Performance of a magnetorheological fluid-based robotic end effector

Robotic end effectors are needed for a variety of terrestrial and space-based tasks. End effectors are commonly inspired by the human hand, with a range of complexity, including varying number of fingers, joints and degrees of freedom. Hand and pincher-type grippers can require complicated actuation and/or a significant sensing and control system to ensure proper orientation of the gripper about the target prior to gripping as well as to avoid crushing the target. Universal grippers, most notably exemplified by the universal Jamming Gripper (Brown et al 2010 Proceedings of the National Academy of Science 107, 18809-18814), provide an alternative design that aims to simplify the actuation, sensing and control of robotic fixturing end-effectors. The universal Jamming Gripper is actuated pneumatically, by applying vacuum to granular media, thereby causing the grains to jam, when confined by an external bladder. We present the design and performance of a universal gripper that is actuated by applying a magnetic field, thereby eliminating the need to supply vacuum (and a reinflation source) to actuate the gripper. The magnetic field actuates a magnetorheological fluid composed of a bi-disperse mixture of carbonyl iron grains suspended in a silicone oil. The performance of this novel gripper design is characterized for a range of target sizes and shapes, and gripper design characteristics.