型。依据此模型，采用三维有限元法，建立了大跨桥梁非平稳耦合抖振运动方程。然后，将虚拟激励法和精细时程积分法相结合，建立了求解桥梁三维非平稳耦合抖振运动方程的快速算法。以某大跨悬索桥为例，分析了该桥的非平稳耦合抖振响应，并与平稳耦合抖振响应进行了比较。计算结果表明：随着脉动风速平稳部分持时的增大，非平稳抖振分析结果逐渐收敛于平稳抖振分析结果；但若脉动风速的平稳部分持时较短，非平稳抖振分析结果将低于平稳抖振分析结果。     

No-chatter variable structure control for fractional nonlinear complex systems

This paper concerns the problem of robust control of uncertain fractional-order nonlinear complex systems. After establishing a simple linear sliding surface, the sliding mode theory is used to derive a novel robust fractional control law for ensuring the existence of the sliding motion in finite time. We use a nonsmooth positive definitive function to prove the stability of the controlled system based on the fractional version of the Lyapunov stability theorem. In order to avoid the chattering, which is inherent in conventional sliding mode controllers, we transfer the sign function of the control input into the first derivative of the control signal. The proposed sliding mode approach is also applied for control of a class of nonlinear fractional-order systems via a single control input. Simulation results indicate that the proposed fractional variable structure controller works well for stabilization of hyperchaotic and chaotic complex fractional-order nonlinear systems. Moreover, it is revealed that the control inputs are free of chattering and practical.     

基于反演高阶滑模的飞行器最优末制导律

针对传统最优末制导律鲁棒性能较弱,且对参数摄动及外扰敏感的不足,而滑模控制对扰动具有较强鲁棒性的优点,提出一种新的基于反演准连续高阶滑模的最优末制导律,其中反演控制能够有效保证系统全局稳定性,而准连续高阶滑模控制则用于消除扰动影响。为了去除抖振效果,引入自适应超螺旋算法在线更新控制参数以消除符号函数导致的高频抖振影响。仿真结果表明:飞行器在该末制导律导引下,弹目视线角速率快速收敛,从而保证飞行器有很高的命中精度;鲁棒性较强;能够较好的满足约束条件要求。     

拦截高超声速飞行器的三维有限时间制导律设计

由于高超声速飞行器具有飞行速度快、机动能力强等特点,因此,传统的制导方式难以保证拦截弹拦截高超声速飞行器时的制导精度。为了减小弹目相对速度,降低对拦截弹的过载能力要求,按照前向制导方式,设计了有限时间收敛的三维前向滑模制导律。该制导律采用了连续的快速双幂次趋近律,不仅保证收敛速度快,同时削弱了传统制导律中存在的抖振现象。在此基础上为了处理系统扰动的上界未知的问题,又设计了自适应滑模制导律,该制导律既可以处理未知上界的外部扰动又可以保证第一种制导律所具有的良好特性。运用李雅普诺夫稳定性理论对所设计的滑模制导律进行了理论证明,最后,通过数值仿真验证了所设计制导律的有效性及优越性。     

Global sliding mode control and application in chaotic systems

This paper is concerned with the stabilization problem for a class of nonlinear systems. Using the global sliding mode control approach, a novel robust control law is established to make the state of system stable and to improve the robustness and the stability of system. A new reaching law is introduced to reduce the chattering. Finally, the method is applied to chaotic systems and an example of the chaotic system is given to illustrate the advantage of the proposed method.     

Forced sliding mode control for chaotic systems synchronization

Synchronization of chaotic systems is considered to be a common engineering problem. However, the proposed laws of synchronization control do not always provide robustness toward the parametric perturbations. The purpose of this article is to show the use of synergy-cybernetic approach for the construction of robust law for Arneodo chaotic systems synchronization. As the main method of design of robust control, the method of design of control with forced sliding mode of the synergetic control theory is considered. To illustrate the effectiveness of the proposed law, in this article it is compared with the classical sliding mode control and adaptive backstepping. The distinctive features of suggested robust control law are the more good compensation of parametric perturbations (better performance indexes—the root-mean-square error (RMSE), average absolute value (AVG) of error) without designing perturbation observers, the ability to exclude the chattering effect, less energy consuming and a simpler analysis of the stability of a closed-loop system. The study of the proposed control law and the change of its parameters and the place of parametric perturbation’s application is carried out. It is possible to significantly reduce the synchronization error and RMSE, as well as AVG of error by reducing some parameters, but that leads to an increase in control signal amplitude. The place of application of parametric disturbances (slave or master system) has no effect on the RMSE and AVG of error. Offered approach will allow a new consideration for the design of robust control laws for chaotic systems, taking into account the ideas of directed self-organization and robust control. It can be used for synchronization other chaotic systems.

     

Finite time integral sliding mode control of hypersonic vehicles

This study investigates the tracking control problem for the longitudinal model of an airbreathing hypersonic vehicle (AHV) with external disturbances. By introducing finite time integral sliding mode manifolds, a novel finite time control method is designed for the longitudinal model of an AHV. This control method makes the velocity and altitude track the reference signals in finite time. Meanwhile, considering the large chattering phenomenon caused by high switching gains, an improved sliding mode control method based on nonlinear disturbance observer is proposed to reduce chattering. Through disturbance estimation for feedforward compensation, the improved sliding mode controller may take a smaller value for the switching gain without sacrificing disturbance rejection performance. Simulation results are provided to confirm the effectiveness of the proposed approach.     

Terminal sliding mode control for aeroelastic systems

An aeroelastic system is a nonlinear system with two freedoms, i.e., the plunge displacement and the pitch angle, in a dynamic system model. A chaos effect or a limit cycle oscillation is presumably attributed to the nonlinear effect of the pitch angle mentioned above or the interaction between the aerodynamic behaviors. It is that a single trailing edge input in an aeroelastic system is employed as a way to suppress the limit cycle oscillation with an exclusive choice between the plunge displacement and the pitch angle for a control law design. Consequently, the remaining inevitably turns into an internal dynamics, whose stability is adversely affected by the flight speed and structure parameters, a problem improved by no means using a singe control input design. Toward this end, this work presents a controller design criterion with multiple input channels for both the leading and training edges to remove the uncertainty effect of internal dynamics, and render more room for the response design of the plunge displacement as well as the pitch angle. Mostly due to external disturbance and unknown uncertainty, there is a deviation between the intended and implemented system performances for a robust control design, a mainstream research issue in the modern control. As a consequence of a sliding mode control utilized here, the limit cycle oscillation suffered in an aeroelastic system is removed effectively by the use of a terminal sliding mode control, and the chattering phenomenon seen in the control signal is hence eliminated by his method. It is seen from simulations that the control system is stably assured to reach the target within a limited time frame with an addition of a saturation function to the control law.     

Control structure with disturbance identification for Lagrangian systems

A new control structure for a class of uncertain Lagrangian systems that solves the regulation and tracking control problems is proposed. This structure has good robustness properties, similar to sliding-mode-type controllers; and is free from chattering. The control structure is based on a discontinuous, robust observer, which displays a second-order sliding mode yielding an exponential convergence to the state of the plant in spite of the existence of non-vanishing disturbances and parameter uncertainties. At the same time, with the aid of a low-pass filter, this observer is employed to estimate the perturbations affecting the plant. This disturbance estimation is used to compensate the perturbations acting on the plant, improving the controller robustness. The performance of the proposed control structure is illustrated numerically and experimentally.     

基于有限时间收敛的双臂空间机器人捕获卫星主动对接力/位姿阻抗控制

针对双臂空间机器人捕获卫星主动对接力/位姿阻抗控制进行了研究.为防止捕获过程中机械臂末端执行器与卫星接触、碰撞时产生的冲击载荷对机器人关节造成冲击破坏,在各关节电机与机械臂之间加入了一种弹簧阻尼缓冲机构.该机构可通过弹簧实现冲击力矩的卸载,阻尼器则用于因弹簧引起的柔性振动的抑制.为解决捕获过程中的非完整动力学约束及捕获后混合体系统的协调控制问题,结合牛顿第三定律、捕获点的速度约束及闭链几何约束,获得捕获后混合体系统的动力学方程,且通过动量守恒关系计算碰撞冲击效应与碰撞冲击力.通过分析对接装置在载体坐标系下的运动学关系,建立对接装置相对载体的运动雅可比矩阵,并基于此建立基于力的二阶线性阻抗模型,实现对接装置输出力的精确控制.考虑到主动对接操作过程要求控制器具有收敛速度快,控制精度高的特点,通过结合终端滑模与超扭滑模的特点,提出一种非奇异快速终端滑模阻抗控制策略.该策略即能实现主动对接操作中位姿与输出力的快速响应,又能有效地抑制滑模的抖振以保证控制精度.通过Lyapunov定理证明系统的稳定性;利用数值模拟验证缓冲装置的抗冲击性能及所提阻抗控制策略的有效性.     

An adaptive fuzzy sliding mode controller for MEMS triaxial gyroscope with angular velocity estimation

In this paper, an adaptive fuzzy sliding mode control (AFSMC) for Micro-Electro-Mechanical Systems (MEMS) triaxial gyroscope is proposed. First, a novel adaptive identification approach with sliding mode controller which can identify angular velocity and other system parameters is developed. And in order to reduce the chattering, an AFSMC is designed to approximate the upper bound of the uncertainties and external disturbances. Based on Lyapunov methods, these adaptive laws can guarantee that the system is asymptotically stable. Numerical simulations are investigated to verify the effectiveness of the proposed AFSMC scheme.