Simultaneous algorithm for trajectory planning

This paper addresses the solution of smooth trajectory planning for industrial robots in environments with obstacles using a direct method, creating the trajectory gradually as the robot moves. The presented method deals with the uncertainties associated with the lack of knowledge of kinematic properties of intermediate via‐points since they are generated as the algorithm evolves looking for the solution. Several cost functions are also proposed, which use the time that has been calculated to guide the robot motion. The method has been applied successfully to a PUMA 560 robot and four operational parameters (execution time, computational time, distance travelled and number of configurations) have been computed to study the properties and influence of each cost function on the trajectory obtained. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

A CNC interpolation algorithm for boundary machining

This paper presents an efficient and accurate algorithm for machining boundaries formed at the intersection of two surfaces, an important manufacturing problem in CNC machining. The algorithm is developed using a locus tracing technique implemented on the basis of Danielson's step selection rules. A vertical ball-end milling cutter moves along the considered boundary, in contact with the two surfaces. The algorithm guides the center of the spherical end of the cutter, to maintain exact contact (within 1 step) along the entire path. A seamless formulation is used, allowing the contact points to move freely from the ball-end to the cutter periphery and vice-versa. The surfaces forming the boundary may be implicitly or parametrically defined. The reliability of the algorithm is demonstrated for both cases, by treating a complex boundary machining example. The boundary considered is formed by the intersecting quadratic surfaces of a sphere and an elliptic hyperboloid.     

High speed interpolation for micro-line trajectory and adaptive real-time look-ahead scheme in CNC machining

CNC machining plays an important role in mechanical manufacturing.A key issue is to improve the machining feedrate while keeping the machining precision and satisfying the acceleration constraints of the CNC machine.For the consecutive micro-line segments interpolation,the velocities at the junction of two segments are the bottlenecks for the machining efficiency.This paper proposes a multi-period turning method to improve the feedrate at the junctions using the linear acceleration and deceleration mode,whi...     

基于信赖域算法的机械臂时间最优轨迹规划

为了提高机械臂的工作效率,提出了一种新的时间最优轨迹规划方法.通过逆运动学运算得到与任务空间轨迹对应的关节空间位置序列,采用7次B样条曲线构造关节空间插值轨迹,将运动学约束转换为对B样条轨迹曲线控制顶点的约束,并适当放大约束条件,然后采用信赖域方法求解时间优化问题,从而规划出速度、加速度和脉动均连续且满足运动学约束的时间最优轨迹.仿真结果验证了所提出时间最优轨迹规划方法的有效性.     

一种新的实时智能汽车轨迹规划方法

针对智能汽车的驾驶决策和轨迹规划问题, 将轨迹表示为轨迹曲线和加速度变化两部分, 以优化轨迹的行驶效率、安全性、舒适性和经济性为目标建立非线性规划模型. 基于序优化思想, 提出混合智能优化算法OODE, 分内、外两层分别优化加速度变化和轨迹曲线, 通过“粗糙” 评价轨迹曲线实现轨迹曲线的快速择优. 仿真结果表明, 所提出的方法能够处理包含多动态障碍物的复杂交通场景, 且具备实时应用能力, 模型的精度和求解速度均优于传统方法.

     

基于AGA的时间最优机械臂轨迹规划算法*

根据机械臂运动学约束,提出了关节空间基于自适应遗传算法(AGA)的3-5-3多项式插值轨迹规划算法。利用运动学约束,以最优时间为目标,针对关节型机器人在静态环境下点到点的轨迹规划问题,利用AGA算法解算多项式插值的时间。通过与基于GA的3-5-3多项式机械臂轨迹规划进化曲线和运动位置、速度、加速度曲线对比,证明该方法在算法收敛、运行平稳度上都有突出优点。     

基于量子行为烟花算法的移动机器人路径规划及平滑

针对移动机器人全局路径规划问题,提出一种基于量子行为烟花算法(quantum-behaved fireworks algorithm,QFWA)的路径规划方法.改进算法在基本烟花算法(fireworks algorithm, FWA)的基础上增加了基于量子行为的烟花爆炸策略.该策略使得种群在接近全局最优时具有较强的局部搜索能力,同时在种群远离全局最优位置时具有较强的全局搜索能力.改进算法提高了烟花爆炸产生火花的多样性和算法的收敛速度.在Benchmark测试函数上将改进算法与其他几种优化算法进行了对比,结果表明改进算法的性能优于其他算法.将QFWA应用于求解移动机器人路径规划问题,并采用均值滤波结合人工势场法对规划出的路径进行路径平滑处理.仿真实验结果表明改进方法在移动机器人路径规划问题上的可行性和有效性.     

Model-based trajectory reconstruction with IMM smoothing and segmentation

This paper presents a new approach for off-line trajectory reconstruction in air traffic control domain. The proposed algorithm, called model-based reconstruction, performs an accurate IMM smoothing process whose parameters are modified along time according to the flight modes segmented from trajectory measurements. Its competitive performance is demonstrated through comparison with previous reconstruction methods used in ATC and with classical IMM smoothing, using simulated data.     

解决TSP问题的局部调整离散微粒群算法

微粒群算法提出以来一直不能较好的解决离散及组合优化问题,针对这个问题,通过对微粒群算法的优化机理的分析,对原有的微粒群进化方程中的速度和位置的更新等进行重新的定义,同时提出一种具有自适应能力的惯性因子,使其适合解决TSP这样的组合优化问题.针对过去的离散算法整体调整容易形成对路径的破坏这一缺点,在重新定义的算法上加入局部调整的策略,形成一种局部调整的离散微粒群算法(local adjustive discrete PSO,LADPSO),通过在ch31和ei151上的试验,证明了该算法在解决这一问题上是可行的.     

An analytical C3 continuous tool path corner smoothing algorithm for 6R robot manipulator

Tool path smoothness is important to guarantee good dynamic and tracking performance of robot manipulators. An analytical C³ continuous tool path corner smoothing algorithm is proposed for robot manipulators with 6 rotational (6R) joints. The tool tip position is smoothed directly in the workpiece coordinate system (WCS). The tool orientation is smoothed after transferring the tool orientation matrix as three rotary angles. Micro-splines of the tool tip position and tool orientation are constructed under the constraints of the maximum deviation error tolerances in the WCS. Then the tool orientation and tool tip position are synchronized to the tool tip displacement with C³ continuity by replacing the remaining linear segments using specially constructed B-splines. Control points of the locally inserted micro-splines are all evaluated analytically without any iterative calculations. Simulation and experimental results show that the proposed algorithm satisfies constraints of the preset tool tip position and the tool orientation tolerances. The proposed corner smoothing algorithm achieves smoother and lower jerks than C² continuous corner smoothing algorithm. Experimental results show that the tracking errors associated to the execution of the C³ continuous tool path are up to 10% smaller than C² continuous path errors.     

基于改进RRT-connect的四旋翼无人机避障轨迹规划算法

针对四旋翼无人机在低空复杂环境自主巡航所需的航迹规划问题,提出了一种基于快速搜索随机树(RRT-connect)的改进型算法。根据四旋翼无人机的微分平坦特性,合理设计了规划空间;引入转角约束和路径修剪方法,在保证规划实时性的基础上使所规划路径的平均长度缩短了19%;通过B样条函数对路径进行平滑处理,使生成的轨迹具有二阶几何连续性,同时能避免与障碍物区域发生碰撞。经多次重复对比试验,证实了提出算法的有效性、优越性和稳定性。     

基于混合遗传算法的工业机器人最优轨迹规划

为兼顾工业机器人工作效率与轨迹的平稳性,提出一种基于混合遗传算法的二次轨迹规划方案.通过最优时间轨迹规划得到最小执行时间,在最小执行时间内进行最优冲击轨迹规划,进而规划出一条既高效又平滑的运动轨迹.采用五次均匀B样条在关节空间进行快速插值,不仅保证了各关节速度和加速度连续性还保证了各关节冲击的连续性.连续平滑的冲击可以减少机械振动,延长机器人的工作寿命.选用PUMA560为对象进行仿真与实验,结果表明,该方案可以获得比较理想的机器人运动轨迹,所提出的混合遗传算法能有效提高全局寻优的性能和算法运行的稳定性.     

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。     

安全平滑的改进时间弹性带轨迹规划算法

传统TEB(time elastic band)算法在杂乱场景下规划易出现倒退、大转向等异常行为,造成加速度跳变,控制指令不平滑,机器人受到大冲击,不利于移动机器人轨迹跟踪.鉴于此,提出一种改进TEB算法,通过增加危险惩罚因子约束规划更安全的运动轨迹,增加加速度跳变以抑制约束减小运动中的最大冲击,增加末端平滑约束以减小末端冲击,实现目标点平滑、准确到达.构建图优化问题,以机器人的位姿和时间间隔为节点、目标函数和约束函数为边,利用问题的稀疏性快速获得相应时刻点的控制量.最后,通过基于机器人操作系统的大量对比仿真测试以及真实差速机器人上的物理实验对提出的改进TEB算法进行性能验证.结果表明,改进TEB算法在复杂环境中能够规划出更安全、平滑的轨迹,减小机器人所受冲击,实现移动机器人更合理地运动.     

Feed-rate and trajectory optimization for CNC machine tools

The key task performed by CNCs is the generation of the time-sequence of set-points for driving each physical axis of the machine tool during program execution. This interpolation of axes movement must satisfy a number of constraints on axes dynamics (velocity, acceleration, and jerk), and on process outcome (smooth tool movement and precise tracking of the nominal tool-path at the desired feed-rate). This paper presents an algorithm for CNC kernels that aims at solving the axes interpolation problem by exploiting an Optimal Control Problem formulation. With respect to other solutions proposed in the literature, the approach presented here takes an original approach by assuming a predefined path tracking tolerance—to be added to the constraints listed above—and calculating the whole trajectory (path and feed-rate profile) that satisfies the given constraints. The effectiveness of the proposed solution is benchmarked against the trajectory generated by an industrial, state-of-the-art CNC, proving a significant advantage in efficiency and smoothness of axes velocity profiles.     

Application of a dynamic programming algorithm for trajectory planning of finger-like manipulators

Dextrous hand designs require planning and coordination of multijointed fingers. This communication presents a dynamic programming algorithm to optimize the trajectory of a finger or a fingerlike manipulator. The algorithm generates a minimum cost trajectory for a specified cost function (such as accuracy or time of travel) and a set of constraints (such as obstacles along the trajectory). We present simulations demonstrating the trajectory planning for simplified fingerlike manipulator configurations. This approach is potentially applicable to several additional situations faced by multijointed fingers employed in dextrous hand designs, such as complex trajectory planning, obstacle avoidance, and fault tolerance. We illustrate some results obtained by computer simulations of these problems.     

改进海洋捕食者算法和插值平滑的机器人路径规划

鉴于传统的智能优化算法（intelligent optimization algorithm,IOA）不能很好解决插值平滑的机器人路径规划（robot path planning,RPP）问题,以及最近提出的海洋捕食者算法（marine predators algorithm,MPA）的优势和不足,提出了一种改进的MPA,即提升信息交流的MPA（interchange enhanced MPA,IEMPA）,用于解决RPP。首先提出一种融合趋向全局最优的反向学习策略用于随机选择的一个捕食者的位置更新,以便降低陷于局部最优的概率;然后提出了一种三阶段最优引导最差策略来强化最差个体以便提升整个群体和提高搜索能力;随后,提出一种信息共享策略用于捕食前期以进一步提高算法的搜索能力;最后将IEMPA用于插值平滑的RPP中。大量的多场景RPP问题的优化实验结果表明,与MPA等优秀算法相比,IEMPA搜索能力更强、精度更高、收敛速度更快,能更好地处理RPP,可应用到在其他复杂优化问题上。     

考虑轧辊成本的轧制计划编制与调整

在分析轧辊车削成本的基础上对轧制计划编制和调整问题进行深入研究, 建立以最小化轧辊车削量为目标的0-1整数规划模型. 针对问题特征, 构造基于替换邻域搜索的两阶段算法: 第1阶段, 对轧制单元实施最佳匹配和交叉使用调整; 第2阶段, 通过搜索轧制单元的轧辊替换邻域, 用车削量较少的轧辊替代车削量较大的轧辊, 从而优化第1阶段的有效解. 通过实际生产数据验证, 两阶段算法能够在满足轧制工艺规程的基础上有效降低轧辊车削量, 算法和模型均可行且有效.     

Feedrate planning for machining with industrial six-axis robots

Nowadays, the adaptation of industrial robots to carry out high-speed machining operations is strongly required by the manufacturing industry. This new technology machining process demands the improvement of the overall performances of robots to achieve an accuracy level close to that realized by machine-tools. This paper presents a method of trajectory planning adapted for continuous machining by robot. The methodology used is based on a parametric interpolation of the geometry in the operational space. FIR filters properties are exploited to generate the tool feedrate with limited jerk. This planning method is validated experimentally on an industrial robot.