Kinematics Modeling and Workspace Analysis of a Cable-based Parallel Manipulator for Shoulder Rehabilitation

The science of rehabilitation showed, in most cases, that repeated movements of human members can to help the patient regain the functions of the member injury. Robots for these tasks can be more efficient in performing these exercises than humans. Robotic systems for rehabilitation can be generally used to record information like position, trajectory, force and velocity exploiting the motor performance during active movements, and to guide the movement of a patient limb attached to the device. The cable-based parallel manipulator consists of a moving platform, which can carry an end-effector, and a base. These two elements are connected by multiple cables that can extend or retract. These structures have characteristics that make them suitable for rehabilitation purposes like large workspace which may be adapted to different patient and different training, the mechanical structure is easy to assembly and disassembly and can be reconfigurated in order to perform different therapies, can be easy to transportation and have low cost and simple maintenance which are relevant characteristics for possible commercial system to be used by patients at home. This paper presents a cable-based parallel structure for rehabilitation of the movements of the human shoulder named CaMaReS (Cable Manipulator for Rehabilitation of Shoulder). The robotics structure consists of four cables that allow the shoulder movements with different limits of movement and speed. After kinematics modeling, the kinds of workspace are defined then a statically reachable combined workspace for different geometric structures of fixed and moving platform is obtained. This workspace is defined as the situations of reference point of the moving platform, center of mass, which under external forces the moving platform should be in static equilibrium under conditions that length of all cables must not be exceeded from the maximum value and all of cables must be at tension. The development of this robotic device is justified by the large number of people with shoulder problems like stroke, polio, arthritis and disaster recovery.