Extending the life of legacy robots: MDS-ACH via X-Ach

Abstract

Our work demonstrates how to use contemporary software tools on older or “legacy” robots while keeping compatibility with the original control, tools, and calibration procedures. This is done by implementing a lightweight middle-ware called MDS-Ach connected directly to the hardware communications layer of the robot's control system. The MDS-Ach middle-ware, which relies on the x-Ach methodology, was specifically designed for Xitome Mobile Dexterous Social (MDS) Robot which was released in 2008. The MDS Robot is actively used in multiple research facilities including the United States Naval Research Laboratory. This middle-ware gives the MDS Robot the bleeding edge software capabilities of today's robot by implementing the x-Ach real-time processes based computer control architecture. MDS-Ach controls the robot over its low level hardware communications interface (CAN-Bus). This communication controlled and implemented by a real-time daemon process. Controllers communicate with the real-time daemon via a ring buffer shared memory with network capabilities. The ring buffer shared memory is a “first-in-last-out” and is non-head-of-line blocking. All of the latter ensures non-blocking reading and writing of the latest data even while newer data is being added to the buffer. The UDP and TCP protocols can be implemented depending on reliability and timing requirements. Secure communication between networked controllers is implemented via tunneling over SSH if needed. The MDS-Ach middle-ware is designed to allow for simple and easy development with modern robotic tools while adding accessibility and usability to our non-hardware-focused partners. We present an implementation of real-time collision avoidance and a robust inverse kinematics solutions within the MDS-Ach system. We include detailed examples of collision avoidance, inverse kinematics implementation, and the software architecture and tools.