Difference between revisions of "OpenModelica/C2/Developing-an-equation-based-model/English-timed"

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(Created page with "{| border=1 ||''' Time ''' ||'''Narration''' |- ||00:01 ||Welcome to the spoken tutorial on '''Developing an equation based model'''. |- || 00:06 || In this tutorial, we are...")
 
 
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|-
 
|-
 
||00:01
 
||00:01
−
||Welcome to the spoken tutorial on '''Developing an equation based model'''.
+
||Welcome to the '''spoken tutorial''' on '''Developing an equation based model'''.
  
 
|-
 
|-
 
|| 00:06
 
|| 00:06
−
|| In this tutorial, we are going to learn: How to create a textual model in '''OMEdit''' and simulate it.
+
|| In this tutorial, we are going to learn:
 +
how to create a textual model in '''OMEdit''' and '''simulate''' it,
 
   
 
   
 
|-
 
|-
 
|| 00:14
 
|| 00:14
−
||How to declare variables and equations.
+
||how to declare '''variable'''s and equations,
 
   
 
   
 
|-
 
|-
 
|| 00:17
 
|| 00:17
−
||How to use '''Simulation Setup''' toolbox.
+
||how to use '''Simulation Setup''' toolbox.
  
 
|-
 
|-
 
|| 00:21
 
|| 00:21
−
|| To record this tutorial, I am using  '''OpenModelica 1.9.2 ''' and '''Ubuntu Linux Operating System 14.04'''
+
|| To record this tutorial, I am using  '''OpenModelica 1.9.2 ''' and '''Ubuntu Linux Operating System 14.04'''.
  
 
|-
 
|-
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|-
 
|-
 
|| 00:48
 
|| 00:48
−
|| Let us simulate the motion of a ball of mass ''''m'''', which is under '''free fall due to gravity'''.
+
|| Let us simulate the motion of a ball of mass ''''m'''' which is under free fall due to gravity.
  
 
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|-
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|-
 
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|| 01:10
 
|| 01:10
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||Variables directed away from the surface of Earth, are considered positive.
+
||Variables directed away from the surface of earth are considered positive.
  
 
|-
 
|-
 
|| 01:16
 
|| 01:16
−
|| The '''equations of motion''' for a freely falling body, are as follows:'''dh/dt = v''' , '''dv/dt = g'''
+
|| The equations of motion for a freely falling body are as follows:
 +
'''dh/dt = v''', '''dv/dt = g'''
  
 
|-
 
|-
 
|| 01:27
 
|| 01:27
−
||The value of '''h''' at time '''t = 0''' is '''30''' m and the value of '''v''' at time '''t = 0''' is '''0'''.
+
||The value of '''h''' at time '''t = 0''' is '''30''' meters and the value of '''v''' at time '''t = 0''' is '''0'''.
  
 
|-
 
|-
 
|| 01:37
 
|| 01:37
−
|| Now let me go to '''OMEdit'''. I have already launched it on my system.
+
|| Now, let me go to '''OMEdit'''. I have already launched it on my system.
  
 
|-
 
|-
 
||01:43
 
||01:43
−
|| To open '''OMEdit '''on '''Ubuntu Linux Operating System''', click on '''Dash Home '''icon, which appears at the top left, in '''launcher'''.  
+
|| To open '''OMEdit '''on '''Ubuntu Linux Operating System''', click on '''Dash Home '''icon which appears at the top left, in '''launcher'''.  
  
 
|-
 
|-
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|-
 
|-
 
||01:59
 
||01:59
−
||On clicking '''OMEdit''' icon, you see a window such as this.
+
||On clicking '''OMEdit''' icon, you see a '''window''' such as this.
  
 
|-
 
|-
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|-
 
|-
 
|| 02:09
 
|| 02:09
−
||'''OMEdit''' by default, opens in the '''"Welcome perspective"'''
+
||'''OMEdit''' by default, opens in the '''"Welcome perspective"'''.
  
 
|-
 
|-
 
|| 02:14
 
|| 02:14
−
|| At the bottom right-hand corner, you can locate buttons for '''‘Welcome’, ‘Modeling’''' and '''‘Plotting’ perspectives'''.
+
|| At the bottom right-hand corner, you can locate buttons for '''‘Welcome’, ‘Modeling’''' and '''‘Plotting’''' perspectives.
  
 
|-
 
|-
 
|| 02:23
 
|| 02:23
−
|| click on''' ‘Modeling perspective’'''.
+
|| click on''' ‘Modeling’''' perspective.
  
 
|-
 
|-
 
||02:26
 
||02:26
−
||'''‘Modeling perspective’''' has now opened.
+
||'''‘Modeling’''' perspective has now opened.
  
 
|-
 
|-
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|-
 
|-
 
|| 02:51
 
|| 02:51
−
||We will learn more about these buttons, as we go along.
+
||We will learn more about these buttons as we go along.
  
 
|-
 
|-
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|-
 
|-
 
|| 03:02
 
|| 03:02
−
||Please download this file and save it on your system.
+
||Please download this file and '''save''' it on your system.
  
 
|-
 
|-
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|-
 
|-
 
|| 03:24
 
|| 03:24
−
|| You may also use the tool named '''Open Model/Library File''', that my cursor is pointing to, for opening a file.
+
|| You may also use the tool named '''Open Model/Library File''' that my cursor is pointing to, for opening a file.
  
 
|-
 
|-
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|-
 
|-
 
|| 03:39
 
|| 03:39
−
||'''Libraries Browser''' shows all '''classes''' that are loaded in a session of '''OMEdit'''.
+
||'''Libraries Browser''' shows all '''classes''' that are '''load'''ed in a session of '''OMEdit'''.
  
 
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|-
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|-
 
|-
 
||04:43
 
||04:43
−
|| A dialog box pops up, as shown.  
+
|| A dialog box pops up as shown.  
  
 
|-
 
|-
 
|| 04:46
 
|| 04:46
−
||In the '''Name''' field of this dialog box, type '''freeFall'''.  
+
||In the '''Name''' field of this dialog box, type: '''freeFall'''.  
  
 
|-
 
|-
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|-
 
|-
 
||05:20
 
||05:20
−
||Let me delete '''annotation section'''.  
+
||Let me delete '''annotation''' section.  
  
 
|-
 
|-
 
|| 05:23
 
|| 05:23
−
|| Now, you may type the required information here and save this '''class'''.
+
|| Now, you may type the required information here and '''save''' this '''class'''.
  
 
|-
 
|-
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|-
 
|-
 
|| 05:36
 
|| 05:36
−
|| Choose an appropriate location for this file and save it.
+
|| Choose an appropriate location for this file and '''save''' it.
  
 
|-
 
|-
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|-
 
|-
 
|| 05:47
 
|| 05:47
−
||So switch to '''freeFall class'''.
+
||So, switch to '''freeFall''' class.
  
 
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|-
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|-
 
|-
 
|| 06:05
 
|| 06:05
−
|| Every '''class''' must have an '''end statement''' to indicate where the '''class''' ends.
+
|| Every '''class''' must have an '''end''' statement to indicate where the '''class''' ends.
  
 
|-
 
|-
 
|| 06:11
 
|| 06:11
−
|| This '''class '''has '''variable declarations '''and '''equations'''.  
+
|| This '''class '''has '''variable declarations '''and equations.  
  
 
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|-
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|-
 
|-
 
||06:25
 
||06:25
−
||'''start''' is an attribute of '''Real variable'''.
+
||'''start''' is an attribute of '''Real''' variable.
  
 
|-
 
|-
 
|| 06:29
 
|| 06:29
−
|| Every '''data-type''' has certain attributes, which specify useful information related to '''variables'''.
+
|| Every '''data-type''' has certain attributes which specify useful information related to '''variables'''.
  
 
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|-
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|-
 
|-
 
|| 06:45
 
|| 06:45
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|| '''unit attribute''' specifies the unit of a '''variable'''.  
+
|| '''unit''' attribute specifies the unit of a '''variable'''.  
  
 
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|-
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|-
 
|-
 
|| 06:52
 
|| 06:52
−
|| Every '''variable declaration''' must end with a '''semi-colon.'''
+
|| Every variable declaration must end with a semi-colon.
  
 
|-
 
|-
 
||06:57
 
||06:57
−
|| '''v''' represents '''velocity''' of ball. It is of '''Real data-type.'''
+
|| '''v''' represents '''velocity''' of ball. It is of '''Real''' data-type.
  
 
|-
 
|-
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|-
 
|-
 
|| 07:09
 
|| 07:09
−
|| '''g'''represents '''acceleration due to gravity'''. It is of '''Real data-type.''' And its unit is '''meter per second square.'''
+
|| '''g''' represents acceleration due to gravity. It is of '''Real''' data-type.  And its unit is '''meter per second square.'''
  
 
|-
 
|-
 
|| 07:18
 
|| 07:18
−
|| '''parameter''' is a quantity that remains constant in a simulation run.
+
|| '''parameter''' is a quantity that remains constant in a '''simulation run'''.
  
 
|-
 
|-
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|-
 
|-
 
|| 07:42
 
|| 07:42
−
||'''Comments '''provide useful information about the program. They are also useful for documentation.  
+
||'''Comments '''provide useful information about the program. They are also useful for '''documentation'''.  
  
 
|-
 
|-
 
|| 07:49
 
|| 07:49
−
|| Now, let me go back to the slides.
+
|| Now, let me go back to the '''slide'''s.
  
 
|-
 
|-
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|-
 
|-
 
|| 07:57
 
|| 07:57
−
||'''Real, Integer, Boolean''' and''' String data-types''' are supported in '''Modelica'''.  
+
||'''Real, Integer, Boolean''' and''' String''' data-types are supported in '''Modelica'''.  
  
 
|-
 
|-
 
||08:03
 
||08:03
−
||'''start''' and '''unit attributes''' have already been defined.
+
||'''start''' and '''unit''' attributes have already been defined.
  
 
|-
 
|-
 
|| 08:07
 
|| 08:07
−
||'''min attribute''' specifies the minimum value of a '''variable'''.  
+
||'''min''' attribute specifies the minimum value of a '''variable'''.  
  
 
|-
 
|-
 
|| 08:10
 
|| 08:10
−
||Similarly, '''max attribute''' specifies the maximum value of a '''variable'''.  
+
||Similarly, '''max''' attribute specifies the maximum value of a '''variable'''.  
  
 
|-
 
|-
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|-
 
|-
 
|| 08:19
 
|| 08:19
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|| '''‘equation’ '''signifies the beginning of '''equation section''' of a '''class'''.
+
|| '''‘equation’ '''signifies the beginning of equation section of a '''class'''.
  
 
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|-
 
|-
 
|| 08:30
 
|| 08:30
−
|| The two '''equations of motion''' for a freely falling body, as we have already discussed, have been included here.
+
|| The two equations of motion for a freely falling body, as we have already discussed, have been included here.
  
 
|-
 
|-
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|-
 
|-
 
|| 08:52
 
|| 08:52
−
|| Every '''equation''' must end with a '''semi-colon'''.
+
|| Every equation must end with a semi-colon.
  
 
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|-
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|-
 
|-
 
||09:24
 
||09:24
−
||Note that there are columns named '''Unit''' and '''Description'''.
+
||Note that there are '''column'''s named '''Unit''' and '''Description'''.
  
 
|-
 
|-
 
|| 09:29
 
|| 09:29
−
||'''Unit''' column specifies '''units''' of '''variables,''' as defined using '''Unit''' attribute.  
+
||'''Unit''' column specifies '''units''' of variables as defined using '''Unit''' attribute.  
  
 
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|-
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|-
 
|-
 
||09:51
 
||09:51
−
||This generates the plot of '''h with respect to time''' -with '''h''' on '''y-axis''' and '''time''' on the '''x-axis'''
+
||This generates the plot of '''h''' with respect to '''time''' -with '''h''' on '''y-axis''' and '''time''' on the '''x-axis'''
  
 
|-
 
|-
 
||10:01
 
||10:01
−
||By default, the simulation is run from 0 to 1 unit of time.  
+
||By default, the simulation is '''run''' from 0 to 1 unit of time.  
  
 
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|-
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|-
 
|-
 
|| 11:33
 
|| 11:33
−
||But, the value of '''h''' has gone below zero, which is unacceptable.
+
||But, the value of '''h''' has gone below zero which is unacceptable.
  
 
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|-
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|-
 
|-
 
|| 12:11
 
|| 12:11
−
||Now, let me delete the first '''equation''' and simulate this '''class''', to see what happens.
+
||Now, let me delete the first '''equation''' and simulate this '''class''' to see what happens.
  
 
|-
 
|-
 
||12:18
 
||12:18
−
|| I have deleted the first '''equation'''.
+
|| I have deleted the first equation.
  
 
|-
 
|-
 
|| 12:21
 
|| 12:21
−
||Notice that a star appears beside the name of the '''class''' in '''freeFall''' tab.  
+
||Notice that a star appears beside the name of the '''class''', in '''freeFall''' tab.  
  
 
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|| 12:44
 
|| 12:44
−
||You may also use the '''Save''' button in '''toolbar''', which my cursor points to, to save a file.
+
||You may also use the '''Save''' button in '''toolbar''' which my cursor points to, to save a file.
  
 
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|-
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|-
 
|| 12:59
 
|| 12:59
−
|| Note that an error message pops up in the '''Messages browser'''.  
+
|| Note that an '''error message''' pops up in the '''Messages browser'''.  
  
 
|-
 
|-
 
|| 13:04
 
|| 13:04
−
||It says, there are too few equations and the model has 1 '''equation''' and 2 '''variables'''.  Hence this cannot be simulated.
+
||It says: there are too few equations and the model has 1 '''equation''' and 2 '''variables'''.  Hence this cannot be simulated.
  
 
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|-
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|| 13:48
 
|| 13:48
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||There is no data flow direction for '''equations'''.
+
||There is no data flow direction for equations.
  
 
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|| 14:00
 
|| 14:00
−
||'''Initial equations section''' is used to enter initial conditions.
+
||'''Initial equations''' section is used to enter initial conditions.
  
 
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|| 14:10
 
|| 14:10
−
|| As an assignment, write a '''model''' to simulate the '''differential equation''' '''dx/dt = -a  into x ''' , where '''a = 1''',  '''x''' belongs to '''R'''  and the value of x at time '''t=0''' is '''5'''
+
|| As an assignment, write a '''model''' to simulate the '''differential equation, dx/dt = -a  into x ''' , where '''a = 1''',  '''x''' belongs to '''R'''  and the value of x at time '''t=0''' is '''5'''.
  
 
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|| 14:31
 
|| 14:31
−
|| Watch the video at the following link.  It summarizes the Spoken Tutorial project.
+
|| Watch the video at the following link.  It summarizes the '''Spoken Tutorial''' project.
  
 
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|| 14:43
 
|| 14:43
−
|| '''Spoken Tutorial project''' is funded by NMEICT, MHRD, Government of India.
+
|| '''Spoken Tutorial project''' is funded by '''NMEICT, MHRD,''' Government of India.
  
 
|-
 
|-

Latest revision as of 15:22, 16 August 2019

Time Narration
00:01 Welcome to the spoken tutorial on Developing an equation based model.
00:06 In this tutorial, we are going to learn:

how to create a textual model in OMEdit and simulate it,

00:14 how to declare variables and equations,
00:17 how to use Simulation Setup toolbox.
00:21 To record this tutorial, I am using OpenModelica 1.9.2 and Ubuntu Linux Operating System 14.04.
00:32 But, this process is identical in Windows, Mac OS X or FOSSEE OS on ARM.
00:40 To understand this tutorial, you need to know equation-based modeling of physical systems.
00:48 Let us simulate the motion of a ball of mass 'm' which is under free fall due to gravity.
00:54 The height of the ball from the surface of Earth is represented by variable h.
00:59 The velocity of the ball is represented by variable v.
01:04 Acceleration due to gravity is represented by g and is assumed to be constant.
01:10 Variables directed away from the surface of earth are considered positive.
01:16 The equations of motion for a freely falling body are as follows:

dh/dt = v, dv/dt = g

01:27 The value of h at time t = 0 is 30 meters and the value of v at time t = 0 is 0.
01:37 Now, let me go to OMEdit. I have already launched it on my system.
01:43 To open OMEdit on Ubuntu Linux Operating System, click on Dash Home icon which appears at the top left, in launcher.
01:53 Type OMEdit in the search bar.
01:56 Click on the OMEdit icon.
01:59 On clicking OMEdit icon, you see a window such as this.
02:06 This window is known as "Welcome perspective".
02:09 OMEdit by default, opens in the "Welcome perspective".
02:14 At the bottom right-hand corner, you can locate buttons for ‘Welcome’, ‘Modeling’ and ‘Plotting’ perspectives.
02:23 click on ‘Modeling’ perspective.
02:26 ‘Modeling’ perspective has now opened.
02:29 I will be referring to the area between Libraries Browser on the left, Messages Browser at the bottom and Toolbar on the top, as the modeling area.
02:41 The toolbar has buttons related to file operations, graphical view and simulation.
02:51 We will learn more about these buttons as we go along.
02:55 Now, we shall use ‘freeFall’ class file provided in the Code Files link on our Spoken Tutorial webpage.
03:02 Please download this file and save it on your system.
03:07 To open this class, go to the File menu in Menu bar.
03:13 Click on Open Model/Library File
03:17 Locate freeFall file that you downloaded and saved on your system and open it.
03:24 You may also use the tool named Open Model/Library File that my cursor is pointing to, for opening a file.
03:34 Note that freeFall icon appears in the Libraries Browser.
03:39 Libraries Browser shows all classes that are loaded in a session of OMEdit.
03:45 Right click on freeFall icon and select View Class.
03:52 The class has now opened in Diagram view.
03:56 Do not worry if the class does not open in Diagram view.
04:00 I shall show you how to switch between different views.
04:04 Go to the top of Modeling area.
04:07 Note that the second button stands for Diagram view.
04:10 Third button is Text View.
04:13 Click on it to switch to Text View.
04:17 The class has now opened in Text view.
04:20 Note that the first button stands for Icon View.
04:24 We will learn more about Icon view and Diagram view later on.
04:29 You may also create a new class named freeFall and type the required information.
04:36 To create a new class, go to File menu.
04:40 Select New Modelica Class.
04:43 A dialog box pops up as shown.
04:46 In the Name field of this dialog box, type: freeFall.
04:51 I am using a different name freeFall1 since freeFall class is already open in OMEdit.
04:58 Note that two classes cannot have the same name.
05:03 Click on Specialization drop-down menu. Select Class. Click on Ok.
05:10 A new class has been created.
05:13 You may also use the tool named New Modelica class to open a new class.
05:20 Let me delete annotation section.
05:23 Now, you may type the required information here and save this class.
05:29 To save this class, go to File menu in Menu bar and click on Save.
05:36 Choose an appropriate location for this file and save it.
05:41 Now, let us understand the syntax of Modelica using freeFall class.
05:47 So, switch to freeFall class.
05:49 Go to top of Modelling area. Click on freeFall tab.
05:54 Programs in Modelica are arranged in the form of classes.
05:58 The first line of a class defines its name.
06:02 The name of this class is freeFall.
06:05 Every class must have an end statement to indicate where the class ends.
06:11 This class has variable declarations and equations.
06:15 Let me show you how to declare variables.
06:18 Real represents data-type.
06:21 h represents height of ball from surface of Earth.
06:25 start is an attribute of Real variable.
06:29 Every data-type has certain attributes which specify useful information related to variables.
06:36 start attribute specifies the initial value of a variable.
06:41 The initial value of h is 30 units.
06:45 unit attribute specifies the unit of a variable.
06:49 The unit of h is metre.
06:52 Every variable declaration must end with a semi-colon.
06:57 v represents velocity of ball. It is of Real data-type.
07:02 The initial value of v is zero. Its unit is meter per second.
07:09 g represents acceleration due to gravity. It is of Real data-type. And its unit is meter per second square.
07:18 parameter is a quantity that remains constant in a simulation run.
07:24 The value of g remains constant throughout the simulation run, with a value of 9.81.
07:32 The negative sign is due to sign convention used.
07:36 The text in double quotes is a comment written with the declaration of g.
07:42 Comments provide useful information about the program. They are also useful for documentation.
07:49 Now, let me go back to the slides.
07:52 parameter is a quantity that remains constant in a simulation run.
07:57 Real, Integer, Boolean and String data-types are supported in Modelica.
08:03 start and unit attributes have already been defined.
08:07 min attribute specifies the minimum value of a variable.
08:10 Similarly, max attribute specifies the maximum value of a variable.
08:16 Let me go back to OMEdit.
08:19 ‘equation’ signifies the beginning of equation section of a class.
08:25 This is an alternative way of inserting comments.
08:30 The two equations of motion for a freely falling body, as we have already discussed, have been included here.
08:38 der() is Modelica function for time derivative.
08:43 Hence, der(h) represents dh/dt.
08:48 And der(v) represents dv/dt.
08:52 Every equation must end with a semi-colon.
08:57 Let me show you how to simulate this class.
09:00 Click on simulate button in the toolbar.
09:04 Close the pop-up window.
09:07 This window is known as the Plotting perspective.
09:11 On successful simulation of a class, Plotting perspective opens automatically.
09:17 Variables browser displays information related to variables and parameters of a class.
09:24 Note that there are columns named Unit and Description.
09:29 Unit column specifies units of variables as defined using Unit attribute.
09:37 Description column displays comments written in double quotes with variable declarations.
09:45 Let me show you how to generate a plot. Select h.
09:51 This generates the plot of h with respect to time -with h on y-axis and time on the x-axis
10:01 By default, the simulation is run from 0 to 1 unit of time.
10:07 The unit of time depends on the system of units used for other variables.
10:13 Let me de-select h.
10:17 It is always a good practice to delete the results, once the necessary plots have been generated.
10:25 To delete this result, right-click on freeFall and select Delete result.
10:33 The result has now been deleted.
10:36 Let me go back to Modeling perspective.
10:39 Click on Modeling button at bottom-right.
10:43 class is used synonymously with model, in Modelica.
10:48 One may use model instead of class here, to produce the same effect.
10:54 Now, let me show you how to change the time interval for simulation.
11:01 Click on Simulation Setup button present in the toolbar.
11:06 Under General tab, locate Stop time field. Change it to 5 units.
11:14 Click on Simulate. Close the pop-up window which appears.
11:21 Let me select h once again, in the Variables browser.
11:26 This generates h v/s time plot.
11:29 Notice that the time interval has increased to 5 units.
11:33 But, the value of h has gone below zero which is unacceptable.
11:40 We will learn how to rectify this issue in the later tutorials.
11:45 Let me delete this result by right-clicking on freeFall and selecting Delete result.
11:53 Go back to Modeling perspective by clicking on Modeling perspective at bottom-right.
11:59 It is necessary to ensure that the number of equations is equal to the number of variables.
12:07 This class has two variables and two equations.
12:11 Now, let me delete the first equation and simulate this class to see what happens.
12:18 I have deleted the first equation.
12:21 Notice that a star appears beside the name of the class, in freeFall tab.
12:28 This indicates unsaved changes in the class.
12:31 Hence it is a good practice to save a class after a change has been made.
12:38 To save this class, go to the File menu and click on Save.
12:44 You may also use the Save button in toolbar which my cursor points to, to save a file.
12:53 Now, let me simulate this class by clicking on Simulate button.
12:59 Note that an error message pops up in the Messages browser.
13:04 It says: there are too few equations and the model has 1 equation and 2 variables. Hence this cannot be simulated.
13:14 Let me insert the equation back in its place and click on Save button in the toolbar.
13:24 Click on Simulate button once again to simulate this class.
13:29 Note that the class simulates successfully, since the number of equations is equal to the number of variables.
13:37 Close the pop-up window.
13:40 Let me go back to the slides.
13:43 “der()” is Modelica function for time derivative.
13:48 There is no data flow direction for equations.
13:52 For example, der(h) = v may also be written as v = der(h).
14:00 Initial equations section is used to enter initial conditions.
14:05 We shall learn more about Initial equation later on.
14:10 As an assignment, write a model to simulate the differential equation, dx/dt = -a into x , where a = 1, x belongs to R and the value of x at time t=0 is 5.
14:28 This brings us to the end of this tutorial.
14:31 Watch the video at the following link. It summarizes the Spoken Tutorial project.
14:37 We conduct workshops using spoken tutorials; give certificates. Please contact us.
14:43 Spoken Tutorial project is funded by NMEICT, MHRD, Government of India.
14:49 We thank the development team of OpenModelica for their support.
14:53 Thank you.

Contributors and Content Editors

Jyotisolanki, PoojaMoolya, Sandhya.np14

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