CARE Robot: Design and Feasibility Assessment of an End-Effector Based Assistive Robot Manipulator for Adaptive Arm Support

We developed a compact 3-D end-effector type of upper limb assistive robot, named CARE Robot, that provides transparency movement and adaptive arm support control to achieve home-based therapy and training in the real environment. The proposed system composes five degrees of freedom, including three active motors and two passive joints at the end-effector module. The core structure of the system is based on a parallel mechanism. The key innovation of this work lies in developing a novel adaptive gravity compensation framework, uniquely designed to provide 3-D arm support without reliance on external sensors. Unlike conventional methods that require wearable magnetic or IMU sensors, our approach estimates joint angles through a fixed torso model and sagittal plane model, enabling personalized and efficient support force generation. To validate the feasibility of the proposed method, preliminary experiments with four healthy subjects were conducted, demonstrating significant reductions in muscle activity, highlighting the potential of our system to assist in Activities of Daily Living and home-based rehabilitation. The combination of the compact design and sensor-free joint estimation approach sets this work apart, offering a more accessible and efficient robotic solution for upper limb assistive therapy.