CN117706980A

CN117706980A - Multi-machine cooperative control method based on time-sensitive network

Info

Publication number: CN117706980A
Application number: CN202311571503.XA
Authority: CN
Inventors: 宋俊霖; 边晓光; 蒲晓珉; 胡凡荣; 陈韬; 范旭杰; 蒋林; 田阳
Original assignee: Dongfang Electric Group Research Institute of Science and Technology Co Ltd
Current assignee: Dongfang Electric Group Research Institute of Science and Technology Co Ltd
Priority date: 2023-11-23
Filing date: 2023-11-23
Publication date: 2024-03-15

Abstract

The invention discloses a multi-machine cooperative control method based on a time-sensitive network, which is used for cooperatively controlling a plurality of processing machine tools in a large-scale power generation equipment production workshop, each machine tool is provided with a TSN controller, all the TSN controllers and a TSN switch form a TSN private network, and protocols such AS IEEE 802.1AS, IEEE 802.1Qbv, IEEE 802.1Qav and the like are supported; acquiring processing parameters and flow characteristics according to the processing time sequence, and sending basic signals of equipment formed by the parameters and the flow characteristics to a TSN switch by a TSN controller, and sending the basic signals to other TSN controllers through the TSN switch; and the TSN controller receives the equipment basic signal and combines the existing flow configuration condition calculation to realize time synchronization and flow scheduling. The invention fully utilizes the advantages of TSN in time synchronization and flow control, and effectively improves the processing and manufacturing efficiency of the equipment.

Description

Multi-machine cooperative control method based on time-sensitive network

Technical Field

The invention relates to the field of industrial control and intelligent manufacturing, in particular to a multi-machine cooperative control method based on a time-sensitive network.

Background

The large-scale power generation equipment is generally composed of a plurality of parts, each part needs to be processed and manufactured on different processing machine tools, certain dependence exists in processing among the parts, all the parts are assembled after being processed, and the whole processing and manufacturing process of the large-scale power generation equipment is completed.

Because the space between the traditional equipment manufacturing workshops is larger, the distance between the processing machine tools is longer, communication is needed through a field bus (such as RS232, RS485, CAN, USB, ethernet and the like), as shown in fig. 1, all control commands and sensor data of the processing machine tools are transmitted on the same bus, a competition relationship exists between the data, the data are transmitted on the bus for delay, the traditional field bus does not have the capacity of carrying out flow control and time synchronization on the transmitted data, the problems of uncertain communication time and uncontrollable communication flow exist, when a plurality of processing machine tools work cooperatively, accurate time synchronization cannot be carried out, priority transmission on important data cannot be guaranteed, larger delay gaps are reserved to ensure communication success, processing efficiency is low, and the overall productivity of workshops is reduced.

Disclosure of Invention

Aiming at the problems of low equipment processing efficiency caused by uncertain time synchronization and uncontrollable communication flow of a field communication bus in the discrete manufacturing process of the existing large-scale power generation equipment, the invention provides a multi-machine cooperative control method based on a time sensitive network, which can effectively solve the problems of the traditional industrial bus based on the advantages of TSN in time synchronization and flow control and improve the processing and manufacturing efficiency of the equipment.

The technical scheme of the invention is as follows:

a multi-machine cooperative control method based on a time sensitive network is characterized in that for a plurality of processing machine tools at different positions in a production workshop of a large-scale power generation device, corresponding TSN controllers are configured, all the TSN controllers corresponding to the processing machine tools and a TSN switch are subjected to wide area networking through an Ethernet to form a TSN private network, and the TSN private network supports protocols such AS IEEE 802.1AS, IEEE 802.1Qbv, IEEE 802.1Qav and the like.

A Time sensitive network (Time-Sensitive Network, TSN), a family of protocols that implements deterministic minimum Time delays in non-deterministic ethernet networks, is a set of protocol standards developed by TSN working groups in IEEE 802.1 working groups, defines a Time sensitive mechanism for ethernet data transmission, and adds deterministic and reliable features to standard ethernet networks to ensure real-Time, deterministic and reliable data transmission.

The TSN controller has a TSN communication function, can perform data communication of a TSN special protocol, and can control an executing mechanism (such as a motor and a cutter) on a processing machine tool to perform processing operation.

The control mode of the invention is as follows: firstly, classifying the processing machine tools, and collecting processing parameters and flow characteristics of each processing machine tool according to the time sequence requirements of processing; each TSN controller forms a basic signal of equipment according to parameters and flow characteristics of a corresponding processing machine tool, and sends the basic signal to a TSN switch, and the basic signal is sent to other TSN controllers through the TSN switch; and each TSN controller calculates according to the processing parameters and the flow characteristics of each processing machine tool sent by the TSN switch and by combining the existing flow configuration conditions, so that ns-level time synchronization and flow scheduling of each processing machine tool are realized.

The IEEE 802.1AS of the TSN switch is used for ensuring the clock synchronization of each processing machine tool connected in the TSN private network and reaching the accuracy error of ms level or even ns level; the method and process for time synchronization in TSNs are defined specifically by the IEEE 802.1AS universal precision time protocol (generalized Precision Time Protocol, gPTP), which is based on IEEE 1588V2 generation, provides globally accurate time synchronization, which is a specific configuration file for PTP. IEEE 1588, known as the precision clock synchronization protocol standard for network measurement and control systems, is also known as Precision Time Protocol (PTP), and is mainly used for clock synchronization of ethernet and nodes of a distributed network. IEEE 1588V2 is a second version of the PTP protocol. IEEE 802.1AS is not a protocol for IP routing and is based entirely on a two-layer network, but its mode of operation remains consistent with the PTP protocol.

Wherein gPTP is similar to the synchronization mechanism of PTP, a master clock (GrandMaster, GM) is selected and a synchronization clock tree is established in the whole gPTP domain through an optimal master clock algorithm (Best Master Clock Algorithm, BMCA), the master clock is used as a time reference of the whole gPTP domain and transmits calibration time information, and then a peer-to-peer path delay measurement mechanism is utilized to calculate time errors between master and slave clock ports for synchronization, namely, delay of data transmission between master ports and slave ports of different processing machine tools and residence time in a TSN switch are measured through gPTP protocol, and each processing machine tool corrects local time through the transmission delay and references of the time reference, so that each processing machine tool in the whole gPTP domain keeps time synchronization.

The path delay measurement time length is as follows:

wherein D is the total delay of path transmission, t _ir Representing the delay, t, of the pdelay_req message _ri Representing delay of the pdelay_res, t1 and t4 are moments when the master node sends out the pdelay_req and receives the pdelay_res message, and t2 and t3 are moments when the slave node receives the pdelay_req and sends out the pdelay_res message; pdelay_req is a message sent by the slave node to the master node for measuring the delay between the slave node and the master node; the pdelay_resp is the response of the master node to the pdelay_req message, and carries delay information between the master node and the slave node; pdelay_resp_follow_up is an additional response of the master node to the pdelay_resp message;

the clock synchronization deviation in the synchronization is calculated as follows:

offset＝t _s -t _m -D

wherein offset represents the clock synchronization offset value, t _s Time of presentationSynchronization initiation stage, t _m Indicating the time of day of the master and slave clock source devices.

For reliable and timely information delivery, the TSN switch proposes the IEEE 802.1Qbv standard on the basis of IEEE 802.1Q. A time aware scheduler (Time Aware Shaper, TAS) is defined in the IEEE 802.1Qbv standard to optimize the transmission priority of ethernet frames and ensure that information is delivered within a specified time. The basic idea of time-aware scheduling is to divide the communication of ethernet into fixed-length, repeated time slices, called periods, using Time Division Multiple Access (TDMA); each cycle is in turn divided into a plurality of finer granularity time slices, called time slots. Each time slot can be allocated to one or more of 8 ethernet priorities, that is, a virtual communication channel is formed in a specific time period, so that specific real-time data can be transmitted in a non-real-time data load in a staggered manner, and the influence of other burst or abnormal sending requests on real-time data transmission is reduced. The communication devices under the constraint of the IEEE 802.1Qbv standard need time synchronization and the same schedule is configured, i.e. all devices know what priority traffic frames should be sent per time slot.

The IEEE 802.1Qav (credit shaper) of the TSN switch is mainly used for reducing burst traffic and congestion in a network, queuing real-time frames and asynchronous frames respectively, giving the real-time frames the highest priority, and the network will send data with high credit value preferentially; controlling network traffic by a Credit-Based traffic shaping algorithm (CBS) of IEEE 802.1Qav through class priority of a data flow queue; the traffic shaping algorithm defines a set of parameters for each queue: an idle rate (idleSlope), a sending rate (sendSlope), an upper credit limit (highcredit), and a lower credit limit (low credit), wherein the queue increases the credit value with the idle rate in an idle state, decreases the credit value with the sending rate in the process of sending the data packet, and can only send data under the condition that the credit value is not negative;

the idle slope is calculated as follows:

idleSlope

the transmission slope is calculated as follows:

sendSlope＝idleSlope-portTransmitRate

where reservedBytes represents the number of bytes reserved, divframe interval represents the framing interval time, and portTransmitrate represents the port's transmission rate.

The technical scheme of the invention has the following beneficial effects:

the invention utilizes the performance advantages of the TSN network in the aspects of time synchronization precision and controllable flow scheduling, integrally improves the cooperation efficiency among processing machine tools, effectively improves the synchronization performance of the operation among a plurality of remote machines, and specifically comprises the following steps: (1) Time certainty of data communication between machine tools can be realized through time synchronization, and accuracy of sending control commands and receiving sensor data is guaranteed; (2) The most critical data (such as workpiece processing state, machine tool fault alarm signal and the like) can be preferentially sent through flow control, so that the processing quality is ensured; (3) Communication reliability can be guaranteed, so that processing quality is guaranteed, and processing and manufacturing efficiency of equipment is improved; (4) In addition, the TSN private network of the invention also supports Ethernet, allows the network to accurately provide time-critical data flows when needed, simultaneously allows less critical traffic to coexist on the network, can combine multiple types of networks into the same network structure, places critical data in a queue with higher priority for priority transmission, and places non-critical data in a low-priority queue, thereby reducing the total cost.

Drawings

Fig. 1 is a schematic diagram of a conventional fieldbus communication mode in the background art.

FIG. 2 is a schematic diagram of a control mode architecture according to the present invention.

Fig. 3 is a schematic diagram of an IEEE 802.1AS clock hierarchy of the present invention.

Fig. 4 is a schematic diagram of a peer-to-peer path delay measurement procedure used in the present invention.

Fig. 5 is a schematic diagram of a clock synchronization deviation calculation process in the present invention.

Fig. 6 is a schematic diagram of the IEEE 802.1Qbv TAS traffic shaping of the present invention.

Fig. 7 is a schematic diagram of the IEEE 802.1Qav CBS traffic shaping of the present invention.

Detailed Description

The technical scheme of the invention is further elaborated below in conjunction with the description and drawings.

AS shown in fig. 2, in a multi-machine cooperative control method based on a time-sensitive network, for a plurality of processing machine tools at different positions in a production workshop of a large-scale power generation device, the distance between each processing machine tool is about hundreds of meters, each processing machine tool is configured with a corresponding TSN controller, all the TSN controllers corresponding to the processing machine tools and a TSN switch are subjected to wide area networking through an ethernet network to form a TSN private network, and the TSN private network supports protocols such AS IEEE 802.1AS, IEEE 802.1Qbv, IEEE 802.1Qav and the like. The TSN controller has a TSN communication function, can perform data communication of a TSN special protocol, and can control an executing mechanism (such as a motor and a cutter) on a processing machine tool to perform processing operation.

The TSN switch defines a method and a process of time synchronization in the TSN through a general precision time protocol (gPTP) of IEEE 802.1 AS; the clock hierarchy in IEEE 802.1AS is shown in fig. 3, where a master clock (GM) is selected in the entire gPTP domain through an optimal master clock algorithm (BMCA), and the master clock is used AS a time reference of the entire gPTP domain and transmits calibration time information; the delay of data transmission between a master port and a slave port of different processing machines and the residence time in a TSN switch are measured through the gPTP protocol, and the local time is corrected by the processing machines through the transmission delay and reference time standard, so that the processing machines in the whole gPTP domain keep time synchronization.

In the IEEE 802.1AS (Audio/Video Bridging (AVB) Sync) standard, I, R, pdelay _req, pdelay_resp, pdelay_resp_foil_up are important messages for accurate clock synchronization and delay measurement.

I (Initialization) messages are sent by the network clock master node to initialize the clocks of all slave nodes in the network. After the master node sends the I message, the slave node will perform initial clock setting and synchronization according to the message.

An R (Announce) message is sent periodically by the network clock master node to inform the nodes throughout the network whether the clocks of themselves are reliable. The R message carries the clock status and reliability information of the master node, and the node can adjust its own clock according to these information.

The pdelay_ Req (Peer Delay Request) message is a message sent by the slave node to the master node for measuring the delay between the slave node and the master node. After the slave node sends the pdelay_req message, the master node calculates the time delay between the pdelay_req message and the slave node according to the received time stamp information.

The pdelay_ Resp (Peer Delay Response) message is the master's response to the pdelay_req message. After receiving the pdelay_req message, the master node immediately sends a pdelay_resp message to the slave node, where the pdelay_resp message carries delay information between the master node and the slave node.

The pdelay_resp_follow_ Up (Peer Delay Response Follow Up) message is an additional response by the master node to the pdelay_resp message. When the master node receives the pdelay_resp message sent from the slave node, a pdelay_resp_follow_up message may be sent, where the pdelay_resp_follow_up message contains more accurate delay information.

As shown in fig. 4, the specific calculation of the path delay measurement procedure is:

wherein D is the total delay of path transmission, t _ir Representing the delay, t, of the pdelay_req message _ri Represents the delay, t, of pdelay_res ₁ 、t ₄ Time t when a pdelay_req message is sent out and received for a master node ₂ 、t ₃ For the moment when the pdelay_req message is received and sent out from the node.

M (Master) is a Master clock node in the TSN network, S (Slave) is a Slave clock node in the TSN network, and all Slave clocks are required to be kept synchronous with a Master clock source;

the Sync message is sent by the network clock master node to synchronize the clocks of all the slave nodes in the entire network. The Sync message contains a time stamp, and all slave nodes will adjust their clocks according to this time stamp to achieve clock synchronization of all nodes in the network. The follow_up message is sent by the network clock master node for providing more detailed synchronization information to the slave node; it contains the timestamp of the Sync message and some other information related to the clock synchronization. After receiving the follow_up message, the slave node can more accurately adjust its own clock according to the information therein.

The process of calculating the synchronization deviation is shown in fig. 5, and the specific clock synchronization deviation is:

offset＝t _s -t _m -D

wherein offset represents the clock synchronization offset value, t _s Represents the initial phase of time synchronization, t _m Indicating the time of day of the master and slave clock source devices.

The TSN switch divides the communication on the ethernet into repeated time periods with fixed length through a time-aware traffic shaper (TAS) of IEEE 802.1Qbv, and in each time period, different time slices are separated again, and data is transmitted according to preset priority in the time slices, and the principle is shown in fig. 6.

The TSN switch controls network traffic through class priority of data flow queues through a credit-based traffic shaping algorithm (CBS) of IEEE 802.1 Qav; the traffic shaping algorithm defines a set of parameters for each queue: an idle rate (idleSlope), a sending rate (sendSlope), an upper credit limit (highcredit), and a lower credit limit (low credit), wherein the queue increases the credit value with an idle slope in an idle state, decreases the credit value with a sending slope during the sending process of the data packet, and the queue can only send data under the condition that the credit value is not negative, and the CBS principle is shown in fig. 7.

The idle slope is calculated as follows:

the transmission slope is calculated as follows:

sendSlope＝idleSlope-portTransmitRate

in the IEEE 802.1Qav (Audio Video Bridging (AVB) Systems) standard, reservedBytes, divframeintervalTime, portTransmitRate is an important parameter for realizing audio-video transmission and quality of service (QoS) control.

reservedBytes: indicating the number of reserved bytes. In AVB networks, a portion of the bytes in each data frame are reserved to ensure that sufficient bandwidth is available for audio-video streaming. These reserved bytes can be used for delay tolerant features (e.g., streaming media streams) to increase the buffering time for queuing and transmission, thereby alleviating network congestion and latency.

divframe interval time: representing the framing interval time. In AVB networks, the framing interval time is used to divide the time slices for traffic scheduling and transmission. Each time slice is used to transmit a different type of data stream, such as audio, video, etc. The framing interval time determines the duration of each time slice, i.e. the time window in which the data stream gets transmitted.

portTransmitrate: representing the transmission rate of the port. In AVB networks, each physical port has a fixed transmission rate that indicates the theoretical maximum rate at which the port can transmit. The transmission rate is typically measured in bits per second transmitted, for example 1Gbps (10-9 bps) or 100Mbps (10-6 bps).

These parameters play an important role in AVB networks, and are used to control key aspects such as bandwidth allocation, timing sequence and fluency of data streams, so as to realize high-quality audio/video transmission and quality of service guarantee.

The controller with TSN communication function is used for replacing a PLC which only supports the traditional field communication buses (such as RS232, RS485, CAN, USB and Ethernet), and intelligent upgrading and reconstruction of the processing machine tool are realized.

Claims

1. A multi-machine cooperative control method based on a time-sensitive network is characterized in that: for a plurality of processing machine tools at different positions in a large-scale power generation equipment production workshop, corresponding TSN controllers are configured, all the TSN controllers corresponding to the processing machine tools and a TSN switch are subjected to wide area networking through an Ethernet to form a TSN private network, and the TSN private network supports protocols such AS IEEE 802.1AS, IEEE 802.1Qbv, IEEE 802.1Qav and the like; the control principle of the method is as follows: firstly, collecting processing parameters and flow characteristics of each processing machine tool according to the time sequence requirements of processing; each TSN controller forms a basic signal of equipment according to parameters and flow characteristics of a corresponding processing machine tool, and sends the basic signal to a TSN switch, and the basic signal is sent to other TSN controllers through the TSN switch; and each TSN controller calculates according to the processing parameters and the flow characteristics of each processing machine tool sent by the TSN switch and by combining the existing flow configuration conditions, so that ns-level time synchronization and flow scheduling of each processing machine tool are realized.

2. The time-sensitive network-based multi-machine cooperative control method according to claim 1, wherein: the TSN switch defines a time synchronization method and process in the TSN through a universal precision time protocol gPTP of IEEE 802.1 AS; selecting a master clock in the whole gPTP domain through an optimal master clock algorithm, establishing a synchronous clock tree, taking the master clock as a time reference of the whole gPTP domain, transmitting calibration time information, and calculating time errors between master clock ports and slave clock ports by utilizing a peer-to-peer path time delay measurement mechanism to carry out synchronization;

the path delay measurement time length is as follows:

wherein D is the total delay of path transmission, t _ir Representing the delay, t, of the pdelay_req message _ri Represents the delay, t, of pdelay_res ₁ 、t ₄ Time t when a pdelay_req message is sent out and received for a master node ₂ 、t ₃ For the moment when the Pdelay_Req is received and the Pdelay_Res message is sent out from the node; pdelay_req is a message sent by the slave node to the master node for measuring the delay between the slave node and the master node;

the pdelay_resp is the response of the master node to the pdelay_req message, and carries delay information between the master node and the slave node; pdelay_resp_follow_up is an additional response of the master node to the pdelay_resp message;

offset＝t _s -t _m -D

3. The time-sensitive network-based multi-machine cooperative control method according to claim 1, wherein: the IEEE 802.1Qbv of the TSN switch is used for solving the problem of certainty of frame scheduling delay, a time sensing scheduler is used for distributing a specific time slot for time sensitive key data with higher priority, and in a specified time node, all nodes in a network must ensure the passing of important data frames preferentially; the communication on the Ethernet is divided into repeated time periods with fixed length by a time-aware scheduler of IEEE 802.1Qbv, and data is transmitted according to preset priority in different time slots of each time period.

4. The time-sensitive network-based multi-machine cooperative control method according to claim 1, wherein: the TSN switch controls network flow through the class priority of the data flow queue through the credit-based flow shaping algorithm of IEEE 802.1 Qav; the traffic shaping algorithm defines a set of parameters for each queue: the queue increases the credit value with an idle slope in an idle state, decreases the credit value with a sending slope in the sending process of the data packet, and can only send data under the condition that the credit value is not negative.

The idle slope is calculated as follows:

the transmission slope is calculated as follows:

sendSlope＝idleSlope-portTransmitRate