Anthony Redamonti

The Robot Operating System (ROS) is gaining popularity in the robotics industry because it is an open-source platform that solves a common problem: trajectory calculation for complex, multi-axis machines. However, users are faced with the issue of sending the trajectory information in a reliable, deterministic way. Software libraries that handle the low-level EtherCAT and CANopen communications can bridge the gap between the controller and the drive, simplifying the overall development of complex motion control applications. If the method of trajectory transmission is unreliable, undesired behavior may occur, such as choppy motion, damaged payloads, and error conditions. The DS402 Protocol for Motion Control has defined Interpolated Position Mode as a means of standardizing the control of multiple coordinated axes through the transmission of synchronization (SYNC) pulses and process data objects (PDO’s). High-resolution trajectories result in high data rates that must be handled by both the controller and drive. Some controllers use real-time operating systems to deal with the high data rates. Another approach utilizes data buffers in the firmware of both the controller and drive to provide forgiveness for controller latency. In either case, engineers designing robotic systems will find that low-level software to process the data is necessary to achieve reliable, high performance motion control. Processing libraries such as the Copley Motion Library (CML) provide easy implementation that integrates seamlessly with the MoveIt2 API and utilizes the DS402 Protocol to deliver smooth, synchronous motion over the CANopen or EtherCAT networks.