High-precision time synchronization chip design for industrial sensor and actuator network

Mission-critical (MC) sensor and actuator networks (SANs) are being applied widely for multiaxis motion control of robotic manipulators, particularly for performing MC tasks in smart manufacturing. One of the most challenging tasks in MC-SANs is the development of a precision time synchronization (PTS) protocol. A conventional precision time system uses the IEEE 1588 v2 standard [1]; however, in MC-SANs, many factors need to be considered when designing an IoT computing system, such as robustness, cost-effectiveness, interoperability and scalability. This study proposes a high-precision time synchronization protocol based on Modbus sensors and actuator networks for an industrial fieldbus network. The PTS protocol design and hardware synthesis are conducted with a consistent and systematic design methodology. GRAFCET is used to model the individual functional modules and hierarchical behavior of the system. The behavior of each module is represented as a sequential–concurrent hybrid discrete event system. We apply high-level synthesis rules to design PTS hardware for a complex PTS system based on the VHSIC hardware description language (VHDL). The PTS hardware module has an embedded PTS algorithm with a proportional error correction model, and the time synchronization accuracy of the precision time protocol (PTP) chip is up to 42 ns. Experimental results demonstrate that our high-performance PTS controller chip can satisfy the requirements of multiaxis motion control and that it is more efficient than other protocols and products designed for similar industrial manufacturing applications.