Robo-Squid: Experimental investigation of pulsed jet propulsion based on magnetohydrodynamics

As the interest in oceanic and marine technologies increases, there is a growing need to perform construction, maintenance and surveying in ever more complicated situations. Currently, most underwater robots have limitations including manoeuvring in tight spaces, entanglement with foreign objects, ecosystem disruption, and high acoustic noise. A novel pulsatile jet actuator using magnetohydrodynamics (MHD) is proposed to overcome these problems. In this system, there are no moving parts; hence mechanical noise, entanglement and potential ecosystem disruption are reduced significantly. The jet engine operates in, and exploits, the electrical and fluidic properties of seawater. The MHD pulse jet engine was experimentally characterized and maximal thrust generation was achieved by enforcing the optimal formation number. The thrust vortex rings generated were studied using particle image velocimetry in both pulsed flow and continuous flow. We successfully developed an untethered robot using a pulsatile MHD jet and demonstrated its effective movement in salt water. The MHD pulse jet is ideally suited to the next generation of autonomous soft robots for environmental monitoring and protection.