I’m trying to build myself a manual wheelchair power assist on a budget since I have issues with fatigue but can’t fit a powerchair in my car (a power assist is kinda like an electric bike but for wheelchairs, it’s not fully powered but does provide some help) and I realized that a single swerve module in the back would be perfect and much less expensive than commercial models from medical manufacturers. Any teams have an old edition of swerve like a mk2 or a prototype that is functional and not being used anymore you’d be willing to send me? it doesn’t need to be of comp quality, just needs to be decently usable, and can be fairly low speed. I am open to paying some for it but looking for less than what swerve usually costs.
Do you have a plan for controlling/powering the module?
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Figuring out what battery to get and i need to talk to someone more talented at programming then I am but I think a button control panel would be easiest (or something that responds to resistance against the motor, e.g. if i roll forward a couple seconds it starts going electrically, and stops when I pull backwards)
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LiFePo4 over LiPo or Li-On if you have the budget! They charge very very very fast and are safer to use. They are very popular in RV, Boat, Robotics as batteries. They have a similar size/shape to standard sla batteries but weigh significantly less. I’m not sure what you need for capacity. An 18ah 12v was around $180 when I’ve bought them for random projects at home.
Dakota Lithium is who I’ve used but there are other brands out there I’m sure. I use them in series for 24v AMRs (autonomous mobile robots) and get easily 8+ hours towing payloads. The difference is I’m not directly supporting the weight of a person on it. I’m towing boxes and totes on their own carts so my runtime would be different than yours. Still 18ah is a lot of capacity.
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Very interesting idea. One thing you may consider is if you even need directional control. If it is just a passive castor, then perhaps all you need is one motor for drive and it will help.
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I think directional control would actually be really helpful, since right now if I go on any sidewalk with a slight slope perpendicular to my direction of travel (about 5° is enough to make a big impact) i go way off the side and into the road 
Having some way to correct the angle other than constantly stopping and turning would be way less stressful lol, it turns out a large majority of sidewalks are slanted for rainwater drainage
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I have thought about this more and I am actually thinking taking apart a cheap electric skateboard would actually work well and be less tricky to engineer…
What would be the best way for me to make it able to turn similar to a caster or swerve?
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I would look at heavy-duty hobby-type servos for turning, in this case.
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How would you control the rotation? I think that a powered caster wheel, or powered esk8 wheel on a custom caster pivot, might be simpler.
Ditto on using LifePo4 if you can afford it. They seem like a perfect fit for this application.
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I can’t figure out if it’s better to have motorized rotation or put it on a bearing and turn with my hands on the pushrims like i normally steer
Old timer here. Twenty years back, I developed a drive unit (motor and motor control) of a power assisted chair called iGlide for J&J. They took it up Pike’s Peak as a demonstration.
The control method was based on strain gauges built into the hand rims. For a short time interval, wheel motors would respond to the strain gauge signals by accelerating each wheel in proportion to the effort exerted on that hand rim. After that short interval, the control reverted to maintaining the speed and heading that had been achieved. People using the chair reported that it felt natural, but as if gravity had been reduced so their own strength was boosted.
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Okay, after sleeping on this overnight I have some ideas. I bought one of these
off of craigslist to convert into an RC drivable chassis. It worked but what made me think about it again was @asid61 mention of the castor. This has two powered wheels and then a dead swivel castor in the rear.
There are two joystick controls originally on the handles but I bypass all of the original control board and use a much more custom motor controller hooked up to an esp8266 and webpage with a joystick. In your case you would probably want at minimum an estop system to cut power even if you don’t want a full control panel.
What I’ve learned driving it around myself is a swivel castor sucks on bumpy terrain so make the castor huge to give yourself the best odds over unknown terrain. The castor on this can’t for instance jump a curb. It works fine on grass though because it’s wide. Go for at least a 3 or 4 inch wide (not diameter) tread, maybe even a big 8 inch diameter pnuematic if you don’t want to go wide. The pnuematic tires will spread out the weight better on “mushy” areas
Ps: the power wheels thing is driven here from the webpage app. You get a good look at the castor on some concrete. Cracks are fine, pot holes or curbs are not
I’m gonna stay tuned to this thread overall cuz I’m curious to see where it goes!
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The iglide isn’t manufactured any more but it seems a couple other companies have very very similar designs… Only problem is they cost thousands per wheel 
Do you think it would be doable for me to make one with very limited budget and limited experience?
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Would these wheels be strong enough to hold my weight? Reading the item description it seems like it’s for toddlers (i weigh 90lbs and the chair weighs 25)
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The wheels it comes with are hollow plastic, they might work but the motors on it are designed for the child size payload. The wheel is attached the the motor with a customized hub, I’ll send some more detailed pictures tonight. What would work almost as well is wheel barrow wheels which are meant to hold a really heavy payload and have a generic standard hub for attachment. Of course idk how you’d get those wheels onto that chassis if you were doing a retrofit.
Yes. I knew that iGlide ceased production long ago.
My post was just a suggestion on possible control architecture, not re-using any particular hardware. I like your idea of using a swerve module – the question is how best to control it.
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I heard from a team that might have an old sds mk2 to give me, which is amazing. I have no experience building a swerve frc bot so i’m not sure what other parts I need to get… I’m assuming I need a battery, joystick, and motor controllers? What am I forgetting?
Well, you would also need some way to control it, like a roborio, and circuit breakers/fuses to make sure you don’t have a fire.
You can use an Arduino and Talon SRX or Victor SPX with PWM motor control with some joysticks. That saves at least $400+ not having the Rio in the mix. Swerve on an Arduino isn’t easy though from a programming perspective. Definitely possible though.
Edit: I second the circuit breaker and fuses, depending if its USB joystick or analog makes a big difference as well for Arduino
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Are those compatible with neo motors?
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