EPM–MRE: Electropermanent Magnet–Magnetorheological Elastomer for Soft Actuation System and Its Application to Robotic Grasping

Conventional soft robotic grippers have been developed based on soft pneumatic actuators or using smart soft materials, but they need external pressure sources, are easily deteriorated or used in millimetric-scale, which leads to increase of the independency, instability, and vulnerability. In this study, we propose an EPM-MRE (Electropermanent Magnet-Magnetorheological elastomer) actuation system, which strengthens the independency and stability of soft actuation by non-contact magnetic force. We established its fundamental principle and investigated parameter design through developing a suction cup as a robotic gripper. We prototyped an EPM-MRE actuated suction cup based on magnetic-charge and tensile modeling as well as optimized the structure of EPM by introducing axisymmetric EPM with frustum pole and suction cup by introducing bi-silicone structure to uniformly activate MRE membrane. The activation of EPM by different current pulses and suction force affected by contact shapes and air gaps were tested. Evaluations showed that the suction cup could be activated with 10 ms and generate a maximum suction force of 9.2 N at a steady state with 0 J energy consumption. In conclusion, the EPM-MRE soft actuation system can be used as a robotic gripper.