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, leadto a failure of the whole process. Instead of suppressing the vibrationby a stiffer design, active control methods may greatly improve thesystem performance and lead the way to a reduction of the mechanism'sweight.We investigate a four-bar-linkage mechanism and show that byintroducing an additional degree of freedom for a controlled actuatorand providing a suitable control strategy, the dynamically inducedinaccuracies can be substantially reduced and new reference paths bedescribed. The modeling of the four-bar-linkage mechanism as a hybridmultibody system and the modeling of the complete system including theactuator is briefly explained. From the combined feedforward–feedbackoptimal control approach presented in [11], a time-varying outputcontrol law is derived that leads to a very good system performancefor both a regulating and a tracking problem. The experimental resultsshow the effectiveness of the applied control strategies.