Design And Implementation Of EtherCAT Fieldbus Interface Of Servo Drive Based On FPGA

Industrial automation puts forward the requirements of the high speed and high precision control for servo drive technology. The fieldbus technology provides a network transmission platform which is digital for servo drive control. Since EtherCAT has excellent performance, it is widely used in the servo drive interface. However, the current implementation of the interface exists high cost and inflexible problems. Therefore, the technology of the EtherCAT servo interface is studied. A new FPGA-based design method is proposed which owns the characteristics of high efficiency, low cost and flexible integration. The specific contents are as follows:The demands arisen from the servo drive control to the EtherCAT bus are analyzed, and the requirements of real-time stability, compatibility and synchronization in EtherCAT bus are discussed. Furthermore, according to the requirements of EtherCAT protocol, a FPGAbased design scheme consisting of hardware platform and software architecture for the servo drive EtherCAT interface is proposed.In the datalink layer of the EtherCAT interface, a kind of design method for the EtherCAT IP core is proposed based on time division multiplexing strategy. And then the realization procedures and simulation verifications of the modules in IP core are presented in details, which consist of the following parts: the data frame real-time processing and forwarding with real-time stability constraint, the application communication interface with compatibility constraint and distributed clock with synchronization constraint.In the application layer of the EtherCAT interface, the key techniques of servo drive EtherCAT interface are studied based on CANopen protocol. Meanwhile, the CoE application layer interface protocol is designed and realized according to its function, including EtherCAT communication state machine, CANopen-based EtherCAT application layer communication interface and CANopen-based power device state machine CiA402 protocol.An interoperability experimental platform is set up to verify the effectiveness and feasibility of the designed EtherCAT interface, which contains different types of master and slave devices. The validation tests of the EtherCAT interface are carried out from the perspective of master devices, and these tests are classified into functional ones and performance ones. The functional tests include the state machine test, the process data communication PDO test and the mailbox communication SDO test; the performance tests are made up of the compatibility test, the real-time stability test and the synchronization test. The experimental results show that the proposed scheme designed servo drive EtherCAT interface can not only achieve the desired functional targets, but also acquire excellent performance for servo control.