Closed-loop control of eccentric presses based on inverse kinematic models

This work shows how to control the ram motion in servo-mechanical presses with non-linear kinematics by means of a model-based closed-loop control. The use of servo drives in forming machines allows for an arbitrarily controlled drive motion and paves the way for modern, more flexible and adaptable forming machines. However, servo-mechanical presses hardly go beyond the closed-loop control of their servo drives. Especially the control of eccentric presses suffers from non-linear kinematics that impede a closed-loop ram motion control. As a result, the actual position, speed and acceleration of the ram are uncontrollable and harmful effects like tilting occur under real process conditions. We present how to precisely control the ram motion by means of a model-based closed-loop control for a multi-point eccentric press. Using position sensors measuring the ram position in three degrees of freedom and the inverse kinematics of the machine, a closed-loop ram motion control is demonstrated. Experiments investigating different types of control under process conditions show a significant improvement in the accuracy of the ram motion.