Joystick steering going backwards is backwards

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Joystick steering going backwards is backwards

Postby Rod » 24 May 2019, 22:28

For as long as I can remember I have had a right and a left side. Whether standing on my head or flat on my back, I know my left from my right.
In 75 years it hasn't changed. From tricycles to motorcycles to cars and trucks and heavy construction equipment sailboats and airplanes, everything
had a right and left side. Why is my wheelchair so confused when backing up ? No wonder they have to slow them down, they are totally counter intuitive.
WHY ?
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Re: Joystick steering going backwards is backwards

Postby duke1 » 24 May 2019, 22:46

hi mostly because of the safety nazis and it seems disabled people should not have any fun or be able to steer due to programming for elderly/slow people,some can be improved through reprogramming theres lots of info on that subject on here,good luck
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Re: Joystick steering going backwards is backwards

Postby Burgerman » 24 May 2019, 23:46

Because a wheelchair is different to a scooter/car/plane/truck ec. In that it steers the same way a tracked vehicle does. It uses skid steer type mixing as its the only logical possible way to do this.

Instead of the drive wheels just going backwards and forwards as your car/scooter/etc does, and steer with its front wheels, it is steered by differential drive to the wheels.

Think about this. It is 2 channel. For now ignore the forwards and reverse channel and look only at the steering channel. Push the stick to the LEFT. The chair now rotates on the spot. What would a car do? As seen from above, to the left. Anti clockwise. It can do no other. This is caused by the right wheel being powered forwards. And the left wheel being powered backwards. If you do this in a scooter/car/truck, it does NOT turn at all. The power wheelchair turns on the spot. And you are doing zero MPH. And unlike a car, LEFT stick ALWAYS turns you left. Rotates you anti clockwise. This does not change, when you also move forwards, or backwards.

A car does the opposite. Turn left while stationary NOTHING happens. Seen from above, moving forwards turns left. Moving backwards rotates the car to the right! The CAR is reversed not the chair.

So while doing this, a slow 360 degree rotation watched from above, now add some backwards, or forwards to it. It does this by mixing the signals to the motor. So if you add say forwards while still turning left, then the chair will now go in a forwards ark. Like a car/scooter/truck. Now whilst still rotating left, with left stick, try reversing a little. Yes, you go backwards, but still continue to rotate left as seen from above. So what else COULD it possibly do???

The SAME applies to all tank steered vehicles. Skid steer if you prefer. This is exactly the same. There is no other way to do that!
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Re: Joystick steering going backwards is backwards

Postby wheelie junkie » 25 May 2019, 16:41

Strange, I actually find reversing and steering easier than going forward and steering. as BM explained it is like track steering where you don't have to be moving forward or backwards to turn which is different to most vehicles. Not the only vehicle with backwards steering, bicycles and motorbikes both are counter steered to initiate the turn.
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Re: Joystick steering going backwards is backwards

Postby Burgerman » 25 May 2019, 17:13

Quite. Turning is serperate from back and forwards. It ALWAYS turns the correct way. Cars dont!
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Re: Joystick steering going backwards is backwards

Postby ex-Gooserider » 28 May 2019, 02:39

I find it totally intuitive as long as I don't think about it :ugeek: If I start thinking it gets confusing....

But basically if you just do left / right the front of the chair rotates in the direction of the stick motion....

Add forwards OR reverse, the front of the chair STILL rotates in the direction of sideways stick motion - does the same thing no matter which way you are going....

I had a much harder time learning how to back up with a car....

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T-5, ASIA-B
Jazzy 1100
Jazzy Select 6
Quickie Q-7
Invacare Mariner
Want to make / get a better chair, ideally one that stands.
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Re: Joystick steering going backwards is backwards

Postby LROBBINS » 28 May 2019, 08:22

What I've found helpful, especially in teaching those, such as the volunteers on Rachi's morning van, who've never driven a chair before, is to say "Think of the joystick as your nose. Wherever you point it, that's where your nose is pointing."
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Re: Joystick steering going backwards is backwards

Postby Burgerman » 28 May 2019, 12:10

It never crossed my mind. I fly model helis and stuff for decades, and the rudder/tail rotor channel is the same. It always goes the same way no matter hover, reversing, forwards. It is only reversed when inverted.

But to really confuse it APPEARS reversed when headingtowards you instead of away.

Roll control (ailerons) always works the same. Right stick always rolls right. Inverted or not. But that too looks opposite when traveling towards you. Flying a RC heli is so complex you CANNOT possibly think about it, or you will already have crashed. You learn it instinctively, it suddenly clicks. So you just use all 3 axis channels automatically, simultaniously, either way up, and flying away or towards you. Its as if someone else is flying. You watch and it kicks in. Same with RC planes but less so. If you were forced to think about this as you do it your brain would blow a microchip or two. But its not requred.

What I am trying to say is that you will soon learn this and control the chair without ever thinking about it and it will be done subconciously.
Same as learning to swim, riding a bike. At first its hard and you cant figure it out. After a while you do it without ever considering how. How can you explain how to ride a bycicle to someone that cant for e.g? You just 'get it' at some point and then its natural.
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Re: Joystick steering going backwards is backwards

Postby Rod » 06 Jun 2019, 22:53

Thank you for the encouragement, I know it will come. After being basically bedridden for a few years
by COPD, I was exposed to power wheelchairs during my 75 year old Medicare exams at LAC USC Med center. Wow,
look at those people go. We lived in a steep canyon with a few steps up to the front porch. even when I could still
negotiate the steps, there was nowhere for a doddering old man to go. The "Woolsey" fire changed all that.
Forty years up in smoke. Life goes on. New home has large floor level deck and ramp to carport. Wow, freedom
to go outside by myself first time in four years. I will definitely learn to backup safely. My experience with skid/steer
equipment goes back a long time. I remember riding on Grandpa's lap in the late forties while he drove his little Cat 30
in his orchard. Noisy, smelly, bouncy scary little machine. Less than 20 years later working in the National Forest pioneering
roads on a Caterpillar D 8 bulldozer the memories of the little Cat tractor made me wish I could have given him a ride on a big one.
People that drove Mule teams pulling wagons, were called Mule Skinners, people that ran bulldozers were called Cat Skinners.
For a few years I was a Cat Skinner, long enough to have it become 2nd nature. Working in steep canyons or cutting fire breaks
at night you become comfortable knowing if you turn left, it will. These machines all worked with steering clutches and brakes,
if you pull the left clutch and apply the left brake yer gonna turn to the left going forward or backward. Some modern equipment
uses differential track speed or direction to maneuver. I was told that my Heroes at Caterpillar now had Joystick steering on some
models. They build multi million dollar machines that operate in extreme conditions, I held my breath and Googled Caterpillar
Joystick controls. This is from an online spec page for a new bulldozer:

"Steering. With the machine moving in forward or reverse, move the joystick to the left to turn the machine to the left; move the joystick to the right to turn right. The more the handle is moved to the right or left, the tighter the turn. Regardless of ground conditions, steering is consistent and predictable. Moving the joystick to the far right or left will make the tracks counterrotate for maneuvering in tight work areas. Counterrotation. The D4G maneuvers easily through side loading blade applications. Simply engage counterrotation briefly to correct machine position. Counterrotation also provides easy, quick maneuvering in small, confined work areas."

Whew.

As an old fixed wing pilot I have to take my hat off to the RC guys that fly fixed wing. I can't even imagine what it would cost me in broken
machines to even start to learn to fly Helios. Absolutely amazing. Thanks











s
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