How to make two planes perpendicular in Simscape Multibody?

Hello everybody,

Currently I am trying to simulate the behaviour of a rear vehicle suspension system (semi-rigid axle). Because I am only simulating a single axle, the whole assembly cannot stay straight on its own, so I need to somehow restrict it so it does not fall, without restricting the important degrees of freedom. I have an idea how to do it, but I do not know whether or not Simscape has the functionality. In the 3D photo, you can see a highlighted (bright-blue) plane. My idea is to make this plane perpendicular to the ground, so that the body of the car always stays straight, but it can still row and make turns. Is there a way for me to achieve this?

Answer 1

[Steve Miller]

Hi Nikola,

I think you are trying to constrain the body of the vehicle so that it can roll (rotate about its longitudinal axis, the one in the direction of travel) steer (rotate about the axis normal to the ground plane), translate along x, y, and z, but not pitch (not freely rotate about the axis parallel with its axle.

There are a few ways to do this, but I think I would connect the center of the plane highlighted in your screenshot to ground using a 6-DOF joint. I would put a spring on the Z-Prismatic and the Y-axis of the spherical joint. The spring force will help keep the vehicle from tipping over because only half of the vehicle is there.

You could accomplish something similar using (Cartesian Joint + Unversal Joint) connected in series, with a spring on the Z-Prismatic of the Cartesian Joint. In this case, no pitch would be permitted.

--Steve