Modeling concepts

• Three basic approaches:
  1. hybrid decomposition
     • two subsystems for phases "swinging" and "falling"
     • have different state space dimensions
     • "swinging" phase uses angle φ, ω
     • "falling" phase uses cartesian coordinates x, y, vx, vy
     • global switch activates/deactivates subsystems
  2. maximal state space
     • contains all variables φ, x, y and derivatives
     • unused variables are "frozen"
  3. high index DAE using cartesian coordinates only
     • constraint equation changes
• Equation-based solution in Modelica:
  1. seems hopeless in Modelica, since total equation count is constant
  2. implementation straightforward
  3. seems easy, but doesn't work