欠驱动刚体航天器姿态运动规划的遗传算法

研究欠驱动刚体航天器姿态的非完整运动规划问题．航天器利用3个动量飞轮可以控制其姿态和任意定位,当其中一轮失效,航天器姿态通常表现为不可控．在系统角动量为零的情况下,系统的姿态控制问题可转化为无漂移系统的运动规划问题．基于优化控制理论,提出了求解欠驱动刚体航天器的姿态运动控制遗传算法,并且数值仿真表明：该方法对欠驱动航天器姿态运动的控制是有效的．     

考虑障碍约束的非完整运动规划

本文针对非完整移动机器人的链式形式，在存在障碍约束时提出了一种运动规划方法,由于其链式形式可以方便地采用分段常值输入和多项多输入来实现其运动规划，因此在满足一定的性能指标的前提下可以找到了种最优的控制律来避开障碍物而到达目标，领导的结果也证明了该方法的有效性。     

欠驱动刚体航天器姿态机动滑模控制研究

针对欠驱动刚体航天器的姿态机动控制问题,提出一种滑模变结构姿态控制器的设计方法.首先给出3轴稳定的欠驱动航天器姿态动力学和运动学模型,分析其模型特点;然后,设计了欠驱动刚体航天器的渐近稳定滑模控制律,并证明了其李雅普诺夫意义下的全局渐近稳定性.最后的仿真结果表明,该方法能够有效实现欠驱动航天器的姿态控制,且系统具有全局稳定性和鲁棒性.     

轮式移动机器人非完整运动规划的遗传算法

本文讨论轮式移动机器人非完整运动的最优规划问题。利用系统的非完整特性 ,将轮式移动机器人运动规划转化为非线性系统最优控制问题。在最优控制中引入遗传算法 ,替代传统的牛顿迭代方法 ,提出基于遗传算法的非完整运动规划最优控制数值方法。通过仿真计算 ,验证了该方法的有效性和可行性。     

考虑动力学模型的非完整移动机器人运动规划

针对非完整移动机器人,在运动学和动力学约束条件下提出了一种运动规划方法.在工作环境已知情况下,根据移动机器人的动力学模型和无打滑非完整运动约束条件,采用立方螺线对规划的路径光滑化,从而使得移动机器人易于跟踪所规划的路径,同时考虑了移动机器人速度的限制.最后采用Matlab对该算法进行了数值仿真,结果表明该方法是有效的.     

基于传感器的非完整移动机器人运动规划

针对非完整移动机器人在未知室内环境中提出了一种路径规划方法, 通过利用传感器对周围环境的探测和实时处理传感器数据, 以及所设计的目标寻找函数, 可以有效地完成其运动规划. 该方法能够确保移动机器人在无障碍物区或障碍物对机器人不构成危险时加速前进, 在障碍物区能够慢速绕过, 从而使得移动机器人快速且安全地到达目标位置, 仿真的结果证明了该方法的有效性.     

非完整移动机器人鲁棒运动规划

非完整移动机器人利用传感器可以解决不确定性模型和未知环境中的许多问题. 利用移动机器人上配备的传感器的信息组合提出了一种在线视点寻求算法, 结合移动机器人的运动方程和传感器的量测方程采用扩展Kalman估计来对移动机器人的位置进行修正, 以降低运动的不确定性, 从而得到一种鲁棒的规划算法, 仿真的结果证明了上述方法是行之有效的.     

二维完整配置下刚性航天器姿态角速度的渐近镇定

讨论了以非完整配置的单向推力器系统为执行机构时,刚性航天器姿态角速度的镇定问题.针对一类特殊的有扰量非完整配置的情况--共面扰量二维完整配置,基于滑动控制律实现了姿态角速度的镇定.仿真结果证实了所述方法的有效性.     

基于遗传算法的欠驱动机器人运动规划

研究了平面欠驱动机器人的非完整运动规划问题,建立欠驱动机器人系统动力学模型,提出了一种利用遗传算法(GA)解决欠驱动机器人运动规划的方法。引入部分稳定控制器的思想,提出基于能量最优的评价函数,利用遗传算法对评价函数进行离线优化,得到有关部分稳定控制器的切换规则。此方法可以推广到任意平面欠驱动机器人的规划问题上,以平面3R欠驱动机器人为研究对象进行了数值仿真,仿真结果验证了该方法的有效性。     

采用碰撞测试和回归机制的非完整约束机器人快速扩展随机树运动规划

本文提出一种改进的快速扩展随机树(rapidly-exploring random trees,RRT)运动规划方法,用于非完整微分约束下的机器人运动规划.针对类似目标偏好与双向RRT(bi-directional RRT,bi-RRT)等目标区域导向的RRT运动规划所存在的局部极小问题,结合回归检测与碰撞检测机制,设计了一种碰撞检测与回归机制(collision-test and regression mechanism,CR)机制.该方法使得机器人在规划过程中能获取到全局障碍物信息,从而避免对已扩展节点的重复搜索,以及重复对边缘节点的回归测试和避障检测.该机制使得机器人可加快跳出局部极小区域,提高运动规划实的时性.将改进的RRT运动算法在容易产生局部极小值的环境中仿真测试,结果表明该算法在不显著影响其他性能的前提下,可以明显提高规划的实时性.     

输入饱和受限下的刚体飞行器姿态系统的有限时间镇定

研究存在输入饱和受限下的飞行器姿态控制问题, 提出一种有限时间姿态镇定方案. 针对基于修改的Rodriguez 参数模型的飞行器姿态控制系统, 基于齐次性理论和饱和控制器设计方法, 并充分利用系统的模型结构特征, 设计一类饱和的有限时间姿态控制器, 使得姿态可以在有限时间内被镇定到平衡点. 仿真结果验证了所设计姿态控制器的有效性.

     

Distributed fixed‐time attitude coordination control for multiple rigid spacecraft

In this paper, the fixed‐time attitude coordination control for multiple rigid spacecraft under an undirected communication graph is investigated. By using the backstepping technique, the distributed fixed‐time observer, and the method of “adding a power integrator,” a distributed fixed‐time attitude coordination control law is designed for a group of spacecraft. The proposed control scheme is nonsingular and can guarantee a group of rigid spacecraft simultaneously tracking a common desired attitude within fixed time even when the time‐varying reference attitude is available only to a subset of the group members. Rigorous analysis is provided to show that the attitude consensus tracking errors can converge to the origin in finite time which is bounded by a fixed constant independent of initial conditions. Numerical simulations are carried out to demonstrate the effectiveness of the proposed control law.     

飞轮安装偏差的过驱动航天器有限时间姿态控制

针对反作用飞轮安装存在偏差的过驱动航天器姿态跟踪问题, 提出一种有限时间姿态补偿控制策略. 通过设计自适应滑模控制器保证实现对不确定性转动惯量与外部干扰的鲁棒控制, 同时实现对飞轮安装偏差的补偿控制, 并应用Lyapunov 稳定性理论证明了该控制器能够在有限时间内实现姿态跟踪控制. 最后, 将该控制器应用于某型航天器的姿态跟踪控制, 仿真结果验证了所提出方法的有效性.     

基于飞轮的欠驱动航天器姿态控制器设计

在以飞轮作为姿态控制执行机构的航天器中,如果部分飞轮发生故障而使得航天器欠驱动时,姿态控制性能会急剧下降.本文对两个匕轮的刚性航天器,研究了姿态控制问题.在零动量的假设下,利用Backstepping方法,为欠驱动姿态控制系统设计了一个新型的姿态控制器.设计过程分两步进行:首先,根据姿态运动学模型,设计出可使航天器姿态全局渐近稳定的控制角速率;然后,根据姿态动力学模型,得到使航天器姿态全局渐近稳定的控制力矩.该控制器为非连续控制器,可使航天器姿态误差全局一致渐近收敛为零,并使系统具有良好的动态性能.计算机仿真表明,本文所设计出的控制器是可行的.     

Global finite-time attitude consensus tracking control for a group of rigid spacecraft

The problem of finite-time attitude consensus for multiple rigid spacecraft with a leader–follower architecture is investigated in this paper. To achieve the finite-time attitude consensus, at the first step, a distributed finite-time convergent observer is proposed for each follower to estimate the leader's attitude in a finite time. Then based on the terminal sliding mode control method, a new finite-time attitude tracking controller is designed such that the leader's attitude can be tracked in a finite time. Finally, a finite-time observer-based distributed control strategy is proposed. It is shown that the attitude consensus can be achieved in a finite time under the proposed controller. Simulation results are given to show the effectiveness of the proposed method.     

Spin-axis stabilisation of underactuated rigid spacecraft under sinusoidal disturbance

Spin-axis stabilisation of spacecraft is a problem of partial stabilisation for non-linear dynamical systems. In this article the analysis of spin-axis stabilisation of underactuated rigid spacecraft in the presence of sinusoidal disturbances is presented. By using the Euler–Poisson form to describe the equations of motion and assuming the disturbances in three axes are decoupled with known frequencies, the paper first studies the problem of the underactuated rigid axisymmetric spacecraft by applying the internal modal principle to eliminate the sinusoidal disturbance. Then the paper turns to the more complicated asymmetric spacecraft, where the boundedness of the angular velocity for the underactuated axis is analysed in detail. The paper also proves the global asymptotic stability of the closed-loop systems for both axisymmetric spacecraft and asymmetric spacecraft by combining the Lyapunov direct method with the LaSalle's theorem. The simulation results show that the proposed control law is effective in the presence of sinusoidal disturbance.     

Extended state observer-based attitude fault-tolerant control of rigid spacecraft

In this paper, a novel fault-tolerant attitude tracking control is proposed for a rigid spacecraft with uncertain inertia matrix, actuator faults, actuator misalignment and external disturbances. The uncertainty of the inertial matrix is caused by the rotation of solar panels, payload movement and fuel consumption, and actuator faults, which include partially failed and completely failed actuators. A novel extended state observer is proposed to estimate the total uncertainties and a fast nonsingular terminal sliding-mode control scheme is proposed to get a faster, higher control precision. Strict finite-time convergence and the concrete convergence time are given. Finally, all the states of the closed-loop system are guaranteed to converge to the corresponding region in a finite time by choosing appropriate parameters. Simulation and comparison results further show the effectiveness and advantages of this method.     

A geometrical approach to the motion planning problem for a submerged rigid body

The main focus of this article is the motion planning problem for a deeply submerged rigid body. The equations of motion are formulated and presented by use of the framework of differential geometry and these equations incorporate external dissipative and restoring forces. We consider a kinematic reduction of the affine connection control system for the rigid body submerged in an ideal fluid, and present an extension of this reduction to the forced affine connection control system for the rigid body submerged in a viscous fluid. The motion planning strategy is based on kinematic motions; the integral curves of rank one kinematic reductions. This method is of particular interest to autonomous underwater vehicles which cannot directly control all six degrees of freedom (such as torpedo-shaped autonomous underwater vehicles) or in case of actuator failure (i.e. under-actuated scenario). A practical example is included to illustrate our technique.