As my final project for this year, we are going to take a small grey game tote and turn it into a robot that pulls the " weeping angel" on you. For those who don’t know what that is, basically, it’ll follow you around and when you turn around it’ll freeze in place, or drop to the ground and not move,depending on how complicated I want to make it. Dropping to the ground will require pneumatics parts that we don’t have. It will look pretty much the same as a regular tote when its finished. Except with wheels, of course. Any ideas or helpful hints as to what I should use would be greatly appreciated. I am going to be using the old cRIO four slot and the old control system parts. The only problem is the drive system. The rest I can handle.
I seriously doubt that this function will “require” a pneumatic system. I am sure that you’ll be able to come up with at least four different ways to do this without pneumatics. Don’t limit yourself!
If you could describe what drive system components are available to you it might help you get more useful advice, and you might figure out something on your own. So, what do you have?
If you’re planning on using pneumatics, I would reccomend using 1/2" stroke pistons to raise/lower your drive train. If you’re really going for the Weeping Angel feel, you should add air restrictors to control the speed of the pistons. Nothing ruins the mood of being silently watched when you hear puffs of air and a tote clanking to the ground.
Staying in the mind of a weeping angel, you should either disable the compressor when stalking, or use an off-board compressor. You shouldn’t need that much psi to lift the tote, and with enough tanks you won’t need to recharge for long periods.
When it comes to building a totebot, you should ask the guys who made the one previously shown of CD.
For this project to be effective you want the thing to be as silent as possible while moving, and make it look as much like a regular, unassuming tote as possible. I’m picturing rubber wheels that touch the ground via cutouts from the bottom of the tote.
How does it detect when you turn around? Face recognition?
I like the idea by the way. I hope you post a video of it when you’re done.
I wouldn’t think of “raising and lowering the drive train” but instead I would think of “raising and lowering the tote.”
Here is a masterfully done CAD rendering of an idea: http://imgur.com/4ebNHBF
Use a winch in the middle, some cable, and some pulleys, to hoist the tote up around the drive base, and then set it down. All motor-driven, no drive articulation, and you could easily take all of the robot guts out of the tote to work on them.
There were 2 tote bots at the Indiana District Championship and neither articulated. Both could sit still and appear to be resting on the floor.
Currently, I have the full control system assembled, two talon sr controllers,as many cim motors as I could ever need, and pneumatics parts, and of course, the tote. We have several types of wheels. The only limit is the drivetrain itself, I may be limited to just 2 CIMple box gearboxes.
Also, if I get the time I’ll program it to make mouse noises like squeaks and yips as it moves around.
The face recognition will be a problem of course
However you are correct on the cutouts, I was planning on doing that. And yes, it must be as quiet as possible. It also needs to have restraint so there isn’t a insane box chasing everyone around
^This. The trick was ground clearance, something neither had much of. In one case (the 868 one) there IIRC was some suspension so at least it had a chance if it got stuck on something… the other (the 3940 one) had a solid mecanum drivetrain that did get stuck on the scoring platforms a few times the one practice match it was used in (as a “50 point bonus if you catch it” prank on 3940).
In your shoes I’d run 2x cimple boxes wiht 1 cim each and with the stock reduction to 2WD. Simple, light, reliable. Put a caster wheel or skid (or omni-wheels) in the “back” where your two driven wheels are not and make sure your battery is near your driving axle.
One simple option might be to use a range finder. Have code that tries to optimize the distance to target to, say, 6 feet. As the person moves forward, the tote follows, trying to keep exactly 6 feet away. If the person stops, the tote will stop.
And, yes, set a maximum speed so the thing doesn’t start chasing everyone (funny as that would look!)
I would love to see a video of that! Surely someone must have been recording it…is it posted somewhere?
Not sure. It was Thursday night at IN state champs, Andy Baker driving the totebot from the sidelines.
This it the bot so far, it shouldn’t take too long to build. We are planning on getting the 2015 robot to be able to chase it
I’m picturing a bunch of people in the room having a meeting nonchalantly while in the background your robot is chasing this tote around. 
If you wanted to use pneumatics on the drive train, you could use a butterfly type drive, with the back traction wheel up inside as the axle/pivot point and just use 4 mini pistons to keep the tote elevated and be able to pop the wheels up inside. http://www.teamneutrino.org/seasons/ultimate-ascent/robot/butterfly/
I can just imagine that conversation.
" so this chart shows…"
" excuse me, but what is that thing doing?"
" fighting crime. Against boxes. Next question"
Our robot is named the black knight. I just got the idea of painting the box joker colors and giving the black knight a cape. Lol.
Update to the project
We have chosen a chain driven mechanism with two Andy mark motors driving them in a tank drive system, with a Omni wheel in the back. Ventilation might be a problem seeing as the tote will be closed. We chose victor motor controllers for the drive motors. Using the old control system will take up a lot of space so space is limited for anything other than the core drive system. Possibly some LED lights or some gizmo to improve the ridiculousness of this robot
I will post a photo tomorrow, as it sits the robot is just the tote, we laid the electronics out in the tote to see if it’ll all fit. The wheel slots have been cut out of the tote. The sprockets need to be drilled out to accommodate a screw to connect to the motor shaft. The wheels are the old KOP white high grip small wheels. The Omni has yet to be chosen. The robot shouldn’t reach too high of a speed overall. Both wheels will be on the same axle to save space, and each will have its own motor.
Try it without ventilation first. Drive it around for a while then quickly stop it and check the temperature of the Victors. If you cannot hold your fingers on them, they are too hot.
The tote has a fair amount of surface area. Heat will pass through the walls to the outside. The plastic is not going to be a good conductor of the heat but it may be good enough. You may want to install one of the large fans that comes in the KOP to circulate the air inside the tote. The more driving around you do, the more heat the Victors will dissipate. This is offset by the air flowing over the tote as you drive. Some of the smaller AC motor controllers (under 50hp) we sell at work get put into large, totally sealed boxes due to the dusty environment they are being used in. There are formulas for calculating the size of the box needed based on the heat generated by the motor controller, the surface area available to dissipate the heat and the ambient temperature.
You could always poke a hole in the bottom where stuff won’t be seen, and add a fan if needed I suppose.