Compensation of Errors in Robot Machining with a Parallel 3D-Piezo Compensation Mechanism

AbstractThis paper proposes an approach for a 3D-Piezo Compensation Mechanism unit that is capable of fast and accurate adaption of the spindle position to enhance machining by robots. The mechanical design is explained which focuses on low mass, good stiffness and high bandwidth in order to allow compensating for errors beyond the bandwidth of the robot. In addition to previous works [7,9], an advanced actuation design is presented enabling movements in three translational axes allowing a working range of each axis up to half a millimeter. Based on the presented theoretical dimensioning and finite element simulation translational moves with higher bandwidth can be enabled, due to the parallel design approach of a 3D-Piezo Compensation Mechanism. For realization aspects piezo actuators are chosen due to their fast dynamics and high forces. The realization of the control loop is further outlined. In order to enable a good control performance the set-up of sensing the extension of the piezo actuator is detailed as well as the spindle position used in fast real-time environment. As a result the 3D-Piezo Compensation mechanism unit allows an active adaption of the spindle position in the range of micrometers. A description of the deployment of the compensation unit to a robot machining system as well as first experimental results conclude the paper and prove the proper functioning of the approach and outline the potential of the entire system. Measured robot paths are applied to the compensation unit and analyzed with respect to the reduction of robot path errors