Single-Board-Heater-System/C2/Implementing-Proportional-Controller-on-SBHS-remotely/English-timed

Time	Narration
00:01	Welcome to the spoken tutorial on Implementing proportional controller on SBHS remotely.
00:09	In this tutorial, we will learn to: * Use Ziegler-Nichols tuning method to calculate proportional controller gain
00:18	* Modify step test code to design a proportional controller
00:22	* Implement this proportional controller on SBHS.
00:26	Ensure that Scilab is installed on your computer.
00:30	Also, ensure that you have internet connectivity before you begin with this tutorial.
00:36	I am recording this tutorial on a Windows 7, 32-bit Operating System.
00:41	As a pre-requisite, watch the tutorial on Using SBHS Virtual labs on Windows OS.
00:48	This tutorial is available on the Spoken Tutorial website.
00:53	It will teach you how to do a basic step test experiment on SBHS, remotely.
01:00	You also need to have basic knowledge of PID tuning.
01:05	You should have the step test experiment code folder available with you.
01:10	You should also have the step test experiment data file with you.
01:15	If not, then it is recommended that you re-do the step test experiment and generate a new data file.
01:23	In my machine, the data file is within the Scilab_codes_windows folder >> step test folder >> logs folder.
01:35	Here is a folder with my username and here is my data file.
01:41	Let us now download the Analysis code from the website.
01:46	Open a web browser and go to the web site: sbhs dot os hyphen hardware dot in.
01:55	On the left hand side, click on Downloads.
02:00	Download the file SBHS Analysis Code and save it on the Desktop.
02:09	Here it is! The file downloaded will be in a zip format.
02:14	Right-click and extract the contents of the zip file.
02:19	A folder named Scilab codes analysis will be created.
02:25	Open this folder.
02:27	Locate and open the folder Step Analysis.
02:32	The Step Analysis folder will have few more folders.
02:36	Copy-paste the data file generated earlier inside the Kp tau order1 folder.
02:50	Double-click on the Scilab file firstorder.
02:55	This will launch Scilab automatically and will also open the file in Scilab editor.
03:02	If it doesn't open the file, click on the File menu and then on Open a file.
03:09	Choose the file firstorder and click on Open.
03:18	Locate the variable filename and change its value to the filename of your data file.
03:27	I will copy-paste the filename to avoid spelling mistakes.
03:34	Keep the ".txt" extension.
03:37	Save and execute this Scilab code.
03:42	If the data file is not corrupted and there are no errors, a plot window will open.
03:48	This plot window will show two graphs, the SBHS temperature plot which has noise and output of the SBHS first order model which is a smooth curve.
04:05	This code basically does the job of fitting a first order transfer function using the data file.
04:12	The values of time constant tau and gain Kp are displayed on the top.
04:19	In this tutorial, we will not use the first order transfer function.
04:23	We will only use the plot of the SBHS output.
04:26	Switch to the Scilab editor.
04:29	Locate the line plot2d of t comma y underscore prediction.
04:37	We don't want the prediction output to appear on the plot.
04:41	Comment out this line by putting two forward slashes at the beginning of the line.
04:48	Save and execute the Scilab code.
04:52	Switch to the plot window.
04:54	Notice that the plot window now has only the SBHS temperature plot.
05:00	To save this image, click on the File menu.
05:04	Then choose Export to option.
05:07	Give a name to the image file. I will type sbhsplot.
05:14	Click on the drop-down menu for Files of type and choose PNG.
05:22	Choose the directory where you want to save this file.
05:27	I will choose Desktop and click on Save.
05:31	Let us open and see if the image file is created on the Desktop.
05:36	Here it is!
05:39	Close this image window.
05:42	Let me now switch to the slides.
05:45	Let us calculate the value of proportional gain using Ziegler-Nichols tuning method.
05:52	There are two tuning rules given by Ziegler-Nichols to calculate the PID parameters. These are Reaction curve method and Instability method.
06:03	We will see the Reaction curve method.
06:06	In this method, a step input is given to the system and its output is observed over a period of time.
06:13	Any practical system would respond exponentially to a step input.
06:18	A tangent is drawn at the point of inflection
06:22	that is, when the curve changes from convex to concave.
06:27	The dead time and time constant are calculated from the time axis.
06:33	This is illustrated in this figure. This is the tangent line drawn at the point of inflection .
06:41	'K' is the gain of the system,
06:45	'L' is the dead time and
06:48	'T' is the time constant.
06:50	Replicate this on the SBHS output figure which is saved on the Desktop.
06:56	I have already done this.
06:58	Let me open this file.
07:01	I have used paint brush which is a default image editing tool on Windows.
07:08	I have got the values of gain equal to 2.7, dead time equal to 1 second and time constant equal to 50 seconds.
07:18	Note that these are all approximate values.
07:22	The values depend on the accuracy with which you draw the tangent line at the inflection point.
07:30	After you get the required values, refer to the table given by Ziegler-Nichols to calculate the value of proportional gain.
07:39	For a proportional controller, we need to calculate only the value of proportional gain.
07:44	In my case, the value of proportional gain comes out to be 18.
07:50	Now, let us see how to implement the proportional controller on SBHS.
07:56	We would modify the step test code for this.
07:59	Switch to the folder where you have the step test code.
08:03	Here it is. Make a copy of this folder.
08:08	Rename this folder as proportional and open it.
08:14	Rename the stepc file to proportional.
08:19	Rename the steptest dot sci file to proportional.
08:24	Rename the steptest dot xcos file to proportional.
08:29	Close Scilab, if already running.
08:33	Double-click on the proportional dot sce file.
08:38	This should launch Scilab automatically and also open the file in Scilab editor.
08:43	If it doesn't open the file, click on the File menu, and then on Open a file.
08:50	Choose the file proportional and click on Open.
08:56	Change the exec command to execute proportional.sci file, instead of steptest.sci file.
09:06	Change the xcos command to execute the proportional.xcos file, instead of steptest.xcos file.
09:16	Save this file.
09:18	Click on the File menu and choose Open.
09:22	Select the file proportional.sci and click on Open.
09:28	Change the function name from steptest to proportional.
09:33	Delete the input variable heat from the proportional function input and type setpoint.
09:42	In the next line, type global, leave a space and then type temp and press Enter.
09:51	In the next line, type: err equal to setpoint minus temp.
10:00	Add semicolon at the end and press Enter.
10:05	In the next line, type: heat equal to 18 multiplied by err. Add a semicolon at the end.
10:17	Here, 18 is the value of the proportional gain for my SBHS.
10:22	You may change it according to what you would have calculated for your SBHS.
10:28	Add setpoint in the input variable of the plotting function , inside its function call.
10:36	To do so, add a space after temp and type setpoint.
10:43	Save this file.
10:45	Switch to the Scilab console. Type xcos and press Enter.
10:52	xcos window will open.
10:55	Close the palette window.
10:58	On the xcos untitled window, click on File menu and choose Open.
11:05	Browse to the proportional directory.
11:08	Select proportional.xcos and click on Open.
11:13	Xcos file will open.
11:15	Double-click on the label Heat input in percentage.
11:20	Delete it and type setpoint.
11:24	Click once anywhere on the xcos window to save the label.
11:29	Double-click on the step input block to open its Properties window.
11:34	Change the Initial Value to 30 and Final Value to 40.
11:40	Keep Step time as 300. Click on Ok.
11:45	Double-click on the function block. A window will appear. Click on OK.
11:53	Another window will appear.
11:55	Here, there is an option to enter the function name to be called by this xcos block.
12:02	Change the function name from step test to proportional. Click on Ok.
12:09	Another window will open.
12:11	Keep clicking on Ok three times to finish the configuration of function block.
12:18	Save the 'xcos' diagram and close it.
12:22	Close the xcos untitled window as well.
12:25	Switch to the web browser.
12:27	On the left hand side, click on Virtual labs.
12:32	Login with your registered username and password. Book a slot.
12:42	Switch to the proportional folder. Double-click on the file run.
12:48	This will open the SBHS client application.
12:53	Login with your username and password. Make sure you are logging in at the booked slot time.
13:02	Expect the message "Ready to execute Scilab code".
13:06	Switch to the Scilab console.
13:08	Type: get d space dot dot slash common files. Press Enter.
13:17	Switch to the Scilab editor. Execute the file proportional.sce.
13:25	If the network is fine, then it will automatically open the xcos window with a proportional controller xcos diagram.
13:34	Execute this xcos diagram and expect a plot window.
13:41	The plot window will have three plots heat, fan, temperature.
13:47	Setpoint will also be plotted in the temperature graph.
13:52	Observe that the proportional controller computes the value of heat in order to achieve the setpoint value of temperature.
14:02	Run this experiment long enough to observe what happens after a step change in setpoint occurs.
14:10	I will now pause this recording until the experiment is executed for sufficient time.
14:16	You can see that the proportional controller has responded to the change in the setpoint.
14:23	You can observe that the proportional controller inherently has the property of offset.
14:29	A proportional controller will always have an offset between the setpoint value and the actual value.
14:36	Now, let us summarize. In this tutorial, we learnt to- * Use Ziegler-Nichols tuning method to calculate proportional controller gain for SBHS
14:47	* Modify step test code to design a proportional controller
14:51	* Implement the designed proportional controller on SBHS.
14:56	Watch the video available at the following link. It summarises the Spoken Tutorial project.
15:02	If you do not have good bandwidth, you can download and watch it.
15:06	The Spoken Tutorial project team: * Conducts workshops using spoken tutorials.
15:10	* Gives certificates to those who pass an online test.
15:14	For more details, please write to: contact at spoken-tutorial.org
15:21	Spoken Tutorial project is a part of the Talk to a Teacher project.
15:25	It is supported by the National Mission on Education through ICT, MHRD, Government of India.
15:31	More information on this mission is available at: [1]
15:42	Thanks for joining. This is Rupak Rokade from IIT Bombay, signing off. Thank You.

Contributors and Content Editors

Nancyvarkey, PoojaMoolya, Sandhya.np14