Automatic Structural Identification and Vibration Suppression of Industrial Robots using a Custom Active Damper

Industrial robots experience low frequency vibrations at the tool induced by rapid movements, base vibrations, and process forces. In precision applications such as robotic machining, tool vibrations can lead to poor surface finish and tolerance violation. Active vibration control can suppress vibrations in real time and increase a robot’s dynamic stiffness provided the structural modes of the robot are accurately known. This paper presents a custom active damper that is capable of both automatic frequency response function (FRF) measurement and active vibration control. The active damper, which consists of a linear voice coil actuator, moving mass, and on-board accelerometer, excites the structural modes of the robot by applying a sine sweep force input. A dynamic model is derived from the FRF, which allows for efficient tuning of the direct velocity feedback controller within a simulation environment. The performance of the active damper is experimentally validated on a Staubli RX90CR industrial robot. Experimental results show a significant reduction of the dominant structural mode subject to hammer tests and base vibrations.