Improved Method for Synchronous Accuracy of Linear and Rotary Axes under a Constant Feed Speed Vector at the End Milling Point while Avoiding Torque Saturation

Abstract

A five-axis machining center is known for its synchronous control capability, which allows complicated three-dimensional surfaces, such as propellers and hypoid gears, to be created rapidly. In this study, we aim to maintain the feed speed vector at the end milling point by controlling two linear axes and a rotary axis with a five-axis machining center to improve the machined surface quality. Previously, we suggested reducing the shape error of machined workpieces by implementing a parameter (referred to as the precedent control coefficient herein) to reduce the differences in the servo characteristics of three axes in the machining method. Moreover, to maintain the feed speed vector at the end milling point when machining complex shapes, a rapid velocity change in each axis is required, which results in inaccuracy due to torque saturation. In this study, to reduce the shape error while avoiding torque saturation during high angular velocity movements, we develop a theoretical method to obtain the suitable precedent control coefficient of each axis based on a block diagram that accounts for torque saturation. The developed method allows shape error reduction and torque saturation avoidance to be realized.