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Fix Average Thrust Calculation (fixes issue #441)

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Remove test for short time interval before first data point in thrust
curve.  Comment said it was for numerical stability; multiplying by a
small number and then adding doesn't introduce any instabilities I'm
aware of in this code.

Add parentheses to clarify that values are being multiplied by time
intervals, not divided.
This commit is contained in:
Joe Pfeiffer 2018-08-21 17:29:07 -06:00
parent 1448cde5aa
commit ac2339b8b4
1 changed files with 5 additions and 8 deletions
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13
core/src/net/sf/openrocket/motor/ThrustCurveMotor.java
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@ -321,23 +321,20 @@ public class ThrustCurveMotor implements Motor, Comparable<ThrustCurveMotor>, Se
// portion from startTime through time[timeIndex]
double avgImpulse = 0.0;
// For numeric stability.
if( time[timeIndex+1] - startTime > 0.001 ) {
avgImpulse = (MathUtil.map(startTime, time[timeIndex], time[timeIndex+1], thrust[timeIndex], thrust[timeIndex+1]) + thrust[timeIndex+1])
/ 2.0 * (time[timeIndex+1] - startTime);
}
avgImpulse = ((MathUtil.map(startTime, time[timeIndex], time[timeIndex+1], thrust[timeIndex], thrust[timeIndex+1]) + thrust[timeIndex+1])
/ 2.0) * (time[timeIndex+1] - startTime);
// Now add the whole steps;
timeIndex++;
while( timeIndex < time.length -1 && endTime >= time[timeIndex+1] ) {
avgImpulse += (thrust[timeIndex] + thrust[timeIndex+1]) / 2.0 * (time[timeIndex+1]-time[timeIndex]);
while ( timeIndex < time.length -1 && endTime >= time[timeIndex+1] ) {
avgImpulse += ((thrust[timeIndex] + thrust[timeIndex+1]) / 2.0) * (time[timeIndex+1]-time[timeIndex]);
timeIndex++;
}
// Now add the bit after the last time index
if ( timeIndex < time.length -1 ) {
double endInstImpulse = MathUtil.map( endTime, time[timeIndex], time[timeIndex+1], thrust[timeIndex], thrust[timeIndex+1]);
avgImpulse += (thrust[timeIndex] + endInstImpulse) / 2.0 * (endTime - time[timeIndex]);
avgImpulse += ((thrust[timeIndex] + endInstImpulse) / 2.0) * (endTime - time[timeIndex]);
}
return avgImpulse / (endTime - startTime);