These clips hold the door brush to the side of the PVC sheel around the auger.  The brush is critical because without the resistance of the bristles, the balls would just roll down the auger.  The clip on the left is different because it needs to clear the motors on the agitation assembly.

These two waterjet parts were, as usual, provided by the generous Richie P.  The one on the left is where the 30 tubes of balls will plug into the agitation/distribution assembly.  The circle on the right is made of steel instead of aluminum.  It acts like a ring gear, and with rubber triangles along the perimeter, is driven to disrupt any balls that might be jammed at the entrance to one of the 30 holes.

This video highlights the first time we turned on the auger after it was mounted in the main structure.  Besides showing the coolness of the auger, it also shows all the progress we made on the structure!

The sloped basin which funnels the balls into the auger:

Raised key units with some main structure:

One of the wings:

After a bit of confusion with OnlineMetals.com, I got all 94 feet of Aluminum 1”x1” in the mail.  I cut it up into the appropriate lengths using the cool new carbide-tipped miter saw in the robotics club.  In the end, there are 54 lengths of angle that all need holes drilled in specific places.  All these pictures are from my cell phone, so bear with me…

40 of the 54 lengths needed for the vibraphone:

Key Units Painted

The first attempt at painting the key units was a complete failure.  However, Megan Dority suggested that I used primer, and even picked some up for me.  It worked like a charm.  Also, Austin Buchan was able to get the group access to the Newel Simon paint booth, which was a huge help.

Key units drying in the paint booth:

Key units after drying:

Waterjet Parts Donated

RobOrchestra founder and alumnus Rich Pantaleo came through once again for the group.  He was able to obtain a large donated sheet of 6063 Aluminum in just a few days when we needed it most.  Also, he cut out all the parts we needed just a few days after getting the sheet!  I made a few mistakes on those parts, but nothing too critical.  I had to widen half of the slots in the giant half circles because I didn’t account for the thickness of the paint and the oversized hardboard.

Completely assembled and painted key unit:

All of the key units on their half circles:

Instead of relying on tension in cables or cloth to keep the wings in their proper place, kickstands were added to each wing to keep it in the right position.  The kickstands also serve as the mounts for the cables that will be keeping the cloth tensioned.

All surface that could potentially come into contact with the steel balls are covered in a 1/8” thick layer of neoprene foam.  The foam will be attached with an adhesive instead of using hardware.  The longest diagonal of the final outer area of the robot are just under 8 feet.  Despite a few minor edits in the basin, the addition of the kickstands, and some other tweaks, Vibratron is still able to fold up into a neat 1’x1’x4.5’ column for storage and transport (excluding the two separate racks of key units).

The entire structure is made out of 94 feet of aluminum 1”x1” angle, varying in thickness from 1/16” to 1/4”.  That aluminum has been ordered ($140.61) and fabrication of the main structure should be underway before mid-February.

With only $200 left in the $1,000 budget, the group still needs a 48’x36”x1/4” sheet of aluminum to waterjet into some very important pieces.  Using cheap 3003 H-14 aluminum sheet, it will cost $160 just for the raw materials for those pieces.  That leaves only $40 in the budget for fabric, foam, a power supply, steel cables, and other hardware.  Obviously the ends won’t be meeting, so we need to look for a donation of the aluminum plate.

At every timestep in the simulation, we are given the current joint angles and velocities, and we need to return values for torques that we want to apply at each of the two joints to control the arm.  Basically, we used PID Control to do some really cool stuff, including having the robot write my signature!

Jon was an incredible partner on this assignment and I look forward to working with him again.  You can view our final submission here.  I can’t wait till the next project!

Giant Circle Full of Key Units

The large waterjet circle that held up all of the key units was three feet in diameter.  Combined with the overhang of some of the key units, the diameter of the robot was at nearly five feet.  Separating the giant circle into two large semicircles fixes the problem pretty easily.  Hand grips were added so that the semicircles could be carried easily.  Even though they are 25 pounds each, the semicircles can be carried close to the body with arms locked, which is a requirement for simple transportation of the machine.

Fold Out Wings

Instead of the large fixed upside-down-umbrella style from the previous design, this design has four fold out “wings” that catch the balls and funnel them towards the center.  The overall diameter is six feet when open, but the wings can fold up completely vertically alongside the column.  Between each wing is a pie-wedge shaped piece of cloth or foam.  This has a duel purpose of funneling balls toward the center and regulating the deployment height of the wings.  When the wings are raised, the compliance of the cloth/foam will allow it to fold.

Deeper Square Basin

The previous basin was a thin circle, but our research with the prototype of the recirculation system has suggested that we will need many more balls in the system to reach steady state.  A wide square basin rigidly integrated with the vertical columns can hold the necessary volume of balls.  Four trapezoidal sheets of plastic also keep the balls rolling towards the center of the basin.

Design Changes

The biggest change between designs was the decision to not remove the material between key points, exchanging concave cutouts for straight lines.  Each new unit is made of five separate pieces of hardboard, connected by wood glue (instead of plastic welding).  Only two parts per unit are unique, instead of 3, which makes machining prep and assembly easier.

Circular Structure with New Key Units

The new key units attach to a horizontal 1/4” plate, just like the previous version.  The only difference is that instead of two clips and two colder pins, these units attach with just a colder pin.  Nothing else in the structure needed to be modified to accommodate the change.

Machining

All of the pieces for all 30 key units can fit on five sheets of 2’x4’ hardboard.  Hopefully these items will all be machined by the end of the winter break so focus can be shifted to the design and fabrication of the structure instead.  Below is an example of how the pieces fit on a sheet of hardboard.  The labels are engraved .02” into the board, and everything else is a profiling cut.

Overall

Two versions: Lombardo and Buss

Very Bright LEDs

Everything Connected to Top Structure

Electronics on the Back

Arduino with Tons of Inputs and Outputs

IR Emitter/Detector Breakout Board

MOSFET Board

For the final lab assignment in my Robotic Manipulation class, we were challenged to competitively stack cups.  We were given six 3 inch tall plastic cups, and were instructed to make a 3-2-1 pyramid out of them, then destroy the pyramid, as quickly as possible.  Before we even began working on the project the best team had already done it in only 12 seconds.

The robot arm is currently equipped with a descent pneumatic gripper.  Two big plastic pads squeeze the cups one at a time to contain them.  Stacking cups one at a time is inefficient, but teams were doing it.  Nico and I decided that we needed a some mechanical advantage.

Design Goals

The biggest design limitation was that the only way to actuate our device would be to integrate with the existing gripper.  This limits us to on-off control, which prevents us from picking up all of the cups at once and releasing them strategically.

However, the bottom stack doesn’t really need to be picked up, it only needs to be slid across the tabletop.  Also, picking up two cups at once for the middle layer saves time as well.  The top cup could even be optimized by dragging it into the stacking area initially.  If any of these goals could be met, it would give us an advantage over the other teams.

Interface

In our previous lab, we were able to use the gripper to attach our end effector to the DENSO arm.  However, because we rely on the actuation of the gripper to activate our mechanism, we needed an alternate means of attachment.  The T-slots on the end of the DENSO arm are the perfect size for a 1/4” nut, which is the standard size for a #4 bolt.  Attaching here gave us a reliable fixed reference point.

Fabrication

Using the robotics club CNC, I was able to build the 6 parts necessary for the device.  The only problem I encountered was bowing and vibration in the middle of the largest piece.  Because my piece (11.58”x3.68”) was near the maximum limits of the machine (12”x4”), it was difficult to secure the middle of the stock.  All in all, it took about 5 hours of machining to build the entire mechanism, half of which was slow-going CNC time on the largest piece.

Performance

In the end, we were able to achieve a time of 5 seconds.  Nico and I are pleased with the results, and expect to have the fastest time in the class.