Design and analysis of a gripper with interchangeable soft fingers for ungrounded mobile robots

Despite recent advances in the development of various types of soft grippers, much of it have focused on the implementation of the grippers in static and stable robots like industrial robotic arms. However, for ungrounded mobile robots such as flying robots or space vehicles, position or orientation errors as well as perturbation due to undesirable forces can be more severe for grasping. In lieu of this, the paper presents the development of a soft material based gripper and an investigation of its feasibility to address these challenges. The gripper is designed with a tendon driven mechanism for opening and uses a spring to exert a grasping force on objects. It is also equipped with interchangeable soft fingers which are designed based on the Fin Ray^® effect. The geometry of the fingers is then varied to investigate the effect of varying compliance in the fingers on gripper performance. The experiment results show that the gripper is able to grasp various objects placed within its work envelope with good resistance to errors in object position and orientation. Furthermore, it is shown that compliance of the fingers does not significantly increase the grasping performance of the gripper as long as the object is within its work envelope, but greatly reduces the dynamic reaction force exerted upwards during grasping. The results therefore show the feasibility and advantages of the gripper for ungrounded mobile robots.