2014 III International Congress of Engineering Mechatronics and Automation - CIIMA 2014
1
Design and implementation of a flow control based on DeviceNet 1
M.Sc William Gutiérrez Marroquín, SENA, Regional Valle, Centro de Electricidad y Automatización Industrial,
[email protected]. 2 Dr.CsEng. Mario Fernández Fernández, Universidad de Talca, Chile, Departamento de Tecnologías Industriales,
[email protected] 3 Esp. William Mantilla Arenas, SENA, Regional Valle, Centro de Electricidad y Automatización Industrial,
[email protected]
Abstract— Measurement and control of flow are definitively important in the industry, especially when they are involved in the control of continuous processes. The use of proportional valves as final control elements is very common. However, it causes a high pressure drop in the flow line. Moreover, its generally non-linear characteristics forces to operate in cases where it is required to change significantly in its operation zone, to avoid having to change the controller tuning parameters. An alternative flow control may be applied directly on the propeller pump, changing the flow by varying the pump speed. This has the advantages of not causing pressure loss in the line (resulting in a reduction of pressure requirements, occupying smaller pumps and decreasing acquisition costs and energy involved). The purpose of this article is to show the design and implementation of a flow control using as final control element (pre-actuator) an inverter speed (VSD), and comparing its performance in relation to which it has a control valve. Additionally, the VSD configuration is done through a DeviceNet network, which requires the commissioning of the network so that the controller can send the inverter reference speed at which the pump must operate. This has the advantage that the parameters of voltage and current consumption of the system can be obtained via the DeviceNet network, to compare both forms of control. The implementation is developed in an educational plant, which has instruments for measuring differential pressure flow, industrial control valves commanded by a current signal (4 to 20 mA), centrifugal pump for pumping fluid from a storage tank to the reaction vessel, commanded by an inverter speed and the controlled by a PLC. PI strategies for flow control are used, comparing the results using as final control element a proportional valve or a pump using a VSD as pre-actuator. The results allow ensuring that the system significantly improves efficiency by using VSD to flow control.
Key words— PI, Flow Control, DeviceNet, Commissioning, Speed converter.
I. INTRODUCTION To control a fluid flow it can put a variable area restriction in the conduit through which flows. This is achieved by integrating a valve in control loop. A pressure loss is produced across the system due to the control valve [1]. Another way is by varying the speed of rotation of the impeller pump, which can be done through an inverter. There are diverse applications of flow control in industrial processes, including the regulating of the amount of raw materials that go into a reactor, the controlling of the amount of heat flow in a heat exchanger, the regulating of the tank level [2]. The DeviceNet network is an open device level network that provides connections between industry devices, such as sensors, actuators, and high-level controllers as PLCs and computers devices. It is a flexible network that works with devices from multiple manufacturers, offering a wide variety of products from Rockwell Automation and thirds [3]. In this paper we study the performance of the flow control loop using as final control element a valve or a VSD, presenting a comparative study of energy consumption involved in both cases. This paper is organized as follows: In Section II refers to the plant is used. Subsequently, in Section III, the control strategies in which the final elements of control is used above are explained. The configuration parameters via the DeviceNet network details are presented in Section IV, and in Section V the results are discussed. Finally, in Section VI the conclusions drawn from this study are highlighted. II. LABORATORY PLANT FIG. 1 shows a picture of the plant with its constituent parts.
2014 III Internatiional Congresss of Engineerin ng Mechatroniccs and Automaation - CIIMA 22014
2
FIG G. 1. Didactic plan nt for remote learniing of process con ntrol.
The Laboratorry of Industriaal Communicaations of SEN NAbia) provides a learning pllant Reegional Valle (Cali, Colomb witth smart transm mitters to meaasure process variables, v conttrol vallves command ded by a 4 to 20 0 mA current. In addition, th here is a high-end PLC P (Allen Bradley, B ControlLogix seriees), hrough an analog whhich obtains alll measuring plant variables th inpput module an nd from which all actuators can c be commaand thrrough an analo og output modu ule, by implem menting a strateegy of pre-defined co ontrol. This plaatform has a caapacity of rem mote net, which allo ows it to be co onfigured in no onacccess via Intern facce from anyw where, making g it particularrly attractive for eduucational purpo oses [4]. FIG. 2 showss the piping and instrumeentation diagrram (P& &ID) related to o the portion of the used plan nt, where the lo oop floow control is implemented using u as finall control elem ment vallve, and FIG. 3 shows thee P&ID contrrol loop using g a PowerFlex variaable speed wiith DeviceNett communication eleement as pre-acctuator.
FIG G. 2. Process P&IID using LCV100 0 valve as actuatorr in the flow conttrol loopp
FIG. 3. Prrocess P&ID usinng FS100 VSD as aactuator in flow coontrol loop
In eaach of the situuations a PI coontrol is impleemented and process variables andd also the vooltage, power, and torque current instant values used by the puump are recordded. LCV100 is a S ST series ball vvalve, led by a positioning The L of the Delta D-53 series, througgh a 4-20mA A signal. As mentation technnique, it is woorking in perceentage units, implem where 00% is fully clossed and 100% is fully open vvalve. The V VSD is an Allen Bradley PowerFlex 40, 1 HP power connecttion 220 VAC C 3φ, with D DeviceNet com mmunication module . L STRATEGIE ES IMPLEMEN NTED IIII. CONTROL FIG. 2 shows the firrst configuratioon considered using a flow control valve as a ffinal control eelement. Closeed loop was tested implementing a PI contrrol strategy, varying the referencce value in stagges to values bbetween 35% aand 45%. As actuatorr is used the L LCV100 controol valve to maanipulate the TK100 tank inflow. H Here, the activaation of the SV VR100 pump is via thhe inverter from m PLC (SY1000), setting the reference to 100% too turn it on annd 0% to turn iit off. To recorrd the engine variablees and parametters (voltage, ccurrent, powerr and torque) was deeveloped a sccript in Matlaab, which excchange data throughh RSLinx OP PC between tthe two appliications was implem mented. For thee second configuration, show wn in FIG. 3, the SVR R100 drive speeed was set ass the final conttrol element. In this ssituation, the ccontrol action stablished by PI controller implem mented in the P PLC (FIC100)), is sent as a word speed referencce to the inveerter. Meanwhhile, the LCV V100 control valve iss opened to 1000% to cause thhe lower possibble restriction of presssure loss. Saame referencee and processs and pump variablee values are reecorded as in the first test ffrom Matlab apply. F IG 4 shows thee definition off the object for OPC Matlab code too exchange daata between thhe plant (via R RSLinx) and Matlab..
2014 III Internatiional Congresss of Engineerin ng Mechatroniccs and Automaation - CIIMA 22014 IV. STRU UCTURE AND D NETWORK SETTINGS S DEVIC CENET D DeviceNet is a high perforrmance and lo ow cost fieldb bus, whhich is being widely w applied in automatic process p controll. It is a communicattion protocol used u in the auttomotive indusstry c devicees for data excchange based on to interconnect control AN bus (Contro oller Area Netw work) and defiine an application CA layyer to cover a wide rangee of device profiles. p Typiical appplications inclu ude informatio on sharing, security devices and a a laarge number of o network conttrol input / outtput. FIG. 5 sho ows thee structure of th he network imp plemented in th his work. % DEFINED THROUGH COMMUN NICATION OPC te OPC Server r'); da = opcda('localhost','RSLinx Remot connect(da); %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%%%%%%%%%%%% %%%% %%%% % A GROUP IS ADDED TO OBJ JECT OPC grp = addgroup(da); % DEFINED ITE EMS IN GROUP OPC itm2 = additem(grp,'[UTALCA2]Pr rogram:MainPr rogram.FT100'); itm4 = additem(grp,'[UTALCA2]Pr rogram:MainPr rogram.TOMAMU UEST RA'); itm5 = additem(grp,'[UTA ALCA2] VALVUL LA_MANUAL'); itm7 = additem(grp,'[UTALCA2]Pr rogram:MainPr rogram.MUESTR RA') ; itm13 = additem(grp,'[UT TALCA2]PID_FL LUJO.SP'); itm15 = additem(grp,'[UT TALCA2]AM'); itm16 = additem(grp,'[UTALCA2]Pr rogram:MainPr rogram.LCV100 0'); itm17 = additem(grp,'[UT TALCA2]CORRIE ENTE_MOTOR'); itm18 = additem(grp,'[UT TALCA2]FRECUE ENCIA_MOTOR'); itm19 = additem(grp,'[UT TALCA2] VOLTA AJE_MOTOR'); itm20 = additem(grp,'[UT TALCA2]POTENC CIA_MOTOR'); itm21 = additem(grp,'[UT TALCA2]TEMPER RATURA_DRIVE'); itm22 = additem(grp,'[UT TALCA2]TORQUE E_MOTOR');
3
perform med, which alloowing to set thhe number of tthe node, the commun unication speedd and the meemory areas aavailable for mappinng VSD paraameters. In thhe FIG. 6, tthe network configuuration is displaayed.
FIG. 6. C Configuring the DeeviceNet Network
The VSD consum me a messagge that comees from the controlller, composed by two words, as follows: • Loggic Command. • Refference. Throuugh the Logicc Command woord, orders aree transmitted to the V VSD (as start, sstop and other) [5]. In thhe FIG. 7 the sstructure of thee Logic comm mand word is shown.
FIG. 4. OPC Matllab code for comm munication between n RSLinx and Mattlab.
FIG. 7.. Logic Commandd Structure
FIG. 5. Network structure s implemen nted with DeviceN Net communication n.
The VSD AC C drive PowerFlex 40 has an inserted 222 OMM-D DeviiceNet communication card d which allo ows CO joiining into a DeviceNet D netw work. Through h the application RS SNetworx the equipment com mmissioning by b the network k is
Reference worrd is defined byy the controller and sent as The R the speeed reference too the drive.
2014 III Internatiional Congresss of Engineerin ng Mechatroniccs and Automaation - CIIMA 22014
4
conditions, th the flow was ccontrolled by m manipulating the LCV100 valve. V100 valve at • Experience 2 (Exp.2): Estaablishing LCV full flow (1000%) so as too cause the leeast possible restriction too the system, the flow is controlled by manipulatingg the frequencyy of pump pow wer. In b oth experiencces, the resullting flow waas measured throughh FIT100 trannsmitter. As a control algoorithm, a PI controlller (FIC100) w was configuredd in the PLC ssystem. Prior to the eexperiences, thhe Ziegler & N Nichols rules w were used as tuning tthe control straategy for each case, resultingg the control parametters shown in TABLE 1. TABLE 1. Parameters used as tuning of PI coontrollers. Experiennce 1 Kc1 Ti1 0.5 00.025
A As shown in FIG. 8, it hass the lowest memory m word of Loocal3.O.Data [0 0] for the Logiic Command, while the high hest corrresponds to th he Speed Referrence. To register parrameters (such h as frequency or voltage pum mp) muust be defined with explicit messages. Fo or this, a speciific com mmand is useed in the conttroller by meaans of which the adddressing param meter is establisshed as followss: Class – Instaance – Attributt.
Pump Frequency [Hz]
Valve opening [%]
FIG. 9 is show wn the setting of o an explicit message m from the conntroller.
Both realized experriences consistted of manuallyy shifting the flow abbout 30% andd then changee the control tto automatic mode. IIn this momentt, we run a M Matlab program that causing five chaanges in the vaalue of the refeerence signal, bbetween 35% and 40% % (SP = [35 440 35 40 35]) w with 1min of tiime between changess, and collectting all experiiment data byy OPC. The control variables aree shown in FIG. 10 and the varying parametters of the pum mp in FIG. 11. Flow Control [%]
FIG. 8. Memory paarameters zone.
E Experience 2 Kcc2 Ti2 0.8 0.009
(a) SP Flow w Exp 1 Flow w Exp 2
40 0 30 0 0
50
100
150 Time [s] T (b)
200
250 0
300
100 0
Valv ve Exp 1 Valv ve Exp 2
50 0 0
50
100
150 Time [s] T (c)
200
250 0
300
VSD D Exp 1 VSD D Exp 2
60 0 50 0 0
50
100
150 Time [s] T
200
250 0
300
FIG. 10. P Process variables, Experiences 1 andd 2. (a) Flow Conntrol; (b) openinng valve; (c) Pumpp Frequency
FIG.9. Setting of an a explicit messagee.
V. RESULTS To verify the hypothesis h thatt the use of a VSD V to control the floow through a pipe is not only y more efficien nt to do it throu ugh a vvalve, but it is more efficientt from the enerrgy point of vieew, thee ability profited by a VSD with DeviceNet able to deliver online consumpttion parameterrs during opeeration. To sh how thiis, the two exp periments perfformed in FIG GS. 2 and 3 were w donne, with the following characcteristics. •
Experien nce 1 (Exp.1)): Fixing the VSD V to feed the P100 pu ump at 60Hz, so that it opeerates at nomiinal
In thhe FIGS. 10B annd 10C can bee seen that, for controlling flow arround the refeerence values set in Exp.1 the opening valve w was modulatedd to values below 50% while the pump was beiing supplied w with a constant frequency, to the nominal value o f 60Hz. Meannwhile, in Exp..2 an equivalennt result was achieveed by varying tthe pump frequuency in the raange of 50Hz to 55Hzz, while the vaalve remains fuully open (100% %). FIG. 10A shows tthe efficiency ssavings with thhe frequency m manipulating, not onlyy for the shortter setting timee and the quicckly reaching of the rreference valuue with zero steady-state errror obtained, but shoowing a similaar behavior foor rising and falling steps (linear behavior), coompared with non-linear reesponse type having valve (due too its quick rellease feature), to which is added a backlash efffect that causees pseudo-statiionary states (as seenn between 70s and 80s, 130s and 140s, 250ss and 260s).
2014 III International Congress of Engineering Mechatronics and Automation - CIIMA 2014 To evaluate the efficiency of the system, the pump parameters in both experiences were analyzed, due to the pump represents the main consumption of the plant (the consumption of the rest of the plant components is similar in both cases). The FIG. 11 presents a comparative description of both experiences. (a)
(b)
(c) 220
60 40
2.8
Voltage [V]
80
Current [A]
Control Action %
100
2.6
180
2.4 0
100 200 300 Time [s] (d)
200
0
100 200 300 Time [s] (e)
0
100 200 300 Time [s] (f)
0
100 200 300 Time [s]
0
-0.5
-1
0
100 200 300 Time [s]
Pump Torque [Nm]
Pump Power [kW]
Power Factor
220 0.8 0.7 0.6 0.5 0.4
0
100 200 300 Time [s]
200 180 160 140 120
FIG. 11. Pump variables, dot line: Exp 1; continuous line Exp 2. (a) control action; (b) Current; (c) Voltage; (d) Power Factor; (e) Pump power; (f) Pump Torque.
In the FIG. 11A is seen that the waveforms of the control actions are similar, each operating in the range required for the control. However, observing FIG. 11B, it can be noted that the power consumption when the pump is operated at the nominal frequency of 60Hz (Exp.1) is greater than 2.8A, while the Exp.2 varies only between 2.4A and 2.6A throughout the time of the experience. Something similar happens with the supply voltage, remaining practically constant at 220V in Exp.1 while it varies around 150V to 170V in Exp. 2 as shown in FIG. 11C. The pressure restrictions caused by the valve in the pipeline when it operates controlling the flow cause the pump works to a greater effort, which is reflected in the value of the power factor, which varies between 0 and -0.8 (most of the time between 0 and -0.5) for Exp.1, in relation to that which results for Exp. 2 which varies between -0.6 and -0.95, as shown in FIG. 11D. Similarly, the lower restriction of pressure in the line for the Exp.2 commits the pump with a variable torque (140Nm to 170Nm), but lower than the Exp.1, which is approximately constant around at 210Nm, as seen in FIG. 11F. Finally, all these results translate into lower power consumption in Exp.2, ranging between 0,5kW to 0,6kW throughout this experience, while it remained almost constant over 0,8kW all time in Exp.1, as shown in FIG. 11E. In order to have an objective measure of efficiency, the energy consumed by the pump in both experiences was determined by integrating the power supplied during the experimentation time. The end result was 41.1 kWh in Exp.1 and 26.9 kWh in Exp.2. Last experience represents an energy saving of about 34.5% about the first. VI. CONCLUSIONS This article presented an experimental development that
5
allowed determining the effective energy savings achieved by performing flow control using as final control element a frequency inverter to a control valve, with an estimated savings of 35% (in this case) when using the VDS. In addition, the dynamic behavior of the controlled system also showed better performance in this case, in terms of response time and steady-state error. The advantage presented by using a DeviceNet fieldbus disposing the motor parameters and effectively monitoring of the energy consumed in the system, in addition to the classical resources to diagnose a malfunction in the equipment and the maintenance schedule is highlighted performed. It should be noted that, despite the drastic reduction of energy and better control can be achieved with VDS, it is not always possible to replace a valve with a frequency inverter around hydraulic circuit, due to there are processes with fluids in the gas phase that hinder the use of pumps as final element of control and critical processes in which redundancy is required in the drive, which would increase the cost of installation. REFERENCES [1]
[2]
[3]
[4]
[5]
M. Atmanand, " A Novel Method of Using a Control Valve for Measurement and Control of Flow," ieee transactions on instrumentation and measurement, vol. 48, no. 6, december 1999. R. Ibrahim. Development and Implementation of Fuzzy Logic Controller for Flow Control Application. Electrical and Electronic Engineering Department, Universiti Teknologi PETRONAS. 2010. T. Bo, "DeviceNet Fielbus and its application in remote monitoring and fault diagnosis system for main drive system of rolling mill. 978-1-4244-3531-9/08/$25.00©2008 IEEE C. Victoria, W. Mantilla, and G. W., "Diseño e implementación de una planta didáctica para la Formación Remota en Control de Procesos," SENA, Regional Valle del Cauca. C.E.A.I.2005. “PowerFlex Communications DeviceNet Adapter 22-COMM-D User Manual”, Rockwell International Corporation, January 2003.
