Kinetic-Geometric Synthesis of a Reconfigurable 4R Four-bar Multitask Mechanism

This paper proposes a design of a reconfigurable force balanced planar 4R four-bar linkage that can be applied for a variety of three-position motion tasks. Based on given and fixed link lengths of the four-bar linkage, from three-position synthesis the locations of the coupler pivots and base pivots can be derived for a desired set of three poses. With respect to the end-effector at the coupler link the two coupler pivots can be reconfigured in a balanced way with balanced five-bar parallelogram linkages such that force balance of the complete linkage is maintained at any time. Similarly the two base pivots can be reconfigured in a balanced way with balanced five-bar parallelogram linkages such that force balance of the complete mechanism is maintained for motion of the end-effector through any chosen set of three poses. The balance conditions for the complete mechanism are derived step by step with mass equivalent models.