Pose-dependent modal behavior of a milling robot in service

The introduction of industrial robots in the machining field represents a large saving in cost and time, given their advantages in terms of high flexibility in a large workspace and the complex machining operations that they can perform compared to a CNC machine tool. However, machining robots are significantly less rigid than machine tools, and present more variability in their dynamic behavior within their workspaces than CNC machine tools. Their considerable lack of rigidity is still a major restriction for precision tasks, and attaining the precision required of a machining robot remains a challenging issue. Thus, a modal parameters analysis of machining robots under real machining conditions, is crucial for a reliable evaluation of its dynamic behavior. Robot configurations can then be adapted to ensure stability conditions along the machining trajectory. The main innovation of this paper is the modal parameter monitoring of a machining robot, in machining conditions, as regards its position and wrist configuration within its workspace, for a more accurate and reliable control of its dynamic behavior. Modal parameters are identified during machining operations using the transmissibility function–based (TFB) method.