# spring_mass_damper.mbd

#-----------------------------------------------------------------------------
# [Data Block]

begin: data;
   problem: initial value;
end: data;

#-----------------------------------------------------------------------------
# [<Problem> Block]

begin: initial value;
   initial time:   0.;
   final time:     5.;
   time step:      1.e-3;
   max iterations: 10;
   tolerance:      1.e-6;
end: initial value;

#-----------------------------------------------------------------------------
# [Control Data Block]

begin: control data;
   output frequency: 10;
   structural nodes: 2;
   rigid bodies:     1;
   joints:           3;
   forces:           1;
   gravity;
end: control data;

#-----------------------------------------------------------------------------
# Design Variables
set: real M = 1.;  #[kg] Mass
set: real L = 1.;  #[m] Spring Natural Length
set: real K = 20.; #[N/m] Spring Stiffness Coefficient
set: real C = 1;   #[Ns/m] Damper Damping Coefficient

#-----------------------------------------------------------------------------
# Node Labels
set: integer Node_Ground = 1;
set: integer Node_Mass   = 2;

# Body Labels
set: integer Body_Mass = 1;

# Joint Labels
set: integer JoClamp_Ground      = 1;
set: integer JoInLin_Ground_Mass = 2;
set: integer JoPrism_Ground_Mass = 3;

# Force Labels
set: integer Force_SpringDamper = 1;

#-----------------------------------------------------------------------------
# [Nodes Block]

begin: nodes;

   #-----------------------------------------------------------------------------
   # Nodes
   structural: Node_Ground, static,
      null, # absolute position
      eye,  # absolute orientation
      null, # absolute velocity
      null; # absolute angular velocity
      
   structural: Node_Mass, dynamic,
      0., 0., -L, # absolute position
      eye,        # absolute orientation
      null,       # absolute velocity
      null;       # absolute angular velocity
      
end: nodes;

#-----------------------------------------------------------------------------
# Plugin Variables
set: [node, DZ, Node_Mass, structural, string="X[3]"];
set: [node, VZ, Node_Mass, structural, string="XP[3]"];

#-----------------------------------------------------------------------------
# [Elements Block]

begin: elements;

   #-----------------------------------------------------------------------------
   # Bodies
   body: Body_Mass, Node_Mass,
      M,    # mass
      null, # relative center of mass
      eye;  # inertia matrix

   #-----------------------------------------------------------------------------
   # Joints
   joint: JoClamp_Ground,
      clamp,
         Node_Ground,
            null, # absolute position
            eye;  # absolute orientation
      
   joint: JoInLin_Ground_Mass, 
      in line,
         Node_Ground,
            null, # relative line position
            eye,  # relative line orientation
         Node_Mass;
      
   joint: JoPrism_Ground_Mass,
      prismatic,
         Node_Ground,
         Node_Mass;
    
   #-----------------------------------------------------------------------------
   # Forces  
   force: Force_SpringDamper,
      follower internal,
         Node_Mass,
            position, null,                               # relative arm
         Node_Ground,
            position, null,                               # relative arm
         single, 0., 0., 1., string, "-K*(DZ-(-L))-C*VZ"; # force value
   
   #-----------------------------------------------------------------------------
   # Gravity          
   gravity: 0., 0., -1., const, 9.81;
   
end: elements;