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Jingjing Xu,Zhifeng Liu,Yongsheng Zhao,Yanhu Pei,Qiang Cheng 한국정밀공학회 2019 International Journal of Precision Engineering and Vol.20 No.5
In the bolt looseness detection task of the locomotive system, the robot could be used to highly improve the working efficiency and reliability, but faces the complex static obstacles while planning the path for the robotic motion. In this paper, a path optimization technique is proposed to obtain an optimal path with obstacle avoidance for a redundant robot in the static complicated environment. There are three main contributions in this technique. The first is the solving of the inverse kinematics problem for a redundant robot based on the screw theory and the geometric description, which is general to all robots with rotational joints. The second is the modeling of the spatial constraint, where the pseudo distance is defined based on the plane description of the obstacles and calculated using the spatial analytic geometry knowledge. The third is the presentation of the whole path-planning framework based on the above two contributions, which could largely improve the generality of the presented technique. In this framework, the minimum-time path could be obtained while guaranteeing both the motion stability and obstacle avoidance. Moreover, a real setting that includes an obstacle environment and an 8-DOF robot, is taken as an example to better present the technique. Finally, the simulation experiment was performed in Isight software to verify the effectiveness of the path optimization technique.
Trajectory Planning with Minimum Synthesis Error for Industrial Robots Using Screw Theory
Zhifeng Liu,Jingjing Xu,Qiang Cheng,Yongsheng Zhao,Yanhu Pei,Congbin Yang 한국정밀공학회 2018 International Journal of Precision Engineering and Vol.19 No.2
This work aims to propose a trajectory planning technique to minimize the end-effector synthesis error for industrial robots, while obtaining a stable movement. With ER3A-C60 robot as a research subject, the kinematic and dynamic models are established by using screw theory and Kane equations, and based on that, the end-effector synthesis error is modeled by considering the effects of interpolation algorithm and flexibilities of all joints. The septic polynomial is used to interpolate the via points in each joint space to obtain a stable movement. Finally, the PSO algorithm with suitable parameters is applied to find the minimum synthesis error under kinematic and dynamic constraints. The results show that the optimal synthesis error decreases by 88.94% compared with the initial one, the angular parameters are all far less than the limitations of joints and the optimal movement has a high stability, and this optimal trajectory has better overall performance than that based on the previous technique (with the minimum total motion time). The main contribution is that the proposed trajectory planning technique can significantly improve the tracking precision of the end effector while controlling the motion time within a given span under the requirements of continuous path control.