need help with electric steering 'pics'

[brokin]

Hello,
My name is Dwayne, I'm a quadreplegic due to a diving accident that broke my neck in 1994. i am totally paralyized from my armpits down and i hve lost the use of my grip in my hands and the triceps in my arms making my arms weak and unable to steer a straight rack steering vehicle.
I have been searching for a vehicle i could easily adapt to my disability so i could drive it. I bought a carter dlx off road kart that was easily modified to hand controls for gas and brake, it has rack and pinion steering but it is so stiff i cant turn the wheel.
We tried electric cylinders/rams and they were to slow, we also tried using a 24vdc motor coupled to the rack its self, it was inconsistent and unpredictable, hydraulics wont work as it has no PTO for a pump and the electric hydraulic pumps use lots of power and would sap my batteries plus I'm told they wouldn't be able to run constant anyway [ less than 30 mins constant run time ]. I'd like to convert it to electric power steering i know from research the Honda insight, Honda s2000 and the Honda nsx uses an electric power steering rack but i cant find one anywhere so i don't know if we could make one work or not .

So heres where i am, i have the buggy with hand controls working great but cant steer it. I have as of now 2 deep cycle 12vdc batteries mounted in the passenger floorboard, wired to a momentary dpdt switch to power a dc motor that is coupled directly to the steering rack . Ive tried 12volts and 24 volts to power the steering but neither are perfect and i either get over steer [ 24v ] or under steer [with 12v] and never the exact direction i want to steer in. as speed [ mph ]changes neither of the voltages work well.it either steers to fast when I'm going slow or to slow when I'm going fast.

any ideas how to get electric steering to work or what parts i would need? heres some pics we took before modifying anything....

http://img212.exs.cx/img212/5467/overall5ji.jpg

http://img212.exs.cx/img212/9515/driverfrombehindfullleft9ex.jpg

http://img212.exs.cx/img212/7100/driverfrombehindfullright8bg.jpg

http://img212.exs.cx/img212/5626/driverfrombehindstright1az.jpg

http://img212.exs.cx/img212/1324/010102076aa.jpg

http://img212.exs.cx/img212/7939/010102055ko.jpg

I'd like to get this thing where i could drive it, any ideas are appreciated, we've tried all we can think of..... if you need any more pictures of the buggy's steering setup or measurements just ask and i will provide it, BTW it takes between 35 and 40 ft lbs [ with torque wrench on steering wheel ] to turn the steering wheel.

ive not drove anything in close to 11 years and dont trust myself on the highway so i wanted an offroad cart to ride with the atv'ers in my community, ive had the cart for over a year and still cant figure anything out. any help would be appriciated.

 

[ccjersey]

What about a solid state control like the cart drive motor uses, linked to the accelerator pedal, but decreasing the voltage to the steering motor as the drive motor voltage increases. At a standstill, when steering effort is high, the voltage would be at the highest, and at top speed, the steering voltage/power would be lowest.

Control would have to match the motor, so you might have to get a motor to match the control.

Let us know what you come up with. Spring is coming!

Jim

 

[brokin]

hello ccjersey and thanks for the reply ! on flat land i think that your idea would work, unfortunatly i live in the mountains and most of the riding i'll be doing [ if i get the buggy going ]involes going up hills / slopes and coming down them. So it would take more gas/throttle going up and steering would be to fast and when coming down the hill id be using brakes or no gas and steering would be to slow .

Ive been racking my brain trying to figure something out to accomplish this task, and i just cant figure it out.

HELP !

 

[ccjersey]

Coming downhill would be like sitting still, no pedal=max voltage to steering. You're right about going up a slope though every golf cart I've ever driven slows down dramatically going up even a gradual hill.

How about an electric rough terrain (golf) cart or even a gasoline one which could power the hydraulic steering. Used ones might not be too expensive and with a good set of batteries, will go a long way on a charge What about a John Deere "Gator" or a Kawasaki "Mule" etc. Really useful, dependable vehicles with plenty of power to run whatever steering you come up with. Might ought to test drive one and see of the standard steering is a possibility.

Jim

 

[Rodmcm]

Perhaps you need a small contoller that always puts the rack into the same position. What I am thinking of is that you put a potentiometer on the sterring wheel, and one in the rack, then a simple controller that runs the DC motor. This means that the wheels must always go to the same position for the same driving wheel setting? Try contacting a local company that makes industrial valve controllers.

 

[abcd3286]

Did you solve the problem?

Where do you live? I'd take a crack at it if you are near Seattle.

I think you are going to have to use hydraulics. The cost of course is reduced mileage (battery consumption).

 

[fsmyth]

Sounds like a good application for a simple servo -
a D.C. motor and PWM drive plus gearing. If the
PWM driver is selected correctly, it should continue
to work even when the batteries are down to where
there is almost no motive power left. The addition
of a rotary encoder will make the travel consistant
regardless of battery state (as long as there is
enough power available to operate the PWM driver).
This additional feedback circuit is obviously added
complication, but may be desirable.
How is your current motor coupled and driven?

I believe if I was to rig it, I would leave the
direct mechanical connections, and add it as an
auxillary booster (i.e., power steering). Can't
tell from the pictures if that is how you have it.

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