Cable Driven Gravity Compensation Mechanism

The gravity compensation mechanisms (GCMs) are widely used in robotic manipulators and exoskeletons. We present a cable-driven GCM applied in a spatial multi-degree-of-freedom (DoF) robotic system. By combining the cable transmission with the spring-based GCM, the whole compensation system is placed outside the main body of the robotic system, including the movable links and revolute joints. Therefore, the complexity and inertia of the robotic system’s main body are reduced, and the motion range will not be limited by the mechanism for compensation, such as parallelogram linkages. Here presents the application example of a cable-driven four-DoF exoskeleton to demonstrate the development of the proposed GCM. The GCM is analyzed based on the space mapping method, and the mechanical models are designed based on theoretical analysis to evaluate the technical feasibility. The effectiveness of the proposed GCM is validated by calculating and analyzing the cable tension required by the exoskeleton and generated by the GCM in several specific movements. Finally, some limitations and potential applications of this cable-driven GCM are discussed.

(a) The overview of a four-DoF exoskeleton with the proposed cable-driven GCM. (b) The overview of the proposed four-DoF cable-driven GCM, where the highlighted green cable is a typical transmission cable in the GCM.