CN115604127A

CN115604127A - Modbus TCP (Transmission control protocol) cross-TSN (time delay network) joint scheduling method

Info

Publication number: CN115604127A
Application number: CN202211210702.3A
Authority: CN
Inventors: 魏旻; 邢益铭; 景瞻; 王平
Original assignee: Chongqing University of Post and Telecommunications
Current assignee: Chongqing University of Post and Telecommunications
Priority date: 2022-09-30
Filing date: 2022-09-30
Publication date: 2023-01-13
Also published as: WO2024066285A1

Abstract

The invention relates to a Modbus TCP cross-TSN joint scheduling method, and belongs to the field of industrial communication. The method comprises the following steps: s1: constructing a heterogeneous network scheduling model, including establishing a heterogeneous network and a flow demand model; s2: adopting a scheduling preprocessing algorithm to complete priority preprocessing in network transmission; s3: and constructing a two-dimensional offline boxing problem model, namely performing problem conversion by adopting a two-dimensional offline boxing algorithm to abstract transmission requirements into two-dimensional objects, and changing a placing principle and a sequence in a boxing process by combining network transmission priority, so that a scheduling problem is optimally solved. The invention can improve the operation efficiency of the scheduling algorithm, reduce the scheduling calculation difficulty and realize the optimization solution of the scheduling problem.

Description

Modbus TCP (Transmission control protocol) cross-TSN (time delay network) joint scheduling method

Technical Field

The invention belongs to the field of industrial communication, and relates to a Modbus TCP cross-TSN joint scheduling method.

Background

As an important support technology for industrial intelligence, a network technology is a premise for realizing interconnection and intercommunication between equipment and a system. Data, control, video and management flows coexist in an industrial network, but the priority, real-time and deterministic requirements of these flows are different. In this case, the industrial network needs to connect some devices having different communication requirements in terms of data rate, delay and reliability. Therefore, IT is a challenge to implement efficient data scheduling in a converged Operation Technology (OT) and Information Technology (IT).

In recent years, with the development of Time-Sensitive Networking (TSN), the industrial field has started to research ITs introduction to achieve converged communication of OT and IT. TSN refers to a set of "sub-standards" that are formulated based on specific application requirements under the framework of the IEEE 802.1 standard, and is intended to establish a "generic" time-sensitive mechanism for ethernet protocols to ensure time-certainty in network data transmission. The TSN allows the periodic control communication requirement and the aperiodic data to be transmitted in the same network, has better performance in the aspects of bandwidth utilization rate, guarantee of transmission performance of the time-sensitive data and the like, and can ensure the transmission of the time-sensitive data in the industrial automation network with low time delay and low jitter.

Since there are many different types of industrial ethernet networks in an industrial network, and an industrial wired network and an industrial wireless network coexist due to their advantages that they cannot be replaced, when a TSN is introduced as a backbone network to transmit data streams, different communication protocols are used on different terminal device interfaces, so as to generate diversified combinations, such as Modbus TCP, WIA-PA, AUTBUS, etc. The Modbus TCP is a communication protocol which is relatively universal in an industrial field, has the advantages of free acquisition, low network implementation cost, easy integration, strong transmission capability and the like, and is applied to a large number of terminal devices. However, the Modbus TCP protocol has no time-sensitive characteristic, is incompatible with the TSN, cannot satisfy the real-time and priority control, and the like, so that the problem of the heterogeneous network coordinated scheduling of the Modbus TCP and the TSN is researched, the cross-network low-delay and deterministic transmission are ensured, and the method has important significance for the development of the fields of industrial communication and automation control.

The generation problem of schedules for industrial networks, especially industrial heterogeneous networks, is constantly under study, the schedule generation problem is considered to be NP-complete, and most algorithms currently work on generating near-optimal feasible solutions.

Therefore, a new method for scheduling Modbus TCP and TSN in cooperation with heterogeneous networks is needed to solve the above problems.

Disclosure of Invention

In view of this, the invention aims to provide a Modbus TCP cross-TSN joint scheduling method, which improves the operation efficiency of a scheduling algorithm, reduces the scheduling calculation difficulty, and can realize the optimal solution of the scheduling problem.

In order to achieve the purpose, the invention provides the following technical scheme:

a Modbus TCP cross-TSN joint scheduling method comprises the following steps:

s1: constructing a heterogeneous network scheduling model, including establishing a heterogeneous network and a flow demand model;

s2: adopting a scheduling preprocessing algorithm to complete priority preprocessing in network transmission;

s3: and (3) constructing a two-dimensional off-line packing problem model, namely performing problem conversion by adopting a two-dimensional off-line packing algorithm to abstract transmission requirements into two-dimensional objects, and changing a placing principle and a sequence in a packing process by combining network transmission priority, so that a scheduling problem is optimally solved.

Further, in step S1, constructing a heterogeneous network scheduling model specifically includes: defining a heterogeneous network N (L) consisting of a plurality of links L e L = { L } _TSN ,L _Mod Composition, where L ∈ L _TSN Is a TSN link, L ∈ L _Mod Is a Modbus link; a stream transmitted in a heterogeneous network N (L) is defined as S = { S = { S = } ₁ ,S ₂ ,…,S _i ,…S _n N represents the total number of streams S transmitted in the heterogeneous network N (L);

considering periodic and deterministic transmission, the stream S transmitted in the heterogeneous network N (L) is periodic by its period T _S And a load B _S Defining; the transmission requirement R (S) of stream S is defined by the set:

R(S)＝{ID _S ,P _S ,T _S ,B _S ,D _S } (1)

wherein, ID _S Denotes the number of the stream S, P _S Indicating the priority of the stream S, D _S Representing the upper end-to-end delay limit for stream S.

Further, in step S2, a scheduling pre-processing algorithm is used to complete the priority pre-processing, which specifically includes the following steps:

s21: carrying out priority mapping on the transmission requirement R (S) of the stream S;

s22: all selectable paths of the stream S for completing the end-to-end transmission and the end-to-end time delay sigma d on each path are calculated _S ；

S23: defining equal priority blocking

And high priority blocking

S24: calculating and analyzing whether an end-to-end time delay upper limit D specified in the transmission requirement R (S) of the stream S is met _S If not, then

The priority of the stream is increased by one level and recalculated until the transmission requirement is met, and after the preprocessing of all the priorities is completed, the scheduling preprocessing algorithm is ended.

Further, in step S21, the priority mapping specifically includes: priority P for stream S _S Defining a binary function F (x, y) which is calculated by the two influencing factors x and y, and mapping the calculation result to the priority P of the stream S _S ；

Where x denotes the data type of stream S, y denotes the urgency of stream S, and a and b denote the weights taken by the two influencing factors, respectively. For ease of calculation, the present invention quantifies the data type x and urgency y of stream S into three levels, respectively, as follows:

the invention quantizes the data type x of stream S as:

1) For a read-write event, the requirement on end-to-end deterministic transmission is higher, so the data type x of the read-write event is assigned to be 3;

2) For a diagnostic query event, which is generally required for end-to-end deterministic transmission, its data type x is assigned a value of 2;

3) For other events, which do little to do with end-to-end deterministic transmission, its data type x is assigned a value of 1.

At the same time, the present invention quantifies the urgency y of stream S as:

1) For interactive important data services, the requirement on end-to-end deterministic transmission is higher, so the urgency degree y of the interactive important data services is assigned to be 3;

2) For non-interactive background data service, the requirement on end-to-end deterministic transmission is general, and a certain time delay can be waited in the transmission process, so the urgency degree y of the non-interactive background data service is assigned to be 2;

3) For non-real-time elastic data traffic, the requirement on end-to-end deterministic transmission is basically not made, and the traffic can be considered to be abandoned when network congestion occurs, so the urgency degree y of the traffic is assigned to 1.

Further, in step S22, an end-to-end delay Σ d of the stream S is calculated _S The expression is:

wherein,

indicating the processing delay of the protocol stack at the transmitting end,

represents a link l _S (n _i ,n _j ) The propagation delay of the signal is reduced to zero,

representing the processing time delay of a protocol stack at a receiving end; d _sw The time delay of the switch is represented,

wherein

Representing the time from when the switch receives a message to when it is placed in the queue,

representing the time from when a data frame is placed in the switch egress port queue until it is dequeued,

representing the transmission delay of a single node.

Further, in step S3, constructing a two-dimensional offline boxing problem model, specifically including the following steps:

s31: the stream S transmitted in the heterogeneous network corresponds to the two-dimensional article, the time domain resource corresponds to the box, and the problem conversion is completed;

s32: cluster period T over stream S transport _LCM And a minimum period T _GCD Converting the one-dimensional transmission process of the stream S in the time domain into a two-dimensional form, and matching the two-dimensional off-line boxing problem; wherein a cluster period T is defined _LCM Is a period T _S Defining a minimum period T, is a minimum common multiple (LCM) _GCD Is a period T _S Greatest Common Divisor (GCD);

s33: according to the conversion idea of step S32, the stream S is converted into a two-dimensional article having a width W _S And height H _S Period T of exactly and flowing _S And a load B _S Correspondingly, it is expressed as:

further, step S32 specifically includes the following steps:

s321: cluster period T for transmitting a stream S on a time axis _LCM At a minimum period T _GCD Detaching, sequentially stacking in time sequence from bottom to top, and longitudinally arranging to obtain a minimum period T _GCD The stacked objects are regarded as a box;

s322: the minimum period of detachment is the width W of the box _box I.e. the width of the bin is equal to the minimum period in the time domain, expressed as:

W _box ＝T _GCD

s323: height H of the box _box Then for each minimum period of the stack up, it is expressed in time domain as:

s324: in the two-dimensional time domain diagram of the box model, the travel track of the time axis is from the point (0,T) ₁ ) Initially, advancing in the positive x-axis direction; after the first minimum period T is completed _GCD I.e. the arrival point (T) _GCD ,T ₁ ) Then, the process returns to (0,T) ₁ ) Dots, then proceed in the positive y-axis direction to dot (0, T) ₂ ) Then continue to advance in the positive x-axis direction, and so on until T is completed _n Minimum period T of _GCD I.e. to a point (T) _GCD ,T _n ) And then, the transmission is completed.

The invention has the beneficial effects that: the invention firstly carries out scheduling pretreatment to improve the operation efficiency of the algorithm and reduce the scheduling calculation difficulty. Then, the scheduling problem is converted, and the solution of the boxing problem is applied to the scheduling problem of the heterogeneous network. Through further research on the packing problem, the invention provides an improved two-dimensional off-line packing problem scheduling algorithm, the problem conversion is carried out in a mode of abstracting a transmission demand into a two-dimensional object, and the placing principle and the sequence in the packing process are changed by introducing the concept of priority in network transmission, so that the scheduling problem is optimized and solved.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims thereof.

Drawings

For the purposes of promoting a better understanding of the objects, aspects and advantages of the invention, reference will now be made to the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a field-level industrial IOT cross-TSN heterogeneous network scheduling architecture diagram;

FIG. 2 is a heterogeneous network N (L) model;

FIG. 3 is a system process flow diagram;

FIG. 4 is a flow chart of scheduling pre-processing;

FIG. 5 is a schematic diagram of a problem of converting time domain resources into two-dimensional offline binning;

FIG. 6 is a two-dimensional time domain diagram of a box model;

FIG. 7 is a flow chart of a two-dimensional offline binning algorithm;

FIG. 8 is a schematic representation of the conversion of a stream into two-dimensional articles of example 1;

FIG. 9 is a schematic view of packing in example 1;

FIG. 10 is a schematic representation of the conversion of a stream into a two-dimensional article in example 2;

fig. 11 is a schematic view of packing in example 2.

Detailed Description

The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It should be noted that the drawings provided in the following embodiments are only for illustrating the basic idea of the present invention in a schematic way, and the features in the following embodiments and embodiments may be combined with each other without conflict.

Referring to fig. 1 to 11, the present invention provides a Modbus TCP cross-TSN joint scheduling method, which first performs scheduling preprocessing to improve the algorithm operation efficiency and reduce the scheduling calculation difficulty. Then, the scheduling problem is converted, and the solution of the boxing problem is applied to the scheduling problem of the heterogeneous network. Through further research on the packing problem, the invention provides an improved two-dimensional off-line packing problem scheduling method, which is used for carrying out problem conversion in a mode of abstracting a transmission demand into a two-dimensional object, and changing a placing principle and a sequence in a packing process by introducing a concept of priority in network transmission, so that the scheduling problem is optimized and solved.

1. Model building and constraint condition analysis

1) TSN (Trans-TSN) cross heterogeneous network scheduling architecture of field-level industrial Internet of things

In combination with the characteristics of a Modbus TCP network topology and a TSN, with reference to standards such as ISO/IEC/IEEE 8802-1Q, 2020/AMD31:2021 and IEC/IEEE 60802, the invention designs a field-level industrial Internet of things cross-TSN heterogeneous network scheduling architecture as shown in FIG. 1.

The architecture is composed of a user plane, a control plane and a data plane, which are respectively introduced in detail as follows:

(1) User side: the user plane is composed of user plane APPs, and is responsible for receiving and sending instructions, and users provide data input and obtain data feedback output.

(2) A control surface: the control plane is composed of two industrial network system managers and an Industrial Software Defined Controller (ISDC). The former (two industrial network system managers) respectively manage the industrial wired network connected with the former, and the cooperative scheduling interface of the former is communicated with the industrial gateway of the data plane to obtain the state data of the industrial network. The latter (industrial software defined controller (ISDC)) is composed of a co-scheduling subsystem, a northbound interface, a southbound interface, and a westbound interface. The cooperative scheduling subsystem is used for calculating the network state information and generating a scheduling table; the northbound interface is connected with the user plane APP and is responsible for sending state information of a network or receiving a command of a user; the southward interface is connected with the CNC configuration interface of the data plane and the industrial gateways in the industrial networks on the two sides and is responsible for reading field network data and issuing a scheduling scheme; and the east-west interface is responsible for carrying out network state information interaction with the industrial network system manager.

(3) Data plane: the data plane is composed of an industrial wired network and TSN field devices and is used for realizing forwarding of industrial wired data. The Modbus network 1 sends data, and the data are forwarded through the TSN and received by the Modbus network 2.

2) For the establishment of the network and traffic model, the following definitions of terms are provided, as shown in Table 1

Table 1 definition of terms

The invention defines a heterogeneous network N (L) formed by a plurality of links L epsilon L = { L = [ ] _TSN ,L _Mod Is composed of where L ∈ L _TSN Is a TSN link, L ∈ L _Mod Is a Modbus link. Transmission in heterogeneous network N (L) is defined as S = { S = } ₁ ,S ₂ ,…,S _i ,…S _n N denotes the total number of streams S transmitted in the heterogeneous network N (L), and the network model thereof is shown in fig. 2.

Considering periodic and deterministic transmission, the stream S transmitted in the heterogeneous network N (L) is periodic by its period T _S And a load B _S And (4) defining. The transmission requirement R (S) of stream S is defined by the set:

R(S)＝{ID _S ,P _S ,T _S ,B _S ,D _S } (1)

wherein, ID _S Represents the number of stream S; p is _S Represents the priority of the stream S; d _S Representing the upper end-to-end delay bound for flow S.

The processing flow of the cooperative scheduling subsystem and the industrial network system manager is shown in fig. 3, and the scheduling algorithm flow is shown in fig. 3. The task of the industrial network system manager is to find a schedulable solution meeting the requirements through a scheduling algorithm according to the network characteristics and the constraint conditions determined by the transmission requirements R (S) of the stream S.

2. Design of scheduling algorithm

1) Scheduling pre-processing algorithm

1.1 Overview of scheduling Pre-processing Algorithm

Before boxing scheduling is carried out, scheduling preprocessing is carried out firstly, so that the operation efficiency of an algorithm is improved, and the scheduling calculation difficulty is reduced. Scheduling pretreatment: firstly, priority mapping is carried out on the transmission requirement R (S) of the stream S, which is given by the following section 1.2); then all the optional paths of the stream S for completing the end-to-end transmission and the end-to-end time delay sigma d on each path are analyzed and calculated _S Given in section 1.3) below; next, both equal priority blocking and high priority blocking are defined, given in section 1.4) below; finally, calculating and analyzing whether an end-to-end time delay upper limit D specified in the transmission requirement R (S) of the stream S is met _S If not, the priority of the stream is upgraded by one level and recalculated until the transmission requirement is met, after the preprocessing of all the priorities is finished, the scheduling preprocessing algorithm is finished, and a flow chart and a pseudo code are given by the following section 1.5).

1.2 ) priority mapping

Priority P for stream S _S The invention defines a binary function F (x, y) which is calculated by the two influencing factors x and y and maps the calculation result to the priority P of the stream S _S 。

Where x denotes the data type of the stream S and y denotes the urgency of the stream S. a and b represent the weights occupied by the two influencing factors, respectively. For ease of calculation, the present invention quantifies the data type x and urgency y of flow S into three levels, respectively, as follows:

the present invention quantizes the data type x of stream S as:

(1) For a read-write event, the requirement on end-to-end deterministic transmission is higher, so the data type x of the read-write event is assigned to be 3;

(2) For a diagnostic query event, which is generally required for end-to-end deterministic transmission, its data type x is assigned a value of 2;

(3) For other events, which do little to do with end-to-end deterministic transmission, its data type x is assigned a value of 1.

Meanwhile, the invention quantifies the urgency y of the stream S as:

(1) For interactive important data services, the requirement on end-to-end deterministic transmission is higher, so the urgency degree y of the interactive important data services is assigned to be 3;

(2) For non-interactive background data service, the requirement on end-to-end deterministic transmission is general, and a certain time delay can be waited in the transmission process, so the urgency degree y of the non-interactive background data service is assigned to be 2;

(3) For non-real-time elastic data traffic, the requirement on end-to-end deterministic transmission is basically not made, and the traffic can be considered to be abandoned when network congestion occurs, so the urgency degree y of the traffic is assigned to 1.

In summary, the priority mapping is shown in table 2.

Table 2 example table of priority mapping

ID	a	x	b	y	ax+by	F(x,y)
							1	0.9	3	0.8	3	5.1	6
2	0.8	3	0.6	2	3.6	4
							3	0.6	3	0.4	1	2.2	3
4	0.5	2	0.7	3	3.1	4
							5	0.8	2	0.5	2	2.6	3
6	0.7	2	0	1	1.4	2
							7	0.4	1	0.8	3	2.8	3
8	0.1	1	0.3	2	0.7	1
							9	0.1	1	0	1	0.1	1

1.3 End-to-end delay analysis

In the process of a flow S from a sending end to a receiving end, the end-to-end delay which is possibly generated theoretically mainly comprises the following parts:

(1) Sending end protocol stack processing delay

(2) Switch delay d _sw ；

Processing time delay: time from receiving a message by a switch to queuing it

Depending on the processing power of the switch;

queuing delay: time from when a data frame is put into a switch egress port queue until it is dequeued

Depending on the scheduling instant on the path port;

and (3) sending time delay: the data frame is sent out at an output port, and the sending time delay of a single node is expressed as

Depending on the link bandwidth and message size;

thus, the switch latency d _sw Can be expressed as:

wherein the link l _S (n _i ,n _j ) Propagation delay of

Depending on the channel bandwidth and cable length of the link.

Receiving end protocol stack processing delay

To sum up, let the theoretical end-to-end delay of stream S be Σ d _S It can be represented as:

1.4 Priority blocking definition

Priority blocking is defined herein as follows:

(1) The Same Priority Blocking (SPB) indicates an extra delay that may be brought to a current frame by a Same Priority frame, generally indicates an extra delay brought by all frames belonging to a Same buffer queue and arranged before the current frame, and indicates the extra delay as

(2) High Priority Blocking (HPB), which represents the extra delay brought by a high Priority frame to a current frame, is usually because when the high Priority frame and the current frame are transmitted simultaneously, a scheduling algorithm will preferentially serve the high Priority, thereby bringing extra delay to the current frame, which is represented as extra delay

1.5 Pseudo code and flow chart for scheduling pre-processing algorithm

The scheduling pre-processing algorithm pseudo-code is shown as algorithm 1.

In summary, the scheduling pre-processing flow is shown in fig. 4.

2) Two-dimensional off-line boxing algorithm

2.1 Overview of binning algorithm

The heterogeneous network joint optimization scheduling problem is an NP complete problem, namely a complete polynomial nondeterministic problem. The solving difficulty of the NP complete problem is related to variable quantity and constraint conditions, and the more complex the network topological structure is, the more the service quantity is, the larger the solving difficulty of the scheduling solution is.

The packing problem is a discrete combination optimization problem, which means that on a discrete and limited mathematical structure, a solution which meets a given condition and enables the objective function value to reach the maximum value or the minimum value is searched. The main research is the relation between boxes and articles, which is generally divided into three problems of one-dimensional boxing, two-dimensional boxing and three-dimensional boxing. The classical packing problem requires placing a certain number of articles in boxes of the same capacity so that the sum of the article sizes in each box does not exceed the box capacity, and the packing algorithm requires the optimization of the function of the objective function under the constraints given above. Learning of the packing algorithm can learn that the packing problem belongs to the NP problem, and the NP problem can be classified into different types according to different application scenes and different constraint conditions. The packing problem has been developed for hundreds of years, and a plurality of packing algorithms with excellent performance exist, and can be used for solving the heterogeneous network scheduling problem.

2.2 Analysis of feasibility of problem transformation

The essence of the heterogeneous network joint scheduling problem is that data streams are arranged in heterogeneous network links according to scheduling requirements, so that the heterogeneous network can carry out end-to-end scheduling according to the transmission requirements; for the essence of the two-dimensional offline boxing problem, two-dimensional articles are purposefully placed in empty boxes according to requirements, and finally, the result of meeting the requirements and optimizing is achieved. Therefore, the essence of the two problems is similar, and certain things are arranged into certain space and time according to certain rules, which are specifically expressed as follows:

(1) In the problem of heterogeneous network joint scheduling, time domain resources are limited, and the total time length of the time domain resources is greater than the sum of all services to be transmitted, that is, the network bandwidth can satisfy all the transmission services; in the case of the packing problem, the corresponding characteristic is that only one box is packed, and the space is larger than the total size of all two-dimensional articles.

(2) In the problem of heterogeneous network joint scheduling, the constraint of a network architecture requires that all periodic flows and aperiodic flows cannot conflict; in the case of the case-packing problem, the case-packing algorithm corresponding to the case-packing problem can also restrict the condition that the two-dimensional objects cannot be overlapped.

(3) In the heterogeneous network joint scheduling problem, the transmission requirements of periodic and non-periodic streams are known before the heterogeneous network is powered on; in the case of the boxing problem, the offline boxing problem is associated with, and information such as the length and width of all the two-dimensional articles is known before boxing.

(4) In the problem of heterogeneous network joint scheduling, transmission time slots are generally arranged for periodic and aperiodic streams according to priority so as to meet end-to-end scheduling of the heterogeneous network; in the case packing problem, the case packing algorithm corresponding to the case packing algorithm can place the two-dimensional articles by taking the priority as a constraint condition, so that the efficient space utilization rate and the reasonable placement rule are ensured.

2.3 Two-dimensional offline binning problem model

The invention defines the cluster period T of stream S transmission _LCM Expressed as a period T _S The Least Common Multiple (LCM), i.e.:

T _LCM ＝LCM(T _S ) (5)

therefore, it can be ensured that all streams are transmitted at least once in one cluster period, the transmission times are the same in each cluster period, and the heterogeneous network also performs cyclic scheduling by using the cluster period as a basic unit.

The invention also defines the minimum period T of the transmission of the stream S _GCD Is shown asPeriod T _S The Greatest Common Divisor (GCD), namely:

T _GCD ＝GCD(T _S ) (6)

the invention constructs an abstract process of heterogeneous network joint scheduling on a two-dimensional offline boxing problem, which comprises the following steps:

(1) Conceptually, the stream S transmitted in the heterogeneous network is corresponding to a two-dimensional article, and the time domain resource is corresponding to a box, so that the problem conversion is completed.

(2) Cluster period T over stream S transport _LCM And a minimum period T _GCD The one-dimensional transmission process of the stream S in the time domain is converted into a two-dimensional form, and the two-dimensional form is matched with the two-dimensional off-line boxing problem, and the specific conversion process is as follows.

a) Cluster period T for transmitting a stream S on a time axis _LCM According to a minimum period T _GCD Disassembling, sequentially stacking in time sequence from bottom to top for longitudinal arrangement, and further adjusting minimum period T _GCD The stacked object is regarded as a box as shown in fig. 5.

b) The minimum period of the unpacking is the width of the box, i.e. the width of the box is equal to the minimum period in the time domain, and is expressed as:

W _box ＝T _GCD (7)

c) The height of the box is the sum of each minimum period of the stack, which can be expressed in time domain as:

in the two-dimensional time domain diagram of the box model shown in FIG. 6, the travel locus of the time axis is from the point (0,T) ₁ ) Initially, advancing in the positive x-axis direction. After the first minimum period T is completed _GCD I.e. the arrival point (T) _GCD ,T ₁ ) Then, the process returns to (0,T) ₁ ) The point, then proceeds in the positive y-axis direction to point (0 ₂ ) Then continue to advance in the positive x-axis direction, and so on until T is completed _n Minimum week ofPeriod T _GCD I.e. to a point (T) _GCD ,T _n ) And then, the transmission is completed.

(3) According to the aforementioned conversion concept, the stream S is converted into two-dimensional articles having a width W _S And height H _S Just enough to coincide with the period T of the stream _S And a load B _S Correspondingly, can be expressed as:

2.4 Two-dimensional offline binning algorithm pseudo-code and flow chart

The two-dimensional offline binning algorithm pseudo code is shown in algorithm 2.

In summary, the two-dimensional offline binning algorithm flow is shown in fig. 7.

Scheduling example 1:

1. scheduling pre-processing flow

The user inputs the transmission requirements according to equation (1), as shown in table 3:

table 3 transmission requirement table

ID _S	a	x	b	y	T _S	B _S	D _S
								1	0.9	3	0.8	3	100	100	1000
2	0.9	3	0.7	2	200	400	1000
								3	0.8	2	0.7	3	600	400	1000
4	0.9	2	0.6	2	200	300	1000
								5	0.7	2	0.4	1	200	500	1000
6	0.5	1	0.4	1	600	200	1000

The priority mapping is performed according to equation (2), as shown in table 4:

table 4 priority mapping table

ID _S	a	x	b	y	ax+by	F(x,y)	P _S
								1	0.9	3	0.8	3	5.1	6	6
2	0.9	3	0.7	2	4.1	5	5
								3	0.8	2	0.7	3	3.7	4	4
4	0.9	2	0.6	2	3	3	3
								5	0.7	2	0.4	1	1.8	2	2
6	0.5	1	0.4	1	0.9	1	1

2. Boxing process

Fig. 8 shows a schematic diagram of a given data flow information and conversion into a two-dimensional article, which is a case when there is only one flow for each type of priority, that is, a case when there is no priority conflict.

All two-dimensional articles are loaded into the box according to a box packing algorithm, a schematic diagram is shown in fig. 9, and the method comprises the following specific steps:

s0: arranging the converted two-dimensional articles in sequence from left to right according to the priority from high to low and the width;

s1: dividing each two-dimensional article along the transverse direction, and corresponding the height of each two-dimensional article to the sub-height of each period;

s2: the principle of placing two-dimensional articles is as follows: the streams are sequentially arranged from left to right and from bottom to top, wherein the former means that the stream with the highest priority is transmitted first, and the latter means that the streams are transmitted on a time axis in time sequence. Firstly, loading a first two-dimensional article with the priority of 6 into the leftmost side of the box, taking the axis close to the abscissa as a reference for placing the two-dimensional article, and averagely placing the sub-articles divided in the S1 in a longitudinal space to show that the sub-articles are transmitted according to the periodic interval of the flow;

s3: judging whether the left width of the right side of the previous two-dimensional article is enough to accommodate the next two-dimensional article to be boxed, namely whether enough resources are arranged in the minimum period or not to arrange the flow of the secondary priority for transmission; if the two-dimensional articles can be loaded, repeating the step of loading S2, and loading the two-dimensional articles with the priority of 5;

s4: repeating the judging process of the S3 and the boxing process of the S2, and loading the two-dimensional articles with the priority of 4;

s5: and repeating the judging process of the S3, wherein the remaining width on the right side of the previous two-dimensional article cannot accommodate the next two-dimensional article to be boxed at the moment, namely that the remaining resources in the minimum period cannot arrange the flow of the second priority for transmission, and jumping to the previous row by the time axis, namely starting the boxing cycle of the second minimum period. At this time, the judging process of S3 and the boxing process of S2 are repeated, and the two-dimensional articles with the priority of 3 are loaded;

s6: repeating the judging process of the S3 and the boxing process of the S2, and loading the two-dimensional articles with the priority of 2;

s7: and repeating the judging process of S5 and the boxing process of S2, and loading the two-dimensional articles with the priority of 1.

Circulating to the upper right corner of the box, finishing, if the two-dimensional articles to be boxed still exist at the moment, indicating that the transmission requirement cannot be scheduled, and returning non-schedulable information to the user; if all of the two-dimensional items are loaded into the bin at this time, it is indicated that the transfer request is dispatchable.

S8: the two-dimensional articles are restored to each minimum transmission period, which is the reverse process of folding the time axis into a box, wherein the box is formed by combining a plurality of minimum periods, and the boxing result needs to be restored to the scheduling table shown in table 5.

Table 5 transmission demand scheduling schedule

Scheduling example 2:

1. scheduling pre-processing flows

The user enters the transmission requirements according to equation (1) as shown in table 6:

table 6 transmission requirement table

ID _S	a	x	b	y	T _S	B _S	D _S
								1	0.9	3	0.9	3	100	100	1000
2	0.8	3	0.9	3	200	200	1000
								3	0.8	2	0.9	3	100	100	1000
4	0.9	3	0.7	2	300	200	1000
								5	0.8	2	0.8	2	600	300	1000
6	0.7	2	0.7	2	600	300	1000

The priority mapping is performed according to equation (2), as shown in table 7:

TABLE 7 priority mapping table

ID _S	a	x	b	y	ax+by	F(x,y)	P _S
								1	0.9	3	0.9	3	5.4	6	6
2	0.8	3	0.9	3	5.1	6	6
								3	0.8	2	0.9	3	4.3	5	5
4	0.9	3	0.7	2	4.1	5	5
								5	0.8	2	0.8	2	3.2	4	4
6	0.7	2	0.7	2	2.8	3	3

2. Boxing process

Fig. 10 shows a schematic diagram of a given data stream information and conversion into a two-dimensional article, which is a case when there is more than one stream for each type of priority, that is, a case when there is a priority conflict.

All two-dimensional articles are packed into bins according to a bin packing algorithm, as shown in fig. 11.

s2: the principle of placing two-dimensional articles is the same as that of Case1. In the case of equal priority transmission, the blocking of equal priority caused by two packing orders in (1) is first compared

Selecting a boxing mode with smaller time delay for boxing;

s3: the procedure was determined as in Case1. The process of transmission with the same priority is the same as S2;

s4: repeating the judging flow and the boxing flow of the Case1, and loading the conflict-free two-dimensional articles with the priority of 4;

s5: repeating the judging process and the boxing process of Case1, and loading the conflict-free two-dimensional articles with the priority of 3;

s6: the two-dimensional article is restored to each minimum transmission period, which is the reverse process of the time axis folding process into a box, the box is formed by combining a plurality of minimum periods, and the boxing result needs to be restored to the scheduling time table shown in table 8.

Table 8 transmission demand scheduling schedule

P _S	Number of times	Time of transmission/us
			6	6	0；100；200；300；400；500
6	3	10；210；410
			5	6	30；130；230；330；430；530
5	2	40；340
			4	1	60
3	1	140

Finally, although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. A Modbus TCP cross-TSN joint scheduling method is characterized by comprising the following steps:

s3: and constructing a two-dimensional offline boxing problem model, namely performing problem conversion by adopting a two-dimensional offline boxing algorithm to abstract transmission requirements into two-dimensional objects, and changing a placing principle and a sequence in a boxing process by combining network transmission priority, so that a scheduling problem is optimally solved.

2. The Modbus TCP cross-TSN joint scheduling method according to claim 1, wherein in step S1, heterogeneous structures are constructedThe network scheduling model specifically comprises: defining a heterogeneous network N (L) consisting of a plurality of links L e L = { L } _TSN ,L _Mod Composition, where L ∈ L _TSN Is a TSN link, L ∈ L _Mod Is a Modbus link; a stream transmitted in a heterogeneous network N (L) is defined as S = { S = { S = } ₁ ,S ₂ ,…,S _i ,…S _n N represents the total number of streams S transmitted in the heterogeneous network N (L);

R(S)＝{ID _S ,P _S ,T _S ,B _S ,D _S } (1)

wherein, ID _S Denotes the number of stream S, P _S Indicating the priority of the stream S, D _S Representing the upper end-to-end delay limit for stream S.

3. The Modbus TCP cross-TSN joint scheduling method according to claim 2, wherein in the step S2, priority preprocessing is completed by using a scheduling preprocessing algorithm, and the method specifically comprises the following steps:

s21: performing priority mapping on the transmission requirement R (S) of the stream S;

S23: defining equal priority blocking

And high priority blocking

S24: calculating and analyzing whether an end-to-end delay upper limit D specified in the transmission requirement R (S) of the stream S is met _S If not, then

4. The Modbus TCP/TSN joint scheduling method according to claim 3, wherein in step S21, the priority mapping specifically includes: priority P for stream S _S Defining a binary function F (x, y) and mapping the calculation result to the priority P of the stream S _S ；

Where x denotes the data type of stream S, y denotes the urgency of stream S, and a and b denote the weights occupied by the two influencing factors, respectively.

5. The Modbus TCP cross-TSN joint scheduling method of claim 3, wherein in step S22, an end-to-end delay Σ d of the stream S is calculated _S The expression is:

wherein,

indicating the processing delay of the protocol stack at the transmitting end,

wherein

representing the transmission delay of a single node.

6. The Modbus TCP cross-TSN joint scheduling method according to claim 2, wherein in step S3, a two-dimensional offline binning problem model is constructed, and the method specifically comprises the following steps:

s31: the method comprises the steps that a stream S transmitted in a heterogeneous network corresponds to a two-dimensional article, and time domain resources correspond to a box;

s32: cluster period T over stream S transport _LCM And a minimum period T _GCD Converting the one-dimensional transmission process of the stream S in the time domain into a two-dimensional form, and matching with the two-dimensional offline boxing problem; wherein a cluster period T is defined _LCM Is a period T _S Defining a minimum period T _GCD Is a period T _S The greatest common divisor of (c);

s33: according to the conversion idea of step S32, the stream S is converted into a two-dimensional article having a width W _S And height H _S Period T of exactly and flow _S And a load B _S Correspondingly, expressed as:

7. the Modbus TCP cross-TSN joint scheduling method according to claim 6, wherein the step S32 specifically includes the steps of:

s321: cluster period T for transmitting a stream S on a time axis _LCM According to a minimum period T _GCD Detaching, sequentially stacking in time sequence from bottom to top, and longitudinally arranging to obtain a minimum period T _GCD The stacked objects are regarded as a box;

W _box ＝T _GCD

s323: height H of the box _box The accumulation for each minimum period of the stack is then expressed in the time domain as:

s324: in the two-dimensional time domain diagram of the box model, the travel track of the time axis is from the point (0,T) ₁ ) Initially, advancing in the positive x-axis direction; after the first minimum period T is completed _GCD I.e. the arrival point (T) _GCD ,T ₁ ) Then, the process returns to (0,T) ₁ ) Dots, then proceed in the positive y-axis direction to dot (0, T) ₂ ) Then continue to advance in the positive x-axis direction, and so on until T is completed _n Minimum period T of _GCD I.e. the arrival point (T) _GCD ,T _n ) And then, the transmission is completed.