Electronics > Mechanical & Automation Engineering

"Best" robotic arm geometry?


I'm thinking of building a 5Dof or 6Dof robotic arm as a project, I've done enough designing of other robotic parts I'm confident I can do it, and I've used cobots (UR5 type) before during some past jobs. The main thing I'm building the arm to do is test some ideas I have about 3d printed parts, I'm not so much in a situation where I'm looking yet to build it with a specific reach and carrying weight, nor yet have I so much decided on exact actual size (but it will be relatively small), so everything I'm asking here is to be proportionally scaled.

What I am trying to work out is what the general "best" kinematic arrangement looks like in terms of joints, Denavit-Hartenburg parameters and relative link lengths. By "best" I mean the one that can most practically reach the greatest variety of positions, the most spatially versatile.

I know that often the really huge industrial robot arms in things like car factories have pretty limited DoF, the design is all about putting heavy motors at the base, and in doing so they often use linkages rather than rotary joints at each joint. And when I used UR5 robots I found that while able to reach complex positions they VERY often went in to "gimbal lock" and other situations where the inverse kinematics couldn't work well, the actual workspaces where the tool end could reach a wide variety of angles was a lot less than the overall workspace that could be simply reached in 3 dimensions.

So I know that the choice of kineamtic layout and link lengths has a really big influence on an arm's versatility.

I can find resources online comparing SCARA/polar/6DoF to each other, but can't find much discussing how different 5Dof and 6Dof layouts compare to one-another.

Can anyone point me to such discussions and articles, so I can get a feeling for whether there is an actual best geometric layout for spatial versatility, or if not whether commercial designs are each optimised in layout for a different parameter than spatial versatility (for exmaple prioritising payload weight instead...).


Any thoughts on where I might find discussions of this. The trouble is most searches for kinematics bring up all the equations but not much discussion of the abilities different arrangements and relative link lengths provide, and searches about "best" bring up specific models of arm rated on things like price or programming interface, both utterly irrelavant to the question of the best geometric architecture to go for when designing your own.



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