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Implement inertia computations.

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This commit is contained in:
kruland2607 2014-11-17 12:02:26 -06:00
parent 1dbff4a0dc
commit 34a2ca8984
1 changed files with 19 additions and 5 deletions
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24
core/src/net/sf/openrocket/rocketcomponent/TubeFinSet.java
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@ -251,19 +251,33 @@ public class TubeFinSet extends ExternalComponent {
double halflength = length / 2;
if (fins == 1) {
return baseRotation.transform(
new Coordinate(halflength, getOuterRadius() + getBodyRadius(), 0, mass));
return baseRotation.transform(new Coordinate(halflength, getOuterRadius() + getBodyRadius(), 0, mass));
} else {
return new Coordinate(halflength, 0, 0, mass);
return baseRotation.transform(new Coordinate(halflength, 0, 0, mass));
}
}
@Override
public double getLongitudinalUnitInertia() {
// FIXME - this is very likely completely wrong
// Logitudinal Unit Inertia for a single tube fin.
// 1/12 * (3 * (r1^2 + r2^2) + h^2)
return (3 * (MathUtil.pow2(getInnerRadius())) + MathUtil.pow2(getOuterRadius()) + MathUtil.pow2(getLength())) / 12;
final double inertia = (3 * (MathUtil.pow2(getOuterRadius()) + MathUtil.pow2(getInnerRadius())) + MathUtil.pow2(getLength())) / 12;
if (fins == 1) {
return inertia;
}
// translate each to the center of mass.
final double hypot = getOuterRadius() + getBodyRadius();
final double finrotation = 2 * Math.PI / fins;
double angularoffset = 0.0;
double totalInertia = 0.0;
for (int i = 0; i < fins; i++) {
double offset = hypot * Math.cos(angularoffset);
totalInertia += inertia + MathUtil.pow2(offset);
angularoffset += finrotation;
}
return totalInertia;
}
@Override