Active Vibration Suppression in Parallel Mechanisms for Handling and Assembly

摘要

Parallel kinematics offer a high potential for increasing performance of machines for handling and assembly. Due to greater stiffness and reduced moving masses compared to typical serial kinematics, higher accelerations and thus lower cycle times can be achieved, which is an essential benchmark for high performance in handling and assembly. As high accelerations lead to vibrations of the mechanisms tool center point, thus increasing cycle times or decreasing precision, an active vibration suppression is incorporated to further enhance the performance of these parallel robots. This paper focuses on two aspects of vibration suppression in this class of machines, on the one hand the design process for the active members is discussed. Different kinds of piezo-actuators are taken into account and the rationale for choosing surface mounted piezo-patch actuators in combination with CFRP structural parts is given. On the other hand the specific complications of doing control for vibration suppression in parallel robots is presented. As solution a robust control scheme, taking into account the changing properties of the structural dynamics of parallel robots is characterized. Experimental data on the effect of vibration suppression on a 4-DOF parallel mechanism for handling and assembly is presented, demonstrating the validity of the presented concepts.