Application of Counter-Rotary Counterweights to the Dynamic Balancing of a Spatial Parallel Manipulator

Abstract

The dynamic balancing of a spatial parallel manipulator of three degrees-of-freedom, CaPaMan-2 (Cassino Parallel Manipulator 2), by the application of Counter-Rotary Counterweights (CRCW) is analyzed. To accomplish this objective the mass and inertia of the moving platform are dynamically replaced by point masses located at the points of attachment of the legs to the platform and the mechanism is balanced by considering each of the legs independently. This fully parallel manipulator has three identical legs, each one composed by a four-bar mechanism (an articulated parallelogram) connected to the fixed base, and a link supported by the coupler that connects to the mobile platform. This link, seen as a pendulum, is transformed to a dynamic balancer using a Counter-Rotary Counterweight in order to compensate the motion of the moving platform. In a second stage the articulated parallelogram is modified by adding Counter-Rotary Counterweight plus a Counterweight to dynamic balance its part of the system. As a final result it is obtained a new design, with a parallel manipulator dynamic balanced. The resulting model of the manipulator is validated by dynamic simulation, using general purpose software for the analysis and dynamic simulation of multi-body systems (ADAMS).