Theekshana
Australia
Asked
— Edited
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!
do you have a pic from your ARC?what are you using ez-b4 ?
i made some pics.
the question mark( ? ) explain how to use it.all has these.
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?
wireless remote control.
someone will chime in chortly,for technical details.
here the link how to do it.
arrow keys
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
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
maybe a pic would be good.
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
and what parts you allreddy have.
thank you alan
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
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...
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
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
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
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.
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.
Thx
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.
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.
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
Motor I am planning to use: http://www.jojocycling.com/index.php?route=product/product&product_id=76747¤cy=AUD&language=en
Thank you rich and everyone else for taking your time to help me :).
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...
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!
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