Modeling Vehicle Dynamics – 6DOF Nonlinear Simulation

Here we take all the equations of motion we have derived and numerically integrate them to generate a simulation of the vehicle motion and dynamics.

 

This post is the 3rd in a series on modeling and simulation of a quadcopter’s vehicle dynamics. The previous posts can be found here:

  1. Modeling Vehicle Dynamics – Euler Angles
  2. Modeling Vehicle Dynamics – Quadcopter Equations of Motion
  3. Modeling Vehicle Dynamics – 6DOF Nonlinear Simulation

Programming a Simulation

I have created the simulation in a Jupyter notebook which uses Python code. You can download a copy of the notebook to make changes and try running it from my GitHub here:

Link to iPython Notebook

 

Example Control Inputs:

In order for the simulation to show something interesting without any control laws in place, I have hard coded in a small set of propeller commands:

  • For time = 0.0 – 10.0 seconds:  Apply positive climb acceleration
  • For time = 8.0 – 9.0 seconds:  Apply forward pitch rate
  • For time = 9.0 – 10.0 seconds:  Remove forward pitch rate
  • For time = 12.0 – 13.0 seconds:  Apply negative pitch rate
  • For time = 13.0 – 14.0 seconds:  Remove negative pitch rate
  • For time = 16.0 and after: Apply slight positive climb acceleration

After the simulation runs you can see the plots at the bottom of the notebook that show the effect these control inputs produce.

 

Visualization

Below is a javascript visualization of the trajectory plotted in the above Jupyter Notebook.

Use left click to rotate, middle click to zoom, and right click to pan (when camera is not locked)

One thought on “Modeling Vehicle Dynamics – 6DOF Nonlinear Simulation

  1. Hi there,
    I was just wondering what would be the expression that would be used to calculate Torque. I mean the the below code returns a value of zero isn’t it?

    def T(F,dx,dy):
    # Returns torque about cg given thrust force and dx,dy distance from cg

    #### PLACEHOLDER ####
    return 0

    I have been going through various sources to finalize on the expression. There are sources which gives expressions such as Torque = Cq * Omega^2 , where Cq is the torque coefficient and Omega the RPM (http://www.cs.cmu.edu/afs/cs.cmu.edu/academic/class/16311/www/s15/syllabus/ppp/Lec08-Control3.pdf) . I am bit confused there as the expression doesn’t contian information regards to the distance from CoM.

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