Auburn University Aerospace Engineering Samuel Ginn College of Engineering
 
 

Generalized Rotational Mechanics

 

The motion of general mechanical systems can be related to the rotational motion of rigid bodies.  One approach to doing this is to equate the generalized coordinates of a system with the Rodrigues parameters of an equivalent rotational motion.  Here are some movies that demonstrate this for two different systems: a planar body and a three-link robotic manipulator.  In each, the motion of the system is shown along with the equivalent rotational motion of a rigid body (the "beachball").

 

PlanarMotion.avi - This movie shows the three cardinal motions of a planar body.

 

PlanarMotion2.avi - This is a case of more general motion.

 

NomMotionFF.avi - Rotation in each joint of a three-link robot is demonstrated.

 

RegMotion.avi - The motion of the robot is now controlled using a spacecraft-attitude control law.

(Note: These movies were created using the Indeo codec.  To play in Windows Media Player they need to be saved to your hard drive.)

 

The last movie demonstrates a main application of this approach to system dynamics.  It allows the work done in spacecraft-attitude control to be leveraged to any 3-DOF system.  The concept can also be extended to systems with more than three degrees of freedom by considering rotations in higher dimensions, but it gets tough to visualize!