Type synthesis of reconfigurable single-loop mechanisms based on transitional configurations

Abstract

This paper presents a general type synthesis methodology for reconfigurable single-loop mechanisms (RSLMs). Unlike conventional approaches that derive RSLMs from classical configurations, this study investigates constraint system variations during transitional configurations of RSLMs. When the RSLM is in transitional configuration, the order of wrench systems reaches its peak. Utilizing this characteristic, we categorize wrench systems according to their order and type, then construct the original single-loop mechanism through the closure of the corresponding wrench system's open-loop kinematic chains. Subsequently, while maintaining the original wrench system configuration, kinematic pairs are added. Further analysis of inactive joints and mechanism reconfiguration characteristics, the optimized RSLM configuration is synthesized. The proposed method generates more generalized RSLM configurations and ensures that the RSLM created is in transitional configurations, thereby facilitating subsequent motion pattern analysis. As validation, multiple novel 6R and 7R RSLMs with single DOF reconfigurability have been successfully synthesized, demonstrating the method's feasibility and effectiveness. Finally, optimization strategies for eliminating inactive joints and structural refinement are proposed. Two application-oriented prototypes are presented to exemplify the practical potential of the synthesized RSLMs.