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| Axis | Maximum Backlash | Gearbox Style | Maximum Mass for Gearbox + Motor | Motor Voltage | Motor Type |
|---|---|---|---|---|---|
| A1 | Zero backlash | Right Angle or In-line | 0.8kg8 kg | 48V | BLDC |
| A2 | 1º (60 arcmin) | In-line | 0.8kg8 kg | 48V | BLDC |
| A3 | 1º (60 arcmin) | In-line | 0.8kg8 kg | 48V | BLDC |
| A4 | 1º (60 arcmin) | In-line | 0.8kg8 kg | 48V | BLDC |
| A5 | 1º (60 arcmin) | In-line | 0.8kg8 kg | 48V | BLDC |
| A6 | 1º (60 arcmin) | In-line | 0.8kg8 kg | 48V | BLDC |
Option 2
| Axis | Maximum Backlash | Gearbox Style | Maximum Mass for Gearbox + Motor | Motor Voltage | Motor Type |
|---|---|---|---|---|---|
| A1 | 0.067º (4 arcmin) | Right Angle or In-line | 0.8kg8 kg | 48V | BLDC |
| A2 | 0.6º (36 arcmin) | In-line | 0.8kg8 kg | 48V | BLDC |
| A3 | 0.6º (36 arcmin) | In-line | 0.8kg8 kg | 48V | BLDC |
| A4 | 0.6º (36 arcmin) | In-line | 0.8kg8 kg | 48V | BLDC |
| A5 | 0.6º (36 arcmin) | In-line | 0.8kg8 kg | 48V | BLDC |
| A6 | 0.6º (36 arcmin) | In-line | 0.8kg8 kg | 48V | BLDC |
Requirement 3 Response
We are open to implement any suggestions you provide, however . These are some potential options we looked at available on Electromate. To compromise on cost, we might want to try to integrate one harmonic gearbox on A1, then planetary gears on A2-A6. A1 has a low load but requires the highest amount of precision, where as A2-A6 require higher torques but have greater permissible backlash. We can look into implementing 6 harmonic drives in our arm within our budget, however we should also plan to be realistic. Here are some ideas of the types of products we have looked at as potential options.
Motor Selection Ideas
EC-flat motors offer good torque and have low cost at Maxon. These seem like a good selection choice for us, but we are also open to other suggestions/motor types.
- Maxon EC-Flat Series (low-ish weight, decent continuous torque and affordable pricing)
Harmonic Gearbox Ideas (to be used on A1)
These are all lightweight options which can provide an output torque required for A1.
Note: these may also be good options for A2/A3 as harmonic drives offer high ratios on a single stage. If we can afford these gears for A2/A3, it would be excellent
Planetary Gearboxes (A2-A6 options)
We've looked at these planetary gears as they posses low weight, low backlash and potentially have low costs. Some of these products, such as the XTRUE planetary gears will not be able to provide sufficient output torques for some of the joints (namely requirements for A2/A3). However, we are open to adding second stage reduction via belt drives to improve torque capabilities in our design.
- XTRUE gearheads from Thomson Micron (these could be used on A2-probably be more applicable for A5/A6)
- HPN gearheads from harmonic drive (good for A2-A6)
- Maxon Planetary Gearheads
Requirement 4 Response
How does 400 CAD per gearbox sound? For the arm, we will probably want 2-3 gearbox spares (per recommendation of Cory I think...) . If we buy 8 gearboxes, that will cost $3200 and comes to 15% of our total rover budget... seems reasonable to me I guess. I think overall the team has around $11,000 funds right now, so we don't want to eat up our actual parts budget too much as we still need to buy motor and drivetrain stuff.
Backlash Requirement Reasoning/Justification
...
We probably need some mass restriction to make sure that the arm doesn't become ridiculously heavy. We are currently aiming for an arm mass of 10kg, and the rest of the arm will consist of mating and structural components that can be optimized for mass design through carbon fiber or whatever. Kinda freeballing it, but I'm going to give a lofty goal of maximum 1kg 0.8kg per motor/gearbox combo. We can refine this if Gleeson finds the requirements too strict. There's not really any rhyme or reason for mass; I just figured that having our arm mass consist of ~45% motors seemed appropriate. I'd like input on this assumption.