Yazar "Akarsu, Cansın" ile FBE- Mekatronik Mühendisliği Lisansüstü Programı'a göz atma
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ÖgeTrajectory generation for industrial robots in presence of wrist singularity(Institute of Science And Technology, 2019-12-05) Akarsu, Cansın ; Bayraktaroğlu, Zeki Yağız ; 518161008 ; Mechatronics Engineering ; Mekatronik MühendisliğiRobotics is a highly interested study field that most likely shapes the future of mankind which is very exciting for scientists and engineers. It is a relatively newer engineering area starting from the late 60s and consisting of different disciplines. From there to now, robots are used almost everywhere, on Mars to Earth, on air to land, in deep space to deep oceans, in factories to houses, in laboratories to hospitals. Surely, this is because of their capabilities in three-dimensional space. They can carry out desired tasks like living beings do and become more intelligent as the time goes on. There are still unsolved problems and active research topics in robotics despite the intense attention. It is possible to see that it is a wide spectrum where plenty of technology branches developed within. New advancements show up inherently and research topics get more complicated with the involvement of different disciplines. Nevertheless, some old problems like inverse kinematics, path planning, or singularity maintain their significance, and suggested solutions vary in the literature. For articulated robots, kinematic singularities are inevitable phenomenons that are caused by the nonlinear relationship between joint space and operational space. At singularities, the instantaneous motion of the end-effector becomes infeasible at least in a spatial direction called degenerate direction. Singularities should be considered as natural constraints of manipulators and had better be handled specially in any task-prior robotic application. Otherwise, whenever the robot arm is at or near singularities, desired end-effector motion in task space may correspond to very high joint speeds and joint torques which are generally impractical. Fundamentally, kinematic singularities of a 6-DOF industrial robot can be classified into three types: shoulder, elbow, and wrist singularities. Shoulder and elbow singularities occur at determined positions of operational space. The former occurs whenever WCP is on the line of the first joint axis and the latter occurs, in simple terms, whenever WCP is on limits of workspace. Generally speaking, if the task is reachable and far enough to the workspace boundaries, it would be sufficient to avoid these singularities. On the other hand, there is not any pre-determined occurrence position for wrist singularity. The degenerate rotation direction is unique for every different end-effector orientation that robot posture forms. Moreover, robot posture may differ with the selected configuration for the same TCP frame. Therefore, in the level of complexity, wrist singularity is superior to other singularities and can be encountered at any position of robot workspace for a given task. This thesis intends to conceive a new analytical solution to the wrist singularity of industrial robots which is known for decades. The overall approach is simply avoiding these wrist singular configurations in applications by regarding kinematic redundancy. Still, avoidance is nothing but a reduction of the workspace to a smaller region that selected robot configuration is not varying. The task may exceed that region even if it is in the workspace. Thus, it is not an exact remedy for this problem. The general solution should be passing through singularity somehow. Certain methods had been applied to both robot control and trajectory generation for singularity-consisting tracking. However, none of these wiped out the infeasible motion of the robot arm whenever it is at singular state. Generally, those methods can be described as a trade-off between tracking error and robot speed. There will be a different viewpoint in this thesis to prove this problem can be solved analytically by defining singular directions on operational space and re-constructing the task in the neighborhood of singularity by concerning these singular directions. If a smooth transition between wrist configurations were possible, all regions of the workspace would become accessible to a continuous path which greatly increases robot capabilities in various applications such as painting, arc welding, laser cutting, water jet, robot machinery, sealing applications, and others. This thesis is mainly aiming contribution to these 5-DOF required continuous processes in which industrial robots are used. After trajectory generated in specified conditions, one can simply load desired joint angles and derivatives to a typical industrial robot and precisely track the path in a continuous application in presence of wrist singular configurations. To explain the problem and the solution clearly, mathematical models are going to be presented for both the robot kinematics side and path planning side. Solutions with the existing methods are going to be shown. Then, our novel solution will be compared with their results in different trajectories.