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Author Topic: Driving an off-road buggy by joystick.  (Read 6372 times)

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Offline TinodesisTopic starter

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Driving an off-road buggy by joystick.
« on: December 15, 2007, 03:06:21 PM »
Hello,

First I would like to compliment the webmaster for hosting an outstanding web site.  I have been looking for help on my project and this site has the most information I have seen.

My project:

I want to drive my buggy using a joystick.  I want to control acceleration and two brake levers.

The buggy is all-wheel-drive with skid-steering.  You can see the two brake cylinders in the picture below.  I think I'll need 50 lbs of force to apply the brakes.

The accelerator is just a lever and a cable (like a lawn mower) and the motor runs at a constant speed.  The buggy's top speed is about 5 mph.

The battery is a 6 volt lawn and garden sealed battery used mainly for starting the motor.

Any thoughts on a safe way to accomplish this?  I want to ask good questions but I'm not sure what to ask.  I'm a newbie when it comes to most of this.





http://youtube.com/watch?v=JUV2VVCWiwU

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Re: Driving an off-road buggy by joystick.
« Reply #1 on: December 15, 2007, 04:21:47 PM »
Thanks :D

When you say "drive my buggy using a joystick," you mean a joystick in the buggy, right? (I'm having thoughts of a remote control buggy . . . <drools>)

Anyway, what you want is called 'Drive by Wire', basically meaning the driver pushes buttons, and then motors handle all the hard work. Only recently is this being added to cars. Its a very basic technology so Im sure if you google around for awhile you can find many examples.

Ok so the first step is to figure out exactly how much force/torque your levers and stearing wheel require. Get one of those weight gauges that have a spring inside, and pull. It should give you a force readout.

Knowing this will help us decide what type of actuator you need, which will then determine the controller you need. You'd probably want a linear motor attached to a motor driver.

Offline TinodesisTopic starter

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Re: Driving an off-road buggy by joystick.
« Reply #2 on: December 15, 2007, 04:42:29 PM »
Hello,

Drive-by-wire is what I want, thank you.  I want to drive my buggy just like I drive my electric wheelchair, with a joystick.

I've googled every term I could think of, except "drive-by-wire."  Industrial joystick companies haven't been helpful, and other results give me pc joysticks for playing video games.  Modern wheelchair controllers are too complicated for me as well.

I will spend some time searching "drive-by-wire" and put a spring scale on my brakes to find out how much pressure I need.

I'm a c5-6 quadriplegic so I'll need help putting things together but that shouldn't be a problem.

Thanks again.

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Re: Driving an off-road buggy by joystick.
« Reply #3 on: December 15, 2007, 04:54:19 PM »
Quote
Modern wheelchair controllers are too complicated for me as well.
I didn't think about using a wheelchair joystick, good idea! Ebay should have a lot of old cheap wheelchairs you can buy and scrap for a joytstick and motor drivers.

http://search.ebay.com/search/search.dll?from=R40&_trksid=m37&satitle=wheel+chair+joystick&category0=

http://search.ebay.com/electric-wheel-chair_W0QQ_trksidZm37QQdfspZ1QQfromZR40QQfsooZ1QQfsopZ34QQsbrsrtZd

Offline ed1380

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Re: Driving an off-road buggy by joystick.
« Reply #4 on: December 15, 2007, 05:12:26 PM »
that thing is sweet

joysticks aren't confusing, there are some that are just switches with a common ground.

if you still want it to be mechanical you can try something like this
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Offline TinodesisTopic starter

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Re: Driving an off-road buggy by joystick.
« Reply #5 on: December 15, 2007, 05:23:57 PM »
Quote
Modern wheelchair controllers are too complicated for me as well.
I didn't think about using a wheelchair joystick, good idea! Ebay should have a lot of old cheap wheelchairs you can buy and scrap for a joytstick and motor drivers.
I discovered the used parts on ebay awhile back. I went down to my local wheelchair mechanic and he talked me out of it.  I think hacking one was simply beyond his abilities.

I have an old electric wheelchair in my garage, I may have to have someone take off the joystick and controller. :o

that thing is sweet

joysticks aren't confusing, there are some that are just switches with a common ground.

if you still want it to be mechanical you can try something like this

I was going to use an actuator/servo/solenoid ??? to apply pressure to the brakes.

Does your picture represent a joystick with actuators in front of it?  I don't have a lot of strength in my arms, so manual controls have got to go.

Offline ed1380

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Re: Driving an off-road buggy by joystick.
« Reply #6 on: December 15, 2007, 05:27:26 PM »
just replace the brake cylingers with switches and hook those up to actuators.

also pushing the jostick forward will do full brakes. you can change it around if you want
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Offline TinodesisTopic starter

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Re: Driving an off-road buggy by joystick.
« Reply #7 on: December 15, 2007, 05:33:29 PM »
just replace the brake cylingers with switches and hook those up to actuators.

This makes sense to me now.

Regarding the joystick, I was thinking:

straight forward to accelerate

forward and to the right for turning right

forward and to the left for turning left

and back for both brakes.

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Re: Driving an off-road buggy by joystick.
« Reply #8 on: December 15, 2007, 06:57:14 PM »
Can you take a few pics of your joystick and the wiring on it and upload it here?

It shouldn't be too hard to figure it out.

Chances are you can just disconnect the motors on the wheelchair, and connect those same wires to the motors that will go on your buggy. Just leave the joystick wiring connected to the motor control electronics alone. Same for the battery (although I suspect it may need more than 6V to work).

Offline TinodesisTopic starter

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Re: Driving an off-road buggy by joystick.
« Reply #9 on: December 15, 2007, 08:24:48 PM »
I will get some pictures up as soon as I can.  I have a teenager that will be on Christmas break soon so I'll have him help me.

I found an interesting project with some relevance to mine.  This guy used an old wheelchair to mow his lawn while sitting on the porch.

http://members.iinet.net.au/~tnpshow/RCLM/downloads.htm

Offline TinodesisTopic starter

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Re: Driving an off-road buggy by joystick.
« Reply #10 on: December 30, 2007, 01:27:55 PM »
Can you take a few pics of your joystick and the wiring on it and upload it here?

It shouldn't be too hard to figure it out.

Chances are you can just disconnect the motors on the wheelchair, and connect those same wires to the motors that will go on your buggy. Just leave the joystick wiring connected to the motor control electronics alone. Same for the battery (although I suspect it may need more than 6V to work).

Some pics of the joystick.  I opened the controller too so I can post pics of that if needed.




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Re: Driving an off-road buggy by joystick.
« Reply #11 on: December 30, 2007, 03:03:11 PM »
wow it appears that joystick board is doing quite a lot of complicated stuff . . . I didn't realize they were that complex . . .

I think the best (easiest) method would be to just attach the motor output wires for the wheel chair to your actuators, leaving all that complex wiring the way it is.

Offline ed1380

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Re: Driving an off-road buggy by joystick.
« Reply #12 on: December 30, 2007, 03:56:45 PM »
wouldnt that actually make it stop when you ues teh joystick  :P
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Offline TinodesisTopic starter

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Re: Driving an off-road buggy by joystick.
« Reply #13 on: December 30, 2007, 04:18:56 PM »
Admin,

You're correct, it's looks complicated.  About eight of those wires could probably be removed, but I'll bet the controller will detect the fault and shut down for safety.

Ed,

Hooking the brake actuators to the motor harness would apply the brakes but probably not in a user-friendly pattern.

You stated above that joysticks are simple and I'm still learning more about them.  I might have some "hands on" help soon.  I'll post if I get things working.

Offline ed1380

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Re: Driving an off-road buggy by joystick.
« Reply #14 on: December 30, 2007, 04:29:20 PM »
do you happen to have a multimeter?

if so can you see if teh joystick is just off/on switches or can it actually sense how much you you moved it?
if you've previously used it, you won't need a MM
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Offline TinodesisTopic starter

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Re: Driving an off-road buggy by joystick.
« Reply #15 on: December 30, 2007, 06:23:01 PM »
The controller senses how far the joystick is moved.  Moving the stick forward gently lets me roll slowly, all the way forward gives me top speed.

There are also four modes you can select which change the sensitivity of the stick. High and low in both "Drive A" or "Drive B."

I may build the $50 robot just for the experience.  I'm getting hooked on this stuff and have a lot of ideas about things I want robotic.

I heard there is a local robotics club but haven't located them yet.  A member is supposed to call me.

I thought this tutorial was interesting.  Very basic but a good learning experience.

http://hila.webcentre.ca/projects/joystick/Hila_Joystick/index.html

Thanks.

 


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