Merge pull request #1355 from JoePfeiffer/use-jerk

Use jerk to adjust simulation timestep while landing

core/src/net/sf/openrocket/simulation/BasicLandingStepper.java

@@ -70,8 +70,14 @@ public class BasicLandingStepper extends AbstractSimulationStepper {
 
 
 		// 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
 		Coordinate newPosition = status.getRocketPosition().add(status.getRocketVelocity().multiply(timeStep)).
 			add(linearAcceleration.multiply(MathUtil.pow2(timeStep) / 2));
@@ -94,12 +100,12 @@ public class BasicLandingStepper extends AbstractSimulationStepper {
 			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.setPreviousTimeStep(timeStep);
+
+		status.setRocketPosition(newPosition);
+		status.setRocketVelocity(status.getRocketVelocity().add(linearAcceleration.multiply(timeStep)));
+		status.setRocketAcceleration(linearAcceleration);
 
 		// Update the world coordinate
 		WorldCoordinate w = status.getSimulationConditions().getLaunchSite();
@@ -116,6 +122,8 @@ public class BasicLandingStepper extends AbstractSimulationStepper {
 		data.setValue(FlightDataType.TYPE_ALTITUDE, status.getRocketPosition().z);
 		data.setValue(FlightDataType.TYPE_POSITION_X, status.getRocketPosition().x);
 		data.setValue(FlightDataType.TYPE_POSITION_Y, status.getRocketPosition().y);
+
+		airSpeed = status.getRocketVelocity().add(windSpeed);
 		if (extra) {
 			data.setValue(FlightDataType.TYPE_POSITION_XY,
 					MathUtil.hypot(status.getRocketPosition().x, status.getRocketPosition().y));

core/src/net/sf/openrocket/simulation/SimulationStatus.java

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

swing/resources-src/datafiles/components

@@ -1 +1 @@
-Subproject commit 8304c0fd3dc80d65c40af4da83268ec1b32931d6
+Subproject commit 860757167c4835a7bb960a4cbb52b06f3309791c