Denavit-Hartenberg Reference Frame Layout

This video demonstrates use of the Denavit-Hartenberg convention for defining the reference frames of a kinematic chain.

In short, the z-axis for each joint is placed along its axis of motion, and then the x-axes are placed along the common normals between these z-axes. Then four parameters are used to specify the transformation between each of these frames:
• d - the "depth" along the previous joint's z axis
• θ (theta) - the rotation about the previous z (the angle between the common normal and the previous x axis)
• r - the radius of the new origin about the previous z (the length of the common normal)
• α (alpha) - the rotation about the new x axis (the common normal) to align the old z to the new z.

See also the Tekkotsu kinematics page, with numerical examples, tools, and links to download HD. http://www.tekkotsu.org/Kinematics.html

Category:

Science & Technology

Tags:

• dh parameters
• d-h
• denavit-hartenberg
• reference
• frame
• layout
• kinematics

[richardcc29]

Is X1=Z0 cross Z1 or X1=Z1 cross Z0?

Are both directions ok?

[TekkotsuRobotics]

Both directions are OK, as long as you flip the sign on the associated 'r' parameter: a × b = -( b × a )

In other words, you have two choices for the direction of each x vector: one results in a positive r, the other results in a negative r. (If z₀ and z₁ intersect, then r₁ is 0 so this is arbitrary)

Neither choice of (z₀ × z₁) vs. (z₁ × z₀) will yield positive r₁ for all configurations, so if you want to enforce a positive r you have to check and flip signs as needed.

[fuqaha8]

i have robotic test tomorrow.. =))

[mehdital]

@bassefa1984 Ours talked about it for 30 minutes...

[bassefa1984]

This took my professor 2.5 hrs to explain on the board and I still didn't get it.

Thnx for the vid :)

[mwmartin06]

thanks man, really appreciate this video

[mavenuparker]

Awesome......I understood DH Notation :)

[cKlutcHJ21]

Thank you! This is totally helping me out right now!

[rajkbehra]

3 days atleast u had saved my important 3 days ,which could have been utilised to understand this topic

[rajkbehra]

3 days atleast u had saved my important 3 days ,which could have been utilised to understand this topic

[Mhkais]

"that's all there is to it"

It has melted my mind all day...

[barbarossamotitoooo]

yes now i understand