Control architecture for stable gait of a six-legged subsea robot CR200

This paper presents a control architecture for 200m-class subsea walking robot, named CR200, which can work in strong tidal current and high turbidity environment by crawling sea floor to survey shipwreck and scientific research. The control architecture consists of deliberative layer, execution layer, and hardware abstract layer. Deliberative layer is in charge of the high level control of the CR200. Deliberative layer only gets needed information from execution layer, and puts processing result to execution layer. Deliberative layer does not consider detail process because execution layer includes most essential process for robot control. Hardware abstract layer allows other layers to perform device-independent, and it includes communication module, sensor interface module, and motor interface module. The control architecture has been implemented to a program of operating software. The program runs on Linux operating system, and it supports soft real-time characteristic without real-time operating system. The control frequency of the CR200 is 100 Hz, and standard deviation of software timer occurrence error was 10.375 us. We conducted first sea trial of the CR200 at KIOST's South Sea Research Institute in July 2013, and the CR200 performed well during its first die.