EtherCAT slave controller for AC servo motor

Abstract

The EtherCAT network was developed by Beckhoff Automation and it is considered the fastest technology among industrial Ethernet networks. Thanks to high data transmission rates, flexible connectivity and nanosecond synchronization, EtherCAT networks are becoming more and more popular in industrial applications. AC Servo motors are becoming more and more popular in industrial applications due to their high efficiency, fast dynamic response, low noise and high precision. Servo motor control technology is constantly being developed, one of the trends is integrating real-time network into the motor controller to improve efficiency and reduce hardware costs. This paper presents the design of an AC Servo motor controller with integrated EtherCAT network. The system architecture of the EtherCAT Slave as well as the communication method between the application microcontroller and the EtherCAT Slave device are presented. Peripheral components, processing tasks of EtherCAT network-integrated motor controllers for industrial applications are analyzed in detail. Then, we propose the optimal EtherCAT controller hardware architecture both in terms of motor control and EtherCAT. The controller architecture is a combination of EtherCAT chip, high performance microcontroller and FPGA, optimized for motor control application. In addition, a prototype controller has been designed based on the proposed structure with compact size, integrated Sigma Delta ADC, USB interface, Digital I/O and support for a variety of position feedback sensors. Some important points of the CIA-402 Driver profile standard such as operating structure, state machine management, Cyclic synchronous position control mode are analyzed and applied to closed-loop control of AC servo motor. The controller is connected to the EtherCAT master and operates in a real-time environment. Test results and measurements have been checked to demonstrate the controller's operability in the EtherCAT network as well as AC Servo motor controller responsiveness.