Bouncing Ball Simulation Example

On this page…
Example Overview Building the Component Using the Component in Microsoft Visual Basic Creating the Microsoft Visual Basic Form

Example Overview

This example is adapted from the ballode demo provided with the MATLAB product. It demonstrates repeated event location, where the conditions are changed after each terminal event.

This demo computes 10 bounces with calls to ode23, which is a MATLAB function. A user-specified damping factor after each bounce attenuates the speed of the ball. The trajectory is plotted using the output function odeplot. In addition to the damping factor, the user can also provide the initial velocity, the maximum number of bounce to track, and the maximum time until demo is completed.

This example shows you how to create the COM component using the MATLAB Builder NE product and how to use this COM component in a Visual Basic application independent of MATLAB.

Note   This example assumes that you have downloaded the MATLAB code to the matlabroot folder.

Back to Top

Building the Component

1. At the MATLAB command prompt, change folders to matlabroot/BallODE.

2. Enter the command deploytool to open the Deployment Tool window.

3. Use the Deployment Tool to create a project with the following settings:

   Setting	Value
   Project name	bouncingBall
   Class name	bouncingBallclass
   Project folder	The name of your work folder followed by the component name
   Generate Verbose Output	Selected

4. Locate your work folder, navigate to matlabroot/BallODE, and add ballode.m to the project.

5. Build the component by clicking the button in the Deployment Tool toolbar.

   The build process begins, and a log of the build appears in the Output pane of the Deployment Tool window. The files that are needed for the component are copied to two newly created folders, src and distrib, in the bouncingBall folder. A copy of the build log is placed in the src folder.

Back to Top

Using the Component in Microsoft Visual Basic

You can call the component from any application that supports COM.

To create a Microsoft Visual Basic project and add references to the necessary libraries:

1. Start Visual Basic.

2. Create a new Standard EXE project.

3. Select Project > References.

4. Select the following libraries:

   • bouncingBall 1.0 Type Library

     (If you named your class something other than bouncingBall or gave a different version number, click and use the appropriate component and corresponding type library.)

   • MWComUtil 7.5 Type Library

     Note   If you do not see these libraries, you may not have registered the libraries using mwregsvr. Refer to Component Registration for information on this.

Back to Top

Creating the Microsoft Visual Basic Form

The next task is to create a front end or a Microsoft Visual Basic form for the application. End users enter data with this form.

To create a new user form and populate it with the necessary controls:

1. Select Projects > Component. Alternatively, press Ctrl+T.

2. Check that Microsoft Windows Common Controls 6.0 is selected. You will use the ListView control from this component library.

3. Add a series of controls to the blank form to create an interface with the properties listed in the following table.

   Control Type	Control Name	Properties	Purpose
   Form	frmBallOde	Caption = Bouncing Ball ODE	Container for all components.
   Frame	frmInput	Name = frmInput* Caption = Input Data Points	Groups all input controls.
   Frame	frmOutput	Name = frmOutput* Caption = Output Coefficients	Groups all output controls.
   Label	lblInitVal	Caption = Initial Velocity	Labels the text box txtInitVal.
   TextBox	txtInitVal	Text =	Holds initial velocity by which ball is thrown into the air.
   Label	lblDamp	Caption = Damping Factor	Labels the text box txtDamp.
   TextBox	txtDamp	Text =	Holds damping factor for the bounce, that is, the factor by which the speed of the ball is reduced after it bounces.
   Label	lblIter	Caption = Number of Bounces	Labels the text box txtIter.
   TextBox	txtIter	Text =	Holds number of iterations or bounces to track.
   Label	lblFinalTime	Caption = Maximum Time	Labels the text box txtFinalTime.
   TextBox	txtFinalTime	Text =	Stores time until demo is completed.
   ListView	lstBounce	Name = lstBounce GridLines = True LabelEdit = lvwManual View = lvwReport	Displays the time stamp when ball bounces off the ground.
   CommandButton	cmdEvaluate	Caption = Evaluate Default = True	Executes the function.
   CommandButton	cmdCancel	Caption = Cancel Cancel = True	Closes the dialog box without executing the function.

4. When the design is complete, save the project by selecting File > Save. When prompted for the project name, type BallOde.vbp, and for the form, type frmBallOde.frm.

5. In the Project dialog box, right-click frmBallOde and select View Code.

   The following code listing shows the code to implement. Note that this code references the control and variable names listed above. If you have given a different name to any of the controls or any global variable, change this code to reflect the differences.

   Private theBall As Variant ' Variable to hold the COM object.
   
   Private Sub cmdCancel_Click()
       ' If the user presses the Cancel button, unload the form.
       Unload Me
   End Sub
   
   Private Sub Form_Initialize()
       Dim Len1 As Long ' Used to set length of columns for list box.
       Dim Len2 As Long ' Used to set length of columns for list box.
       On Error GoTo Handle_Error
       ' Set length of the each column based on length of the listbox
       ' such that the two columns span the maximum area without 
       ' creating a horizontal scroll bar.
       Len2 = lstBounce.Width / 2
       Len1 = (lstBounce.Width - Len2) - 300
       
       ' Add column headers to each column in the list box.
       Call lstBounce.ColumnHeaders.Add(, , "Bounce", Len1)
       Call lstBounce.ColumnHeaders.Add(, , "Time", Len2)
       
       ' Set tab indices for each component.
       txtInitVel.TabIndex = 1
       txtDamp.TabIndex = 2
       txtIter.TabIndex = 3
       txtFinalTime.TabIndex = 4
       cmdEvaluate.TabIndex = 5
       cmdCancel.TabIndex = 6
       lstBounce.TabStop = False
       
       ' Create the COM object
       ' If there is an error, handle it accordingly.
       Set theBall = CreateObject("bouncingBall.bouncingBall.1_0")
       Exit Sub
   Handle_Error:
       ' Error handling code
       MsgBox ("Error " & Err.Description)
   End Sub
   Private Sub cmdEvaluate_Click()
       ' Dim R As Range
       Dim zeroTime As Variant ' Result variable object.
       Dim loopCount As Integer
       Dim item As ListItem
       
       ' Check if the object was created properly.
       ' If not, go to the error handling routine.
       If theBall Is Nothing Then GoTo Exit_Form
       
       ' If there is an error, continue with the code.
       On Error Resume Next
       
       ' Process inputs
       ' If the user does not provide the values for input parameters,
       ' use the default values.
       If txtDamp.Text = Empty Then
           txtDamp.Text = 0.9
       End If
       If txtInitVel.Text = Empty Then
           txtInitVel.Text = 20
       End If
       If txtIter.Text = Empty Then
           txtIter.Text = 15
       End If
       If txtFinalTime.Text = Empty Then
           txtFinalTime.Text = 20
       End If
           
       'Compute Bouncing ball data
       Call theBall.ballode(1, zeroTime, CDbl(txtIter.Text),_ 
       CDbl(txtDamp.Text), CDbl(txtFinalTime.Text),_ 
       CDbl(txtInitVel.Text))
       
       ' Display the output values (time stamp when ball bounces on 
       ' the ground).
       Call lstBounce.ListItems.Clear
       For loopCount = LBound(zeroTime, 1) To UBound(zeroTime, 1)
           Set item = lstBounce.ListItems.Add(, , Format(loopCount))
           Call item.ListSubItems.Add(, , Format(zeroTime(loopCount,_ 
           1), "##.###"))
       Next
       Call lstBounce.Refresh
       
       GoTo Exit_Form
   Handle_Error:
       ' Error handling routine
       MsgBox (Err.Description)
   Exit_Form:
   End Sub
   

Back to Top

Curve Fitting Example

How the MATLAB Builder NE Product Creates COM Components

© 1984-2012- The MathWorks, Inc.    -   Site Help   -   Patents   -   Trademarks   -   Privacy Policy   -   Preventing Piracy   -   RSS