Model-based adjustment of the dynamic behavior of coupled robots for the optimization of milling processes

• Applicant: Professor Dr.-Ing. Jürgen Fleischer
• Subject Area: Production Automation and Assembly Technology
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 577794312

With social and technological change, the demands on production technology are changing. Shorter product life cycles and increasing product diversity and customization options are leading to ever smaller batch sizes. This results in the need for greater flexibility and adaptability in production plants and processes, while maintaining productivity and cost-effectiveness. With the new production system of value stream kinematics, the limits of flexibility and agility are being pushed further. The basic idea of value stream kinematics is to build an entire value stream in a production line from uniform, universal six-axis robot kinematics, which are equipped with specialized end effectors and act collaboratively. These kinematics are realized by standardized 6-axis articulated robots. The collaboration takes place, in part, by coupling the robots. Despite many years of research into the use of robots in machining, their use has not become established due to their low rigidity. Low precision and low natural frequencies, which can lead to chattering due to excitation in the milling process, are further challenges. The present project is to investigate to what extent the tension occurring in the coupled and therefore over-determined system can be used to manipulate the machine-dynamic properties of the coupled robot system in order to improve the machining quality. The aim is to examine what improvements can be achieved by coupling serial robot arms in a parallel kinematic system in terms of machine capability for path accuracy and surface quality in the milling process. The system's tension is to be adjusted in order to suppress the natural oscillations excited by the process. This is done by tensioning the over-determined system by moving the flanges of the robot arms relative to each other. Absolute path accuracy is of crucial importance for carrying out processes that are normally not accessible to industrial robots due to the high demands on the aforementioned accuracy. A stiffness model is being developed to characterize the system. In addition, modal analyses are being carried out to identify the system's eigenmodes. The advantage of this modeling is evaluated by integrating the model-optimal response into the control chain using milling experiments. The aim is to create a model of the system that changes its dynamics by means of tensioning in such a way that chattering is minimized. In order to be able to set the tension correctly, models are created that determine robot configurations in the joint space, the implementation of which results in optimal system dynamics.

• DFG Programme: Research Grants