Simulation-Based Analysis of the Modal Control of Ball Screw Driven Feed Axes

Feed axes of machine tools often include more sensors and actuators than needed for basic motion generation. In such over-actuated systems, actuator control is typically implemented in an independent manner, without explicit consideration of the dynamic interactions between individual control loops. The performance of such decentralised control schemes is often limited. Modal decoupling enables the system to be separated into individual vibration modes, each controlled independently. The advantage of modal control lies in its ability to simplify the control of complex systems by reducing them to multiple independent single-input, single-output systems. Each control loop corresponds to a specific vibration mode, and its control law can be designed to meet the desired performance requirements. This study presents a simulation-based analysis of modal control applied to feed axes equipped with a ball screw. Two over-actuated configurations are examined. The first consists of a ball screw driven by a single motor, with an optional active damping device attached to the slide. The second configuration features a ball screw driven by two motors, one mounted on each side. Applying modal control increases the position-control bandwidth by up to 60 % when using an active damping device, and by up to 20 % for a dual-motor ball screw axis.