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A screw theory-based methodology for approximate static balancing of mechanisms
  • Neider Nadid Romero ,
  • Rodrigo S Vieira ,
  • Daniel Martins
Neider Nadid Romero
Universidade Federal de Santa Catarina

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Rodrigo S Vieira
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Daniel Martins
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Abstract

A statically balanced mechanism remains in equilibrium at any position in its range of motion, which is desirable in many devices since minimal or no actuator action is required to support the weight of the mechanism; furthermore, improved energy efficiency, simplified control, and inherent safety are some additional properties of statically balanced devices. Although static balancing has been formally studied for several decades, practical applications remain challenging. The static balancing procedures in the literature are not very general and only work for specific cases. This paper presents a methodology based on screw theory for approximate static balancing of mechanisms. The proposed approach is based on the integration of natural coordinates in screw theory, which allows a systematic mathematical formulation of the optimization problem where the objective is to minimize the actuating forces or torques required to maintain the equilibrium of the mechanism. The developed methodology is applicable to planar or spatial mechanisms of open or closed kinematic chains. The first application example shows the step-by-step of the proposed methodology. A second example shows the balancing of an RSSR-SS spatial mechanism, and a third example shows the balancing of a manipulator robot. In all three application examples, a considerable reduction in the actuation requirements is evident, which is sufficient for practical purposes.