COUPLED TANKS GENERATION II RIG LABORATORY USER GUIDE
Contents
1. y 18 728 77 1x 365 231 asaaalevelSensor 1 evel Sensor 2 Linear Level Sensor 1 TTE 0014 0016 0018 0020 0022 0004 0 006 0 008 0010 0 012 0 000 0 002 Sensor Output A Coupled Tanks Generation 2 Rig 2 Flow Rate L min vs Valve Position 74 Linear Valve 1 0 075 1 168 Flow Rate L min University of Technology Sydney 2012 Page 9 Coupled Tanks Generation 11 Laboratory User Guide Version 1 4 4 Rig Control Software After clicking the launch button you should be presented with the rig control software This is a LabVIEW application that allows you to control the valve position inlet flow rate observe the inlet inter tank and outlet flow rates and implement a PID controller for level control of the secondary tank UNIVERSITY OF Coupled Tanks Setpoint Manual PID n rr Perr Purreprerrrprurrrypurrerprrery 10 20 30 40 50 60 70 80 90 100 60 00 Level mim Time 5 Flow 1 Flow L min Time 5 Connected Loggedin Status Login OK Figure 2 Rig Control Software with the system operating in Open Loop Mode University of Technology Sydney O 2012 Page 10 Coupled Tanks Generation 11 Laboratory User Guide Version 1 4 4 1 Data Display The rig contr2. ie 16 5 4 Gleanng Data PIONS ELLE 16 9 5 Downloading Saved ia ea ag eoe Eo eoe ette duties edes 17 551 D ring a Rig eco REESE 17 552 Akera Rig SCSSIOM ec sesanan e aa e EA 17 FAQS TrOupIeShOOUn O a ee E EE 18 6 1 Hardware TIAN AOS a LI PI 18 6 1 1 Inlet Flow Rate Pump Continuously On Valve Minimum 18 6 1 2 Outlet Flow Meter amp Low Water 18 e E EN o huoc NR EE 19 NN CLER GU ao elici RENE 20 6 1 3 Magnetic Float Bobbing amp uiia Renee teet re len c lesus ted odia 21 6 2 eite nie PE ETE E m 22 6 3 ETE E DSL 22 Revision History 15 02 2012 Draft Created NE I 07 03 2012 Draft Release Doe 08 03 2012 Initial Release University of Technology Sydney O 2012 Page 1 Coupled Tanks Generation Il Laboratory User Guide Version 1 4 1 Introduction 1 1 Remote Laboratories Remote laboratories enable students to access physical laboratory apparatus through the internet providing a supplement to their studies and existing hands on experience Students carry out experiments using real equipment but with much greater flexibility since ac
3. Sess Coupled Tanks 1 Youhavechosentoopen fo a VideoFormats x 11110 D NM 20110812 163753 txt which is Text Document from http remotelabs eng uts edu au r What should Firefox do with this file 2 C Open with Notepad default ra EE E Do this automatically for files like this from now Le After clicking the text file title a browser specific download window should appear be sure to click Save File or similar in this window to save the file in an appropriate location on your computer 5 5 2 After a Rig Session If you have completed a rig session previously and saved data you are able to retrieve the saved files by clicking the Data Files heading on the UTS Remote Labs website La labVehare Legend Rig Selection Activate Access P active Coupled Tanks FPGA Hydro inclined Plane Loaded Beam Inactiv gt able Locke Rig Types Free gt 2 Tanks Specific Rigs Coupled Tanks 1 A list of previously saved data files should appear to download amp save the file to your computer click the text file title e g 20110812 163753 txt Partnered with mmm ig s REMOTELABS iab sh 2 snare 20110812_163753 b t s hich is a Text t Rig Administration Rig Selection Existing Reservations Reports Data Files from http remotelabs eng uts edu au What should Firefox
4. rambtelabs Coupled Tanks ESI Setpoint Manual PID a a a a n a a 0 10 20 30 40 50 60 70 80 90 100 Valve Level mim on MEET h 160 180 200 220 240 260 275 Time 8 Flow 1 Flow 2 Flow 3 A E z 200 220 240 260 275 Time 5 Connected Loggedin Status Login OK University of Technology Sydney 2012 Page 15 Coupled Tanks Generation 11 Laboratory User Guide Version 1 4 5 2 Saving Data PID Mode When the rig is operating in PID mode you can choose to save data in an automated fashion so that you do not have any unwanted data and or so you don t miss critical timing information system response time etc To do this click the checkbox next to the Auto Save label Data will begin to be saved when PID control is enabled Data will stop being saved as soon as PID control is disabled Alternatively you can still use the manual start and stop save buttons however note that they will be disabled when Auto Save is active g UNIVERSITY OF Manual PID AF Dlelabs Coupled Tanks TECHNOLOGY SYDNEY Setpoint mim Levelt Level2 Setpoint Manual PID Enable Setpoint mm 400 Kp a 4 5 6 1 1 Li Time m 1 Flow 2 Flow 3 1 6 Lim E 0 0 Level mm 38 63 30 19 4576 RPM 2 5 Lim z
5. N 1 2 3 Time s Connected Logged In Status Login OK Clear Plot 5 3 Saved Data Format Data is saved to a tab delimited text txt file at 0 1 second intervals The data is divided up into columns with the column order being Setpoint Valve Tank 1 Level Tank 2 Level Flow 1 Flow 2 Flow 3 mm L min L min L min RPM Time s Kp Ki 5 4 Clearing Data Plots Plots of data recorded in the rig control software can be cleared at any time by clicking the Clear Plot button This will clear all plots and reset the time counter back to zero meaning that you can repeat an experiment or mark times at different points in the experiment University of Technology Sydney O 2012 Page 16 Coupled Tanks Generation Il Laboratory User Guide Version 1 4 5 5 Downloading Saved Data As noted any saved exported data is saved to a tab delimited text txt file This these file s can be retrieved during or after the rig session Please follow the processes outlined below for each scenario 5 5 1 During a Rig Session If you wish to download your data during a rig session go to the UTS Remote Labs website window you used to launch the rig control software On this page there will be a Session Files heading with a list of all saved text files Click the text file title e g 20110812 163753 1 1 to download amp save the file to your computer
6. UNIVERSITY OF TECHNOLOGY SYDNEY COUPLED TANKS GENERATION II RIG LABORATORY USER GUIDE VERSION 1 4 Partnered with WT IS tel bs University of Technology Sydney 2012 Coupled Tanks Generation Il Laboratory User Guide Version 1 4 Table of Contents MOAGI ec ecce CRT 2 1 1 Remote Laboratories cccccccccccsssseceeecaeeeeeececaaueceeecaeuseceeeeeeeeceeessauseceeessaaeceesssaaeeeessaaeeeeesssaneeeees 2 1 2 Coupled Tanks Generation Il The Rig Apparatus cccccccseeeeeeeeeseeseeeesseeeeeeeseeeaeeeseseaaeeeeeesaaees 3 2 SAIGSSPSCIICALION C Tm 4 2 1 4 2 2 M 4 2 3 o M 4 2 4 T 4 2 5 ROW Meters tari odisse a ara E os ru EE 5 2 6 Se die lb cUm 5 2 7 Inter Tank Coupling Valves sess 6 2 8 Level Sensors with Magnetic Floats ccccccececcceccseeeeeeeeseeeeeeeeseeeeeceeesseeeeeeeesseaeeeeeesaaeeeeesssageeeeeeeas 6 2 9 Real Time Controller ccccccccccccssscceceeseceeceeeceeceeeceeseeueceeseaceeseeaeeessuaec
7. Il The Rig Apparatus The Coupled Tanks Generation 11 Rig was designed to allow students to acquire data from a physical dynamic system in order to develop a simplified mathematical model of the underlying dynamics Once the mathematical models have been developed students are able to design a control system using a P PD or PID controller and analyse the performance of the controller in maintaining the water level in one of the two tanks The rigs emulate a process engineering scenario whereby it may be critical to maintain a specific fluid level in a tank with single or multiple input s and output s acting upon the system allowing students to characterise the behaviour of such systems Each Coupled Tanks Generation 11 Rig consists of the following main components e 1xFrame e 2x Tanks 1 x Primary Tank 1 x Secondary Tank e 1 Reservoir 2x Pumps e Flow Meters 2x Inlet Flow Meters 2x Outlet Flow Meters 2x Inter Tank Flow Meters e 2x Control Valves e 2x Inter Tank Coupling Valves e 2x Level Sensors with Magnetic Floats Additionally each Coupled Tanks Generation Il Rig is monitored by a web camera so as to provide real time video of the system The entire suite of Rigs is controlled by a Real Time I O controller which enables data acquisition and control of the components within each Rig The control interface is written in LabVIEW Level Sensors with 1 1 Flow Meters ani
8. Plot Above The system undertaking PID control for a setpoint of 125 mm Note the accuracy achieved 4 3 Switching Between Control Modes The user can switch between control modes at any time If you switch from Open Loop to Closed Loop the current level in Tank 2 will be used as the setpoint If you switch from Closed Loop to Open Loop the current valve position will be used as the desired valve position Note that in PID mode the PID control will not operate until you click the enable button so that it turns green If the button is not enabled the valve will be set to 0 and consequently the tanks will drain to their minimum operating level University of Technology Sydney 2012 Page 14 Coupled Tanks Generation 11 Laboratory User Guide Version 1 4 5 Rig Data Acquisition Users are able to save sensor data for water levels flow rates and valve position for later analysis in programs like Microsoft Excel or MATLAB Please be aware of the various acquisition procedures depending on which mode you are operating the Rig in 5 1 Saving Data Manual Mode In manual mode sensor data can be saved whilst your session and the rig control software is active by clicking the Start Save button Data will be recorded and saved to a tab delimited text txt file at 0 1 second intervals When you have completed your experiment or recorded the appropriate data be sure to click the Stop Save button UNIVERSITY OF
9. position with increments of 1 from the current position by pressing the buttons next to the input box Manual pip Valve purrggpraagaggpgrgggggrrggggrg gpr2ggp pyrggrgggrggggroggggrtraga 10 20 30 40 50 60 70 80 90 100 60 00 Note The inlet flow rate is always non zero this is by design See section 6 1 1for more information 4 1 2 Open Loop States By setting a constant inlet flow rate the tanks will eventually reach one of two states The first is steady state whereby the inlet flow rate inter tank flow rate and outlet flow rates are matched with the system balancing out at a specific level for each tank In these scenarios the response of the system can be measured and included in dynamic models The second is that of overflow whereby the inlet flow rate is set too high and the system cannot balance itself see 6 1 Hardware Limitations for further explanation as a result the level in Tank 1 reaches a maximum and excess water goes into the tank overflow outlet In this case the response of the system cannot be measured qd UNIVERSITY OF rembtelabs Coupled Tanks TECHNOLOGY SYDNEY Level 1 Level 2 Setpoint Manual N 0 10 20 30 40 50 60 70 80 90 100 Level mm 23 00 a 100 120 140 160 180 200 220 240 260 275 2 7 Lim Time s Flow 1 Flow 2 Flow 3 70 10 7 4578 RPM 2 7 Lim Flow L min 0 70 80 100 120 140 160 180 200 220 Time s Conn
10. s Current Input Module 2 10 More Information A specification pack containing more information on the hardware used will be released at a later date as a downloadable archive zip file located on the session page for each rig University of Technology Sydney 2012 Page 7 Coupled Tanks Generation Il Laboratory User Guide Version 1 4 3 Calibration Data 3 1 Rig 1 Coupled Tanks Generation 2 Rig 1 Level mm vs Sensor Output A y 18 814 154x 369 899 R 1 000 m i y 18 746 968 368 557 2 1 000 Sensor 1 eea a Level Sensor 2 Linear Level Sensor 1 Linear Level Sensor 2 0 008 0 010 0012 0014 0016 0018 0020 0022 Sensor 0 000 0 002 0 004 0 006 Coupled Tanks Generation 2 Rig 1 Flow Rate L min vs Valve Position 95 aa aaa ghe 1 Linear Valve 1 y 0 073x 0 902 R 0997 Flow Rate L min 10 University of Technology Sydney 2012 Page 8 Coupled Tanks Generation 11 Laboratory User Guide Version 1 4 3 2 Rig 2 Coupled Tanks Generation 2 Rig 2 Level mm vs Sensor Output A pf po pa eg e n e y 18 782 800x 365 020 R 1 000
11. 0 units These are in line impeller type units that output a pulse as the impeller revolves in the fluid flow They do this by shining an infra red beam perpendicular to the axis of rotation of the impeller through to a sensor creating what is known as a photo interrupter As the impeller spins it interrupts the beam creating a pulse in the output voltage The on board circuitry has been designed such that this output voltage is a square wave The manufacturer provides a typical K factor for calibration that states how many pulses equate to a given flow rate The units are equipped with G3 e BSPP male threaded connectors and have an internal diameter of approximately 10mm opecifications are given below Flow Meter Specifications Pressure Drop 1 mH O 15 L min 752 pulses per Litre Typical Accuracy 2 Typical Output Signal 5V DC Square Wave G3 8 BSPP Male Threaded Inlet amp Outlet 2 6 Control Valves The control valves are a hybrid unit consisting of a Hass Manufacturing EPV 375B Electronic Proportional Valve and a Leadshine DM422C Digital Stepper Motor Controller The EPV 375B is a brass bodied in line globe valve with 72 NPT female threaded inlet amp outlet The valve is actuated by a Moons 56185 050 stepper motor connected to the valve stem The ND556 is a high performance stepper motor controller using pure sinusoidal current control and allows a variety of settings such as motor current and micro step res
12. a Control Valves Inter Tank Coupling Valves f Tank1 CELES Reservoir Figure 1 Coupled Tanks Generation II Rig University of Technology Sydney 2012 Page 3 Coupled Tanks Generation Il Laboratory User Guide Version 1 4 2 Rig Specifications 2 1 Frame The rig frame is made of MayTec Aluminium Extrusion with a 40mm profile The frame has a 6 mm thick aluminium base plate to support the reservoir and the tanks An additional circular cut out allows for access to the reservoir drain plug during system maintenance The back plate is made from 6 mm thick aluminium and has been CNC machined with numerous chamfered through holes for component wiring 2 2 Tanks The tanks are made of a mixture of 6mm and 3mm acrylic Each tank has a recess for the level sensors and a stepped outlet so as to compensate for the dead zone of each sensor The tank also has an internal overflow outlet to ensure that the water level does not exceed the design allowance of 295 mm 2 5mm The tanks have a capacity of approximately 3 800 cc 3 8 L each 2 3 Heservoir The reservoir acts as a common water supply for the system supplying both pumps and has a capacity of approximately 17 500 cc 17 5 L The reservoir has been designed such that even with both tanks operating at maximum level sufficient water level head is provided above the pump inlet to avoid the formation of inlet vortices and the consequential effects of air ingestion such
13. as cavitation 2 4 Pumps The pumps are Swiftech MCP 35X branded units which are re badged Laing Thermotech utilising a DDC3 1 PWM PCB Printed Circuit Board The MCP 35X is an electronically commutated spherical motor pump The only moving part in the unit is the permanent magnet spherical impeller and this is supported by a ball shaped ceramic bearing The implementation of such a bearing effectively eliminates bearing play and any associated noise increase and ensures that the bearing is self realigning The internal components are lubricated directly by the media being pumped known as a wet rotor design The permanent magnetic impeller is driven by a stator built into the pump housing that wraps a magnetic field around the impeller as this field is switched on and off the impeller rotates The MCP 35X features RPM tachometer output as well as PWM Pulse Width Modulation speed control input opecifications are given below Pump Specifications Operating RPM 1 300 4 500 via PWM Max Nominal Head 12 VDC 44 mH2O Max Nominal Flow Rate 12 VDC 0 292 L s 17 5 L min RPM Signal Open Collector 20mA 0 24 VDC Square Wave 2 pulses per revolution PWM Signal 5V DC 20 25 kHz G4 BSPP Female Threaded Inlet amp Outlet University of Technology Sydney O 2012 Page 4 Coupled Tanks Generation Il Laboratory User Guide Version 1 4 2 5 Flow Meters The flow meters are Parker DataFlow Compact DFC900010
14. ce and bobbing of the magnetic float University of Technology Sydney 2012 Page 21 Coupled Tanks Generation 11 Laboratory User Guide Version 1 4 6 2 Contacting Support Any questions regarding the nature of assessment tasks should initially be directed to the relevant academic If the user encounters any difficulties during the course of using the rigs the Contact Support button should be used to request assistance and report an incident The following popup will appear please enter your name and a valid email address followed by a category from the Type drop down list Remote Labs Login ER UNIVERSITY OF y ios ig 5 NREMOIEJC BS ES bs 22 M Contact Support x Login Laboratory Rigs The request will be sent to the Remote Labs support team Name Email Type Help Request Purpose Feedback You may then enter a brief statement regarding the nature of the request in the Purpose field Be sure to enter as detailed a description as possible of the incident in the Feedback field 6 3 Providing Feedback Users are strongly encouraged to leave feedback and comments of their experience with the rigs to help improve the system as well as any suggestions for additional features to be included in the future For any enquires or assistance contact the Labshare helpdesk at helodesk labshare edu au University of Technology Sydney 2012 Page 22
15. cess can occur from anywhere and at any time Their interaction with the remote equipment is assisted by the use of data acquisition instrumentation and cameras providing direct feedback to students for better engagement Traditional engineering laboratories require students to be physically present in order to work with equipment which may limit student flexibility Conversely remote laboratories let students work in their own time and even repeat experiments for better learning outcomes Of course students cannot actually touch and feel the equipment in a remote laboratory but they can still perform most other tasks relevant to their learning Sometimes separation from potentially hazardous equipment is preferable from a safety point of view Due to the increased use of remote operation in industry where machinery and entire plants are often controlled from a distant location students may directly benefit from learning how to remotely control equipment Furthermore remote laboratories provide the opportunity to access a wider range of experiments as costly or highly specialised equipment may not be locally available This presents the opportunity to share laboratory facilities between institutions oignificant research and pilot studies have been undertaken in Australia and by several groups around the world into the educational effectiveness of using remote laboratories These studies have consistently shown that if used appropriately in a
16. d by counting the number of pulses during the acquisition window Currently the acquisition window is set to 2 Hz so as to allow a reasonable update frequency on the flow meter data plot When the flow rate is for example 1 0 Litre per minute 0 0167 L s one would expect 752 pulses per minute 12 53 pulses per second Since the acquisition window is 2 times per second 2 Hz we would expect to count 6 265 pulses However the flow meters generate their pulses through the use of a photo interrupter an electromechanical method Since we count the full number of pulses during the acquisition window effectively rounding down to the nearest pulse each time we would thus only count 6 pulses Small variations in the flow rate can thus have an effect on the data displayed For 6 pulses when the value is converted into a flow rate using the K Factor we arrive at 0 957 L min 0 0159 L s approximately 4 lower than the true flow rate Resolution at this flow rate is thus 20 The good news is that as the flow rate increases the error due to this rounding down becomes smaller At 10 Litres per minute the error is only 1 1 of the true flow rate Resolution at this flow rate is thus 2 Photo Interrupter lt TET gt 1 Pulse Fluid Flow Above Simplified diagram of how the flow meters generate their output signal University of Technology Sydney O 2012 Page 19 Coupled Tanks Generation 11 Laboratory User Guid
17. de Version 1 4 4 1 3 System Overview Animation In addition to the plots noted previously an animation of the system with instantaneous display of important data 15 provided The level of each tank is illustrated and the instantaneous level can be observed by looking at the corresponding numerical readout shown on each tank Additionally the instantaneous inlet flow rate inter tank flow rate and outlet flow rates are shown 158 55 EE 102 72 4548 RPM 3 2 Lim The current valve position as percentage is displayed next the valve The Pump status is indicated by the colour surrounding the impeller green for ON red for OFF with the impeller soeed displayed in RPM to the right Finally the setpoint for the desired level for Tank 2 15 indicated by the red line University of Technology Sydney 2012 Page 12 Coupled Tanks Generation 11 Laboratory User Guide Version 1 4 4 1 Open Loop Control The Coupled Tanks Generation 11 Rig has two operating modes The first is Open Loop Manual mode whereby the user controls the valve position and consequently the inlet flow rate directly 4 1 1 Valve Position Inlet Flow Rate As noted above in this mode the valve position and hence the inlet flow rate is adjustable by the user You can either type in a value in the input box with up to 2 decimal points of precision and press enter to set it or drag the yellow slider to your desired position or adjust the
18. do with this file C Openwith Notepad def HEHEHE EH NE Loot SAVE o Do this automatically for files like this from now Help 1 After clicking the text file title a browser specific download window should appear be sure to click Save File or similar in this window to save the file in an appropriate location on your computer University of Technology Sydney 2012 Page 17 Coupled Tanks Generation Il Laboratory User Guide Version 1 4 6 FAQ amp Troubleshooting 6 1 Hardware Limitations The following hardware limitations apply to the rig care should be taken to avoid mistaking real phenomena as faults and the limitations should be observed when selecting the operating parameters for the rig 6 1 1 Inlet Flow Rate Pump Continuously Valve Minimum Setting You may notice that the pump can never be switched off and that water is always flowing into the tank even when the valve position is set at the minimum possible 0 A design decision was made to avoid startup lag of the pump complicating the experiment As a result the pump is always on and its flow rate is modulated by the valve In order to avoid damaging the pump a minimum flow rate of approximately 1 0 L min was deemed necessary with this being achieved when the valve position is set at the minimum possible value of 0 6 1 2 Outlet Flow Meter amp Low Water Level When the water level in Tank 2 is very
19. e Version 1 4 6 1 2 Overflow State When the inlet flow rate to Tank 1 is set too high in Open Loop control mode it is possible to reach an overflow state whereby the water level in Tank 1 rises and reaches a stagnation point as the inter tank coupling valve flow rate is not high enough to transfer the water to Tank 2 As a result the water level in Tank 1 reaches a maximum of approximately 295 mm 2 5 mm and spills over into the overflow section of the tank When this occurs the user will see a sudden transition to a continuous level on the level data plot and additionally the level readout for Tank 1 will show approximately 295 mm Note that Tank 2 can never reach overflow due to the pressure drop AP through the inter tank valves the maximum level for Tank 2 15 approximately 255 mm 150 50 60 0 Time 5 Above Tank 1 reaching the overflow point of approximately 295 mm Note that Tank 2 can never reach overflow due to the pressure drop AP through the inter tank valves is important to note that once the tank has reached overflow any data recorded for certain modelling techniques e g step response Is invalid as the true level that would be reached cannot be measured Flow 1 Flow 2 Flow 3 Flow L min 20 30 40 50 60 0 Time Above The inter tank flow rate red dropping as the level in Tank 2 attempts to match that of Tank 1 Univer
20. ected Logged In Status Login OK Clear Plot Start Save Above The system approaching steady state Note the flow rates converging and the levels flattening out University of Technology Sydney 2012 Page 13 Coupled Tanks Generation 11 Laboratory User Guide Version 1 4 4 2 Closed Loop Control The Coupled Tanks Generation II Rig has two operating modes The second is Closed Loop PID mode whereby the user enters a level setpoint for the secondary tank and the PID controller coefficients they wish to use 4 2 1 Setpoint amp PID Constants By entering a setpoint and PID constants calculated from a model of the tank system or from an on line response test the coupled tanks system will be able to perform closed loop control In this mode the system monitors the level in the secondary tank and automatically adjusts the valve position and consequently the inlet flow rate on the fly according to the PID constants set As a result extremely accurate setpoints can be reached typically 0 1 mm intervals with maintenance within 0 1 mm is up to the user to elect values that will render an appropriate response i e targeting the fastest response time minimum overshoot etc UNIVERSITY OF femfibtelabs Coupled Tanks A Setpoint _ Manual PID Setpoint mm 400 Sm Enable Level mm 60 0 80 90 100 Time 5 r Flow Limin Time Connected Logged In Status Login Clear
21. esseueeeeseaeeessagecessaeeeeseaes 7 2 10 inen zio ME RRRTUCUTTURTTE 7 Lm reme 8 3 1 RO ecoa a a 8 3 2 RO 9 4 TRIG Control SOW suus iuba iM NR 10 4 1 Hr TEES 11 Aled ada Ani unido ed ac n te Mat ient UN 11 MEE o UR ICU 11 4 1 3 System Overview Animation sc cc2a sensacexeeeesearaxnscecsiaenetae suasacententauarsasenuaginatasdencadeaeiacarcneteneweseuame 12 4 1 CONTO renske 13 4 1 1 Valve Position Inlet Flow 13 44 2 vOe Loop dtu 13 4 2 ClOSCG LOOD CONIO MEI I uu 14 421 SEPON PID CONSAN ds ek cece pec le ete iac 14 4 3 Switching Between amp os 14 SEE Sis NP ci pite 15 5 1 Datas Manual a E 15 5 2 late PID MOAS 16 9 9 Saved 2 podes chess tente
22. low the flow meter readings for the outlet may appear very high and there may appear to be significant changes in the flow rate These readings do not reflect the actual flow rate through the outlet and occur as a result of the operating principle of the flow meters Flow 2 a Flow 3 Tr E 15 20 2 30 35 40 15 40 Time 5 Above Flow Meter Data Plot showing incorrect outlet flow rate due to vortex formation At levels below approximately 10 mm in Tank 2 a vortex forms and air is ingested into the tank outlet and accordingly the outlet flow meter This causes inaccurate readings to be observed as the operating principle of the flow meter depends on the impeller and flow meter cavity being saturated entirely with water Outlet Vortex Above Simplified diagram of outlet behaviour at low water levels University of Technology Sydney 2012 Page 18 Coupled Tanks Generation 11 Laboratory User Guide Version 1 4 6 1 1 Flow Meter Signals The signals from the flow meters may appear to be quite noisy this is however not noise but an artefact from the way the flow meters generate their signal and can be viewed as a quantisation of the signal a 300 320 340 360 380 400 120 Time 5 Above Meter Data Plot showing signal artefacts which may be mistaken for noise The units have a K Factor of 752 pulses per litre The data from the flow sensors is acquire
23. n Rig is controlled by a National Instruments Compact Real Time I O Controller aka cRIO The cRIO chosen a cRIO 9022 has a 533MHz controller with 2GB storage 256MB DDR2 RAM USB RS232 interfaces and dual Ethernet ports For I O the chassis cRIO 9114 with embedded Xilinx Virtex 5 FPGA has 4x NI 9403 32 Ch 5 V TTL 7uS Bidirectional Digital Modules installed as well as 1x NI 9208 16 Ch 20mA 16 Bit 200kS s Current Input Module Interfacing to each rig is performed a custom PCB designed at UTS that re routes the I O lines from the DB37 connector on each I O module to a DB25 connector for each rig This then simply connects via a standard DB25 cable providing a complete and simplified I O solution The use of digital I O and current rather than voltage based sensors reduces the amount of noise and signal degradation in the rig Control of the rig is performed through a LabVIEW application that communicates with the cRIO presenting the user with accurate real time information and control of each rig Real Time Controller Specifications Manufacturer National Instruments NI Controller NI cRIO 9022 Real Time I O Controller Chassis NI cRIO 9114 Controller Specifications 533MHz controller with 2GB storage 256MB DDR2 RAM Chassis Specifications 8 slot Virtex 5 LX 50 Reconfigurable Chassis 4 x NI 9403 32 Ch 5 V TTL 7uS Bidirectional Digital Modules VO Modules 1 x NI 9208 16 Ch 20mA 16 Bit 200kS
24. ol software displays numerous sources of data in real time Familiarise yourself with the display and relevance of this data by reading through the sections below Please be aware of hardware limitations that are outlined in section 6 1 Hardware Limitations of this document before reporting any faults with the rig from data shown on the displays described below 4 1 1 Water Level Plot In both Manual and PID modes the water level is displayed for Tank 1 and Tank 2 in real time with units of millimetres The tank is empty at 0 mm 0 5 mm and reaches overflow at 295 mm 5 mm TaT Time Tank 1 has the label Level 1 and is shown in Blue Tank 2 has the label Level 2 and is shown in Orange In PID mode only the desired level for Tank 2 has the label Setpoint and is shown in Red 4 1 2 Flow Rate Plot In both Manual and PID modes the flow rates for different points in the system are displayed in real time with units of Litres per Minute L min Three different flow rates are given for the system Flow 1 Flow 2 and Flow 3 Flow L min 15 20 25 30 35 40 45 450 Time Flow 1 is shown in White Flow 2 is shown in Red and Flow is shown in Green These flow rates correspond to the Inlet Flow Rate Tank 1 the Inter Tank Flow Rate and the Outlet Flow Rate Tank 2 respectively University of Technology Sydney 2012 Page 11 Coupled Tanks Generation 11 Laboratory User Gui
25. olution to be programmed via DIP switches Specifications for this hybrid unit are given below Control Valve Specifications gt Valve Material Brass Fittings 1 NPT Female Threaded Inlet amp Outlet gt Control University of Technology Sydney 2012 Page 5 Coupled Tanks Generation Il Laboratory User Guide Version 1 4 2 7 Inter Tank Coupling Valves The tanks are coupled with a pair of fullway ball valves made by Giacomo Cimberio S P A These valves have a G3 8 BSPP female threaded inlet amp outlet Teflon stem and ball gaskets and a hot forged brass ball and body To aid in maintenance of the system UTS developed custom push fit connectors which attach the valves to the tanks The push fit connectors use a double o ring system which allows for easy removal of the coupling valves for maintenance inspection amp replacement The specifications for the coupling valves are given below Coupling Valve Specifications Manufacturer Giacomo Cimberio S P A Model Number CIM312 Valve Type Fullway Ball Valve Butterfly Handle Ball amp Body Material Hot Forged Brass Stem amp Ball Gasket Material Teflon P T F E Flow Factor K 10 m hr with AP 10 mH2O G3 8 BSPP Female Threaded Inlet amp Outlet 2 8 Level Sensors with Magnetic Floats The level sensors used are MTS Temposonics GH Rod Style magnetostrictive position sensors These sensors use the principle of magnetostriction a phenomena tha
26. sity of Technology Sydney 2012 Page 20 Coupled Tanks Generation 11 Laboratory User Guide Version 1 4 6 1 3 Magnetic Float Bobbing amp Disturbance When looking closely at the level sensor data for Tank 1 it is possible to see small fluctuations in the level There are two reasons for this the first is due to the way the water flows into the tank and the second is due to the way the magnetic floats are coupled to the level sensors The water flow into the tanks is de coupled except at the very upper reaches of the tank level close to the overflow level of 295 mm This means that the flow stream exists in free air and reaches the water surface due to the effect of gravity When the flow stream hits the water surface it thus makes a disturbance creating small variations in the water level recorded by the level sensors Additional variations in the water level are seen by the level sensors due to the magnetic floats having a significantly larger internal bore diameter when compared to the outer diameter of the level sensors As a result in a steady state condition the floats move around with the water current in the tank These variations are very small sub millimetre and should not impact any typical experiments undertaken on the rigs Level 1 n Level 2 na Setpoint na mm 200 220 240 260 280 300 320 Time 5 Above Small variations white the recorded water level due to surface disturban
27. t causes a material to change shape during magnetisation To allow the sensor to measure a level or distance an external magnet located at some position along the wave guide generates its own magnetic field within that vicinity The sensor sends a current pulse along the wave guide and when the current pulse reaches the position of the external magnet the two magnetic fields interact producing a strain pulse It is the time between the current pulse and this returning strain pulse that is measured by the sensor and then converted into an output signal that corresponds with distance The sensors used here output a 4 20 mA current signal to the real time I O controller allowing for accurate and fast measurements To allow for measurement of the fluid level in the couple tanks a magnetic float is used to provide the required external magnetic field to interact with the current pulse Specifications for the level sensors are provided below Level Sensor Specifications Manufacturer MTS Update Time lt 1ms Typical Resolution Infinite Restricted by output ripple Non Linearity 0 02 Full Stroke 50 um min Repeatability lt 0 001 Full Stroke 2 5 um min Signal Output 4 20 mA Dead Zones 51mm from Flat Faced Flange 63 5mm from Rod End University of Technology Sydney 2012 Page 6 Coupled Tanks Generation Il Laboratory User Guide Version 1 4 2 9 Real Time I O Controller The Coupled Tanks Generatio
28. way that is cognizant of the intended educational outcomes of the laboratory experience remote laboratories can provide significant benefits Indeed multiple research studies have demonstrated that whilst there are some learning outcomes that are achieved more effectively through hands on experimentation e g identification of assumptions specific haptic skills there are other learning outcomes that are achieved more effectively through remotely accessed laboratories e g processing of data understanding of concepts Engineering students are able to access the Coupled Tanks Generation II Rigs to help them develop and verify their mathematical models of the complex system dynamics involved in a SISO MIMO coupled tank system The Coupled Tanks Generation allows students to Characterise the behaviour of a Single Input Single Output SISO or Multi Input Multi Output MIMO coupled tank system o Note As of mid 2012 the Coupled Tanks Generation Rig is only capable of running in SISO mode as MIMO functionality requires hardware that is not yet implemented into the system Acquire experimental data to assist in developing a simplified model of the system Implement a PID controller to manage the inlet flow rate of water such that the water level in the desired tank is kept constant University of Technology Sydney O 2012 Page 2 Coupled Tanks Generation 11 Laboratory User Guide Version 1 4 1 2 Coupled Tanks Generation
Download Pdf Manuals
Related Search