Design of a 7-DOF Cable-Driven Arm Exoskeleton (CAREX-7) and a Controller for Dexterous Motion Training or Assistance

The training for both translation and rotation of the hand is desirable for patients with impairments. This paper focuses on the design and control of a 7-degree-of-freedom cable-driven arm exoskeleton (CAREX-7), used for dexterous motion (including translation and rotation) training or assistance of the whole-arm. The CAREX-7 includes an additional wrist module compared with CAREX, and eight cables are routed through the exoskeleton cuffs to drive the whole-arm motion. Based on the “assist-as-needed” paradigm, a novel wrench-field controller was designed to regulate a needed wrench (force and torque) on the hand for assisting its dexterous manipulation. Healthy subjects participated in path-tracking experiments while wearing CAREX-7. The experimental results show that the CAREX-7 with the new wrench-field controller can help the subjects to follow the path more closely, and this demonstrates the effectiveness of the device. The current design of CAREX-7 is unique and offers significant improvements and new functionality over the existing CAREX. The novel features are the following: 1) CAREX-7 is an exoskeleton for the full human arm, including shoulder, elbow, and the wrist, with new design issues; and 2) controller of CAREX-7 builds on a screw-theoretic approach and assists both translation and rotation of the hand, allowing for dexterous hand reorientation, which is required in everyday tasks.