基于VS-IRRT算法的采摘机械臂路径规划

针对多自由度机械臂在采摘过程中出现的路径规划速度慢、路径成本高以及因视觉定位误差和机械臂关节位置误差引起的采摘失败问题,提出了结合视觉伺服的改进随机快速搜索树算法(Improved rapidly-exploring random trees with visual servoing, VS-IRRT),具体包括改进RRT算法和基于平移控制器的视觉伺服方法。改进的RRT算法通过使用基于超椭球引力偏置的采样方法和密度减小策略,增加树拓展的目的性,减小了树的采样密度,提高路径规划效率;引入贪心思想和B样条曲线,剔除多余节点,对剩下折线进行平滑处理,优化路径在机械臂上的实施效果;结合基于平移控制器的视觉伺服控制,减小了定位误差对采摘过程的影响。使用Matlab分别对改进RRT算法和基于平移控制器的视觉伺服在二维和三维空间中进行仿真模拟试验,结果表明,改进的RRT算法的采样点数较RRT^*-connect算法减少92.9%,规划时间较RRT^*-connect算法减少86.1%,路径成本较RRT算法也减少35.2%。使用六自由度机械臂进行采摘试验,VS-...

Motion Planning of Harvesting Manipulator Based on VS-IRRT Algorithm

Aiming at the problems of slow harvesting, an improved rapidly-exploring random trees with visual servoing (VS-IRRT) algorithm was proposed to solve the problems of slow path planning, high path cost and picking failure caused by visual positioning error and joint position error of manipulator in harvesting process. By using the sampling method based on super ellipsoid gravity bias and density reduction strategy, the purpose of tree expansion was increased, the sampling density of tree was reduced and the efficiency of path planning was improved. The greedy idea and B-spline curve were introduced to eliminate unnecessary nodes, and the remaining polyline were smoothed to optimize the implementation effect of the path on the manipulator. Combined with visual servoing control based on translation controller, the influence of positioning error on harvesting process was reduced. Matlab was used to simulate the improved RRT algorithm and the visual servo based on translation controller in two-dimensional and three-dimensional space. The results showed that the number of sampling points of the improved RRT algorithm was reduced by 92.9% compared with that of RRT*-connect algorithm, the planning time was reduced by 86.1% compared with that of RRT*-connect algorithm, and the path cost was reduced by 35.2% compared with that of RRT algorithm. Using six degrees of freedom manipulator for harvesting test, the harvesting speed of VS-IRRT algorithm was increased by 48.36% compared with that of RRT*-connect algorithm, the path cost was reduced by 17.14% compared with that of RRT algorithm, and the harvesting success rate was increased by 2.1 percentage points, therefore, in specific application scenarios, especially in agricultural harvesting scenarios, VS-IRRT algorithm can better improve the comprehensive performance of manipulator harvesting.