CN103873387A - Industrial Ethernet-oriented deterministic communication scheduling method - Google Patents

Abstract

The invention discloses an industrial Ethernet-oriented deterministic communication scheduling method, and belongs to the technical field of industrial Ethernet data communication. In the method, a deterministic scheduling method based on dynamic priority and a link time-delay matrix is designed on the basis of realizing a communication scheduling entity according to the application requirement of industrial real-time Ethernet. By adopting the communication scheduling method provided by the invention, the problem of infinite waiting of low-priority non-periodical messages in the industrial Ethernet is solved, the timing accuracy and scheduling accuracy are increased, and the overall managing quality and efficiency of networks are improved greatly.

Description

A kind of certainty client/server adaptation scheme towards Industrial Ethernet

Technical field

The invention belongs to Industrial Ethernet data communication technology field, relate to a kind of certainty client/server adaptation scheme towards Industrial Ethernet.

Background technology

Traditional commercial Ethernet (being IEEE802.3 standard) has the advantage such as opening, aboundresources, compatible good and integrated convenience, but also have that reliability is not high, the defect such as anti-interference and intrinsic safety deficiency, cannot directly apply to industrial control field.Industrial Ethernet has increased communications dispatching management entity and the TDMA transmit mechanism of staggering the time on the basis of commercial Ethernet, avoided data collision problem, has met the demand of industry spot high real-time, high reliability.

At present, still there are some problems in the communication scheduling technology of Industrial Ethernet, and such as aperiodic, the random transmit mechanism of message can cause communication delay to change, and then influence time synchronization accuracy and deterministic communication scheduling precision, even may cause data collision; In addition, aperiodic, message adopted static priority to measure, and low priority message may be postponed without the time limit, thereby caused overflowing of node buffering area.Therefore,, for the application demand of Industrial Ethernet, design is a kind of rationally, deterministic communication scheduling mechanism is necessary efficiently.

Summary of the invention

In view of this, the object of the present invention is to provide a kind of certainty client/server adaptation scheme towards Industrial Ethernet, the method is realizing on the basis of communication scheduling entity, adopt based on dynamic priority and chain-circuit time delay matrix, can effectively avoid low priority message to postpone for a long time, improve the scheduling precision of the communication resource.

In Industrial Ethernet, there are two kinds of messages: one is cycle message, as the data of transducer circle collection; Another kind is message aperiodic, as alarm and administrative message.Accordingly, Industrial Ethernet also will be divided into message transmissions stage in cycle and message transmissions stage aperiodic the time, and these two stages form a grand cycle.Aperiodicity message carrys out the access control power of competition bus by message priority and IP address.Because application is depended in IP address, Industrial Ethernet can only realize stable, communication scheduling fast and accurately by improving the priority of message aperiodic.Dynamic priority technology is for message aperiodic with randomness, and it is to have added element of time on the basis of static priority, message stand-by period aperiodic longer, its priority is higher.Cycle message transmitting time determines, its priority is common also the highest, therefore without the dynamic priority of adjustment cycle message.

Chain-circuit time delay Matrix Technology is mainly for cycle message, the chain-circuit time delay of its computing cycle message, and dispatch Industrial Ethernet node and send in advance to offset communication delay, improve scheduling precision.The byte count sizes of cycle message is fixed, and the skew of time in each cycle sending be identical, and this makes the communication delay of each node cycle message of system basic identical.For message aperiodic, its transmitting time can not be fixed, and in the time that system need to be preengage transmitting time, also can use the sending metrix based on chain-circuit time delay.

Timer is the basis that Industrial Ethernet is carried out scheduling of resource, timing management.Timer chain meter based on time difference becomes simply, fast management and the scheduling to timer.In timer chain meter, insert a timer node and can realize the setting of timer, can end a timer operation and delete a node.

Technical scheme provided by the invention is as follows:

Towards a certainty client/server adaptation scheme for Industrial Ethernet, the method, on the basis of static priority, increases element of time, forms dynamic priority strategy; Described priority policy specifically comprises the following steps:

1) by aperiodic data message according to priority classify, put into respectively the queue of corresponding priority;

2) message starts to start timer timing after packing queue into, if this message can send successfully at the appointed time, writes down adjustment factor K now; Otherwise along with the increase K value of stand-by period can constantly increase, until can successfully send;

3) time of wait is longer take the grand cycle as base unit the average latency of similar message in this queue, and in queue, position is just more by queue heads, and the priority in this queue is higher;

4) when entering aperiodic when message transmission phase, the priority calculating according to utilization sends, if IP address is identical, selects the little preferential transmission in address.If compete unsuccessfully, adopt method above to continue to adjust priority, the transmission of preparing next round.

Further, in described dispatching method, increase chain-circuit time delay matrix, thereby improved the scheduling precision of Industrial Ethernet.

Further, increasing chain-circuit time delay matrix specifically comprises the following steps:

A) calculate the communication delay Δ T between every two nodes, comprise transmission processing time delay t ₁, queuing delay t ₂, propagation delay time t ₃with reception & disposal time delay t ₄;

B) by the transmitting time T of this sending node _sendΔ T in advance, the transmitting time after adjusting is T _adjust=T _send-Δ T;

C) the communication delay matrix of whole Industrial Ethernet is $\left(\begin{array}{c}{T}_{11\mathrm{send}}-\mathrm{\Δ}{T}_{11,......,}{T}_{1\mathrm{nsend}}-\mathrm{\Δ}{T}_{1n}\\ T_{21\mathrm{send}}-\mathrm{\Δ}{T}_{21,......,}{T}_{2\mathrm{nsend}}-\mathrm{\Δ}{T}_{2n}\\ ...............................................\\ T_{n1\mathrm{send}}-\mathrm{\Δ}{T}_{n1,......,}{T}_{\mathrm{nnsend}}-\mathrm{\Δ}{T}_{\mathrm{nn}}\end{array}\right).$

Further, described dispatching method also provides a kind of timer chain meter based on time difference, for reducing processor expense, improves systematic function.

Further, the described timer chain meter based on time difference is specially:

The head of A, timer chain meter points to the timing of grand cycle relative displacement minimum all the time;

In B, timer chain meter, each timing value is actually the summation of several time values above;

In C, timer chain meter, above timing event, can not be out of order always prior to generation below.

Beneficial effect of the present invention is: client/server adaptation scheme provided by the invention, both solved the unlimited problem of waiting for of low priority message aperiodic in Industrial Ethernet, also improve timing accuracy and scheduling precision, promoted greatly holistic management quality and the efficiency of network.

Accompanying drawing explanation

In order to make object of the present invention, technical scheme and beneficial effect clearer, the invention provides following accompanying drawing and describe:

Fig. 1 is CSME communication scheduling overall construction drawing;

Fig. 2 is CSME state machine flow chart diagram;

Fig. 3 is the state diagram of CSME scheduling timing;

Fig. 4 is the timer chain meter based on time difference;

Fig. 5 is Industrial Ethernet communication delay.

Embodiment

Below in conjunction with accompanying drawing, the preferred embodiments of the present invention are described in detail.

Communications dispatching management entity (the Communication Scheduling Management Entity of Industrial Ethernet, CSME) both support the communication scheduling mode based on CSMA/CD free competition, also supported the certainty communication scheduling mode sending based on TDMA timesharing.Towards the certainty client/server adaptation scheme of Industrial Ethernet, its general frame as shown in Figure 1.For each part in this figure as shown in Table 1.

Table one

CSME entity has one of four states: bypass condition (Standby), ready state (Ready), cycle data transmission phase (PeriodicDataSending) and data transmission phase aperiodic (NonPeriodicDataSending).The implication of each state representation is as follows:

(1) bypass condition: represent that this equipment is in bus contention state freely, message is not dispatched, and easily causes data collision.Under this state, cannot guarantee the certainty of data communication.

(2) ready state: indication equipment has been carried out the preparation of communication scheduling.Under this state, equipment timing tracking accuracy reaches requirement, and communication scheduling desired parameters has also completed configuration.

(3) cycle data transmission phase: when current time arrives cycle data information delivery time, node just can be transformed into this state from bypass condition and send the periodically packets such as IO data.Send after all cycle messages, can immediately following along with send one aperiodic message assert packet, to the highest level of each node report self message aperiodic on network.

(4) aperiodic data transmission phase: after the message stage in cycle, be exactly message stage aperiodic.Precedence information aperiodic that its utilization message stage in cycle in earlier stage provides, elects a limit priority to send.If sending node also has relevant information, its sends aperiodic when message so, still needs to send this node remaining aperiodic of message.

As shown in Figure 2, detailed process is as follows for the communication scheduling program circuit of CSME:

After device power, first can check system relevant parameter, if find there is no corresponding configuration schedule information, equipment can enter bypass condition.Otherwise, when configuration is good and relevant relevant parameter reaches requirement (as timing tracking accuracy), will automatically enter bypass condition.Now CSME can start calculation of parameter correlation time, enters cycle data transmission state or data transmission aperiodic state with deciding, and computing formula is shown in equation (1).

T _de＝T _c%T (1)

In above formula, T _dethe bias of local current time to grand cycle T initial time, T _cit is current system time.If T _deequal default cycle message transmitting time bias, will enter cycle message transmission phase.

CSME definition status as shown in Figure 3.

While entering CSME for the first time, if T _debe less than the time T that local node current period message sends _pi, start so one and be spaced apart Δ T _ptimer, its expression:

ΔT _p＝T _pi-T _de (T _pi＞T _de) (2)

As long as Δ T _p> 0, just can enter cycle message transmission phase; If Δ T _p< 0, upgrades Δ T _pfor:

ΔT _p＝(T+T _pi-T _de)%T (3)

The design of deterministic communication scheduling strategy:

On the basis of original static priority scheduling strategy, be used for adjusting the priority of aperiodicity message using the time as one of them key element, avoid occurring the unlimited problem of waiting for of low priority message aperiodic.Message stand-by period aperiodic longer, its priority can be higher, so just solved the unlimited Holding Problem of low priority message aperiodic in Industrial Ethernet.

Improved dynamic priority scheduling strategy is as follows:

A) by aperiodic data message according to priority classify, put into respectively the queue of corresponding priority.Suppose that message priority has n class: PQ ₁, PQ ₂..., PQ _n, queue priority initial value is NPri ₁=1, NPri ₂=2 ..., NPri _n=n.For message aperiodic, NPri ₁the=1st, limit priority, priority 0 is kept for cycle message.

B) message starts to start timer timing after packing queue into, if this message can send successfully at the appointed time, writes down adjustment factor K now; Otherwise along with the increase K value of stand-by period can constantly increase, until can successfully send.The formula that priority dynamically updates is as follows:

$\left\{\begin{array}{c}P{Q}_1:N{\mathrm{Pri}}_1=\mathrm{NPr}{i}_1-K_1\\ P{Q}_2:\mathrm{NPr}{i}_2=\mathrm{NPr}{i}_2-K_2\\ .\\ .\\ .\\ P{Q}_n:\mathrm{NPr}{i}_n=\mathrm{NPr}{i}_n-K_n\end{array}\right.---\left(4\right)$

K in above formula _ndepend on stage aperiodic stand-by period ti, i.e. K _n=f (t1, t2 ... .., tn); NPri _nthe initial priority that our team lines up a message.

C) step can complete the adjustment of different priorities queue messages above, but is also to arrange accordingly between same one-level priority.The average latency of similar message in this queue, the time of wait was longer take the grand cycle as base unit, and in queue, position is just more by queue heads, and the priority in this queue is higher.

D) aperiodic, message sent.When entering aperiodic when message transmission phase, the priority calculating according to utilization sends, if IP address is identical, selects the little preferential transmission in address.If compete unsuccessfully, adopt method above to continue to adjust priority, the transmission of preparing next round.

Timer chain meter design:

In Industrial Ethernet system, it is very important that timer chain meter seems, it is the basis of the timing management of scheduling.In the case of the frequency and time deviation adjustment of timing, design a kind of two-way timer chained list based on time difference, to carry out more effectively timer design, as shown in Figure 4.Lefttime value in this figure, need to sort according to time difference.Time difference is to start to calculate with the starting point in grand cycle, and scale unit is the time granularity unit of hardware timer, is not the beat in routine operation system.

In the timing chained list of this difference, should be noted that following key element: the head of (1) timer chain meter points to the timing of grand cycle relative displacement minimum all the time; (2) in chained list, each timing value is actually the summation of several time values above; (3) in chained list, above timing event, can not be out of order always prior to generation below.

The design of the fine-grained timing chained list by differential type, has improved the precision of timing, has also avoided the chaotic problem of timing simultaneously, and each event has strict sequencing.

Scheduling based on chain-circuit time delay matrix improves design:

Because the communication delay of every two nodes in Industrial Ethernet is not identical, communication scheduling precision also can be subject to the impact of communication delay, even has influence on the order of scheduling.Therefore, consider the delay problem of each inter-node communication, will communication scheduling be produced to important impact.

For the transmission of cycle message, because the byte count sizes of message is fixed, and the skew of the time sending in each grand cycle is identical, so it is little that the sending metrix relevant parameter of each node cycle message of system based on time delay changes, the sending metrix algorithm based on time delay is mainly used in the transmission of phase of the cycles message.For message aperiodic, its transmitting time can not be fixed, and in the time that system need to be preengage transmitting time, also can use the sending metrix based on chain-circuit time delay.

End to end communication time delay in Industrial Ethernet is by transmission processing time delay t ₁, queuing delay t ₂, propagation delay time t ₃with reception & disposal time delay t ₄composition, is shown in Fig. 5.T in the deviation of considering timing tracking accuracy _ptpsituation under, total delay time when two node communications is Δ T:

ΔT＝t ₁+t ₂+t ₃+t ₄+T _ptp (5)

For offsetting communication delay, the time that node sends message need shift to an earlier date, and actual transmitting time adjustment is as follows:

T _adjust＝T _send-ΔT （6）

In the time there is n node in Industrial Ethernet, i node sends message and is adjusted into T to the time between j node _ijadjust=T _ijsend-Δ T _ij, communication delay matrix is so:

$\left(\begin{array}{c}{T}_{11\mathrm{send}}-\mathrm{\&Delta;}{T}_{11,......,}{T}_{1\mathrm{nsend}}-\mathrm{\&Delta;}{T}_{1n}\\ T_{21\mathrm{send}}-\mathrm{\&Delta;}{T}_{21,......,}{T}_{2\mathrm{nsend}}-\mathrm{\&Delta;}{T}_{2n}\\ ...............................................\\ T_{n1\mathrm{send}}-\mathrm{\&Delta;}{T}_{n1,......,}{T}_{\mathrm{nnsend}}-\mathrm{\&Delta;}{T}_{\mathrm{nn}}\end{array}\right)---\left(7\right)$

After the synchronization accuracy of Industrial Ethernet is stablized, the deviation T of timing tracking accuracy _ptpto be far smaller than the communication delay Δ T of message, if its value is crossed conference, communication scheduling is produced to larger impact.

Finally explanation is, above preferred embodiment is only unrestricted in order to technical scheme of the present invention to be described, although the present invention is described in detail by above preferred embodiment, but those skilled in the art are to be understood that, can make various changes to it in the form and details, and not depart from the claims in the present invention book limited range.

Claims (5)

1. towards a certainty client/server adaptation scheme for Industrial Ethernet, it is characterized in that: on the basis of static priority, increase element of time, form dynamic priority strategy; Described priority policy specifically comprises the following steps:

1) by aperiodic data message according to priority classify, put into respectively the queue of corresponding priority;

2) message starts to start timer timing after packing queue into, if this message can send successfully at the appointed time, writes down adjustment factor K now; Otherwise along with the increase K value of stand-by period can constantly increase, until can successfully send;

3) time of wait is longer take the grand cycle as base unit the average latency of similar message in this queue, and in queue, position is just more by queue heads, and the priority in this queue is higher;

4) when entering aperiodic when message transmission phase, the priority calculating according to utilization sends, if IP address is identical, select the little preferential transmission in address, if compete unsuccessfully, adopt method above to continue to adjust priority, the transmission of preparing next round.

2. a kind of certainty client/server adaptation scheme towards Industrial Ethernet according to claim 1, is characterized in that: in described dispatching method, increase chain-circuit time delay matrix, improve the scheduling precision of Industrial Ethernet.

3. a kind of certainty client/server adaptation scheme towards Industrial Ethernet according to claim 2, is characterized in that: increase chain-circuit time delay matrix and specifically comprise the following steps:

A) calculate the communication delay Δ T between every two nodes, comprise transmission processing time delay t ₁, queuing delay t ₂, propagation delay time t ₃with reception & disposal time delay t ₄;

B) by the transmitting time T of this sending node _sendΔ T in advance, the transmitting time after adjusting is T _adjust=T _send-Δ T;

C) the communication delay matrix of whole Industrial Ethernet is $\left(\begin{array}{c}{T}_{11\mathrm{send}}-\mathrm{\&Delta;}{T}_{11,......,}{T}_{1\mathrm{nsend}}-\mathrm{\&Delta;}{T}_{1n}\\ T_{21\mathrm{send}}-\mathrm{\&Delta;}{T}_{21,......,}{T}_{2\mathrm{nsend}}-\mathrm{\&Delta;}{T}_{2n}\\ ...............................................\\ T_{n1\mathrm{send}}-\mathrm{\&Delta;}{T}_{n1,......,}{T}_{\mathrm{nnsend}}-\mathrm{\&Delta;}{T}_{\mathrm{nn}}\end{array}\right).$

4. a kind of certainty client/server adaptation scheme towards Industrial Ethernet according to claim 1, is characterized in that: described dispatching method also provides a kind of timer chain meter based on time difference, for reducing processor expense, improves systematic function.

5. a kind of certainty client/server adaptation scheme towards Industrial Ethernet according to claim 4, is characterized in that: the described timer chain meter based on time difference is specially:

The head of A, timer chain meter points to the timing of grand cycle relative displacement minimum all the time;

In B, timer chain meter, each timing value is actually the summation of several time values above;

In C, timer chain meter, above timing event, can not be out of order always prior to generation below.

Images