Sampling-based planning algorithms play an important role in high degree-of-freedom motion planning(MP)problems,in which rapidly-exploring random tree(RRT)and the faster bidirectional RRT(named RRT-Connect)algorithms ...Sampling-based planning algorithms play an important role in high degree-of-freedom motion planning(MP)problems,in which rapidly-exploring random tree(RRT)and the faster bidirectional RRT(named RRT-Connect)algorithms have achieved good results in many planning tasks.However,sampling-based methods have the inherent defect of having difficultly in solving planning problems with narrow passages.Therefore,several algorithms have been proposed to overcome these drawbacks.As one of the improved algorithms,Rapidlyexploring random vines(RRV)can achieve better results,but it may perform worse in cluttered environments and has a certain environmental selectivity.In this paper,we present a new improved planning method based on RRT-Connect and RRV,named adaptive RRT-Connect(ARRT-Connect),which deals well with the narrow passage environments while retaining the ability of RRT algorithms to plan paths in other environments.The proposed planner is shown to be adaptable to a variety of environments and can accomplish path planning in a short time.展开更多
Due to the interrelationship between the base placement of the manipulator and its operation object,it is significant to analyze the accessibility and workspace of manipulators for the optimization of their base locat...Due to the interrelationship between the base placement of the manipulator and its operation object,it is significant to analyze the accessibility and workspace of manipulators for the optimization of their base location.A new method is presented to optimize the base placement of manipulators through motion planning optimization and location optimization in the feasible area for manipulators.Firstly,research problems and contents are outlined.And then the feasible area for the manipulator base installation is discussed.Next,index depended on the joint movements and used to evaluate the kinematic performance of manipulators is defined.Although the mentioned indices in last section are regarded as the cost function of the latter,rapidly-exploring random tree(RRT) and rapidly-exploring random tree*(RRT*) algorithms are analyzed.And then,the proposed optimization method of manipulator base placement is studied by means of simulation research based on kinematic performance criteria.Finally,the conclusions could be proved effective from the simulation results.展开更多
The quality of hot-rolled steel strip is directly affected by the strip crown.Traditional machine learning models have shown limitations in accurately predicting the strip crown,particularly when dealing with imbalanc...The quality of hot-rolled steel strip is directly affected by the strip crown.Traditional machine learning models have shown limitations in accurately predicting the strip crown,particularly when dealing with imbalanced data.This limitation results in poor production quality and efficiency,leading to increased production costs.Thus,a novel strip crown prediction model that uses the Boruta and extremely randomized trees(Boruta-ERT)algorithms to address this issue was proposed.To improve the accuracy of our model,we utilized the synthetic minority over-sampling technique to balance the imbalance data sets.The Boruta-ERT prediction model was then used to select features and predict the strip crown.With the 2160 mm hot rolling production lines of a steel plant serving as the research object,the experimental results showed that 97.01% of prediction data have an absolute error of less than 8 lm.This level of accuracy met the control requirements for strip crown and demonstrated significant benefits for the improvement in production quality of steel strip.展开更多
为提高果园自主移动机器人在山区、丘陵等复杂地形环境下运动路径规划效果,增强机器人野外工作性能,针对果园非结构化布局和起伏地形,本文提出了一种基于改进PF-RRT*(Plane fitting-rapidly exploring random trees star)算法的果园机...为提高果园自主移动机器人在山区、丘陵等复杂地形环境下运动路径规划效果,增强机器人野外工作性能,针对果园非结构化布局和起伏地形,本文提出了一种基于改进PF-RRT*(Plane fitting-rapidly exploring random trees star)算法的果园机器人路径规划方法。利用自适应采样步长策略,在果园不同障碍物密度环境下能够灵活地调节随机树扩展步长。采用自适应目标偏置的势场引导采样方法,能够有效引导随机树避开障碍物并向目标点扩展。此外,在随机树扩展过程引入地形评估函数。通过平面拟合技术对地形坡度、稀疏度和粗糙度进行综合评估,确保规划的路径在复杂地形中可通过性和安全性。最后,采用三次样条插值与高斯过程回归对路径进行平滑和优化。在仿真环境中,改进PF-RRT*算法与RRT*、Q-RRT*和PF-RRT*算法相比,轨迹偏差最多减少46.97%,路径长度最多减少7.64%,规划时间最多减少23.58%,且成功率和避障效果均优于对比算法。真实果园行间试验结果表明,与RRT*、Q-RRT*和PF-RRT*算法相比,改进PF-RRT*算法与理想轨迹偏差量减少34.04%、26.19%、27.91%、路径长度减少6.58%、3.16%和4.10%、规划时间减少30.56%、18.25%和33.52%。表明本文算法在果园复杂地形下能够实现自主移动机器人最优路径规划与导航。展开更多
To guide an unmanned aerial vehicle(UAV)flying in complex three-dimensional(3D)environments with unknown obstacles,a novel UAV path planning algorithm named IRRT∗-C2TD3 is proposed.The algorithm combines the rapidl...To guide an unmanned aerial vehicle(UAV)flying in complex three-dimensional(3D)environments with unknown obstacles,a novel UAV path planning algorithm named IRRT∗-C2TD3 is proposed.The algorithm combines the rapidly-exploring random tree star(RRT∗)algorithm with the twin delayed deep deterministic policy gradients(TD3)algorithm(a deep reinforcement learning algorithm).By employing exploration strategies from reinforcement learning,IRRT∗-C2TD3 improves the RRT∗algorithm.IRRT∗-C2TD3 is a two-stage path planning algorithm comprising pre-planning and real-time planning.It performs pre-planning of paths by generating paths based on geometric connections toward the goal and smoothing them using cubic B-spline curves.By designing the network architecture and reward function of the TD3 algorithm,real-time planning in unknown environments is achieved based on the pre-planned path from the first stage.Simulation results show that IRRT∗-C2TD3 demonstrates better path planning performance in 3D partially unknown environments than RRT∗-C2TD3,M-C2TD3 and MODRRT∗algorithms.展开更多
This paper investigates the six degree-of-freedom(6DOF)relative kinodynamic motion planning problem for spacecraft close approach operations,wherein a controlled chaser spacecraft is required to approach a noncooperat...This paper investigates the six degree-of-freedom(6DOF)relative kinodynamic motion planning problem for spacecraft close approach operations,wherein a controlled chaser spacecraft is required to approach a noncooperative space target at a close range under both dynamic constraints and motion constraints.An enhanced version of the bidirectional rapidlyexploring random tree*(BiRRT*)algorithm based on flight zoning(FZ-BiRRT*)is proposed to generate safe,feasible,and nearoptimal relative motion trajectories.In the proposed algorithm,the space surrounding the space target is zoned in a spherical coordinate system based on the collision probability so that specific designs can be made for different phases of the approaching.Subsequently,based on the flight zone,dynamic constraints,and experiential knowledge,a series of modifications are made to the classic BiRRT*algorithm,and a postprocessing step is designed to accelerate convergence and promote search efficiency.Furthermore,a general regression neural network is introduced to fit a smooth and applicable final motion trajectory.Finally,the feasibility of the generated motion trajectory and the superiority of the proposed algorithm is demonstrated by means of numerical simulations.展开更多
针对传统RRT(Rapidly-exploring Random Tree)算法在进行机械臂路径规划时存在的采样随机性过大、搜索效率低下、所规划的路径曲折等问题,提出一种基于采样区域限制的改进RRT(Sampling Area Restriction RRT,SAR-RRT)算法。首先,针对随...针对传统RRT(Rapidly-exploring Random Tree)算法在进行机械臂路径规划时存在的采样随机性过大、搜索效率低下、所规划的路径曲折等问题,提出一种基于采样区域限制的改进RRT(Sampling Area Restriction RRT,SAR-RRT)算法。首先,针对随机性过大的问题,通过引入目标偏置策略来增强随机树的目标导向性,并采用球形采样区域以及角度限制策略对算法的采样进行约束,减少算法对无用空间区域的探索。其次,为提升算法的搜索效率,对随机树的节点扩展进行自适应优化,采用多步长扩展,使算法能够充分利用环境与障碍物的信息,同时利用贪婪思想加快随机树的收敛从而缩短路径的生成时间。最后,对初始规划出的路径进行二次优化处理,在去除路径中的冗余点后以三次B样条曲线对路径进行平滑处理,提升所规划路径的质量。实验结果表明,在2维及3维场景下,SAR-RRT算法均可以顺利完成路径规划任务。对比传统RRT算法,改进算法总体上使路径长度降低27.73%,规划时间缩短85.25%,采样点数减少87.19%且所生成的路径更加平滑。展开更多
针对快速搜索随机树(rapidly-exploring random tree,RRT)算法的随机采样特征导致的收敛速度慢、路径冗余度高、采样点利用率低问题,给出一种新的解决方法。首先,根据图复杂度公式,计算出图的复杂度后确定目标偏执概率,建立偏置概率自...针对快速搜索随机树(rapidly-exploring random tree,RRT)算法的随机采样特征导致的收敛速度慢、路径冗余度高、采样点利用率低问题,给出一种新的解决方法。首先,根据图复杂度公式,计算出图的复杂度后确定目标偏执概率,建立偏置概率自适应模型;其次,在首次规划好路线后,路径中仍存在一些不必要的拐点与棱角,针对传统路径裁剪依赖局部搜索策略,可能导致次优解生成,提出PRM-Dijkstra(probabilistic roadmap-dijkstra)算法对路径进行裁剪,将改进RRT算法生成的树节点利用PRM算法相互连接起来,通过Dijkstra算法计算出一条最优路径;最后,改进RRT算法与PRM-Dijkstra种算法优势相结合,在保证有一条路径的前提下,最大概率的寻找最优路径。通过复杂图下仿真避障实验,结果显示:改进RRT算法在节点生成数量与规划用时相较传统RRT算法平均减少80%,相较于Goal-bias RRT算法均减少40%。并通过机器人操作系统(robot operating system,ROS)下的MoveIt!集成开发平台进行现实环境下避障实验,验证了算法的可行性与有效性。展开更多
This study focuses on the improvement of path planning efficiency for underwater gravity-aided navigation.Firstly,a Depth Sorting Fast Search(DSFS)algorithm was proposed to improve the planning speed of the Quick Rapi...This study focuses on the improvement of path planning efficiency for underwater gravity-aided navigation.Firstly,a Depth Sorting Fast Search(DSFS)algorithm was proposed to improve the planning speed of the Quick Rapidly-exploring Random Trees*(Q-RRT*)algorithm.A cost inequality relationship between an ancestor and its descendants was derived,and the ancestors were filtered accordingly.Secondly,the underwater gravity-aided navigation path planning system was designed based on the DSFS algorithm,taking into account the fitness,safety,and asymptotic optimality of the routes,according to the gravity suitability distribution of the navigation space.Finally,experimental comparisons of the computing performance of the ChooseParent procedure,the Rewire procedure,and the combination of the two procedures for Q-RRT*and DSFS were conducted under the same planning environment and parameter conditions,respectively.The results showed that the computational efficiency of the DSFS algorithm was improved by about 1.2 times compared with the Q-RRT*algorithm while ensuring correct computational results.展开更多
针对六自由度工业机器人在复杂的分拣环境中分拣速度慢、避障效果差等问题,提出了一种融合人工势场(Artificial Potential Field,APF)算法的快速扩展随机树(Rapidly-exploring Random Tree,RRT)改进算法。传统RRT算法路径规划随机性强...针对六自由度工业机器人在复杂的分拣环境中分拣速度慢、避障效果差等问题,提出了一种融合人工势场(Artificial Potential Field,APF)算法的快速扩展随机树(Rapidly-exploring Random Tree,RRT)改进算法。传统RRT算法路径规划随机性强、收敛速度慢,在该算法中引入APF机制引导其向目标点进行有效扩展,减少路径搜索过程中的无效分支,提高搜索效率;优化对父系节点的选择策略,对原路径局部节点进行优化重连,提高路径质量及平滑性。根据实际分拣中可能出现的状况,在MATLAB软件中建立了3个不同的仿真场景,并将所提出的改进APF-RRT算法与传统RRT算法、APF-RRT算法进行对比仿真实验。结果表明,改进APF-RRT算法于不同分拣环境中,在路径长度、搜索时间、节点个数和迭代次数4个指标上均有一定提升,能以更高的效率搜索到更高质量的路径。展开更多
基金supported in part by the National Science Foundation of China(61976175,91648208)the Key Project of Natural Science Basic Research Plan in Shaanxi Province of China(2019JZ-05)。
摘要Sampling-based planning algorithms play an important role in high degree-of-freedom motion planning(MP)problems,in which rapidly-exploring random tree(RRT)and the faster bidirectional RRT(named RRT-Connect)algorithms have achieved good results in many planning tasks.However,sampling-based methods have the inherent defect of having difficultly in solving planning problems with narrow passages.Therefore,several algorithms have been proposed to overcome these drawbacks.As one of the improved algorithms,Rapidlyexploring random vines(RRV)can achieve better results,but it may perform worse in cluttered environments and has a certain environmental selectivity.In this paper,we present a new improved planning method based on RRT-Connect and RRV,named adaptive RRT-Connect(ARRT-Connect),which deals well with the narrow passage environments while retaining the ability of RRT algorithms to plan paths in other environments.The proposed planner is shown to be adaptable to a variety of environments and can accomplish path planning in a short time.
基金Supported by the National Science and Technology Support Program of China(No.2013BAK03B01)
摘要Due to the interrelationship between the base placement of the manipulator and its operation object,it is significant to analyze the accessibility and workspace of manipulators for the optimization of their base location.A new method is presented to optimize the base placement of manipulators through motion planning optimization and location optimization in the feasible area for manipulators.Firstly,research problems and contents are outlined.And then the feasible area for the manipulator base installation is discussed.Next,index depended on the joint movements and used to evaluate the kinematic performance of manipulators is defined.Although the mentioned indices in last section are regarded as the cost function of the latter,rapidly-exploring random tree(RRT) and rapidly-exploring random tree*(RRT*) algorithms are analyzed.And then,the proposed optimization method of manipulator base placement is studied by means of simulation research based on kinematic performance criteria.Finally,the conclusions could be proved effective from the simulation results.
基金supported by the National Natural Science Foundation of China(Grant Nos.52074085,U21A20117 and U21A20475)the Fundamental Research Funds for the Central Universities(Grant No.N2004010)the Liaoning Revitalization Talents Program(XLYC1907065).
摘要The quality of hot-rolled steel strip is directly affected by the strip crown.Traditional machine learning models have shown limitations in accurately predicting the strip crown,particularly when dealing with imbalanced data.This limitation results in poor production quality and efficiency,leading to increased production costs.Thus,a novel strip crown prediction model that uses the Boruta and extremely randomized trees(Boruta-ERT)algorithms to address this issue was proposed.To improve the accuracy of our model,we utilized the synthetic minority over-sampling technique to balance the imbalance data sets.The Boruta-ERT prediction model was then used to select features and predict the strip crown.With the 2160 mm hot rolling production lines of a steel plant serving as the research object,the experimental results showed that 97.01% of prediction data have an absolute error of less than 8 lm.This level of accuracy met the control requirements for strip crown and demonstrated significant benefits for the improvement in production quality of steel strip.
摘要为提高果园自主移动机器人在山区、丘陵等复杂地形环境下运动路径规划效果,增强机器人野外工作性能,针对果园非结构化布局和起伏地形,本文提出了一种基于改进PF-RRT*(Plane fitting-rapidly exploring random trees star)算法的果园机器人路径规划方法。利用自适应采样步长策略,在果园不同障碍物密度环境下能够灵活地调节随机树扩展步长。采用自适应目标偏置的势场引导采样方法,能够有效引导随机树避开障碍物并向目标点扩展。此外,在随机树扩展过程引入地形评估函数。通过平面拟合技术对地形坡度、稀疏度和粗糙度进行综合评估,确保规划的路径在复杂地形中可通过性和安全性。最后,采用三次样条插值与高斯过程回归对路径进行平滑和优化。在仿真环境中,改进PF-RRT*算法与RRT*、Q-RRT*和PF-RRT*算法相比,轨迹偏差最多减少46.97%,路径长度最多减少7.64%,规划时间最多减少23.58%,且成功率和避障效果均优于对比算法。真实果园行间试验结果表明,与RRT*、Q-RRT*和PF-RRT*算法相比,改进PF-RRT*算法与理想轨迹偏差量减少34.04%、26.19%、27.91%、路径长度减少6.58%、3.16%和4.10%、规划时间减少30.56%、18.25%和33.52%。表明本文算法在果园复杂地形下能够实现自主移动机器人最优路径规划与导航。
基金National Natural Science Foundation of China(No.62173084)Foundation of Shanghai Committee of Science and Technology,China(Nos.23ZR1401800 and 22JC1401403)。
摘要To guide an unmanned aerial vehicle(UAV)flying in complex three-dimensional(3D)environments with unknown obstacles,a novel UAV path planning algorithm named IRRT∗-C2TD3 is proposed.The algorithm combines the rapidly-exploring random tree star(RRT∗)algorithm with the twin delayed deep deterministic policy gradients(TD3)algorithm(a deep reinforcement learning algorithm).By employing exploration strategies from reinforcement learning,IRRT∗-C2TD3 improves the RRT∗algorithm.IRRT∗-C2TD3 is a two-stage path planning algorithm comprising pre-planning and real-time planning.It performs pre-planning of paths by generating paths based on geometric connections toward the goal and smoothing them using cubic B-spline curves.By designing the network architecture and reward function of the TD3 algorithm,real-time planning in unknown environments is achieved based on the pre-planned path from the first stage.Simulation results show that IRRT∗-C2TD3 demonstrates better path planning performance in 3D partially unknown environments than RRT∗-C2TD3,M-C2TD3 and MODRRT∗algorithms.
基金supported by the Science Center Program of National Natural Science Foundation of China(62188101)the National Key Research and Development Program of China(2024YFF0504702)the SiYuan Collaborative Innovation Alliance of Artificial Intelligence Science(HTKJ2023SY502003).
摘要This paper investigates the six degree-of-freedom(6DOF)relative kinodynamic motion planning problem for spacecraft close approach operations,wherein a controlled chaser spacecraft is required to approach a noncooperative space target at a close range under both dynamic constraints and motion constraints.An enhanced version of the bidirectional rapidlyexploring random tree*(BiRRT*)algorithm based on flight zoning(FZ-BiRRT*)is proposed to generate safe,feasible,and nearoptimal relative motion trajectories.In the proposed algorithm,the space surrounding the space target is zoned in a spherical coordinate system based on the collision probability so that specific designs can be made for different phases of the approaching.Subsequently,based on the flight zone,dynamic constraints,and experiential knowledge,a series of modifications are made to the classic BiRRT*algorithm,and a postprocessing step is designed to accelerate convergence and promote search efficiency.Furthermore,a general regression neural network is introduced to fit a smooth and applicable final motion trajectory.Finally,the feasibility of the generated motion trajectory and the superiority of the proposed algorithm is demonstrated by means of numerical simulations.
摘要针对传统RRT(Rapidly-exploring Random Tree)算法在进行机械臂路径规划时存在的采样随机性过大、搜索效率低下、所规划的路径曲折等问题,提出一种基于采样区域限制的改进RRT(Sampling Area Restriction RRT,SAR-RRT)算法。首先,针对随机性过大的问题,通过引入目标偏置策略来增强随机树的目标导向性,并采用球形采样区域以及角度限制策略对算法的采样进行约束,减少算法对无用空间区域的探索。其次,为提升算法的搜索效率,对随机树的节点扩展进行自适应优化,采用多步长扩展,使算法能够充分利用环境与障碍物的信息,同时利用贪婪思想加快随机树的收敛从而缩短路径的生成时间。最后,对初始规划出的路径进行二次优化处理,在去除路径中的冗余点后以三次B样条曲线对路径进行平滑处理,提升所规划路径的质量。实验结果表明,在2维及3维场景下,SAR-RRT算法均可以顺利完成路径规划任务。对比传统RRT算法,改进算法总体上使路径长度降低27.73%,规划时间缩短85.25%,采样点数减少87.19%且所生成的路径更加平滑。
基金the National Natural Science Foundation of China(Grant No.42274119)the Liaoning Revitalization Talents Program(Grant No.XLYC2002082)+1 种基金National Key Research and Development Plan Key Special Projects of Science and Technology Military Civil Integration(Grant No.2022YFF1400500)the Key Project of Science and Technology Commission of the Central Military Commission.
摘要This study focuses on the improvement of path planning efficiency for underwater gravity-aided navigation.Firstly,a Depth Sorting Fast Search(DSFS)algorithm was proposed to improve the planning speed of the Quick Rapidly-exploring Random Trees*(Q-RRT*)algorithm.A cost inequality relationship between an ancestor and its descendants was derived,and the ancestors were filtered accordingly.Secondly,the underwater gravity-aided navigation path planning system was designed based on the DSFS algorithm,taking into account the fitness,safety,and asymptotic optimality of the routes,according to the gravity suitability distribution of the navigation space.Finally,experimental comparisons of the computing performance of the ChooseParent procedure,the Rewire procedure,and the combination of the two procedures for Q-RRT*and DSFS were conducted under the same planning environment and parameter conditions,respectively.The results showed that the computational efficiency of the DSFS algorithm was improved by about 1.2 times compared with the Q-RRT*algorithm while ensuring correct computational results.
摘要针对六自由度工业机器人在复杂的分拣环境中分拣速度慢、避障效果差等问题,提出了一种融合人工势场(Artificial Potential Field,APF)算法的快速扩展随机树(Rapidly-exploring Random Tree,RRT)改进算法。传统RRT算法路径规划随机性强、收敛速度慢,在该算法中引入APF机制引导其向目标点进行有效扩展,减少路径搜索过程中的无效分支,提高搜索效率;优化对父系节点的选择策略,对原路径局部节点进行优化重连,提高路径质量及平滑性。根据实际分拣中可能出现的状况,在MATLAB软件中建立了3个不同的仿真场景,并将所提出的改进APF-RRT算法与传统RRT算法、APF-RRT算法进行对比仿真实验。结果表明,改进APF-RRT算法于不同分拣环境中,在路径长度、搜索时间、节点个数和迭代次数4个指标上均有一定提升,能以更高的效率搜索到更高质量的路径。