Active vibration damping of a machining robot with hybrid drive

• Applicant: Professor Dr.-Ing. Berend Denkena
• Subject Area: Production Automation and Assembly Technology
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 525070922

Due to the low investment costs combined with high flexibility, the use of industrial robots for machining large-volume and easy-to-machine materials is becoming increasingly relevant. However, the advantage of the large working space to installation space ratio of an industrial robot with articulated arm kinematics is offset by disadvantages compared to conventional machine tools in terms of low path accuracy and high susceptibility to vibration. The main reason for this is the high compliance of the robot gear units. The current approaches to reducing structural vibrations lower the drive dynamics or, in the case of active vibration damping, can only dampen the vibration amplitudes in a µm adjustment range. Furthermore, in the methods of active vibration damping, the pose-dependent vibration behaviour of the robot structure is not considered in the control algorithms. A robot developed by IFW with a hybrid drive has a suitably large positioning range due to an additional torque motor. Due to the positioning in the force path of the robot structure, the additional torque motor can therefore also be enabled to actively dampen vibration amplitudes in the mm adjustment range. The currently implemented control algorithm leads to a stiffening of the hybrid axis, so that structural vibrations cannot be specifically damped. Structural vibrations are thus transmitted to the subordinate axis. There are currently no control algorithms with which vibrations of industrial robots can be actively compensated for changing vibration eigenmodes. For active vibration damping of the robot structure with the help of the hybrid drive, model-based control approaches are therefore required that consider the non-linear, pose-dependent vibration behaviour of the robot structure. The overall objective of the project is to present a novel control method for active vibration damping of a robot structure with serial kinematics, considering the pose-dependent vibration behaviour. To achieve this goal, a multidimensional multi-body model is first developed to represent the relevant pose-dependent structural vibrations of the robot structure. Based on the multi-body model, a parameter-variant control method is developed. Finally, the limits of the damping concept in the machining process are explored.

• DFG Programme: Research Grants