Design and modeling of a cable-driven articulated robot intended to conduct lower limb recovery training

The proposed cable-driven articulated robot (CDAR) is composed mainly of an articulated-multibody system which is connected to three cables, and can perform sitting type rehabilitation therapies for lower extremity. Adding torsion springs to the rotary joints of CDAR ensures that all cables are always in tension. The arrangement of kinematics in the sagittal plane is presented for motion control and the corresponding optimization problems with strongly nonlinear characteristics are developed. After, the particle swarm optimization method is used to determine the dimensions of the mechanism and the optimum attachment position of the cable. Further, the system dynamics is derived based on Newton-Euler method to help analyze the force profiles and the stiffness of the robot is described when considering compliant impacts of the structural joints. Finally, experimental results demonstrated that the designed robot can fulfill lower limb rehabilitation with advantages such as being lightweight, low-cost, and having simple transmission.