Grasp analysis and a self-adaptive robotic hand with a novel parallel-coupled switchable mode

Traditional underactuated fingers with the coupled and self-adaptive (COSA) grasping mode cannot parallel grip objects; fingers with the parallel and self-adaptive (PASA) grasping mode cannot hook objects. This paper reviewed all grasping modes of underactuated fingers and proposes a novel switching concept to combine the COSA mode and the PASA mode. This paper designs a novel underactuated robotic finger with parallel-coupled switchable (PCSS) mode, called PCSS finger. The PCSS finger consists of a pulley-belt speed-up transmission, an open-loop tendon transmission, two springs, a mechanical limit and a switching mechanism. The PCSS finger can conduct either the PASA grasp or the COSA grasp, being able to grasp a larger range of objects than traditional COSA fingers and PASA fingers.