考虑几何约束的AUV回收路径规划

结合3次B样条的曲率连续特性和遗传算法的全局搜索特性,提出了一种适合欠驱动AUV(自治水下机器人)的回收路径规划方法.算法给出连接始末位置的光滑3维路径,适用于AUV回收的归航阶段,能够保证AUV以合适的姿态进行后续的导引对接.首先,分析了AUV的欠驱动特性带来的几何约束问题,包括任务终端约束和运动约束.其次,根据B样条曲线的特性确定通过选取控制点序列来给出3维路径曲线的思路.第一步采用样板的方式确定一部分控制点使曲线满足终端约束条件,第二步将AUV的回转和升沉运动约束写入遗传算法,通过对解空间的启发式自适应搜索确定中间控制点,两部分控制点所决定的曲线满足所有的几何约束条件.最后,针对路径的生成和跟踪,设计了半物理动力学仿真试验,从几何的角度对比AUV航迹和路径.结果显示,路径与AUV的运动能力具有很好的匹配特性,能够保证跟踪结束时AUV的位置和姿态满足导引对接阶段的要求.     

Robust global uniform asymptotic stabilization of underactuated surface vessels with unknown model parameters

The full‐state stabilization scheme is proposed for the control of an underactuated surface vessel with unknown modeling parameters. By knowing only the upper/lower bounds of model parameters, the designed controller is the first one able to globally uniformly asymptotically stabilize all the states of the vessel to zero. The virtual surge velocity control law is first derived, which makes the Lyapunov function at the kinematic level non‐increasing, irrelevant to the yaw velocity, leaving a freedom for choosing the virtual yaw velocity control law to stabilize the other state variables. After finishing the design of virtual velocity law, the back‐stepping approach and the Lyapunov redesign technique are combined to obtain the actual force/torque control law despite parameter uncertainties. Simulation examples are given to illustrate the effectiveness of the proposed control law, showing that all the states and the control inputs are globally uniformly asymptotically convergent to zero under parameter uncertainties and are globally bounded under unknown external bounded disturbances. Copyright © 2013 John Wiley & Sons, Ltd.     

Tracking and load sway reduction for double‐pendulum rotary cranes using adaptive nonlinear control approach

Because of the existence of rotational boom motion, the load sway characteristics is more complex. In particular, when the sway presents double‐pendulum phenomenon, the design of the controller is more challenging. Furthermore, the uncertain parameters and external disturbances in crane system make it difficult for traditional control methods to obtain satisfactory control performance. Hence, this paper presents an adaptive nonlinear controller based on the dynamic model of double‐pendulum rotary crane. Unlike a traditional method, the proposed one does not need to linearize the crane system for controller design; therefore, the control performance can be guaranteed even if the system states are far away from the equilibrium point. By using Lyapunov technique and LaSalle's invariance theorem, it is strictly proved that the whole control system is asymptotically stable at the equilibrium point. The effectiveness of the presented controller is demonstrated via comparative simulations.     

TORA系统基于自调节滑模干扰补偿器的解耦滑模控制

针对欠驱动TORA系统,提出一种基于自调节滑模干扰补偿器的解耦滑模控制方法。所提出的控制方法无需系统不确定性上界的先验信息,对于系统不确定性具有良好的适应性。该控制方法包括设计一种自调节滑模干扰补偿器和一种新型的双幂次趋近律,所设计的自调节滑模干扰补偿器能够利用切换增益自适应算法准确逼近上界未知的系统不确定性,所提出的新型双幂次趋近律能够保证系统状态的快速趋近并抑制控制器的高频抖动。采用Lyapunov稳定性理论证明闭环控制系统的稳定性,并通过数值仿真实验验证所提出的控制方法的有效性。     

欠驱动航天器姿态稳定的非线性控制

针对欠驱动航天器姿态稳定的非线性控制设计问题,给出了欠驱动航天器姿态运动的运动学方程和动力学方程,并将姿态四元数和角速度整合,引进分段连续变量和相应的时变函数,提出周期性连续时变反馈控制律,使欠驱动航天器姿态达到稳定状态.数值仿真实验结果表明了所设计控制律的有效性.     

A five-fingered underactuated prosthetic hand： hardware and its control scheme

A five-fingered underactuated prosthetic hand controlled by surface EMG (electromyographic) signals is presented in this paper. The prosthetic hand was designed with simplicity, lightweight and dexterity on the requirement of anthropomorphic hands. Underactuated self-adaptive theory was adopted to decrease the number of motors and weight. The control part of the prosthetic hand was based on a surface EMG motion pattern classifier which combines LM-based (Levenberg-Marquardt) neural network with the parametric AR (autoregressive) model. This motion pattern classifier can successfully identify the flexions of the thumb, the index finger and the middle finger by measuring the surface EMG signals through two electrodes mounted on the flexor digitorum profundus and flexor pollicis longus. Furthermore, via continuously controlling a single finger's motion, the five-fingered underactuated prosthetic hand can achieve more prehensile postures such as power grasp, centralized grip, fingertip grasp, cylindrical grasp, etc. The experimental results show that the classifier has a great potential application to the control of bionic man-machine systems because of its fast learning speed, high recognition capability and strong robustness.     

An efficient online trajectory generating method for underactuated crane systems

In this paper, a trajectory planning approach is proposed for underactuated overhead cranes. Different from existing trajectory planning methods, the presented approach generates trajectory commands online without the necessity of iterative optimization, which is convenient for practical implementation. We demonstrate the performance of the proposed method, including swing elimination and precise trolley positioning, with rigorous Lyapunov‐based mathematical analysis. Both numerical simulation and experimental results suggest that the presented method is feasible and efficient for practical applications. Copyright © 2013 John Wiley & Sons, Ltd.     

欠驱动无人水下航行器三维轨迹跟踪的反步控制

针对欠驱动无人水下航行器(underactuated unmanned underwater vehicles,UUVs)三维轨迹跟踪控制问题,本文有别于传统反步法中基于视线法设计姿态角误差变量的思路,提出了一种定义虚拟速度误差变量的反步控制器设计方法,能够有效避免传统反步法控制律设计时存在的奇异值问题,简化了传统反步法复杂的计算过程;设计了欠驱动UUV的三维轨迹跟踪控制器,给出了系统的误差方程,基于Lyapunov稳定性理论证明了系统在定常外界扰动下的鲁棒性和稳定性;仿真结果表明本文提出的UUV三维轨迹跟踪反步控制方法收敛、有效,能够实现欠驱动UUV对时变三维轨迹的精确跟踪控制.     

基于级联标准型的Acrobot反步控制

Acrobot是一种典型的二自由度欠驱动机械系统,针对Acrobot系统镇定控制中需要分别设计起摆控制器和平衡控制器,控制器设计复杂这一问题,提出一种新型的镇定控制策略,该控制策略仅仅需要设计一个控制器,就可以使Acrobot由竖直向下的稳定平衡点起摆,并稳定于竖直向上的不稳定平衡点。首先,采用欧拉-拉格朗日方程为系统建立动力学模型;然后,结合部分反馈线性化,提出一种闭环全局坐标变换方案,将Acrobot系统动力学模型转换为严格反馈级联标准型;最后,采用反步法将系统分为若干个子系统,分别为每个子系统构造Lyapunov函数,并设计虚拟控制输入,最终实现系统的镇定控制。仿真结果表明,所提出的控制策略简单有效,可以应用于与Acrobot系统类似的二自由度欠驱动系统中,具有较高的理论和应用价值。     

基于中心流形理论的欠驱动航天器姿态控制

考虑一类欠驱动航天器的执行机构为喷气推力器,根据航天器姿态动力学理论,建立欠驱动航天器姿态动力学方程。对于仅有两个反作用飞轮的零动量姿态控制系统设计了不连续的状态反馈控制器。基于给出的欠驱动航天器姿态动力学方程,设计控制律,利用中心流形方法判别驱动航天器系统在临界情形下的稳定性,得出欠驱动航天器姿态达到稳定状态的稳定性控制参数条件。数值仿真验证了所设计控制律的有效性。