Design And Implementation Of Gyrowheel Communication System Based On Ethercat Bus

With the continuous development of space technology,the miniaturization of spacecraft has attracted the attention of many institutions and researchers at home and abroad.The gyrowheel is a new type of device that integrates attitude control and measurement functions.It can output three-axis attitude control torque and simultaneously sense the two-axis attitude angular velocity of the spacecraft.The existing gyrowheel prototype system adopts the combination control mode of the host computer and the slave computer,and they communicate through the Advantech series PCL board,which has high cost and complicated structure.In view of the above shortcomings,this paper designs and implements the gyrowheel communication system based on EtherCAT industrial Ethernet bus.Firstly,the EtherCAT protocol is introduced.The EtherCAT operating principle and data frame format are analyzed.EtherCAT messages can be matched with slaves by network addressing,logical addressing,device addressing exactly.Master-slave communication can be divided into non-periodic mailbox data communication and periodic process data communication according to time key.The master can communication with the slave after configuring the slave to the operating state.Secondly,the design of the EtherCAT master under Windows system is introduced,including the network card driver module,configuration module and data communication module.The NIC driver module is mainly implemented by calling the library function in WinPcap,it can configure the network card to send and receive data.The configuration module mainly configures the slave registers by constructing,transmitting and receiving data frames,and the slave is switched fr om the init state to the operational state;the data communication module periodically collects the gyrowheel data information and outputs the control amount through the timer.Then,the RTX system and the design and implementation of the EtherCAT master in the RTX system are introduced.The RTX system can extend the Windows operating system in real time,which solves the real-time problem of the Windows platform effectively.The EtherCAT communication under the RTX system also includes a network card driver module,a configuration module,and a data communication module.Among them,the network card driver module is achieved by modifying the network card open source driver provided by IntervalZero officially;the configuration module only needs to adopt the sending and receiving functions under the RTX system,the state transition process is not changed;the data communication module needs to use the timer under the RTX system.Finally,a system experiment platform was built and tested.The master and slave are connected by a switch,which is connected to another computer.Firstly,the system clock accuracy and stability under both systems are tested.Then,the functions of the network card driver module,configuration module and data communication module are tested.The EtherCAT data frames sent and received by the network card are monitored by Wireshark software,and the voltage value of the corresponding pin is measured by the oscilloscope,and the data received by the master are analyzed.Various experimental results indicate that the EtherCAT communication can be normally performed between the master and the slave.