Merge pull request #505 from teyrana/fix_500_cg
[fixes #500] May Calculate CG for fins on zero-dimension mounts
This commit is contained in:
Wes Cravens
GitHub
commit
c5733b9b68
@ -412,8 +412,12 @@ public abstract class FinSet extends ExternalComponent implements RingInstanceab
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- outerArcAngle * filletRadius * filletRadius / 2
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- innerArcAngle * bodyRadius * bodyRadius / 2);
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// each fin has a fillet on each side
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crossSectionArea *= 2;
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if(Double.isNaN(crossSectionArea)) {
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crossSectionArea = 0.;
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}else {
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// each fin has a fillet on each side
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crossSectionArea *= 2;
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}
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// heuristic, relTo the body center
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double yCentroid = bodyRadius + filletRadius /5;
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@ -435,8 +439,8 @@ public abstract class FinSet extends ExternalComponent implements RingInstanceab
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* 5. Return twice that since there is a fillet on each side of the fin.
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*/
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protected Coordinate calculateFilletVolumeCentroid() {
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Coordinate[] bodyPoints = this.getBodyPoints();
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if (0 == bodyPoints.length) {
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Coordinate[] mountPoints = this.getRootPoints();
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if( null == mountPoints ){
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return Coordinate.ZERO;
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}
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@ -446,11 +450,9 @@ public abstract class FinSet extends ExternalComponent implements RingInstanceab
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}
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Coordinate filletVolumeCentroid = Coordinate.ZERO;
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Coordinate prev = bodyPoints[0];
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for (int index = 1; index < bodyPoints.length; index++) {
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final Coordinate cur = bodyPoints[index];
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Coordinate prev = mountPoints[0];
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for (int index = 1; index < mountPoints.length; index++) {
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final Coordinate cur = mountPoints[index];
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// cross section at mid-segment
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final double xAvg = (prev.x + cur.x) / 2;
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@ -469,9 +471,6 @@ public abstract class FinSet extends ExternalComponent implements RingInstanceab
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prev = cur;
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}
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// translate to be relative to the fin-lead-root
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filletVolumeCentroid = filletVolumeCentroid.sub(getAxialFront(), 0,0);
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if (finCount == 1) {
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Transformation rotation = Transformation.rotate_x( getAngleOffset());
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return rotation.transform(filletVolumeCentroid);
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@ -541,7 +540,7 @@ public abstract class FinSet extends ExternalComponent implements RingInstanceab
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final double xTabTrail_body = xFinFront_body + xTabTrail_fin;
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// always returns x coordinates relTo fin front:
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Coordinate[] upperCurve = getBodyPoints( xTabFront_body, xTabTrail_body );
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Coordinate[] upperCurve = getMountInterval( xTabFront_body, xTabTrail_body );
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// locate relative to fin/body centerline
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upperCurve = translatePoints( upperCurve, -xFinFront_body, 0.0);
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@ -573,14 +572,14 @@ public abstract class FinSet extends ExternalComponent implements RingInstanceab
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private Coordinate calculateSinglePlanformCentroid(){
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final Coordinate finFront = getFinFront();
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final Coordinate[] upperCurve = translatePoints( getFinPoints(), finFront.x, finFront.y );
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final Coordinate[] lowerCurve = getBodyPoints();
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final Coordinate[] upperCurve = getFinPoints();
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final Coordinate[] lowerCurve = getRootPoints();
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final Coordinate[] totalCurve = combineCurves( upperCurve, lowerCurve);
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Coordinate planformCentroid = calculateCurveIntegral( totalCurve );
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// return as a position relative to fin-root
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return planformCentroid.sub(finFront.x,0,0);
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return planformCentroid.add(0., finFront.y, 0);
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}
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/**
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@ -1042,11 +1041,12 @@ public abstract class FinSet extends ExternalComponent implements RingInstanceab
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*
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* @return points representing the fin-root points, relative to ( x: fin-front, y: centerline ) i.e. relto: fin Component reference point
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*/
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public Coordinate[] getBodyPoints() {
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final double xFinStart = getAxialFront();
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final double xFinEnd = xFinStart+getLength();
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public Coordinate[] getMountPoints() {
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if( null == parent){
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return null;
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}
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return getBodyPoints( xFinStart, xFinEnd);
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return getMountInterval(0., parent.getLength());
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}
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/**
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@ -1055,18 +1055,21 @@ public abstract class FinSet extends ExternalComponent implements RingInstanceab
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* @return points representing the fin-root points, relative to ( x: fin-front, y: fin-root-radius )
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*/
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public Coordinate[] getRootPoints(){
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if( null == parent){
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return new Coordinate[]{Coordinate.ZERO};
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}
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final Coordinate finLead = getFinFront();
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final double finTailX = finLead.x + getLength();
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final Coordinate[] bodyPoints = getBodyPoints( finLead.x, finTailX);
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final Coordinate[] bodyPoints = getMountInterval( finLead.x, finTailX);
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return translatePoints(bodyPoints, -finLead.x, -finLead.y);
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}
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private Coordinate[] getBodyPoints( final double xStart, final double xEnd ) {
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if( null == parent){
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return new Coordinate[]{Coordinate.ZERO};
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}
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private Coordinate[] getMountInterval( final double xStart, final double xEnd ) {
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// System.err.println(String.format(" .... >> mount interval/x: ( %g, %g)]", xStart, xEnd));
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// for a simple bodies, one increment is perfectly accurate.
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int divisionCount = 1;
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@ -1125,7 +1128,8 @@ public abstract class FinSet extends ExternalComponent implements RingInstanceab
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buf.append( getPointDescr( this.getFinPoints(), "Fin Points", ""));
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if (null != parent) {
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buf.append( getPointDescr( this.getBodyPoints(), "Body Points", ""));
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buf.append( getPointDescr( this.getRootPoints(), "Root Points", ""));
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buf.append( getPointDescr( this.getMountPoints(), "Mount Points", ""));
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}
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if( ! this.isTabTrivial() ) {
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@ -1179,13 +1179,13 @@ public class FreeformFinSetTest extends BaseTestCase {
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final Coordinate[] finPointsFromBody = FinSet.translatePoints( finPoints, 0.0, fins.getFinFront().y);
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{ // body points (relative to body)
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final Coordinate[] bodyPoints = fins.getBodyPoints();
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final Coordinate[] mountPoints = fins.getMountPoints();
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assertEquals("Method should only generate minimal points for a conical transition fin body! ", 2, bodyPoints.length );
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assertEquals("incorrect body points! ", finPointsFromBody[0].x, bodyPoints[0].x, EPSILON);
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assertEquals("incorrect body points! ", finPointsFromBody[0].y, bodyPoints[0].y, EPSILON);
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assertEquals("incorrect body points! ", finPointsFromBody[finPoints.length-1].x, bodyPoints[1].x, EPSILON);
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assertEquals("incorrect body points! ", finPointsFromBody[finPoints.length-1].y, bodyPoints[1].y, EPSILON);
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assertEquals("Method should only generate minimal points for a conical transition fin body! ", 2, mountPoints.length );
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assertEquals("incorrect body points! ", finPointsFromBody[0].x, mountPoints[0].x, EPSILON);
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assertEquals("incorrect body points! ", finPointsFromBody[0].y, mountPoints[0].y, EPSILON);
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assertEquals("incorrect body points! ", finPointsFromBody[finPoints.length-1].x, mountPoints[1].x, EPSILON);
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assertEquals("incorrect body points! ", finPointsFromBody[finPoints.length-1].y, mountPoints[1].y, EPSILON);
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}
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{ // root points (relative to fin-front)
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final Coordinate[] rootPoints = fins.getRootPoints();
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@ -1203,18 +1203,16 @@ public class FreeformFinSetTest extends BaseTestCase {
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final Rocket rkt = createTemplateRocket();
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final FreeformFinSet fins = (FreeformFinSet) rkt.getChild(0).getChild(2).getChild(0);
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final Coordinate finFront = fins.getFinFront();
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final Coordinate[] finPoints = fins.getFinPoints();
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final Coordinate[] finPointsFromBody = FinSet.translatePoints( finPoints, finFront.x, finFront.y);
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{ // body points (relative to body)
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final Coordinate[] bodyPoints = fins.getBodyPoints();
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final Coordinate[] bodyPoints = fins.getMountPoints();
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assertEquals("Method should only generate minimal points for a conical transition fin body! ", 2, bodyPoints.length );
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assertEquals("incorrect body points! ", finPointsFromBody[0].x, bodyPoints[0].x, EPSILON);
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assertEquals("incorrect body points! ", finPointsFromBody[0].y, bodyPoints[0].y, EPSILON);
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assertEquals("incorrect body points! ", finPointsFromBody[finPoints.length-1].x, bodyPoints[1].x, EPSILON);
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assertEquals("incorrect body points! ", finPointsFromBody[finPoints.length-1].y, bodyPoints[1].y, EPSILON);
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assertEquals("incorrect body points! ", 0.0, bodyPoints[0].x, EPSILON);
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assertEquals("incorrect body points! ", 1.0, bodyPoints[0].y, EPSILON);
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assertEquals("incorrect body points! ", 1.0, bodyPoints[1].x, EPSILON);
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assertEquals("incorrect body points! ", 0.5, bodyPoints[1].y, EPSILON);
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}
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{ // body points (relative to root)
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final Coordinate[] rootPoints = fins.getRootPoints();
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@ -1236,7 +1234,6 @@ public class FreeformFinSetTest extends BaseTestCase {
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final Coordinate finFront = fins.getFinFront();
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final Coordinate[] finPoints = fins.getFinPoints();
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{ // fin points (relative to fin) // preconditions
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assertEquals(4, finPoints.length);
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@ -1281,35 +1278,30 @@ public class FreeformFinSetTest extends BaseTestCase {
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}
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}
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}{ // body points (relative to body)
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// translate from fin-frame to body-frame
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final Coordinate[] finPointsFromBody = FinSet.translatePoints( fins.getFinPoints(), finFront.x, finFront.y );
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final Coordinate[] bodyPoints = fins.getBodyPoints();
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assertEquals(101, bodyPoints.length);
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final Coordinate expectedEndPoint = finPointsFromBody[ finPoints.length-1];
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final Coordinate[] mountPoints = fins.getMountPoints();
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assertEquals(101, mountPoints.length);
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// trivial, and uninteresting:
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assertEquals("incorrect body points! ", finPointsFromBody[0].x, bodyPoints[0].x, EPSILON);
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assertEquals("incorrect body points! ", finPointsFromBody[0].y, bodyPoints[0].y, EPSILON);
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assertEquals("incorrect body points! ", 0.0, mountPoints[0].x, EPSILON);
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assertEquals("incorrect body points! ", 0.0, mountPoints[0].y, EPSILON);
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// n.b.: This should match EXACTLY the end point of the fin. (in fin coordinates)
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assertEquals("incorrect body points! ", expectedEndPoint.x, bodyPoints[bodyPoints.length-1].x, EPSILON);
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assertEquals("incorrect body points! ", expectedEndPoint.y, bodyPoints[bodyPoints.length-1].y, EPSILON);
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assertEquals("incorrect body points! ", 1.0, mountPoints[mountPoints.length-1].x, EPSILON);
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assertEquals("incorrect body points! ", 1.0, mountPoints[mountPoints.length-1].y, EPSILON);
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{// the tests within this scope is are rather fragile, and may break for reasons other than bugs :(
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// the number of points is somewhat arbitrary, but if this test fails, the rest *definitely* will.
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assertEquals("Method is generating how many points, in general? ", 101, bodyPoints.length );
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assertEquals("Method is generating how many points, in general? ", 101, mountPoints.length );
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final int[] testIndices = { 2, 5, 61, 88};
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final double[] expectedX = { 0.036, 0.06, 0.508, 0.724};
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final int[] testIndices = { 3, 12, 61, 88};
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final double[] expectedX = { 0.03, 0.12, 0.61, 0.88};
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for( int testCase = 0; testCase < testIndices.length; testCase++){
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final int testIndex = testIndices[testCase];
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assertEquals(String.format("Body points @ %d :: x coordinate mismatch!", testIndex),
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expectedX[testCase], bodyPoints[testIndex].x, EPSILON);
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expectedX[testCase], mountPoints[testIndex].x, EPSILON);
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assertEquals(String.format("Body points @ %d :: y coordinate mismatch!", testIndex),
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body.getRadius(bodyPoints[testIndex].x), bodyPoints[testIndex].y, EPSILON);
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body.getRadius(mountPoints[testIndex].x), mountPoints[testIndex].y, EPSILON);
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}
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}
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}
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@ -90,7 +90,7 @@ public class TrapezoidFinSetTest extends BaseTestCase {
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final Rocket rkt = createSimpleTrapezoidalFin();
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final TrapezoidFinSet fins = (TrapezoidFinSet)rkt.getChild(0).getChild(0).getChild(0);
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// This is a simple square fin with sides of 1.0.
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// This is a simple square fin with sides of 0.1.
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fins.setFinShape(0.1, 0.1, 0.0, 0.1, .005);
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// should return a single-fin-planform area
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@ -170,14 +170,14 @@ public class TrapezoidFinSetTest extends BaseTestCase {
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// / \
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// [0] +--------+ [3]
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//
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assertEquals(0.06, fins.getLength(), EPSILON);
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assertEquals("Body radius doesn't match: ", 0.1, body.getOuterRadius(), EPSILON);
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final Coordinate actVolume = fins.calculateFilletVolumeCentroid();
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assertEquals("Line volume doesn't match: ", 5.973e-07, actVolume.weight, EPSILON);
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assertEquals("Line mass center.x doesn't match: ", 0.03, actVolume.x, EPSILON);
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assertEquals("Line mass center.y doesn't match: ", 0.101, actVolume.y, EPSILON);
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assertEquals("Fin volume doesn't match: ", 5.973e-07, actVolume.weight, EPSILON);
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assertEquals("Fin mass center.x doesn't match: ", 0.03, actVolume.x, EPSILON);
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assertEquals("Fin mass center.y doesn't match: ", 0.101, actVolume.y, EPSILON);
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{ // and then, check that the fillet volume feeds into a correct overall CG:
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@ -189,7 +189,6 @@ public class TrapezoidFinSetTest extends BaseTestCase {
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@Test
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public void testTrapezoidCGComputation() {
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{
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// This is a simple square fin with sides of 1.0.
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TrapezoidFinSet fins = new TrapezoidFinSet();
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@ -200,9 +199,7 @@ public class TrapezoidFinSetTest extends BaseTestCase {
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assertEquals(1.0, fins.getPlanformArea(), 0.001);
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assertEquals(0.5, coords.x, 0.001);
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assertEquals(0.5, coords.y, 0.001);
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}
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{
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}{
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// This is a trapezoid. Height 1, root 1, tip 1/2 no sweep.
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// It can be decomposed into a rectangle followed by a triangle
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// +---+
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@ -218,7 +215,77 @@ public class TrapezoidFinSetTest extends BaseTestCase {
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assertEquals(0.3889, coords.x, 0.001);
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assertEquals(0.4444, coords.y, 0.001);
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}
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}
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@Test
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public void testGetBodyPoints_phantomMount() {
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final Rocket rkt = createSimpleTrapezoidalFin();
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// set mount to have zero-dimensions:
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final BodyTube mount = (BodyTube)rkt.getChild(0).getChild(0);
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mount.setLength(0.0);
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mount.setOuterRadius(0.0);
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assertEquals( 0, mount.getLength(), 0.00001);
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assertEquals( 0, mount.getOuterRadius(), 0.00001);
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assertEquals( 0, mount.getInnerRadius(), 0.00001);
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final TrapezoidFinSet fins = (TrapezoidFinSet)mount.getChild(0);
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final Coordinate[] mountPoints = fins.getMountPoints();
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assertEquals(2, mountPoints.length );
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assertEquals( 0.00, mountPoints[0].x, 0.00001);
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assertEquals( 0.00, mountPoints[0].y, 0.00001);
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assertEquals( 0.00, mountPoints[1].x, 0.00001);
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assertEquals( 0.00, mountPoints[1].y, 0.00001);
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}
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@Test
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public void testGetBodyPoints_zeroLengthMount() {
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final Rocket rkt = createSimpleTrapezoidalFin();
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// set mount to have zero-dimensions:
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final BodyTube mount = (BodyTube)rkt.getChild(0).getChild(0);
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mount.setLength(0.0);
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mount.setOuterRadius(0.1);
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mount.setInnerRadius(0.08);
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assertEquals( 0, mount.getLength(), 0.00001);
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assertEquals( 0.1, mount.getOuterRadius(), 0.00001);
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assertEquals( 0.08, mount.getInnerRadius(), 0.00001);
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final TrapezoidFinSet fins = (TrapezoidFinSet)mount.getChild(0);
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final Coordinate[] mountPoints = fins.getMountPoints();
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assertEquals(2, mountPoints.length );
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assertEquals( 0.0, mountPoints[0].x, 0.00001);
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assertEquals( 0.1, mountPoints[0].y, 0.00001);
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assertEquals( 0.0, mountPoints[1].x, 0.00001);
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assertEquals( 0.1, mountPoints[1].y, 0.00001);
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}
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@Test
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public void testTrapezoidCGComputation_phantomMount() {
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final Rocket rkt = createSimpleTrapezoidalFin();
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// set mount to have zero-dimensions:
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final BodyTube mount = (BodyTube)rkt.getChild(0).getChild(0);
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mount.setLength(0.0);
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mount.setOuterRadius(0.0);
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assertEquals( 0, mount.getLength(), 0.00001);
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assertEquals( 0, mount.getOuterRadius(), 0.00001);
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assertEquals( 0, mount.getInnerRadius(), 0.00001);
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final TrapezoidFinSet fins = (TrapezoidFinSet)mount.getChild(0);
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assertEquals( 0.06, fins.getLength(), 0.00001);
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assertEquals( 0.05, fins.getHeight(), 0.00001);
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assertEquals( 0.06, fins.getRootChord(), 0.00001);
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assertEquals( 0.02, fins.getTipChord(), 0.00001);
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final Coordinate coords = fins.getCG();
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assertEquals(0.002, fins.getPlanformArea(), 0.001);
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assertEquals(0.03, coords.x, 0.001);
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assertEquals(0.02, coords.y, 0.001);
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}
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@Test
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