Help very much needed

[chat2]

Hi guys

I recently got a labview assignment to create for school.  The problem is, i have no previous experience with labview and i'm really unfamiliar with the way it works.  If anyone could help me out and sorta help me figure it out, i would greatly appreciate it.  This should be a relatively simple task for someone with labview knowledge and know how. 

Here is the assignment:

You must download the program from WebCT (“Exothermic Reaction.vi”). The reactor vessel illustrated in the front panel contains an exothermic chemical reaction. The amount of heat produced is proportional to the reaction rate.  The reaction rate at a given temperature can be calculated from the Arrhenius equation:

 Run the program and notice that the temperature increases exponentially since the reaction creates heats, which increases the reaction rate, which produces even more heat.

A water jacket has been placed around the reactor to control the temperature of the reactor.  By flowing cold water to the outside of the jacket, you can remove heat that is produced.  You must program a controller for which set the level of the cold water valve to keep the temperature constant at 50 degC. 

Output your results to charts showing the tank temperature vs, time and valve position.  As well, plot dT/dt and d(error)/dt.

This is what is called a feedback system.  You know the set point you want and you adjust your inputs. 

You need to use a proportional controller.  Hint: Calculates the error (where error = set point - current value) and then makes a proportional change to (new valve setting = old valve setting + constant * error).  Also note, if your error is positive or negative this will open or close you valve automatically.  So when you error is large, you will open a lot and when your error is small, you open a little.  You find your proportionality constant (k) by trial and error. 

Please submit your program as a mini lab report.  The written report must include

1)    Introduction

2)    Background Include the basic principle of feedback and include information on what a PID controller is (1/2 to 1 page).  You can use the internet to find some information.  Do not copy and paste from a website (that is plagiarism and I will report you to the Faculty Disciplinary Officer).  The TA is not going to give you this information, you need to research control theory a bit yourself.

3)    Results;

–      Show your block diagram and front panel.

–      Explanation your program and the way it works.  If not it will be difficult for the TA to follow.  Explain each calculation in the program in terms of plain language.

4)    Discussion;

–      How well does your program control temperature (what is your max ΔT or ΔH).

–      How long does it take to reach and stay at the set point?

–      Try changing you proportionality constant and you can make it reach steady state much quicker or slower.  Plot time to reach steady state vs k.  What happens if you try and go too quickly?

–      What are the advantages of proportional control?  What would you gain if you used integral or derivative control?

[chat2]

Here is the program by the way

[chat2]

Arrhenius equation: k = Ae^(-Ea/RT)

[smercurio_fc]

Well, we're not goign to do your homework for you, but we can offer advice. If anyone on here starts giving you code I will personally kick their behind.

As for your project: have you done any research on control theory, specific to PID controllers? It seems to me that's where you need to start. If you don't know the concept and the application, it will not be possible for you to write code in any language. So, separate the problem into 2 parts: theory and application of PID controllers, and LabVIEW coding. The former you can do by sitting down and doing as the assignment suggests: research. The latter can be done by going through some LabVIEW tutorials. To learn more about LabVIEW it is recommended that you go through the introduction material, tutorial(s), and other material in the NI Developer Zone's Learning Center which provides links to other materials and other tutorials. You can also take the online courses for free.

Post back once you've learned some information.

[smercurio_fc]

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@chat2 wrote:

Here is the program by the way

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Did you write that program? What does it do? As the assignment indicates, explain what it does and how it works.

[smercurio_fc]

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@chat2 wrote:

Arrhenius equation: k = Ae^(-Ea/RT)

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And this tells me? ....

[chat2]

I did not write the program, it's given in the assignment.  All the description i have is described.  Also i just listed the arrhenius equation simply because it was not given in the description.

Thanks

[chat2]

The research isn't the problem, i just listed the assignment as a whole, i obviously intend to do the write up myself.  However, actual application of the program is what i'm having trouble with, I am completely unfamiliar with the basics.

[Z'atari]

The code you sent, is that something you created, or was that given to you by the teacher?

So K is the rate constant of chemical reaction? How is it increasing your Temperature, from the VI you sent, it looks like you are adding T_0+k to get T_1, is that correct?

At the end of the day, given that you have a certain differential equation, you need to use some Eulerian method or some sort of first order numeric method to get T(n+1) from T(n), in LV these kind of simulations are best done in CD&Sim (control design and simulation toolkit). 

However, can you tell us what school grade this assignment is for? and most importantly can you share with us your model or equations that allow temperature at state N to become Temperature at state N+1, you could do this straight in LV by using shift registers.