Trajectory and velocity planning of the robot for sphere-pipe intersection hole cutting with single-Y welding groove

• Published in: Robotics and computer-integrated manufacturing Vol. 56; pp. 244 - 253
• Main Authors: Liu, Yan, Liu, Ya, Tian, Xincheng
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.04.2019; Elsevier BV
• Subjects: Algorithms; Compensation; Cutting tools; Machine tools; Model forms; Optimization; Pipes; Process parameters; Robot machining; Robots; Single Y-groove; Sphere-pipe intersecting curve; Spheres; Surface treatment; Three dimensional models; Tool compensation; Trajectory planning; Velocity; Welding; Sphere-pipe intersecting curve; Trajectory planning; Tool compensation; Robot machining; Single Y-groove
• ISSN: 0736-5845; 1879-2537
• DOI: 10.1016/j.rcim.2018.10.005

•The proposed sphere-pipe model can cover most of the intersection structures (commonly used in actual machining). And this model integrates the essential characteristics of the intersecting curve and the groove features. The parameterized input interface makes modeling and programming more simple and efficient.•Through the geometric analysis of the above model, this paper uses coordinate systems to describe the reference intersecting curve, single Y-groove and robot tool compensation interface. At the same time, the spatial relationship between coordinate systems is expressed using the homogeneous transformation matrix. The practice has proved that this approach is conducive to achieving functional modularity.•To apply to most industrial robots and their programming rules, this paper gives the description of robot trajectory (function of time) in Cartesian coordinate system based on the final homogeneous matrix. And according to different interpolation modes of the robot controller, two algorithms of TCP speed planning are proposed in this paper, and the stability of speed is verified by actual cutting experiments.•In the experiment, the arc voltage is unstable when the plasma arc starts, which is easy to cause large defects such as cutting gaps. This paper gives the setting algorithm of starting pose based on the intersection model, which avoids the problem of cutting gaps and improves the accuracy of groove cutting successfully. The influence of welding preparation and surface treatment of the weldment on welding quality is very important. Single Y-groove technique is a common surface treatment technique in intersecting curve welding. This paper presents a trajectory and velocity planning method for robot to machine a spherical single Y-groove. First, the geometrical models of the sphere-pipe intersection and the single Y-groove are established. This model can cover most of the intersection modes and parameterizes the groove angle and root face height to obtain the optimum process parameters. The above model forms the basis of robot trajectory planning and is the core innovations of this paper. Based on this model and the principle of three-dimensional tool compensation, our paper designs the interface of cutting robot tool compensation. Through this interface, the operators can flexibly change the radius to adapt to different tools or cutting torches, which can fulfill the requirements of dynamic compensation. As the goal of our paper, this method gives a general trajectory description of the robot and introduces two algorithms for the velocity planning to ensure the stability of the robot velocity. Finally, this paper takes the plasma cutting as example, and gives the relevant algorithm to solve the optimal start position and orientation of the plasma torch, which can avoid the cutting defects.