Synchronization of Distributed Controllers in Cyber-Physical Systems

Due to misaligned clock sources, distributed control in Cyber-Physical Systems (CPS) requires not only synchronous execution of control algorithms on distributed system components, which we refer to as cyber-synchronization, but also appropriate generation of actuation signals-we refer to this as physical-synchronization. In this paper, we define general requirements for cyber-physical synchronization, as well as show their use on a specific real-world application-distributed motion control for reconfigurable manufacturing systems. We present synchronization challenges in such systems and investigate effects of synchronization errors on the overall system functionality (i.e., machining accuracy). Furthermore, we introduce a low-cost synchronization scheme that can be implemented with of-the-shelf components and validate it on standardized accuracy tests with 2D configurations of industry-grade single-axis robots. We show that our cyber-physical synchronization techniques ensure minimal accuracy impairment of distributed motion control without introducing significant cost/overhead to system design.