Quasi-static path optimization for industrial robots with dress packs

• Published in: Robotics and computer-integrated manufacturing Vol. 68; p. 102055
• Main Authors: Hermansson, T., Carlson, J.S., Linn, J., Kressin, J.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.04.2021; Elsevier BV
• Subjects: Collision avoidance; Cosserat rods; Deformation; Equilibrium equations; Flexible structures; Formability; Industrial robots; Linear programming; Mathematical models; Mechanical systems; Non-linear programming; Nonlinear programming; Optimization; Parameter optimization; Parameters; Quasi-static simulation; Robot dress packs; Robot dynamics; Robot path optimization; Robots; Static equilibrium; Stud welding; Cosserat rods; Parameter optimization; Non-linear programming; Robot path optimization; Robot dress packs; Quasi-static simulation
• ISSN: 0736-5845; 1879-2537
• DOI: 10.1016/j.rcim.2020.102055

•Quasi-static path optimization can improve and resolve issues in robot programs with respect to the robot dress pack.•A Cosserat rod is a suitable model of a robot dress pack in a quasi-static parameter optimization framework.•Clearance constraints and process requirements are naturally modelled as constraints in the non-linear path optimization problem. Problems with robot dress packs are a major reason for on-line adjustments of robot programs and down-time in robot stations. It is therefore of high value if the physical behaviour of the dress packs can be considered with simulation methods already during the off-line programming process for a robot station. This paper presents a method for quasi-static path optimization for an industrial robot with respect to its deformable dress pack. Given an initial collision-free path generated by an automatic path planner, the via point configurations of the path are optimized with respect to the performance aspects of the dress pack. The method is derived from a general framework for parameter optimization of a mechanical system subject to quasi-static motions and deformations. The optimal parameter values are obtained from numerical solutions to a non-linear programming problem in which the static equilibrium equations of the system hold at discrete times. Due to the large-scale nature of this problem, a dress pack is modelled as a discrete Cosserat rod, which is the preferred choice for modeling large spatial deformations of a slender flexible structure with coarse discretization. The method is applied to an industrial robot moving in-between stud welding operations in a stud welding station. The optimized path reduces the stress in the dress pack and keeps the dressed robot from the surrounding geometry with a prescribed safety clearance during the entire robot motion.