Enhancing distal motion-force interaction performance of parallel mechanisms through integration of closed-loop passive limb

• Motion-force interaction performance is analyzed for 5R and its variant mechanisms. • The distal performance is further enhanced by introducing a closed-loop passive limb. • The results guide the design of key structural parameters for the Delta parallel robot. • Variant parameters in closed-loop passive limbs result in different performances. • This work provides an approach for enhancing the performance of parallel mechanisms. Dimensional synthesis is widely recognized as a core approach for enhancing the performance of parallel mechanisms. However, is it possible to improve their performance further? This paper aims to provide a novel method to enhance the performance of a 5R parallel mechanism, which already possesses optimal dimensional parameters, by introducing a closed-loop passive limb. First, typical closed-loop limb-type parallel mechanisms and motion-force interaction performance are introduced as background. Then, the identification of wrenches and twists, and interaction indices for general planar two-degree-of-freedom parallel mechanisms are presented as the mathematical foundation for performance evaluation. Finally, building upon the 5R parallel mechanism with optimal dimensional parameters, its performance is further enhanced by introducing a closed-loop passive limb. The results show that the distal interaction performance of the redesigned kinematic chain is effectively improved through the integration of a closed-loop passive limb. This work provides a new and effective approach for enhancing the performance of parallel mechanisms.