Unit 2, 2.1.5 Composition of rotations

Course Support Basic Arm Kinematics
1

Hello!
can someone xplain these two points?

  1. If we post-multiply, the Z rotation is intrinsic, it is applied to the current coordinate frame (the can rotates about the axis of the cylinder).
  2. If we pre -multiply, the Z rotation is extrinsic , and it is applied to the fixed coordinate frame (the z-axis normal to the planar grid).
    Thanks
2

Hi,

EXtrinsic = The reference frame we use for the rotations of that SolidObject is the WORLD frame
Intrinsic = The reference frame we use for the rotations is a certain reference frame that is NOT the WORLD frame

EXample:

  • In these images you can see two frames: The World frame, and the Neck_frame.

If we rotate around the X axis o the World frame ( EXtrinsic) it turns like in the second image.

If we turn around the Nack frame ( Intrinsic) we turn as in the third image.

rotglob_iddle
rotglob_iddle1920×1080 25.5 KB

rotglobx
rotglobx1920×1080 32.2 KB

rotglob_x_rel
rotglob_x_rel1920×1080 25.6 KB

3

So Extrinsic means global frame and Intrinsic is like local frame. Thanks for explaining through images…:slight_smile:

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