Active vibration control for robotic machining

Due to their flexibility, low cost and large working volume, 6-axis articulated industrial robots are being used increasingly for drilling, trimming and machining operations. However, producing high quality components has proven to be difficult, as a result of the inherent problems of robots, including low structural stiffness, hence excitation of structural modes, low positional accuracy, and bandwidth limitations associated with dynamics and control. These limit robotic machining to noncritical components and parts with low accuracy and surface finish requirements. As a part of the "Light Controlled Factory" project at the University of Bath, studies have been carried out to improve robotic machine capability, specifically positioning accuracy and vibration reduction. This paper describes experimental studies in reducing robot machining vibrations induced by cutting forces with active vibration control, using accelerometers to measure vibration and inertial actuators to mitigate vibration forces. With a relatively simple controller, a 25% reduction of RMS vibration amplitude is demonstrated.