Sandhya.np14 at 10:33, 18 August 2018

2018-08-18T10:33:02Z

Sandhya.np14 at 10:03, 18 August 2018

2018-08-18T10:03:25Z

Sandhya.np14 at 15:29, 17 August 2018

2018-08-17T15:29:49Z

Jyotisolanki: Created page with "{| border=1 ||''' Time ''' ||'''Narration''' |- ||00:01 || Welcome to the spoken tutorial on '''Control flow and Event handling'''. |- || 00:07 || In this tutorial, we are g..."

2017-09-27T07:04:12Z

Created page with "{| border=1 ||''' Time ''' ||'''Narration''' |- ||00:01 || Welcome to the spoken tutorial on '''Control flow and Event handling'''. |- || 00:07 || In this tutorial, we are g..."

New page

{| border=1
||''' Time '''
||'''Narration'''

|-
||00:01
|| Welcome to the spoken tutorial on '''Control flow and Event handling'''.

|-
|| 00:07
|| In this tutorial, we are going to learn:How to use '''if-else''' statement , How to handle '''time''' and '''state''' events, How to use '''when''' statement.

|-
|| 00:19
|| To record this tutorial, I am using : '''OpenModelica 1.9.2''' and '''Ubuntu Operating''' system version 14.04.

|-
|| 00:30
||But, this process is identical in '''Windows, Mac OS X''' or '''FOSSEE OS''' on '''ARM'''.

|-
|| 00:38
|| To understand and practice this tutorial, you need to know the following: equation-based '''modeling''' of physical systems ,

|-
|| 00:47
||branching in any programming language , '''class''' definition in '''Modelica'''

|-
|| 00:53
||Pre-requisite tutorials are mentioned on '''Spoken Tutorial''' website. Please go through them.

|-
|| 01:00
||'''freeFall''' class was already discussed in previous tutorials.

|-
|| 01:05
||Now, let us add a '''constraint''' to it.

|-
|| 01:08
||Ball is at rest until '''t = 0.5''' seconds. Free fall under '''gravity''' starts at time '''t = 0.5''' seconds.

|-
|| 01:19
||I have created a '''model''' named '''timeEventExample''' which simulates this condition.

|-
||01:25
||'''timeEventExample''' file is available in '''Code Files''' link on '''spoken tutorial''' website.

|-
|| 01:32
||Please download and save all the files in '''Code Files''' link.

|-
|| 01:38
||For your convenience, '''freeFall class''' is also made available.

|-
|| 01:43
|| Now let me go to '''OMEdit'''.

|-
|| 01:45
||I have already launched it on my system.

|-
|| 01:49
|| To open '''OMEdit''' on '''Ubuntu Operating System''', click on '''Dash Home''' icon at the top left.

|-
|| 01:58
|| Type '''OMEdit''' in the '''Search bar''' and click on '''OMEdit''' icon. Let me go back.

|-
|| 02:06
||Note: '''Windows''' users may similarly search for '''OMEdit''' in '''Start''' menu and open it.

|-
|| 02:13
|| To open '''timeEventExample''' file, click on the tool named '''Open Model/Library File'''.

|-
|| 02:21
|| Locate '''timeEventExample''' file in your system and click on '''Open'''.

|-
|| 02:28
||You may alternatively use the '''File''' menu to open this file.

|-
|| 02:34
||Note that '''timeEventExample''' has appeared in '''Libraries browser'''.

|-
||02:39
||Right-click on this icon and select '''View class'''.

|-
|| 02:44
||The model has now opened in '''Diagram view'''.

|-
||02:47
||Click on third button which is the '''Text View'''.

|-
|| 02:51
||We have already discussed that '''model''' and '''class''' are used synonymously in '''Modelica'''.

|-
|| 02:58
|| The name of this '''model''' is '''timeEventExample'''.

|-
|| 03:02
|| '''Comments''' such as this, may be written on the first line of a '''model''' or '''class'''.

|-
|| 03:08
|| '''h, v''' and '''g''' represent the same quantities as in '''freeFall class'''.

|-
|| 03:16
|| '''initial equation''' section contains initial conditions.

|-
|| 03:21
|| Value of '''h''' at time '''t = 0''' is '''30m'''.

|-
|| 03:26
|| Value of '''v''' at time '''t = 0''' is '''0'''.

|-
|| 03:31
|| '''Equation''' signifies the beginning of equation section of this '''model'''.

|-
|| 03:36
|| Now, let us see how to insert the '''constraint''' explained in slides.

|-
|| 03:43
|| Note that there is an '''if-else block''' in '''equation''' section as shown.

|-
|| 03:48
||Let us try to understand each statement of this '''if-else block'''.

|-
|| 03:53
|| '''if statement''' places a '''constraint''' on '''time''' variable.

|-
|| 03:58
||'''time''' is a built-in variable in '''Modelica'''.

|-
|| 04:01
||It need not be explicitly declared in a '''class''' or '''model'''.

|-
|| 04:06
|| The ball experiences free fall after time '''0.5''' seconds.

|-
|| 04:12
||Hence, these two equations represent the same equations as those in '''freeFall class'''.

|-
|| 04:19
|| '''else branch''' contains '''equations''' which are executed when time is less than '''0.5''' seconds.

|-
|| 04:27
|| The ball is at rest when time is less than '''0.5''' seconds.

|-
|| 04:32
||Hence, these two '''equations''' hold good in that case.

|-
|| 04:36
|| '''end if''' signifies the end of '''if-else block'''.

|-
|| 04:41
|| The '''model''' is now complete.

|-
|| 04:44
||Let us simulate it by clicking on '''Simulate''' button.

|-
||04:48
|| '''Plotting perspective''' has now opened.

|-
|| 04:51
||Select '''h''' in the '''Variables browser'''.

|-
|| 04:55
|| This generates '''h''' versus '''time''' plot.

|-
|| 04:58
||Since the ball is at rest until time '''t=0.5''' seconds, height remains the same.

|-
|| 05:06
||To delete the result, right click on '''timeEventExample''' in Variables browser and select '''Delete Result'''.

|-
|| 05:15
|| To go back to '''Modeling perspective''', click on '''Modeling''' button at bottom right.

|-
|| 05:21
|| Now, let me delete the second '''equation''' in '''else branch'''.

|-
|| 05:26
||Click on '''Save''' button in the toolbar, to save this '''model'''.

|-
|| 05:31
|| Click on '''Simulate'''.

|-
|| 05:34
|| The simulation has failed.

|-
||05:37
||Go to the '''Messages browser''' and scroll up to see the error message.

|-
|| 05:42
||The error message says that the number of '''equations''' in each '''branch''' should be the same.

|-
|| 05:49
||Therefore, the number of '''equations''' in '''if''' and '''else branches''' should each be equal to the number of variables.

|-
|| 05:58
||Let me insert the '''equation''' back in its place and click on '''Save''' button.

|-
|| 06:05
|| Note that '''der(h) = v''' is an '''equation''' which is common to both '''if''' and '''else branches'''.

|-
|| 06:14
||Hence, the '''if-else block''' can be replaced by two '''statements'''.

|-
||06:20
|| Let me show you how it is done.

|-
|| 06:23
||Delete the '''if-else block''' first.

|-
||06:26
||The equations to be typed here have been provided in a file named '''if else-statement.txt'''.

|-
|| 06:34
|| These file is also available in '''Code Files''' link.

|-
|| 06:39
|| Since it is a text file, I have used '''gedit''' to open it.

|-
|| 06:45
|| Let me go to '''gedit'''.

|-
|| 06:47
||'''Windows''' users may open this file using '''Notepad''' or any other text editor.

|-
|| 06:54
|| Copy the two equations.

|-
|| 06:57
|| Go back to '''OMEdit'''.

|-
|| 07:00
||Do a right-click and select '''Paste'''

|-
|| 07:04
|| Click on '''Save''' button in the toolbar once again.

|-
||07:08
|| Click on '''Simulate'''.

|-
|| 07:11
||Close the pop up window.

|-
||07:14
||Select '''h''' in the '''Variables browser''' once again.

|-
|| 07:18
||Note that the '''h''' versus '''time''' plot is the same as in previous case which indicates that both models are the same.

|-
||07:27
||To delete the result, right-click on '''timeEventExample''' and select '''Delete Result'''.

|-
|| 07:34
|| Click on '''Modeling''' button at bottom right.

|-
|| 07:38
|| This is an '''if-else statement''' which indicates that if '''time >= 0.5''' '''dv/dt = g''' otherwise '''dv/dt = 0'''.

|-
||07:52
|| Now let me go back to the slides.

|-
||07:55
||Please note that the number of '''equations''' in '''if branch''' should be equal to the number of equations in '''else branch'''.

|-
|| 08:03
||And both of them should be equal to the number of variables in the '''class''' or '''model'''.

|-
||08:10
|| '''Event''' is an abrupt change in behavior of a system.

|-
|| 08:15
||'''Events''' may be categorized into time events and state events.

|-
|| 08:20
||In a '''time event''', the time at which event occurs is precisely known.

|-
|| 08:25
||'''timeEventExample''' handles a time event at '''t = 0.5''' seconds

|-
|| 08:32
||'''state event''' occurs when a system variable cross a certain value.

|-
||08:38
||Let us try to understand state events using an example.

|-
|| 08:43
||A ball under free fall, faces a '''state event''' on touching the ground.

|-
|| 08:48
||The following behavior is observed when it hits the ground.

|-
|| 08:52
||Velocity of ball reverts in direction.

|-
|| 08:55
||Magnitude of velocity changes if the collision is inelastic.

|-
||09:00
||I have created a '''model''' named '''bouncingBall''' to simulate this behavior.

|-
|| 09:06
||This file is available on '''Spoken Tutorial''' Website.

|-
|| 09:10
|| To view this '''model''' and simulate it, let me go back to '''OMEdit'''.

|-
|| 09:15
|| Click on '''OpenModel/LIbrary File''' tool.

|-
|| 09:19
||Locate '''bouncingBall''' file in your system and click on '''Open'''.

|-
|| 09:25
|| Right-click on '''bouncingBall''' icon in '''Libraries browser''' and select '''View Class'''.

|-
|| 09:33
||If the '''model''' does not open in '''Text View,''' go to the top of '''modeling area''' and click on '''Text View''' button.

|-
|| 09:41
|| '''e''' is coefficient of restitution for inelastic collision of ball with Earth.

|-
|| 09:48
||It is a parameter and its value remains constant at 0.8 throughout the simulation run.

|-
|| 09:56
|| '''radius''' represents the radius of ball in '''m'''.

|-
||10:00
|| '''h, v''' and '''g''' represent the same quantities as in '''timeEventExample'''.

|-
|| 10:07
|| These two equations of motions have already been discussed in '''freeFall class'''.

|-
|| 10:13
|| '''when statement''' is used to signal an event.

|-
|| 10:17
||It is used to specify the action to be taken when an event occurs.

|-
|| 10:22
||'''h <= radius''' holds '''true''' when the ball is in contact with ground.

|-
|| 10:29
||This '''statement''' is executed whenever the event occurs.

|-
|| 10:34
|| '''reinit()''' function is used to re-initialize a variable.

|-
|| 10:39
|| Here, it re-initializes velocity of ball with the negative product of '''e''' and velocity of ball before touching the ground.

|-
|| 10:49
|| To simulate this model Click on '''Simulation Setup''' button in the toolbar.

|-
|| 10:55
||Under '''General''' tab, change '''Stop Time''' field to 30 units and Click on '''Simulate'''.

|-
|| 11:04
||Close the pop-up window.

|-
|| 11:06
|| Select '''h''' in '''Variables browser'''.

|-
|| 11:10
||Note that '''h''' drops below zero, which is unacceptable.

|-
|| 11:16
||We have seen similar behavior while simulating '''freeFall class'''.

|-
|| 11:21
|| This faulty behavior is due to numerical errors.

|-
|| 11:25
||A discussion of numerical errors is beyond the scope of this tutorial.

|-
|| 11:30
||Please refer to '''Zeno''' behavior of bouncing ball for a better understanding.

|-
||11:36
||Let me de-select '''h'''.

|-
|| 11:39
|| Let us go back to the slides.

|-
|| 11:42
|| '''when statement''' is used to signal an event.

|-
|| 11:45
||'''reinit(a,b)''' assigns value of '''b''' to variable '''a''' and resumes simulation.

|-
|| 11:54
||'''pre(a)''' returns the value of variable '''a''' before event.

|-
|| 11:59
||For example, '''reinit(a, 10)''' assigns a value of '''10''' to '''a''' when event occurs.

|-
|| 12:08
||The faulty behavior of '''bouncingBall''' model is corrected in '''bouncingBallWithHysteresis'''.

|-
||12:15
||'''bouncingBallWithHysteresis''' model is available on '''spoken tutorial''' website.

|-
|| 12:21
||Simulate '''bouncingBallWithHysteresis''' and generate '''h''' versus '''time''' plot.

|-
|| 12:27
||Notice the difference between '''bouncingBall''' and '''bouncingBallWithHysteresis'''

|-
|| 12:33
|| This brings us to the end of this tutorial.

|-
|| 12:36
|| Watch the video available at following link.'''http://spoken-tutorial.org/ http://spoken-tutorial.org] /What\_is\_a\_Spoken\_Tutorial'''

|-
|| 12:40
||It summarises the '''Spoken Tutorial''' project

|-
|| 12:42
|| We conduct workshops using spoken tutorials Give certificates Please contact us.

|-
|| 12:48
|| If you have any questions related to this spoken tutorial, please visit the following website.

|-
|| 12:55
|| Under '''Textbook Companion Project''' we coordinate coding of solved examples of popular books.

|-
|| 13:03
||We give honorarium and certificates to those who do this. For more details please visit the following website.

|-
|| 13:10
|| Under '''Lab Migration Project''' we help migrate commercial simulator labs to OpenModelica.

|-
|| 13:17
||For more information please visit the website.

|-
|| 13:21
|| '''Spoken Tutorial Project''' is supported by '''NMEICT, MHRD''', Government of India.

|-
|| 13:28
|| We thank the development team of '''OpenModelica''' for their support.

|-
|| 13:33
|| Thank you for joining me in this tutorial. Goodbye.
|-
|}

@@ Line 541: / Line 541: @@
 || 12:36
 || Watch the video available at following link.
-'''http://spoken-tutorial.org /What_is_a_Spoken_Tutorial'''
+'''http://spoken-tutorial.org/What_is_a_Spoken_Tutorial'''
 |-

@@ Line 5: / Line 5: @@
 |-
 ||00:01
-|| Welcome to the spoken tutorial on '''Control flow and Event handling'''.
+|| Welcome to the '''spoken tutorial''' on '''Control flow and Event handling'''.
 |-
 || 00:07
-|| In this tutorial, we are going to learn:How to use '''if-else''' statement , How to handle '''time''' and '''state''' events,  How to use '''when''' statement.
+|| In this tutorial, we are going to learn:
 |-
 || 00:19
-|| To record this tutorial, I am using : '''OpenModelica 1.9.2''' and '''Ubuntu Operating''' system version 14.04.
+|| To record this tutorial, I am using : '''OpenModelica 1.9.2''' and '''Ubuntu Operating system''' version '''14.04'''.
 |-
@@ Line 25: / Line 28: @@
 |-
 || 00:47
-||branching in any programming language , '''class''' definition in '''Modelica'''
+||branching in any programming language , '''class''' definition in '''Modelica'''.
 |-
@@ Line 37: / Line 40: @@
 |-
 || 01:05
-||Now, let us add a '''constraint''' to it.
+||Now, let us add a constraint to it.
 |-
 || 01:08
-||Ball is at rest until '''t = 0.5''' seconds.  Free fall under '''gravity''' starts at time '''t = 0.5''' seconds.
+||Ball is at rest until '''t = 0.5''' seconds.  Free fall under gravity starts at time '''t = 0.5''' seconds.
 |-
@@ Line 53: / Line 56: @@
 |-
 || 01:32
-||Please download and save all the files in '''Code Files''' link.
+||Please download and '''save''' all the files in '''Code Files''' link.
 |-
@@ Line 73: / Line 76: @@
 |-
 || 01:58
-|| Type '''OMEdit''' in the '''Search bar''' and click on '''OMEdit''' icon. Let me go back.
+|| Type: '''OMEdit''' in the '''Search bar''' and click on '''OMEdit''' icon. Let me go back.
 |-
@@ Line 117: / Line 120: @@
 |-
 || 03:02
-|| '''Comments''' such as this, may be written on the first line of a '''model''' or '''class'''.
+|| '''Comments''' such as this may be written on the first line of a '''model''' or '''class'''.
 |-

OpenModelica/C2/Control-flow-and-Event-handling/English-timed - Revision history

Sandhya.np14 at 10:33, 18 August 2018

Sandhya.np14 at 10:03, 18 August 2018

Sandhya.np14 at 15:29, 17 August 2018

Jyotisolanki: Created page with "{| border=1 ||''' Time ''' ||'''Narration''' |- ||00:01 || Welcome to the spoken tutorial on '''Control flow and Event handling'''. |- || 00:07 || In this tutorial, we are g..."