A Real-time Look-ahead Trajectory Planning Methodology for Multi Small Line Segments Path

When a robot is required to machine a complex curved workpiece with high precision and speed,the tool path is typically dispersed into a series of points and transmitted to the robot.The conventional trajectory planning method requires frequent starts and stops at each dispersed point to complete the task.This method not only reduces precision but also causes damage to the motors and robot.A real-time look-ahead algorithm is proposed in this paper to improve precision and minimize damage.The proposed algorithm includes a path-smoothing algorithm,a trajectory planning method,and a bidirectional scanning module.The path-smoothing method inserts a quintic Bezier curve between small adjacent line segments to achieve G^(2)continuity at the junctions.The trajectory planning method utilizes a quartic polynomial and a double-quartic polynomial that can achieve a constant velocity at the velocity limitation.The bidirectional scanning module calculates the velocity at each trajectory planning segment point,simplifying calculation complexity and can be run in real time.The feasibility of the proposed algorithm is verified through simulations and experiments,which can be run in real time.In addition,high machining precision can be achieved by adjusting the relevant parameters.

基于多Agent强化学习的多站点CSPS系统的协作Look-ahead控制

研究多站点传送带给料生产加工站(Conveyor-serviced production station,CSPS)系统的最优控制问题,其优化目标是通过合理选择每个CSPS的Look-ahead控制策略,实现整个系统的工件处理率最大.本文首先根据多Agent系统的反应扩散思想,对每个Agent的原始性能函数进行改进,引入了具有扩散功能的局域信息交互项(原始项看作具有反应功能);并运用性能势理论,构建一种适用于平均和折扣两种性能准则的Wolf-PHC多Agent学习算法,以求解决策时刻不同步的多站点的协作Look-ahead控制策略.最后,论文通过仿真实验验证了该算法的有效性,学习结果表明,通过性能函数的改进,各工作站的负载平衡性得到改善,整个系统的工件处理率也明显提高.

结合look-ahead值排序的自适应分支求解算法

基于新近提出的自适应分支约束求解框架,结合look-ahead值启发式,提出一种新的约束求解算法AdaptBranchLVO。为验证算法效率,在标准测试库上进行了充分对比实验。结果表明,新提出算法在效率上明显优于已有的自适应分支求解算法。

A Generalized Acceleration and Deceleration Approach for Continuous Small Line Blocks with Look-ahead

Generally complex 3D contours are divided into a lot of continuous small line blocks by CAD/CAM software. When these small line blocks are used in conventional way,machine tool has to stop at the end of one move before continuing on to the next to meet accuracy requirement,which results in inefficiency.Look-ahead is an intelligent function that aims at adjusting the feed rate automatically to achieve maximum productivity while maintaining accuracy.By now most researchers just utilize the simplest linear acceleration(ACC)and deceleration(DEC)to deal with look-ahead intelligence.A generalized ACC/DEC ap- proach and corresponding optimal look-ahead algorithm based on dynamic back tracking along a doubly linked list are proposed.An improved rounding strategy for reducing interpolation errors is also presented.By using the proposed techniques,arbitrary velocity profiles that offer look-ahead feature and have the desired ACC/DEC characteristics for movement of a lot of continuous line blocks can be generated efficiently.Both simulations and experiments showed the productivity was dramatically increased without sacri- fice of accuracy.

LOOK-AHEAD ALGORITHM FOR VELOCITY CONTROL BASED ON PARAMETERIZED CURVE INTERPOLATOR

To avoid suffering gouge and transient overshooting in high speed cutting machining, a novel parametefized curve interpolator model with velocity look-ahead algorithm is proposed. Based on a prearrangement step interpolation algorithm for parameterized curves and considering high curvature points, parameterized curve tool path is divided into acceleration segments and deceleration segments by look-ahead algorithm. Under condition of characteristics of acceleration and deceleration stored in control system, deceleration before high curvature points and acceleration after high curvature points are realized in real-time in high speed cutting machining. Based on new parameterized curve interpolator model with velocity look-ahead algorithm, a real cubic spline is machined simulativly. The simulation results show that velocity look-ahead algorithm improves velocity changing more smoothly.

Study on Real-time Look-ahead and Adaptive Parametric Curve Interpolator

The principle of real-time look-ahead was introduced and analysed. An adaptive parametric curve interpolator with a real-time look-ahead function was developed for non-uniform rational B-spline (NURBS) curves interpolation, which considering the maximum acceleration/deceleration of the machine tool. In order to deal with the acceleration/deceleration around the feedrate sensitive corners, the look-ahead function was designed and illustrated. It can detect and adjust the feedrate adaptively. With the help of real-time look-ahead, the acceleration/deceleration can be limited to the range of the machine tool capacity. Thus, feedrate fluctuation is reduced. A NURBS curve interpolation experiment was provided to verify the feasibility and advantages of the proposed interpolator with a real-time look-ahead function.

A new deep-reading look-ahead method in electromagnetic loggingwhile-drilling using the scattered electric field from magnetic dipole antennas

This paper presents a new deep-reading logging-while-drilling electromagnetic(EM)logging method to detect bed boundaries ahead of bit.Unlike all existing EM logging approaches,the new method is based on the scattered electric field radiated by a magnetic dipole antenna.By analyzing the characteristics of electric tensor responses in layered formations,optimal look-ahead electric component is selected.The selected scattered field contributes to a large portion of the total field and is strongly sensitive to the boundary position.The measured voltage from the scattered electric component can be tens of times larger than that from the scattered magnetic fields and it attenuates slower.Thus,the detection capability improves significantly.A coaxial open-loop half-circle antenna is then proposed to measure the electric field in logging while drilling environment.A practical tool implementation equipped with two tilted close-loop antennas and two open-loop antennas is further developed for look-ahead application.Numerical results demonstrate that the detection depth of the new look-ahead tool can be up to 40 m under favorable conditions.Compared with current look-ahead logging tools,the new method not only significantly shortens the tool size,but also can recognize the boundary position and azimuth.

A new cellular automata model of traffic flow with negative exponential weighted look-ahead potential

With the development of traffic systems, some issues such as traffic jams become more and more serious. Efficient traffic flow theory is needed to guide the overall controlling, organizing and management of traffic systems. On the basis of the cellular automata model and the traffic flow model with look-ahead potential, a new cellular automata traffic flow model with negative exponential weighted look-ahead potential is presented in this paper. By introducing the negative exponential weighting coefficient into the look-ahead potential and endowing the potential of vehicles closer to the driver with a greater coefficient, the modeling process is more suitable for the driver’s random decision-making process which is based on the traffic environment that the driver is facing. The fundamental diagrams for different weighting parameters are obtained by using numerical simulations which show that the negative exponential weighting coefficient has an obvious effect on high density traffic flux. The complex high density non-linear traffic behavior is also reproduced by numerical simulations.

CNC中基于Bezier拟合的Look-Ahead轨迹规划的研究

轨迹规划是CNC系统的重要功能之一。传统CNC在处理连续微小NC程序时,存在诸如机床震颤、工件毛刺、加工效率低等问题。作者提出的Look-Ahead轨迹规划算法能解决上述问题,此算法将NC程序分成3种"大路径段",将连续微小路径(CSBs)拟合成Bezier曲线,再进行速度规划和轨迹插补,在此基础上提出Look-Ahead离线插补器的结构。仿真结果表明,该算法能够实现大量微小路径的连续加工。

基于动态前瞻深度的量子线路映射研究

随着量子计算技术的快速发展,现在已经进入了噪声中型量子(NISQ)时代。但受限于当前的技术,目前一个量子位只能与相邻的量子位直接交互。为了使量子线路能直接在NISQ设备上执行,需要在逻辑线路中插入SWAP门或使用桥门来近邻化量子位。为了减少量子线路映射中插入额外量子门的数量,本文研究了基于动态前瞻的线路映射方法,考虑了在拓展层中插入交换门的影响,优化了代价函数模型。通过模拟退火算法来确定插入交换门时的最佳前瞻深度,以减少插入交换门的数量,进而减少CNOT门的数量。实验结果表明,与现有映射方法相比,本文提出的算法减少了插入的CNOT门数,平均优化率达到45.59%。

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,which utilizes the maximal acceleration capabilities of the NC machine while satisfying the machining precision.A new and more efficient look-ahead method and a feedrate override method are also proposed to boast the global machining speed.The proposed algorithm has been implemented on Blue Sky NC System,and experimented in real material manufacturing.Compared with several existing algorithms,the current algorithm can improve the manufacturing time ranging from 50% to 180%,depending on the machining parameters,and also results in better machining quality.In addition,the algorithm also satisfies the need of real-time interpolation.

计及调节资源AGC动态特性的离散-连续时间随机前瞻经济调度

随着具有波动性的可再生能源渗透比例不断提高,系统对调频备用的需求显著增加。为了制定更合理的调度方案和调频备用,有必要研究经济调度和自动发电控制(automatic generation control,AGC)之间的协调优化。该文提出建立考虑调节资源AGC动态特性的离散-连续时间随机前瞻经济调度模型,以制定兼顾能量平衡和调频需求的调度决策,并实现快慢资源的最优协同,增强系统的动态调节能力。为降低模型复杂度,在当前时段将调节资源的AGC动态特性建模为精细化离散模型,在前瞻时段采用简化的连续时间模型刻画调节资源的AGC动态特性,显著降低问题规模。通过在目标函数中引入合适的储能充放电成本惩罚项,将储能充放电互补约束松弛,从而消除01变量。最后,采用Benders分解算法实现并行求解,进一步降低了计算时间。该文在PJM5节点系统和IEEE118节点系统进行算例验证。结果表明,与传统模型相比,所提模型可以有效降低系统的频率偏差;与在前瞻时段考虑精细化AGC动态约束的模型相比,所提模型可显著降低计算时间。

Enhanced Flexible Ramping Product Formulation for Alleviating Capacity Shortage in Look-ahead Commitment

The roll-out of a flexible ramping product provides independent system operators(ISOs)with the ability to address the issues of ramping capacity shortage.ISOs procure flexible ramping capability by committing more generating units or reserving a certain amount of headrooms of committed units.In this paper,we raise the concern of the possibility that the procured flexible ramping capability cannot be deployed in realtime operations due to the unit shut-down in a look-ahead commitment(LAC)procedure.As a solution to the issues of ramping capacity shortage,we provide a modified ramping product formulation designed to improve the reliability and reduce the expected operating cost.The trajectories of start-up and shutdown processes are also considered in determining the ramping capability.A new optimization problem is formulated using mixed integer linear programming(MILP)to be readily applied to the practical power system operation.The performance of this proposed method is verified through simulations using a small-scale system and IEEE 118-bus system.The simulation results demonstrate that the proposed method can improve the generation scheduling by alleviating the ramping capacity shortages.

面向电网前瞻调度嵌入领域知识的深度强化学习方法

强化学习由于具有自学习与自寻优能力,在电网前瞻调度等领域渐露头角。然而,现有基于强化学习的调度方法对最优策略的探索效率及收敛性较低。为了适应大规模电网,考虑历史发电数据、电力平衡、新能源消纳率、线路负载率等领域知识,将其嵌入至强化学习策略网络正则项并用于引导智能体训练方向。该方法在训练前期基于专家修正后的历史机组出力轨迹学习调度员经验,使得智能体策略网络参数快速收敛到一个有效初始解;在训练中后期,引入电力平衡等损失函数正则项,引导智能体满足先验调度知识,有效预防智能体盲动行为,提升调度决策质量。最后,利用IEEE118节点系统验证所提算法有效性。

高比例可再生能源接入下含自愈性能的分布式配电网重构策略研究

【目的】随着可再生能源电网占比逐年增加,电网的波动性和不确定性显著提升,给配电网的安全运行带来挑战。针对高比例新能源电网分布式配网重构问题,提出一种在线滚动优化框架方法。【方法】通过分布式共识协议获取网络拓扑和节点运行信息,在N-1和N-2线路故障状态下自动重构,实现配电网无额外外部触发信号情况下自动恢复正常运行,保证电网经济运行。同时采用滚动优化方法处理高比例可再生能源所导致的电网波动问题,并利用生成对抗网络(generative adversarial network,GAN)技术生成新数据,结合历史数据实现电网运行数据高精度预测。【结果】所提方法在正常状态、单点故障和两点故障3种情况下,均能实现电网的自动经济运行优化和自愈修复。【结论】与鲁棒规划和随机规划等方法相比,所提出方法可提升电网预测精度。

弱分界面下物流AGV障碍物识别系统设计

针对当前AGV无法对障碍物做出前瞻性预判的问题,设计一种优化智能物流AGV障碍物激光扫描识别系统。将采集的数据生成图片并进行去噪处理,利用背景减除等方法检测障碍物,并传输信号到AGV系统中;基于多步前瞻算法及TOF测距方法,完成障碍物的弱分界面区分迭代识别及测距。实验结果表明:设计的系统应用到AGV中,障碍物平均正检率高于90%,且障碍物面积检测计算的误差率最大仅为3.94%,设计的系统具有一定的实用价值。

Effect of Look-Ahead Depth in Evolutionary Checkers

It is intuitive that allowing a deeper search into a game tree will result in a superior player to one that is restricted in the depth of the search that it is allowed to make. Of course, searching deeper into the tree comes at increased computational cost and this is one of the trade-offs that has to be considered in developing a tree-based search algorithm. There has been some discussion as to whether the evaluation function, or the depth of the search, is the main contributory factor in the performance of an evolved checkers player. Some previous research has investigated this question （on Chess and Othello）, with differing conclusions. This suggests that different games have different emphases, with respect to these two factors. This paper provides the evidence for evolutionary checkers, and shows that the look-ahead depth （like Chess, perhaps unsurprisingly） is important. This is the first time that such an intensive study has been carried out for evolutionary checkers and given the evidence provided for Chess and Othello this is an important study that provides the evidence for another game. We arrived at our conclusion by evolving various checkers players at different ply depths and by playing them against one another, again at different ply depths. This was combined with the two-move ballot （enabling more games against the evolved players to take place） which provides strong evidence that depth of the look-ahead is important for evolved checkers players.

自动泊车路径纯跟踪算法应用研究

为实现自动泊车系统的路径跟踪功能,解决纯跟踪算法由于预瞄距离选取不当导致的方向盘抖动、跟踪精度下降的问题,文中提出了一种改进的纯跟踪路径跟踪算法,该方法在传统纯跟踪算法的计算结果基础上设计了一种带记忆参数的方向盘转角修正算法.实车实验表明,该方法适用于自动泊车系统,可以在适用工况下选取较小的预瞄距离,在保证跟踪精度的同时解决了纯跟踪算法在小预瞄距离下的方向盘抖动问题.

基于时滞补偿的纯追踪控制预瞄距离优化方法

纯追踪算法是无人驾驶领域中常用的路径跟踪算法,其中预瞄距离的选择影响着路径自主跟踪的精度。针对实际车辆时滞导致理论最优预瞄距离与实际最优预瞄距离不符的问题,提出了一种基于时滞补偿的纯追踪控制预瞄距离优化方法。首先,基于时延和迟滞对传统模型的影响,更新时滞车辆模型;其次,设计了一种改进樽海鞘优化算法对预瞄距离进行优化,研究不同车辆速度下最优预瞄距离配置,得到了仿真平台下最优预瞄距离和速度的一次线性关系式;最后,在实际车辆平台上,对所提优化方法进行了实验验证。实验结果表明:相比于传统模型,加入时滞补偿所得最优预瞄准确率提高了67.55%。

一种快速有限时间收敛的轨迹跟踪引导律

针对参考轨迹曲率变化大导致前视距离(LAD)调整不及时,使得无人船(USV)轨迹跟踪误差收敛慢的问题,本文利用轨迹跟踪几何关系,建立位置跟踪误差动态系统,引入曲率参数设计一种新型的时变前视距离(NTLAD),提出一种快速有限时间收敛的轨迹跟踪引导律(FFTC-GL),包括期望艏向引导律和期望巡航速度引导律研究,以快速准确跟踪大范围曲率的轨迹.首先,构造NTLAD的稳定约束条件,结合图解法求解NTLAD函数,实现法向误差快速有限时间收敛,并且引入曲率参数,快速准确地跟踪不同曲率的轨迹.其次,基于切向误差的有限时间技术,设计快速有限时间速度引导律,实现切向误差动态系统的有限时间稳定.最后,通过对比有限时间上确界,表明引导律对位置跟踪误差收敛的快速性.轨迹跟踪仿真表明FFTC-GL能够在有限时间内跟踪参考轨迹,保证曲线拐点位置跟踪误差快速收敛.