A combined feedforward-feedback control strategy for improving the dynamics of a flexible mechanism

Modern high-speed mechanisms often experience undesirable vibrations, which may render a required accuracy unattainable or, even worse, lead to a failure of the whole process. Instead of suppressing the vibration by a stiffer design, active control methods may greatly improve the system performance and lead the way to a reduction of the mechanism's weight. We investigate a four-bar-linkage mechanism and show that by introducing an additional degree of freedom for a controlled actuator and providing a suitable control strategy, the dynamically induced inaccuracies can be substantially reduced and new reference paths be described. The modeling of the four-bar-linkage mechanism as a hybrid multibody system and the modeling of the complete system including the actuator is briefly explained. From the combined feedforward-feedback optimal control approach presented in [11], a time-varying output control law is derived that leads to a very good system performance for both a regulating and a tracking problem. The experimental results show the effectiveness of the applied control strategies.