Coaxial octocopter Gazebo simulation problems

Hi,

I’m trying to create a coaxial octocopter for a research project. I’m trying start start out with creating a very simple model to fly in a Gazebo simulation, but I have some problems, since I’m not that experienced with either PX4 or Gazebo. I have managed to load the simple model into Gazebo and have 8 motors that all spins, but as soon as I try to takeoff the drone will flip over. I’m using version 1.13.0 of PX4.

I’m using the following files to try and create the drone, if somebody wants to replicate it. Let me know if anything is missing. Most of them was modified from other code I have found, so any help in improvements in them are appreciated :slight_smile:

The mixer file

# Octo coaxial

R: 8c

The geometry file located in init.d-posix being used.

#!/bin/sh
#
# @name Generic 10" Octo coaxial geometry
#
# @type Octorotor Coaxial
# @class Copter
#
# @output MAIN1 motor 1
# @output MAIN2 motor 2
# @output MAIN3 motor 3
# @output MAIN4 motor 4
# @output MAIN5 motor 5
# @output MAIN6 motor 6
# @output MAIN7 motor 7
# @output MAIN8 motor 8
#
# @maintainer Lorenz Meier <lorenz@px4.io>
#
# @board bitcraze_crazyflie exclude
#

. ${R}etc/init.d/rc.mc_defaults

set MIXER octo_cox

set PWM_OUT 12345678

The SDF file being used:


<?xml version='1.0'?>
<sdf version='1.6'>
  <model name='octo_cox'>
    <!--Drone body -->
    <link name='base_link'>
      <pose>0 0 0 0 -0 0</pose>
      <inertial>
        <pose>0 0 0 0 -0 0</pose>
        <mass>6</mass>
        <inertia>
          <ixx>0.762625</ixx>
          <ixy>0</ixy>
          <ixz>0</ixz>
          <iyy>0.762625</iyy>
          <iyz>0</iyz>
          <izz>1.369</izz>
        </inertia>
      </inertial>
      <collision name='base_link_inertia_collision'>
        <pose>0 0 0 0 -0 0</pose>
        <geometry>
          <box>
            <size>0.74 0.74 0.25</size>
          </box>
        </geometry>
        <surface>
          <contact>
            <ode>
              <min_depth>0.001</min_depth>
              <max_vel>0</max_vel>
            </ode>
          </contact>
          <friction>
            <ode/>
          </friction>
        </surface>
      </collision>
      <visual name='base_link_inertia_visual'>
        <pose>0 0 0.125 1.57 0 0</pose>
        <geometry>
          <mesh>
            <scale>0.3 0.3 0.3</scale>
            <uri>model://octo_cox/meshes/Part1.dae</uri>
          </mesh>
        </geometry>
      </visual>
      <gravity>1</gravity>
      <velocity_decay/>
    </link>
    <link name='/imu_link'>
      <pose>0 0 0 0 -0 0</pose>
      <inertial>
        <pose>0 0 0 0 -0 0</pose>
        <mass>0.015</mass>
        <inertia>
          <ixx>1e-05</ixx>
          <ixy>0</ixy>
          <ixz>0</ixz>
          <iyy>1e-05</iyy>
          <iyz>0</iyz>
          <izz>1e-05</izz>
        </inertia>
      </inertial>
    </link>
    <joint name='/imu_joint' type='revolute'>
      <child>/imu_link</child>
      <parent>base_link</parent>
      <axis>
        <xyz>1 0 0</xyz>
        <limit>
          <lower>0</lower>
          <upper>0</upper>
          <effort>0</effort>
          <velocity>0</velocity>
        </limit>
        <dynamics>
          <spring_reference>0</spring_reference>
          <spring_stiffness>0</spring_stiffness>
        </dynamics>
        <use_parent_model_frame>1</use_parent_model_frame>
      </axis>
    </joint>

    <!-- Rotor 0 (CCW) -->
    <link name='rotor_0'>
      <pose>0.520429 -0.435000 0.220 0 -0 0</pose>
      <inertial>
        <pose>0 0 0 0 -0 0</pose>
        <mass>0.05</mass>
        <inertia>
          <ixx>9.75e-07</ixx>
          <ixy>0</ixy>
          <ixz>0</ixz>
          <iyy>0.000273104</iyy>
          <iyz>0</iyz>
          <izz>0.000274004</izz>
        </inertia>
      </inertial>
      <collision name='rotor_0_collision'>
        <pose>0 0 0 0 -0 0</pose>
        <geometry>
          <cylinder>
            <length>0.005</length>
            <radius>0.128</radius>
          </cylinder>
        </geometry>
        <surface>
          <contact>
            <ode/>
          </contact>
          <friction>
            <ode/>
          </friction>
        </surface>
      </collision>
      <visual name='rotor_0_visual'>
        <pose>0 0 0 0 -0 0</pose>
        <geometry>
          <mesh>
            <scale>1.5 1.5 1.5</scale>
            <uri>model://sdu_description/meshes/prop_ccw.dae</uri>
          </mesh>
        </geometry>
        <material>
          <script>
            <name>Gazebo/DarkGrey</name>
            <uri>file://media/materials/scripts/gazebo.material</uri>
          </script>
        </material>
      </visual>
      <gravity>1</gravity>
      <velocity_decay/>
    </link>
    <joint name='rotor_0_joint' type='revolute'>
      <child>rotor_0</child>
      <parent>base_link</parent>
      <axis>
        <xyz>0 0 1</xyz>
        <limit>
          <lower>-1e+16</lower>
          <upper>1e+16</upper>
        </limit>
        <dynamics>
          <spring_reference>0</spring_reference>
          <spring_stiffness>0</spring_stiffness>
        </dynamics>
        <use_parent_model_frame>1</use_parent_model_frame>
      </axis>
    </joint>

    <!-- Rotor 1 (CW) -->
    <link name='rotor_1'>
	<pose>0.550429 0.535000 0.220 0 -0 0</pose>
      <inertial>
        <pose>0 0 0 0 -0 0</pose>
        <mass>0.05</mass>
        <inertia>
          <ixx>9.75e-07</ixx>
          <ixy>0</ixy>
          <ixz>0</ixz>
          <iyy>0.000273104</iyy>
          <iyz>0</iyz>
          <izz>0.000274004</izz>
        </inertia>
      </inertial>
      <collision name='rotor_1_collision'>
        <pose>0 0 0 0 -0 0</pose>
        <geometry>
          <cylinder>
            <length>0.005</length>
            <radius>0.128</radius>
          </cylinder>
        </geometry>
        <surface>
          <contact>
            <ode/>
          </contact>
          <friction>
            <ode/>
          </friction>
        </surface>
      </collision>
      <visual name='rotor_1_visual'>
        <pose>0 0 0 0 -0 0</pose>
        <geometry>
          <mesh>
            <scale>1.5 1.5 1.5</scale>
            <uri>model://sdu_description/meshes/prop_cw.dae</uri>
          </mesh>
        </geometry>
        <material>
          <script>
            <name>Gazebo/Blue</name>
            <uri>file://media/materials/scripts/gazebo.material</uri>
          </script>
        </material>
      </visual>
      <gravity>1</gravity>
      <velocity_decay/>
    </link>
    <joint name='rotor_1_joint' type='revolute'>
      <child>rotor_1</child>
      <parent>base_link</parent>
      <axis>
        <xyz>0 0 1</xyz>
        <limit>
          <lower>-1e+16</lower>
          <upper>1e+16</upper>
        </limit>
        <dynamics>
          <spring_reference>0</spring_reference>
          <spring_stiffness>0</spring_stiffness>
        </dynamics>
        <use_parent_model_frame>1</use_parent_model_frame>
      </axis>
    </joint>

    <!-- Rotor 2 (CCW) -->
    <link name='rotor_2'>
      <pose>-0.40 0.535000 0.220 0 -0 0</pose>
      <inertial>
        <pose>0 0 0 0 -0 0</pose>
        <mass>0.05</mass>
        <inertia>
          <ixx>9.75e-07</ixx>
          <ixy>0</ixy>
          <ixz>0</ixz>
          <iyy>0.000273104</iyy>
          <iyz>0</iyz>
          <izz>0.000274004</izz>
        </inertia>
      </inertial>
      <collision name='rotor_2_collision'>
        <pose>0 0 0 0 -0 0</pose>
        <geometry>
          <cylinder>
            <length>0.005</length>
            <radius>0.128</radius>
          </cylinder>
        </geometry>
        <surface>
          <contact>
            <ode/>
          </contact>
          <friction>
            <ode/>
          </friction>
        </surface>
      </collision>
      <visual name='rotor_2_visual'>
        <pose>0 0 0 0 -0 0</pose>
        <geometry>
          <mesh>
            <scale>1.5 1.5 1.5</scale>
            <uri>model://sdu_description/meshes/prop_ccw.dae</uri>
          </mesh>
        </geometry>
        <material>
          <script>
            <name>Gazebo/DarkGrey</name>
            <uri>file://media/materials/scripts/gazebo.material</uri>
          </script>
        </material>
      </visual>
      <gravity>1</gravity>
      <velocity_decay/>
    </link>
    <joint name='rotor_2_joint' type='revolute'>
      <child>rotor_2</child>
      <parent>base_link</parent>
      <axis>
        <xyz>0 0 1</xyz>
        <limit>
          <lower>-1e+16</lower>
          <upper>1e+16</upper>
        </limit>
        <dynamics>
          <spring_reference>0</spring_reference>
          <spring_stiffness>0</spring_stiffness>
        </dynamics>
        <use_parent_model_frame>1</use_parent_model_frame>
      </axis>
    </joint>

    <!-- Rotor 3 (CW) -->
    <link name='rotor_3'>
      <pose>-0.350429 -0.405000 0.220 0 -0 0</pose>
      <inertial>
        <pose>0 0 0 0 -0 0</pose>
        <mass>0.05</mass>
        <inertia>
          <ixx>9.75e-07</ixx>
          <ixy>0</ixy>
          <ixz>0</ixz>
          <iyy>0.000273104</iyy>
          <iyz>0</iyz>
          <izz>0.000274004</izz>
        </inertia>
      </inertial>
      <collision name='rotor_3_collision'>
        <pose>0 0 0 0 -0 0</pose>
        <geometry>
          <cylinder>
            <length>0.005</length>
            <radius>0.128</radius>
          </cylinder>
        </geometry>
        <surface>
          <contact>
            <ode/>
          </contact>
          <friction>
            <ode/>
          </friction>
        </surface>
      </collision>
      <visual name='rotor_3_visual'>
        <pose>0 0 0 0 -0 0</pose>
        <geometry>
          <mesh>
            <scale>1.5 1.5 1.5</scale>
            <uri>model://sdu_description/meshes/prop_cw.dae</uri>
          </mesh>
        </geometry>
        <material>
          <script>
            <name>Gazebo/Blue</name>
            <uri>file://media/materials/scripts/gazebo.material</uri>
          </script>
        </material>
      </visual>
      <gravity>1</gravity>
      <velocity_decay/>
    </link>
    <joint name='rotor_3_joint' type='revolute'>
      <child>rotor_3</child>
      <parent>base_link</parent>
      <axis>
        <xyz>0 0 1</xyz>
        <limit>
          <lower>-1e+16</lower>
          <upper>1e+16</upper>
        </limit>
        <dynamics>
          <spring_reference>0</spring_reference>
          <spring_stiffness>0</spring_stiffness>
        </dynamics>
        <use_parent_model_frame>1</use_parent_model_frame>
      </axis>
    </joint>


    <!-- Rotor 4 (CCW) -->
    <link name='rotor_4'>
      <pose>0.550429 0.535000 0.120 0 -0 0</pose>
	
      <inertial>
        <pose>0 0 0 0 -0 0</pose>
        <mass>0.05</mass>
        <inertia>
          <ixx>9.75e-07</ixx>
          <ixy>0</ixy>
          <ixz>0</ixz>
          <iyy>0.000273104</iyy>
          <iyz>0</iyz>
          <izz>0.000274004</izz>
        </inertia>
      </inertial>
      <collision name='rotor_4_collision'>
        <pose>0 0 0 0 -0 0</pose>
        <geometry>
          <cylinder>
            <length>0.005</length>
            <radius>0.128</radius>
          </cylinder>
        </geometry>
        <surface>
          <contact>
            <ode/>
          </contact>
          <friction>
            <ode/>
          </friction>
        </surface>
      </collision>
      <visual name='rotor_4_visual'>
        <pose>0 0 0 0 -0 0</pose>
        <geometry>
          <mesh>
            <scale>1.5 1.5 1.5</scale>
            <uri>model://sdu_description/meshes/prop_ccw.dae</uri>
          </mesh>
        </geometry>
        <material>
          <script>
            <name>Gazebo/DarkGrey</name>
            <uri>file://media/materials/scripts/gazebo.material</uri>
          </script>
        </material>
      </visual>
      <gravity>1</gravity>
      <velocity_decay/>
    </link>
    <joint name='rotor_4_joint' type='revolute'>
      <child>rotor_4</child>
      <parent>base_link</parent>
      <axis>
        <xyz>0 0 1</xyz>
        <limit>
          <lower>-1e+16</lower>
          <upper>1e+16</upper>
        </limit>
        <dynamics>
          <spring_reference>0</spring_reference>
          <spring_stiffness>0</spring_stiffness>
        </dynamics>
        <use_parent_model_frame>1</use_parent_model_frame>
      </axis>
    </joint>

    <!-- Rotor 5 (CW) -->
    <link name='rotor_5'>
      <pose>0.520429 -0.435000 0.120 0 -0 0</pose>
      <inertial>
        <pose>0 0 0 0 -0 0</pose>
        <mass>0.05</mass>
        <inertia>
          <ixx>9.75e-07</ixx>
          <ixy>0</ixy>
          <ixz>0</ixz>
          <iyy>0.000273104</iyy>
          <iyz>0</iyz>
          <izz>0.000274004</izz>
        </inertia>
      </inertial>
      <collision name='rotor_5_collision'>
        <pose>0 0 0 0 -0 0</pose>
        <geometry>
          <cylinder>
            <length>0.005</length>
            <radius>0.128</radius>
          </cylinder>
        </geometry>
        <surface>
          <contact>
            <ode/>
          </contact>
          <friction>
            <ode/>
          </friction>
        </surface>
      </collision>
      <visual name='rotor_5_visual'>
        <pose>0 0 0 0 -0 0</pose>
        <geometry>
          <mesh>
            <scale>1.5 1.5 1.5</scale>
            <uri>model://sdu_description/meshes/prop_cw.dae</uri>
          </mesh>
        </geometry>
        <material>
          <script>
            <name>Gazebo/Blue</name>
            <uri>file://media/materials/scripts/gazebo.material</uri>
          </script>
        </material>
      </visual>
      <gravity>1</gravity>
      <velocity_decay/>
    </link>
    <joint name='rotor_5_joint' type='revolute'>
      <child>rotor_5</child>
      <parent>base_link</parent>
      <axis>
        <xyz>0 0 1</xyz>
        <limit>
          <lower>-1e+16</lower>
          <upper>1e+16</upper>
        </limit>
        <dynamics>
          <spring_reference>0</spring_reference>
          <spring_stiffness>0</spring_stiffness>
        </dynamics>
        <use_parent_model_frame>1</use_parent_model_frame>
      </axis>
    </joint>
<!-- Rotor 6 (CCW) -->
    <link name='rotor_6'>
      <pose>-0.350429 -0.405000 0.120 0 -0 0</pose>
      <inertial>
        <pose>0 0 0 0 -0 0</pose>
        <mass>0.05</mass>
        <inertia>
          <ixx>9.75e-07</ixx>
          <ixy>0</ixy>
          <ixz>0</ixz>
          <iyy>0.000273104</iyy>
          <iyz>0</iyz>
          <izz>0.000274004</izz>
        </inertia>
      </inertial>
      <collision name='rotor_6_collision'>
        <pose>0 0 0 0 -0 0</pose>
        <geometry>
          <cylinder>
            <length>0.005</length>
            <radius>0.128</radius>
          </cylinder>
        </geometry>
        <surface>
          <contact>
            <ode/>
          </contact>
          <friction>
            <ode/>
          </friction>
        </surface>
      </collision>
      <visual name='rotor_6_visual'>
        <pose>0 0 0 0 -0 0</pose>
        <geometry>
          <mesh>
            <scale>1.5 1.5 1.5</scale>
            <uri>model://sdu_description/meshes/prop_ccw.dae</uri>
          </mesh>
        </geometry>
        <material>
          <script>
            <name>Gazebo/DarkGrey</name>
            <uri>file://media/materials/scripts/gazebo.material</uri>
          </script>
        </material>
      </visual>
      <gravity>1</gravity>
      <velocity_decay/>
    </link>
    <joint name='rotor_6_joint' type='revolute'>
      <child>rotor_6</child>
      <parent>base_link</parent>
      <axis>
        <xyz>0 0 1</xyz>
        <limit>
          <lower>-1e+16</lower>
          <upper>1e+16</upper>
        </limit>
        <dynamics>
          <spring_reference>0</spring_reference>
          <spring_stiffness>0</spring_stiffness>
        </dynamics>
        <use_parent_model_frame>1</use_parent_model_frame>
      </axis>
    </joint>
<!-- Rotor 7 (CW) -->
    <link name='rotor_7'>
	<pose>-0.40 0.535000 0.120 0 -0 0</pose>
      <inertial>
        <pose>0 0 0 0 -0 0</pose>
        <mass>0.05</mass>
        <inertia>
          <ixx>9.75e-07</ixx>
          <ixy>0</ixy>
          <ixz>0</ixz>
          <iyy>0.000273104</iyy>
          <iyz>0</iyz>
          <izz>0.000274004</izz>
        </inertia>
      </inertial>
      <collision name='rotor_7_collision'>
        <pose>0 0 0 0 -0 0</pose>
        <geometry>
          <cylinder>
            <length>0.005</length>
            <radius>0.128</radius>
          </cylinder>
        </geometry>
        <surface>
          <contact>
             <ode/>
          </contact>
                 <friction>
             <ode/>
                 </friction>
        </surface>
       </collision>
      <visual name='rotor_7_visual'>
      <pose>0 0 0 0 -0 0</pose>
        <geometry>
          <mesh>
            <scale>1.5 1.5 1.5</scale>
            <uri>model://sdu_description/meshes/prop_cw.dae</uri>
          </mesh>
        </geometry>
        <material>
          <script>
            <name>Gazebo/Blue</name>
            <uri>file://media/materials/scripts/gazebo.material</uri>
          </script>
        </material>
      </visual>
      <gravity>1</gravity>
      <velocity_decay/>
    </link>
    <joint name='rotor_7_joint' type='revolute'>
      <child>rotor_7</child>
      <parent>base_link</parent>
      <axis>
        <xyz>0 0 1</xyz>
        <limit>
          <lower>-1e+16</lower>
          <upper>1e+16</upper>
        </limit>
        <dynamics>
          <spring_reference>0</spring_reference>
          <spring_stiffness>0</spring_stiffness>
        </dynamics>
        <use_parent_model_frame>1</use_parent_model_frame>
      </axis>
    </joint>
    <plugin name='rosbag' filename='libgazebo_multirotor_base_plugin.so'>
      <robotNamespace/>
      <linkName>base_link</linkName>
      <rotorVelocitySlowdownSim>10</rotorVelocitySlowdownSim>
    </plugin>
        <plugin name='motor_model_0' filename='libgazebo_motor_model.so'>
          <robotNamespace/>
          <jointName>rotor_0_joint</jointName>
          <linkName>rotor_0</linkName>
          <turningDirection>ccw</turningDirection>
          <timeConstantUp>0.0125</timeConstantUp>
          <timeConstantDown>0.025</timeConstantDown>
          <maxRotVelocity>1100</maxRotVelocity>
          <motorConstant>8.54858e-06</motorConstant>
          <momentConstant>0.06</momentConstant>
          <commandSubTopic>/gazebo/command/motor_speed</commandSubTopic>
          <motorNumber>0</motorNumber>
          <rotorDragCoefficient>0.000806428</rotorDragCoefficient>
          <rollingMomentCoefficient>1e-06</rollingMomentCoefficient>
          <motorSpeedPubTopic>/motor_speed/0</motorSpeedPubTopic>
          <rotorVelocitySlowdownSim>10</rotorVelocitySlowdownSim>
        </plugin>
        <plugin name='motor_model_1' filename='libgazebo_motor_model.so'>
          <robotNamespace/>
          <jointName>rotor_1_joint</jointName>
          <linkName>rotor_1</linkName>
          <turningDirection>cw</turningDirection>
          <timeConstantUp>0.0125</timeConstantUp>
          <timeConstantDown>0.025</timeConstantDown>
          <maxRotVelocity>1100</maxRotVelocity>
          <motorConstant>8.54858e-06</motorConstant>
          <momentConstant>0.06</momentConstant>
          <commandSubTopic>/gazebo/command/motor_speed</commandSubTopic>
          <motorNumber>1</motorNumber>
          <rotorDragCoefficient>0.000806428</rotorDragCoefficient>
          <rollingMomentCoefficient>1e-06</rollingMomentCoefficient>
          <motorSpeedPubTopic>/motor_speed/1</motorSpeedPubTopic>
          <rotorVelocitySlowdownSim>10</rotorVelocitySlowdownSim>
        </plugin>
        <plugin name='motor_model_2' filename='libgazebo_motor_model.so'>
          <robotNamespace/>
          <jointName>rotor_2_joint</jointName>
          <linkName>rotor_2</linkName>
          <turningDirection>ccw</turningDirection>
          <timeConstantUp>0.0125</timeConstantUp>
          <timeConstantDown>0.025</timeConstantDown>
          <maxRotVelocity>1100</maxRotVelocity>
          <motorConstant>8.54858e-06</motorConstant>
          <momentConstant>0.06</momentConstant>
          <commandSubTopic>/gazebo/command/motor_speed</commandSubTopic>
          <motorNumber>2</motorNumber>
          <rotorDragCoefficient>0.000806428</rotorDragCoefficient>
          <rollingMomentCoefficient>1e-06</rollingMomentCoefficient>
          <motorSpeedPubTopic>/motor_speed/2</motorSpeedPubTopic>
          <rotorVelocitySlowdownSim>10</rotorVelocitySlowdownSim>
        </plugin>
        <plugin name='motor_model_3' filename='libgazebo_motor_model.so'>
          <robotNamespace/>
          <jointName>rotor_3_joint</jointName>
          <linkName>rotor_3</linkName>
          <turningDirection>cw</turningDirection>
          <timeConstantUp>0.0125</timeConstantUp>
          <timeConstantDown>0.025</timeConstantDown>
          <maxRotVelocity>1100</maxRotVelocity>
          <motorConstant>8.54858e-06</motorConstant>
          <momentConstant>0.06</momentConstant>
          <commandSubTopic>/gazebo/command/motor_speed</commandSubTopic>
          <motorNumber>3</motorNumber>
          <rotorDragCoefficient>0.000806428</rotorDragCoefficient>
          <rollingMomentCoefficient>1e-06</rollingMomentCoefficient>
          <motorSpeedPubTopic>/motor_speed/3</motorSpeedPubTopic>
          <rotorVelocitySlowdownSim>10</rotorVelocitySlowdownSim>
        </plugin>
        <plugin name='motor_model_4' filename='libgazebo_motor_model.so'>
          <robotNamespace/>
          <jointName>rotor_4_joint</jointName>
          <linkName>rotor_4</linkName>
          <turningDirection>ccw</turningDirection>
          <timeConstantUp>0.0125</timeConstantUp>
          <timeConstantDown>0.025</timeConstantDown>
          <maxRotVelocity>1100</maxRotVelocity>
          <motorConstant>8.54858e-06</motorConstant>
          <momentConstant>0.06</momentConstant>
          <commandSubTopic>/gazebo/command/motor_speed</commandSubTopic>
          <motorNumber>4</motorNumber>
          <rotorDragCoefficient>0.000806428</rotorDragCoefficient>
          <rollingMomentCoefficient>1e-06</rollingMomentCoefficient>
          <motorSpeedPubTopic>/motor_speed/4</motorSpeedPubTopic>
          <rotorVelocitySlowdownSim>10</rotorVelocitySlowdownSim>
        </plugin>
        <plugin name='motor_model_5' filename='libgazebo_motor_model.so'>
          <robotNamespace/>
          <jointName>rotor_5_joint</jointName>
          <linkName>rotor_5</linkName>
          <turningDirection>cw</turningDirection>
          <timeConstantUp>0.0125</timeConstantUp>
          <timeConstantDown>0.025</timeConstantDown>
          <maxRotVelocity>1100</maxRotVelocity>
          <motorConstant>8.54858e-06</motorConstant>
          <momentConstant>0.06</momentConstant>
          <commandSubTopic>/gazebo/command/motor_speed</commandSubTopic>
          <motorNumber>5</motorNumber>
          <rotorDragCoefficient>0.000806428</rotorDragCoefficient>
          <rollingMomentCoefficient>1e-06</rollingMomentCoefficient>
          <motorSpeedPubTopic>/motor_speed/5</motorSpeedPubTopic>
          <rotorVelocitySlowdownSim>10</rotorVelocitySlowdownSim>
        </plugin>
<plugin name='motor_model_6' filename='libgazebo_motor_model.so'>
          <robotNamespace/>
          <jointName>rotor_6_joint</jointName>
          <linkName>rotor_6</linkName>
          <turningDirection>ccw</turningDirection>
          <timeConstantUp>0.0125</timeConstantUp>
          <timeConstantDown>0.025</timeConstantDown>
          <maxRotVelocity>1100</maxRotVelocity>
          <motorConstant>8.54858e-06</motorConstant>
          <momentConstant>0.06</momentConstant>
          <commandSubTopic>/gazebo/command/motor_speed</commandSubTopic>
          <motorNumber>6</motorNumber>
          <rotorDragCoefficient>0.000806428</rotorDragCoefficient>
          <rollingMomentCoefficient>1e-06</rollingMomentCoefficient>
          <motorSpeedPubTopic>/motor_speed/6</motorSpeedPubTopic>
          <rotorVelocitySlowdownSim>10</rotorVelocitySlowdownSim>
        </plugin>
<plugin name='motor_model_7' filename='libgazebo_motor_model.so'>
          <robotNamespace/>
          <jointName>rotor_7_joint</jointName>
          <linkName>rotor_7</linkName>
          <turningDirection>cw</turningDirection>
          <timeConstantUp>0.0125</timeConstantUp>
          <timeConstantDown>0.025</timeConstantDown>
          <maxRotVelocity>1100</maxRotVelocity>
          <motorConstant>8.54858e-06</motorConstant>
          <momentConstant>0.06</momentConstant>
          <commandSubTopic>/gazebo/command/motor_speed</commandSubTopic>
          <motorNumber>7</motorNumber>
          <rotorDragCoefficient>0.000806428</rotorDragCoefficient>
          <rollingMomentCoefficient>1e-06</rollingMomentCoefficient>
          <motorSpeedPubTopic>/motor_speed/7</motorSpeedPubTopic>
          <rotorVelocitySlowdownSim>10</rotorVelocitySlowdownSim>
        </plugin>
    <model name='gps0'>
      <link name='link'>
        <pose>0 0 0.125 0 -0 0</pose>
        <inertial>
          <pose>0 0 0 0 -0 0</pose>
          <mass>0.01</mass>
          <inertia>
            <ixx>2.1733e-06</ixx>
            <ixy>0</ixy>
            <ixz>0</ixz>
            <iyy>2.1733e-06</iyy>
            <iyz>0</iyz>
            <izz>1.8e-07</izz>
          </inertia>
        </inertial>
        <visual name='visual'>
          <geometry>
            <cylinder>
              <radius>0.01</radius>
              <length>0.002</length>
            </cylinder>
          </geometry>
          <material>
            <script>
              <name>Gazebo/Black</name>
              <uri>__default__</uri>
            </script>
          </material>
        </visual>
        <sensor name='gps' type='gps'>
          <pose>0 0 0 0 -0 0</pose>
          <plugin name='gps_plugin' filename='libgazebo_gps_plugin.so'>
            <robotNamespace/>
            <gpsNoise>1</gpsNoise>
            <gpsXYRandomWalk>2.0</gpsXYRandomWalk>
            <gpsZRandomWalk>4.0</gpsZRandomWalk>
            <gpsXYNoiseDensity>0.0002</gpsXYNoiseDensity>
            <gpsZNoiseDensity>0.0004</gpsZNoiseDensity>
            <gpsVXYNoiseDensity>0.2</gpsVXYNoiseDensity>
            <gpsVZNoiseDensity>0.4</gpsVZNoiseDensity>
          </plugin>
        </sensor>
      </link>
    </model>
    <joint name='gps0_joint' type='fixed'>
      <parent>base_link</parent>
      <child>gps0::link</child>
    </joint>
    <plugin name='groundtruth_plugin' filename='libgazebo_groundtruth_plugin.so'>
      <robotNamespace/>
    </plugin>
    <plugin name='magnetometer_plugin' filename='libgazebo_magnetometer_plugin.so'>
      <robotNamespace/>
      <pubRate>20</pubRate>
      <noiseDensity>0.0004</noiseDensity>
      <randomWalk>6.4e-06</randomWalk>
      <biasCorrelationTime>600</biasCorrelationTime>
      <magTopic>/mag</magTopic>
    </plugin>
    <plugin name='barometer_plugin' filename='libgazebo_barometer_plugin.so'>
      <robotNamespace/>
      <pubRate>10</pubRate>
      <baroTopic>/baro</baroTopic>
    </plugin>

    <plugin name='parachute_plugin' filename='libgazebo_parachute_plugin.so'>
      <robotNamespace/>
      <commandSubTopic>/gazebo/command/motor_speed</commandSubTopic>
      <motorNumber>6</motorNumber>
    </plugin>

    <plugin name='mavlink_interface' filename='libgazebo_mavlink_interface.so'>
      <robotNamespace></robotNamespace>
      <imuSubTopic>/imu</imuSubTopic>
      <magSubTopic>/mag</magSubTopic>
      <baroSubTopic>/baro</baroSubTopic>
      <mavlink_addr>INADDR_ANY</mavlink_addr>
      <mavlink_udp_port>14560</mavlink_udp_port>
      <mavlink_tcp_port>4560</mavlink_tcp_port>
      <serialEnabled>false</serialEnabled>
      <serialDevice>/dev/ttyACM0</serialDevice>
      <baudRate>921600</baudRate>
      <qgc_addr>INADDR_ANY</qgc_addr>
      <qgc_udp_port>14550</qgc_udp_port>
      <sdk_addr>INADDR_ANY</sdk_addr>
      <sdk_udp_port>14540</sdk_udp_port>
      <hil_mode>0</hil_mode>
      <hil_state_level>0</hil_state_level>
      <vehicle_is_tailsitter>0</vehicle_is_tailsitter>
      <send_vision_estimation>1</send_vision_estimation>
      <send_odometry>0</send_odometry>
      <enable_lockstep>1</enable_lockstep>
      <use_tcp>1</use_tcp>
      <motorSpeedCommandPubTopic>/gazebo/command/motor_speed</motorSpeedCommandPubTopic>
      <control_channels>
        <channel name="rotor0">
          <input_index>0</input_index>
          <input_offset>0</input_offset>
          <input_scaling>1500</input_scaling>
          <zero_position_disarmed>0</zero_position_disarmed>
          <zero_position_armed>100</zero_position_armed>
          <joint_control_type>velocity</joint_control_type>
          <joint_name>rotor_0_joint</joint_name>
        </channel>
        <channel name="rotor1">
          <input_index>1</input_index>
          <input_offset>0</input_offset>
          <input_scaling>1500</input_scaling>
          <zero_position_disarmed>0</zero_position_disarmed>
          <zero_position_armed>100</zero_position_armed>
          <joint_control_type>velocity</joint_control_type>
          <joint_name>rotor_1_joint</joint_name>
        </channel>
        <channel name="rotor2">
          <input_index>2</input_index>
          <input_offset>0</input_offset>
          <input_scaling>1500</input_scaling>
          <zero_position_disarmed>0</zero_position_disarmed>
          <zero_position_armed>100</zero_position_armed>
          <joint_control_type>velocity</joint_control_type>
          <joint_name>rotor_2_joint</joint_name>
        </channel>
        <channel name="rotor3">
          <input_index>3</input_index>
          <input_offset>0</input_offset>
          <input_scaling>1500</input_scaling>
          <zero_position_disarmed>0</zero_position_disarmed>
          <zero_position_armed>100</zero_position_armed>
          <joint_control_type>velocity</joint_control_type>
          <joint_name>rotor_3_joint</joint_name>
        </channel>
        <channel name="rotor4">
          <input_index>4</input_index>
          <input_offset>0</input_offset>
          <input_scaling>1500</input_scaling>
          <zero_position_disarmed>0</zero_position_disarmed>
          <zero_position_armed>100</zero_position_armed>
          <joint_control_type>velocity</joint_control_type>
          <joint_name>rotor_4_joint</joint_name>
        </channel>
        <channel name="rotor5">
          <input_index>5</input_index>
          <input_offset>0</input_offset>
          <input_scaling>1500</input_scaling>
          <zero_position_disarmed>0</zero_position_disarmed>
          <zero_position_armed>100</zero_position_armed>
          <joint_control_type>velocity</joint_control_type>
          <joint_name>rotor_5_joint</joint_name>
        </channel>
	<channel name="rotor6">
          <input_index>6</input_index>
          <input_offset>0</input_offset>
          <input_scaling>1500</input_scaling>
          <zero_position_disarmed>0</zero_position_disarmed>
          <zero_position_armed>100</zero_position_armed>
          <joint_control_type>velocity</joint_control_type>
          <joint_name>rotor_6_joint</joint_name>
        </channel>
	<channel name="rotor7">
          <input_index>7</input_index>
          <input_offset>0</input_offset>
          <input_scaling>1500</input_scaling>
          <zero_position_disarmed>0</zero_position_disarmed>
          <zero_position_armed>100</zero_position_armed>
          <joint_control_type>velocity</joint_control_type>
          <joint_name>rotor_7_joint</joint_name>
        </channel>
        <channel name='aux1'>
          <input_index>8</input_index>
          <input_offset>0</input_offset>
          <input_scaling>1000</input_scaling>
          <zero_position_disarmed>0</zero_position_disarmed>
          <zero_position_armed>100</zero_position_armed>
          <joint_control_type>velocity</joint_control_type>
        </channel>
      </control_channels>
    </plugin>
    <static>0</static>
    <plugin name='gazebo_imu_plugin' filename='libgazebo_imu_plugin.so'>
      <robotNamespace></robotNamespace>
      <linkName>/imu_link</linkName>
      <imuTopic>/imu</imuTopic>
      <gyroscopeNoiseDensity>0.0003394</gyroscopeNoiseDensity>
      <gyroscopeRandomWalk>3.8785e-05</gyroscopeRandomWalk>
      <gyroscopeBiasCorrelationTime>1000.0</gyroscopeBiasCorrelationTime>
      <gyroscopeTurnOnBiasSigma>0.0087</gyroscopeTurnOnBiasSigma>
      <accelerometerNoiseDensity>0.004</accelerometerNoiseDensity>
      <accelerometerRandomWalk>0.006</accelerometerRandomWalk>
      <accelerometerBiasCorrelationTime>300.0</accelerometerBiasCorrelationTime>
      <accelerometerTurnOnBiasSigma>0.196</accelerometerTurnOnBiasSigma>
    </plugin>

</model>
</sdf>

Managed to solve it simply by moving the propellers further away from the center. The reason for this is that the geometry file says the propellers is located 0.7 meters away from the center, so moving the that far out made it fly.