Research On The Communication Technology Between Drive System And Encoder Based On Power Line Carrier

With the continuous improvement of the level of industrial automation,the servo system has become more and more widely used as the most important drive device in automated production.Encoders with high resolution and high communication speed are often used as position sensors for high performance servo systems to obtain accurate position and velocity information.High resolution and high speed encoders usually use full duplex synchronous serial communication mode.Two groups of signals are transmitted through clock and data,which requires high synchronization of signal phase and additional synchronous compensation function to achieve better transmission rate and transmission distance.With the progress of communication technology,encoder interface is developing in the direction of bus and network.Reducing the number of communication cables and the number of contact points is also a new trend of long distance and high reliable data transmission.Therefore,a kind of encoder interface communication system based on power line carrier technology is studied in this paper.First of all,the design of carrier communication in servo system is outlined.On the basis of this scheme,the design of carrier system based on RS485 link standard is proposed.Then the traditional carrier signal modulation method is analyzed,and the differential Manchester encoding is finally used.Then,the carrier timing requirements are analyzed in detail,and a power line carrier parallel communication method based on BiSS-C protocol is proposed.This method can shorten the communication delay by the maximum program under the premise of satisfying the synchronous transmission of sensor data and control information bits.Secondly,the hardware circuit of the whole system is designed,including the coupling circuit,the RS485 communication circuit and the power supply circuit.The characteristics of the DC channel of the coupled circuit and the parameters selection and design process of the coupling transformer are analyzed in detail.Then,based on FPGA,the controller-side slave,encoder-side host and differential Manchester codec are designed,and the rationality of each module design is verified by simulation and board-level test.Finally,an on-line debug platform based on servo system is built.The test and result analysis of the servo control system under carrier communication structure are completed.In order to further verify the reliability of the carrier communication system,the error rate test and anti-interference test are also carried out.In summary,this article takes FPGA as the core,designs the carrier hardware circuit,plans the communication flow,formulates the communication protocol,and realizes the digital carrier communication of the DC power line.The experiment of closed-loop control of servo motor shows that the system is stable and reliable and meets the requirements of communication.