Andrew Burks

Archive for December, 2010

Improved Key Unit

by on Dec.11, 2010, under RobOrchestra, Robotics Club, Vibratron

After several attempts at getting the 180 separate parts necessary for the previous vibratron key unit laser-cut, we finally found a feasible method for fabrication.  The father of a roboclub member offered to us the use of his large CNC routing table.  Because Acrylic does not machine well (it is much too brittle) some redesign was done to make the key units out of hardboard.

Design Changes

Hardboard - Key Unit

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

Hardboard - Full Circle

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.

Cut Sheet 1

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Tactile Simon Completed

by on Dec.05, 2010, under Personal Projects, Simon

I was able to complete the game of Simon that I was developing for my cousins in time.  The hardest part by far was getting the IR sensors to cooperate.  Here are some photos of the final product, followed by a really artistic video my roommate Mike made for me.

Overall

Top Iso

Two versions: Lombardo and Buss

Double Top Iso

Very Bright LEDs

Double Lit Up

Everything Connected to Top Structure

Lid Out

Electronics on the Back

Back

Arduino with Tons of Inputs and Outputs

Arduino

IR Emitter/Detector Breakout Board

IR Board

MOSFET Board

MOSFET and Servo

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Robotic Manipulation Cup Stacking

by on Dec.02, 2010, under Classwork

Challenge

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.

Denso End Effector

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.

Combined

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.

Gripper

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.

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