A Novel Kinematically Redundant Orthopedic Robot for Avoiding Interference in Long Bone Deformity Correction

Long bone deformity correction with orthopedic robots is guided by a preplanned correction path, and the continuous implementation of the entire process is highly important for achieving acceptable outcomes. However, multiple types of interference phenomena (i.e., strut overstroke, singularity configuration, and soft tissue-strut collision) frequently occur, which necessitate temporary robot reassembly and path replanning that interrupt the correction process. To solve this issue, this letter introduces the self-motion characteristics of redundant parallel mechanisms into the design of orthopedic robots. On this basis, a novel redundant configuration is proposed, and its mechatronic design is developed. Afterward, on the basis of the kinematic model and the cylinder-elliptical table analytical model, avoidance indices are presented for predictiong the interference state. By integrating the indices and performing weight discrimination, a configuration optimization algorithm is constructed for all interference avoidance tasks. Finally, simulations and prototype experiments demonstrate that the proposed design concept and methodology can assist surgeons in planning an interference-free adjustment scheme and ensure the continuity of the correction process without altering the original robot assembly and correction path.