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Self-Sensing Electroadhesive Polymer Gripper with Magnetically Controllable Surface Geometry

- Authors: Dirk Sindersberger1, Gareth J. Monkman2
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View Affiliations Hide AffiliationsAffiliations: 1 Ostbayerische Technische Hochschule Regensburg, Regensburg, Germany 2 Ostbayerische Technische Hochschule Regensburg, Regensburg, Germany
- Source: Soft Robotics , pp 60-89
- Publication Date: April 2022
- Language: English
Compared to most conventional industrial end effectors, electroadhesive grippers enable the handling of sensitive, soft, or air-permeable materials [1]. This makes them highly suitable for integration into soft robotic designs. The prehension force is based on a strong electric field generated by electrodes resulting in a polarisation of the dielectric and the generation of mirror charges in the workpiece. When the electrode supply voltage is deactivated, the electric field rapidly drops, but an electrostatic field remains due to the remanent polarisation of the dielectric. The residual charge on the gripper surface reduces only slowly and, in combination with other influencing factors, can prevent the workpiece from being ejected temporarily or completely. A solution to this problem is presented by means of a magnetically deformable soft gripper surface based on a combination of gripper dielectric and a magneto-active polymer (MAP) actuator. The increased distance between the workpiece and the dielectric enables precise and controlled workpiece ejection. In addition to compliance and deformability, the employment of soft smart materials enables the integration of self-sensing mechanisms for the measurement of surface deformation. Direct mechanical coupling between the magnetic polymer and the electrodes allows the actual deformation of the surface to be determined. The ability to measure this deformation allows the magnetic field to be increased until the required displacement is reached, regardless of the prevailing adhesion forces. Since electroadhesive forces are also dependent on the workpiece materials, simply applying a fixed magnetic flux would not be sufficient to achieve the same deformation for every material. The self-sensing capability is independent of the gripping process and can therefore also be used to recognise a particular surface topology. By applying a mechanical force, the end effector can be pressed onto a three-dimensional workpiece, causing the surface to deform inwards and physically comply with the workpiece shape. The deformation achieved can then be targeted by the magnetic drive before each gripping process, thereby creating optimum contact with the workpiece. Ejection of the workpiece then follows by means of an inverse process, whereby the deformation of the surface is reversed and the workpiece ejected by reducing the contact area. Embedded electrically conductive thermoplastic electrodes within the soft silicone dielectric have the necessary flexibility to support such movements whilst serving as the necessary electrodes for electroadhesion. Since the implementation of the end effector is based entirely on soft materials, the self-sensing magnetically controllable electroadhesive gripper (SMEG) can be produced in a simple shape deposition manufacturing (SDM) process [2, 3] and is highly applicable to the field of soft robotics [4].
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