Multi-directional crawling robot with soft actuators and electroadhesive grippers

This paper presents the design of a planar, low profile, multi-directional soft crawling robot. The robot combines soft electroactive polymer actuators with compliant electroadhesive feet. A theoretical model of a multi-sector dielectric elastomer actuator is presented. The relation between actuator stroke and blocking force is experimentally validated. Electrostatic adhesion is employed to provide traction between the feet of the robot and the crawling surface. Shear force is experimentally determined and forces up to 3N have been achieved with the current pad design. A 2D multi-directional gait is demonstrated with the robot prototype. Speeds up to 12mm/s (0.1 body-lengths/s) have been observed. The robot has the potential to move on a variety of surfaces and across gradients, a useful ability in scenarios involving exploration.</p

Performance optimization of a conical dielectric elastomer actuator

Dielectric elastomer actuators (DEAs) are known as &lsquo;artificial muscles&rsquo; due to their large actuation strain, high energy density and self-sensing capability. The conical configuration has been widely adopted in DEA applications such as bio-inspired locomotion and micropumps for its good compactness, ease for fabrication and large actuation stroke. However, the conical protrusion of the DEA membrane is characterized by inhomogeneous stresses, which complicate their design. In this work, we present an analytical model-based optimization for conical DEAs with the three biasing elements: (I) linear compression spring; (II) biasing mass; and (III) antagonistic double-cone DEA. The optimization is to find the maximum stroke and work output of a conical DEA by tuning its geometry (inner disk to outer frame radius ratio a/b) and pre-stretch ratio. The results show that (a) for all three cases, stroke and work output are maximum for a pre-stretch ratio of 1 &times; 1 for the Parker silicone elastomer, which suggests the stretch caused by out-of-plane deformation is sufficient for this specific elastomer. (b) Stroke maximization is obtained for a lower a/b ratio while a larger a/b ratio is required to maximize work output, but the optimal a/b ratio is less than 0.3 in all three cases. (c) The double-cone configuration has the largest stroke while single cone with a biasing mass has the highest work output

Limpet II: A Modular, Untethered Soft Robot

The ability to navigate complex unstructured environments and carry out inspection tasks requires robots to be capable of climbing inclined surfaces and to be equipped with a sensor payload. These features are desirable for robots that are used to inspect and monitor offshore energy platforms. Existing climbing robots mostly use rigid actuators, and robots that use soft actuators are not fully untethered yet. Another major problem with current climbing robots is that they are not built in a modular fashion, which makes it harder to adapt the system to new tasks, to repair the system, and to replace and reconfigure modules. This work presents a 450 g and a 250 × 250 × 140 mm modular, untethered hybrid hard/soft robot—Limpet II. The Limpet II uses a hybrid electromagnetic module as its core module to allow adhesion and locomotion capabilities. The adhesion capability is based on negative pressure adhesion utilizing suction cups. The locomotion capability is based on slip-stick locomotion. The Limpet II also has a sensor payload with nine different sensing modalities, which can be used to inspect and monitor offshore structures and the conditions surrounding them. Since the Limpet II is designed as a modular system, the modules can be reconfigured to achieve multiple tasks. To demonstrate its potential for inspection of offshore platforms, we show that the Limpet II is capable of responding to different sensory inputs, repositioning itself within its environment, adhering to structures made of different materials, and climbing inclined surfaces