Underactuated fingers controlled by robust and adaptive trajectory following methods

Choosing an appropriate control scheme to alleviate nonlinearities and uncertainties is not a trivial task, especially when models are not easily available and practical evaluation provides the only means for actual performance assessment. Various factors can contribute to these nonlinearities and uncertainties, such as friction and stiction. Thus, this article investigates four different control schemes, namely PID, adaptive, conventional sliding mode control (SMC) and integral sliding mode control (ISMC) which are implemented in the Bristol Elumotion Robot Hand (BERUL) to analyse and overcome the aforementioned problems. The hand has five fingers with 16 joints and all fingers are underactuated. The implementation of the proposed control schemes are challenging since the BERUL fingers have significant friction, stiction and unknown parameters. The fingers are light in weight and fragile. Comparative performance characteristics have shown that the ISMC is the most suitable candidate to provide good experimental trajectory following and positioning control for underactuated BERUL fingers.     

An economical synthesis of the major sex attractant of the oak leaf roller—cis-10-tetradecenyl acetate

The major sex attractant of the oak leaf roller (Archips semiferanus Walker),cis-10-tetradecenyl acetate (I), was synthesized in 55–62% overall yield by a highly economical route from inexpensive azelaic acid (II).Authorized as Paper No. 4779 in the Journal Series of the Pennsylvania Agricultural Experiment Station.     

Fuzzy PID control of space manipulator for both ground alignment and space applications

Considering gravity change from ground alignment to space applications, a fuzzy proportional-integral-differential (PID) control strategy is proposed to make the space manipulator track the desired trajectories in different gravity environments. The fuzzy PID controller is developed by combining the fuzzy approach with the PID control method, and the parameters of the PID controller can be adjusted on line based on the ability of the fuzzy controller. Simulations using the dynamic model of the space manipulator have shown the effectiveness of the algorithm in the trajectory tracking problem. Compared with the results of conventional PID control, the control performance of the fuzzy PID is more effective for manipulator trajectory control.     

Stabilization And Tracking Of Underactuated Surface Vessels In Random Waves With Fin Based On Adaptive Hierarchical Sliding Mode Technique

Trajectory tracking and roll stabilization are both vital practices in ship motion control. Trajectory tracking is a kind of low‐frequency control, while roll stabilization by means of fins is a kind of high‐frequency control. However, they have been studied separately previously; most tracking control of underactuated surface vessels in the previous studies do not account for roll stabilization by means of fins. In reality, however, they are an integral system. In this paper, a simple control strategy is proposed to achieve trajectory tracking and fin roll stabilization simultaneously. Four degrees of freedom derived from a six degrees of freedom mathematical model of a surface vessel is considered, including surge, sway, roll and yaw. Surge force, roll moment and yaw moment are considered as control inputs, while position, yaw angle and roll angle are controlled. The number of control inputs is fewer than the outputs to be controlled. Therefore, we are dealing with an underactuated problem. An adaptive hierarchical sliding mode control technique is employed to deal with the underactuation. Stabilization of underactuated surface vessels is studied as a special case. Random waves are applied to test the robustness of the designed controllers. Lyapunov stability theory is used to show the stability of closed‐loop system. The simulation results verify the effectiveness of the proposed strategy.     

基于QPSO 算法移动机器人轨迹规划与实验

针对移动机器人路径规划问题,提出一种基于QPSO算法的路径规划方法,并用概率论的方法分析了移动机器人路径规划的收敛性,阐明了该方法随均匀分布和正态分布的参数关系和收敛区间;然后根据移动机器人的运动特征提出一种改进的轨迹规划方法。移动机器人平台的实验结果表明了该方法在移动机器人路径规划中的有效性和可行性。     

轨迹空间中基于特征符号搜索算法的非刚体三维运动重建研究

现有研究一般是在正交约束条件下采用最小二乘法来求解三维运动轨迹基重建问题,然而这些算法的性能容易受噪声影响,产生不适定性。为此,通过利用离散线性的方法为三维运动搜索最优轨迹基系数和三维结构,建立了一种基于特征符号搜索算法的三维运动轨迹基重建方法。利用该方法,对一系列单目图像序列进行了重建实验研究,结果表明所提出的方法是可行的,并提高了重建算法的准确性。     

混炼硅橡胶的配合技术(四)

介绍了几种胶辊用混炼硅橡胶的配制,包括低硬度胶辊用混炼硅橡胶、低环硅氧烷含量的胶辊用混炼硅橡胶、送纸胶辊用混炼硅橡胶及工业胶辊用混炼硅橡胶的配制。     

基于近似弧长参数化的机器人轨迹规划

主要研究了采用近似弧长参数化的插值方法进行关节式工业机器人的轨迹规划.运用近似弧长参数化的插值方法将机器人末端轨迹参数曲线离散为等弧长的插值点序列,通过机器人逆向运动学求解各关节的位移点序列,采用极限的方法进行各关节速度和加速度规划.这种轨迹规划方法可以避免关节空间的插值计算和雅克比矩阵的计算.在 matlab7.8平台上,对近似弧长参数化的插值方法、轨迹规划及可行性验证进行了实例仿真,仿真结果表明该轨迹规划方法是可行的.     

防空导弹拦截目标的建模与仿真

利用simulink构造防空导弹抗击目标的模型.在比例导引的基础上,建立导弹和目标的运动轨迹方程,模拟两者运动轨迹对抗击过程进行仿真.模型结构简单,能够实现对航向角和航迹角的实时跟踪,同时可以利用简单的参数调整模拟不同类型目标.最后,对拦截过程多个相关因素的影响给予对比,仿真结果理想可靠.     

智能轮椅上的机械手运动学分析及轨迹规划*

装备了机械手臂的智能轮椅在助老、助残、辅助康复等方面都有重要的研究价值。对装备于智能轮椅的四自由度机械手臂运动学分析以及轨迹规划进行了研究,为机械手臂自主抓取建立了数学模型和理论依据,运用D-H法建立了机器人的运动学方程。提出了基于目标函数的最小功率法,在逆解存在多组解的情况下,选取节约能量的一组解,从而节约了能量。通过仿真实验验证了算法的有效性,为以后的轨迹优化、无碰撞轨迹规划建立基础。