On-line collision avoidance for collaborative robot manipulators by adjusting off-line generated paths: An industrial use case

• Published in: Robotics and autonomous systems Vol. 119; pp. 278 - 288
• Main Authors: Safeea, Mohammad, Neto, Pedro, Bearee, Richard
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.09.2019; Elsevier
• Subjects: Assembly; Collaborative robotics; Collision avoidance; Engineering Sciences; Industry; Collaborative robotics; Industry; Collision avoidance; Assembly; Software; General Mathematics
• ISSN: 0921-8890; 1872-793X
• DOI: 10.1016/j.robot.2019.07.013

Human–robot collision avoidance is a key in collaborative robotics and in the framework of Industry 4.0. It plays an important role for achieving safety criteria while having humans and machines working side-by-side in unstructured and time-varying environment. This study introduces the subject of manipulator’s on-line collision avoidance into a real industrial application implementing typical sensors and a commonly used collaborative industrial manipulator, KUKA iiwa. In the proposed methodology, the human co-worker and the robot are represented by geometric primitives (capsules). The minimum distance and relative velocity between them is calculated, when human/obstacles are nearby the concept of hypothetical repulsion and attraction vectors is used. By coupling this concept with a mathematical representation of robot’s kinematics, a task level control with collision avoidance capability is achieved. Consequently, the off-line generated nominal path of the industrial task is modified on-the-fly so the robot is able to avoid collision with the co-worker safely while being able to fulfill the industrial operation. To guarantee motion continuity when switching between different tasks, the notion of repulsion-vector-reshaping is introduced. Tests on an assembly robotic cell in automotive industry show that the robot moves smoothly and avoids collisions successfully by adjusting the off-line generated nominal paths. •On-line collision avoidance for collaborative robot manipulators.•Adjusting off-line generated paths.•Motion continuity when switching between different tasks.•Assembly robotic cell in automotive industry.