CN117499175A - Multi-motor synchronous control method based on TSN and EtherCAT heterogeneous network - Google Patents

Multi-motor synchronous control method based on TSN and EtherCAT heterogeneous network Download PDF

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Publication number
CN117499175A
CN117499175A CN202311430186.XA CN202311430186A CN117499175A CN 117499175 A CN117499175 A CN 117499175A CN 202311430186 A CN202311430186 A CN 202311430186A CN 117499175 A CN117499175 A CN 117499175A
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motor
clock
motor driver
servo motor
computer
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Inventor
陈晓乐
张宏超
梁晓明
孙云龙
李淑慧
江达
杜玲
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China North Vehicle Research Institute
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China North Vehicle Research Institute
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    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00Data switching networks
    • H04L12/28Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
    • H04L12/40Bus networks
    • H04L12/403Bus networks with centralised control, e.g. polling
    • H04L12/4035Bus networks with centralised control, e.g. polling in which slots of a TDMA packet structure are assigned based on a contention resolution carried out at a master unit
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04JMULTIPLEX COMMUNICATION
    • H04J3/00Time-division multiplex systems
    • H04J3/02Details
    • H04J3/06Synchronising arrangements
    • H04J3/0635Clock or time synchronisation in a network
    • H04J3/0638Clock or time synchronisation among nodes; Internode synchronisation
    • H04J3/0658Clock or time synchronisation among packet nodes
    • H04J3/0661Clock or time synchronisation among packet nodes using timestamps
    • H04J3/0667Bidirectional timestamps, e.g. NTP or PTP for compensation of clock drift and for compensation of propagation delays
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L69/00Network arrangements, protocols or services independent of the application payload and not provided for in the other groups of this subclass
    • H04L69/16Implementation or adaptation of Internet protocol [IP], of transmission control protocol [TCP] or of user datagram protocol [UDP]
    • H04L69/161Implementation details of TCP/IP or UDP/IP stack architecture; Specification of modified or new header fields
    • H04L69/162Implementation details of TCP/IP or UDP/IP stack architecture; Specification of modified or new header fields involving adaptations of sockets based mechanisms
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L69/00Network arrangements, protocols or services independent of the application payload and not provided for in the other groups of this subclass
    • H04L69/22Parsing or analysis of headers
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P90/00Enabling technologies with a potential contribution to greenhouse gas [GHG] emissions mitigation
    • Y02P90/02Total factory control, e.g. smart factories, flexible manufacturing systems [FMS] or integrated manufacturing systems [IMS]

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Computer Security & Cryptography (AREA)
  • Control Of Multiple Motors (AREA)

Abstract

The invention relates to a multi-motor synchronous control method based on TSN and EtherCAT heterogeneous network, belonging to the motor control field, comprising the steps of establishing communication between a computer PC, a TSN exchanger and a motor controller, setting clock synchronization period and time difference threshold value for clock synchronization initialization; in the clock synchronization period, the computer PC sends a control instruction data packet to each motor controller through the TSN switch, each motor controller analyzes the control instruction data packet into a pulse signal, the pulse signal is sent to a first motor driver in the sub EtherCAT network, and the rest motor drivers in the sub network are cascaded to receive the pulse signal; each motor driver returns the motion state of the corresponding servo motor; triggering clock synchronization initialization after fault repair is carried out when the PC monitors that the motion state of the servo motor is inconsistent with the control command; or triggering clock synchronization initialization when the computer PC monitors that the total execution delay of the control instructions is larger than the time difference threshold value; the end of the clock synchronization period triggers the clock synchronization initialization again. The real-time synchronous communication of multiple motors is solved.

Description

Multi-motor synchronous control method based on TSN and EtherCAT heterogeneous network
Technical Field
The invention relates to the technical field of industrial automation control, in particular to a multi-motor synchronous control method based on TSN (Time-Sensitive Networking, clock sensitive network) and EtherCAT (Ethernet for Control Automation Technology, ethernet control automation technology) heterogeneous network.
Background
In modern industrial automation and control systems, multi-motor synchronous control is an important task, which aims to ensure that multiple motors run at consistent speeds, positions or movement patterns, thereby improving the performance and accuracy of the overall system. Synchronous control is not separated from an efficient and reliable real-time communication technology. Real-time data exchange and control command transmission are required between the sensor and the actuator to ensure the synchronism among multiple motors. Conventional communication methods cannot meet the requirements of real-time and synchronicity, and thus more advanced communication technologies are required to meet these requirements. In recent years, ethernet technology has been widely used in the field of industrial automation. With the development of Ethernet technology and real-time communication protocols such as EtherCAT, the development of the technology greatly improves the data transmission speed and the accurate synchronization capability between multiple motor systems, and provides effective technical support for realizing real-time synchronization control.
Due to the complexity and interaction of multiple motor systems, real-time synchronous control is required to address the following major issues:
(1) Communication delay: the communication delay refers to a delay time from the transmission of the control instruction to the execution of the actual action. In a multi-motor system, control instructions for each motor need to be transmitted to the corresponding slave station apparatus via a communication network, and executed by a driver. Communication delay can cause time difference of a control command reaching the motor, and the synchronous performance of the motor is affected;
(2) Data synchronization: in a multiple motor system, the data (e.g., position, speed, etc.) of the individual motors need to be consistent during real-time synchronous control. The data synchronization problems include clock synchronization, data transfer synchronization, and control calculation synchronization. If the synchronism is not good, the problems of uncoordinated motor movement, error accumulation and the like are caused.
While ethernet and real-time communication protocols provide a good technological base, multi-motor real-time synchronous control still faces challenges. The aim of the real-time synchronous control of the multiple motors is to realize the cooperative work among the multiple motors and improve the performance of the whole system. The strategy of complex multi-distributed control and cooperative control is affected by factors such as model uncertainty and parameter sensitivity, which affect the synchronization accuracy and system reliability. Further, the synchronous control of the two motors is performed to the synchronous control of the multiple motors. Even up to the control of larger scale motor clusters and large space span collaborative systems, appropriate control structures and real-time communication means are required to achieve effective control. Although ethernet technology and real-time communication protocols provide support in implementing real-time synchronous control, no effective method for addressing the need for multi-motor synchronous control real-time communication has been proposed.
Disclosure of Invention
In view of the above analysis, the embodiment of the invention aims to provide a multi-motor synchronous control method based on a TSN and EtherCAT heterogeneous network, which is used for solving the technical problem that multiple motors need real-time synchronous communication in the prior art.
In order to solve the technical problems, the invention provides a multi-motor synchronous control method based on TSN and EtherCAT heterogeneous network, comprising the following steps:
establishing communication among a computer PC, a TSN switch and a plurality of motor controllers, setting a clock synchronization period and a time difference threshold value, and carrying out clock synchronization initialization;
in a clock synchronization period, the computer PC sends a control instruction data packet to each motor controller through the TSN switch, each motor controller analyzes the control instruction data packet into a pulse signal, the pulse signal is sent to a first motor driver in the sub-network through a corresponding sub-EtherCAT network, and the rest motor drivers in the sub-network are connected in cascade to receive the pulse signal; each motor driver returns the motion state of the corresponding servo motor to the computer PC; when the PC monitors that the motion state of the servo motor is not consistent with the control instruction, triggering clock synchronization initialization after the servo motor fault is repaired; or triggering clock synchronization initialization when the computer PC monitors that the total execution delay of the control instructions is larger than the time difference threshold;
And triggering the clock synchronization initialization again when the clock synchronization period is finished.
Further, the establishing communication between the computer PC, the TSN switch, and the plurality of motor controllers includes:
setting the PC, the motor controller and the TSN switch to be in the same network segment of the same TSN domain;
the computer PC is used as a server, and a server socket is created;
setting the connection of the server to be in a multithreading mode, and carrying out polling monitoring;
each motor controller is used as a client to be connected to the server through a TSN switch respectively;
and the server side polls to acquire the connection of a new client side, and creates a sub-thread for communicating with the client side.
Further, the clock synchronization initialization includes:
in the TSN domain, using a gPTP synchronization mode, aligning the hardware time stamps of the computer PC and each motor controller;
in each sub EtherCAT network, a distributed clock synchronization mechanism is adopted, each motor controller is used as a master station reference clock of each sub EtherCAT network, and the link propagation delay and the initial clock offset from the master station reference clock to a first motor driver in each corresponding slave station are calculated;
The first motor driver calculates a local clock error according to a reference clock of a master station, link propagation delay and an initial clock offset, and adjusts the local system time of the first motor driver to be a calibration clock of the first motor driver based on the local clock error;
sequentially adding a micro clock drift to the cascaded motor drivers on the basis of the calibration clock of the previous motor driver to obtain the calibration clock of each cascaded motor driver; the micro-clock drift is obtained by the fact that the computer PC sends a synchronization instruction in advance and the link transmission delay between the second motor driver and the first motor driver in each sub EtherCAT network is calculated.
Further, the first motor driver calculating a local clock error according to the master station reference clock, the link propagation delay and the initial clock offset, and adjusting the first motor driver local system time to the calibration clock of the first motor driver based on the local clock error comprises:
calculating link propagation delay and initial clock offset from a reference clock to a corresponding first motor driver by taking each motor controller hardware time stamp as a master station reference clock;
The first motor driver calculates a local clock error according to the master station reference clock, the link propagation delay and the initial clock offset;
the initial clock offset is the time difference between the reference clock of the master station of the motor controller and the local clock of the first motor driver when the clock synchronization initialization process starts; the link propagation delay is a transmission delay between the motor controller to the first motor drive;
the local clock error of the first motor drive is calculated as follows:
E 1 =C i -T i -T refi
wherein E is 1 For the local clock error of the first motor driver corresponding to motor controller i, C i For the local clock, T, of the first motor drive corresponding to motor controller i i For the link propagation delay of the first motor driver corresponding to the motor controller i, T refi A reference clock for the motor controller i;
the first motor driver obtains a calibration clock based on the local system time and the local clock error adjustment.
Further, the control instruction data packet includes a transmission time stamp;
the motor controller in each sub EtherCAT network receives the control instruction data packet, analyzes the control instruction data packet into a pulse signal and sends the pulse signal to the first motor driver in the sub EtherCAT network;
The first motor driver extracts the corresponding instruction according to addressing and transmits the rest instructions to the next motor driver through the EtherCAT bus, and the rest motor drivers are sequentially connected in cascade to receive pulse signals.
Each motor driver receives the pulse signals to drive the corresponding servo motor to move, and simultaneously records and uploads the received pulse signal time stamp to the computer PC;
and obtaining the total execution delay of the control instruction based on the received pulse signal time stamp and the sending time stamp.
Further, when the computer PC monitors that the motion state of the servo motor does not accord with the control command, performing the fault repair of the servo motor includes:
each motor driver sequentially returns the recorded corresponding servo motor motion state data to the last motor driver in cascade until reaching the first motor driver, and the data are transmitted back to the computer PC through the motor controller and the TSN switch;
the PC judges whether the motion state of the servo motor meets the control instruction requirement or not;
and if the fault is not met, performing fault repair on the servo motor.
Further, if the failure meets the failure condition, performing fault repair on the servo motor comprises the following steps:
The first step, the computer PC judges the sub EtherCAT network where the failed servo motor is based on the servo motor running state data, and then judges the corresponding motor driver and motor controller;
secondly, judging the fault severity degree of the failed servo motor based on the running state data;
and thirdly, stopping the system, stopping/disabling the failed servo motor or performing online replacement of the servo motor based on the severity of the fault.
Further, based on the severity of the fault, stopping the system, stopping or disabling the failed servo motor, or performing an online replacement of the servo motor includes:
if the severity of the fault is a safety risk, immediately stopping the machine to repair the fault;
if the position and the speed of the servo motor are the position and the speed of the servo motor, the electric fault, the mechanical fault and the bearing fault, the servo motor cannot accurately sense the position and the speed, and the computer PC sends a command for stopping/disabling the servo motor, so that the fault servo motor is stopped/disabled;
if the temperature is abnormal or the communication data packet is lost, the servo motor is replaced online.
Further, the motor controller, the motor driver and the servo motor are positioned in an EtherCAT network and are connected through an EtherCAT interface and a bus;
Each sub EtherCAT network consists of a motor controller, a plurality of motor drivers and corresponding servo motors, wherein the motor controller is a master station, and the motor drivers are slave stations.
Further, the servo motor operation state data includes: current position, speed, acceleration, power, temperature, current, voltage, fault code, alarm information, operation log, event record information of the servo motor.
Compared with the prior art, the invention has at least one of the following beneficial effects:
1. high-performance real-time synchronous control: one TSN network may be connected to multiple sub EtherCAT networks to enable high performance, high real-time and high synchronization communications in various industrial automation applications. The TSN network provides a high precision clock synchronization and traffic scheduling mechanism that ensures real-time communications throughout the network. By combining with the real-time Ethernet protocol of EtherCAT, high-performance data transmission and control calculation can be realized, and the real-time performance of a multi-motor system is improved;
2. synchronization is improved: the clock synchronization mechanism in the TSN network can ensure that clocks of all nodes are kept synchronous, and time error accumulation between servo motors is avoided. By combining a synchronization mechanism in EtherCAT, high-precision synchronous control among a plurality of servo motors can be realized, and cooperative work and motion precision of the motors are ensured;
3. Advantages of heterogeneous networks: the TSN and EtherCAT are fused together by two different communication technologies, and their advantages are fully utilized. TSN provides time synchronization and predictable latency, while EtherCAT provides real-time data transmission and synchronization control capabilities. The heterogeneous network combines the advantages of the two, so that higher-performance control is realized in a complex multi-motor synchronous control system;
4. network reliability enhancement: the TSN network improves the reliability of data transmission through a fault recovery mechanism and ensures the stable operation of a multi-motor system;
5. flexibility and scalability: through the combination of TSN and EtherCAT, a heterogeneous network architecture can be realized, and a multi-motor system can be flexibly laid out and expanded. The TSN network supports distributed node and segment configuration, can synchronously control a larger-scale servo motor cluster, and can meet the requirements of multi-motor control systems with different scales and complexity.
In the invention, the technical schemes can be mutually combined to realize more preferable combination schemes. Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and drawings.
Drawings
The drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the invention, like reference numerals being used to refer to like parts throughout the several views.
FIG. 1 is a flow chart of a multi-motor synchronous control method based on TSN and EtherCAT heterogeneous network;
fig. 2 is a topological structure block diagram of a multi-motor real-time synchronous control system based on TSN and EtherCAT heterogeneous network.
Detailed Description
Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form a part hereof, and together with the description serve to explain the principles of the invention, and are not intended to limit the scope of the invention.
In the scheme, through a real-time clock synchronization and data transmission mechanism of the TSN network, each node is ensured to perform data transmission and control operation at the same time point. And the EtherCAT network is used for carrying out real-time data transmission and control calculation, so that high-precision synchronous control among all servo motors is ensured.
The TSN is a technology for realizing real-time communication and synchronization on the Ethernet, so that the Ethernet network can provide predictable delay and high-precision synchronization, and the TSN can be applied to the fields of industrial automation, automobiles and aerospace so as to support the application with higher real-time requirements. EtherCAT is a high-performance, real-time Ethernet communication protocol used in the field of industrial automation. Based on the physical layer of the Ethernet, low-delay and high-precision real-time communication is realized.
EtherCAT, as a real-time Ethernet protocol, can transmit data in millisecond or sub-millisecond time, providing high-performance data transmission and synchronous control functions. EtherCAT supports a distributed control architecture, wherein a plurality of devices can be physically connected through Ethernet wires, so that the complexity of network wiring is reduced, and the expandability is improved. One TSN network is connected to a plurality of EtherCAT networks.
The heterogeneous network of the TSN and the EtherCAT combines two different communication technologies of the TSN and the EtherCAT together to form a comprehensive network architecture, and the heterogeneous network aims at fusing the time synchronization of the TSN and the real-time data transmission and synchronization control capability of the EtherCAT network. By this combination, higher performance, more reliable real-time communication and synchronous control can be achieved in complex control systems, especially in multi-motor synchronous control applications. The heterogeneous networks of TSN and EtherCAT combine two different but complementary communication technologies to meet the requirements of synchronous control of multiple motors for real-time and reliability.
In a specific embodiment of the present invention, a multi-motor synchronous control method based on a TSN and EtherCAT heterogeneous network, where a computer PC communicates with a motor controller in real time through a TSN switch in the TSN network, to implement real-time synchronization, remote control and motion adjustment of a multi-motor system, as shown in fig. 1, includes:
Establishing communication among a computer PC, a TSN switch and a plurality of motor controllers, setting a clock synchronization period and a time difference threshold value, and carrying out clock synchronization initialization;
in a clock synchronization period, the computer PC sends a control instruction data packet to each motor controller through the TSN switch, each motor controller analyzes the control instruction data packet into a pulse signal, the pulse signal is sent to a first motor driver in the sub-network through a corresponding sub-EtherCAT network, and the rest motor drivers in the sub-network are connected in cascade to receive the pulse signal; each motor driver returns the motion state of the corresponding servo motor to the computer PC; when the PC monitors that the motion state of the servo motor is not consistent with the control instruction, triggering clock synchronization initialization after the servo motor fault is repaired; or triggering clock synchronization initialization when the computer PC monitors that the total execution delay of the control instructions is larger than the time difference threshold;
and triggering the clock synchronization initialization again when the clock synchronization period is finished.
Further, the establishing communication between the computer PC, the TSN switch, and the plurality of motor controllers includes:
Setting the PC, the motor controller and the TSN switch to be in the same network segment of the same TSN domain;
the computer PC is used as a server, and a server socket is created;
setting the connection of the server to be in a multithreading mode, and carrying out polling monitoring;
each motor controller is used as a client to be connected to the server through a TSN switch respectively;
and the server side polls to acquire the connection of a new client side, and creates a sub-thread for communicating with the client side.
Setting the PC, the motor controller and the TSN switch to be in the same network segment of the same TSN domain; the three are connected by Ethernet. Ensuring that the computer PC, motor controller and TSN switch are all within the same TSN domain and within the same network segment ensures that they can communicate with each other.
The server socket is used for intercepting a connection request of the motor controller; this is the starting point of the communication and the computer PC will wait for the connection of the motor controller.
The connection of the PC end of the computer is set to be in a multithreading mode, and the PC can monitor connection requests of a plurality of motor controllers at the same time. This method of concurrent processing ensures that the computer PC can communicate with multiple motor controllers simultaneously.
The motor controller is used as a client and is respectively connected with a computer PC end; the motor controller sends a connection request to the computer PC to establish a communication connection.
One computer PC may be connected to one to a plurality of clients. The computer PC handles multiple connections simultaneously, with each sub-thread being responsible for communication with the motor controller in each sub-EtherCAT network.
The sub EtherCAT network comprises 1 motor controller, a plurality of motor drivers and corresponding servo motors, wherein the motor controller, the motor drivers and the servo motors support EtherCAT interfaces, and the motor controllers, the motor drivers and the servo motors are connected through EtherCAT buses. The motor controller is a master station of the sub EtherCAT network, and the motor driver is a slave station of the sub EtherCAT network.
Further, the clock synchronization initialization includes:
in the TSN domain, aligning the computer PC with the hardware time stamps of the motor controllers using gPTP (general Precise Time Protocol, generalized accurate time synchronization protocol) synchronization;
in each sub EtherCAT network, a distributed clock synchronization mechanism is adopted, each motor controller is used as a master station reference clock of each sub EtherCAT network, and the link propagation delay and the initial clock offset from the master station reference clock to the first motor driver of each corresponding slave station are calculated;
The first motor driver calculates a local clock error according to a reference clock of a master station, link propagation delay and an initial clock offset, and adjusts the local system time of the first motor driver to be a calibration clock of the first motor driver based on the local clock error;
sequentially adding a micro clock drift to the cascaded motor drivers on the basis of the calibration clock of the previous motor driver to obtain the calibration clock of each cascaded motor driver; the micro clock drift is obtained by the link transmission delay between a second motor driver and a first motor driver in each sub EtherCAT network through calculation, wherein the micro clock drift is obtained by the fact that the computer PC sends a motor driver clock synchronization instruction in advance;
and sequentially adding a micro clock drift to the cascaded motor drivers to obtain the calibration clock of each cascaded motor driver.
In the TSN domain, using a gPTP synchronization mode, aligning the hardware time stamps of the computer PC and each motor controller;
the gPTP protocol provides accurate clock synchronization, among other things, to ensure that all devices are operating on the same time reference. With the gPTP protocol, the computer PC is aligned with the hardware timestamps of the multiple motor controllers. This means that their time references become consistent to ensure that they all operate under the same time standard. Multiple motor systems require a high degree of time synchronization to ensure coordinated motion.
In each sub EtherCAT network, a synchronization mechanism employing a distributed clock (DC, distributive Computing, distributed computing) is used.
In this step, the function of establishing the clock synchronization period is to ensure that the various devices (including the computer PC, the motor controller, and the motor driver) in the multi-motor synchronization system remain highly accurate in time synchronization. Periodic timing clock synchronization is performed within a certain time to maintain the synchronism between the local clock and the reference clock of the device, thereby realizing time synchronization and correcting clock drift.
The clock synchronization period is set according to specific actual requirements. The synchronous control of multiple motors is closely related to the clock synchronization precision. In a specific implementation, due to reasons such as hardware equipment, a slave clock cannot well follow a master clock, and as time goes by, due to factors such as clock drift, the synchronization error value of the slave clock relative to the master clock increases. Thus, the clock synchronization period is set, and clock synchronization is periodically resumed. When the TSN time delay is large, firstly, clock synchronization is carried out in a TSN domain, and a computer PC is aligned with hardware time stamps of all motor controllers; and then, in each EtherCAT network, using each motor controller as a reference clock, recalculating the link propagation delay and the initial clock offset from the reference clock to each driver, and performing DC synchronization, so that the synchronous execution of tasks of each servo motor is controlled by using the same system time between TSN and all the devices of the EtherCAT heterogeneous network.
The time difference threshold, which is a set point used in determining whether to clock synchronize, is typically used for the computer PC to control the maximum allowable difference between the command packet transmit time stamp and the motor driver receive pulse signal time stamp, and helps determine when to trigger the clock synchronizing operation to ensure that the time of each device remains within a consistent range. By way of example, the time difference threshold may be set to 10 microseconds.
The particular value of the time difference threshold is set will vary depending on the needs of the particular application. The time difference threshold is typically in microseconds (μs) or nanoseconds (ns), the following being exemplary time difference thresholds:
(1) For applications requiring higher precision synchronization, the time difference threshold is set very small, e.g., 1 microsecond (μs) or less;
(2) In some real-time control systems, a slightly larger time difference can be tolerated, typically set between a few microseconds or tens of microseconds;
(3) For general applications, the time difference threshold is further relaxed, allowing for greater values, which may be set for hundreds of microseconds or more;
(4) In certain industrial automation applications, time differences of the order of milliseconds may even be acceptable, which is often not suitable for multi-motor control systems requiring a high degree of synchronization.
The selection of the time difference threshold value balances the system performance requirements and acceptable complexity, and a smaller time difference threshold value requires more stringent clock synchronization and higher mildness, requires higher performance hardware and complex software to implement, and the specific time difference threshold value is weighted according to the application scenario, performance requirements and available technology.
Further, the first motor driver calculating a local clock error according to the master station reference clock, the link propagation delay and the initial clock offset, and adjusting the first motor driver local system time to the calibration clock of the first motor driver based on the local clock error comprises:
calculating link propagation delay and initial clock offset from a reference clock to a corresponding first motor driver by taking each motor controller hardware time stamp as a master station reference clock;
the first motor driver calculates a local clock error according to the master station reference clock, the link propagation delay and the initial clock offset;
the initial clock offset is the time difference between the reference clock of the master station of the motor controller and the local clock of the first motor driver when the clock synchronization initialization process starts; the link propagation delay is a transmission delay between the motor controller to the first motor drive;
The local clock error of the first motor drive is calculated as follows:
E 1 =C i -T i -T refi
wherein E is 1 For motor controller i pairsLocal clock error of corresponding first motor driver, C i For the local clock, T, of the first motor drive corresponding to motor controller i i For the link propagation delay of the first motor driver corresponding to the motor controller i, T refi A reference clock for the motor controller i;
the first motor driver obtains a calibration clock based on the local system time and the local clock error adjustment.
Further, the control instruction data packet includes a transmission time stamp;
each motor controller in each sub EtherCAT network receives the control instruction data packet, analyzes the control instruction data packet into a pulse signal and sends the pulse signal to the first motor driver in the sub EtherCAT network;
the first motor driver extracts the corresponding instruction according to addressing and transmits the rest instructions to the next motor driver through the EtherCAT bus, and the rest motor drivers are sequentially connected in cascade to receive pulse signals.
Each motor driver receives the pulse signals to drive the corresponding servo motor to move, and simultaneously records and uploads the received pulse signal time stamp to the computer PC;
And obtaining the total execution delay of the control instruction based on the received pulse signal time stamp and the sending time stamp.
The data instruction transmission between the PC and the motor controller is realized based on Modbus TCP protocol.
The computer PC sends a synchronous control instruction data packet to the motor controller through the TSN switch, wherein the control instruction data packet comprises: setting target position, speed, acceleration, current parameters of the servo motor, or performing specific control operations.
After receiving the control instruction data packet of the computer PC, the motor controller analyzes and processes the control instruction data packet, and sends control instructions to each motor driver in real time through the EtherCAT bus, so that high-precision synchronous control among all motors is ensured;
each motor controller controls the corresponding servo motor to operate; each motor controller records corresponding servo motor operation state data.
The servo motor operation state data includes: the current position, speed, acceleration, power, temperature, current, fault code, alarm information, running log and event record information of the servo motor.
As shown in fig. 2, the motor controller 1 transmits a pulse signal to the motor driver 1, the motor controller 2 cascades the motor controller 1 to receive the pulse signal, the motor controller 2 transmits a pulse signal to the motor driver 3, and the motor controller 4 cascades the motor controller 3 to receive the pulse signal.
Further, when the computer PC monitors that the motion state of the servo motor does not accord with the control command, performing the fault repair of the servo motor includes:
each motor driver sequentially returns the recorded corresponding servo motor motion state data to the last motor driver in cascade until reaching the first motor driver, and the data are transmitted back to the computer PC through the motor controller and the TSN switch;
the PC judges whether the motion state of the servo motor meets the control instruction requirement or not;
and if the fault is not met, performing fault repair on the servo motor.
Further, if the failure meets the failure condition, performing fault repair on the servo motor comprises the following steps:
the first step, the computer PC judges the sub EtherCAT network where the failed servo motor is based on the servo motor running state data, and then judges the corresponding motor driver and motor controller;
secondly, judging the fault severity degree of the failed servo motor based on the running state data;
and thirdly, stopping the system, stopping/disabling the failed servo motor or performing online replacement of the servo motor based on the severity of the fault.
Further, based on the severity of the fault, stopping the system, stopping or disabling the failed servo motor, or performing an online replacement of the servo motor includes:
if the severity of the fault is a safety risk, immediately stopping the machine to repair the fault;
if the position and the speed of the servo motor are the position and the speed of the servo motor, the electric fault, the mechanical fault and the bearing fault, the servo motor cannot accurately sense the position and the speed, and the computer PC sends a command for stopping/disabling the servo motor, so that the fault servo motor is stopped/disabled;
if the temperature is abnormal or the communication data packet is lost, the servo motor is replaced online.
Further, the motor controller, the motor driver and the servo motor are positioned in an EtherCAT network and are connected through an EtherCAT interface and a bus;
each sub EtherCAT network consists of a motor controller, a plurality of motor drivers and corresponding servo motors, wherein the motor controller is a master station, and the motor drivers are slave stations.
Further, the servo motor operation state data includes: current position, speed, acceleration, power, temperature, current, voltage, fault code, alarm information, operation log, event record information of the servo motor.
As shown in fig. 2, the hardware device involved in the method includes:
(1) Computer PC (Talker), speaker): the computer PC (Talker, sender) is a device for sending instructions, and is responsible for sending control instruction data packets to each motor controller through the TSN switch, and has a TSN time synchronization function;
optionally, according to the scale of the multi-motor synchronous control system in actual demand, a computer PC (Personal Computer ) can also be selected as a computer Server; the computer Server is selected when the system scale is large and the high-performance computer is needed, otherwise, the computer PC is selected.
(2) TSN switch: the TSN switch is a key device which is specially used for supporting real-time and high-reliability communication requirements, guaranteeing predictable and controllable transmission delay of instructions and data in a network, and achieving real-time communication and synchronous control in a TSN domain.
Wherein the TSN domain is a logical network area divided in the TSN network, wherein the devices and TSN switches both follow the same time synchronization and communication rules, the purpose of the TSN domain is to create a controllable, predictable communication environment to support real-time communication and synchronization control applications. Within a TSN domain, all devices follow the same time reference, controlled and scheduled by the TSN switch.
The TSN switch plays a key role in the multi-motor synchronous control system, is a bridge for two-way communication between a computer PC and a plurality of motor controllers in the sub EtherCAT network, and helps to realize high-performance real-time synchronous control among multiple motors by providing high-precision clock synchronization, flow scheduling and predictive data transmission, so that the performance and reliability of the whole system are improved.
The computer PC and the TSN switch are positioned in the same network segment of the same local area network, and the same local area network is a TSN domain local area network.
(3) A motor controller: the computer PC sends control command packets to a plurality of motor controllers (listeners) in the sub EtherCAT network via the TSN switch. The computer PC is connected with the TSN switch and a plurality of motor controllers in the sub EtherCAT network through the Ethernet.
The motor controller can be one or more, and according to actual needs, the motor controller is used as a device for receiving the control instruction data packet. Each motor controller is a master station of the sub EtherCAT network where the motor controller is located, has a TSN time synchronization function, supports EtherCAT interfaces, receives a control instruction data packet sent by the Talker, receives the control instruction data packet, analyzes and processes the control instruction data packet into a pulse signal, and sends the pulse signal to a first motor driver in the sub EtherCAT network where the motor controller is located in real time.
The computer PC and the motor controller are in a one-to-many relationship. The division and collaboration of the Talker and Listener roles is an important link in implementing a multi-motor synchronous control system.
(4) A motor driver: the motor driver is used as a slave station of the sub EtherCAT network, the first motor driver is connected to the master station through the EtherCAT interface and the bus, the second motor driver is cascaded to the first motor driver, and the rest is analogized, and each motor driver supports EtherCAT interface to communicate through the EtherCAT bus.
A sub EtherCAT network includes a master station (motor controller) and a plurality of slave stations (motor drivers). In a sub EtherCAT network, the motor controller and the plurality of motor drives are typically physically connected by way of a cascade connection. This connection is commonly referred to as a "tandem connection" or "series connection". The basic steps are as follows:
first, the motor controller and the first motor driver in the sub EtherCAT network are physically connected:
next, starting from the first motor driver, its output is connected to the input of the next motor driver with EtherCAT cable. Thus, the instructions in the motor controller go along the EtherCAT cable to the next motor driver, and so on;
Repeating the cascade: this process can continue until all motor drives are connected to the same EtherCAT bus. Each motor drive is connected to a previous motor drive, thereby forming a cascade chain. The motor controller sends control pulse signals to all motor drivers through the cascade chain.
The cascade or series connection mode is beneficial to simplifying wiring, reducing the number of hardware devices and ensuring high performance and real-time performance. Such wiring is generally suitable for applications requiring synchronous control of multiple motors, such as industrial automation, robotics, and automated production lines. This topology ensures that control instructions and data can be efficiently transferred and synchronized.
The motor controller receives a control instruction data packet from a computer PC, analyzes and converts the control instruction data packet into a pulse signal, transmits the pulse signal to a first motor driver in the sub EtherCAT network, and receives the pulse signal in a cascade connection manner by the remaining motor drivers, wherein each motor driver drives a corresponding servo motor to rotate or move;
firstly, based on a control instruction data packet sent by a computer PC, a motor controller in a sub EtherCAT network generates pulse signals (such as a motion command, speed setting, position setting and the like) to a first motor driver;
Step two, after the first motor driver receives the pulse signal, executing the operation of the related servo motor, namely controlling the corresponding first servo motor;
a third step, simultaneously, the first motor driver continuously transmits the pulse signal to a second motor driver of the next cascade connection;
and step four, after the second motor driver receives the pulse signal from the first motor driver, executing corresponding servo motor operation, namely controlling the second servo motor.
This cascading process may continue by sequentially delivering pulse signals to each of the cascading motor drives to synchronously control the plurality of servo motors.
This cascading method allows coordinated multi-servo motor motion control, wherein the motions between the different servo motors are synchronized with each other. Typically, each motor drive has a unique address or identification in the cascade chain to ensure that the command is properly delivered to the particular servo motor.
In summary, the cascaded motor drives cooperate by transmitting commands in the cascade chain to ensure that the plurality of servomotors move synchronously in the desired manner. This is important for applications where multiple servomotors need to be coordinated to perform complex tasks simultaneously.
The motor driver receives pulse signals of the motor controller and is used for controlling the motion and behavior of the servo motor, and the position and speed of the servo motor can be controlled.
(5) And (3) a servo motor: as a device for executing instructions, a plurality of servo motors are necessary for real-time synchronous control when the plurality of servo motors execute corresponding actions at the same point in time.
As shown in fig. 2, schematically, two motor controllers are connected to the TSN switch, one motor controller being connected to two drivers. In this scheme, the motor controller can be a plurality of, and the quantity of motor controller does not have fixed maximum restriction, depends on specific application demand and system design, needs to consider following factors comprehensively, determines the quantity of specific motor controller:
(1) System scale: the system size is one of the main factors that determine how many motor controllers are needed. Large-scale industrial automation systems require multiple motor controllers to correspond to different motor drives and servomotors, while small-scale applications require only a few motor controllers;
(2) Number of motors: the number of servo motors is also a main factor in considering how many motor controllers are needed;
(3) System complexity: the complexity of the system also affects the number of motor controllers, and if the system needs a highly complex control strategy and a plurality of servo motors cooperate, more motor controllers are needed to realize the control;
(4) Performance requirements: if the system has higher requirements on real-time performance, precision and synchronism, more motor controllers are needed to ensure the control performance of each servo motor;
(5) Reserved capacity: in system design, it is considered to reserve some additional capacity for future expansion of the system.
In summary, the present solution has no hard limit on the number of motor controllers, which depends on the system requirements and design strategy, and in the system design stage, the scale, complexity, performance requirements and possible future extensions of the system are comprehensively considered, so as to determine an appropriate number of motor controllers.
Meanwhile, one motor controller in one sub EtherCAT network can correspond to a plurality of motor drivers, and the motor drivers and the servo motors are in a 1:1 relation. One motor controller corresponds to several motor drivers, i.e. several servo motors, and the following factors need to be considered:
(1) Motor controller performance: the performance of the motor controller will directly affect the number of drives and servo motors it can control;
(2) Communication bandwidth: the communication between the motor controller and the driver needs to occupy a certain bandwidth, and the larger communication bandwidth can support more drivers and servo motors;
(3) Control strategy: if the system application requires highly coordinated multi-motor motion control, more motor controller resources are required;
(4) Real-time and synchronicity: if the system application has high requirements on real-time performance and applicability, the motor controller needs more resources to ensure the synchronization among a plurality of servo motors.
Although one motor controller can control a plurality of motor drivers and servo motors, when determining specific quantity, performance evaluation and test verification at the system level need to be performed in advance, so that each servo motor can obtain enough control resources.
The multi-motor synchronous control method based on TSN and EtherCAT heterogeneous network has the following beneficial effects:
1. high-performance real-time synchronous control: one TSN network may be connected to multiple sub EtherCAT networks to enable high performance, high real-time and high synchronization communications in various industrial automation applications. The TSN network provides a high precision clock synchronization and traffic scheduling mechanism that ensures real-time communications throughout the network. By combining with the real-time Ethernet protocol of EtherCAT, high-performance data transmission and control calculation can be realized, and the real-time performance of a multi-motor system is improved;
2. Synchronization is improved: the clock synchronization mechanism in the TSN network can ensure that clocks of all nodes are kept synchronous, and time error accumulation between servo motors is avoided. By combining a synchronization mechanism in EtherCAT, high-precision synchronous control among a plurality of servo motors can be realized, and cooperative work and motion precision of the motors are ensured;
3. advantages of heterogeneous networks: the TSN and EtherCAT are fused together by two different communication technologies, and their advantages are fully utilized. TSN provides time synchronization and predictable latency, while EtherCAT provides real-time data transmission and synchronization control capabilities. The heterogeneous network combines the advantages of the two, so that higher-performance control is realized in a complex multi-motor synchronous control system;
4. network reliability enhancement: the TSN network improves the reliability of data transmission through a fault recovery mechanism and ensures the stable operation of a multi-motor system;
5. flexibility and scalability: through the combination of TSN and EtherCAT, a heterogeneous network architecture can be realized, and a multi-motor system can be flexibly laid out and expanded. The TSN network supports distributed node and segment configuration, can synchronously control a larger-scale servo motor cluster, and can meet the requirements of multi-motor control systems with different scales and complexity.
Those skilled in the art will appreciate that all or part of the flow of the methods of the embodiments described above may be accomplished by way of a computer program to instruct associated hardware, where the program may be stored on a computer readable storage medium. Wherein the computer readable storage medium is a magnetic disk, an optical disk, a read-only memory or a random access memory, etc.
The present invention is not limited to the above-mentioned embodiments, and any changes or substitutions that can be easily understood by those skilled in the art within the technical scope of the present invention are intended to be included in the scope of the present invention.

Claims (10)

1. A multi-motor synchronous control method based on TSN and EtherCAT heterogeneous network is characterized by comprising the following steps:
establishing communication among a computer PC, a TSN switch and a plurality of motor controllers, setting a clock synchronization period and a time difference threshold value, and carrying out clock synchronization initialization;
in a clock synchronization period, the computer PC sends a control instruction data packet to each motor controller through the TSN switch, each motor controller analyzes the control instruction data packet into a pulse signal, the pulse signal is sent to a first motor driver in the sub-network through a corresponding sub-EtherCAT network, and the rest motor drivers in the sub-network are connected in cascade to receive the pulse signal; each motor driver returns the motion state of the corresponding servo motor to the computer PC; when the PC monitors that the motion state of the servo motor is not consistent with the control instruction, triggering clock synchronization initialization after the servo motor fault is repaired; or triggering clock synchronization initialization when the computer PC monitors that the total execution delay of the control instructions is larger than the time difference threshold;
And triggering the clock synchronization initialization again when the clock synchronization period is finished.
2. The method of claim 1, wherein establishing communication between the computer PC, the TSN switch, and the plurality of motor controllers comprises:
setting the PC, the motor controller and the TSN switch to be in the same network segment of the same TSN domain;
the computer PC is used as a server, and a server socket is created;
setting the connection of the server to be in a multithreading mode, and carrying out polling monitoring;
each motor controller is used as a client to be connected to the server through a TSN switch respectively;
and the server side polls to acquire the connection of a new client side, and creates a sub-thread for communicating with the client side.
3. The method of claim 2, wherein the clock synchronization initialization comprises:
in the TSN domain, using a gPTP synchronization mode, aligning the hardware time stamps of the computer PC and each motor controller;
in each sub EtherCAT network, a distributed clock synchronization mechanism is adopted, each motor controller is used as a master station reference clock of each sub EtherCAT network, and the link propagation delay and the initial clock offset from the master station reference clock to a first motor driver in each corresponding slave station are calculated;
The first motor driver calculates a local clock error according to a reference clock of a master station, link propagation delay and an initial clock offset, and adjusts the local system time of the first motor driver to be a calibration clock of the first motor driver based on the local clock error;
sequentially adding a micro clock drift to the cascaded motor drivers on the basis of the calibration clock of the previous motor driver to obtain the calibration clock of each cascaded motor driver; the micro-clock drift is obtained by the fact that the computer PC sends a synchronization instruction in advance and the link transmission delay between the second motor driver and the first motor driver in each sub EtherCAT network is calculated.
4. The method of claim 3, wherein the first motor driver calculating a local clock error from the master station reference clock, the link propagation delay and the initial clock offset, and adjusting the first motor driver local system time to the first motor driver calibration clock based on the local clock error comprises:
calculating link propagation delay and initial clock offset from a reference clock to a corresponding first motor driver by taking each motor controller hardware time stamp as a master station reference clock;
The first motor driver calculates a local clock error according to the master station reference clock, the link propagation delay and the initial clock offset;
the initial clock offset is the time difference between the reference clock of the master station of the motor controller and the local clock of the first motor driver when the clock synchronization initialization process starts; the link propagation delay is a transmission delay between the motor controller to the first motor drive;
the local clock error of the first motor drive is calculated as follows:
E 1 =C i -T i -T refi
wherein E is 1 For the local clock error of the first motor driver corresponding to motor controller i, C i For the local clock, T, of the first motor drive corresponding to motor controller i i For the link propagation delay of the first motor driver corresponding to the motor controller i, T refi A reference clock for the motor controller i;
the first motor driver obtains a calibration clock based on the local system time and the local clock error adjustment.
5. The method of claim 4, wherein the control instruction packet includes a transmission time stamp;
the motor controller in each sub EtherCAT network receives the control instruction data packet, analyzes the control instruction data packet into a pulse signal and sends the pulse signal to the first motor driver in the sub EtherCAT network;
The first motor driver extracts the corresponding instruction according to addressing and transmits the rest instructions to the next motor driver through the EtherCAT bus, and the rest motor drivers are sequentially connected in cascade to receive pulse signals.
Each motor driver receives the pulse signals to drive the corresponding servo motor to move, and simultaneously records and uploads the received pulse signal time stamp to the computer PC;
and obtaining the total execution delay of the control instruction based on the received pulse signal time stamp and the sending time stamp.
6. The method of claim 5, wherein performing the servo motor fault repair when the computer PC detects that the servo motor motion state does not match the control command comprises:
each motor driver sequentially returns the recorded corresponding servo motor motion state data to the last motor driver in cascade until reaching the first motor driver, and the data are transmitted back to the computer PC through the motor controller and the TSN switch;
the PC judges whether the motion state of the servo motor meets the control instruction requirement or not;
and if the fault is not met, performing fault repair on the servo motor.
7. The method of claim 6, wherein said if not conforming to said servo motor fault repair comprises:
the first step, the computer PC judges the sub EtherCAT network where the failed servo motor is based on the servo motor running state data, and then judges the corresponding motor driver and motor controller;
secondly, judging the fault severity degree of the failed servo motor based on the running state data;
and thirdly, stopping the system, stopping/disabling the failed servo motor or performing online replacement of the servo motor based on the severity of the fault.
8. The method of claim 7, wherein stopping the system, stopping or disabling the failed servo motor, or performing an online replacement of the servo motor based on the severity of the failure comprises:
if the severity of the fault is a safety risk, immediately stopping the machine to repair the fault;
if the position and the speed of the servo motor are the position and the speed of the servo motor, the electric fault, the mechanical fault and the bearing fault, the servo motor cannot accurately sense the position and the speed, and the computer PC sends a command for stopping/disabling the servo motor, so that the fault servo motor is stopped/disabled;
If the temperature is abnormal or the communication data packet is lost, the servo motor is replaced online.
9. The method according to any one of claims 1-8, comprising:
the motor controller, the motor driver and the servo motor are positioned in an EtherCAT network and are connected through an EtherCAT interface and a bus;
each sub EtherCAT network consists of a motor controller, a plurality of motor drivers and corresponding servo motors, wherein the motor controller is a master station, and the motor drivers are slave stations.
10. The method of any one of claims 1-8, wherein the servo motor operating state data comprises: current position, speed, acceleration, power, temperature, current, voltage, fault code, alarm information, operation log, event record information of the servo motor.
CN202311430186.XA 2023-10-31 2023-10-31 Multi-motor synchronous control method based on TSN and EtherCAT heterogeneous network Pending CN117499175A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117714228A (en) * 2024-02-06 2024-03-15 长春晟博光学技术开发有限公司 Control method of heliostat controller based on Autbus communication mode

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117714228A (en) * 2024-02-06 2024-03-15 长春晟博光学技术开发有限公司 Control method of heliostat controller based on Autbus communication mode
CN117714228B (en) * 2024-02-06 2024-04-26 长春晟博光学技术开发有限公司 Control method of heliostat controller based on Autbus communication mode

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