The CAN-based synchronized structure for multi-axis motion control systems

Basically, the controller area network (CAN) is an event-triggered control network. However, design of precise and safety-critical applications requires time-triggered protocols as the communication infrastructure to achieve hard real-time performance. Although the time-triggered controller area network (TTCAN) is suitable for synchronized applications, complexity and inflexibility of implementing the TTCAN cause limited applications in motion control. This paper implements CAN communication services on precise synchronized multi-axis motion control by introducing the event/time-triggered structure. A motion command estimator is implemented to estimate the lost messages caused by the network transmission rate. The proposed CAN-based motion control system achieves desirable performance even under a lower transmission rate with heavier message loading on the bus. Furthermore, the proposed event/time-triggered structure has been successfully applied to a DYNA MYTE 1007 CNC machine and experimental results indicate that tracking accuracy in different CAN transmission rate has been obtained.