A family of generalized single-loop RCM parallel mechanisms: structure synthesis, kinematic model, and case study

In this paper, a novel family of generalized single-loop remote center of motion (RCM) parallel mechanisms (PMs) based on a spherical surface geometric model is proposed. The underlying principles behind generating RCM motion are intuitively revealed through geometry. The spherical surface geometric models are first constructed through the application of the midperpendicular theorem of chords by utilizing basic geometric elements (point, line, and surface). A general arrangement of generalized single-loop remote center of motion parallel mechanisms (RCM-PMs) is then established by combining the geometric models with the single-loop structure. The construction principle of generalized single-loop RCM-PMs is subsequently derived. By means of the construction principle, a family of generalized single-loop RCM-PMs are synthesized. Additionally, a general kinematic model is established to analyse this family of generalized single-loop RCM-PMs. Finally, a case study is implemented, including the kinematics and performances analysis, and the simulation of a generalized single-loop RCM-PM. The proposed generalized single-loop RCM-PMs possess several advantages, such as a modular structural design, a good drive unit, analytical kinematics solutions, no internal singular configurations, and a large workspace.