IMPROVED 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, allowing complicated three-dimensional surfaces, such as propellers and hypoid gears, to be quickly created. We aimed 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. In previous research, we suggested reducing the shape error of machined workpieces by applying the proposed method, which uses a parameter (referred to as precedent control coefficient in this research) to reduce the differences in the servo characteristics of the 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, causing inaccuracy owing to torque saturation. In this research, to reduce the shape error while avoiding torque saturation when movement has high angular velocity, we developed a theoretical method to obtain the most suitable precedent control coefficient of each axis by using a block diagram that considers torque saturation. Therefore, both shape error reduction and torque saturation avoidance can be realized by using the proposed method.