A Multifunctional Underwater Biomimetic Microrobot

Abstract

Robots play an important role in underwater monitoring and recovery operations, such as pollution detection, submarine sampling and data collection, video mapping, and object recovery in dangerous places. However, regular-sized robots may not be suitable for applications in some restricted underwater environments. Accordingly, in previous research we designed several novel types of bio-inspired microrobots, using ionic polymer metal composite (IPMC) and shape memory alloy (SMA) actuators. These microrobots possess some of the attributes of compact structure, multifunctionality, flexibility, and precise positioning. However, they lack the attributes of long endurance, stable high speed, and large load capacity necessary for real-world applications. To overcome these disadvantages, we propose a mother-son robot system, composed of several microrobots as sons and a newly designed amphibious spherical robot as the mother. In this system, the mother robot is actuated by four water-jet propellers and eight servomotors, capable of providing stable high speed and carrying the microrobots to the desired target location where tasks are to be performed. Generally speaking, compact structure, multifunctionality, and precise positioning are considered incompatible characteristics for underwater microrobots. To realize the necessary multifunctionality for adapting to complex underwater environments, we introduce a walking biomimetic microrobot with two kinds of motion attitudes: a lying state and a standing state. The microrobot uses eleven IPMC actuators to move and two SMA actuators to change its motion attitude. In the lying state, the microrobot implements stickinsect-inspired walking/rotating motion, fishlike swimming motion, horizontal grasping motion, and floating motion. In the standing state, it implements inchworm-inspired crawling motion in two horizontal directions and grasping motion in the vertical direction. We constructed a prototype of this biomimetic microrobot and evaluated its walking, rotating, and floating speeds experimentally. The experimental results indicated that the robot could attain a maximum walking speed of 3.6 mm/s, a maximum rotational speed of 9°/s, and a maximum floating speed of 7.14 mm/s. Obstacle-avoidance and swimming experiments were also carried out to demonstrate its multifunctionality.