New Dynamixel Servos (XM430 Series): Updated Mechanical Design and a Constant Torque Mode

Robotis Dynamixel XM Series of Servos

It's no secret that I'm a huge fan of Robotis' Dynamixel servos.  I've written about them in the past (here and here), developed open source Python libraries to control them, and used them extensively in my past research.  The new XM Series of Dynamixel servos are a pretty big change for Robotis... the new mechanical design has a lot of benefits: better mounting options (direct-to-case rather than the weird nut insert), more visually appealing, and the ability to route the cable directly through the backside load bearing. But they also offer a lot of improved performance -- comparing the old MX-28AR to the new XM430-W350, we get 65% higher torque for 5% lower price (I'm told the MSRP will be ~$240). Plus a whole bunch of new operating modes, including a few that directly control current (and torque by proxy): Torque Control Mode (perfect for robot grippers!), Current-and-Position Control, and even raw PWM.  Read on for details, including a new open-source Python library to control the XM Series using Robotis' v2 Communication protocol.

If you want exact technical specifications, hop over to Robotis' XM430 Series e-Manual. (Quick aside: I love the transition away from PDFs!).  The most pronounced thing is the new design that ditches those funky inset nuts in favor of mounting holes directly on the servo body.  Also of note: The new backside load bearing supports through-hole cable routing (yay for cleaning up the wiring!).  The front of the servos remains relatively unchanged in terms of the servo horn itself.

New Robotis Dynamixel XM Series

New Robotis Dynamixel XM Series

New Robotis Dynamixel XM Series New Robotis Dynamixel XM Series New Robotis Dynamixel XM Series

New Robotis Dynamixel XM Series


I've heard that these new servos will retail for $240 (so about the same price as a comparable MX-Series servo)... but they have much better torque and standby-current ratings.


From a controls perspective, the most compelling news for these new servos is new Torque Control Mode.  There's a RobotisChannel Youtube video that shows off the new capability:


Robotis lent me a few developer test units to play around with and gave me permission to write about them. I wish I had time to play around extensively with the new servos... but alas, my new robotics startup is keeping me insanely busy.  [I know what you're thinking: "You have a new robotics startup?! Wat?"  Yep. But we're still a bit stealthy at the moment, so stay tuned; we'll announce it eventually.]

But I did take a bit of time to devise a new control library (similar to the old library), which supports the new XM servos and the Robotis v2.0 communication protocol. You can find the new source here:  Please note that it's not fully backwards compatible with the old library -- in fact, it's missing quite a lot.  Some day, maybe I'll go back and make a unified Python library for all Robotis servos.... but in the meantime, here's a very simple usage example (fully tested!):

dyn = USB2Dynamixel_Device( '/dev/ttyUSB0' )
p = Robotis_Servo2( dyn, 1, series = "XM" )
p.set_torque( 100 )  # 2.69mA/unit * 100 => 269mA current => 0.3 Nm according to torque curve


I can't stop 0.3 Nm on the servo horn directly with my hand... but if you back it down to 20 instead of 100 (off the torque-current curves), then I was able to stall the rotation while the motor provided constant opposing torque. Pretty cool -- this should prove really handy for building things like robot grippers!



Hey, thank you so much for this post. Even now that the XM series are available for purchase, your article is the only one I've found for more info on these new motors. Great post.

I can quite make out how the wiring goes into the shaft and connects, can you provide more pictures or a video of that? And have you found any cons about these new motors?


I know how it's an awesome game so I real want to Play it haha :) :)

tank trouble   bejeweled

—SusanM Gardner

Much informative article, and I really appreciate this info and willing for moreinteresting article like this. happy wheels demo

—happy wheels

Really impressive post. I read it whole and going to share it with my social circles. I enjoyed your article and planning to rewrite it on my own blog.  


This is such a great resource that me are providing and you give it away for free. seeing that understand the value of providing a quality resource for free bloons tower defense 5    super smash flash 2

—MarkC Phillips

Thanks for sharing this great. Keep sharing more useful and conspicuous stuff like this. Thank you so much geometry dash


This is an interesting site, serious!Really these contents needs to be shared on social networking sites as they are really the brief and great masterpieces here happy wheels


I really loved reading your blog. It was very well authored and easy to undertand. Unlike additional blogs I have read which are really not tht good. I also found your posts very interesting. In fact after reading, I had to go show it to my friend and he ejoyed it as well! five nights at freddy's


The one place where as a venue and fan I could search by what ever perimeters I chose .Good Luck with your future endeavors happy wheels demo


Thanks for the sharing this great article related to The Future of the Web.. this article is very usefull for me…..thanks again for sharing this great article! flip diving


Thank you for another essential article. I have learned a lot from your article. Thank so much, again!  hotmail login


good post guys and thanks for your article this is simply awesome. thanks for your info.   spotify premium apk


This is also a very good post which i really enjoyed reading. It is not everyday that i have the possibility to see something. Shilpa

Get free online money making guide click here this is our stance and further information gta v money cheat on gta online cheats as for a gta 5 money cheat,here more info on that.

—gta 5 online generator

Thanks for the sharing this great article related to The Future of the Web.. this article is very usefull for me…..thanks again for sharing this great article lowongan


This post is very amazing for me.I read this post and share this with my all family member. Thanks for this nice post keep it up.  

It's a great posting, thanks for this share..

Umroh Ramadhan I Haji Plus 2017

Thank you for sharing! Can you sharing some updates on how you have made this powerful post!

geometry dash | facebook sign up | bloons tower defense 5

I just want to say thanks for your wonderful post, it is contain a lot of knowledge and information that i needed right now. You really help me out my friend, thanks !  hill climb racing 2

—hill climb racing 2

The article you have shared here very good. This is really interesting information for me. Thanks for sharing!

- google mail

Hello! I'm a Rom, I would like to challenge the whole world with the kind of games follows: First, <a href="" title="Super Smash Flash"><b>Super Smash Flash</b></a> is a series of non-profit, fighting, crossover, fan-made Flash games published by indie website McLeodGaming. It is based on the Super Smash Bros. series.   Second, You’ll have to be very ingenious to pass the levels in the game. At a high level, you will face many difficulties.  <a href="" title="Rolling Sky 2 Online"><b>Rolling Sky 2 Online</b></a> has 14 levels for you to conquer, if you pass level 14, you really are a top player.   And finally, Drag the ball left or right and avoid all obstacles. Do not deviate from track! Come on! Relentless pursuit of super speed. You can be faster along with the music rhythm!   <a href="" title="Rolling Sky Game"><b>Rolling Sky Game</b></a> is a 3D game. There are many different levels of play at the levels of increasing difficulty. At a high level, you will have to overcome many more obstacles, requires ingenuity, agility and persistence. Are you ready?  

Interesting post! This is really helpful for me. I like it! Thanks for sharing!

- gmail sign up

This improvement will change a lot of work in controlling. Thanks for sharing.

google maps street view

email sign up

Thank you for sharing! Can you sharing some updates on how you have made this powerful post!

- [url=]Baby Names[/url] 

- [url=]Usps Tracking[/url] 

- [url=]Beyonce Net Worth[/url]  


All pics are informative. thanks for sharing. FL Studio 12 Regkey

—Priya Rani

The article you have shared here very good. This is really interesting information for me. Thanks for sharing!

- gmail sign in

Plus Free Flash games online Play Free sudoku hearts minesweeper freecell spades yahtzee Free Flash Games <a href=""></a> unblocked happy wheels <a href=""></a> Play Free sudoku hearts minesweeper freecell spades yahtzee <a href="">free spider solitaire</a> Play Free sudoku hearts minesweeper freecell spades yahtzee <a href=""></a> Play <a href=""></a> Fireboy & Watergirl unblocked


This is one of the cult game now, a lot of people enjoy playing them . Also you can refer to the game :  animal jam 2 five nights at freddys 2 | hotmail login

Thank you for sharing! 

driving directions

—Driving Directions

Post new comment

The content of this field is kept private and will not be shown publicly.
  • Web page addresses and e-mail addresses turn into links automatically.
  • Allowed HTML tags: <a> <em> <strong> <cite> <code> <ul> <ol> <li> <dl> <dt> <dd> <p>
  • HTML tags will be transformed to conform to HTML standards.

More information about formatting options