Abstract
To improve the sorting accuracy and efficiency of sorting system with large inertia robot, this article proposes a novel trajectory planning method based on S-shaped acceleration/deceleration algorithm. Firstly, a novel displacement segmentation method based on assumed maximum velocity is proposed to reduce the computational load of velocity planning. The sorting area can be divided into four parts by no more than three steps. Secondly, since the positions of workpieces are dynamically changing, a dynamic prediction method of workpiece picking position has been presented to consider all the possible positions of the robot and the workpiece, so as to realize the picking position prediction of the workpiece at any positions. Each situation in this method can constitute an equation with only one solution, and the existence of the solution can be verified by the proposed graphical method. The simulations of the motion time of the sorting process show that the proposed method can significantly shorten the sorting time and improve the sorting efficiency compared with the previous method. Finally, this method was applied to the Selective Compliance Assembly Robot Arm (SCARA) robot for experiments. In the physical picking experiment, the missing-pick rate was less than 1%, which demonstrates the efficiency and effectiveness of this method.
Highlights
The sorting for the moving workpieces, which is to identify, pick, and place the messy workpieces,[1] is one of the most common applications in modern industrial production.[2]
To achieve accurate positioning of the workpiece, machine vision is widely used in robot sorting system.[4]
A novel displacement segmentation method based on assumed maximum velocity is proposed to reduce the computational load of velocity planning
Summary
The sorting for the moving workpieces, which is to identify, pick, and place the messy workpieces,[1] is one of the most common applications in modern industrial production.[2]. The total motion time is Ttotal 1⁄4 Tup þ Tlevel þ Tdown ð1Þ velocity v s and ending point velocity ve, and the time for each section f1⁄2t1; t2; t3; t4; t5; t6; t7g of the feed rate profile can be calculated by analytical or numerical methods.[22] It is a typical point-to-point (PTP) process that picks the workpiece on the conveyor I and places it in the pallet of the conveyor II.[6] To prevent the vibration caused by the sudden change of the trajectory at the corner, and shorten the motion time, the arc transition mode is adopted at the corner.[23] the “door” path includes three segments: P1P2ðL1Þ, P2P3ðL2Þ, and P3P4ðL3Þ. To facilitate the calculation of the sorting trajectory, this article proposes a novel displacement segmentation method based on the assumed maximum velocity. The part III starts from R3, F is the actual maximum velocity in the motion process. t acc and t dec can be calculated according to vc A1 A2
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