A New Class of Spring Four-Bar Mechanisms for Gravity Compensation

This paper presents a new class of spring four-bar mechanisms, with fifty-six different mechanism types, for gravity compensation. A synthesized mechanism is realized by linkage combination with a planar four-bar linkage and attachment of a linear spring. The main advantages of the proposed spring mechanisms are their simple architectures and high performances that possess great potential for practical applications. The parameters of the mechanisms for gravity compensation are derived from an optimization approach. Numerical examples are given to demonstrate the performances of the proposed spring mechanisms. The simulation results showed that the motor torques of the mechanisms could be reduced by up to ninety-nine percent with the spring attachment.