Estimation and compensation of cutting force induced position error in robot machining system

Recently, industrial robots have been widely used in manufacturing due to their various advantages when compared with other equipment, such as maneuverability in a wide range of workspaces, high degrees of freedom, and flexibility. However, due to the low stiffness, they are difficult to be used for precision metal cutting process those require high position control performance under cutting force. This paper proposes a compensation method that estimates the position error induced by the cutting force and compensates the error by controlling the workpiece position by using additional two-axis servo system. The cutting force model was constructed to estimate the cutting force generated during milling without sensors. The kinematic and stiffness models of the industrial robot were developed to calculate the angular error of each joint and position error of the tool center position caused by cutting force. To verify the performance of the proposed compensation method, series of experiments were conducted under various cutting conditions and compared with traditional on-line compensation method. The position accuracy was increased by 63.68 % after the application of the proposed compensation method.