Inter-program communication protocol for operation of six-legged subsea walking robot CR200

This paper presents a communication protocol among operating programs for the CR200, which is 200m-class subsea walking robot with six legs. The number of operating programs is twelve. We have developed six essential programs, which exchange data using designed message protocol through Ethernet. The inter-program communication protocol includes message frame form, message type, transmission process, reception process, and communication sequence. The message frame is divided into header area and data area. The size of header area is two bytes and the length of data area is variable. First byte of header is start-of-frame delimiter, next two bytes indicates the length of data area, and last byte is for message type. There is no error check area because Ethernet communication protocol basically supports error check. Transmission process and reception process varies depending on message type. Some programs only run after valid interaction with other program by specified communication sequence. The protocol mechanism is simple but it was enough to operate the CR200. We successfully finished basin test of the CR200 in April 2014. Subsequently, the CR200 deployed in Sewol ferry disaster site and it supported search operation for three weeks.