Preliminary mechanical analysis of an improved amphibious spherical father robot

In recent years, considerable underwater robotics research has focused on manipulating sophisticated systems for inspecting and maintaining underwater structures, which can include cluttered and complex areas such as narrow clear spaces. These robots may be used for feature and cable tracking, deep-ocean exploration, and to carry out tasks in environments full of coral reefs (Zhang et al. 2004; Mori and Hirose 2006). Many researchers have focused on downsizing their robots by optimizing their structures and employing smaller motors (Ha and Goo 2010; Wang et al. 2011). However, traditional motor-actuated robots have challenges related to their limits in size and the power consumption of their motors. Consequently, smart actuators are being used to develop micro-robots (Chen et al. 2010; Villanueva et al. 2010). Smart actuators are usually simple and light, and some of them have low power consumption, leading to various new small robots and new movement methods. These actuators include ionic polymer metal composite (IPMC) and smart memory alloy (SMA) actuators (Brunetto et al. 2008; Abdulsadda and Tan 2012; Shi et al. 2011, 2012a, 2012b, 2013a; Guo et al. 2012a). In our previous research, we developed a micro-robot utilizing two IPMC actuators and a short-range proximity sensor. We also designed an electronic mechanical model to evaluate the grasping ability of a robot using different voltages, and added eight bio-mimetic IPMC legs to implement walking and rotating motion (Shi et al. 2012b, 2013c). Abstract Amphibious micro-robots are being developed for complicated missions in limited spaces found in complex underwater environments. Therefore, compact structures able to perform multiple functions are required. The robots must have high velocities, long cruising times, and large load capacities. It is difficult to meet all these requirements using a conventional underwater micro-robot, so we previously proposed an amphibious spherical father–son robot system that includes several micro-robots as son robots and an amphibious spherical robot as a father robot. Our father robot was designed to carry and power the son robots. This paper discusses improvements to the structure and mechanism of the father robot, which was designed to have a spherical body with four legs. Based on recent experiments in different environments, we have improved the father robot by adding four passive wheels, and we have redesigned its structure by means of three-dimensional printing technology, resulting in greatly improved velocity and stability. Moreover, due to the complexity and uncertainty of many underwater environments, it is essential for the father robot to have adequate structural strength. We analyzed the movement