mechanically R/C'ing a joy stick
 

Im in a robotics class right now and we are designing a robot for a competion. We finally got a hold of a wheel chair and plan on using all the guts out of it to power our robot. We are now at the process of trying to "R/C" this robot and I convinced my teachers to by a Spektrum DX7 transmitter to control it because they liked my own personal DX7 so much. We still have the original joy stick that came with the wheel chair and we plan on using it to control the robot.

What I would like suggestions on is a fairly simple but effective way to mechanically "R/C" the wheel chair joy stick via our new DX7 transmitter. I have several ideas but I would like to see what everyone else thinks about them.

I have 2 servos and plan on controling it on an x,y axis type deal. I made a few sketches that hopefully make sense but basicly the first one is 2 "slides" that move back and forth on their own axis via a servo and a pushrod. (I realize I only drew one servo in there but I will probably go with 2 servos and "Y" them together for each end of the slide so it does not bind). The second drawing is built on a big base on the bottom and then it has a horizontal sliding platform that slides up and down and on that platform it has another block that slides back and forth, all controled by 2 servos.

The joystick is about 3/4" diameter and 2" tall. It has a total of maybe 45 to 50 degrees of travel from one extreeme edge to the other. and it has a full 360 degrees of travel.

I dont know if I am overthinking this or not but I would like to see what you guys think.

David

RE: mechanically R/C'ing a joy stick
 

some one has suggested to me that I put some kind of hose clamp around the joy stick with two "control horns" sticking out at 90 degre angles and using servos to direct control the stick. I thought about that and realized that when you move one control it will arc the path of the other control. In other words the controls would be a little off and might make an arc turn when you want to go straight but probably not by much. This would probably be the easiest method but it would just have that one problem of arcing the joy stick one way or the other.

RE: mechanically R/C'ing a joy stick
 

My thought is that "R/C"ing" a joystick is like having a seeing eye cat lead a blind dog who is leading a blind man. Why not control the chair's electronics directly with patch cords instead of mechanically controlling a mechanical controller?

RE: mechanically R/C'ing a joy stick
 

I agree with Charlie, adding that some accuracy will be lost in each step.

The servo's movements are much smaller than the joy stick's movements in X or Y.

RE: mechanically R/C'ing a joy stick
 

Strip the variable pots out of the joystick or buy ones with a similar resistance and operate those from the servos.

Good primer on 2 wheel drive steering here [link=http://www.4qd.co.uk/robot/start.html#sas]CLICKY[/link]

I was involved in a big fighting bot and built a couple of Antweights [ 150 g max ] from scratch lots of fun!

RE: mechanically R/C'ing a joy stick
 

Im not exactly sure how to go about controling it with patch cords or really even what that would involve, maybe someone else on my team could look into that. I will be the first to admit I am not exactly electrically inclined I am more of a "mechanical" type thinker. I havent taken apart the joystick yet so none of us know exactly how it is being controled. It is sort of an older model electric wheel chair but maybe that we could use servos to direct control the electronics on the inside. I dont believe it has to have super quick movements so if it has a little slop, that is to be expected and is not that big of a deal for us.

edit. wow, did not see all those posts inbetween, you guys must have snuck in there.

RE: mechanically R/C'ing a joy stick
 

I have sort of another question. Would you guys know if it is possible to take two alike joysticks off a wheel chair and "Y" them together? We half to both RC this robot and send it autonomous. The rc part will be easy weather we do it mechanically or electrically but when it comes to autonomous, we will half to let go of the transmitter and have it run by itself. So far the only thing we have to do that is a lego nxt brain. We were going to have one joystick be controled by an RC transmitter and the other joystick be controled by the Lego NXT motors in the same manner.

RE: mechanically R/C'ing a joy stick
 

We took the joystick apart today to see what was inside. We found that the joy stick had another cup housing around it, but it has four wires coming out the bottom. we did not pull off the cup housing so we dont know whats in there. our teacher wants us to try and use relays to control the joystick to make it an electrical linkage instead of mechanical. The problem is we are unsure of how to go about using relays to do this. And then after we get the realys to control the joystick movements, how would we go about hooking that up to be controlled by the transmitter? Can you guys give me some more input?


Thanks, David.

RE: mechanically R/C'ing a joy stick
 

make it easy, use this http://dimensionengineering.com/Sabertooth2X25.htm

this is what i use in my full size R2D2 robot. also using spectrum dx7