Optimal design for a gravity-balanced compliant mechanism

This article develops a new gravity-balanced mechanism by using a compression spring in combination with a tension spring. The static equilibrium principle is employed to calculate the relationship between the stiffness of two springs. Then, this article employs a multi-objective genetic algorithm (MOGA) to determine the optimal values for both springs. The results indicate that the stiffness of a compression spring is approximately 2 N/mm, while the stiffness of a tension spring is equivalent to 0.3 N/mm. Using the MOGA, the compression spring has a height of 16 mm, a beam length of 7 mm, and a spring thickness of 1 mm. The results of the tension spring determined that the height is 28.5 mm, the beam length is 17 mm, and the tension spring thickness is 1 mm. The experiments revealed that the compression spring achieves a working displacement of 12.18 mm, while the tension spring achieves a displacement of 13.38 mm. Ultimately, the construction of the balancer relies on both springs. The proposed gravity-balanced mechanism effectively balances the robotic arm, according to the results.