Priority polling and dynamic time-window mechanisms in a multicycle Fieldbus

Raja, P.; Ulloa, G.

doi:10.1109/cmpeur.1993.289840

Cited by 13 publications

(2 citation statements)

References 4 publications

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“…The network ensures that the variable is transferred from the producer to all consumers . This is done by th e master which polls each variable periodically [7,8] . A polling sequence is shown in Fig .…”

Section: Basic Assumptions About the Networ Kmentioning

confidence: 99%

Analysis of polling protocols for fieldbus networks

Raja¹,

Noubir²,

Ruiz³

et al. 1993

SIGCOMM Comput. Commun. Rev.

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Roll-call polling mechanisms are considered for fieldbus networks . Based on a producer/consumer communication model, two different protocols are presented, namely the standardized FIP (Factory Instrumentation Protocol) and a modified FIP protocol that we propos e here. The modified protocol uses redundancy to eliminate local timers used by the FIP protocol . The two protocols are analyzed for efficiency, jitter and robustness . We compare the two protocol s based on implementation and analytical results . Practical aspects concerning : clock precision ; computing time ; and hard real-time constraints are also discussed . The results show that: (1) th e original FIP protocol is fractionally more efficient with respect to its execution time than th e modified one ; (2) the modifications proposed, however, reduce the jitter and improve th e robustness considerably ; (3) the slot time of the original FIP protocol has theoretical upper boun d but the modified protocol has no such limitations . . INTRODUCTIO NControl applications, such as manufacturing systems and process control, constitute an importan t class of real-time applications . Such an application is in constant interaction with an external physical process through field devices (like sensors, actuators, Programmable Logical Controllers , PLCs ). The major activity is to read values (from sensors), calculate new commands (by PLCs ) and send new commands (to actuators), Fig. 1. In general, these three steps are carried ou t periodically in a cyclic manner [2,6] . The response times of these systems are in the order of fe w milliseconds and therefore are generally classified as hard real-time systems [9] .In this paper, attention is focused on the communication support for such systems when the fiel d devices are connected by a real-time local area network . Fieldbus is the standard solution for suc h networks [1,2] . Its purpose is to replace the traditional point-to-point cabling that connect sensor s and actuators with PLCs. FIP (Factory Instrumentation Protocol) [1, 4] is a French nationa l standard for fieldbus. It has also been proposed as an international standard [12] . FIP is basically a polling protocol. A station, called master, controls accesses to the communication medium, and al l other stations connected to the network, called secondary sites, are polled by the master.Two polling mechanisms are generally known in the literature [5] . They are briefly described in th e following :Roll-call polling : The master polls a secondary site and the secondary site transfers messages an d notifies the master at the end of the transmission . Then the master polls the next secondary site i n the polling sequence.Hub polling : The master polls an initial secondary site, the secondary site transfers its messages an d passes on the control to the next site (for example by suffixing a go-ahead field to the end of it s transmission with the next secondary site address) . Thus, the intermediate transfer of control t o the master is avoided .External Environmen t ...

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Section: Basic Assumptions About the Networ Kmentioning

confidence: 99%

Analysis of polling protocols for fieldbus networks

Raja¹,

Noubir²,

Ruiz³

et al. 1993

SIGCOMM Comput. Commun. Rev.

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show abstract

“…For example, Nilsson [1] supposed the network delay to meet the characteristics of the finite state Markov chain, under the condition where the network delay is less than the sampling period, and applied the stochastic control theory to the problem of stability and optimization design of NCSs. Raja [2] proposed the bandwidth allocation scheme based on priority cycle service and dynamic time windows to improve utilization of network bandwidth, without consideration of control system QoP. Walsh [3] presented the MEF-TOD algorithm, an algorithm of dynamic network resource allocation for the time-critical information, which enables the node of maximal weighing error to transmit in prior order; however, it has no consideration of control system QoP too.…”

Section: Introductionmentioning

confidence: 99%

A synthesizing control model of networked control systems to guarantee QoP and QoS

Kang

Dai

2008

J. Control Theory Appl.

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The whole performance of the networked control system (NCSs) depends on two interaction factors, namely the quality of control performance (QoP) and quality of network service (QoS). So, to optimize the whole performance of NCSs, the problem of guaranteeing QoP and QoS plays an important role in the design of NCSs. However, up to now, little work has been done in this field. In this paper, a synthesizing control model of NCSs to guarantee QoP and QoS is proposed, and a feasible condition of optimizing whole performance of NCSs is also suggested. Finally, the simulation results show that the proposed model is effective.

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Using IA Algorithm to Improve Consistencies in Real-Time Fieldbus

Franco

Henriques

2000

IFAC Proceedings Volumes

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Priority polling and dynamic time-window mechanisms in a multicycle Fieldbus

Cited by 13 publications

References 4 publications

Analysis of polling protocols for fieldbus networks

Analysis of polling protocols for fieldbus networks

A synthesizing control model of networked control systems to guarantee QoP and QoS

Using IA Algorithm to Improve Consistencies in Real-Time Fieldbus

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