Real-time stiffness compensation and force control of cooperating robots in robot-based double sided incremental sheet forming

Abstract

In robot-based incremental sheet forming, the forming robot is displaced due to the forming forces and the comparable low stiffness. As the forming forces can not be predicted precisely, the stiffness needs to be compensated based on the measurement of a force torque sensor. While previous approaches used precalculated lookup tables, this publication presents a multi body system robot model that can calculate the displacement of the tool center point in real-time. In incremental sheet forming, the supporting robot is typically force controlled to bring superimposed stress into the forming zone. Unfortunately, this could lead to oscillations in the stiffness compensation. The presented force control approach takes the stiffness compensation into account to ensure a smooth movement of the forming robot. In a series of 30 forming experiments the effectiveness of the developed stiffness compensation and force control is validated.

Prediction of forming accuracy in incremental sheet forming using artificial neural networks on local surface representations

“…1 Forming setup at the chair of production systems (LPS). The forming experiments were carried out by two KUKA KR600 robots, each driven by KRC4 controller (background) [23].…”

“…Therefore, the large workspace, broad distribution, great kinematic flexibility, and comparatively cheap investment costs of industrial robots are all advantageous to the process. Conversely, industrial robots' open kinematic chains result in low system stiffness and deflections as a result of forming forces, necessitating a stiffness compensation during the process [23]. The two distinct tools being used enable DSIF-specific process parameters.…”

Einfluss der Frässpindel-Orientierung auf die Bearbeitungsgenauigkeit beim Fräsen mit Industrierobotern

“…So werden Industrieroboter zunehmend in der Metallbearbeitung eingesetzt, wie z. B. beim Blechumformen, Polieren, Entgraten, Bohren, Schleifen und Fräsen [1][2][3]. Im Gegensatz zu CNC-Maschinen bieten Roboter eine hohe Flexibilität, geringe Investitionskosten pro Kubikmeter Arbeitsraum sowie eine Möglichkeit zur Interaktion mit anderen Maschinen [4].…”