Stiffness Analysis for an Optimal Design of Multibody Robotic Systems

Abstract

Robots are widely used to help human beings and/or to execute various manipulative tasks in industrial applications and even in non-industrial environments. Researchers are still widely investigating robotics with the aim to further improve a robot performance and/or to enlarge their fields of application. These tasks can be achieved only when the peculiarities in Kinematics and Dynamics behaviors are properly considered since the early design stage. Significant works on the topics can be considered the pioneer papers (Shimano & Roth, 1978), (Vijaykumar et al., 1986), (Paden & Sastry 1988), (Manoochehri & Seireg 1990), and more recently the papers (Angeles 2002), (Hao & Merlet, 2005), (Carbone et al. 2007), just to cite a few references in a very rich literature. Algorithms have been proposed, for example, as based on workspace characteristics (Schonherr, 2000), and global isotropy property (Takeda, & Funabashi,1999), separately. Several (often conflicting) criteria can be taken into account in the design process. Only recently, it has been possible to consider simultaneously several design aspects in design procedures for manipulators. Multi-criteria optimal designs have been proposed for example in (Ottaviano & Carbone 2003), (Hao & Merlet, 2005). The significance of each design criterion is often strongly related with specific application task(s) and constraints. Therefore, in this chapter several design criteria are overviewed with specific numerical evaluation procedures for analytical definition of design optimization problems. But, among the design criteria special attention is addressed to stiffness, since it can be considered of primary importance in order to guarantee the successful use of any robotic system for a given task (Ceccarelli, 2004). Indeed, there are still open problems related with stiffness. Still an open issue can be considered, for example, the formulation of computationally efficient algorithms that can give direct engineering insight of the design parameter influence on stiffness response. There is also lack of a standard procedure for the comparison of stiffness performance for different multibody robotic architectures. Therefore, this chapter is also an attempt to propose a formulation for a reliable determination and comparison of the stiffness performance of multibody robotic systems by means of proper local and global stiffness performance indices. Then, the proposed numerical procedure is included into a multi-objective optimal design procedure, whose solution(s) can be achieved 11