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Member Since 28 Feb 2013
Offline Last Active May 17 2017 03:40 PM

Posts I've Made

In Topic: What field of study deals with articulation(joints) efficiency/practicality d...

02 February 2016 - 03:11 PM

I have special interest in know how they come up with the best joints for the best task, like "oh, i need x degrees of freedom here, but it needs to support y weight, so since Im limited to materials s and z, I think joint j will do the work".
Is it mechanical engineering? is it industrial design? is it not really present in a single field? I mean, robotics is pretty generic and deals with a million of different stuff.
So, say a team is making a robot, say something like big dog, how/when exactly the joints gets decided..?


Those questions usually fall in the mechanical engineering (ME) discipline. ME basically touches all other engineering fields and some of everything's in there. You're right that robotics is something that crosses a lot of disciplines, but your questions about joints and materials would be ME all the way.


You've actually described at a very high level what engineers would do. First, you have to define your functional requirements. This is usually like a use case, or some specific set of "must-haves" in the design. Sometimes that may be the total degrees of freedom, but sometimes that's simply "the machine must be able to do X or Y". This usually frees up the constraints in the concept generation phase. At that point, you come up with a basic design that may work functionally. You check that design over to see if there are any obvious problems with it, then you start analyzing it. There are lots of different analyses you can and should do, such as kinematic (to see range of motion and maybe if it can crash into itself), structural (to see if it can hold itself up or if the material will yield during operation), joints (like what kind of torque you need to move the robot armatures around), tribological (to see if friction/wear is a problem and where it is), tolerance (to see if the tolerances on different subcomponents are too tight or too loose for assembly), failure safety, motion repeatability, and so on. This is the basic design process. If at any point you come across a problem that is "unsolvable" (i.e. the joint type causes stress peaks that yield your material or the parts cost too much), you've got to go back and redesign. The further down the process you go, the harder it is to go back and redesign, so usually following rules of thumb help you save yourself early on. You don't always have to do those kinds of analyses. If you're trying to build a one-off or a prototype, you may not care if your tolerances are defined for general manufacturing. It does help, but not completely necessary. It just depends on how you're comfortable proceeding.


Mechatronics is kind of like a hybrid of mechanical and electrical engineering and deals with the application of electromechanical components. I would think a lot of the knowledge of servos/motors/etc. would be there as well as in electrical engineering. AFAIK and I was told, electrical engineers don't deal too much with this type of thing anymore because they do a lot more signal processing and systems design (the kind with complicated ODEs and filters and things I don't fully understand).


If you're interested specifically in how joints are studied and forces calculated (roughly), then I would suggest "Design of Machinery" by Norton (ISBN: 978-0077421717). " It's not the best book on the subject, but I know what's in it since I used it in my kinematics class way back when. Once the kinematics is explained, it goes into how to calculate forces. Check it out or borrow the book (or PDF?) from somewhere.


Good luck!

In Topic: "Real-Time" Smoothing

01 February 2016 - 03:16 PM

Hey @L.Spiro, did you find what you were looking for? It would be very interesting and  helpful if you were to post your solution (or workaround) :-)

In Topic: Calculate time t along a 2D cubic bezier equal to a given tangent vector

19 January 2016 - 12:28 PM


That's a really elegant way to pose the problem. Good find!

In Topic: [Solved] What's the best type of curve for this case?

12 January 2016 - 01:59 PM

Bezier curves were designed to be natural for non-mathematics types to use them. They can loop, but as stated before, but that behavior can be controlled. I would try it out and see.

In Topic: Random Math Questions

15 September 2015 - 10:55 AM

Well, I'm just curious about the building blocks. I've spent hours on per-algebra, and some on algebra, and a quite a few on trigonometry learning the basics. Still, none of it had anything to do with this... What's going to make understand what you've said here. Have I skipped a math subject?


I don't think you've really skipped anything. Seems to me one of the problems is that the math books and things you've been reading aren't helping you understand how to apply the info to do what you want. It's a learning process.


I'm gonna check out the vector 2d math. This stuff is kill'n me.. I would never have guessed that formula, and don't understand the explanation. I just don't think I'm smart enough for this game stuff. I keep trying to get better at it, but I just don't have the intelligence... I guess the only thing I can do is learn math, and hope it clicks in.. not sure... just learned a bunch of algebra, some trig, and it was no use... nothing I learned in the past 4 days applied here..


Another potential problem is that you might be overwhelming yourself with trying to understand all the math at once. It took me several years in secondary school to wrap my head around these concepts. Like any practiced skill, it's only "easy" once you've done it a thousand times. Plus, if you're really trying and still don't understand it, it's not your fault. The job of any teacher or learning tool is to break down the concept. My personal experience of learning new things from the Internet is that it takes a lot more time since it isn't always broken down nicely and there's no one to really ask (except on forums). Even then, it's hard to explain it over text.



One last thing, have you checked out BSVino's Youtube videos? At the very least, they'll help you see how the math is used.