help troubleshooting?

[stepfen]

Hello,
The right hand wheel of my sister's wheelchair (VR2) has stopped moving backwards.
Is there an "easy" way to troubleshoot and locate and/or fix the problem?

The left hand side works fine (forward and back). The right hand side wheel moves forward as normal, but won't turn backwards at all.
Any ideas?

I am an electronic engineer but I haven't got any hands on experience on the chair, other than changing/tuning some of the parameters (turning speeds etc) for her when she bought it.

Thanks a lot,
Manos

[Burgerman]

Probably a cush drive or gearbox issue. Maybe a motor brush problem. It will need some careful examination to figure out. If so then ebay a motor or order new $$$££££...

May be easier to check with wheels off the ground.

[martin007]

Do you hear any abnormal sounds?

[tettralytic]

A fault on one of the "H" bridge switches (transistors) would explain your symptoms. To diagnose you could change over left and right motors at the p.m. If the fault moves that would further indicate. Unfortunately they are inside the p.m.

[stepfen]

Thanks for all the replies.
There are no abnormal sounds.
I need to find time to experiment with this...
Thanks a million.

[martin007]

Keep us informed of the progress.

[FelipeOliveira]

Reversing the engines probably won't help in this case. The VR2 would indicate an error code and would not allow the left one to move
Since you can move your left hand normally, the fault is probably mechanical.
Gearbox, electromagnetic brake very dirty.

What is the model of the powerchair?

[ex-Gooserider]

I'd disagree w/ Felipe, if you swap the two motor plugs the controller will not have any way to tell, although the chair will probably drive very strangely (Do this with the wheels off the ground)

Swap the two motor connectors, plugging both in...

If the problem changes sides, it's a bad controller. If the problem stays with the same motor it's the motor....

ex-Gooserider

[FelipeOliveira]

I'd disagree w/ Felipe, if you swap the two motor plugs the controller will not have any way to tell, although the chair will probably drive very strangely (Do this with the wheels off the ground)

Swap the two motor connectors, plugging both in...

If the problem changes sides, it's a bad controller. If the problem stays with the same motor it's the motor....

ex-Gooserider

Yes, I agree that this procedure, however, would only confirm what is already certain. but in my opinion, a failure in the controller would be the last possibility, as it can still move the left and right sides perfectly, just forwards..
It is very likely that the problem will continue exactly as it is on the same side.
Correcting what I said previously… I was wrong about the electromagnetic brake. But I remain suspicious of a MECHANICAL failure (gearbox). And it would reinforce BURGERMAN's opinion. The most likely cause is BRUSHES with deformed springs.

Let's wait for Stepfen to update the current situation

[ex-Gooserider]

I'd disagree w/ Felipe, if you swap the two motor plugs the controller will not have any way to tell, although the chair will probably drive very strangely (Do this with the wheels off the ground)

Swap the two motor connectors, plugging both in...

If the problem changes sides, it's a bad controller. If the problem stays with the same motor it's the motor....

ex-Gooserider

Yes, I agree that this procedure, however, would only confirm what is already certain. but in my opinion, a failure in the controller would be the last possibility, as it can still move the left and right sides perfectly, just forwards..
It is very likely that the problem will continue exactly as it is on the same side.
Correcting what I said previously… I was wrong about the electromagnetic brake. But I remain suspicious of a MECHANICAL failure (gearbox). And it would reinforce BURGERMAN's opinion. The most likely cause is BRUSHES with deformed springs.

Let's wait for Stepfen to update the current situation

I agree we need a situation update, but my reading was that Stepfen was still trying to figure out if it was a motor or controller problem, and the motor swap problem is the easiest way to determine that....

I'd agree that it's more likely a mechanical problem w/ the motor, but it is still possible that it's a controller issue - most are using an "H-Bridge" and if one of the four FETs in the bridge fails open , you'd get rotation in only one direction... Not to mention any odd failures in the control circuits going to the bridge...

ex-Gooserider

[Burgerman]

and if one of the four FETs in the bridge fails open , you'd get rotation in only one direction...

No you get a error and a number and do not move. Ask me how I know.

[FelipeOliveira]

and if one of the four FETs in the bridge fails open , you'd get rotation in only one direction...

No you get a error and a number and do not move. Ask me how I know.

Exactly !! And I still agree with you. BM….

Gearbox or brushes

But unfortunately, many do not provide feedback and it seems unlikely that Stepfen will either.

[stepfen]

Sorry for the delay guys.
It turned out that the wheelchair was under warranty (in fact last week or so out of the 2 years period!!) hence it was repaired by the shop and I didn't have chance to investigate further.
All I know is that it was fixed by replacing the whole motor assembly. They didn't give me the broken part so I can't know more. Most probably there was something wrong with the gearbox.

Out of curiosity and for future reference, is it possible to buy somewhere online these parts (preferably a European shop - not uk to avoid dealing with customs etc)???
I'm attaching a photo of the motor label. The company doesn't seem to have this particular type in their web site and I can't find it anywhere else.

To be honest my sister is kind of abusing the chair as she can't have good control of it. Also the chair has very thick front wheels/tires hence some times it struggles to turn on the spot. As a result it gets stuck occasionally next to obstacles etc and I am afraid it is a matter of time that this will happen again.

Thanks for all the help.

[Burgerman]

Out of curiosity and for future reference, is it possible to buy somewhere online these parts (preferably a European shop - not uk to avoid dealing with customs etc)???
I'm attaching a photo of the motor label. The company doesn't seem to have this particular type in their web site and I can't find it anywhere else.

To be honest my sister is kind of abusing the chair as she can't have good control of it. Also the chair has very thick front wheels/tires hence some times it struggles to turn on the spot. As a result it gets stuck occasionally next to obstacles etc and I am afraid it is a matter of time that this will happen again.

Motors are generally sold as complete motor/gearbox and brake units. Sometimes brushes are available seperately.
Struggling to turn on the spot and struggling to control is usually caused by 4 things. You will need to address all 4 to make the thing work properly.

1. It will have weedy 2 pole motors that are too small and lack enough torque for the job. This is very common.
2. It will have a control system that cannot provide adequate amps when its needed for e.g to turn in place and so the motors stall.
3. if rear drive it will have way too much mass over the front casters and so makes it even worse. Needs seat movng back and a centre footplate.
4. In programming it probably needs the motor compensation increasing a touch, and all the turn delay removing by setting all 4 turn acceleration parameters up from the typical low 30 to 40 to 100. This means turn acceleration, turn deceleration, minimum turn acceleration and finally minimum turn deceleration.

[stepfen]

Motors are generally sold as complete motor/gearbox and brake units. Sometimes brushes are available seperately.
Struggling to turn on the spot and struggling to control is usually caused by 4 things. You will need to address all 4 to make the thing work properly.

1. It will have weedy 2 pole motors that are too small and lack enough torque for the job. This is very common.
2. It will have a control system that cannot provide adequate amps when its needed for e.g to turn in place and so the motors stall.
3. if rear drive it will have way too much mass over the front casters and so makes it even worse. Needs seat movng back and a centre footplate.
4. In programming it probably needs the motor compensation increasing a touch, and all the turn delay removing by setting all 4 turn acceleration parameters up from the typical low 30 to 40 to 100. This means turn acceleration, turn deceleration, minimum turn acceleration and finally minimum turn deceleration.

All 4 are possible. I think No3 is probably the most important as the front wheels seem to carry a lot of weight - I will have a look for seat adjustment. No 1 and 2 are quire probable too, but too difficult to solve for now.
As for No4 I myself tuned the control unit when we bought it (it was horribly tuned out of the box) following some suggestions and a guide fount here. It is 2 years ago so I can't remember details but I think I have done these adjustments.

Can anyone be more specific on where I could buy eg this particular motor unit? Google doesn't find the type code at all!

Cheers

[Burgerman]

Motors for powerchairs are normally ordered in batches with the specific motor spec, wind, no of poles, brake voltages, gear ratios and connecting cable lengths and connectors all agreed. So unless you plan to buy a pallet of them its unlikely a manufacturer of motors will sell you one. You need to buy from whowever made the powerchair, and the via a high street or online dealer.

[stepfen]

Motors for powerchairs are normally ordered in batches with the specific motor spec, wind, no of poles, brake voltages, gear ratios and connecting cable lengths and connectors all agreed. So unless you plan to buy a pallet of them its unlikely a manufacturer of motors will sell you one. You need to buy from whowever made the powerchair, and the via a high street or online dealer.

I was hopping that there would be online shops/dealers who sell this kind of motors.

[Burgerman]

One or two generic ones can be bought from robotics suppliers. They are unlikely to be correct in every way. Different sized motor output shaft, different mountings, different impedances, different cables, brakes and connectors etc. But theres no shop. It would be almost impossible considering the sheer amount of possible options, motors or chairs.

What exactly is your chair?
I can order a set of motors that fit my newest two powerchairs by quoting part numbers taken from sunrise medicals online parts website. I can order from any sunrise dealer on the high street or online. Same with all the rest of the chairs parts. But you cannot order seperate motor parts of sub assemblies. That wouldnt be viable. So you can order full motor assemblies, wheels, bearings, actuators, joysticks or power modules or other parts etc. But its usually far cheaper to order these parts from eBay etc.

Motors for my chairs are actually Linix motors in china. These are also used by other chair manufacturers. Such as permobil. But theres around 15 different part numbers for the sunrise supplied ones alone. All are not directly interchangable as they are different electrically, gearing, 2 and 4 pole, cable lengths, etc. And they dont even look the same as the permobil versions as these use a different gearbox style mountings. As I say companies such as linix who actually make these motors make large batches as specfied for each different chair or speed to a specific set of parameters. If its not a mainstream powerhair and a cheap chinesium one, you might find similar generic motors on aliexpress etc. But the devil is in the details.

So they wont be interested in supplying a specific order to tailered to suit a single retail customer in a forein country as a one off. They know nothing about powrchairs, only motors. Lets say you have a BMW car. And want a brake master cylinder. Or a speedometer. Or a fuel injector. Or alternator. BMW dont make many parts they buy them in and these are manufactured for them by various external companies that specialise in these things. But not only for BMW. You couldnt go direct to the company that supplied these parts to BMW and expect them to supply a single customer. Their contract for that part is with BMW. They are set up to deal with business to business. Not retail customers and they wouldnt know what part or what details you wanted anyway. They may in fact not even know what that part is fitted to at all.

[ex-Gooserider]

BM prefers to get new motors, but a lot of us get used motors from eBay or similar... However you will probably NOT find the motor by the numbers on the labels... The following will be helpful...
1. ID your chair, and find the parts list for it...
2. Find the manufacturer part numbers, for BOTH motors
3. Get a good idea of what the motor looks like - how it mounts, and so on...
4. Try to identify as many other chairs from the same manufacturer use the same motors

If you are lucky a motor listing will be for a pair of motors (I tend think one motor listings are suspect - if one of a pair has failed, I wonder what kind of abuse the one for sale has suffered) w/ manufacturer's part number... More typically the listing will be just saying what chair they came off...

Often this won't be accurate, so look carefully and be sure the photos match what you expect the motor to look like... While a lot of sellers will try to polish up things, it is good to look closely at the photos and see if they seem to show wear consistent w/ descriptions...

ex-Gooserider