Motor for Powered Wheelchair for a disabled (awesome) friend

[ashinu77]

Hey beautiful people,

 

So I have a friend who suffers from Muscular dystrophy, a disease in which your muscles and bones degenerate over time. He is 28 years old, weighs 90kg and has not stepped out of his apartment house for over 12 years (since his apartment does not have an elevator and his parents are too old to lift him around). If the pandemic has taught me anything, then its that life is short and you need to see the world when you can.

 

He is a beautiful person, tech enthusiast and a heavy gamer and I want to do this for him

 

I want to build him a powered chair and I want your help with what kind of motor I should choose. A normal industrial-grade DC motor (the e-bike motors) won't do because it just is too fast and even if I slow it down with a gear assembly, its low torque makes it dangerous for him to control because of low handling (he has brittle bones too).

 

So I need something with a high torque, like a servo motor, which my friend can control very precisely. Speed is not a goal here. Safe mobility is. But a servo motor is not continuous in its rotation but I would very much like something with as much control as that. So can you people please help me out in choosing an appropriate motor(s)? Experienced members can even tell me its wattage, and other technical specs. I'm a mechanical engineer, I will understand

 

Please note: I am an excellent fabricator (I can definitely build something swanky that supports his weight and still look cool) with intermediate level of expertise when it comes to electronics and control systems using basic computers such as arduino and raspberry pi. So please do not hold back if you have got in-depth ideas.

 

Many might be thinking - there are ready to use power chairs out there, why not go for it? Reason is - we're in Mumbai (India) and they're just not available here. Import duty alone will be 5x the product itself and the pandemic makes nothing easier. Also, there's something fun about DIY projects so there's that too haha (same reason why we love building PCs when you can buy an pre-built Origin or NZXT eh? ).

 

Down the line, after this basic problem is tackled, I plan to slap some RGB underglow and what not on this as well haha, I shall be posting the progress pictures if the community is interested 

 

Thanks people :)

[Evolution.]

Tagging @CircleTech  and @BuckGup

[paddy-stone]

Following.

 

I probably can't add anything here, but as a "disabled" person myself I am interested in what you are trying to achieve. This is a really nice thing to do for your friend

 

I love some of the all-terrain wheelchair type vehicles that people have made. I haven't seen it myself, but believe Jerryrigeverything youtuber has built or is building something similar for his wife, so might want to check that out. He is usually pretty good with things like this, and he will possibly say what components are involved in the motor etc.

[Drama Lama]

2 hours ago, paddy-stone said:

haven't seen it myself, but believe Jerryrigeverything youtuber has built or is building something similar for his wife, so might want to check that out. He is usually pretty good with things like this, and he will possibly say what components are involved in the motor etc.

@ashinu77

 

https://www.youtube.com/watch?v=Uhq5_6aq1Lg&list=PL0vZL9uwyfOEHDP0omDpmYJ0zawk1VnM9

 

that's a playlist

 

hope it will help

[BuckGup]

https://www.castlecreations.com/en/castle-2028-1y-sensored-motor-800kv-060-0064-00

 

It's roughly a 10 horsepower motor with insanely fine tuning possibilities due to it being a brushless sensored motor and ESC combo. You would have to do the math for the gearing but you wouldn't want a wheelchair going 30mph anyway, or you might lol. This is sorta overkill though and a standard motor you find in a junk yard or old electric wheelchairs or powerwheels would suffice. 

[Thaelin]

0_0  Smokem dude! Wheelie bars included? Mobility should never be drab for sure. My fat tire EBike "can" do 45 but!

[TehDwonz]

On 9/5/2020 at 8:59 AM, ashinu77 said:

I want to build him a powered chair and I want your help with what kind of motor I should choose. A normal industrial-grade DC motor (the e-bike motors) won't do because it just is too fast and even if I slow it down with a gear assembly, its low torque makes it dangerous for him to control because of low handling (he has brittle bones too).

You'd get more torque by gearing it down - that's what they're for  Perhaps a salvaged golf-cart motor would do the job? Or, if you feel adventurous, a milk-float style one?  

[ColinLTT]

I would suggest a brushless motors with a O-Drive https://odriverobotics.com/

[akio123008]

A 100-150kV BLDC motor with a home made 20:1 or so gearing can do the trick. If you get a sensored one and operate it with a VESC you can control it down to crawling speed. Similar to @ColinLTT's idea, except the VESC may be easier to obtain and cheaper. 

 

The important thing is, you want a low speed (low-kV) motor, otherwise your wheelchair ends up either going waaay too fast or in need of extreme gearing (which is difficult to fabricate, we're talking 40-100:1 kind of ratios. to give you a rough idea, my e-bike has a 190kV motor, which is already considered quite low, and even with a 7:1 gearing ratio, it gets up to 50 km/h.) I'd aim for a motor that's <150kV, preferably under 100.

 

An alternative idea (which I'd actually use here, given it's the cheapest and simplest) is to use some old DC motor from a mobility scooter or something similar, which you can control very well using a cheap PWM motor controller. That way you have a motor that's essentially designed for the task, and very fine control. Brushless motors need expensive and complex control systems to allow for very precise control (something like an Odrive or VESC) whereas a normal DC motor can be controlled extremely well using a standard PWM motor controller.

 

[ashinu77]

Hey there everyone, thank you for all your replies. Based on availability, I'm going for a brushless DC motor I found for cheap in a workshop near my area. I'll be using the method of giving it low voltage to cap its speed and a mechanism who's name I do not know but it does not allow movement of the chair unless the user actively pushes the joystick forward(or backward). Will be going for dual motor system, powering the two wheels individually. And turning to be achieved by alternate direction of motion of the 2 wheels.

 

In all, speculated cost from start to finish is around 40,000 Indian rupees, or around 550 USD. Which, I think is not bad and something I can afford. So, lets see how it goes. Starting the skeletal fabrication of the chair this weekend, electronics to be the last sprint  Thank you for everything you guys!