Reliable software architecture design with EtherCAT for a rescue robot

Modern robot researches focus on disaster response to carry out several missions by a robot itself. Robot software should handle a large number of calculation under real-time constraints. And also, the software design should be complex to process a lot of sensors, which increases a number of factors to consider for the system performance. In this paper, we present the software architecture design for the rescue robot which rescues a wounded person and moves dangerous objects in disaster situations. The software architecture is designed with real-time APIs from a Xenomai real-time kernel patch. The architecture uses EtherCAT which is an Ethernet-based real-time network to communicate with all joint controllers. The processors in the architecture communicate each other by the shared memory. We study two considerations to improve the performance and reliability. First, we present a method to minimize the memory synchronization procedure which is a drawback of the shared memory communication. We also consider processor affinity for all real-time tasks in the architecture to stabilize execution time of high priority tasks.