Design of Active Rods with Multiple Degrees of Freedom for Vibration suppression in Parallel Robots for Handling and Assembly

Parallel robots demonstrated their potential in applications with needs for high dynamic trajectories in the recent years. In contrast to serial robots they meet the demands for higher accelerations at constant precision due to their lower moved masses and larger structural stiffness. On the other hand higher accelerations increase the risk of severe vibration of the structural parts. Therefore active vibration suppression using rods with embedded piezoceramic actuators is used to counteract these vibrations to reach the goal of short cycle-times in handling processes. Active rods or active members in general were used to build systems for vibration suppression in parallel robots and were presented previously. In this paper a design for rods with multiple active degrees of freedom (i.e. bending, elongation and torsional movement) is presented in the context of parallel robots. This design is using piezoelectric actuators with d33-effect to realize the active deformations. The design process used for building these rods is discussed as it is essential to balance the goal of maximum actuating authority with the demand for the ability to carry structural loads as a robot component. This concept of structural conformity governing the design process in order to build reliable and high-performance rods is elucidated and discussed. The parameters influencing the design are given. Problems of manufacturing the rods are highlighted as boundary conditions to the design process. Parameter studies using an FE model demonstrate the concept and experimental data give evidence of the validity of the mode