Controlling and Monitoring Air Speed in a Wind Tunnel


Bachelor Thesis, 2015

45 Pages


Free online reading

TABLE OF CONTENTS

ABSTRACT

LIST OF ABBREVIATIONS

LIST OF FIGURES

LIST OF TABLES

Chapter 1 Introduction
1.1 Problem
1.2 Background
1.3 Scope and Objectives
1.4 Document Overview

Chapter 2 Literature Review
2.1 PID Control
2.2 Wind Tunnel
2.3 Web Based Monitoring
2.4 PWM

Chapter 3 Materials and Methods
3.1 Implementation of Design
3.2 PWM Test
3.3Web Based Monitoring Test

Chapter 4 Results and Discussion
4.1 Results
4.2 Discussion

Chapter 5 Conclusions and Recommendations
5.1 Conclusions
5.2 Recommendations

REFERENCES

Appendix A Project Planning

Appendix B Design Drawings & Component Specifications

Appendix C List of Software Code

Appendix D Relevant Standards

Appendix E Other Technical or Data Appendices

LIST OF ABBREVIATIONS

illustration not visible in this excerpt

LIST OF FIGURES

Figure 1 Simulation of System controlled by Proportional Controller

Figure 2 Simulation of System Controlled by PI controller

Figure 3 PWM Pulses with Different Duty Cycles and Period

Figure 4 Brushless Flow Fan Drawing

Figure 5 Monitoring Step Block diagram

Figure 6 Circuit Used for Connecting PLC to the Fan

Figure 7 Online Monitoring Screen Shot

Figure 8 Screen Shot of the Command Prompt / IP Configuration

Figure 9 Screen Shot of the Command Prompt / PLC's IP Address

Figure 10 Customized Web Page

Figure 11 Wind Tunnel Drawing

Figure 12 Wind Tunnel's Frame Drawing

Figure 13 Wind Tunnel's Third Angle Representation

Figure 14 Previous Wind Tunnel Dimensions

Figure 15 Previous Wind Tunnel 3D Drawing

Figure 16 Wind Tunnel and Its Sensor Attached/ Internal View

Figure 17 Brushless Fan Drawing

Figure 18 Nano 10 Image

Figure 19 Omron Anemometer Sensor Image

Figure 20 RS Power Supply Image

ABSTRACT

The project proposes a construction of a wind tunnel controlled and monitored by a system containing a Web Based monitoring interfaced to a Programmable Logic Control network that carries out an application program which receives inputs from an anemometer sensor for measuring the airspeed performed by the fan and from a User Computer, which chooses airspeed values to be implemented by the Brushless fan. Both inputs are compared by the PID controller, control mode used by the PLC system, and the output is generated with base on the inputs received by the PID controller.

This system after set properly, is able to measure airspeed value provided by the Brushless fan in real time, transferring it to the PLC via internet where it is displayed in a Web page developed for this system.

ACKNOWLEDGEMENTS

Firstly, I am really thankful to God for giving me this incredible opportunity of working in a sophisticated project, covering a rising area in Mechatronic Engineering as the Control area has been.

Besides, I want to thank Mr. Manoelino Coutinho de Paula, my father, Mrs. Valdelice Gomes Coutinho, my mother, and Bruno Donatti, my fiancé, for all support and hopeful words that they have gave to me while being at Ireland.

Finally, I have many reasons to be thankful to my academic adviser, Derek Kerr, for providing me all the guidelines, explanations, always increasing my technical and theoretical knowledge, helping me to bring this project to the reality.

DECLARATION

The work submitted in this report is the results of the candidate’s own investigations and has not been submitted for any other award. Where use has been made of the work of other people it has been fully acknowledged and referenced.

Student Name

Chapter 1 Introduction

Wind tunnels are special equipment where is installed a fan for providing air flow, simulating the natural wind and the consequences suffered by the objects exposed to this perturbation.

The main objective of this project is to design, to implement and to monitor the air speed flowing through the wind tunnel using PID control and Web-Based monitoring system. To implement the Web-Based monitoring, a web page will be provided, where the desired air speed, Setpoint, will be selected for being performed by the Brushless fan. Its DC motor will be controlled by a PLC in order to produce air flow in the desired air speed, which will be measured by a sensor and displayed in the web page.

The PLC will provide the PID closed loop control that will use the desired airspeed and the airspeed measured by the sensor as its inputs.

1.1 Problem

In this project, an equipment responsible to provide air flow, the wind tunnel, will be constructed. This equipment will be used to store a sensor for measuring the airspeed flowing through the tube. The measurement came from the sensor will be received by the monitoring system used in this project, the Web Based monitoring.

The Web Based monitoring system consists of a web page created to display all information regards to the wind tunnel control and to enable the user to choose the speed desired to be performed by the fan.

The controller for this system will be the PID control, which will receive as inputs the current air speed value performed by the fan and sensed by the sensor and the desired air speed selected by the user in the web page. Once getting these data stored, the controller takes some necessary control actions that will force the system to achieve the air speed picked up by the user.

1.2 Background

As long as industries have suffered a high development in their technologies and products, more their systems to be operated have became more complex and more they have needed to be controlled and monitored from far distances and with more accuracy.

The PID control has provided satisfactory results while applied in industrial environment. Despite of being in use for many decades, it is still the best choice for many manufacture areas, as they can supply their necessities in eliminating errors in production, decreasing the production time and increasing their efficiency.

It is known that PID controller is consisted by some weakness and disabilities. However, when it is summed with other devices, it can be powerful for solving industry issues and achieving desired specifications, what turns it worthier if it is compared with some new control methods that have emerged in current days. One way of enhancing a control system is adding a Web Based monitoring to it, what enables the process’s variables to be controlled and supervised even if the plant is in a remote location.

Nowadays, purchasing new control methods demands high investments that sometimes do not bring the expected return. Most often the control method may cover up one deficiency in the system but not being efficient for solving other issues. Therefore, it is highly relevant to keep on testing PID control and to explore others possibilities for it, as it has a good price return when making use of what it provides of best. Furthermore, adding other control tools as Web Based monitoring, for improving the current control models, makes the system more powerful.

1.3 Scope and Objectives

In this project a wind tunnel will be built and controlled by PID controller. All performances related to the air speed came from a Brushless fan will be monitored by Web Based.

The building of the wind tunnel is not the focus itself of this project, as consequence, the wind tunnel constructed for this project will not have big dimensions and complex design, but it will be just decent enough to store the anemometer sensor and to fit a Brushless fan on its diameter.

Therefore, the main purpose on this project is to control and monitor the air flow process, testing it and improving the control and monitoring methods applied in current days.

1.4 Document Overview

In this project, the chapter 1 introduces the reader to the important aspects regards the project, containing all information in advance which the reader must be aware, understanding the project purpose, the concept of the methods to be implemented in order to achieve the project objectives, the project relevance and the project applications in current days.

The chapter 2 covers up a research on all concepts and devices involving the wind tunnel built and its control and monitoring implementations.

The chapter 3 provides a list of all materials and methods applied, with explanations on each feature function. Besides of displaying a block diagram with the data type flowing to each device used, it is described all steps for assembling the complete system, letting it ready for being tested.

Lastly, the chapter 4 delivers the results after testing and the discussion related to what improvements could be implemented to this project. Finally, in chapter 5 is placed the project conclusion and recommendations.

Chapter 2 Literature Review

2.1 PID Control

PID is a method of control defined by proportional, integral and derivative modes of control.

These control actions are based on the past, present and on the future prediction. Each mode contributes in different ways for making the system to achieve the Setpoint (the desirable value) even in presence of disturbance.

PID control is followed by 4 modes of control: Proportional control (P), Proportional Derivative (PD), Proportional Integrative (PI) and Proportional Integrative Derivative (PID).

Regards the proportional controller, P, when used alone, followed by a first order system, it follows the equation below:

C(s) = Kp ;

As the transfer function in closed loop is defined by T(s) =[illustration not visible in this excerpt]and K= System Gain; Kp = Proportional Gain; Y(s) = Output; U(s) = Input ;

The T(s) equation is a result, T(s) = Simulink returns:[illustration not visible in this excerpt] which after being simulated in

illustration not visible in this excerpt

Figure 1: Simulation of an uncompensated open loop system and a closed loop system compensated by proportional gain.

By simulating the system built in Simulink, there are two curves on the simulation that are the response to a unit step. The blue line corresponds to step response from a system compensated in a closed loop with proportional gain Kp = 0.5, while the red line is the step response of a first order system in open loop and uncompensated system.

In the Matlab plot, it is clear that the proportional controller decreases the rise time if compared to an uncompensated system and the steady state error is decreased.

Another thing to be noticed in the transfer function is if the proportional gain Kp is really increased, tending to a high value, T(s) tends to 1, making the output virtually equal to the input.

Despite of making the system follow the reference input, proportional controller is not able to eliminate steady state error, the offset. Besides, as its control action is proportional to the error, if there is no error, there is no controller output, what makes impossible to achieve the reference value. Consequently, proportional control is not used alone in most of systems.

In addition, the high overshoot is not decreased by this controller.

The Proportional Integrative controller that stands by PI, is a controller that carries proportional and integrative action.

Its equation is given by :[illustration not visible in this excerpt]

As the integrative control action is proportional to the integration of the error with time, PI is able to eliminate the steady state error whether it is constant, removing the offset from the output.

In second order systems, when applying the PI controller, it turns :

illustration not visible in this excerpt

It is possible to see that one zero was added at [illustration not visible in this excerpt] and one pole at s = 0. Hence, Ki and Kp can not be bigger, in order to make the zero gets closer to the origin and away from the most significant poles.

The integrative gain Ki depends on the capacitance value, where as higher is the capacitance value, lower is the integrative gain. Therefore, effective PI control requires small values for Ki.

Despite of PI controller being a great low pass filter, that filters out high frequency noise, being largely indicated to eliminate steady state errors and disturbs, systems with PI controller tends to be slower and more oscillatory, thus, if one system is supposed to be fast, PI controller is not the right choice. Consequently, if the PI controller gains are not chosen properly, the system becomes unstable.

In order to compare one second order system [illustration not visible in this excerpt] compensated by PI controller, where Ki =0.01 and Kp =2 with the same second order system compensated

by P controller, where Kp =2, another simulation was done in Simulink, for making possible to notice that when PI control is used, the steady state error can be eliminated:

illustration not visible in this excerpt

Figure 2: Simulation of a Closed Loop System Compensated by a Integrative Gain and a Closed Loop System Compensated by Proportional Gain.

In the plot above, the red curve corresponds to the system compensated by PI control, and the blue curve represents the same system compensated by Proportional controller only. As it is notable in the plot, both systems achieved the same overshoot value, though the steady state error was eliminated by PI controller, while in P controller it did not happen.

The Proportional Derivative controller stands by PD and is a sum between proportional control action and derivative control action. Its equation is known as:

C(s) = Kp + Kds, where Kd is the derivative gain.

The PD controller is an anticipatory control which is compound of proportional and derivative control modes. The derivative mode control produces a control action that is proportional to the rate in which the error is changing related to the time, and the proportional control mode provides a control action which is proportional to the error. By just knowing the current error slope, the controller can anticipate the error direction and takes decisions in advance, what enhances the control.

Using a mechanical machine as an example to understand how the PD controller works, lets consider a positive torque in one time interval, what produces a high overshoot. The controller will analyze it and send a command to stand for a negative torque, in one attempt of not producing a high overshoot in the next time interval. Therefore, PD controller provides predictive action.

PD controller makes the system becomes more damped as Kd gain is increased, improves the system stability, decreases the overshoot and when using PD controller, the system is turned faster. However, if it is required solutions regards to the error, PD controller will not provide the expected result, as if the error increases with time, PD controller will take control action which will change the steady state error, trying to solve this issue. Finally, if the error is a constant, the derivation of this constant will be zero, what will not provide change in the final value.

Despite of all enhancements that PD can offer to a system, it accentuates the noise, as it is a high pass filter. Thus, if a system is affected by noise in high frequency, PD controller will not work well.

As it was mentioned, it is possible to use all the control actions in one only controller, in this case the PID controller. When making use of proportional, integrative and derivative control modes, a more complete control may be acquired, by summing all the advantages of each control mode .

In order to solve all the issues faced by industrial process as response time, offset, elimination of disturbs by integrative action control, the feedback and the anticipating of the future by derivative control action, PID can be employed in almost all existent processes, unless it is impossible to meet the specifications for making a balance between the PID parameters.

PID controller provides the following equation:

illustration not visible in this excerpt

Nowadays, the tuning methods available are the Ziegler Nichols rule, the Coen - Coon method, the IAE, the ITAE and the Internal Model Control . Each tuning method may be properly or better employed in one particular process and situation. Consequently, there is no the best or worst tuning method, it depends on only what is the process and the project specifications.

2.2 Wind Tunnel

Wind Tunnels are large tubes with air moving inside it, that works in order to measure the airspeed, testing the stability and behavior of objects in flight or objects that may suffer the action of the wind.

Wind Tunnels have been largely used for over the past 50 years for tests in civil engineering, aerodynamic engineering (in this case for construction of air planes and aircrafts), in studies of Aeolian Processes and etc, as it provides an air stream flowing under controlled conditions, predicting its effects.

Regards to the Wind Tunnel design, there are 2 types related to its geometry, the Open loop Wind Tunnel and the Closed loop Wind Tunnel. While in the first type the fresh air is drawn into the entrance and expelled at the exit, the second uses the expelled air again, making it being re-circulated.

As the Wind Tunnel has the main proposal of measuring the airspeed, it will also differ by the airspeed which will be tested and required as well. The three types are defined by Low Speed Wind Tunnel, Supersonic Wind Tunnel and Hypersonic Wind Tunnel. However, for this project, a Low Speed Wind Tunnel will be built, in open loop.

2.3 Web Based Monitoring

Web Based Monitoring consists to a mode of monitoring that connects the plant equipment and process to the Internet or Intranet, permitting the user to have access to all information regards to a process, by monitoring it in a real time, besides controlling all the variables involved in this process.

The basic parts required for web-based data acquisition and control are: an interface to the machine or process to be monitored or controlled via web connection, a web server to make available one display and/or control pages to the PC and a data service or interface to make possible the exchange data between the local machine/process and the remote system (PC).

2.4 PWM

PWM stands for Pulse Width Modulation and it is a clever mode of controlling power in electrical devices. It is characterized by a duty clock, measured in Hz, and by the duty cycle, measured in percentage %. The signal amplitude is kept stable during time though its width is increased or decreased, depending on its duty cycle, where it is on for a period of time and off for the rest of the time.

The total power delivered to the load to be controlled is the area under the positive state of the PWM. As the area depends on the duty cycle, the pulse width, if the duty cycle has the value of 1, it means the load is receiving 100% of the voltage. However, when the duty cycle is modified, the result is a decrease in the area of the power delivered to the load. Hence, it when the duty cycle is modified, the power delivered to the load is also altered.

Regards to the DC motor, it is known that its speed is an answer to the power received. The fan used in this project is not a standard fan, featured by 2 wires, but it is a PWM fan featured by 4 wires : ground, power, tach signal and PWM signal input, what besides being powered can have its speed controlled in the same time, using the PWM signal.

illustration not visible in this excerpt

Figure 3: PWM Pulses with Different Duty Cycles and Period.

Chapter 3 Materials and Methods

Bellow, there is a description of all needed devices to implement this project and their functionalities:

-PC : The Web page for monitoring the system is created in the PC and the desired airspeed is selected on this Web page.

- PID/ PLC : The PID controller is present in the device called PLC which will be connected to the DC motor coupled to the fan. The PID controller receives a couple of inputs, the desired airspeed value from the PC and the current air speed value from the sensor. As it is provided two values to the controller, these inputs are compared and the controller takes the properly control action for making the system achieves the Setpoint.
- Motor/Fan : The motor is attached to the fan. Motor and fan are the actuators of this system. The PLC provides pulses to the motor driver, but before it arrives in the motor, it comes to the D/A converter and after being turned in the analogical airspeed it achieves the fan, whose motor will perform the speed in conform with the PWM duty cycle.
- Anemometer : It is the proper sensor for measuring the wind speed value and to return this value as a digital input to the PC.
- A/D converter and D/A converter : The A/D converter is a device that converts the analogical signs in digital signs, while the D/A converter converts the digital signs in analogical signs. It is normally included on the devices in order to each device receive the proper sign, taking one sign type and turning it in the sign type which this device

was developed to receive.

illustration not visible in this excerpt

Figure 4: Wind Tunnel Block Diagram.

The figure above demonstrates the signal types that each device receives and how the data flows in this system. The PLC CPU first analyses the logic states of the inputs, in this case the desirable air speed coming from the PC and the current air speed measured by the sensor and converted in digital value by the A\D converter. Both of the inputs are stored in PLC CPU memory and by processing these inputs the ladder program will be carried out.

After the date being stored in the CPU memory, the PID controller will compare the inputs for applying the proper control action in order to the system achieve the Setpoint. The PLC will provide pulses to the motor, which will be converted in an analogical speed value before being performed by the motor. Once the airspeed was converted to an analogical value, the fan will perform the required airspeed output, which will be measured by the Anemometer. The Anemometer's output will be converted in a digital value for being received by the PLC.

The described process above can be summarised in the ladder logic scan, one process performed by PLC and defined by 3 steps: read physical inputs, execute the program contained in the PLC and update the outputs. It happens continuously all the time, as a loop. However, the output bits are updated only after the logic scan ends up.

Bellow, there is a preview of the wind tunnel features:

1. Settling Chamber : It is responsible for eliminating the swirl and unsteadiness from the flow, making it smooth.
2. Contraction Place : It provides a contraction, by making the flow more uniform and by decreasing the air's volume in the airflow in order to increase the air speed and the flow in the test section.
3. Test Section : In this section is located the sensor, that will measure the air velocity. In aerodynamic tests, the test section is the place where the planes and aircrafts are submitted to tests regards to the resistance and behaviour faced to the airspeed variations.
4. Diffuser: It decreases the air flow velocity from the test section, decreasing the air flow pressure until achieving the static pressure.
5. Motor and Fan : It provides the airflow following the commands given by the controller.

However, the wind tunnel model described above will not be used in this project. The features composing our wind tunnel will be only the Settling Chamber, the Test Section and the Motor/Fan, as the main aim of this project is not the wind tunnel construction, but the PID performance in controlling the air speed and the monitoring of this wind tunnel by Web-Based.

A block diagram was included below containing the PC, the PLC, the router and the modem , all devices involved in this stage.

illustration not visible in this excerpt

Figure 5: Block Diagram for the Monitoring Step in the Wind Tunnel.

First of all, the PLC has to be connected to the PC. It can be connected via RS232 using a USB-RS232 adapter or via RS485 using a USB-RS485 adapter.

After connecting the PLC to the PC, the PC and PLC should be connected to the router, and the router connected to the modem, for allowing the internet access to the devices linked to the router.

Related to displaying the results and variables, it is relevant to be aware that there is no way of connecting some LCD display to the PLC. The Nano - 10 PLC has not a connector for connecting to a physical LCD display. However, the variables can be displayed in the PC screen, using the I-TRILOGI online monitoring function as a virtual LCD.

Furthermore, the LCD content can be released from a web browser using the correct web service command. The SETLCD command, present in the Nano - 10 PLC, permits you to have access to the LCD display in real time by internet. Thus, it is possible to monitor all the desired variables by the web, visualizing it on the PC screen.

Regards to dimensions, the wind tunnel will have a length of 0.45m, and its circular diameter will be 0.1m. The material used for building it will be a Polyvinyl Chloride Plastic, PVC.

The PVC plastic is a material widely used in civil construction, in toy factories and in the hospital products production worldwide. It is 100% recyclable, of low cost, very resistant and an insulation material. Besides of all this advantages, PVC does not offer any health or security risk when it is manipulated in a properly way, making it to be really useful for the wind tunnel building.

3.1 Implementation of Design

Below, all materials needed for the project implementation are listed:

-1 Nano 10 PLC ;
-1 PC ;
-1 12VDC Regulator;
-1 5VDC Regulator;
-1 Optoisolator;
-Solder and Soldering Iron;
-Veros;
-1 AKASA - MH9225H12S - 0.26A DC BRUSHLESS FAN, 92 x 92 x 25mm, 12V ;
-1 PVC Pipe with 100mm of diameter and 450mm of Length ;
-1 OMROM MEMS Air Velocity Sensor ;
-Bolts, Nuts and Washers ;
-Drilling Machine ;
-1 24 V DC Power Supply ;
-Clamps ;
-Pliers ;

To hold the Wind Tunnel, one frame was built which dimensions and drawings are at the Appendix C.

Using a drilling machine, 2 centralized holes were made on the frame's surface, 1 in the beginning of the tube and another in the end, for placing a half of the clamp. The other half is fitted on the first by screwing the clamp screw.

To place the fan inside the tube, one PVC lid was cut off in the same format and dimensions of the fan. Firstly, the fan was fixed in the tube’s wall and then the lid was put over the fan housing, in order to fasten the fan in the tube. Finally, three holes were made in the lid by going through the tube using the drilling machine and then screws and nuts were put on these holes.

About the sensor, firstly it was attached to a Veroboard using screws and its wires were soldered on the vero. After, the vero/sensor set was attached to an aluminum stick, where 2 holes were made and then bolts, nuts and washers were put on it. After getting the sensor attached to the aluminum stick, a hole was made at the superior wall of the wind tunnel and bolts, nuts and washers were put on this hole for fixing the aluminum stick in the wind tunnel wall. The sensor was placed in a position in which it receives the air flow directly from the fan.

After getting the wind tunnel and the sensor wiring ready, the devices started to be connected to each other. In this stage, the Optoisolator, the 5 VDC regulator, the 12 VDC regulator, the wires coming from the sensor, the 24 VDC wire coming from the Power Supply, and the 12 VDC wire for the fan were soldered in the Veroboard. The inputs for the sensor and both regulators were powered up by 24 VDC from the Power Supply while their ground pin were connected to a common ground.

The first pin of the Optoisolator, from the bottom to the top, was connected to the ground, the second pin was connected to the fan’s control wire, the third pin was connected to the 5 VDC regulator output pin, the forth pin was connected to the ground and the fifth pin was connected to the PWM output coming from the PLC.

The Optoisolator receives 24 V PWM pulses from the PLC. In order to deliver a 5V PWM pulse to the fan, the Optoisolator uses the 5 VDC coming from the 5 VDC regulator output as its reference.

The 12 VDC regulator was used to turn the 24 VDC came from the Power Supply in 12 VDC, as 12 VDC is the voltage specified to feed up the Brushless fan which was chosen.

The first step, which is regards to the fan wiring, is to connect the fan's voltage wire (yellow wire) to the 12 VDC regulator output pin. After, the 12 VDC regulator input pin has to be connected to the 24 VDC coming from the Power Supply. The ground wire for the fan (black wire) must be connected to the 0 VDC coming from the Power Supply, the PWM wire (blue wire) is connected to the second pin of the Optoisolator, the sensor wire (green wire) has to be connected to the sensor input pin. The sensor output pin has to be connected to the Nano 10 PLC digital input port.

The PLC is powered by 24 VDC coming from the Power Supply, its ground wire is connected to the 0 VDC also coming from the Power Supply and its output 2 port is connected to the fifth pin of the Optoisolator. About the 4 switches which will be taken for test, they have to be connected to the PLC’s inputs while the their ground wire has to be connected to a common ground and then connected to the 0 VDC coming from the Power Supply.

The Veroboard was attached to the PLC board by screws and lastly, for getting the Wind Tunnel completely built, the PLC board was attached to the frame’s box and some holes were made on the wind tunnel wall in order to pass the wires through there for the Power Supply and for the fan.

3.2 PWM Test

Once the PLC is already connected to the power, a USB to RS485 converter is downloaded in www.tri-plc.com/U-485.htm, in order to convert the PC’s USB port directly to a 2 wire RS485 interface. To enable the communication between PLC and PC, the TLServer software is ran, inside TRILOGI folder available in the PC. After opening the PLC Webserver, it is necessary to click on Serial Port Setup button and wait the Serial Communication Setup & Test appear. In the Port Name tab should contain COM3, which is the correct port for top USB port on rhs of Manuela’s Laptop. At Command String tab, “IR*” has to be typed and then ENTER should be pressed. The PLC’s reply at Response String tab, should be “IR01*”, confirming that the PLC is ready to communicate with the PC.

As the communication between the PLC and the PC is set, a Red /Green light will be flashing in 485 converter and the Ladder program can be transferred to the PLC by clicking on the Controller button in the TRILOGI software and then on the “Program Transfer to PLC“ option. The last step is to click on “Online Monitoring” option at Controller tab and now it will be working via U485 cable.

Note that for the motor to be working, the output for PWM ,set up in the Ladder Program, has to be the same PWM output described in the Nano 10 manual user. If it is different the fan will not work.

3.3 Web Based Monitoring Test

At this stage, firstly the wireless is turned off and then the PC's Command Prompt is open. IPCONFIG is typed at Command Prompt in order to find out the PC's IP address. In Trilogi software, the Controller tab is selected and then “Ethernet & ADC Configuration” option. There it is necessary to click on the “ Factory Default” button firstly for after changing the IP address of the PLC to 192.168.43.23X, where X is the last IP address' number. If the PC's IP address is 192.168.43.237, X can be 7+1 or 7-1. Note that the PLC’s IP address must not be set to an IP address equal to the PC IP address.

To confirm whether the PLC's Ethernet Comms is working properly, the Command Prompt is open to ping the PLC’s IP address. Getting the PLC’s IP address correctly set, the yellow led on the PLC's Ethernet port should be lit and the green led on the PLC's Ethernet port should blink during data transfer. If all events described above happened, the TLServer can be stopped and the U485 cable can be removed as the comms is now via Ethernet port.

To enable the user to control the parameters for the DC motor by web page, it is strictly necessary to map the internal relay bits (from 129 to 136) to the PLC’s input/output. It can be done by accessing the i-Relay.PC6 program which contains the correct relay to be used for each input and output. After consulting this program, the Ladder program elaborated for the fan control has to be open and the relays added in parallel with its correspondent input or output.

When the PC and the PLC are connected via Ethernet port, the FileZilla Client program can now be installed, which will enable to develop the web page for the Nano 10 PLC.

After selecting the PLC's IP address as "Host" in General Tab on FileZilla menu, the Logontype should be set to "Normal" and the User and the Password must be the same as in Nano 10 PLC.

The next step to create the web page is to download the HMI samples from , which contains the 0.htm file. This htm file should be customized in conformity with your application using Notepad. Furthermore, the Trilogi Supplied JavaScript file M.JS has to be also downloaded and a background graphic file should be created at Paint and saved as *.gif. All this files must be stored in the same folder and then transferred to FileZilla.

When the web page is ready, the LADDER program should be run, the parameters for the airspeed in the web page can be altered and the process is ready to be monitored.

Chapter 4 Results and Discussion

4.1 Results

On the first attempt of getting the fan controlled by the PLC, some wires for feeding the PLC were disconnected, what resulted in a no reply from the PLC. After they being tightened, the fan was not working yet under the commands present in the LADDER program. In order to find out what was wrong in the circuit , a multimeter was used for measuring the voltage in each component on the circuit and a failure on the 5 VDC regulator was detected, which had 24 VDC in its output instead 5 VDC. As this voltage regulator was connected to the Optoisolator, it also was not working, what consequently disturbed the fan operation.

To solve the issue described above, the complete circuit was substituted for a direct supply where instead of using a 12 VDC regulator for the fan and a yellow wire coming from the circuit and connected to the fan, an orange wire coming from PLC’s output 2 connector was connected to 2 100 Ω resistors in series and then connected to the fan’s black connector. Furthermore, the 24 VDC wire coming from the Power Supply which was feeding the PLC directly, was connected to the fan's yellow connector. Once the PLC and fan were wired, the new circuit was tested by clicking on the inputs “Start” and “HighSpeed” at Programmable Logic Simulator and the fan started to work under these commands.

illustration not visible in this excerpt

Figure 6: Circuit used for connecting PLC to the Fan.

For the second test, 4 switches was used instead of the buttons present at Programmable Logic Simulator, for representing each input: Start, Stop, LowSpeed and HighSpeed.

Despite of having no more switches, the input MedSpeed and 3 indicators for Low, Medium and High speed were also included in the Ladder program. As consequence, for having access to these inputs, it was necessary to click on the virtual switch for the desired input at Programmable Logic Simulator.

Below, it is displayed a screen shot of the fan’s Online Monitoring and a video.

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Figure 7: Online Monitoring Screen Shot.

Once the fan is fully working under the PWM pulses control, it is time for testing the Web Based monitoring scheme, starting from connecting the Ethernet cable to the PC's Ethernet port and then to the PLC's Ethernet port. At this time the first aim is to get the Ethernet port configured by clicking on “Network Connection” at Control Panel and going to Ethernet Properties, where the “Protocol Version 4 (TCP/IPv4) needs to be changed by clicking on its properties. At Properties, instead of “Obtaining IP automatically”, it was changed to set the IP address manually, by inserting the same IP address used for the PLC, in this case 192.168.43.231. In addition, the Subnet is set to 255.255.255.0, the gateway is set to 192.168.1.1 and the Fserver Port is set to 9080, which is a default for the Nano 10 PLC.

The next step is to investigate whether the IP address for PLC was set up by typing ping 192.168.43.231 at Command Prompt. After it was done, the Command Prompt returned “Destination Host Unreachable” as a reply. Therefore, it means that the Ethernet Port could not assume this IP address even if it has been changed at Ethernet Properties. The solution for this problem was to investigate the IP addresses in the PC by typing IPCONFIG on the Command Prompt, what displayed the IP address for the Ethernet port, the IPv4 Address, as it is displayed on the figure below.

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Figure 8: Screen Shot of the Command Prompt / IP Configuration.

Therefore, as the IP address for the Ethernet port is 169.254.13.172, the IP address for the PLC was changed to 169.254.13.171. To confirm whether this new IP address for PLC was set up properly, over again it was used the Command Prompt by looking for the IP address 169.254.13.171, what resulted in a positive return which is displayed in the figure below.

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Figure 8: Screen Shot of the Command Prompt / PLC’s IP Address.

In order to establish a connection in the FileZilla client, the IP address at Host space was changed to PLC’s IP address, the Username was set to “samples” , the Port Number space was left blank and the Transfer Mode at Site Manager option was changed to “Active”. After pressing ENTER, a connection was established, though it was kept for only 20 seconds. After this time, a “Time Out” message of inactivity appeared and it was necessary to reconnect.

During the 20 seconds of connectivity at FileZilla, many attempts of transferring the 0.htm file to FileZilla were made with no success, as the file could not be dragged to the directory. Furthermore, even when the FileZilla was supposed to be connected, on the directory area was displayed a “Not Connected to Any Server” message.

To sort out this technical issues, many attempts of connection were made in addition to changes on the parameters, an older FileZilla version was installed and a long time was spent on consulting the Nano 10 Manual in order to overcome the FileZilla's problem. However, even following the standard guidelines to fix the FileZilla's issue, it did not work as expected and the web page could not be created. Consequently, the sensor was not used, as it was supposed to be included when getting the Web Based scheme fully working.

Even though the Web Based monitoring could not be fully implemented, the web page default for Nano 10 PLC was customized and it is displayed below.

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Figure 9: Customized Web Page.

4.2 Discussion

In this project a wind tunnel was built and an investigation was made for checking whether was possible to control a fan by PID control while monitoring its airspeed by Web Based.

This project was split in three relevant tasks to be executed: the Wind Tunnel construction, the PID control implementation and the Web Based monitoring implementation.

The first task was carried out successfully, even facing some problems in its execution as the difficulties for building an aluminum clamp to attach the tube in the frame. After 3 attempts with no success, a ready aluminum clamp was taken instead of constructing one. After this overcoming, the Wind Tunnel construction was finally completed.

The PID control implementation, the second task, was also executed with success. The basic issues faced were related to the circuit developed for connecting the devices, where the 5 VDC regulator was broken, what triggered in non operation of the Optoisolator.

To overcome it, the circuit was substituted by a direct wiring. All inputs were tested and their performance were as the expected.

The third and last task, the Web Based implementation was carried out partially. All the guidelines were followed for getting the web page and then to monitor the process through it. Nevertheless, the FileZilla server was facing several technical issues for connecting and transferring the customized html file, what paralyzed the project in this stage.

Chapter 5 Conclusions and Recommendations

5.1 Conclusions

This paper has proposed and implemented the PID control and the Web Based monitoring applied to a Brushless fan. The fan was perfectly controlled by PLC via PMW pulses, which when had its duty cycle changed, resulted in an alteration on the airspeed performed by the fan, confirming that PID control is really worth, straightforward and reliable.

Although the Web Base monitoring could not be totally implemented, the project was successful in its general execution by increasing technical and theoretical knowledge and opening precedents for future researches in Control and Monitoring area.

5.2 Recommendations

To complete this project by getting everything working as it is supposed to, it would be decisive to have 2 weeks more for implementing only the Web-Based monitoring, as it depends on a server, FileZilla Client, which runs several issues regarding its connection and file transfer. During this extension time, it would be possible to get this issue sorted out by requesting technical help from FileZilla Client developers. For future work, it would be desirable to use a PLC with more inputs, as it would avoid the use of switches, turning the process totally controlled on the web page. Furthermore, more functionalities could be added to the LADDER program, instead of getting the fan working alone, others components could be work synchronously with it.

Lastly, the last proposal is to add a SCADA monitoring that could allow a deeper investigation on the system developed, permitting to monitor it graphically regarding the time that the system takes for executing the airspeed selected, how it responds to a change on the Setpoint or even to an addition of a disturbance.

REFERENCES

[1] NASA, What Are Wind Tunnels? (2014) [online]. Available from: <http://www.nasa.gov/audience/forstudents/k-4/stories/what-are-wind-tunnels- k4.html#.VFkCfvmsVS0> [Accessed on: Sept. 29, 2014].
[2] R.D.Mehta & P.Bradshaw.(1979) Design Rules for Small Low Speed Wind ”, [online]. Available from: Aeronautical Journal of the Royal Aeronautical Society <http://navier.stanford.edu/bradshaw/tunnel/LowSpeedTunnels.pdf> [Accessed on: Sept. 30, 2014].
[3] Triangle Research International, Nano-10 Ladder + Basic Sper PLC User's Manual [online]. Available from < http://www.triplc.com/documents/Nano-10- UserManual.pdf > [Accessed on: Oct. 2, 2014].
[4] Wang Q.G, Lee T.H, Fung H.W, Bi Q. (1999) PID Tuning for Improved Performance [online]. Available from: IEEE Control Systems Society <http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=772161> [Accessed on: Oct. 15, 2014].

Appendix A Project Planning

Salient components of the project planning are described below, and critically evaluated with suggestions for how the project planning could have been improved upon in case significant deviation from original plans had to be accommodated in the project.

- Optoisolator : It could be substituted by a relay. Even though the relays are more robust and slower than the Optoisolators, it would not interfere in the project operation.
- 5 VDC voltage regulator : It should have been tested in a Protoboard before being soldered in the Veroboard. In case of non operation it could be substituted for another IC in advance.
- 12 VDC voltage regulator : It should have been tested in a Protoboard before being soldered in the Veroboard. In case of non operation it could be substituted for another IC in advance.
- Anemometer : It could be substituted by a potentiometer in case of a failure.

Appendix B Design Drawings & Component Specifications

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Figure 12: Previous Wind Tunnel and Its Sensor Attached / Internal View.

DC AXIAL FLOW FAN

The motor fan used for the wind tunnel project will be an AKASA - MH9225H12S- 0.26A DC Brushless fan.

It is a small fan with frame dimensions of 92 mm x 92 mm x 25 mm that will fit properly on the circular entry of the wind tunnel, as its ratio is 50 mm.

Its supply voltage is 12 VDC and its speed range max is 2600 rpm.

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Figure 4 : Brushless Flow Fan Drawing.

NANO PLC Controller

In this project the Nano 10 PLC will be employed. This PLC is thought to be small in measure but with just 10 dig + analog I/O s. Although, despite of its small size, there is a Ethernet port in this device that permits the connection to a network router, switch or hub access to the LAN or to the internet, as the wind tunnel will be monitored by Web Based Monitoring.

As the Nano-10 User Manual says, the Nano-10 PLC has 2 analog inputs (12-bit, 0- 5VDC), 4 digital inputs and 4 digital outputs. All the digital outputs can each supports 4A peak current and 2A continuous current, 24 VDC current from the load and it is taken to output stepper motor pulse/ direction signal or taken as PMW output driver.

The other 2 digital outputs each comprises a pair of voltage - free contacts, permitting switching of two isolated loads of up 5A current per channel (24 VDC/AC or 120 VAC).

Another interesting advantage of using this PLC is that the Nano-10's RS485 port can communicate with Nano-10 CPU if your Ethernet configuration settings are failing and it can not be connected to your network router.

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Figure 18 : Nano 10 Image- From http://www.icc-gb.com/nano.html.

OMRON MEMS Air Velocity Sensor

The air velocity sensor used will be a OMRON MEMS D6F-W01A1/04A1 Air Velocity Sensor. It is a compact anemometer whose dimensions are 39 mm x 20 mm x 9 mm. Its power supply max is 26.4 VDC and min is 10.7 VDC, its max current consumption is 15mA and its repeat accuracy is +/- 5% FSD max, 25°C.

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Figure 19 : Omron Anemometer Sensor Image - From http://www.digikey.com/product-detail/en/D6F-W01A1/Z2631-ND/1277560.

DC Power Supply

A RS POWER SUPPLY UNIT, DIN RAIL, 45W 24V will be used in this project.

This power supply receives a max DC voltage as input of 370 V, its power rating is 48 W and its output current is 2A. Its dimensions is 93 mm x 78 mm x 67 mm. One of its advantages is its integrated protection against short circuit, over voltage, over load and over temperature.

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Figure 20 : RS Power Supply Image - From http://dir.indiamart.com/search.mp?ss=RS+POWER+SUPPLY+UNIT%2C+DIN+RAIL%2C+45 W+24V.

IR3476 SUPLRBuck IC

The power supply will deliver up to 24 VDC to the Brushless fan. However, the input voltage required by the fan is 12 VDC. To decrease the voltage coming from the power supply to the fan it will be added in this project a IR3476 SUPLRBuck DC / DC voltage regulator IC.

It is an integrated component really straightforward to use. Besides, it has a high efficiency in providing a precise voltage output, it is covered by a thermal protection and it is suitable for many different applications.

Its input voltage range is from 3 VDC to 27 VDC, delivering a minimum output voltage of 500m VDC and a maximum of 12 VDC which will be powering the Brushless fan.

Its switching frequency is 750KHz and its Precision Voltage Reference is 0.5V, +/-1%.

Appendix C List of Software Code

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Appendix D Other Technical or Data Appendices

Formulae Sheets are provided below:

C(s) = Kp (Proportional Controller)

[illustration not visible in this excerpt] (Proportional Integrative Controller)

[illustration not visible in this excerpt](Proportional Derivative Controller)

[illustration not visible in this excerpt] Kds (Proportional Integrative Derivative Controller)

[illustration not visible in this excerpt]( Transfer Function in Closed Loop)

[illustration not visible in this excerpt]( Transfer Function in Open Loop for PI Controller)

Appendix E First Material List and Implementation

For implementing the project all materials below will be taken:

-1 Nano 10 PLC ;
-1 PC ;
-1 AKASA - MH9225H12S - 0.26A DC BRUSHLESS FAN, 92 x92 x 25mm, 12V ;
-1 PVC Pipe with 100mm of diameter and 600mm of length ;
-1 OMROM MEMS Air Velocity Sensor ;
-1 Plastic Support with 700 x 300 x 25mm ;
-8 Bolts and 8 Nuts ;
-16 Washers ;
-1 Drilling Machine ;
-1 24 V DC Power Supply ;
-USB Cables ;
-2 Cramps ;
-1 Pliers ;
-1 Thin Wood Stick with 100 mm of length and 20 mm of diameter ;
-1 Hole Saw Kit ;
-1 Fuse for electrical isolation ;
-1 470µF 50 V Electrolytic Capacitor ;
-1UF4001 Diode ;
-1 4N35 Optoisolator ;

In the wind tunnel construction, the cooler was removed from the frame and a circular hole was cut off from the PVC lid using the hole saw kit and the drilling machine, with the same diameter than the cooler. The next step was to relocate the cooler inside the frame, put it like a model over the PVC lid, making 4 holes in it by using the drilling machine. For finally fixing the fan to the PVC tube, bolts, nuts and washers were put in the holes for holding the fan to the PVC lid. In order to place the sensor on the test section, the sensor was fix to the wood stick by putting bolts, nuts and washers on it . Once getting the sensor attached to the stick, it was fixed to the wind tunnel walls by putting bolts, nuts and washers.

To join the wind tunnel to the plastic base, 2 clamps were taken. The clamps were fixed in the wind tunnel and holes were made in the clamp tips, joining it to the plastic base, and finally ending it up by putting 4 holes 4 bolts, 4 nuts and 4 washers on these holes.

For testing the wind tunnel the power supply is connected to the fuse before plugging it to the power. After the Nano 10 PLC and the sensor are ready to be connected to the 24V DC power supply.

The connection between the Nano 10 PLC to the power supply can not be directly. Instead, to avoid that reverse current flows back to the power supply and to avoid undesirable voltage glitches from conducting into the PLC, the 470 µF electrolytic capacitor is connected between the PLC and the power supply and a diode is connected before the capacitor.

45 of 45 pages

Details

Title
Controlling and Monitoring Air Speed in a Wind Tunnel
Course
Bachelor of Engineering (Honours) in Mechatronics
Author
Year
2015
Pages
45
Catalog Number
V300143
ISBN (Book)
9783656972204
File size
899 KB
Language
English
Tags
Wind Tunnel, Web Based Monitoring, PLC, PID, Fan, Anemometer
Quote paper
Manuela Gomes (Author), 2015, Controlling and Monitoring Air Speed in a Wind Tunnel, Munich, GRIN Verlag, https://www.grin.com/document/300143

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