仿蛙跳跃机器人起跳任务规划与控制

研究跳跃机器人起跑规划问题,针对仿蛙跳跃机器人在起跳过程中脚掌与地面之间形成的欠驱动约束和特定的起跳任务,为提高系统性能,提出了一种在任务空间内实现给定起跳任务要求的路径运动规划控制.利用部分反馈线性化(PFL)将仿蛙跳跃机器人系统起跳动力学方程中的非线性部分线性化,设计了滑模变结构控制器对仿蛙跳跃机器人在起跳阶段的质心轨迹进行跟踪控制.结果表明滑模控制器能够使质心轨迹精确地跟踪给定轨迹,解决了仿蛙跳跃机器人的起跳任务优化控制问题,验证了提出的任务空间控制方法用于仿蛙跳跃机器人起跳任务规划的可行性.     

无穷维时滞系统的变结构控制

本文在Banach空间研究了无穷维时滞系统的变结构控制问题,给出了滑动模态的稳定性条件,滑动模态的到达条件和变结构控制的一般形式,最后用分布参数系统变结构控制的例子说明了方法的有效性。     

空间机器人分布式滑模变结构控制方法

针对空间机器人的动力学特性和星载控制系统的结构特点,分别基于干扰上确界和比例切换,设计了2种分布式滑模变结构控制方法,以实现在存在不确定干扰和关节摩擦力矩情况下基座姿态和关节运动的综合控制.首先给出了空间机器人的动力学模型和关节低速摩擦力矩模型,并以两自由度空间机器人为例,介绍了2种分布式滑模变结构控制方法的推导过程.通过仿真实验,对2种控制方法进行了对比,结果表明分布式变结构控制方法在简化算法的同时,能够保证系统控制性能,并对干扰和参数变化具有较强的鲁棒性.     

基于遗传优化的水平欠驱动机械臂分层滑模控制

针对二自由度水平欠驱动机械臂系统,提出一种基于等效控制理论和李雅普诺夫反馈函数法的分层滑模变结构控制方法.同时,为解决由于欠驱动系统控制缺少通用的参数计算方法而产生控制精度低的问题,提出了针对水平欠驱动系统的遗传算法在全局参数空间进行全参数寻优的改进控制方法.仿真结果表明了该方法的有效性,并且优化后的控制器具有较好的适应性和控制效果.     

基于应用层逻辑的分布式集群架构在生物计算中的应用

本文提出一种新型的服务器集群构架,用于解决生物信息学计算中所使用的分布式集群系统的负载平衡问题.该结构基于任务的应用层逻辑对不同种类的任务进行分类,使得同类任务运行在固定的计算机子群上,从而回避了不同类型负载之间的比对问题,简化了负载平衡操作的难度.并且,此结构充分利用了计算机的时间局部性和空间局部性原理,提高了整个系统运行的效率.     

基于隐Lyapunov 函数的软变结构控制: 一种控制策略

针对变结构控制的抖振问题,基于隐Lyapunov函数,提出一种新的控制策略:软变结构控制.首先给出软变结构控制的定义和控制器的构造方法;然后设计软变结构控制器和隐Lyapunov区域,给出了控制不受限和控制受限两种情形的软变结构控制,同时,分析了带有状态观测器的软变结构控制.软变结构控制是无滑模的变结构控制,能有效削弱抖振,保持高速调节速度和缩短趋近时间.仿真实例表明了该方法的有效性和可行性.     

多输入离散时滞系统的变结构控制设计

研究多输入时滞离散系统的变结构控制问题．首先将离散时滞系统简化为无时滞离散系统，在此基础上提出一种新的变结构控制设计算法．该算法能使从空间任意点出发的运动在有限时间内准确到达并保持在切换面上，不发生切换面的穿越，有效地消除了抖振．数值计算和仿真结果表明了该方法的有效性．     

空间系绳系统展开的滑模变结构控制

为了增强空间系绳系统展开过程的抗干扰性,本文提出了空间系绳系统展开运动轨迹跟踪的滑模变结构控制方法.考虑大气摄动和无模型摄动建立了空间系绳系统展开运动动力学模型.基于遗传算法,针对两阶段展开方式,采用最优振荡阻尼张力控制律和等分时张力控制律设计了展开运动标称轨迹.为了实现轨迹的鲁棒跟踪,采用考虑展开长度的等效控制和连续函数幂次趋近律切换控制设计了滑模变结构控制器.仿真结果表明,所提出的控制方法有效增强了空间系绳系统展开运动的动态性能及鲁棒性.     

基于期望轨迹补偿的机器人鲁棒自适应控制

针对机器人存在的参数不确定性和外扰的问题,提出了一种基于期望轨迹补偿和自适应控制的方法,在传统自适应控制方法的基础上,结合变结构控制方法,设计了一种新的控制策略.该方法采用期望轨迹补偿,离线计算回归矩阵,可以有效节约控制系统在线计算的时间,实时性好,并利用变结构思想补偿非线性摩擦和外界干扰,利用lyapunov直接法分...     

二阶分布参数系统的变结构控制

本文研究了Hilbert空间中的二阶分布参数系统的变结构控制问题,给出了系统存在滑动模的条件;并研究了系统的有限维近似问题,从而为柔性机器人等分布参数系统的变结构控制奠定了理论基础。     

Experimental evaluation of a variable structure controller for constrained robots

In this paper, a variable structure control scheme for constrained robots is developed. This control law ensures the asymptotic convergence of the position errors to zero and also the boundedness of the force tracking error. The control scheme requires a few online computations and thus can be easily implemented. The proposed control law does not require measurements of the joint accelerations or the estimation of the derivative of the force. Experimental results are presented to verify the theoretical developments.     

Robust variable structure and switching-Σ adaptive control ofsingle-arm dynamics

In this paper, the variable structure control (VSC) and switching-σ adaptive laws are used to design a new robust controller for single-arm rigid manipulators in joint space. The controller is shown to be robust with respect to bounded disturbance. More particularly, a bound on the tracking error is determined and shown to be smaller than those resulting from the VSC) law proposed in Slotine and Li as well as the robust adaptive control law derived in Reed and Ioannou. The simulations also show that the proposed control law has better tracking precision performance than the VSC law and switching-σ adaptive control law. It can also suppress chattering and maintain good tracking precision even if actuator unmodeled dynamics are considered     

Robust adaptive control of an underactuated free-flying space robot under a non-holonomic structure in joint space

This paper introduces a robust adaptive control scheme for an underactuated free-flying space robot under non-holonomic constraints. An underactuated robot manipulator is defined as a robot that has fewer joint actuators than the number of total joints. Because, if one of the joints is out of order, it is so hard to repair the joint, especially in space, the control of such a robot manipulator is important. However, it is difficult to control an underactuated robot manipulator because of the reduced dimension of the input space, i.e. the non-holonomic structure of the underactuated system. The proposed scheme does not need to assume that the exact dynamic parameters must be known. It is analysed in joint space to control the underactuated robot mounted on the space station under parametric uncertainties and external disturbances. The simulation results have shown that the proposed method is very feasible and robust for a two-link planar free-flying space robot with one passive joint.     

Chattering phenomena in discontinuous control systems

The reduction of chatter in variable structure control (VSC) systems is considered. In this scheme the time derivative of the control law is discontinuous on a suitable manifold of an augmented order state space. For the case of differential equations with uncertain RHS, the proposed scheme maintains the robustness properties of classical VSC if an estimator of inaccessible state components is introduced. A separation property, together with the convergence of the proposed estimator are proved. Some simulation results relating to an induction motor control problem are finally presented.     

A bio‐inspired approach for regulating and measuring visco‐elastic properties of a robot arm

This work focuses on interaction control of robot manipulators in unstructured environments, with special regard for situations of unpredictable contact/noncontact transitions. It is basically addressed to those environments where a high level of robot adaptability is required and no information on the geometry of the environment is available. By pointing out the main limitations of standard interaction control schemes in managing situations of contact/noncontact transitions, this paper proposes a new control solution that is inspired by the biological model of motor control in voluntary movements. It consists of a combination of a feedforward loop and a proportional‐derivative plus gravity compensation control in the feedback loop. The control law is named coactivation‐based compliance control in the joint space since a unique function, called coactivation function, is evaluated for regulating robot visco‐elasticity in an unpredictably variable environment. It resumes the mechanism of adjustable visco‐elastic properties acting on the agonist and antagonist muscles of a human arm. The work also proposes a methodology for evaluating performance of interaction control schemes that is based on stiffness graphical representation through ellipses. The method replicates the experimental setup used in neuroscience to measure stiffness in human limbs. It is regarded as a powerful tool for evaluating robot behavior over space and time, since it allows both a visual representation of stiffness variation during motion and a quantitative measure of robot performance. It is shown how the method can be used to evaluate a control scheme and how it can provide indications to improve a control law. In this paper, an application to the standard compliance control in the joint space and the coactivation‐based compliance control is presented. © 2005 Wiley Periodicals, Inc.     

Robust Motion Control for Robotic Assembly Tasks using Variable Structure Control Scheme

The success of robot assembly tasks depends heavily on its ability to handle the interactions which take place between the parts being assembled. In this paper, a robust motion-control method is presented for robot manipulators performing assembly tasks in the presence of dynamic constraints from the environment. Using variable structure model reaching control concept, the control objectives is first formulated as a performance model in the task space. A dynamic compensator is then introduced to form the switching function such that the sliding-mode matches the desired model. A simple variable structure control law is suggested to force the system to reach and stay on the sliding mode so that the specified model is achieved.The proposed method is applied to control the prismatic joint of a selective compliance assembly robot-arm type robot for the insertion of printed circuit board into an edge connector socket. Various amounts of interaction forces are generated during the operation. Experimental and simulation results demonstrated the performance of the variable structure model reaching control approach. In comparison, it is shown that the popular position controllers such as proportional plus derivative control and proportional plus derivative with model-based feedforward control are not suitable for achieving good trajectory tracking accuracy in assembly tasks which experience potential interaction force.     

再入飞行器变结构姿态控制律设计与仿真

研究飞行器再入问题,以美国X-34技术验证机为对象,提出了一种再入飞行器变结构姿态控制算法。为提高姿态控制的精度,通过设计内外双环控制器,并选择适当的趋近律和符号函数连续化方法来解决由于变结构控制带来的抖振问题。同时基于X-34反作用控制系统(RCS)配置方案给出了一种RCS控制模式。由于RLV存在两套姿态控制执行机构与气动舵面,提出了一种基于动压调节的混合控制策略。最后通过Matlab/Simulink仿真计算验证了在标称状态与加入扰动时的控制算法的有效性,具有良好的跟踪性能和强鲁棒性。     

Variable structure trajectory control of an elastic robotic arm

This article introduces a variable structure system scheme to control the end effector trajectory of a two-link flexible robotic arm. Because control of the actual tip position leads to unstable zero dynamics, control of points in the neighborhood of the tip is considered. An output is chosen as the sum of the joint angle and tip elastic deformation times a constant factor for each link. For the chosen output, a discontinuous output control law is derived based on the variable structure theory. The control law thus derived accomplishes the desired trajectory tracking of the output. A linear stabilizer is designed using the pole assignment technique for the final capture of the terminal state and stabilization of the elastic modes. Simulation results are presented to show that in the closed-loop system large maneuvers can be performed in the presence of payload uncertainty, thereby exhibiting the robustness of the controller.     

一种基于操作空间的操作器分散自适应控制方法

本文提出了一种操作器分散自适应阻力控制方法．这种方法不要求知道操作器动态模型的结构和参数，采用分散控制的形式，可以对各自由度单独进行控制，因此计算简单有效，具有一定的容错能力，控制系统有较好的暂态性能，由于控制律以操作空间坐标形式描述，适合于具有冗余自由度的操作器的控制．计算机仿真表明了该方法的良好的控制效果     

Operating robot manipulators through kinematic singularities using a continuously sliding mode control

Planning the motion of end-effectors of robot manipulators can be carried out more directly in the Cartesian space compared to the joint space. Yet, Cartesian paths may include singular configurations where conventional control schemes suffer from excessive joint velocities and loss of tracking accuracy. The difficulties arise because the Jacobian matrix that is used to establish a linear relation between the velocities in the task and joint spaces loses rank at singularities. The problem can be resolved by using a local second-order approximation of robot kinematics for the joint velocities, which is called Resolved Motion Quadratic Rate Control. In this article, we present a control strategy based on this approach and a recently developed variable structure control scheme. The controller receives Cartesian inputs whenever the manipulator is outside the singular domain. Otherwise, it uses resolved motion quadratic rate control to compute the required joint inputs. Numerical simulation is performed to show that the proposed control scheme provides accurate tracking of the desired motion without inducing excessive control activity when operating robot manipulators through singular configurations. © 1994 John Wiley & Sons, Inc.