Design and Fabrication of Micro Gripper Using Functional Fluid Power

Gripping and holding mechanism of automated systems in manufacturing and distribution industries are required to flexibly accommodate various product shapes. In recent years, the gripping and holding mechanisms using jamming transition have been attracting attention because they can grasp objects of various shapes. The jamming gripping mechanism generally requires a mechanical vacuum pump to adjust the internal pressure of the gripping part, and it is difficult to miniaturize the system. An electro-conjugate fluid (ECF), a type of functional fluid, can generate a strong jet flow by applying a high DC voltage between the positive and negative electrodes. The ECF jet flow has a great potential to realize micro fluid power sources. In this paper, we proposed and prototyped a new type of small gripping and holding mechanism that uses the jet flow generated by the ECF and the jamming of granular material. A prototyped micro gripper had an outer diameter of 14 mm, a total length of 40 mm, and a tip diameter of 10 mm for gripping. A mathematical model of the micro gripper was derived by deformation of an elastic membrane and volume and pressure changes. It was verified by the mathematical model that the supplied pressure of the ECF hydraulic power source was large enough to realize gripping performance of the prototyped jamming gripper. The performance of the prototype micro gripper was numerically and experimentally evaluated the mathematical model. It was experimentally clarified that a maximum holding force of the prototyped jamming gripper was shown under the condition that filling rate of granular material was 50%. It was also clarified that the micro gripper with a built-in vacuum pump using the ECF hydraulic power source had a gripping force of up to 93 mN at an applied DC voltage of 4 kV.