APMonitor

! Truck suspension 
! 
! D. Matko, R. Karba and B. Zupancic, Simulation and Modeling of Continuous
!   Systems.  Prentice Hall, 1992. 
!
! APMonitor Modeling Language
! https://www.apmonitor.com
Model suspension
  Parameters
    m[1] = 500  ! kg
    m[2] = 50   ! kg
    k[1] = 7500 ! spring constant
    k[2] = 150000 ! spring constant
    f = 2250    ! N
    z = 0       ! vertical displacement
  End Parameters

  Variables
    y[1] = -0.05 ! position
    y[2] = 0
    z[1] = 0     ! velocity
    z[2] = 0
  End Variables

  Equations
    $y[1] = z[1]
    $y[2] = z[2]
    m[1] * $z[1] = -f * (z[1]-z[2]) - k[1] * (y[1]-y[2])
    m[2] * $z[2] = -f * (z[2]-z[1]) - k[1] * (y[2]-y[1]) - k[2] * (y[2]-z)
  End Equations
End Model