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BALL SCREW DRIVE SYSTEMS: EVALUATION OF AXIAL AND TORSIONAL DEFORMATIONS

Keywords: Screw Drive, Dynamic Model, Vibration Modes, Ritz Series. Abstract. The ball screw drives are among the most commonly mechanisms used to provide motion in high speed machine tools. The most important factor that affects high speed positioning accuracy is the closed loop bandwidth, which in turn is affected by the structural vibration modes. | Asociación Argentina de Mecánica Computacional Mecánica Computacional Vol XXVIII págs. 3265-3277 artículo completo Cristian García Bauza Pablo Lotito Lisandro Parente Marcelo Vénere Eds. Tandil Argentina 3-6 Noviembre 2009 BALL SCREW DRIVE SYSTEMS EVALUATION OF AXIAL AND TORSIONAL DEFORMATIONS Diego A. Vicentea Rogelio L. Heckerab Gustavo M. Floresa Facultad de Ingeniería Universidad Nacional de La Pampa Calle 9 y 110 General Pico La Pampa Argentina vicente@ing.unlpam.edu.ar http www.ing.unlpam.edu.ar bCONICET Keywords Screw Drive Dynamic Model Vibration Modes Ritz Series. Abstract. The ball screw drives are among the most commonly mechanisms used to provide motion in high speed machine tools. The most important factor that affects high speed positioning accuracy is the closed loop bandwidth which in turn is affected by the structural vibration modes. In recent years newer strategies have emerged achieving higher control bandwidth but requiring higher order plant models as well as a better understanding of the system dynamics. This work presents a dynamic model of a lead screw drive accounting for high frequency modes. The analytical formulation follows a comprehensive approach where the screw was modeled as a continuous subsystem. The axial and angular displacement fields for this continuous screw were approximated by Ritz series to obtain an approximate N-degree-of-freedom model. Furthermore it is discussed how to decouple the damping matrix to transform an N-degree-of-freedom system into N one-degree-of-freedom systems because the advantages that this implies when numerical solution is required. Then expressions for the displacement fields in terms of modal coordinates are found and a procedure to compute the axial and angular components of the mode functions is discussed as well as a numerical procedure to compute the system deformation. In order to obtain conclusions about the system behavior in the first modes the axial an angular components of the mode .