git.gag.com Git - debian/openrocket/blob - src/net/sf/openrocket/rocketcomponent/ThrustCurveMotor.java

   1 package net.sf.openrocket.rocketcomponent;
   2
   3 import net.sf.openrocket.util.Coordinate;
   4
   5 /**
   6  * A class of motors specified by a fixed thrust curve.  This is the most
   7  * accurate for solid rocket motors.
   8  *
   9  * @author Sampo Niskanen <sampo.niskanen@iki.fi>
  10  */
  11 public class ThrustCurveMotor extends Motor {
  12
  13         private final double[] time;
  14         private final double[] thrust;
  15         private final Coordinate[] cg;
  16
  17         private final double totalTime;
  18         private final double maxThrust;
  19
  20
  21         /**
  22          * Sole constructor.  Sets all the properties of the motor.
  23          *
  24          * @param manufacturer  the manufacturer of the motor.
  25          * @param designation   the designation of the motor.
  26          * @param description   extra description of the motor.
  27          * @param diameter      diameter of the motor.
  28          * @param length        length of the motor.
  29          * @param time          the time points for the thrust curve.
  30          * @param thrust        thrust at the time points.
  31          * @param cg            cg at the time points.
  32          */
  33         public ThrustCurveMotor(String manufacturer, String designation, String description,
  34                         Motor.Type type, double[] delays, double diameter, double length,
  35                         double[] time, double[] thrust, Coordinate[] cg) {
  36                 super(manufacturer, designation, description, type, delays, diameter, length);
  37
  38                 double max = -1;
  39
  40                 // Check argument validity
  41                 if ((time.length != thrust.length) || (time.length != cg.length)) {
  42                         throw new IllegalArgumentException("Array lengths do not match, " +
  43                                         "time:" + time.length + " thrust:" + thrust.length +
  44                                         " cg:" + cg.length);
  45                 }
  46                 if (time.length < 2) {
  47                         throw new IllegalArgumentException("Too short thrust-curve, length=" +
  48                                         time.length);
  49                 }
  50                 for (int i=0; i < time.length-1; i++) {
  51                         if (time[i+1] < time[i]) {
  52                                 throw new IllegalArgumentException("Time goes backwards, " +
  53                                                 "time[" + i + "]=" + time[i] + " " +
  54                                                 "time[" + (i+1) + "]=" + time[i+1]);
  55                         }
  56                 }
  57                 if (time[0] != 0) {
  58                         throw new IllegalArgumentException("Curve starts at time=" + time[0]);
  59                 }
  60                 for (double t: thrust) {
  61                         if (t < 0) {
  62                                 throw new IllegalArgumentException("Negative thrust.");
  63                         }
  64                         if (t > max)
  65                                 max = t;
  66                 }
  67
  68                 this.maxThrust = max;
  69                 this.time = time.clone();
  70                 this.thrust = thrust.clone();
  71                 this.cg = cg.clone();
  72                 this.totalTime = time[time.length-1];
  73         }
  74
  75
  76         @Override
  77         public double getTotalTime() {
  78                 return totalTime;
  79         }
  80
  81         @Override
  82         public double getMaxThrust() {
  83                 return maxThrust;
  84         }
  85
  86         @Override
  87         public double getThrust(double t) {
  88                 if ((t < 0) || (t > totalTime))
  89                         return 0;
  90
  91                 for (int i=0; i < time.length-1; i++) {
  92                         if ((t >= time[i]) && (t <= time[i+1])) {
  93                                 double delta = time[i+1] - time[i];
  94                                 t = t - time[i];
  95                                 return thrust[i] * (1 - t/delta) + thrust[i+1] * (t/delta);
  96                         }
  97                 }
  98                 assert false : "Should not be reached.";
  99                 return 0;
 100         }
 101
 102
 103         @Override
 104         public Coordinate getCG(double t) {
 105                 if (t <= 0)
 106                         return cg[0];
 107                 if (t >= totalTime)
 108                         return cg[cg.length-1];
 109
 110                 for (int i=0; i < time.length-1; i++) {
 111                         if ((t >= time[i]) && (t <= time[i+1])) {
 112                                 double delta = time[i+1] - time[i];
 113                                 t = t - time[i];
 114                                 return cg[i].multiply(1 - t/delta).add(cg[i+1].multiply(t/delta));
 115                         }
 116                 }
 117                 assert false : "Should not be reached.";
 118                 return cg[cg.length-1];
 119         }
 120
 121 }