Page Comparison

Motors

• Obviously, we need to select BLDCs
• Will be selecting 24VDC BLDCs and scrapping 48VDC motors due to availability
• Integrate RLS or netzer encoders into joints, not broadcom AEATs

BACKDRIVING

• A1 is backdriveable but will not experience too many loads to backdrive it when driving around
• A2 and A3 both passively backdrive
• A4 has some backdriving (not much) under 5kg load
• A5/A6 occasionally had minor backdriving under 5kg load (only witnessed this once, but other times throughout testing it did not backdriving)
• Opinion: backdriving is only a concern on joints that passively backdrive when the arm is unloaded
  • Don't want to constantly consume power to hold arm position when unloaded
  • When arm is loaded, we will be drawing power/current anyways and will not carry high loads under extended periods of time - thus we can probably pass over fixing backdriving on A1, A4, A5, A6
• Worm gears or breaks for A2/A3? Or just choose a transmission option with high enough internal friction to counter natural mass moment (risky, easy to get wrong)

Axis 1

• Current belt tensioner loosened over time - and is somewhat difficult to readjust/tension on the fly
  
  • Solutions:
    • Apply a lead screw tightener
    • Use static tensioners (like the bearings idea on A3)
    • Switch to gearing (see kaydon bearing)
• Turntable bearing is not sufficent. Entire robot base tilts when larger moment loads are applied to A2
  • Solutions:
    • Spec a proper crossed roller bearing with high moment, axial and radial load tolerances A1 - Turntable Bearing Options (Kaydon, iGUS, chinese bearings, mcmaster)
    • Currently chasing down SKF on if we can spec a turntable bearing from Kaydon through our sponsorship
      
      
      • These bearings come with no teeth, or teeth on inner/outer race depending on config. If these are available, we can remove the belt and simply use the kaydon bearing as a gear/bearing at the same time - saving weight and components.
      •  Rated for various loads, weigh 200g-500g
• Better cable management solutions should be integrated for this pairing

Axis 2

• Obviously belt drive does not work due to slipping
• Single stage reduction option availability seems initially slim (based on Electromate comms, not much external research has been completed)
• Other than that, A2's linkage and frame construction seems OK
• Simplify construction and reduce number of parts for next revision
• Better cable management solutions should be integrated for this pairing

Axis 3

• Comprehensive load testing on A3 has not been completed, but from initial observations it works well. 
• Reduce weight if possible / simplify number of components for next design
• Should reduce the transmission ratio on the belt. A3 is currently fine, but if anything is learned from A2 large belt ratios can occasionally be unreliable
• Closer to chris annin
• Better cable management solutions should be integrated for this pairing

Axis 4

• Experimental loads are higher than initally calculated, however they are still within a similar range to A5/A6
  • We can likely still spec the same motor + gearbox for all three of these axis
• Design can likely be simplified, implement off-axis encoder to reduce weird components
• I think we should continue to have the A4 motor stick out on the opposite side of the link (counter act the moment)
• Better cable management solutions should be integrated for this pairing

Axis 5/6

• Differential is very rigid/stable
• Experienced loads are higher, internal tooth meshing friction may be high but also there may just be significant dynamic torque applied
• We are still within our expected calculated range (with SF), current requirements with SF are likely sufficent for upcoming design
• Reduce bulk for upcoming design
• Improve cable management
• Better cable management solutions should be integrated for this pairing