Denavit-Hartenberg Reference Frame Layout

[@Cold_Ham_on_Rye]

This type of stuff has to be learned visually. I had no idea what my textbook was saying.

[@longbeachboy57]

Same here :)

[@asharatiq4941]

Cold Ham on Rye this just saved my exam!

[@williamchamberlain2263]

You're right. But this also has a good sequence of words, and a good sequence of steps which introduce the variables one at a time. I think that textbooks try to cram it into too short a space: it looks like at least 2 pages of A4 at 11pt Arial to me, with an illustration for each point which highlights the measurements and variable being introduced.

[@muhammadzafarullahkhalid5129]

True

[@jaystonn]

I couldnt keep looking at it as a triangle 😭😭

[@hardeep1331]

it's amazing how a 3 minute video can teach you more than reading a whole chapter

[@sorrefly]

3 minutes explained more of 6 hours of class

[@jean-pauldus5241]

Wonderful video. I recommend it to every person that needs to understand the Denavit-Hartenberg convention. If you could do other videos like that please do it! It really helps. Thank you.

[@MrNormanhughes1]

Wow, this just taught me how D-H works better than a 4th year undergraduate course could. THANKS!!!

[@dez7800]

sameeeeee ! 7 years later lol

[@UPBCFernando]

It´s 2020 and your video still rocks, i show this to my robotics class every time i need to explain DH parameters, thanks!!

[@rohanrana4626]

finally a prof who knows the value of this video and possibly his and his students' time.

[@green8026]

The utility/information to time ratio on this video is one of the highest I've ever seen. It's even higher than Master Yoda's.

[@rajivkrishnatr]

You made it seem very simple! Better than the textbooks!

[@tundeojutiku4281]

Wonderful! Full semester course explained in 3 minute. Thank you Sir.

[@sahilrupani3043]

You saved my grace... like literally bro... I would have damn near flunked my paper cause i simply couldn't visualise it... Whoever you are you rock... P.S. I wouldn't be surprised if it was Denavit himself who realised he needed to make a video to explain himself...

[@vitalram1985]

Best explanation on DH parameters ever find.

[@threshaxe]

This made DH transforms click. People like you are the saving grace for visual learners like me.

[@zihanqiao2850]

Perfect video for learners to understand the meaning of the four parameters!

[@boiledham]

Thank you so much for this video. I want you to know that it's still being used in college lectures because it's far more intuitive to see the D-H convention in 3-D rather than a page of a textbook.

[@williamchamberlain2263]

BoiledHam I found it via 15-494 Cognitive Robotics David S. Touretzky & _Ethan Tira-Thompson_ Carnegie Mellon Spring 2012 :)

[@fernando4959]

Even wikipedia is referring this video, in the article (not reference / footnote)

[@saud9270]

the best explanation ever. these 3 mins where better than the 3 hour lecture I had

[@AnandVL]

Denavit-Hartenberg would be proud! This video saved me. Brilliant explanation. Thanks loads

[@Potato_soldier]

The best DH-conversation guide I seen ever!

[@PEJOTAvix]

Great vid. Awesome to understand the variables of Denavit-Hartenberg. Indicated by my teacher in a robotics introdutory class.

[@Mobin92]

Why is the X-Axis at 1:00 pointing in that direction? I would have expected it to be the inverse of that.

[@AndreasAn]

Thanks a lot. This short animation and explanation was more worth than 2 hours of reseraching the internet for texts and imgages.

[@Manish-ue9xw]

this clip deserve more views , textbooks should provide such links for better understanding.

[@NadiaAkbar-z5t]

Found this video on wikipedia and it's very helpful, thank you

[@npuldon]

Best video ever on DH parameters!

[@kenzalazrak790]

please keep making videos like this, you just have saved my life ! thanks !

[@ahmedayman8369]

Thanks a lot man. Saved me a lot of time. Way better than seeing them on a 2D slide.

[@alirizvi6375]

The visualization is very helpful in understanding the DH frame assignment. Thank you so much.

[@ashishlakr]

THIS HELPED ME A LOT FOR MY EXAMS PURPOSE

[@justeeSh]

+ve angle(theta and alpha) is obtained by conterclockwise rotation and +ve length( r and a) are obtained by moving from previous x-axis to new origion

[@lpedrosoacademic]

This video has made everything so clear to me!

[@mustafahasria5362]

It's more than a fantastic video it's a lot to learn in 3 minute

[@alexhamilton-jones1884]

Brilliantly simple, well explained and nice animation - thanks!

[@bcavalcante]

I wish you were my robotics teacher! Thanks for your explanation!!!

[@kemi242]

Thanks. I'm studying for an exam, and this helped make it clear.

[@yvonnemakori9869]

Wow...Am impressed...So simple and easy to understand

[@ramonperez5506]

You made this look so simple. Thanks!!! Good job with the graphics too.

[@jiglesiasabio]

DH + Fireworks = AWESOME! great video!

[@alfredomaussa]

but, this is a denavit hartenberg modified, it is different from the original denavit hartenberg. no mentioning that is confusing when you look other examples.

[@rajkbehra]

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

[@tanyagupta3034]

Thanks for the video man! Awesome explanation and animation!

[@TheDIYer]

Someone give him a medal/oscar, thanks very much

[@peacemaker3913]

The sprinkels in the end *.*

[@TheLeontheking]

The explanation was quite good, but what really made it was the celebrating robot at the end ;)

[@Infaviored]

Thanks so much. I understand the concept now, but i think my book uses another convention (or i am just extremely confused). Mine is using the convention from Craig(1989) The bodys are called B_i-1 and B_i. axis z_i-1 and z_i are pointing along the axis of Rotation/Translation of the Joints. x_i-1 is pointing along the smallest distance between z_i-1 and z_i . Where z_i-1 and x_i-1 meet is the origin of body i-1. a_i-1 is the translation distance of the origin along the axis x_i-1. alpha_i-1 is the angle between axis z_i-1 and z_i along x_i-1. the translation distance of the origin along axis z_i is called d_i. The rotation between axis x_i-1 and x_i is called theta_i. I think both concepts describe the same thing, but i cant get my head around on how to describe a system with my convention. Say i want to write a code that generates a joint structure by the DH parameters. Starting from body 0, how can i know in which direction to lay x_0 if i do not yet know where the next joint is located?

[@vargalaszlo1989]

Better late than never: your book uses the 'modified DH' parameters, but many times the author just don't mention it. I recommend Peter Corke's books.

[@KiranParmar88]

Thank you for making this simple as possible!

[@namensklauer]

what about the r=0 case? if that 45° angle (where the second joint is connected) wasnt there, so that the second Z axis would go right through the first one, then the new X axis should be aligned with the old Y axis, right? a "minimal rotation around the old Z axis" would leave +90° and -90° as solutions, so postive wins?

[@avinashsingh8458]

This is really helpful in those online classes.

[@josu88]

wow.. tons of love for you brother, u save my life

[@nataliaortizb]

Thanks a lot to upload this video, I finally understand how to put the frames

[@mostafametwally]

Thank you !! I am studying at RWTH and this video was really helpful :D

[@RaniLink]

I'm always baffled by how a 3 minute video can explain what my incompetent professor couldn't in a 3 hour lecture

[@REL1C]

The confetti at the end makes the video.

[@MrGuitarMix]

When the teacher dances like 2 hours in front of the class to explain the DH convention.

[@rbaleksandar]

I have a question to ask. Let's say we have two rotational joints and the rotation axis of the second is perpendicular to the the rotation axis of the first. The common normal in this case is the same as the rotation axis of the second joint. In this case how can we determine the frame (x,y,z) of the second joint using the DH-convention?

[@BlackShadows2424]

This is what my whole last lecture should've been boiled down too.

[@davidgmos]

thanks for taking your time to share this

[@rbaleksandar]

Found the answer. :P In this case we simply take x(i) to be parallel to x(i-1) that is x(i) is a normal to the plane of z(i) and z(i-1).

[@ingofrank3556]

I might be wrong on this but i think there is a mistake with the animation at the end: the x and y axis of the first element should not move while turning but stand still. the following joints coordinate systems should move with respect to the coordinate systems prior to them. the first joint and coordinate system is attached to the base frame should not move with respect to the base frame. At least that's how we learned from my professor. I still love this Video though, thanks for sharing!

[@aaronsnoswell]

In traditional DH Convention, the X axis, not the Z axis, is on the axis of rotation.

[@williamchamberlain2263]

aaronsnoswell welcome to the pain of coordinate system conventions! Image processing usually use xyz=right-down-forward for local and have no global, ground& manipulator robots use xyz=forward-left-up for local and east-north-up for global, drones/UAVs/aeronautics/ships/subs use xyz=foward-right-down for local and north-east-down for global

[@henokdaniel6358]

wow....this helps tremendously man. thank you

[@punstress]

Great video. I need to simulate a robot in Gazebo standalone and can't figure how to incorporate DH tables. I'm new to robotics, Gazebo, simulation, yeah so it's not going well. Can't find any documentation. Stressing out!

[@roorkeeable]

Hi, how did you create this video? What kind of software did you use? thank you

[@ejtttje]

Blender www.blender.org

[@TiborBotos]

Thanks, that's an awesome visual explanation!

[@bestmessi87]

When the z axes are perpendicular the common normal is the point where intersect. In this case I can choose x arbitrarily?

[@eduardoramada5164]

Hi. Do you authorize the download and use it in a educational simulator as support material for students?

[@PavanKalyanKota]

I'm having a confusion in drawing the Joint Co-ordinate system for a 7DOF manipulator. All are revolute joints. Shoulder Roll (Spin) Shoulder Pitch (Articulate) Elbow Roll (Spin) Elbow Pitch (Articulate) Wrist Yaw (Articulate) Wrist Pitch (Articulate) Wrist Roll (Spin) Please help me out in drawing this one. Thank you.

[@ayushagarwal69]

omg , so well explained , thanks a lot :)

[@willemjvo1967]

Great video! Concise and correct!

[@fritzchennummber1]

Thanks a lot from Germany!

[@ClearNinjaFox]

can someone explain how does one starts to note the dof of a human in degrees or radiance ? i mean i kno obv what is our dof but how would we go about writing it in programming terms?

[@shenyan9062]

Thx. You made my life easy.

[@malcomx2012]

it is really very amazing video and very helpful and thank u for uploading this

[@chaluvadi]

Hi, I have a doubt. 1. Theta is the angle about the previous z axis . So by right hand thumb rule you have to rotate the x-axis in anti-clock wise direction but in the video its clock-wise. And its the same with alfa. 2. At joint one Z-axis is pointing outwards. Is it OK to consider z-axis pointing inwards since link 1 can rotate clock wise and anti-clockwise.

[@msschubi]

+bhanu kiran chaluvadi Yeah, i think that you are right :)

[@venkat28061991]

+bhanu kiran chaluvadi To clarify your doubt, 1. In the video, Theta and Alpha are denoted as variables. So it does not matter in which way you measure while representing Theta and Alpha. However, the values taken by these variables must be as per Right hand thumb rule. For example if X-Axes are displaced by 45 degree in clockwise direction w.r.t Z-Axis, then the value of Theta will be -45 degree and can be denoted in the same way as shown in the video 2. You can choose in any way as you like, since it only acts as a reference for calculating the angles. Also you have to note that any given position of the end effector has two solutions. One with Theta and other with Theta+180 degree (assuming you have taken Z-Axis pointing outwards and it is revolute joint) So if you take the Z-Axis pointing inwards, your solution will be either Theta+180 degree or Theta.

[@ejtttje]

1. You can have negative rotations :) But you are correct to use the right hand rule to know which direction is positive. 2. I'm not sure what you mean by "in" or "out". The general idea is that the Z-axis should point in the direction of positive rotation for the corresponding joint. Otherwise your physical joints won't match what the math expects them to do.

[@sission4630]

What software was used for this video?

[@nadezhdadimitrova4042]

Really useful video. Just a quick remark though: I think it would be better if the text in the video was not different than the speech. A bit confusing,

[@asharatiq4941]

Superb explanation!

[@BrianKCatlin]

What software was used to create this video?

[@quannarula7046]

great video! thanks for sharing!

[@RoshanAkaravitage]

Thank You very much ! this is really helpful.

[@beaubryant4534]

Why can't i hit the like button more than once.

[@khoerulanwar3318]

nice I like it, very informative than a book i think

[@divixth]

Dangg!!! This is all I want Thanks Dude :D

[@tarekwisdom664]

Amazing explanation .... thank you

[@chokkakulahemanth9631]

Good......nice animation Betterful to students........

[@maliakbulut]

What happens when two z axes(z, z+1) intersect each other.

[@davidgwestern]

r = 0

[@穆翔]

This is for the standard DH or the modified DH?

[@quentinl6256]

really helpful. thanks for a great vid

[@muditmittalyou]

Really awesome......Great animation!!!

[@nadezhdadimitrova4042]

Thanks! What happens to the x-axis in the parallel case?

[@ayushagarwal69]

still along the common normal , same case as before

[@JadeOhara]

This is amazing!

[@66hades]

What software did you use to simulate this animation?

[@ejtttje]

Blender www.blender.org

[@Alexr044]

Amazing video, can't thank you enough!

[@dellefranz]

It’s still difficult. But this makes it easier.

[@richardcc29]

Is X1=Z0 cross Z1 or X1=Z1 cross Z0? Are both directions ok?

[@aayushverma4408]

How do you decide the sign of r,d and alpha??

[@tholfikarn]

the best video ever

[@joels9848]

The auto-captioning is top-notch...

[@mwmartin06]

thanks man, really appreciate this video

[@hamoudamezghani1756]

thanks , this helps me a lot :) you are just grate ;)

[@wanderfra42]

This video is a-w-e-s-o-m-e!

[@palashrathore6277]

Nailed it bro!!