I want to model the drivingshaft of a vehicle. If I just use mathematical equations，I can get the right simulation result. however,my aim is to model a whole vehicle,so I need to add a connector (flange )to my model ,then errors come up ! my code is as follows :
model drivingshaft
  import SI = Modelica.SIunits;
  RotFlange_a  flange_a ;
  input SI.Velocity u;
  SI.AngularVelocity dew;
  parameter SI.Mass m = 1360;
  parameter SI.Area A = 2.57;
  parameter SI.CoefficientOfFriction Cd = 0.26,f = 0.014;
  parameter SI.Radius Rwh = 0.348;
  parameter SI.Acceleration g = 9.81;
  parameter Real ktrans = 4.113;
  SI.Force Fenv;
  SI.Torque tau;
  parameter SI.Inertia J = m * Rwh ^ 2;
equation
  dew = der(flange_a.phi);
  Fenv = (Cd * A * u ^ 2) / 21.15 + m * g * f + m * der(u);
  tau = Fenv * Rwh;
  dew = u / (Rwh * ktrans);
  J * der(dew) = flange_a.tau + tau;
end drivingshaft;
who can tell me the problem? Thank you!
cherry