In the field of soft robotics, granular jamming is a newly adopted variable stiffness mechanism involving the use of vacuum pressure to control soft, particulate matter to become a unified, solid-like structure. However, granular jamming is conventionally controlled with air, which reduces the mobility of the robot. This is because the compressibility of air requires large vacuum pumps or chambers. Instead, we propose the use of an incompressible fluid, such as water, to control the stiffness of the mechanism. This paper presents comparative studies that shows that a hydraulic granular jammed joint using deaired water can both achieve the same stiffness level with just one twentieth of the volume extraction and maintain the same hysteresis level of an air-based system.
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