This is awesome! thank you! I was able to script this in python in half a day while I knew nothing of matrices before I watched this video. One thing I can't get my head around though. When calculating IK, aren't the α and Θ compensation values of J4,J5 and J6 from the DH table used at all?
I was watching the "Made with Layers" Channel where he built an AR4 but at the end he mentions how much wobble the arm had. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-4xD9QCBkxAs.html Was there something in his build that he did differently because the results from your version and his look very different. (perhaps a parameter was set wrong or where he set the tool center offset 300mm from the Arm at the 14 minute mark ?) I'm just starting out so I don't know enough to comment so just looking for some insight. Thanks
I did see his video. I sent him this response in the comments: @Thomas, Thank you for building the AR4 and highlighting some of its features. I did want to touch on a few of the comments you made. In the overview section of the manual I do mention pre-applying solder to wires being joined together - I find it easier to pre-apply solder or tinning the ends - and then bring them together with the iron rather than trying to hold the wire ends together and hold the solder and hold iron at the same time, not having 3 hands - it helps to pre apply the solder. None of the wires going to the breakout board call for tinning so I'm not sure about your comments on that? On page 143 I do have some groups of wires soldered together to help group them going to the 3 screw terminals as its a tight fit and difficult to maneuver them into position without them being connected but you could certainly use ferrules in this step if needed. At one point in the past the design did utilize plug connectors and building a wiring harness. Given different applications, motions and articulations all the low cost plugs I sampled proved to fail over time. With this small arm and the limited cable routing and cable arc lengths, direct solder with the solder joints in strategic locations using heat shrink proved to be more reliable, less bulky, less costly and not as time consuming as crimping and inserting numerous plug pins. The primary goal of this project from day one has been to realize a usable robot and at a very particular price point. I've worked with industrial robots my entire career and its always been a frustration that any usable robot was out of reach. There is an absolute threshold on the price as most educators have a budgetary limit so I have made it priority number one to stay under that limit. This drives many of the design aspects, The motors for example are off the shelf variants and cannot be fully customized without adversely affecting the price. There is a limit as to what OMC can customize on these coming from the factory. The machined components are kept to an absolute minimum and as many as possible are cut from flat sheet material. This also drives the bearing designs and tensioning designs as custom machined threads and spindles for locknuts for example is not in the cards at this price point. It also drives some of the belt selections. I did notice the belt tension on your build was far too loose resulting in a good amount of play. Here is a quick video of the forced deflection on my build. ru-vid.comlf_KFFiCdJA - Making the statement that "This robot arm is neither accurate nor precise, rigid or smooth" seems a bit harsh considering. A great deal of effort has gone into this project, I know you have a great deal of experience and a wealth of knowledge in all manner of machines and mechatronics and your design suggestions are certainly well founded but I wanted to explain these aspects of the project, and hope you will convey these points to your audience. Thank you.
Chris, are you familiar with JMC servos? Packaged in stepper form, with a built in driver on the motor. They accept step/direction signals just as a normal stepper would. They are fairly competitive price wise.
@@classicskatespots1 if there's gasoline in the carburetor it'll run off the carburetor otherwise you just run it out of gas and then switch it over to propane or natural gas.
You will need the AR4 motors kit from Stepperonline and the robot combo kit from Annin Robotics. Have a look at the robot kits page which covers everything needed. Total cost to build the AR4 is approx $1900
All I can say is WOW! Your resume in robotics, I would guess, is fairly impressive. Thank you for posting and teaching. Your channel is very fascinating.
i remember that stuff from school... Denavit-Hartenberg-Transformation..and so on.. hard stuff but very useful! great video! awesome and outstanding work at all!!! btw at least 360° = 2pi
Hi, can you show us the backlass of your arms ?? Im trying to create a arm but im the process to calculate the best economic option to improve the backlass. Thanks and good channel, im seing you since spain =)
I've occasionally followed your project. Very impressive stuff. It must've taken quite a lot of time to get this far. Huge props btw for making license so that ie. one man business could build one for him/herself and use it for something. I absolutely understand the "no copying or building and selling robot" policy, but nice you've left this so-to-say poor mans business possibility open 👍👍
Hey Chris. I just put in a request to join your site/forum. (Devinda) Just putting a comment here in case a RU-vid notification reaches you faster. 😁 I'm really excited to post. Sorry to bother u.
@@anninrobotics That does sound like a huge pain. Thanks for building a place for us to commune. I look forward to joining! Also, do you happen to have a Discord community?
The closest Kuka would be the KR4 agilus. I think the AR4-MK3 is pretty decent given the goal of making a low cost robot that anyone can build at a cost of just under $2k for a full aluminum version but its not going to be quite as good as a $20K industrial robot. I'll keep working on it though!
I worked with 2 ton Kuka robots, but i still enjoy watching your videos. This is a very usable robot, many DIY ones are not, hence i do not bother watching them. Thank you. Question, how is the "singularity event" handled? On big ones i would have to reprogram the move that would cause that, to avoid having the option of 2 joints being able to do the same move.
REALLY great work there Chris. My only "problem" (and it is not necessarily a problem for anyone else) is that the stability of such a (lets face it) "light" robot arm is not too good when you have a router spindle as an end effector. I would really like to have a robot arm that can act reliably and accurately as a multiple DOF CNC mill. But even though this robot will not be able to operate as one of those, the work you are doing and the innovations that you are implementing are actually jaw dropping especially as far as the control hardware and software goes. Possibly for your next robot arm you can team up with one of the aluminum foundry folk and machinists that are able to accurately finish-machine the castings and develop castings that will be an order of magnitude stiffer. But in the meantime I will keep watching. Thanks Chris
This reminds me of what "toy computers" did to "real computers" in the mid to late 1970s. The company that made the toy computers was named after a fruit. The companies that made the real computers, such as DEC and Wang, are long gone; whereas, Apple is still around.
