Differential Screws, 11 Lenses, Harmonic Gear (robot series)

dc42

Slide rules? Luxury! (with a Yorkshire accent)

deckingman

@dc42 Yes - pure decadence. We even used paper and ink - none of this slate and chalk stuff (although the teachers used blackboards and chalk). I think it was mostly because chalk made good missiles to throw at wayward students (or in the case of one teacher it was a great big lump of wood in the form of a board rubber). I never did work out why giving a student concussion would make them pay more attention........

JoergS5

@tony73 I've managed to have a working kinematics and inverse kinematics code for 6 axis robot now, based on Jacobian matrix calculation. I need about 3 iterations to approach an exact inverse kinematics position and orientation, on the PC about 5 ms for 100 segments. I hope it's fast enough for running it on Duet.

I proceed with building differential screw / 1:1 lens / harmonic drive now to build a robot prototype.

tony73

@joergs5
Hello! how is the design of the six-axis robot progressing? I look every now and then if there is any news!

JoergS5

@tony73 I thought about I have to post news the next days how it's proceeding.

I went back to school in a figurative sense the last two months to learn more about robot kinematics, especially matrix calculations, so there was no development. I'll proceed with building soon.

Core elements are differential screws (I need them at multiple places), encoder support and diy harmonic drive, and finishing the RRF kinematics code. I'll use OpenCV for quality checks, it's a great program, I can recommend the book of Escriva/Laganiere about OpenCV 4.

I'll use OpenCV together with the cameras/lenses for

check the quality of the harmonic drive teeth
check printing result while printing
CNC position checking, 3D printing object position checking, SMD placement
homing position checking
measure precision of the kinematics (joints, steppers, belts, pulleys)

The patents of harmonic drives are interesting, I follow inventor Aubin with US5456139, EP0640778, US5662008 and similar from Ishikawa to optimize teeth. I try 3D printed parts first (using PP for the flexspline), but if it's not sufficient change to drilling with CNC with spring steel.