Re: Team 95 Hard At Work - 2015
 

I like the manipulator. Seems like it would be really effective at both totes and containers.

Re: Team 95 Hard At Work - 2015
 

Thanks! I/we was/were getting tired of all of the teaser pics and opted for some transparency instead. If another team wants to copy any we put up, please do!

Thank you!

I can't wait until we have good pictures of the real tote manipulating mechanism(s). But that's all in CAD for now, prototypes were just wrapped up this week.

Re: Team 95 Hard At Work - 2015
 

Had a lot of progress over the weekend. Here are some of the pictures.

This is our main assembly area. Note the house-wiring practice area to the right, this is for the day-time class that uses this space.



What the CAD of the gripper looks like:



The arm assembly is getting some tweaks to improve stiffness.



Decided to try out velcro to mount electronics this year. It seemed like a good opportunity given the lack of defensive impacts we'll see.



And much of the robot got wired up! We made all the transmissions turn and such. No pneumatics and no real sensors wired... yet. We left PWM and other signal cables loose to aid in debugging.

Re: Team 95 Hard At Work - 2015
 

Cool, did you use a bead roller on the belly pan? Does it add any noticeable stiffness?

Re: Team 95 Hard At Work - 2015
 

Yes we did and yes it does, it makes a very big difference in stiffness, at least qualitatively. It was the first part we ever bead-rolled (and my first, personally). Was a little nerve-wracking for the student and I who did it, but it's pretty easy to do, would highly recommend to teams who do sheet metal parts.

We also noticed that the bead makes a good shape to drop counter-sunk bolt heads into... but given that we're using Velcro this year we haven't drilled any holes in it yet.

Re: Team 95 Hard At Work - 2015
 

Looking good.

Re: Team 95 Hard At Work - 2015
 

The deck is PET-G, not polycarbonate. We have found PET-G to be nearly as robust as polycarbonate while being roughly half the cost. The deck was cut on my CNC router.



Another view of the chassis.



Some big steps were made in assembly of our main arm.

Picture of the 4-bar links.



4-Bar being moved by hand to show the arms articulation and range.

https://www.youtube.com/watch?v=ahGZ...ature=youtu.be

As she sits we're looking at 75lbs for the base and 10lbs for the arm+gripper. Not too bad...

Re: Team 95 Hard At Work - 2015
 

Interesting video. Your arm is positioned perpendicular to your wheels and appears to go on both sides of the robot.
Can you talk about those design decisions? It looks to me like it was done such that step-container autos would be easier, but I'm not sure.

Re: Team 95 Hard At Work - 2015
 

I can, and am happy to.

The primary objective of this arm mechanism, our main mechanism, is to grab RCs off of the step and place them upright on, or near, the scoring platform for us to use later, for our alliance partners to use, and to deny them from our opponents. After doing a time-study we concluded that being able to do grab and place the RCs without any significant driving or robot re-positioning (i.e. grab, back up, turn, place, drive to next RC, realign, grab) was the most effective method. Currently our operation looks like: align, grab, drop behind, drive to next, grab.

After looking at the geometry we determined that the same arm that could grab RCs from the step could also cap 5-6 tote stacks on the 'front' and at least 4-tote stacks on the 'rear.' Given the ability to rapidly deploy a single arm, with a single degree of freedom, we thought that this would make a great counter to any robot that makes a grab for multiple RCs in auto. Could that robot hold onto 2-4 RCs if we're latched firmly onto one of them, pulling with all of our might?

The arm is designed to reach the RCs on the step without disturbing any of the totes in the landfill. We wanted to reduce the destabilizing moment from the RC and improve the stabilizing moment from the robot to make our RC-grabbing design as capable and fast as possible. This dictated pushing our wheelbase as close to the RC as possible. Orienting the wheels as we have does this. A traditional tank drive would require a lot of coordination and/or very precise driving in order to align on a recycling container. Mecanum wheels, on the other hand, allow us to drive 'forward' onto the RCs, as well as 'strafe,' to reduce the difficulty in acquiring the RCs while allowing us to put wheels where we wanted. This, coupled with the fact that we've made a mecanum robot before, lead us to select mecanum drive over alternatives like h-drive.

Re: Team 95 Hard At Work - 2015
 

Well done. I look forward to seeing it in action!

Re: Team 95 Hard At Work - 2015
 

Do you plan on using sensors to position or are you just going manual on that?

Re: Team 95 Hard At Work - 2015
 

Encoder plus a magnetic limit switch or two.

Re: Team 95 Hard At Work - 2015
 

"Virtual" 4 bars are my absolute favourite mechanism to see on any robot, and I'm very impressed with your implementation. I love the idea of aircraft cable (or something similar) for the parts of the 4 bar where you don't need chain. Nice work.

Re: Team 95 Hard At Work - 2015
 

Thanks! We like using chain for 4-bars, but the arm is so long that the weight was really adding up. Enter the 221 robotics tensioners, some 3/32 cable, and a few custom clamps anyone can make on a drill press, and voila! Light-weight 4-bar linkage!

Re: Team 95 Hard At Work - 2015
 

Thanks!

We drove it around a bit last night, but the arm damaged the chassis due to assembly with some under-sized screws.

In good news the two CIM motors can hold arm position at about 10% throttle without the air cylinder counter-balance, so it should be quite robust once the transmission mounting hardware is sorted out. On the other hand there are some tremendous forces involved... hopefully we can keep the destruction from happening again.

I hope to have a video of the RC arm in action this week.