Development and Experiments of a Bio-inspired Underwater Microrobot with 8 Legs

Abstract

In recent two decades, research of underwater microrobots developed at a high speed. They can be widely applied in the field of underwater monitoring operations including pollution detection, video mapping, and exploration of unstructured underwater environments. Based on the underwater monitoring, this kind of microrobot is of great interest for cleaning the micro pipeline in the radiate area, getting samples from the seabed for archeology or mining, and so on (Kim et al., 2005; Behkam & Sitti, 2006; McGovern et al., 2008). For example, some underwater robots with screw propellers have been developed. However, the electromagnetic structure of traditional motors is difficult to shrink. So, motors are rarely found in this sort of application (Zhang et al., 2006a; Wang et al., 2008), and special actuator materials are used instead. As a result, many kinds of smart materials, such as ionic polymer metal composite (IPMC), piezoelectric elements, pneumatic actuator, shape memory alloy, which can be used as artificial muscles, have been reported (Heo, 2007; Park et al., 2007). Although problems such as electrical leakage, water safety, physical bulk, and high stiffness persist in real applications, these smart materials have been widely used as actuators to develop new type of microrobot. Ionic polymer metal composite (IPMC) is an innovative material made of an ionic polymer membrane chemically plated with gold electrodes on both sides. Its actuation characteristics, such as suitable response time, high bending deformation and long life, have significant potential for the propulsion of underwater microrobots. Flexible IPMC propulsion blades operating at low driving voltages provide many new possibilities for underwater locomotion applications (Lee & Kim, 2006; Nakadoi & Yamakita, 2006; Dogruer et al., 2007; Punning et al., 2007; Liu et al., 2008). They have been widely used on soft robotic actuators such as artificial muscles, as well as on dynamic sensors (Guo et al., 2008b; Ye et al., 2008). Now, many kinds of underwater microrobots have been developed using IPMC actuators as artificial muscles to propel the robots back and forth. They are widely used in swimming microrobots as oscillating or undulating fins where fast response is required (Jung et al., 2003; Guo et al., 2004; Kamamichi, 2006; Guo et al., 2007; Brunetto et al., 2008). IPMC actuators are also used for underwater bipedal walking microrobots (Kamamichi et al., 2003; Guo et al., 2006; Yim et al., 2007), and a kind of ion-conducting polymer gel film microleg