Spiral motion simulation in Simulink

Using Simulink and the 6DOF (Euler angle) block feeding into the 6DOF animation block I am trying to create a spiral that ascends or descends. I tried using the repeating sequence stair block to input values for pitch (simulate steady ascent or descent) and yaw (simulate a steady inward spiral). Upon trying different vector configurations, I have found that my model always tends to increase the inward spiral as if the yaw moment is accelerating or something similar to this, at the point where I am lost for ideas how to make this work. My question is, how could I simulate a steady spiral? I am not sure if my problem comes from a constant velocity issue or if it is as I mention above with an accelerating yaw moment.

I have screenshot my simulink model and the animation output as well as my code from matlab that gives vector inputs to my thrust and moment inputs in simulink.

Many thanks to any that help!

Answer 1

[Jianxin Sun]

Hi Josh,

To generate a circular motion, you can try the following:

1. In the initial state of 6 DOF block, set it so that it has initial tangential speed.
2. Based on the speed and desired radius, you'll need to apply a force vector on the body that points towards the center of your circle, which might look like Fx = mV^2/r*sin(theta), Fy = mV^2/r*cos(theta), where theta = V/r*t + theta0.