The CoGripper: a Cooperative Gripper for Smart Factories

Most of the work on collaborative robots (cobots) and more in general on physical human robot interaction have focused on robotic arm design and control. This has led to a novel generation of collaborative robots that can safely interact with a human operator. Although robot end-effectors are most of the time the part of the robot more proximal to the human partner in collaborative scenarios, only a few works have been dedi- cated to the design and the control of collaborative grippers. The Schunk Co-Act Gripper [1] is an example of gripper designed for collaborative robotics, even if it still needs a complex system to be safe and can deal with a limited type of object’s geometries. Another example of a plug–and–play gripper is represented by the RG6 Collaborative Gripper [2], that however can be controlled only through the robotic arm interface thus limiting its applicability in many collaborative contests. We will present a soft–gripper explicitly devoted to an easy and safe interaction with human operators in cooperative tasks. The key ingredient of the softgripper is the intrinsic softness of the device, i.e., its embodied ability to comply and adapt to features of the objects and of the environment. The proposed device, that we named the Co-Gripper (see Fig. 1), is a wireless underactuated tendon-driven gripper, with four flexible fingers composed of three soft- rigid modules each. A wireless implementation allows to easily integrate the gripper both on actuated arms and on passive structures. Also, its control interface is extremely simple and can be used both in industrial and more general service application, without the need for specific knowledge or training for the user. We managed to obtain suitable adaptability and robustness properties, thanks to a tendon based actuation and flexible finger structure, in which joint stiffness is evaluated according to the methodologies that we have proposed in [3]. The gripper has been realized using rapid prototyping techniques, in which we can manage material’s mechanical properties by properly regulating 3Dprinting parameters, and it can easily be reconfigured, due to its modular structure at a finger level. In the design of the device, we have followed four main guidelines. Our proposal is to delineate which are the main features of a novel generation of soft grippers explicitly designed to physically interact with a human operator. To- gether with the automation standards detailed in the ISO/TS 15066 [4], we identified four main principles that a cogripper should have with respect to foster human robot cooperation: i) intrinsic safety and adaptability, ii) easy reconfigurability, iii) portability and iv) easy interface with the human operator [5]