Dodecarotor Cox Mod - Issues

[mariepierb]

Hi!
I am trying to simulate a Dodecarotor Cox multicopter. I started my mod from your hexacopter vehicle, and followed the numbering so that it matches the PX4 - QGC numbering found here (https://docs.px4.io/master/en/airframes/airframe_reference.html).

Dodecarotor.java:
package me.drton.jmavsim.vehicle;

import me.drton.jmavsim.Rotor;
import me.drton.jmavsim.World;

import javax.vecmath.Matrix3d;
import javax.vecmath.Vector3d;

/**

• Generic Dodecarotor model.
  */
  public class Dodecarotor extends AbstractMulticopter {
  private static final int rotorsNum = 12;
  private Vector3d[] rotorPositions = new Vector3d[rotorsNum];
  // private int[] rotorRotations = new int[rotorsNum];

  /**

  • Generic Dodecarotor constructor.

  • @param world world where to place the vehicle

  • @param modelName filename of model to load, in .obj format

  • @param orientation "x" or "+"

  • @param armLength length of arm from center (m)

  • @param rotorThrust full thrust of one rotor (N)

  • @param rotorTorque torque at full thrust of one rotor (Nm)

  • @param rotorTimeConst spin-up time of rotor

  • @param rotorHeight height of propeller from center point (m)

  • @param rotorsOffset rotors positions offset from gravity center

  • @param showGui false if the GUI has been disabled
    */
    public Dodecarotor(World world, String modelName, String orientation, double armLength,
    double rotorThrust, double rotorTorque, double rotorTimeConst, double rotorHeight,
    Vector3d rotorsOffset, boolean showGui) {
    super(world, modelName, showGui);

     rotorPositions[0] = new Vector3d(0.0, armLength, -rotorHeight);
     rotorPositions[1] = new Vector3d(0.0,-armLength, -rotorHeight);
     rotorPositions[2] = new Vector3d(armLength * Math.sin(Math.PI / 3),
     								-armLength * Math.cos(Math.PI / 3), -rotorHeight);
     rotorPositions[3] = new Vector3d(-armLength * Math.sin(Math.PI / 3),
     								armLength * Math.cos(Math.PI / 3), -rotorHeight);
     rotorPositions[4] = new Vector3d(armLength * Math.sin(Math.PI / 3),
     								armLength * Math.cos(Math.PI / 3), -rotorHeight);
     rotorPositions[5] = new Vector3d(-armLength * Math.sin(Math.PI / 3),
     								-armLength * Math.cos(Math.PI / 3), -rotorHeight);
     rotorPositions[6] = new Vector3d(0.0, armLength, rotorHeight);
     rotorPositions[7] = new Vector3d(0.0,-armLength, rotorHeight);
     rotorPositions[8] = new Vector3d(armLength * Math.sin(Math.PI / 3),
     								-armLength * Math.cos(Math.PI / 3), rotorHeight);
     rotorPositions[9] = new Vector3d(-armLength * Math.sin(Math.PI / 3),
     								armLength * Math.cos(Math.PI / 3), rotorHeight);
     rotorPositions[10] = new Vector3d(armLength * Math.sin(Math.PI / 3),
     								armLength * Math.cos(Math.PI / 3), rotorHeight);
     rotorPositions[11] = new Vector3d(-armLength * Math.sin(Math.PI / 3),
     								-armLength * Math.cos(Math.PI / 3), rotorHeight);				
    

    if (orientation.equals("x") || orientation.equals("X")) {
    Matrix3d r = new Matrix3d();
    r.rotZ(-Math.PI / 2);
    for (int i = 0; i < rotorsNum; i++) {
    r.transform(rotorPositions[i]);
    }

    } else {
    throw new RuntimeException("Unknown orientation: " + orientation);
    }
    for (int i = 0; i < rotors.length; i++) {
    rotorPositions[i].add(rotorsOffset);
    Rotor rotor = rotors[i];
    rotor.setFullThrust((i > 5) ? 0.9*rotorThrust : rotorThrust); //Lower propeller reduced efficiency
    rotor.setFullTorque((i == 6 || i == 3 || i == 4 || i == 6 || i == 8 || i == 11) ? -rotorTorque : rotorTorque);
    rotor.setTimeConstant(rotorTimeConst);
    }
    }

  @OverRide
  protected int getRotorsNum() {
  return rotorsNum;
  }

  @OverRide
  protected Vector3d getRotorPosition(int i) {
  return rotorPositions[i];
  }
  }

I am calling it from Simulator.java using these specific values :

private AbstractMulticopter buildMulticopter() {
Vector3d gc = new Vector3d(0.0, 0.0, 0.0); // gravity center

	AbstractMulticopter vehicle = new Dodecarotor(world, DEFAULT_VEHICLE_MODEL, "x",
                                           0.6096, 306.26, 19.07, 0.005, 0.114, gc, SHOW_GUI);
	
    Matrix3d I = new Matrix3d();
    // Moments of inertia
    I.m00 = 39.0;  // X
    I.m11 = 39.0;  // Y
    I.m22 = 52.0;  // Z
    vehicle.setMomentOfInertia(I);
    vehicle.setMass(100);
    vehicle.setDragMove(2);
    SimpleSensors sensors = new SimpleSensors();
    sensors.setGPSInterval(50);
    sensors.setGPSDelay(200);
    sensors.setNoise_Acc(0.05f);
    sensors.setNoise_Gyo(0.01f);
    sensors.setNoise_Mag(0.005f);
    sensors.setNoise_Prs(0.1f);
    vehicle.setSensors(sensors, getSimMillis());
    //v.setDragRotate(0.1);

    return vehicle;
}

The build of the code is successful, however, my drone does not take off. I believe the error might lies in AbstractMulticopter.java . Can you help me? Or is there resources anywhere to help me build my own airframe configurations?

[zondafeng]

do you solve it? i have a similar question. i want to modify the relationship between thrust/moment and rotation speed.