A novel cascade control principle for feed drives of machine tools

Most feed drives in machine tools are designed using ball screw drives. The bandwidth of such drives with conventional PPI control principle is limited by the first natural frequency of mechanical transmission elements. A novel feedback control principle is presented to improve feed drive dynamics. It is cascade structured and consists of a weakly set motor speed controller, a disturbance observer with the feedback velocity of machine table and a PD position controller. This principle increases the bandwidth of the position loop over 200% without any extra sensor or actuator. Experimental results validate the effectiveness and robustness of this principle.