Low Power Implementation for Networked Control Industrial Applications

7/28/2019 Low Power Implementation for Networked Control Industrial Applications

1/4

A Review on Low Power Implementation for

Networked Control Industrial Applications

Ahmad Mahfouz Marzouk

ID: 800-112-783

EENG 556: Networked Control Systems

Electronics Engineering Department

School of Sciences and EngineeringThe American University in Cairo

Submitted to Dr. Ramez Daoud

Abstract With the knowledge that Power consumption is a critical

design issue in networked control systems, this review studydiscusses various issues with low power implementations of

Networked Control Systems (NCS) in industrial automation. Thenetwork protocols are considered to be the most important aspect ofthe system. Different state-of-the-art types of communication

systems, wired they are or wireless, that are used in real-timecontrol systems are introduced as found in literature.

I. INTRODUCTIONReviewing the current trends in power-aware and low

power implementation of industrial applications shows thegreat potential of wireless networks to be used to communicatethe system nodes. Beside the flexibility, reliability andportability, the implementation cost is an important factor thattilted the balance against fieldbus communication systems forthe latest industrial applications. Nevertheless, thenondeterministic and concurrent behavior of distributed controlsystems makes their design and analysis more complex than thecounter fieldbus protocols supporting real-time control.

With the focus of almost all literature studies on variousnetwork parameters other than power, such as reliability,resiliency, latency, jitter and delay, it was difficult to find adefinite, specific wired protocol or implementation which ispower driven in industrial automation. However, not onlywireless sensor and actuators Networks (WSAN) areconsidered in this review of power-aware industrial

implementations but also the state-of-the-art wired controlnetworks are studied focusing mainly on industrial Ethernet,with all its different co-existing forms and solutionsvendors;PROFINET, Ethernet Powerlink, Ethernet/IP, Modbus-TCP,etc.

II. WIRED IMPLEMENTATIONA. Industrial Ethernet Implementation

In spite of the early attempts to use Ethernet technology inthe industrial context, only recently has it attracted a lot of

attention as a support for industrial communication. Many

manufacturing companies maintain separate networks tosupport their factory floor operations and business operationsshown in Figure 1. Over the years, these networks weredeveloped to respond to the different information flows andcontrol requirements involved with manufacturing processes.The control-level network connects control and monitoringdevices, including programmable automation controllers, PC-based controllers, I/O racks, drives, and human-machineinterfaces (HMIs). This network, which has not been basedupon standard Ethernet and IP in the past, requires a router or,in most cases, a gateway to translate application-specificprotocols to Ethernet-based protocols. This translation letsinformation pass between the control network on the factoryfloor and the corporate network infrastructure, but has limited

functionality and bandwidth, and requires significant effort tokeep up to date.

Figure 1. Traditional Proprietary Fieldbus Architecture


2/4

Figure 2. Traditional Proprietary Fieldbus Architecture

Traditionally, interconnectivity between various devices onthe factory floor, e.g. sensors, actuators, HMIs, controllers, wasachieved with a variety of fieldbuses such as DeviceNet,Profibus, and Modbus. Each fieldbus has specific power, cable,and communication requirements, depending on the factoryapplication it supports. This has led to a replication of multiplenetworks in the same space and the need to have multiple setsof spares, skills, and support programs.

Moreover, there are other several advantages behind theturning to Ethernet technology as a means to interconnect fielddevices to the first level of automation in addition to the

previously mentioned major issue. To name a few of suchadvantages:

Tremendously higher speeds ( 10 Gb/s is now currentlyoffered ) than other fieldbuses networks such as thepreviously mentioned Profibus, DeviceNet, or CAN.

Cost feasibility due to the huge market for Ethernet andthe associated protocols IP, UDP, and TCP that costsof interface circuits have been drastically lowered.

Furthermore, Industrial Ethernet can unite a companysadministrative, control-level, and device-level networks to runover a single network infrastructure instead of usingarchitectures composed of multiple separate networks.

Recognizing that Ethernet is the leading networking solution,many industry organizations are porting the traditional fieldbusarchitectures to Industrial Ethernet. Simply, it applies theEthernet standards developed for data communication tomanufacturing control networks, shown in Figure 2 using IEEEstandards-based equipment, organizations can migrate all orpart of their factory operations to an Ethernet environment atthe pace they wish.

III. WIRELESS IMPLEMENTATOINSGiven the novel characterizations for modern factory

facilities with highly flexible manufacturing cells and highlydynamic processes, where clusters of fixed or moving sensors

and actuatotrs have to be controlled in limited space andconsume adequate power under the constraints of real-time andreliability. Here comes the role of wireless systems in suchdemanding industrial environments.

A cutting-edge technology that tends to be the perfectsolution for power-aware and flexible applications is WirelessSensor and Actuator Networks (WSAN). WSAN, alsoaddressed as Industrial Wireless Sensor Networks (IWSN) [9],are used to improve control system efficiency through severalfunctions that are distributed over different wireless nodes,where the wireless communication channels provide increased

flexibility, reliability and portability. In a Networked ControlSystem (NCS) allowing mobile-communicated system nodes,the sensor, controller and actuator functions are distributed andcan be assigned to other nodes according to specified criteriasuch as power consumption optimization, time constraints anddelay reduction [2]. Additional to the aforementionedadvantage of WSAN, it brings self-organization, rapiddeployment, flexibility, and inherent intelligent-processingcapability [9]. Hence, WSAN plays a vital role in creating ahighly reliable and self-healing industrial automation systemthat rapidly responds to real-time events with appropriateactions.

On the other hand, it is not an easy task to implement an

automation solution using WSAN systems; unique technicalchallenges and design principles are need to be faced in termsof hardware and software developments and systemarchitecture beside protocol design. A comprehensiveaddressing for the most important challenges and design goalsare given in table 1. It is noteworthy that WSAN demandconsiderable research to focus on overcoming the deficienciesof energy consumption of the sensor nodes through powermanagement schemes regarding resource allocation, routingand low-energy consumption. This requires various powerconservation mechanisms to be applied on the differentnetwork layers as addressed in [2] basically in order to reducethe power consumption at different levels.


3/4

TABLE I. CHALLENGES VERSUS DESIGN GOALS IN WSAN[9]

In this review, wireless network protocols are addressed asa most weighted aspect in an industrial implementation for anNCS. Nevertheless, the different design and technical aspects

toward the WSAN implementation are classified in an elegantmanner combining the most crucial issues as follows [9]:

1. Hardware development; where low-power and low-costsensor-node, with its different components including thesensor, the transceiver, the power source and theprocessor, should be adopted for the implementation.Additionally, energy-harvesting technique is an importantaspect to be considered affecting the system powerefficiency and the lifetime of the whole WSANs. Finally,the radio technologies to be used in such noisy andinterfering environment.

2. Software development; where the regularly importantaspects toward delivering a user-friendly yet reliable

system are required, starting from applicationprogramming interface level to the high-level systeminstallation and commissioning.

3. Protocol design; where the network architecture isdiscussed to reach a scalable design that is of primaryimportance in an industrial application. In addition, thedesign of an optimized cross-layer technique is also ofprimary important in such interdependent system layers.

Reaching this point, the most applied standardization related toWSANs are briefly addressed as follows.

A. Bluetooth and IEEE 802.11e:Bluetooth and IEEE 802.11e EDCA (Enhanced Distributed

Channel Access) have been discussed in literature, [1], toimplement control systems. The results show that thesetechnologies allow to fullfil with real-time constrains inindustrial applications for less than 10 nodes and sampleperiods upper than 10 ms.

B. ZigBee:ZigBee technology is a wireless networking protocol

targeted towards automation and remote control applications. Itis advantageous for its low data rate, low power consumption,low cost. ZigBee sits below Bluetooth in terms of data rate;250kbps at 2.4GHz while that of Bluetooth is 1Mbps. Zigbee is

supported by the IEEE 802.15.4 standard which providesasynchronous and synchronous (through beacons) mediaaccess. The advantage of the asynchronous MAC algorithm isthat it facilitates scalability and network auto-configuration;however, it does not fully guarantee time transmission

bounds.[4] Moreover, it supports star topology, cluster treetopology, and peer-to-peer topology that benefits industrialcontrol and monitoring; as it can provide reliability bymultipath routing.

C. WirelessHART:WirelessHART is another wireless network protocol which

consumes less power than systems supported by IEEE 802.11.It is an extension of the HART protocol and is specificallydesigned for process monitoring and control. The technologyemploys IEEE 802.15.4-based radio, frequency hopping,redundant data paths, and retry mechanisms. WirelessHARTnetworks utilize mesh networking, in which each device is able

to transmit its own data as well as relay information from otherdevices in the network [10].

D. Ultrawideband:UWB is a short-range wireless-communication

technologysending data in the form of very short periodicimpulses. The initial applications of UWB include multimediaand personal area networking. Although UWB-based industrialapplications have gained recent attention, it is not a viableapproach for communication over longer distances ormeasuring data from unsafe zone. This is simply due to thehigh peak energy of pulses. Besides, serious current challengesare occurring against this technology such as hardwaredevelopment, dealing with MAC and multipath interference,

and understanding propagation characteristics. However, theUWB is advantageous as a result of the following:

Good localization capabilities. Possibility to share previously allocated radio-

frequency bands by hiding signals under noisefloor.

Ability to transmit high data rates with low power. Good security characteristics due to the unique

mode of operation.

Ability to cope with multipath environments.


4/4

IV. CONCLUSIONIn this study, the most recent and latest industrial

implementations for power-aware Networked Control Systemsare introduced. These implementations are classified mainlyinto wired and wireless techniques. The most famous and lately

hugely used wired technique is Industrial Ethernet. Mainly itdiffers that IT-based Ethernet by its deterministic behavior toaccommodate the real-time requirements by the industrial NCSapplications.

The wireless techniques show high potential in bothresearch and industry. With the consequent advancement inresearch and development for wireless communicationprotocols and technologies, such as the Wireless Sensor andActuator Networks system, wireless implementations arereaching reliability and resilience of wired techniques. Not toforget the advancement in power reduction techniques in thewireless implementations which increase the advantage ofwireless against wired in the foreseen future.

REFERENCES

[1] Pantazis, N.A.; Vergados, D.D.; , "A survey on power control issues inwireless sensor networks,"Communications Surveys & Tutorials,

IEEE, vol.9, no.4, pp.86-107, Fourth Quarter 2007

[2] Martinez, D.; Gonzalez, A.; Blanes, F.; Aquino, R.; Simo, J.; Crespo, A.Formal Specification and Design Techniques for Wireless Sensor andActuator Networks, Sensors 2011, 11(1), 1059-1077;doi:10.3390/s110101059. [http://www.mdpi.com/1424-8220/11/1/1059/]

[3] Decotignie, J.-D.; , "Ethernet-Based Real-Time and IndustrialCommunications,"Proceedings of the IEEE, vol.93, no.6, pp.1102-1117, June 2005.

[4] Zigbee Specification. Available online: http://www.Zigbee.org (accessedon 7 October 2010).

[5] Rojas, C.; Morell, P.; , "Guidelines for Industrial Ethernet infrastructureimplementation: A control engineer's guide," Cement Industry TechnicalConference, 2010 IEEE-IAS/PCA 52nd , vol., no., pp.1-18, March 282010-April 1 2010.

[6] Schmidt, K.; Schmidt, E.; , "Distributed Real-Time Protocols forIndustrial Control Systems: Framework and Examples," Parallel andDistributed Systems, IEEE Transactions on , vol.PP, no.99, pp.1, 0

[7] Korber, H.-J.; Wattar, H.; Scholl, G.; , "Modular Wireless Real-TimeSensor/Actuator Network for Factory AutomationApplications," Industrial Informatics, IEEE Transactions on , vol.3, no.2,pp.111-119, May 2007.

[8] Decotignie, J.-D.; , "Ethernet-Based Real-Time and IndustrialCommunications," Proceedings of the IEEE , vol.93, no.6, pp.1102-1117, June 2005.

[9] Gungor, V.C.; Hancke, G.P.; , "Industrial Wireless Sensor Networks:Challenges, Design Principles, and Technical Approaches," IndustrialElectronics, IEEE Transactions on , vol.56, no.10, pp.4258-4265, Oct.2009.

[10] IML Group Plc, Wireless hart specification released, ControlEngineering Europe, vol. 8, no. 3, pp. 89, Jun./Jul. 2007

Low Power Implementation for Networked Control Industrial Applications

Documents

Transcript of Low Power Implementation for Networked Control Industrial Applications