Arduino controlled wheelchair

[DougL]

And Ive only four wires from Shark Controller to Under chair Motor Driver.

right, I forgot we are working on a couple of different things in this thread and by different people. 4 wires, that's what I have on the Jazzy Select but 2 are power, one is INH and one is JSIG. IIRC, it was determined your Shark used a bidirectional communications between base and joystick controller so there is no separate INH line.

[Alli]

Hello,

i hope im posting to the correct topic of the forum, if not i apologize in advance. I am actually a novice to electronics i have just studied electronic engineeering at university for the last 2 years and i am relatively familiar with Arduino. As a personal project, I am actually trying to convert my mothers manual wheelchair into a simple electronically operated wheelchair. Im finding it really difficult to determine the Motor specifications more specifically the torque and rpm required to drive (lets say) 100kgs. I have a rough idea on the design of this chair. Im planning to use maybe 2 12Vdc brushless geared motor (As i read the brushless is longer lasting and the geared provides smoother control) to drive the wheels(This im still unsure about the diameter and thickness). Depending on the motors selected currently planning to use 24Vdc batteries. I have already planned to implement the motorized wheels at the back of this chair because it made sense from a design and practical approach. Also plan to use mosfets and h-bridge to control current to control the direction of the motor using an Arduino. Can some one please advise me on the required motor specifications and if possible relevant formula and also advise on the battery to drive these motors. Any help will be greatly appreciated.

[Burgerman]

Where to start...

Brushless needs to be sensored rather than the hobby type non sensored motors.
Geared = more losses, and is smoother only because it offers more poles per revolution of the drive wheel, or per meter. So a smoother high pole count motor, and direct drive is a better solution. But you need to consider the total wheelchair width, and a motor that will fit inside a wheel because of that. And the best tyres for a powerchair ar ones with large cross section, and a small wheel rim diameter like 6".

And why 24V?

Take a read here: http://www.wheelchairdriver.com/BM-MK3- ... rchair.htm

Note, that by doubling the voltage, (or halving the impedance) a massive efficiency gain is possible.

[gcebiker]

Kits available here http://www.goldenmotor.com/wheelchair.htm sound what you are looking for, specs on that page, else you could use the specs they list/adjust them as you need, for your own purposes.

SaberTooth, https://www.dimensionengineering.com/pr ... rtooth2x60 or one of their other models is what some people use as motor controllers.
Its cheaper and easier that what we are doing on this thread

[Alli]

Sorry Mr Burgermen, i didnt quite understand the the explanation on the motors. high pole count? direct drive? As for the physical size of the motors i have approximately 25cm length and 30cm space between the wheels depending on the dimensions of the motors. So i should have adequate space to accommodate the size of the motors.

The reason for 24Vdc is convenience and few electric whelchairs i checked online ran of 24Vdc, you suggest i use larger voltage battery?

Thank you the wheel specification makes sense i will look for something as you described. Thank you very much for you response. if you can please advise further.

[Burgerman]

Brushless with wheelchairs isn't easy. You wont get anything off the shelf. It wont be easy, and it certainly wont be cheap.

Not to say it cant be done, but to get adequate starting torque, and suitable smoothness isn't simple.

[Alli]

Thank you mr Gcebiker.

The first link you sent ill use to give me an idea of the specs to use on my design. Im actually from South Africa and the price of that wheelchair is basically R25000 which is basically 5 months rent of an average 2 bedroom apartment here. very expensive. Even the motor controller itself is almost R2000, that is really expensive. Im finding it difficult to actually determine what motor specifications is necessary in order to drive 100kg load, if i can get a start there than determining the battery capacity and voltage and current ratings will become slightly easier right? Also determining a motor controller will become slightly easier once i know the ratings of the motor and battery ? than i can find a better priced one here. Thank you as well for you input and assistance, i really appreciate it thank you.

[Alli]

Brushless with wheelchairs isn't easy. You wont get anything off the shelf. It wont be easy, and it certainly wont be cheap.

Not to say it cant be done, but to get adequate starting torque, and suitable smoothness isn't simple.

oh my, i didint know that it would be difficult. So what do you suggest ? please forgive my ignorance, i want to learn and after battling on the internet i realized itl be best learning and taking the advice from those well experienced with this. i have a reasonable budget to work around depending on the design and whats required. Roughly 600 USD. Please advise if its not too much trouble

[Burgerman]

Well it depends if this is a serious functional wheelchair you want or just a toy to experiment on.

Batteries are the biggest issue on any powerchair unless you only use it to watch TV. These compete with space for motors, wheels etc to keep width as narrow as possible. Its all a careful balance.

Torque, control, and smoothness. are important. That means big expensive controllers and motors such as the ones I am using, with a lot of custom safety equipment, and development time, current sensors, contactors, code, etc. And that alone will be around 4 times your budget. Or considerably more if you go to lithium. And development time will be years rather than weeks.

So. Whats it actually for? Experimenting? Or serious use?

[Burgerman]

As a personal project, I am actually trying to convert my mothers manual wheelchair into a simple electronically operated wheelchair.

I hadn't read that bit. You might get away with small simple controller and small batteries. If you don't expect too much.

But consider this. The only thing a manual chair with add on power does better than a proper powerchair that was built that way, is be easier to lift into a car or a house. You ruin that to a large degree by fitting motors, batteries, controller etc. You sort of end up with all the disadvantages of each all rolled into one.

A normal powerchair is far superior for everything else. It is more stable, has bigger casters that work outdoors, better ride, much better range, usually better speed, and almost always better control. It has greater seating comfort, arms, and is much more usable.

You may be better looking at cheap used powerchairs with your 400 budget.

Its a bit like this.

A car is good at some things, keeps you dry, warm, comfort, quiet transport.
A motorcycle is good at another. It threads through traffic, super fast, and its nimble and can go places a car wont fit.
A motorcycle and sidecar, has all the disadvantages of both all rolled in one!

[Alli]

Well it depends if this is a serious functional wheelchair you want or just a toy to experiment on.

Batteries are the biggest issue on any powerchair unless you only use it to watch TV. These compete with space for motors, wheels etc to keep width as narrow as possible. Its all a careful balance.

Torque, control, and smoothness. are important. That means big expensive controllers and motors such as the ones I am using, with a lot of custom safety equipment, and development time, current sensors, contactors, code, etc. And that alone will be around 4 times your budget. Or considerably more if you go to lithium. And development time will be years rather than weeks.

So. Whats it actually for? Experimenting? Or serious use?

It is serious and I'm also learning at the same time. I think I bit of more than I can chew with this project, it sounds a lot beyond my capability and budget than I thought. I didn't realize it would be so complicated. I don't have much because I'm a student, I thought if I could make just a simple design just for mum to use to move around the house and when she's at the mall, I don't expect it to be spectacular but something to make her life a little easier. In this country its very difficult to get a decent second hand wheel chair and its difficult to trust people here they may hustle me. Its gong to take 2 years before I'm able to earn decently to beable improve my mothers standard of living. I have to try, if its just a simple chair for her to move around the house basically indoors? Thank you for your advice and honesty Mr Burgerman, I know that I'm really ignorant in this field thank you for taking the time to respond to my messages. If I may do a little more research present you with a design for something really simple I hope you will help me a little further.

Iv attached a very rough sketch of the dimensions and pace I plan to implement the wheels, just to give you an idea of the space I'm working with. Ill try to draw out the electrical design maybe you can give me pointers ass to what's needed to be added on. Thanks again for your help

[Alli]

As a personal project, I am actually trying to convert my mothers manual wheelchair into a simple electronically operated wheelchair.

I hadn't read that bit. You might get away with small simple controller and small batteries. If you don't expect too much.

But consider this. The only thing a manual chair with add on power does better than a proper powerchair that was built that way, is be easier to lift into a car or a house. You ruin that to a large degree by fitting motors, batteries, controller etc. You sort of end up with all the disadvantages of each all rolled into one.

A normal powerchair is far superior for everything else. It is more stable, has bigger casters that work outdoors, better ride, much better range, usually better speed, and almost always better control. It has greater seating comfort, arms, and is much more usable.

You may be better looking at cheap used powerchairs with your 400 budget.

Its a bit like this.

A car is good at some things, keeps you dry, warm, comfort, quiet transport.
A motorcycle is good at another. It threads through traffic, super fast, and its nimble and can go places a car wont fit.
A motorcycle and sidecar, has all the disadvantages of both all rolled in one!

Yes I understand, that's really appropriate analogy. I really Hope I figure something out. Thank you I will keep that in mind

[gcebiker]

I Designed these, initial versions were bolt on units for wheelchairs.
I now just build the chair sections to suit the end user...works out way cheaper and more easy to customize.

Parts (other than frame, subframe, forks, wheel guards)are off the shelf components
Front wheel = Electric Bike wheel (Double reduction Freewheel Planetary Drive, low speed 12km/hr on LiFEPO4, high torque)
Rear Wheels = Detachable Wheelchair wheels,
Standard bicyle parts for brakes, throttle, locking brake, basket.
Seat = Boat seat.

First version of how they are made now was using a rubbish kick scooter with welded up back section to hold wheels/seat/batteries.
As such they are hell cheap to build out of rubbish and lead acid batteries.

[Burgerman]

But its a scooter - not a tank steer powerchair.

As such power requirement is much less. Tank steer eats much more motor/battery power turning than it takes to go forwards. Or even correcting steering. And accuracy of control at low.starting speeds is less important. As is low speed starting torque at small pulse widths, motor compensation/or feedback tracking becomes important etc.

But its not a wheelchair. Will not allow most chair users to transfer into it, or use indoors, loos, tables etc. Those wheel motors, and controllers do not work well enough for a wheelchair unless its a temporary solution. It would work as a single wheel add on for outdoors though.

[flagman1776]

I agree with Burgerman. I'm impressed actually, that you have created a respectable complete SCOOTER. I AM a SCOOTER user. OUTDOORS. I can see your scooter design being useful for outdoor commuting but would be too large for in home or even in large USA stores.
I applaud your goal of building a useful Power Chair for your Mom. I don't know her circumstance but I don't think your clever build, and it is quite clever, would fill the need as I understand it.

[Alli]

I Designed these, initial versions were bolt on units for wheelchairs.
I now just build the chair sections to suit the end user...works out way cheaper and more easy to customize.

Parts (other than frame, subframe, forks, wheel guards)are off the shelf components
Front wheel = Electric Bike wheel (Double reduction Freewheel Planetary Drive, low speed 12km/hr on LiFEPO4, high torque)
Rear Wheels = Detachable Wheelchair wheels,
Standard bicyle parts for brakes, throttle, locking brake, basket.
Seat = Boat seat.

First version of how they are made now was using a rubbish kick scooter with welded up back section to hold wheels/seat/batteries.
As such they are hell cheap to build out of rubbish and lead acid batteries.

That's a really neat unit, but I don't think its very manoeuvrable especially indoors, which is mostly what my design is bard on, indoor electric wheelchair. But thank you, that is a different approach, nice idea

[Alli]

I agree with Burgerman. I'm impressed actually, that you have created a respectable complete SCOOTER. I AM a SCOOTER user. OUTDOORS. I can see your scooter design being useful for outdoor commuting but would be too large for in home or even in large USA stores.
I applaud your goal of building a useful Power Chair for your Mom. I don't know her circumstance but I don't think your clever build, and it is quite clever, would fill the need as I understand it.

Yes Mr Burgerman also had concerns, I appreciate the advice and feedback, could you tell me what do you feel I need to consider more? Or please explain to me why you feel it won't meet the need? Id appreciate the positive criticism and ill take it under advisement and use it to improve my idea and design.

[Alli]

Also can someone please advise me whether to use 12v 20A motors or 24V 10A motors? If I use the larger voltage motor that has lower current rating than the appropriate battery will beable to drive this motor longer than the lower voltage rated motor? If not what difference will it make because the power used by both will be the same? Please advise

[Burgerman]

You are a long way from understanding how everything works. I suggest we start at the beginning.

Describe what you want to do in detail, and why?

I might add that, any motor that takes 10 or 20 amps stalled will not work in a wheelchair. Unless its super light, and very low geared. And on the edge of burning out. Unless voltage is very high. (Watts = Power. Volts x Amps = watts.)

http://www.wheelchairdriver.com/gopro/motoramps.mp4 Just to get an idea. This is ONE motor on 24V with an accurate clamp DC ammeter.


Yes its TALLER GEARED (6MPH/10KPH)
Yes its HEAVY because its got me, and two 70Ah lead batteries on board.
Yes its programmed to turn when I tell it.

It does however show that the motors pull well over 100A EACH (only one is shown) when I turn.

A DC motor with adequate torque, will take more than 100A stalled while steering one wheel against the other (tank steer). Its THIS that makes powerchairs far less efficient than scooters.

[flagman1776]

If your Mom needs a wheel chair in the home... Wheel chairs are compact & can turn in place.
A scooter could not even turn around in most homes & can't get close enough to counters or into bathrooms. I own a TravelScoot https://www.youtube.com/watch?v=wFmlBKBLXq0
But it would be of no practical use IN my house.
That is what we are trying to tell you.

[Burgerman]

He is trying to motorise a manual powerchair.

[Alli]

You are a long way from understanding how everything works. I suggest we start at the beginning.

Describe what you want to do in detail, and why?

I might add that, any motor that takes 10 or 20 amps stalled will not work in a wheelchair. Unless its super light, and very low geared. And on the edge of burning out. Unless voltage is very high. (Watts = Power. Volts x Amps = watts.)

http://www.wheelchairdriver.com/gopro/motoramps.mp4 Just to get an idea. This is ONE motor on 24V with an accurate clamp DC ammeter.


Yes its TALLER GEARED (6MPH/10KPH)
Yes its HEAVY because its got me, and two 70Ah lead batteries on board.
Yes its programmed to turn when I tell it.

It does however show that the motors pull well over 100A EACH (only one is shown) when I turn.

A DC motor with adequate torque, will take more than 100A stalled while steering one wheel against the other (tank steer). Its THIS that makes powerchairs far less efficient than scooters.

Thank you Mr Burgerman, I really appreciate it. Okay let me tell you specifically what I want to do ill need some time. Also I wanted to know you said when you ate in the wheelchair the one motor it draws 100A ?? And normal use?

[Alli]

If your Mom needs a wheel chair in the home... Wheel chairs are compact & can turn in place.
A scooter could not even turn around in most homes & can't get close enough to counters or into bathrooms. I own a TravelScoot https://www.youtube.com/watch?v=wFmlBKBLXq0
But it would be of no practical use IN my house.
That is what we are trying to tell you.

Sorry Mr flagman, I think you confused me with someone else my Concept is not the scooter, its the manual to electric wheel chair.

[Burgerman]

Also I wanted to know you said when you ate in the wheelchair the one motor it draws 100A ?? And normal use?

That's is normal use. That's what it takes, 100A per motor, (200 total) to turn.

A manual chair and your mother may be lighter and take less. Maybe 50A each motor.

[gcebiker]

Please re read my post. First versions were indeed bolt on/removals power units for wheelchairs. I believe many examples iof such powered add ons are avaulable. .. but this is of topic for this thread.

[Burgerman]

I believe many examples iof such powered add ons are avaulable. .. but this is of topic for this thread.

True. But all hopeless outdoors, with harsh ride, tiny casters getting jammed, longer and wider than a real powerchair, unless just used in a portable, temporary, not very controlled short range low power sort of way.

Theres a good reason that proper powerchairs that are born that way, have big 70Ah batteries, 100A controllers, powerful motors, fatter tyres, complex programming, etc for true outdoor capability.

[ex-Gooserider]

Can I suggest that it might be worth SPLITTING UP this thread? There are 3 or 4 different projects being discussed here, and it seems like several of us are getting confused about which messages go with which project, and that is leading to even more confused messages...

On some other boards that I've been on, we tried to encourage a "One Thread / One Project" pattern, where any given project that someone was working on got a single thread started on it, and everyone was encouraged to keep all messages related to that project in the thread, even if that meant bring it 'back from the dead' every few months as progress was made.... Anyone wanting to start another project was encouraged to start a separate thread...

It didn't work perfectly, and topics still drifted and so on, but it did help to minimize confusion, and made it easy to go back and look at a given projects history start to finish....

ART

[ex-Gooserider]

This gets long, so keeping it condensed a bit by leaving the quotes at the end....

The charge plugs and the data cable plugs are VERY different, with different wiring and protocols as I said... The battery + and - wires are the ONLY ones that are shared.... The 'charge inhibit' wire is NEVER shared on any controller that I've seen, and there is NO reason for it to be, and it would be a total waste of wire if it were....

The power base, as designed, is NOT 'inhibited' from moving by anything - it simply CAN'T move unless it gets a signal that tells it to move.... It is just like your car, which doesn't need a "driver not present" switch to 'inhibit' it from moving, it simply can't move (unless broken) unless there is a driver there to provide control inputs.... Thus there is no need for an 'inhibit signal' of any sort to be sent to the power base - all that is needed is an inhibit signal internal to the joystick pod to tell it not to send movement commands to the base (and turn on the 'charge inhibit error' signal)

There is also no need for an explicit inhibit for faults in the joystick - controller wiring, as the system essentially will automatically inhibit by default UNLESS the wiring is OK and all the signals are getting through properly... Essentially the default action for anything to do with a chair is to shut down, unless everything is perfectly working to tell it to operate....

However there is nothing that says the micro in the joystick pod can't send a DATA signal, using the same wires and protocols as all the other data signals, that says "I'm in charge inhibit mode" and for the motor controller to then do an extra lockout in response - I don't really know if it does this or not, and don't see it as terribly important other than as a possible 'message' content....

Note that while there may be connectors for both external and on-board chargers, their inhibits will NOT be sharing the same wire, as the inhibit signal works in the OPPOSITE way - the external charger inhibit is normally high, and gets pulled to ground when the charger is plugged in, while the on-board chargers are normally wired to have the inhibit pin be normally low, and pull it HIGH when the on board is connected to the mains... In many cases the on-board often does connect to the controller in the power base, and it then acts as a sort of pass through, where the micro in the controller sends a signal to the micro in the joystick pod that it is seeing an inhibit - which again keeps it from sending motion controls back down to the controller, and tells it to turn on the charge inhibit lights...

The 'all in one' controllers are really no different in their function and operation than the multi-part units, except that the electronics for both units are crammed into the same case, and they get rid of the data cable between them - I'm not sure, but they may also get rid of one of the micros and do everything off of one, since they don't need to worry about data connections....

ex-Gooserider

Two different plugs, with different wiring and protocols...

maybe and maybe not. The batteries are down in the power base yet the charge plug is up in the joystick controller. What that means is that 2 battery wires(V+/GND) must be in the bundle of wires coming up from the power base to the joystick controller. Those are pretty easy to figure out so now we know what 2 of those pins are in the joystick to power base cable. The 3rd pin in the charger connector is the inihibit/programmer signals for the Jazzy VR2/GC2 type controller based power chairs. The Jazzy 600 has a VR2 based controller. Because the Inhibit line operates to inhibit the power base from moving there's a good chance not only is the 3rd pin in the charge connector the Inhibit signal but also there is an Inhibit signal wire going down to the power base. If this is the case, ie using a DMM to ohm out the charge connectors Inhibit pin to a pin on the joystick cable to the power base, then we would now know what 3 of the wires are coming from the power base up to the joystick controller. On the GC2 controller I found in the Jazzy Select it had a connector next to the joystick pigtail and I found a page which listed that as an aux charge port with INH/PROG pin for an onboard charger. It had 3 pins and one was Inhibit so I checked and verified the V+/Batt+ and GND wires in the joystick controller cable and then found that the Inhibit pin on the Aux Charger connector also was connected to a pin/wire in the joystick cable. That INH wire in the joystick controller cable was indeed connected to the charge port on the joystick controller.

I've seen that some chairs have the controller and joystick all in a huge box mounted on the armrest but the Jazzy Select and Jazzy 600 are not that type. These power chairs have a controller mounted in the base and a smaller joystick controller( with a charge port ) on the armrest.

So are you saying that the Inhibit line from the charge port on the joystick controller does not ohm out as having a direct connection to one of the wires in the joystick cable doing down to the power base?

There is the three wire (on most controllers) XLR charging plug - the wires on this are +V and Gnd, with the third wire serving as EITHER an inhibit wire (shorted to ground by the plug on the charger which has the two pins wired together) OR a programming wire that uses some sort of one wire serial data protocol, via either a dongle or a converter that does some serial data conversion between the usual PC TX/RX + handshake signals, and the one wire setup.... (Some controllers have an oddball setup with a proprietary version of the XLR plug that adds more extra, tiny, pins that are used only in programming, and are ignored in charging.

Then there is the connector / cable between the joystick pod and the rest of the chair electronics (controller, ALM modules, etc...) This will have a variable number of wires. At least two that are usually bigger than the others and carry the charging current from the XLR plug on the pod to the power module where they feed into the battery cables. Then there will be some additional wires (often very small, as they are only for data signals, which carry data, including joystick commands, information about button pushes, inhibit signals, etc.... The number of wires, protocols and so on will vary depending on the controller brand / family.... It is reverse engineering this set of wires, protocols, and messages that pose the big challenge when trying to hack into the chair electronics....

The inhibit / programming wire and signals on the XLR plug has NOTHING to do with the wire and signals on the cable to the rest of the system. The inhibit / programming wire goes ONLY to the board in the joystick module. The electronics in the pod take whatever comes into it from the XLR plug, and does some processing on it, including translating it to the protocol used to talk to the rest of the chair and sends out whatever it needs to.... The exact details of what gets sent is again variable depending on the controller type.... For instance some controller systems store the programming data in the joystick pod, and others in the power module....

The charger inhibit signal is actually one that doesn't NEED to be sent to the rest of the chair - if the joystick pod sees it, then all it needs to do is flash that controllers error code, and simply NOT send any other signals to the rest of the chair....

I found it was differently on the Jazzy Select having a GC2 controller in the base and a joystick controller w/charge connector on the armrest. The Inhibit signal could be handled by the micro controller in the joystick as you mentioned but since the "PROGRAMMING" portion of the INH/PROG pin in the charge port is for programming the controller in the power base then it makes sense they would connect that wire all the way through the joystick controller down to the power base. Again, as I saw them do it in the Jazzy Select. But it is possible they have implemented some other form of communications with the power base controller using the joystick controller as a form of intermediate control module. It's a bit dangerous though since any fault in the joystick system would prevent an Inhibit signal getting to the power base and locking out any change of the wheels moving.

I would just like to hear it be say that the Inhibit line( on the charge connector in the joystick ) with all other(skip known V+/GND wires) wires coming from the joystick controller to the power base were ohmed out and only the Battery wires are in common between the joystick controller cable and the charge port on the joystick controller.

Doug

ex-Gooserider

can you remind me how it was determined the protocol was SPI? From a previous post there are only 4 wires going from the power base to the joystick control board and 2 of those are power(V+/GND) and 2 wires are signal(Y/V).

Also, there is a 3 pin charge connector on the joystick and one of those is the Inhibit/Prog pin and I found that pin was a direct circuit(and wire) down to the power Rob@ with the subject line I want better communication from robbase. So that left a 1 wire signaling protocol and UART made the most sense so it was the first tried and it turned out to be true.

This is why I ask how it was determined the protocol was SPI which is a 2 wire protocol(1=data, 2=clock)?

Remember, the Inhibit line is a safety feature of most all power chairs as it prevents the chair from being moved in any way when plugged into the charger.

Doug

[ex-Gooserider]

Also can someone please advise me whether to use 12v 20A motors or 24V 10A motors? If I use the larger voltage motor that has lower current rating than the appropriate battery will beable to drive this motor longer than the lower voltage rated motor? If not what difference will it make because the power used by both will be the same? Please advise

Alli, looking at the questions you have been asking, I think that you are FAR from sufficiently knowledgeable to do a 'from scratch' build at this point... Given that what you are wanting to do is motorizing your mothers existing chair, I'd suggest looking at that kit from Golden Motors that was mentioned earlier in this thread... From what I understand of their description it is essentially a 'bolt-on' solution with hub-motors that replace the existing wheels on the chair, and a controller, so you have a setup where all the parts are matching and will work together... It would also be easy to remove if for any reason you want to go back to the lighter weight all manual solution....

This is FAR from the great chairs that Burgerman likes, but it is adequate for light duty use around a house or shopping mall.

Another concern I have is your mother's safety - when you are putting a person in a motorized chair or scooter, things MUST work properly, or otherwise one can get seriously hurt... To do a 'home-built' chair safely requires that you have a really good understanding of how all the parts fit together and interact - otherwise you are an accident waiting to happen....

So what I'd suggest is that you start with a reasonably complete kit like the Golden Motors unit, which will teach you a lot about the basics of how this stuff works, and let you get your mother under power, while you continue to develop your understanding and knowledge until you reach the point where you are ready to start doing a from scratch build....

[Alli]

Also I wanted to know you said when you ate in the wheelchair the one motor it draws 100A ?? And normal use?

That's is normal use. That's what it takes, 100A per motor, (200 total) to turn.

A manual chair and your mother may be lighter and take less. Maybe 50A each motor.

Thank you for indulging my questions and being patient with my ignorance Mr Heffernan. And thank you everyone for your input and assistance. I must say I do feel bit despondent now, I was really keen and maybe a little desperate to do it in my own, but I guess I'm too naive still. But I won't give up. Thank you for giving me a start though. Hope everyone else is having better luck with their projects.
Also Mr Burgerman, its a really nice thing you doing advising and educating people to improve their lives with your site and blog and id like to commend you on it.it. I did learn alot and it was nice to beable to ask someone for help on this blog. And thank you to all the good samaritans who also give their input to help others like me.
Hope to contact yourll soon after learning bit more. Thank again