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SUMMARYThis paper investigates a comparative kinematic analysis between nonredundant and redundant 2-Degree Of Freedom parallel manipulators. The nonredundant manipulator is based on the Five-Bar mechanism, and the redundant one is a 3-RRR planar parallel manipulator. This study is aimed to select the best structure for a haptic application. This latter requires a mechanism with a desired workspace of 10 cm × 10 cm and an admissible force of 5 N in all directions. The analysis criteria are the accuracy of the forward kinematic model and the required actuator torques. Thereby, the geometric parameters of the two structures are optimized in order to satisfy the required workspace such that parallel singularities are overcome. The analysis showed that the nonredundant optimally designed manipulator is more suitable for the haptic application.

Summary This paper deals with a continuous design task of a planar cable robot used in a gait training machine called the cable-driven legs trainer. The design of cable robots requires satisfying two constraints, that is, tensions in the cables must remain non-negative, and cable interferences should be avoided. The carried design approach is based on interval analysis, which is one of the most efficient methods to obtain certified results. The constraints of non-negative tensions and cable to end-effector interference are solved using interval analysis tools. By means of a dynamic simulation, the reached workspace and the produced wrenches of the cable robot are evaluated as a set of interval vectors. An optimization algorithm is then designed to optimize the cable robot structure for the gait training machine. The robot is designed to produce non-negative tensions in the cables and to avoid collision at all times within the desired workspace and under the required external loads.