Quadrotor model

Discussion in 'Modeling' started by Artem, Jan 10, 2018.

  1. Hi everyone,

    what would be the best way to create a model of a quadrotor in MuJoCo?
    The main question is probably how to create actuators simulating thrusters?
    Could you provide an example?

    Thanks a lot!
    Last edited: Jan 11, 2018
  2. Emo Todorov

    Emo Todorov Administrator Staff Member

    Are we talking about a spinning propeller, or a rocket-style thruster?

    For a thruster, you can attach a motor to a free joint, and specify the 6D gear parameters so that the motor applies force along the desired axis.

    If you want a spinning propeller, you need to use the lift-drag force simulation in MuJoCo. Attached is an XML illustrating this.

    Attached Files:

  3. Thanks a lot for the help.

    I first tried to make a simple thruster model.
    I am creating a site at the location of the thruster and then I am specifying the site for the actuator (motor type).
    As a gear parameter, I set gear='0 0 100 0 0 0' to see the effect of forces only. If I understand the first 3 components will be responsible for scaling the force, and the next 3 the torque. Is that correct?
    The documentation also says that the force will be generated in the site's frame ( http://mujoco.org/book/modeling.html#general ).
    But a simple simulation with generating a force at a single thruster does not seem to produce an adequate behavior since a force on a single thruster should have just flipped the quadrotor.
    Thus, I am wondering if I did it correctly?
    I also have another question:
    - what is the simplest way to simulate opposite direction torques along the yaw (z) axis generated by thrusters.

    I am attaching the xml file I have created and recording of the experiment I see.
    Looking forward to your response!

    Attached Files: