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Australia
Asked — Edited

6 Servo Robot Help Needed. (Ridable)

Hey guys
I just wanted to know how can I control 6 servos with a movement panel, I am a noob when it comes to servos. The front 2 are steering and the back 4 are not. This is gonna be a ridable robot! Call me crazy but I am still gonna make it. Please let me know how I can set this up.BTW I wanna use the arrow keys to control the servos.

Thank you for reading!
:D


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PRO
Belgium
#1  
hi theekshana

do you have a pic from your ARC?what are you using ez-b4 ?



i made some pics.


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the question mark( ? ) explain how to use it.all has these.
Australia
#2  
Thx for the pics and yes I am using ez-b 4
PRO
Belgium
#3  
am a newbie to.

do you use servo's from ez ?
try one servo and see what it does.
is the ez-b4 allreddy connected to your pc or?
Australia
#4  
I wanna be able to use the arrow keys to control it.
PRO
Belgium
#5  
am not sure about the arrows keys how to use it.but i do know there is a ,
wireless remote control.
someone will chime in chortly,for technical details.


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#7  
A Movement Panel will react to the arrow keys, no need for the keyboard control @nomad18.08 pointed you to. The question is which Movement Panel you need, and that depends on the hardware you are trying to drive.

Since you said Rideable, I assume you don't really mean servos, but motors, so you will need H-bridge(s) for the motors. An H-Bridge or Sabertooth Movement Panel can drive a pair of motors, using differential speed for turning (one motor turns faster than the other, or at the extreme, one goes backwards and the other forwards for a turn). However, since you are talking about 6 wheels with only two steering, you will probably need to script your actions using a custom Movement Panel (although you could have an h-bridge Movement Panel driving the front motors, and then script movement of the 4 drive motors based on what the front motors are doing.

But how do you plan to steer a 6 motor device with only the front two steering? Are you going to do differential steering on those (would be difficult unless you do differential steering on all 6 wheels), or some kind of steering wheel that turns the motors. Depending on their size, you might be able to use heavy duty servos to turn a steering wheel or other device, or you could do something with a motor, like a worm gear motor and a gear on the steering shaft to kind of make a rack and pinion type device.

I am not really trying to answer your question here, or scare you away with too much technical detail. Really just pointing out that we need to know much more detail about what you are trying to build, and what hardware you already have before we can answer any questions.

Assuming you bought a developer kit, I would first build a boxbot using a Movement Panel and the continuous rotation servos that come in the kit. (just use some hot melt glue to attach them to the bottom of a cardboard box). Add some cardboard arms with the other servos in the kit to learn to control them, etc. basically, get to know the software and the basics before jumping into a big ride-able build.

Alan
PRO
Belgium
#8  
thtechguru thank you for chimming in.
is that any movement panel?
#9  

Quote:

thtechguru thank you for chimming in.
is that any movement panel?


Yes. You need to first click on the panel so that it has focus, then the arrow keys on your keyboard will drive it.

Alan
PRO
Belgium
#10  
che wants to use 6 servo's.does this mean 6 movement panels?
maybe a pic would be good.
#11  
You can't use more than one Movement Panel in a project. Each Movement Panel can control two modified servos or motors directly, but with a custom Movement Panel and scripting, you can run more than that.

Like I said, we need much more information about the project before we can give useful advice. With what we have so far, we are just taking wild stabs in the general direction.

Alan
PRO
Belgium
#12  
theekshana you can read it,lots off info,a pic or drawing what you want to do.
and what parts you allreddy have.



thank you alan
Australia
#13  
Ok currently I am just planning it right so I am a noob when it comes to Hbridges I have no idea how to make it work, but I have made robots with Arduino and coded but only used servos. But I wanna use EZ-B to do it. And which motors you recommend? and if I used motors how would I do it? with the steering and stuff?
PRO
Belgium
#14  
goodmorning theekshana

on this page ontop you see learn button,click on that.then next page you see,
also ontop page,ARC manuel.there you find all video about devices.
how to use them and connect them.also servo for wheels and H-bridge is ,
on sale here.


H-bridge
#15  
You don't use an H-bridge with servos... H-bridges are DC motor controllers.... Servos basically have a H-bridge built in.... As Alan mentioned use the modified servo Movement Panel (or custom movement panel) to control 360 deg (continuous rotation) servos.... Use the vertical or horizontal servo controls for normal 180 deg servos...

If you are driving normal geared dc motors (there are literally thousands of different kinds so it's hard to recommend any) you would use an H bridge motor controller.... I personally like using a sabertooth motor controller (you can google it) because of it's simplicity, power and versatility....

If you want to be able to "ride" this robot using servos, you better go on a diet. You would be lucky if your cat would be light enough to do it. You will need something like wheel chair motors and a strong frame if you were at all serious about riding it...
#16  
I would suggest differential steering rather than something more complex. If you are set on 6 wheel drive, you will need 6 of the same motor, and an H-bridge with a higher amp rating of all 6 plus some overhead. (you could use one H-bridge per motor pair, but that gets more complex).

You could also use fewer motors and use casters for the additional wheels. A pair of wheelchair motors can move 300lbs at a good clip if powered with 24 volts.

Or, with more motors you could use something like windshield wiper motors. A pair won't move you too fast, but 6 of them would.

I still suggest starting with a simple boxbot to get used to how the software works and then spend some time designing your ride-able robot and run your ideas past this group before making big purchases.

This video (and the related ones on Youtube) show you how to build a simple boxbot with parts from the developer kit. It was done with the V3 board, so the instructions for connecting to the computer are different now, but the basics are all there.




Alan
Australia
#17  
No I am not set on 6 wheels bud I just don't know if 4 wheels will do the trick :/ and yes I will check that out.How do you think I should set up the steering? Do you think these motors will be good? http://www.motiondynamics.com.au/worm-drive-motor-12v-24v-200w-180-rpm-20nm-torque.html and where can I get these "wheelchair motors" from? I am probably gonna cut wood out (very light wood) and I am gonna make the frame probs gonna spary it with spray paint and make a cool image or something on it....
#18  
I would do differential steering. It is much easier than trying to build a steering system that turns the wheels, particularly on a big heavy bot.

eBay is the best place for wheelchair motors. I imagine the availability in OZ is pretty good, although maybe not as good as the USA. I'll need to do some research to see if the motors you selected are a good choice. One advantage they have is that worm gear motors hold their position well when you stop providing power, so you don't need to worry about a brake system or your bot rolling away if you park on a hill (not 100%, but better than a lot of other motors that will just spin free when un-powered.

Nothing inherently wrong with a 6 motor system, just takes some thought and engineering to make sure the speeds match and that when you are turning they all are doing the same thing and not fighting each other. Done right, you get a lot of stability and control under adverse conditions (rough ground) using a six motor system, and of course, good weight bearing without worrying about breaking your frame since you are spreading the load across a larger surface.

Alan
Australia
#19  
Thx for the advice Alan and I think now I might actually do 4 wheel but how do I do the differential steering with that I don't really get differential steering works.... please explain......... is it like that motor bike type or ?
#20  
Differential steering is what you automatically get when you drive motors through an EZ-B movement panel.

In its most basic form, to turn right, the right wheels spin backwards and the left spin forwards. Vis Versa to turn left.

basically it turns in place.

However, if moving forward at and turning, instead of one set moving backwards, the wheels on the side you are turning towards just move slower or stop while the other side wheels push you around the turn.

Think tank or 6-wheel off road ATV.

The other option. What i call "normal" steering is actually much more complex to engineer in a robot. It the way a car turns. Where the front wheels turn in the direction you are turning. Making a robot control a steering wheel or steering shaft is actually quite complex, particularly on a large (or powerful) robot.

Alan
#21  
Differential steering is like how a tank steers... Left wheels spin one direction, right wheels spin the opposite or vice versa... A wide, short chassis will turn better...
PRO
Belgium
#22  
RR is that not how roli works?
#23  
@nomad18.08.... Yep, Roli uses differential steering....
PRO
Belgium
#24  
maybe the roli is a good for starting ez,for theekchana.
United Kingdom
#25  
Skipped the last few posts but to answer the question of a Movement Panel which can be controlled by the arrow keys, you are looking at either the Custom Movement Panel (Under scripting) or the Auto Position Movement Panel (Under servo).

You will need to either script the correct servo positions or make the frames for the movements. Once that is done it's pretty straight forward.

Auto Position Movement Panel is probably the easiest option. Use the Six Example Project as a guide on how to use the Auto Position Movement Panel.
United Kingdom
#27  
Frames are what make up the action, think of frames of a cartoon being drawn.

You only need to make the key frames, as in the specific positions required, ARC will fill in the movement between the frames.

DJ has made a video of how to make movements and actions.

PRO
Belgium
#28  
haha rich thats the video dj made for me.i knew it come in handy.
Australia
#29  
Can someone please make me a differently steering ez-b file? that would help tons!
Thx
United Kingdom
#30  
The tools and guidance is there to help you make your own projects, that's the beauty of ARC and EZ-Robot.

I can't speak for everyone but I personally only guide others to create and achieve their goals, I wont do it for you. It's easy enough to do it yourself if you watch the tutorial videos.

Also, a lot more information would be needed. Someone could make you a "differently steering ez-b file" but it probably wouldn't be what you need. We need to know exact details of the project, how you want it to work in great detail, which ports are connected to which servos, motors, sensors etc. and so much more.
Australia
#31  
Anyone wanna recommend a hbridge for me? someone recommended a sabertooth one.
United Kingdom
#32  
How many motors are you running?
What size motors are you running (i.e. how many amps each)?
Do you need positioning feedback?

The L298n based H-Bridges are great cost effective solutions for running two motors up to 5A however lack any position feedback. If running more than 2 motors you can use multiple H-Bridges and this would require scripting a custom movement panel.

The Sabertooth is more expensive however can handle a lot more current. With the addition of the Kangaroo control board you can also add in positioning feedback.

The TB6612FNG is a smaller and cheaper H-Bridge which works well for small motors, this is what I used in Melvin so runs the original Omnibot drivetrain without any problems.
Australia
#33  
Number of motors: 2
Size: Estimated 10amps.... 24V 250w
What do you mean positing feedback?
and also I am to have a caster controlled at the front controlled by a servo:) idk if that will make me have a custom Movement Panel as I really don't know how to script it.. but if you know how to script it and I need to use it, I would appericiate your help with the scripting.... and I might actually use the sabertooth depending on how this "custom movement panel" scripting is gonna go..
Motor I am planning to use: http://www.jojocycling.com/index.php?route=product/product&product_id=76747&currency=AUD&language=en

Thank you rich and everyone else for taking your time to help me :).
#34  
My advice for you since you don't have much experience in robotics is to start basic and small. Purchase the EZ Robot developer's kit and build yourself a small robot from the kit... The kit has everything you need save for a chassis to attach the wheels and ezb4 to... The experience you gain building it will allow you to build a bigger more complex robots.....
Australia
#35  
Richard, I have had ALOT of experience with arduino robots. But I never used motors or Hbridges with it:) or EZ-Robots I have the confidence that I can make this ima try my best:)
Australia
#36  
If you know EZ-robot scripting let me know:)
#37  
I don't think I have ever built a robot that didn't use motors or servos to some extent... What did you build with the arduinos? My way of scripting won't help you since it is specific the robots I create... A manual for a Honda wouldn't be any good for working on a Toyota... Albeit both are similar cars, they are still quite different in details... Saying that, ARC provides tons of example code to help you get started in scripting....

I can help with the Sabertooth (which is easy). Rich is the H-Bridge guru... But again a physical robot would really help with the coding....

I usually write my software after building my bot...
Australia
#39  
Richard so basicly all it is a caster at the front that is controlled with a servo and 2 wheelchair motors at the back and I wanna use the custom Movement Panel with it.....
#40  
Ok so what you would do:
Straight:
Have the custom Movement Panel set to move both motors forwards and backwards(which, if using a sabertooth, you will have to put a serial code line for each motor, and each direction.) And along with the forward arrow have the steering servo go straight.

Turning: to turn you will need to make the servo turn in the direction you want to turn and at an angle you want. Setting up a joystick which moves a slide script would make this big bot turn smoothly. Along with the servo you'll need to slow down the motor your turning towards,or you'll just start peeling the front tire off the servo. (Think of a 2wd 4wheeler. If you lean back while turning, it barely turns, and if you lean forwards the inside wheel spins as you turn.)

Once you get that out of the way, you need to design the bot and think about these points:

-how will you power it? Most wheelchair motors pull 5-10amps each. This means if you want to go far you'll need lots of power(car batteries)

-how much weight will the motors be moving? You have to think of the chassis, your weight, your passengers weight, and the battery weight.

Hope this helps!
Tech
Australia
#41  
Ok, I think ima pause on this project for now and then start it again, after I have made a little robot with EZ-Robot:)
#42  
Its a good idea. Get yourself familiar with ARC and the ez-b and then go for the big bot. Why not try to make a mini version of your bot? Then you could just scale it up a few sizes. It would also help you realize the challenges you'll face.