Terminate

The most common usage of terminate is to give a more appropriate stopping criteria for terminating a simulation than a fixed point in time. The terminate function takes a single argument of type String, which is used to indicate the reason for a successful termination. This is exemplified in the terminate statement within the when-statement in MoonLanding.

1 Celestial Body

class CelestialBody constant Real g = 6.672e-11; parameter Real radius; parameter String name; Real mass; end CelestialBody;

2 Rocket

class Rocket parameter String name; Real mass(start = 1038.358,fixed=true); Real altitude(start = 59404,fixed=true); Real velocity(start = -2003,fixed=true); Real acceleration; Real thrust; // Thrust force on the rocket Real gravity; // Gravity forcefield parameter Real massLossRate = 0.000277; equation (thrust - mass*gravity)/mass = acceleration; der(mass) = -massLossRate * abs(thrust); der(altitude) = velocity; der(velocity) = acceleration; end Rocket;

3 MoonLanding

When using this terminate condition the simulation stops when the moon lander touches the ground on the moon.

class MoonLanding parameter Real force1 = 36350; parameter Real force2 = 1308; protected parameter Real thrustEndTime = 210; parameter Real thrustDecreaseTime = 43.2; public Rocket apollo(name = "Apollo13"); CelestialBody moon(name = "moon", mass = 7.382e22, radius = 1.738e6); equation apollo.thrust = if (time < thrustDecreaseTime) then force1 else if (time < thrustEndTime) then force2 else 0; apollo.gravity = moon.g*moon.mass/(apollo.altitude + moon.radius) ^2; algorithm when apollo.altitude < 0 then // Termination condition terminate("The moon lander touches the ground of the moon"); end when; end MoonLanding;

4 MoonLanding Simulation

When we simulate the MoonLanding class from 0 to 230 we get a message that the simulation ended before reaching 230. In the dslog.txt file we see that the simulation is terminated at T = 218.

simulate( MoonLanding, stopTime=230 )
plot( { apollo.velocity, apollo.altitude } ) //??xrange xrange={0,208} is removed

Vertical velocity relative to the lunar surface and Altitude of the Apollo rocket over the lunar surface.