QADRALIMB: EMBEDDED TCP ACTUATORS IN SILICONE FOR GRASPING TASKS AND UNDERWATER SOFT ROBOTS

Abstract The behaviors of TCP actuators embedded in silicone depend on several critical parameters such as applied voltage, actuation frequency, pre-tension, resistance of the muscles as well as the geometry and the material composition of the structure in which the muscles are embedded. Out of these, the first three parameters can be controlled during operation. This paper presents experimental results that determine the optimum ranges for these controllable parameters and the characteristics of the structure specifically for a swimming and a grasping application. With respect to the swimming application, a low-profile robotic structure of size Φ340 mm x 12 mm with four limbs was designed and built that was able to swim a vertical displacement of 343 mm in 640 s. The limb designs have also been optimized for a grasping application and few cases of grasping in air and in water against gravity was shown while using a single limb as well as a combination of two limbs. The 2-ply TCP actuators can provide a strain of 12.5% at 300g (2.9N) optimum load and a blocking force of 1.7 kg load (16.7N) when supplied with an electrical input energy of 225 J. One of the experiments showed that the limb was able to hold a maximum load of 35 g (0.34 N) when operated in air. Such a soft structure with embedded TCP actuators has not been demonstrated in underwaters environment and hence adds new knowledge in this area. Furthermore, the paper shows FEM simulation results showing the behavior of a single limb under the effect of gravity which was performed using ANSYS to compare with the behavior found in the corresponding experimental results. This research has potential applications in underwater exploration and manipulation in environments that are toxic or dangerous for human interaction.