Hoss Mobility - Segway style chair

[Burgerman]

Well segways are unusable, and this is $$$$$$$$$

[StephensonVoice]

Dear Burgerman,

You have already gently corrected me a couple of times, and this may be the next opportunity.

Having watched some videos on the Omeo and similar, I was thinking of building a self-balancing chair that would handle my weight. Your remark above seems pretty dogmatic. I recognize that you have certainly earned the right to be dogmatic, of course, on top of this being your sandbox.

But - I would greatly appreciate it if you would tell me WHY a self-balancer would be a bad idea.

Thanks!

-Tim
https://youtu.be/U-RH4p-V4vg?t=63
https://youtu.be/0VBd8mlFfGM?t=55

[StephensonVoice]

I am worried that I might be misunderstood in my comment, above. It made sense to me when I typed it, but on rereading it after some hours it seems off somehow.

I have the greatest respect for Burgerman, and am perfectly happy to read how he reacts to this or that and internalize his opinion as my own: he's clearly shown himself to have done absolutely heroic work in studying and experimentation (I'm 20 pages into his Roboteq thread so far, for example). And his sharing of his experience with us all is astonishingly generous. So I'm guessing there are darned good reasons behind every one of his opinions!

I hold my opinions strongly, too. But I confess that mine are often based on incomplete information or wishful thinking. I am hoping that he will share some of his reasoning behind the "Segways are unusable" remark, so I can bury my desire for one with a pile of good reasons. I can, of course, bury my desire for one just on his say-so, but it would be cool to know why.

Thanks, Burgerman!

-Tim

[Burgerman]

Segways?
I think you didnt read the complete thread.

In order to go forwards you need to lean your upper body forwards. And to go back or slow down you need to do the opposite. If you can do this great. If you cant and I cant, not so great. Hence the joystick mod.

T4 paraplegic here. Not just hard of walking. Means that I have no trunk or other control. No movement below nipples. So the whole idea of any control on a machine that depends on weight shift for forwards, backwards (or emergency stop especially) is a non starter. Moving your HEAD alone is simply not enough!

It COULD be made to work by intergating a joystick for forwards and backwards movement. But I have looked at the segways and decided that this was rather hard to do. Which is why non of them offer this.

This applies to all tetraplegic/paraplegics, and many other users. If you are what I call walking wounded or a scooter user and have normal trunk control then they work. But for many here they dont.

[700R]

I have tried the Omeo and although liked the top speed element I never felt I would be capable of exploring it much further than flat surfaces as I am 6'6" tall and a tetraplegic. We modded it as best we could on the day for me to sit in it without falling forwards but, in that there follows a compromise in seat directional sensitivity. There is a sweet spot which isn't really adjustable which isn't a problem for shorter, more able bodied individuals with core strength.

For me, I felt it was a risk that given the way I ride my chairs, was going to end in a painful episode if I tried to replicate that. To make the Omeo fit my long legs the seat was lifted but that made transferring nigh on impossible and something I wouldn't do regularly. Using the joystick for directional changes was simple although I could also manoeuvre it with my body but again should I catch something on the ground unexpected I think I'd be visiting the floor. Being 'perched' on top of a moving object without anything protecting body movement from easily leaving the seat never felt great but was certainly worth a try. If prices weren't daft I might consider one for a straight, flat, fast pub run but then just like powerchairs, they need to be bought at silly low prices to justify ownership for me.

Just to add, they are also quite sensitive to power shutdowns which aren't then suited to paralysed individuals. They also tip over going down steepish, damp grassy banks due to leaning back to brake and the tyres slip. My powerchairs would manage the same example without drama.

Great bit of kit but suited for individuals that can walk a little, or shorter paralysed individuals not so bothered about putting it through its paces and accepting of its occasional shutdowns and high cost.

[StephensonVoice]

Yeah, I can certainly see how they would be a complete nonstarter for spinal injury folks. My big problem is fatigue/weakness/pain on standing or walking for any length of time. I'm just waaay stinking overweight. I am expecting that in a few years, I might need a chair, and I needed one on a week-long trip we took to Yosemite National Park. There I used a recumbent trike to get the quarter mile from car to cabin and to the various sites. It barely worked and I doubt it will work in a couple of years. But only the 600 lb chairs will carry me, and they're all too big for my home and much too expensive to consider. Being handy I was thinking of building a stout self-balancer for the overall smaller footprint and considering that I've got the ability to move and to climb on and off it. Rotten choice for many - still considering it for myself. Burgerman and 700R, thanks for your thoughtful and extensive replies.

[StephensonVoice]

(And I *did* read the entire thread - several times. I just wasn't sure if there might be some other fatal flaw with self-balancers.)

[700R]

(And I *did* read the entire thread - several times. I just wasn't sure if there might be some other fatal flaw with self-balancers.)

On a cliff-top and leaning forward to scratch your shin could be deemed a fatal flaw.

[StephensonVoice]

I'll grant you that...

[Burgerman]

Balancers are actually good for power saving as turns in place are almost "free" compared to tank steer with casters. Same when correcting direction while traveling. Having tested the original iBot 3000 and the later "better" iBot 4000 I can say I like balance. Although its not foolproof and I managed to get it to crash several times! Caught by the rep, during evaluation.

[StephensonVoice]

I will post photos; I will also wear a helmet if the project gets far enough to sit on it. Or hire a younger and faster-healing test pilot. And make HIM wear a helmet.

[Burgerman]

I asked David Coates of independence technology europe while testing the pre production prototype IBOT 3000 at my house: What will it do in a train, in balance mode? While leaving the station? Or on a curve? He looked at me and looked puzzled. "I dont know. Dont try that."

I didnt. But managed to get it to freak out and try to fall down anyway!

There are always things that the designer of these things didnt think of. Balance machines can do very surprising and unexpected things fast! And they have by nesessity a lot of torque/power. Esp if the ground moves or a wheel slips on a wet/greasy/oily/icy/mulched up leaves in winter, etc. Or when a wall or some "trip" hazard or threshold or "dip/hole cannot be overcome.

[StephensonVoice]

Along those lines, I was curious about how a self-balancer might behave with thresholds along the lines of the standard chair programming heroics to up the power and then knock it down right away so you don't race to the far wall in the next room. I would think that one might need to lean a bit farther forward to get the power needed to get over the threshold, and then hopefully the self-balancer would zip up under you quickly enough to keep you off the far wall. Or might that require quick reflexes on my part (you know, like the 'quickly back off on the joystick' one would have to do with a standard chair)? Thoughts?

Probably I would best correspond with the guy(s) who did the programming I will be incorporating in the rig, to see how they've dealt with this. Oboy. A new version of the 119 page Rpbpteq thread to read!

[Burgerman]

I would think that one might need to lean a bit farther forward to get the power needed to get over the threshold, and then hopefully the self-balancer would zip up under you quickly enough to keep you off the far wall. Or might that require quick reflexes on my part (you know, like the 'quickly back off on the joystick' one would have to do with a standard chair)? Thoughts?

No... On a normal chair.
This is the whole point of motor load compensation. It means that even a tiny command of maybe 5% pulswidth to move a wheel or start a turn at the joystick input is ramped up to whetever power is required AT THE WHEEL to overcome the resistance of a threshold or extra current required to turn etc. YOU shouldnt need to. It backs off just as fast. So it isnt really noticed by a user. Because if this didnt happen then the chair would behave really badly. As it it just wouldnt move at all when set to low speeds. And would overshoot madly after you got it to climb a threshold. Compensation effectively adds torque when required ONLY. It does this with every command, every movement inc when slowing.

So your chair adds NEGATIVE current to a motor as you descend a ramp while going forwards. Even though you are applying a forward stick command to move forwards. So it descends the ramp at the same speed as it will climb it. Without compensation you would need REVERSE stick to descend a ramp slowly! To stop it running away on its own.

It can add more power to one wheel while adding negative power to the other to make your chair go in a straight line along the edge of a cambered road. A lateral slope. The rate that the motor compensation works at is faster than the rate of turn or forward/reverse acceleration you have programmed in. It just fixes everything. It makes a motor behave as if it has zero resistance. Up to the point where the typical 120A controller runs out of steam.

But unlike pure digital systems with encoders, or brushless motor systems, or even gyro systems it doesent remove all feel or feedback. So control feels very intuitive. Providing your chair is CORRECTLY programmed and configured. But seriously non of them are close! Thats why a little knowledge and a OEM programmer is essential or a powerchair is dead to me. I wouldnt even consider one that doesent allow this.

[ex-Gooserider]

I have never tried one of the self balancer chairs, and would like to, but more out of curiosity than anything else...

At more or less T-5 level, I have SOME trunk control, but the further over I go the less reliable it gets, so I can easily reach a point where I need to either grab the chair or wave my arm to balance and get me back upright.... I'd be afraid of going to far over to recover reliably... Even if I had a joystick I'd still worry a bit about getting tipped in a hard turn which I'd expect would upset the balance...

A somewhat related datapoint... A couple years ago, I was working with my friend Erik Kondo on making a manual wheelchair accessible hoverboard (we won a first round prize in a Toyota Mobility design competition) One of the problems we found was that it was quite drivable on flat ground or uphills, but downhills were VERY problematic...

Erik would hop his chair up onto the board while holding a wheelie, and drive it by shifting slightly back and forth to tilt the board the way a TAB would do it by flexing his ankles...

The problem on downhills was that the weight shift needed to keep in balance and maintain the wheelie would also tilt the board forward, telling it to go faster, needing more tilt, in a positive feedback loop until bad things happened... In order to tilt the board backwards he would have had to lean forwards, and face plant as soon as the board slowed and he went forward over it... This is something that we were still trying to figure out, without much progress, when we got hit by a 'stealth patent' that effectively ended the project... (Given that I've yet to see a product, I suspect the stealth patent people hit the same problem)

ex-Gooserider

[StephensonVoice]

Hm. Will test with even more caution, then. Thanks for the warning.

All the parts are ordered, including HD 4-pole low-speed-gearbox motors from a 600 lb capacity Pride/Jazzy 1450, a 24v LiFePO4 battery bank, and a Hyperion 1420i-NET3 charger. I went with a Sabertooth 24v 2x60A controller for starters because the project I'm emulating used the Sabertooth 2x25A controller and the data feed side is the same. If I am unhappy with it I'll upgrade to the Roboteq - but then I'll have to reprogram it from a cold start and with this project it's all been done for me. Hopefully. And this was $500 cheaper. Will post progress if successful or when I get out of the hospital if not.

[Burgerman]

Hyperion?
I gave up on them because they became impossible to source were super unreliable and I managed t0 get the manufacturer of the PL8 to fix the things so thay properly charged large LiFePO4 and lead... I did the same with hyperion 6 or 7 years earlier. Including a BT conversion and countless firmware revisions.

Also their code on the controller may "work" but it will be a long way short of the real refinement needed for use as a powerchair. But you are just beginning this! And will learn all the issues as time goes on!

And I think at your weight you need more power for the extreme events that keep you upright. A wheelchair motor at stall would take around 350A if the current wasnt controlled by the pulsewidth allowed down to the 120A limit that we see in most powerchairs. I am not sure 60 will cut it. It will most of the time.

Lets say you stop at the bottom of a "threshold" like the entrance to my drive. The "threshold test" that I use when evaluating chairs. Its a small slope up to the block paving up the grey "curb" stones from the black tarmac footpath.

In a normal wheelchair, riding up that is trivial as long as you are already moving. You dont really notice it. Just a bump. However, if I drive the caster wheels up and stop when the drive wheels hit the grey stone. And then try to climb it with zero run up/momentum, the chair STALLS at 120A. And refuses to move... This is with 6mph 4 pole motors. And a 120A controller with a 20 stone user in a heavy 185KG powerchair. It literally refuses to climb this seemingly easy edge. In the case of a balancing chair that means it will *reverse* around an inch, to tilt you forwards, then try to go forwards and then stall... And you will fall forwards and do a faceplant.

The slope in question. Look at the grey concrete entrance between the geteway pillars and zoom in. 120A not enough from a standstill. I tested this exact same scenario as a "torque" test on a great many chairs. Only my lighter chairs without all the heavy seating stuff will do this without problem. But this is nothing compared to what you will come across in the real world. Now your moving momentum in a powerchair, even going slowly hides this lack of torque. So you see no problem. But the momentum effect wont be effective in a balancer. As your CG is above the contact patch and the chair will want to crash forwards instead. This caused the iBot a problem too. Its only a couple of inches total.

[Burgerman]

I found another easier to understand video. A different "curb"...

This is a very old rear drive chair. And an example of what happens if you use an 80A controller as fitted to this. Its an olde backup chair.
This is a 1.5 inch rounded curb. Initially I drive up the fronnt casters no problem then I stop when the drive wheels touch the curb. Then show what happens. It reaches its 80A and we go nowhere! This is what happens if the controller has inadequate Amps even on this very light chair with no rehab options. It has 80A 6mph motors.

80A here is not enough. At the end I reverse a few inches and then go forwards and its momentum causes it to climb this small curb without issue. But:
a) you shouldnt need momentum if the motor has enough torque. The same chair fitted with a 100A controller clims this curb without this problem.
b) in a balancer momentum still helps. But not as much. And when the wheel stalls you faceplant!

Watch carefully. An example of inadequate Amps. (80A controller).
(Note, if motor compensation set too low this also happens with a 100 or 120A controller!)

https://www.wheelchairdriver.com/gopro/lackofamps.mp4

[StephensonVoice]

Yeah, the probable lack of torque for my weight is indeed a concern.

Not asking you to agree with my decision-making, of course, but just to clarify why I chose these items:

• Hyperion Charger: you told me it was the best, on https://www.wheelchairdriver.com/hyperi ... harger.htm. Is there a new favorite? I might want to put this one back on eBay and aim for it.
• 60A x2 controller: my just-turned-74 wife will need a chair sooner or later - if for nothing else than zooming around Yosemite with me next time we go. So this chair, even if underpowered for me, will likely do quite well for her petite frame. And I'll learn a lot in the process. To be sure, the already-done self-balancer circuit and code and the $500 cheaper price were influences, too.

I will be starting another thread in a moment, asking, "Can I drop a Roboteq into a Sabertooth circuit to increase power?" and would love your thoughts.

[Burgerman]

That is a 15 year old webpage!
Last updated 13 years back.

Since then it became obsolete, and I managed to get the cellpro PL8v2 chargers updated in the same ways as the hyperions with suitability for us. Both lead and lithium.

Then that too became obsolete. Ceased production. Theres nothing really that matches it but the bigger iCharger models are what people now use in place of it. Albeit with a slight reliability concern and no decent charger configuration or control software.

There are some good PL8s still available from shirleyHK on another thread.

Drop in a Roboteq in place of the 60A sabertooth? Its a whole new level of capability and configuration and will need one of lennys new circuit boards ideally to simplify instalation. And his latest script etc. And a LOT ofunderstanding and configuration. But anythings ossible It wont be a drop in thing though. A start from scratch is more likely going to be easier. Or a start with roboteq makes more sense to me.

[700R]

Along those lines, I was curious about how a self-balancer might behave with thresholds along the lines of the standard chair programming heroics to up the power and then knock it down right away so you don't race to the far wall in the next room. I would think that one might need to lean a bit farther forward to get the power needed to get over the threshold, and then hopefully the self-balancer would zip up under you quickly enough to keep you off the far wall. Or might that require quick reflexes on my part (you know, like the 'quickly back off on the joystick' one would have to do with a standard chair)? Thoughts?

Probably I would best correspond with the guy(s) who did the programming I will be incorporating in the rig, to see how they've dealt with this. Oboy. A new version of the 119 page Rpbpteq thread to read!

Once you are seated correctly and practised a bit you really don't actually lean to any noticeable degree. Everything falls into place and it becomes very natural. It's only at first it feels like you need to dive forwards to propel it but it really isn't like that. Practice is key. Thresholds are fine with momentum and confidence and where possible crossing them diagonally can help. It will bite if hesitation is present and often go into a spin. All this however is a learning curve that fades into the distance with time in the seat.

[700R]

I have never tried one of the self balancer chairs, and would like to, but more out of curiosity than anything else...

At more or less T-5 level, I have SOME trunk control, but the further over I go the less reliable it gets, so I can easily reach a point where I need to either grab the chair or wave my arm to balance and get me back upright.... I'd be afraid of going to far over to recover reliably... Even if I had a joystick I'd still worry a bit about getting tipped in a hard turn which I'd expect would upset the balance...

A somewhat related datapoint... A couple years ago, I was working with my friend Erik Kondo on making a manual wheelchair accessible hoverboard (we won a first round prize in a Toyota Mobility design competition) One of the problems we found was that it was quite drivable on flat ground or uphills, but downhills were VERY problematic...

Erik would hop his chair up onto the board while holding a wheelie, and drive it by shifting slightly back and forth to tilt the board the way a TAB would do it by flexing his ankles...

The problem on downhills was that the weight shift needed to keep in balance and maintain the wheelie would also tilt the board forward, telling it to go faster, needing more tilt, in a positive feedback loop until bad things happened... In order to tilt the board backwards he would have had to lean forwards, and face plant as soon as the board slowed and he went forward over it... This is something that we were still trying to figure out, without much progress, when we got hit by a 'stealth patent' that effectively ended the project... (Given that I've yet to see a product, I suspect the stealth patent people hit the same problem)

ex-Gooserider

You'd manage the Omeo easily and downhill use is a breeze. I really enjoyed going flat out and leaning back with some force to stop the machine. The reclined position is comfortably, probably the best part of it. Down a hill it's simply a case of controlling speed by leaning back the desired amount and only poses a problem on a wet, grassy bank for instance where it would lose traction and drop you off the back.

[Burgerman]

I am not so sure. YOU may be able to. I wouldnt even be able to remain sat in it without a highr back and some proper arms!

I would fall out sideways just sat still. And all the movements I see people making in every video are completely impossible for me.
I think exgoos is very similar - maybe more mobile as T5..

[Burgerman]

I did enjoy the balance mode on the iBot 3000 and 4000 chairs during the couple of days with each of them here. Because of the joystick giving precise control. A far better way to steer and to drive any balancing chair than weightshift. Even if I could do that control with weightshift its simply messier, unessassary and less accurate. The Joystick control is an essential need and want on any balancing chair I would wish to use.

However the iBots (both versions) had some serious issues...
For a start in every mode other than balance, they were terribly compromised chairs that performed dismally. (I wont go into detail here unless you want! Its not what the thread is about)

And unless I could have gotten hold of whatever they used as OEM level programing tools, then I wouldnt touch one with yours. They drove terribly and were horrid to drive and could barely hit a doorway. And they got worse with speed. As a daily chair they were hopeless because of this even in balance mode. Still balance was fun.

[ex-Gooserider]

I am not so sure. YOU may be able to. I wouldnt even be able to remain sat in it without a highr back and some proper arms!

I would fall out sideways just sat still. And all the movements I see people making in every video are completely impossible for me.
I think exgoos is very similar - maybe more mobile as T5..

The neurology people tell me I'm at T-5 for function, but I've had a few other SCI folks with nominally similar levels tell me I can do more than they can in terms of bending over and straightening back up...

A couple data points - I can bend over, pick up something off the floor with one hand, and straighten back up just using the other arm for balance (but it's easier if I use it to pull up on the chair frame) but I can't pick up even a very light object if I need both hands to grab it. (like a box)... If I put a strap under the box so I can haul it up w/o bending over I don't have any problem staying upright.

When driving (I'm in the US so drive on the correct (right) side of the road), I have problems staying straight upright when taking an exit ramp at 15-20 MPH faster than the 'suggested' speed for it, but no problem if I lean over to the left so that my shoulder is against the door pillar...

ex-Gooserider

[Burgerman]

I am T3/T4 complete and cannot do any of what you describe. You sound like T5/T6 incomplete?

Quite apart from this. A joystick offers accurate easy mm perfect positioning. At least once the hovercraft programming has been removed! Weight shift cannot be that accurate no matter what you do. Its clumsy and hard work in comparison. Imagine trying to use your PC mouse to hit a tiny button or highlight a text letter or word for e.g by shifting your body weight! Its just not good enough for accurate positional control.

[StephensonVoice]

Hm. Very good point.

[Burgerman]

The iBot balancer in the picture above cound be manoevred for and aft in the same way as a segway or any other balancer. But it DID have a joystick. And was hugely more accurate using that. But like all balancers it isnt that accurate in a fore/aft sense whatever you do.

It did however also have the same exact issue as every last powerchair I ever tested. And that is probably 7 or 8 brands or so and maybe 30 chairs. Tested at shows, other users here at my house, at the spinal injuries unit etc. ALL of them have the same stupid delayed action turn acceleration/turn deceleration thing going on. Why??? Non of those could hit a doorway and go through in a linear accurate easy way. They all drove like hovercraft. All powerchairs steer rediculously and dangerously by default. In almost every case it requires access to an OEM level or better programmer in order to fix that. And on some chairs you simply cannot fix it. For a bunch of different reasons. Even WITH an OEM programmer.

The iBot was no different here. And no way to access OEM level programming tools. So that simple thing alone ruled out this balancer in all its various drive modes for me. It totally removes it from my list of suitable daily use chairs. Thats not its only issue but its one of them.

[ex-Gooserider]

I am T3/T4 complete and cannot do any of what you describe. You sound like T5/T6 incomplete?

Quite apart from this. A joystick offers accurate easy mm perfect positioning. At least once the hovercraft programming has been removed! Weight shift cannot be that accurate no matter what you do. Its clumsy and hard work in comparison. Imagine trying to use your PC mouse to hit a tiny button or highlight a text letter or word for e.g by shifting your body weight! Its just not good enough for accurate positional control.

"Officially" according to the neurologists that tested me while I was in rehab, I'm a T-5, ASIA-B - which translates to "incomplete"... The ASIA scale is supposed to be a more nuanced version of "in/complete" as it ranges from A - no motor / no sensation (aka "complete") to increasing levels of sensation and motor w/ "normal" being "E"

I have no useful motor ability (I can 'twitch' my feet a bit when in bed, and when in a pool can sort of do a slow 'bicycle pedal" that isn't enough to swim, but that's about it) but do have sort of weird sensation, I can feel touch, but can't tell the difference between a 'finger poke' and a 'pin poke'... It seems that I am mostly missing the pain part of the signal. (I have injured myself many times and not noticed)

My injury is not the usual "traumatic" sort where there is physical damage to the cord at a particular point.... Instead it is a "non-traumatic" ischemic attack that happened during surgery, amounting to a stroke that hit my spine instead of my brain....

The result is a slightly different set of issues - I'm told because I have 'lower motor neuron damage' rather than a "break in the line with things below the break still sort of working, just not connecting to the brain... I have NO reflexes, no spasticity, don't respond to electro-stim, etc... This has pluses and minuses, but causes some confusion for the docs that are used to dealing w/ traumatic injuries and the typical stuff that goes with them....

ex-Gooserider

[CPguy]

I tested the hoss mobility thing in person. It is just a segway conversion so a tiny battery and you can only traverse a 6 cm (!) curb. The sales price is insane but the joystick control works.

A BM style chair with lithium is your best bet.