Design and analysis of a cable-driven gravity compensation mechanism for spatial multi-DoF robotic systems

Abstract

The gravity compensation mechanisms (GCMs) are widely used in robotic manipulators and exoskeletons. This paper presents 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.