VERSION 5.00
Begin VB.Form Form1 
   BackColor       =   &H00C0FFFF&
   Caption         =   "Form1"
   ClientHeight    =   7845
   ClientLeft      =   60
   ClientTop       =   390
   ClientWidth     =   11025
   LinkTopic       =   "Form1"
   ScaleHeight     =   7845
   ScaleWidth      =   11025
   StartUpPosition =   3  'Windows Default
End
Attribute VB_Name = "Form1"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = True
Attribute VB_Exposed = False
Public inkey$
Private Sub Form_KeyPress(KeyAscii As Integer)
inkey$ = Chr$(KeyAscii)
End Sub

Private Sub Form_Load()
Show
ZOrder (0)
Scale (3, -2.5)-(-3, 2.5)
SetFocus

Print "Simulation of closed-loop system with `live input'"
Print "ERROR Phase-plane is shown - velocity against position ERROR"
Print "Press number keys, q to quit"
Print
'INPUT "Feedback, damping (suggest 8,2 to start) "; f, d
f = 8
d = 2

'VIEW (2, 20)-(638, 328), 8, 4
Line (-2.5, 0)-(2.5, 0), vbBlue
Line (0, -2.5)-(0, 2.5), vbBlue


Print "Press number keys 0 to 9 to change the target, q to quit"
Print "Velocity versus position ERROR";
Print "  Scale -2.5 to 2.5 in position and velocity";
'
   dt = 0.001           'Make dt larger to speed up running
   x = 1               'Initial values
   v = 0
   t = 0
   Target = 0           'until a key is pressed
   PSet (x - Target, v)      'move to the first point
   Do
      a$ = inkey$
      inkey$ = ""
      If a$ <> "" Then
         Target = 0.5 * (Val(a$) - 5)
         PSet (x - Target, v)
      End If

      u = f * (Target - x) - d * v          'u is determined by feedback

      x = x + v * dt                        'This is the simulation
      v = v + u * dt                        '
      t = t + dt
     
      Line -(x - Target, v)                        'This displays the result
      DoEvents
   Loop Until a$ = "q"
'

End
End Sub