Suggestions for increasing the torque on robot steering system--new system almo

P!-Ro

Hey guys, I can't go to school this week so I figured I would start working harder to get my bot up and running. Only prob, the steering motor runs too fast so it doesn't have the torque needed to turn the wheels. If any of you have had to do with something similar please explain what you did, it would help me immensely. Check out the photos if you are curious on my current setup. Suggestions/comments are welcome.

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PG

Post Edited (Pi Guy) : 11/8/2009 10:56:49 PM GMT

Duffer

Shortening the lever arm between the motor and the steering bar will increase the torque, but it will also decrease the travel length of the steering bar which will mean that the wheels won't turn as far.

Duffer

Timmoore

I can't tell but it looks like you have a 90degree gear that is turning the arm that is moving the steering?
The choices I can see are
different motor - slower/more torque - maybe a window motor since they often have the 90degree turn built in and tend to have a lot of torque
Add gearing between motor and turning arm
Change gearing and arm to be a screw gear - attach a screw rod to the motor, attach the nut to the steering column, when the motor turns it turns the screw rod then the nut can move side to side, this gives a large increase in torque.

Beau Schwabe

Similar to what Duffer said.... increasing the length of the lever arms of the rack-n-pinion to each wheel will have a similar effect to shortening the lever arm between the motor and the steering bar.

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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

P!-Ro

Shortening the bar will help some, but I doubt it will be enough to turn the wheels fully, especially in the grass. Perhaps if I'm feeling less sick tomorrow I'll make a vid for you both to see. I've been thinking about it for a while, but it's definitely making me frustrated. The last thing I want to do is re-design the steering system. I am willing to create an attachment for the top though, however I'm just unsure how best to do it. I could use gears, and maybe weld the motor arm to it or make an attachment that fits it's base, but thinking about it, it seems to lead to a lot of adjustment issues.

Last week there was a boat in the school welding shop that some people were working on with a steering system where when the steering wheel was turned a piston-type end to a flexible tube would push in/out. If I could figure out how to make something like that to put on my motor all I would have to do is make a mount for the piston to push on the steering bar. The only problem is once I get it done it might be more complex than the ideas you guys already mentioned.

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PG

P!-Ro

@Beau--sorry to miss your post. Yes, I can do that. At one point I thought about making it adjustable, but I'm not sure if I'll still do that. The problem is there is a large lack of power in the system, something that won't be fixed by changing the size of things. I need to find a way to gear it down. Unfortunately when I made it I didn't realize how much power turning would take. Oh well, learning on the job I guess.

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PG

Beau Schwabe

Pi Guy,

Check this thread out for an actuator that I built for steering...

http://forums.parallax.com/showthread.php?p=525233






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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

P!-Ro

Hmm, you got me thinking again. I'm not sure where to get all those parts but I can look around. One of my main objections is having to re-weld the bracket for my motor so it will face the correct direction, but I remember someone talking about using gas lines as a flexible shaft. I'll have to look into it, this will be interesting.

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PG

P!-Ro

Just for an update I have all the parts I need. I will start working on getting everything fastened tomorrow.

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PG

P!-Ro

Put the two together now. If I don't spend too much time hanging out with friends I should get the robot working in a little over a week (hopefully). I still have more cutting/welding to do to get my motor in the right spot.

Just wondering...why am I posting this info anyway?

GeorgeCollins

Pi Guy, you know why you are posting this? Because you are my hero! Developing mechanical parts for robots is so hard for me, and I think for a lot of other people as well. To see you go on this form, show your problem, find a diagram, and then build the thing is kind of amazing.

Many people report they are having a problem and then disappear into the ether. It is really encouraging to see someone work through a problem, you know they will really build robots. Congratulations.

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My Robots

W9GFO

Yes. Following through. One of the tougher skills to master. It's great to see that you are still on this project. How many months has it been now?

Rich H

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The Simple Servo Tester, a kit from Gadget Gangster.

P!-Ro

A lot. I would probably be done by now if I wasn't racing friends and blowing up butane, but I'll get it done. I'll see if I can get the parts into the shop today. Thanks for showing your interest, it helps me get the job done.

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PG

P!-Ro

I've been playing it safe recently and had enough time to do more work. I will try and finish it this weekend if I can--that is, if I'm not hanging out with friends.

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PG

erco

Nice fabrication job, old-fashioned machining is not an easy skill to master and it's sad that it (industrial arts) isn't taught in school any more. Most people don't go much past drilling holes or hacksawing these days. You've made a whole steering system!

Good intro to Ackerman steering at http://www.rctek.com/technical/handling/ackerman_steering_principle.html

Your lead screw is very nice part, probably with ground or rolled threads. It has a very course angle, and was probably designed for a recirculating ball bearing application, like a cars' steering box. Looks like you made a threaded nut-like part from a square steel channel. No mean feat! But since you're rubbing instead of rolling, there will be lots of friction. You will want to use lots of serious lithium or silicone grease on those threads, and cover the whole assembly with something like a CV joint boot or flexible bellows on each side to keep dirt out and grease in.

A few more suggestions: make your pivoted connection to your square nut·in line with·the leadscrew. Anywhere else will cause the nut to cock and bind on the leadscrew. Also lubricate every pivot in your steering linkage, there will be a lot of wear & tear. Good luck, and keep posting your updates!

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·"If you build it, they will come."

Post Edited (erco) : 10/30/2009 7:30:46 PM GMT

P!-Ro

Well, they obviously teach it somewhere since I'm doing the lathe work at school, but maybe it's just Idaho. I'm figuring it will have a lot of friction, but the motor is plenty strong enough to do the task. As it is, it seems to be breaking the system itself more than anything else. Or maybe that was just because an idiot was messing with it? But I now have to fix up a few things and hopefully make it stronger along the way. This is the second version of the steering system so I had better make it work.

Just to explain things further--I'm not sure what you are talking about with the lead screw, but if you're talking about the part that the 1X2" tubing is on it is actually a drill bit for cutting cement. It was just lying around, so I used it. I used tig to weld it to stainless pipe so it would fit in the 1" bearing, unfortunately making it lopsided, and then I pressed it in tightly so it isn't even necessary to use the set screws on the bearing. The part holding the bearing is just a pipe I cut and beveled to make it fit, and welded the other pieces to it so it would hold it and be easily mounted. The 1x2" metal part I mentioned earlier is just that, but with a 1/2" hole drilled in one side and a 3/4" hole in the other. To get it to fit in the 1/2" side, I used a grinder cutting blade to put a slot in it, forcing it to move with the screw, or drill bit. Hope this answered any questions, it really isn't too complex.

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PG

mikediv

PiGuy is that a windshield wiper motor? It looks very robust. I recognized the drill bit very clever its amazing what some people can turn into working stuff thats a really big robot was it your go cart at one point? I would love to see some pictures of the whole thing

P!-Ro

Built from scratch, actually. All the substitution shows how far a jobless 15/16 year old has to go to accomplish dreams. It's just too bad it hasn't happened yet, but it will. I'll get you a full pic later, but unfortunately it will probably be something I've already shown on here before.

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PG

P!-Ro

Nothing special, a couple pics.

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PG

P!-Ro

It's now reinforced and, as far as I can see, idiot proof. Now I just have to perfect it and I will be ready to try mounting it this weekend. If all goes well, I may turn the manned rover into a robot. Don't be too hopefull though.

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PG

P!-Ro

I worked on it today, I'm hoping to have everything mounted tomorrow. Once all on the moment of truth comes on whether it will work or not. For now, I keep my fingers crossed and remain hopeful as I get a good nights sleep. I'll be sure to give you guys updates and pics tomorrow. Once this is done and I stop the motor from smoking when connected to the battery, I should finally be able to give this thing some robotic capabilities before working on the next couple systems.

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PG

PJAllen

Llook, llamas.

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P!-Ro

Lol, yes I have llamas. Used to pack with them, now they just keep the grass down.

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PG

P!-Ro

Day late but I blame it on the llamas. j/k

It isn't done but it's functional. I still need to give it wider turning angles and give it more torque by increasing the leverage on the steering bar. Then I intend to use a ping to inform me of the turning angle since it is easiest. After everything is where I want it I will attach the steel cable to it instead of that wire and make it permanent on the fully functional and finally finished steering system. Next up: brakes

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PG