Train Models in Modelica Sample Clauses

Train Models in Modelica. Kinematics and speed control of both trains is encoded by the equations in Fig. 4. The first equation block captures motion: acceleration is the deriva- tive (operator der(_)) of the train’s velocity, given by the current speed variable, and velocity the derivative of its relative position on the track, given by the position on track variable. While an accurate physics model of the train would be expressed in terms of traction and braking forces, the assumption of constant train mass and Xxxxxx’x law entitles us to consider acceleration alone. The second equation block realises a control algorithm: acceleration is set to either zero, normal_acceleration or normal_deceleration, depending on whether the current speed is equal, below or above the set-point speed Figure 4: Train control equations in Modelica. of the train, set by the driver. The latter two are suitable constants of the model. A special case is added by the when clause that simultaneously sets the train speed to the set-point speed and acceleration to zero if we are close to the set-point speed. This is to avoid chattering during simulation and can also be thought of as ‘engaging the brakes’ when the train approaches zero speed while decelerating towards a halt. The behaviour of the train driver is captured by the following equation: