Terrestrial and Underwater Locomotion Control for a Biomimetic Amphibious Robot Capable of Multimode Motion

The advancement of mechatronic devices and computer science has provided an impulse to fast-moving robotic technology in last decades. Taking the category of robots as an example, besides the industrial robots for manufacturing, the list of emerging robots for spaceflight, navigation, medical nursing, service, military purposes and so on, are growing (Yang et al., 2007). Further, there are many application-specific robots being developed and used today across a wide variety of domains. An accompanying drawback is that conventional robots can only work in a single working condition. For instance, the terrestrial mobile robots are functionally unable to propel in water owing to lacking necessary aquatic propelling units or waterproof treatment, while the underwater robots mostly have not sufficient locomotion ability on land since the locomotion will undergo stronger friction than it encounters in viscosity medium. Developing versatile robots adapting to changing environments faces significant challenge. Amphibious robots, with dual locomotion for mixed water-land environments, draw great attention and interest from academics and engineers all over the world (Ijspeert et al., 2005, 2007; Healy & Bishop, 2009). No doubt, they are very important tools when executing terrestrial and/or underwater related operations in complex surroundings (e.g. in the combat zone). In particular, military robots are currently being applied to many missions in Iraq and Afghanistan ranging from mine detection, surveillance, as well as logistics to rescue operations. Besides military applications, the welldeveloped amphibious robots that are highly maneuverable and adaptable to changeable terrains will cover more complex real-world missions, including ecological monitoring, amphibious reconnaissance, safety check, search and rescue, etc. Compared with other single-function robots, the existing amphibious robots capable of operating both on land and under water are relatively rare. Generally speaking, they tend to fall into two primary categories: legged and snake-like. Since irregular and uneven terrain is the salient feature of water-land environment, many amphibious robots conventionally utilized leg-like locomotion on rough terrains. Some examples include the lobster robot constructed by J. Ayers group in Northeastern University of US (Ayers, 2004), the ALUV with six legs to duplicate crab by IS Robotics and Rockwell for the purpose of sensing or mine detection (Greiner et al., 1996), as well as the robotic crab built by Harbin Engineering