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Chapter 02

Basics of Animation and Forward Kinematics

Page 12

Forward Kinematics: Two Link Mechanism

The mathematical drill previously done, is good for a single link mechanism only. For two link mechanism, like the robot arm, a few more considerations are required.
Consider the following example in which a 5-sided polygon is rotated for θ°



In order to rotate a polygon all the 5-points are equally rotated. If not then the shape will be deformed.

Now, instead of the polygon, imagine a 4-link mechanism. The link names are L1, L2, L3 and L4. If Link-1 is rotated then all other links after it are to be rotated:

RULE:

To rotate a multi-link mechanism (graphically) along any joint, rotate all the vertices following it (with the same angle and same direction)

This can be observed from the gif-animations shown below:

To rotate L1 : Rotate Vertice_of_Joint_2, Vertice_of_Joint_3, Vertice_of_Joint_4 and Vertice_of_gripper w.r.t Vertice_of_Joint_1






To rotate L2 : Rotate Vertice_of_Joint_3, Vertice_of_Joint_4 and Vertice_of_gripper w.r.t Vertice_of_Joint_2





To rotate L3 : Rotate Vertice_of_Joint_4 and Vertice_of_gripper w.r.t Vertice_of_Joint_3






To rotate L4 : Rotate Vertice_of_gripper only w.r.t Vertice_of_Joint_4

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