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In BasicLandingStepper, instead of basing time step on acceleration (higher acceleration => shorter time step), base it on change in acceleration (ie jerk)

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This commit is contained in:
JoePfeiffer 2022-05-13 15:24:23 -06:00
parent 0910317bf6
commit f6b30df8f9
2 changed files with 26 additions and 8 deletions
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23
core/src/net/sf/openrocket/simulation/BasicLandingStepper.java
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@ -70,8 +70,14 @@ public class BasicLandingStepper extends AbstractSimulationStepper {
// Select tentative time step // Select tentative time step
double timeStep = MathUtil.min(0.5 / linearAcceleration.length(), RECOVERY_TIME_STEP); double timeStep = RECOVERY_TIME_STEP;
// adjust based on change in acceleration (ie jerk)
final double jerk = linearAcceleration.sub(status.getRocketAcceleration()).multiply(1.0/status.getPreviousTimeStep()).length();
if (jerk > MathUtil.EPSILON) {
timeStep = Math.min(timeStep, 1.0/jerk);
}
// Perform Euler integration // Perform Euler integration
Coordinate newPosition = status.getRocketPosition().add(status.getRocketVelocity().multiply(timeStep)). Coordinate newPosition = status.getRocketPosition().add(status.getRocketVelocity().multiply(timeStep)).
add(linearAcceleration.multiply(MathUtil.pow2(timeStep) / 2)); add(linearAcceleration.multiply(MathUtil.pow2(timeStep) / 2));
@ -82,7 +88,6 @@ public class BasicLandingStepper extends AbstractSimulationStepper {
final double a = linearAcceleration.z; final double a = linearAcceleration.z;
final double v = status.getRocketVelocity().z; final double v = status.getRocketVelocity().z;
final double z0 = status.getRocketPosition().z; final double z0 = status.getRocketPosition().z;
final double z = linearAcceleration.x;
// The new timestep is the solution of // The new timestep is the solution of
// 1/2 at^2 + vt + z0 = 0 // 1/2 at^2 + vt + z0 = 0
@ -95,12 +100,12 @@ public class BasicLandingStepper extends AbstractSimulationStepper {
newPosition = newPosition.setZ(0); newPosition = newPosition.setZ(0);
} }
status.setRocketPosition(newPosition);
status.setRocketVelocity(status.getRocketVelocity().add(linearAcceleration.multiply(timeStep)));
airSpeed = status.getRocketVelocity().add(windSpeed);
status.setSimulationTime(status.getSimulationTime() + timeStep); status.setSimulationTime(status.getSimulationTime() + timeStep);
status.setPreviousTimeStep(timeStep);
status.setRocketPosition(newPosition);
status.setRocketVelocity(status.getRocketVelocity().add(linearAcceleration.multiply(timeStep)));
status.setRocketAcceleration(linearAcceleration);
// Update the world coordinate // Update the world coordinate
WorldCoordinate w = status.getSimulationConditions().getLaunchSite(); WorldCoordinate w = status.getSimulationConditions().getLaunchSite();
@ -117,6 +122,8 @@ public class BasicLandingStepper extends AbstractSimulationStepper {
data.setValue(FlightDataType.TYPE_ALTITUDE, status.getRocketPosition().z); data.setValue(FlightDataType.TYPE_ALTITUDE, status.getRocketPosition().z);
data.setValue(FlightDataType.TYPE_POSITION_X, status.getRocketPosition().x); data.setValue(FlightDataType.TYPE_POSITION_X, status.getRocketPosition().x);
data.setValue(FlightDataType.TYPE_POSITION_Y, status.getRocketPosition().y); data.setValue(FlightDataType.TYPE_POSITION_Y, status.getRocketPosition().y);
airSpeed = status.getRocketVelocity().add(windSpeed);
if (extra) { if (extra) {
data.setValue(FlightDataType.TYPE_POSITION_XY, data.setValue(FlightDataType.TYPE_POSITION_XY,
MathUtil.hypot(status.getRocketPosition().x, status.getRocketPosition().y)); MathUtil.hypot(status.getRocketPosition().x, status.getRocketPosition().y));

11
core/src/net/sf/openrocket/simulation/SimulationStatus.java
View File

@ -46,6 +46,7 @@ public class SimulationStatus implements Monitorable {
private Coordinate position; private Coordinate position;
private WorldCoordinate worldPosition; private WorldCoordinate worldPosition;
private Coordinate velocity; private Coordinate velocity;
private Coordinate acceleration;
private Quaternion orientation; private Quaternion orientation;
private Coordinate rotationVelocity; private Coordinate rotationVelocity;
@ -105,6 +106,7 @@ public class SimulationStatus implements Monitorable {
this.position = this.simulationConditions.getLaunchPosition(); this.position = this.simulationConditions.getLaunchPosition();
this.velocity = this.simulationConditions.getLaunchVelocity(); this.velocity = this.simulationConditions.getLaunchVelocity();
this.worldPosition = this.simulationConditions.getLaunchSite(); this.worldPosition = this.simulationConditions.getLaunchSite();
this.acceleration = Coordinate.ZERO;
// Initialize to roll angle with least stability w.r.t. the wind // Initialize to roll angle with least stability w.r.t. the wind
Quaternion o; Quaternion o;
@ -175,6 +177,7 @@ public class SimulationStatus implements Monitorable {
this.time = orig.time; this.time = orig.time;
this.previousTimeStep = orig.previousTimeStep; this.previousTimeStep = orig.previousTimeStep;
this.position = orig.position; this.position = orig.position;
this.acceleration = orig.acceleration;
this.worldPosition = orig.worldPosition; this.worldPosition = orig.worldPosition;
this.velocity = orig.velocity; this.velocity = orig.velocity;
this.orientation = orig.orientation; this.orientation = orig.orientation;
@ -300,7 +303,15 @@ public class SimulationStatus implements Monitorable {
public Coordinate getRocketVelocity() { public Coordinate getRocketVelocity() {
return velocity; return velocity;
} }
public void setRocketAcceleration(Coordinate acceleration) {
this.acceleration = acceleration;
this.modID++;
}
public Coordinate getRocketAcceleration() {
return acceleration;
}
public boolean moveBurntOutMotor( final MotorConfigurationId motor) { public boolean moveBurntOutMotor( final MotorConfigurationId motor) {
// get motor from normal list // get motor from normal list