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Merge pull request #1035 from rsammelson/fix-cg-positioning

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Use correct zero point for center of gravity calculation
This commit is contained in:
Neil Weinstock 2021-11-04 15:57:30 -04:00 committed by GitHub
commit 83908a9f20
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GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 7 additions and 4 deletions
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7
core/src/net/sf/openrocket/masscalc/MassCalculation.java
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@ -343,6 +343,10 @@ public class MassCalculation {
// mass data for *this component only* in the rocket-frame // mass data for *this component only* in the rocket-frame
compCM = parentTransform.transform( compCM.add(component.getPosition()) ); compCM = parentTransform.transform( compCM.add(component.getPosition()) );
// setting zero as the CG position means the top of the component, which is component.getPosition()
final Coordinate compZero = parentTransform.transform( component.getPosition() );
if (component.getOverrideSubcomponents()) { if (component.getOverrideSubcomponents()) {
if( component.isMassive() ){ if( component.isMassive() ){
// if this component mass, merge it in before overriding: // if this component mass, merge it in before overriding:
@ -352,14 +356,13 @@ public class MassCalculation {
this.setCM( this.getCM().setWeight(component.getOverrideMass()) ); this.setCM( this.getCM().setWeight(component.getOverrideMass()) );
} }
if (component.isCGOverridden()) { if (component.isCGOverridden()) {
this.setCM( this.getCM().setX( compCM.x + component.getOverrideCGX())); this.setCM( this.getCM().setX( compZero.x + component.getOverrideCGX()));
} }
}else { }else {
if (component.isMassOverridden()) { if (component.isMassOverridden()) {
compCM = compCM.setWeight( component.getOverrideMass() ); compCM = compCM.setWeight( component.getOverrideMass() );
} }
if (component.isCGOverridden()) { if (component.isCGOverridden()) {
final Coordinate compZero = parentTransform.transform( Coordinate.ZERO );
compCM = compCM.setX( compZero.x + component.getOverrideCGX() ); compCM = compCM.setX( compZero.x + component.getOverrideCGX() );
} }
this.addMass( compCM ); this.addMass( compCM );

4
core/test/net/sf/openrocket/masscalc/MassCalculatorTest.java
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@ -1064,7 +1064,7 @@ public class MassCalculatorTest extends BaseTestCase {
double calcTotalMass = structure.getMass(); double calcTotalMass = structure.getMass();
assertEquals(" Booster Launch Mass is incorrect: ", expMass, calcTotalMass, EPSILON); assertEquals(" Booster Launch Mass is incorrect: ", expMass, calcTotalMass, EPSILON);
final double expCMx = 1.0446069131149498; final double expCMx = 1.1191303646438673;
Coordinate expCM = new Coordinate(expCMx, 0, 0, expMass); Coordinate expCM = new Coordinate(expCMx, 0, 0, expMass);
assertEquals(" Booster Launch CM.x is incorrect: ", expCM.x, structure.getCM().x, EPSILON); assertEquals(" Booster Launch CM.x is incorrect: ", expCM.x, structure.getCM().x, EPSILON);
assertEquals(" Booster Launch CM.y is incorrect: ", expCM.y, structure.getCM().y, EPSILON); assertEquals(" Booster Launch CM.y is incorrect: ", expCM.y, structure.getCM().y, EPSILON);
@ -1076,7 +1076,7 @@ public class MassCalculatorTest extends BaseTestCase {
double boosterMOI_xx = structure.getRotationalInertia(); double boosterMOI_xx = structure.getRotationalInertia();
assertEquals(" Booster x-axis MOI is incorrect: ", expMOI_axial, boosterMOI_xx, EPSILON); assertEquals(" Booster x-axis MOI is incorrect: ", expMOI_axial, boosterMOI_xx, EPSILON);
final double expMOI_tr = 0.036243133045; final double expMOI_tr = 0.040989095911;
double boosterMOI_tr = structure.getLongitudinalInertia(); double boosterMOI_tr = structure.getLongitudinalInertia();
assertEquals(" Booster transverse MOI is incorrect: ", expMOI_tr, boosterMOI_tr, EPSILON); assertEquals(" Booster transverse MOI is incorrect: ", expMOI_tr, boosterMOI_tr, EPSILON);
} }