Reverse torque

[biscuit]

Good afternoon. I've just noticed that my chair will not reverse up the WAV ramp. Not even when it's empty. I don't generally reverse up ramps, so I never noticed. I thought I had programmed it very nicely.

Years ago I reduced the motor load compensation so it was not so jumpy, and then over time increased the torque (and accelerations) to where I thought it felt ok driving and taking slopes, unevenness, doorways etc.

Should I increase the torque again? or increase the motor load compensation and reduce the torque? I think the VSI also has a setting for something like wiring compensation (I forget the word used, cable/wire/wiring compensation, something like that), also in mOhms, which I never changed as I guessed it worked like motor load compensation.

[Burgerman]

You should increase motor compensation in stages until it performs correctly. Should have just as much torque in reverse as in forwards.
You will then need to reduce torque (which actually isnt torque at all) so that it isnt jumpy at 0 to 0.1mph. Torque setting only increases response by either adding control as a "jump" at the first mm of stick movement or adding compensation in this first mm of stick movement.

If you have a 90A controller you should get the same 90A in reverse as you do in forwards. Thats the whole point of compensation. It allows full torque and control regardless of the speed or small stick movement. It also ensures that it will turn in place properly slowly and in full reliable control without getting "stuck" and then overshooting.

[biscuit]

No 90A here! Current limit is 50A. Cable resistance was the term I forgot. I will try that. Thank you.

[biscuit]

Nice. Thanks . I just put the torque down 5% and the compensation up 5mOhms.

[Burgerman]

I would set torque to zero. Then increase compensation 5 at a time until it became jumpy and then go back a step. Then add torque a bit at a time until it turns in place reliably and consistently without being jerky.

Thats the only way to set this stuff up really. What was stock compensation? That is usually about 5 too low on most chairs to make them smooth and safe and it needs tweaking a little normally. Add 5 at a time and see how it feels.

You need a sensitive bum and feel what it does.
Set compensation to something stupid like 5mOhm and drive the chair. Then you will understand how it feels to have no compensation. Its horrible! That add to your mental understanding. Then set it to the stock figure. And compare both turn in place, acceleration, deceleration etc. Then as you set it 5 higher at a time you will begin to feel its effect. And it will get better and better until it starts to be snatchy. At that point you went too far. And if you go any further it can literally take off and ou cant stop it. Or spin... So theres that! This is why they always set it very conservatively and a bit too low. Never reduce this to make it "smoother" as it takes away all the control consistency and affects everything.

[biscuit]

My computer knows the stock compensation, I forget. It was something like 90 and the chair hopped and skipped all over, which was scary, and I spent quite a few weeks tweaking 5 off the compensation at a time, but assuming it was something near the right amount, and fiddling with the torque, none of which made a good ride, and eventually I appropriately halved the compensation figure (and instantly the torque was responsive) and I went from there.

Tomorrow I shall try doing what you suggested - sounds like the opposite of what I was doing over the past couple of years!

[Burgerman]

If it seems too "sudden" for you with compensation set correctly then REDUCE turn speed. And Minimum turn seed.

If it accelerates too suddenly then reduce forward acceleration, and set deceleration to a very low figure or it will feel jerky. Same for reverse. Leave turn acceleration high. And minimum turn acceleration high as well...

Motor compensation must be set at least to the manufacturers figure or you will literaly have no torque at small throttle positions. By throttle I mean a small "command". But in reverse, a FULL STICK is still a small command because you have it set to less than 100% speed. Without compensation working properly that also means that you will only have a tiny bit of torque.

(note: the actual torque setting DOESENT change torque! Thats not its purpose, unless you are going at about 0.00001mph)

So summary!
Compensation MUST be set correctly. Without it you will have no "power" when up against some resistance like a carpet or your van ramp at slow speeds.

The settings that remove the sudden jerkiness or sharp controls are:
Forward Acceleration
Minumum Forward Acceleration
Reverse Acceleration.
Ninimum Reverse Acceleration.
Turn Speed.
Minimum Turn Speed.

NOT motor compensation, or Turn acceleration and minimum turn acceleration. Leave those high!

[biscuit]

Good afternoon. I re-loaded the original settings and reduced the motor compensation to 0 and got a very smoothe ride including an inch step from road to driveway.

So my settings yesterday and originally were as per the table below:

present +++++ original

acceleration 100 +++++ 32
deceleration 25 +++++ 60
turn acceleration 100 +++++ 30
turn deceleration 100 +++++ 30
reverse speed max/min 30/20 +++++ 40/20
turning speed max/min 38/13 +++++ 40/29
minimum acceleration 100 +++++ 50
minimum deceleration 100 +++++ 50
minimum turn acceleration 100 +++++ 50
minimum turn deceleration 100 +++++ 50
sleep timer 30 +++++ 0
speed adjust driving on +++++ off
soft stop rate 50 +++++ 85
front wheel drive rate 0 +++++ 50
soft reverse deceleraton rate 80 +++++ 70
motor compensation mΩ 60 +++++ 90
torque 75 +++++ 80

reverse acceleration?? No settings exist for that. But the reverse speed is quite low anyway.

remaining as original:
forward speed max/min 100/30

power 100%
cable resistance mΩ 40

Maybe I'm just a wussy driver in a wussy chair. It is the easy fold chair.

[Burgerman]

Setting compensation down from stock to 60 basicaly means its practicaly off. So you wont have any torque or control. Or "torque in reverse" to speak of... So thats why you have this issue.

What hapens if you set it back to stock?
Then reduce TURN SPEED, MINIMUM TURN SPEED, FORWARD ACCELERATION, MINIMUM FORWARD ACCELERATION, and the same with the reverse ones.

Set compensation back to normal.
Reduce all the others in the list above to LOW figures. Or 0. And increase each a little at a time until it gets too "jumpy" for you. Then go back to just where it wasnt.

Reducing compensation to make a chair smooth is the exact opposite to what you need to be doing.

Are you one of these that doesent or cant hold the joystick properly? Pod cupped in the palm of your hand. Stick between forefinger and thumb? If so then you will never have proper control and likely thats why you want to keep reducing compensation.

acceleration 30 +++++ 32 ONLY turn up after testing with compensation set to 90
deceleration SET AS LOW AS POSSIBLE 10? +++++ 60
turn acceleration 100 +++++ 30
turn deceleration 100 +++++ 30
reverse speed max/min 20/20 +++++ 20/20 Adjust upwards if needed LATER! last...
turning speed max/min 15/13 +++++ 20/29 Turn up a little at a time after testing. It only affects speed 1 or very small joystick movements.
minimum acceleration 100 +++++ 50
minimum deceleration 100 +++++ 50
minimum turn acceleration 100 +++++ 50
minimum turn deceleration 100 +++++ 50
sleep timer 30 +++++ 0
speed adjust driving on +++++ off
soft stop rate 50 +++++ 85
front wheel drive rate 50 +++++ 50 Stops it being jerky at speed.
soft reverse deceleraton rate 80 +++++ 70
motor compensation mΩ 90 +++++ 90
torque 0 +++++ 80 Adjust this upwards again very last. And to wherever feels best when JUST starting or turning from standstill only - if you are going faster than a snail its not doing anything and you passed its influence... It can only make a chair snatchy if adjusted too high. If it appears to be doing nothing then compensation is set TOO LOW!!! Its meant to help iniate movement. The first 2 inches.

Then analyse WHAT is twitchy?

If anything.

Then increase each setting ONE AT A TIME until it behaves well with the compensation left well alone!!!

[biscuit]

Thank you so much for spoonfeeding me me with these settings! I have put in all the settings you suggested with impressive results. My chair is far better in all its manoeuvring than how it was. It's not the first time I've programmed a controller, but it is an eye-opener! Crossing from the lawn to the driveway, I could always feel the little bump, but now I do not. As for reversing up the ramp, my chair takes it easily now.

No doubt I'll tweak it for faster turning when I'm up & about again, I haven't clarified in my mind what needs doing.

[Burgerman]

Well now, is the time you set EACH ONE of the following settings individually. DONT touch Compensation, and turn acceleration or deceleration settings, they stay at 100... All 4.

Set FORWARD SPEED to the max. 100. This sets the speed the chair goes when set to high speed on the joystick. Or usually no. 5.
Set MINIMUM FORWARD SPEED to the speed you want the chair to travel at indoors when the joystick is set to its slowest speed. So usually no. 1.

Test this carefully.
Then go to this:

Set MINIMUM TURN SPEED only to a level that works great turning ONLY LEFT and RIGHT (and not while going forwards or backwards). So turn in place speed only, when it is set to the slowest on the joystick - usually 1... So set that minimum turn speed so that the chair turns slowly and safely indoors. It will set the speed only when the chair is set to its slowest "SPEED" usually no. 1 Make sure you have this right for driving indoors.
When you are sure you have understood what that is doing and that you have this set correct move on to the:

TURN SPEED. (not minimum!) That sets the speed the chair turns in place (no moving forwards and backwards yet!) when set to the fastest speed on the joystick. So usually speed 5. So set to max speed 5 and test. Outdoors. Set this to a speed that makes the chair rotate at a speed (when seen from above) like a clock to whatever you feel isnt too fast. But gives the steering speed you want.

Then do the same with the MINIMUM forward acceleration (set it when the chair is at no 1 on the joystick) and then Forward acceleration when its set to max speed 5... The minimum should usually be set to the same as you set max acceleration.

Do the same thing ONE AT A TIME with reverse... If you can.

ONLY when you are happy with all of this, set the TORQUE setting.

Do this by setting the chair at speed 2 initially.
Then while on a carpet indoors, try a gradual turn in place. Take note of the first 2 inches of movement. Only. Thats all it does. Increase it from 0 to 100 and test again. You should feel that it becomes jumpy and that the turn starts more easily. The correct setting is where the turn in place begins at a small stick movement reliably no matter where the casters are pointing. But low enough that the chair doesent feel nervous and jumpy.
Now test this torque setting at speeda 1, and 5 as well. And make sure it initiates the turn in place smoothly and reliably and adjust to make it do so.

NOW your chair will drive properly.