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Merge pull request #2368 from JoePfeiffer/fix-2278

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Don't consider shoulders in applying parallel axis theorem to longitudinal moment of inertia
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Joe Pfeiffer 2023-10-16 13:42:48 -06:00 committed by GitHub
commit 8f937daf33
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2 changed files with 22 additions and 11 deletions
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19
core/src/net/sf/openrocket/rocketcomponent/SymmetricComponent.java
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@ -281,14 +281,25 @@ public abstract class SymmetricComponent extends BodyComponent implements BoxBou
/** /**
* Calculate CG of the component by integrating over the length of the component. * Return the CG and mass of the component. Subclasses may
* The method caches the result, so subsequent calls are instant. Subclasses may
* override this method for simple shapes and use this method as necessary. * override this method for simple shapes and use this method as necessary.
* *
* @return The CG+mass of the component. * @return The CG+mass of the component.
*/ */
@Override @Override
public Coordinate getComponentCG() { public Coordinate getComponentCG() {
return getSymmetricComponentCG();
}
/**
* Calculate CG of the symmetric component by integrating over the length of the component.
* The method caches the result, so subsequent calls are instant. We need this method because subclasses
* override getComponentCG() and include mass of shoulders
*
* @return The CG+mass of the component.
*/
private Coordinate getSymmetricComponentCG() {
if (cg == null) if (cg == null)
integrate(); integrate();
return cg; return cg;
@ -491,7 +502,7 @@ public abstract class SymmetricComponent extends BodyComponent implements BoxBou
longitudinalInertia /= vol; longitudinalInertia /= vol;
// Shift longitudinal inertia to CG // Shift longitudinal inertia to CG
longitudinalInertia = Math.max(longitudinalInertia - pow2(getComponentCG().x), 0); longitudinalInertia = longitudinalInertia - pow2(getSymmetricComponentCG().x);
} }
@ -548,7 +559,7 @@ public abstract class SymmetricComponent extends BodyComponent implements BoxBou
rotationalInertia /= surface; rotationalInertia /= surface;
// Shift longitudinal inertia to CG // Shift longitudinal inertia to CG
longitudinalInertia = Math.max(longitudinalInertia - pow2(getComponentCG().x), 0); longitudinalInertia = longitudinalInertia - pow2(getSymmetricComponentCG().x);
} }

14
core/test/net/sf/openrocket/masscalc/MassCalculatorTest.java
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@ -625,7 +625,7 @@ public class MassCalculatorTest extends BaseTestCase {
// Component: Nose Cone // Component: Nose Cone
final NoseCone payloadNose = (NoseCone) payloadStage.getChild(0); final NoseCone payloadNose = (NoseCone) payloadStage.getChild(0);
assertEquals(payloadNose.getName() + " Rotational MOI calculated incorrectly: ", 3.508155e-5, payloadNose.getRotationalInertia(), EPSILON); assertEquals(payloadNose.getName() + " Rotational MOI calculated incorrectly: ", 3.508155e-5, payloadNose.getRotationalInertia(), EPSILON);
assertEquals(payloadNose.getName() + " Longitudinal MOI calculated incorrectly: ", 2.0400578477e-6, payloadNose.getLongitudinalInertia(), EPSILON); assertEquals(payloadNose.getName() + " Longitudinal MOI calculated incorrectly: ", 3.993059978352989E-5, payloadNose.getLongitudinalInertia(), EPSILON);
// Component: Payload BodyTube // Component: Payload BodyTube
final BodyTube payloadBody = (BodyTube) payloadStage.getChild(1); final BodyTube payloadBody = (BodyTube) payloadStage.getChild(1);
@ -695,7 +695,7 @@ public class MassCalculatorTest extends BaseTestCase {
expInertia = 1.73189409900e-5; expInertia = 1.73189409900e-5;
compInertia = boosterNose.getRotationalInertia(); compInertia = boosterNose.getRotationalInertia();
assertEquals(boosterNose.getName() + " Rotational MOI calculated incorrectly: ", expInertia, compInertia, EPSILON); assertEquals(boosterNose.getName() + " Rotational MOI calculated incorrectly: ", expInertia, compInertia, EPSILON);
expInertia = 4.51796586171e-6; expInertia = 1.814234981813717E-5;
compInertia = boosterNose.getLongitudinalInertia(); compInertia = boosterNose.getLongitudinalInertia();
assertEquals(boosterNose.getName() + " Longitudinal MOI calculated incorrectly: ", expInertia, compInertia, EPSILON); assertEquals(boosterNose.getName() + " Longitudinal MOI calculated incorrectly: ", expInertia, compInertia, EPSILON);
@ -946,7 +946,7 @@ public class MassCalculatorTest extends BaseTestCase {
double boosterMOIRotational = spent.getRotationalInertia(); double boosterMOIRotational = spent.getRotationalInertia();
assertEquals(" Booster x-axis MOI is incorrect: ", expMOIRotational, boosterMOIRotational, EPSILON); assertEquals(" Booster x-axis MOI is incorrect: ", expMOIRotational, boosterMOIRotational, EPSILON);
double expMOI_tr = 0.0573781722; double expMOI_tr = 0.057405421013859766;
double boosterMOI_tr = spent.getLongitudinalInertia(); double boosterMOI_tr = spent.getLongitudinalInertia();
assertEquals(" Booster transverse MOI is incorrect: ", expMOI_tr, boosterMOI_tr, EPSILON); assertEquals(" Booster transverse MOI is incorrect: ", expMOI_tr, boosterMOI_tr, EPSILON);
} }
@ -964,7 +964,7 @@ public class MassCalculatorTest extends BaseTestCase {
final double expIxx = 0.0122505987; final double expIxx = 0.0122505987;
final double actIxx = launchData.getRotationalInertia(); final double actIxx = launchData.getRotationalInertia();
final double expIyy = 0.0635943662; final double expIyy = 0.06362161493172772;
final double actIyy = launchData.getLongitudinalInertia(); final double actIyy = launchData.getLongitudinalInertia();
assertEquals(" Booster x-axis MOI is incorrect: ", expIxx, actIxx, EPSILON); assertEquals(" Booster x-axis MOI is incorrect: ", expIxx, actIxx, EPSILON);
@ -1010,7 +1010,7 @@ public class MassCalculatorTest extends BaseTestCase {
double boosterMOI_xx = burnout.getRotationalInertia(); double boosterMOI_xx = burnout.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);
double expMOI_tr = 17.78076176335; double expMOI_tr = 17.78078901211703;
double boosterMOI_tr = burnout.getLongitudinalInertia(); double boosterMOI_tr = burnout.getLongitudinalInertia();
assertEquals(" Booster transverse MOI is incorrect: ", expMOI_tr, boosterMOI_tr, EPSILON); assertEquals(" Booster transverse MOI is incorrect: ", expMOI_tr, boosterMOI_tr, EPSILON);
} }
@ -1064,7 +1064,7 @@ public class MassCalculatorTest extends BaseTestCase {
double boosterMOI_xx = boosterData.getRotationalInertia(); double boosterMOI_xx = boosterData.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);
double expMOI_tr = 0.347611843243; double expMOI_tr = 0.34852907557064894;
double boosterMOI_tr = boosterData.getLongitudinalInertia(); double boosterMOI_tr = boosterData.getLongitudinalInertia();
assertEquals(" Booster transverse MOI is incorrect: ", expMOI_tr, boosterMOI_tr, EPSILON); assertEquals(" Booster transverse MOI is incorrect: ", expMOI_tr, boosterMOI_tr, EPSILON);
} }
@ -1111,7 +1111,7 @@ 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 = 0.040598624476; final double expMOI_tr = 0.04062587324372749;
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);
} }