DIY Electric Assist Wheelchair

[csm]

I have seen a couple electric assist wheelchairs. It is kind of like the pedalec of electric wheelchair systems. It apparentl has en electric hub motor for each side wheel. And each wheel has a motor, controller, and lithium battery in it. It has a switch that attaches to the hand rail ring which is articulating to trigger the motor assist switch. It has an 8 LED battery charge indicator on the side of each hub, that turns off after non use of a few seconds (this may be a good think for electric assist bikes with LED battery charge level indicators. It also has a remote control which can change the controler settings. The chair apparently cost about $7-8k (minimum). I was think this technology could be cheaper. And I was thinking how could I create a similar switch assist in the hand rail. I was thinking that the Golden motor may be a good canditate for a hub that could be hacked, to contain the batteries controller.. and mounted with a switch that could be linked to a hand rail attached to the rim. I thought I would open this project up to the rest of you for your contributions and pleasure.

Here is some basic graphics on the system:

Here is a commercial promo video for the e-motion electric assist wheelchair:
[youtube]ZWKsMYVUNOE[/youtube]

Here is a lecture on why people may benefit from electric assist wheelchairs. There is a parallel, folks, with why people may opt for using electric assist bicycles. It also includes examples of different types of wheelchairs. One of the issues with using only manual powered, is the development of joint problems, such as spurs, and tendon ligament disease/injury, including things like carpel tunnel syndrome, repetitive motion injury, arthritis, numbness, etc.
[youtube]CcyEPlobfdA[/youtube]

User's Manual (PDF):
http://www.alber.de/fileadmin/content/downloads/BDA_emotion_M10_e.pdf

Specifications:
http://www.alber.de/en/products/mobility-wheelchair-emotion/specifications.html

Technical Data:

Batteries
25.2 V; 6.0 Ah; Lithium-ions, leak-proof and maintenance-free

Charger (input)
100-240 V AC

Charger (output)
30 V DC

Operating voltage
25.2 V

Speed
support 0-6 km/h

Power-rating
2 x 60W

Climbing capability
restricted to wheelchair model

Range (1)
approx. 25 km

Maximum permitted total weight
180 kg (396 lb)

Weight of components:
Wheels (2)
each 11 kg (24 lb)
(1) According to ISO 7176-4

 

[amberwolf]

I have some old sub-C NiMH packs for older E-motion systems. Unfortunatley I don't have the motors or wheels. It's an interesting idea, because you can basically take the wheels and stick them on just about any regular wheelchair for an instant assist capability.

As I understand the older version at least you simply used the wheelchair exactly as normal, except that it would turn your arms "bionic", by applying power to the motor every time you manually rotate the wheel. It would work the same whether you are an assistant pushing teh chair from behind, or the occupant doing it by hand. Even pulling the chair along with your feet would get you an assist. I believe thtat the assist on this is much finer than on a typical pedelec bike, so that you don't have to wheel along for a while first and then suddenly get a jerky boost,b ut ratehr just a smooth addition of power as soon as you begin to move the wheel.

I expect it is using feedback from the motor coils vs the magnets to determine position, or a sine/cosine encoder with fine magnet resolution in it's encoder ring, or possibly evne an optical encoder with extremely fine resolution. (the latter is probably the finest resolution of any of these, at a guess).

 

[Samd]

I never thought of an electric assist wheelchair before. Makes good sense.

My aprilia enjoys are originally electric assist, and for what you propose it would work very well. The aprilia thread might be worth a read. As well as the original logic.

It works by some cadence magnets triggering a reed switch as I understand it. If you are accelerating it tries to do so also as an impulse, then maintain a basic speed.

Plenty of cheap chinese 3phase controllers seem to have the capability built in, but I know little of it as I have always disconnected it and gone for direct drive. I have struggled to find a decent application before you highlighted it today....

 

[Hillhater]

... aprilia enjoys are originally electric assist,
It works by some cadence magnets triggering a reed switch as I understand it.....

Samd,..the aprilia system is a "Torque sensing" system, which attempts to match the riders efforts.
But you are correct, a similar system would work if incorporated into the chairs hand rims, such that forward or reverse pressure on the hand rims, initiated matching torque from the wheel motors.
I Think Aussie Jester would be a good consultant for this project !

 

[LockH]

[youtube]6NqdMN9tJL8[/youtube]

 

[mettleramiel]

I will tell you as someone in the industry, these systems are pretty much universally hated. They seem like a good idea because you can still use your chair manually when you want to, but switch to assist when needed. The problem is that the wheels add so much weight to the chair, that you end up using assist all the time which defeats the purpose of having a manual chair to begin with. We get customers excited to try these out constantly and for every 100 trials we have, we might have 1 sale. The wheels can be popped on and off with just one push-button, but no-one wants to pay so much for an extra set of wheels that they might use once in a while.

All that being said, they are easy to get used on the cheap. So far in my experience, the batteries are top notch and have still held some juice after sitting dormant for years.

 

[spinningmagnets]

Lately, I've seen several companies that are making something similar to this. If I was in a wheelchair, I think I'd try one.

https://www.youtube.com/watch?v=zomjLf6nbKI

[youtube]zomjLf6nbKI[/youtube]

 

[MrDude_1]

I play leauge pool and there are quite a few guys with chairs that have hub motors.

I was under the impression that the hand ring on each wheel is connected with a torque sensor, so for every amount of force applied to the ring, it could apply a "amplifying" assist... To use a non ebike example, its just like electric power steering, except the wheel it turns is fully rotating.