VEX Design Challenge

Entry: Heaterbot

Challenge Summary

VRDCUsing Autodesk Inventor 2010, design a VEX robot that can do a household chore or activity falling under one of the following categories: necessity, convenience or entertainment. If you don't currently have Autodesk Inventor, you can download a free* version of the software on the Student Education Community at: http://students.autodesk.com.

Entry Detail

As is inevitable on most VEX Robotics teams, Team 254 members have found themselves working on their robots late at night...often without a heater, and never with one in reach. To solve this problem, we thought of the most efficient, user-friendly way to move the heater – and came up with Heaterbot.

We planned for Heaterbot to use a holonomic drive. This drive system would let the heater move freely around as well as rotate in place. We also aimed for a central spooling mechanism which could wind the extension cord connecting it to the wall. After talking with the 254A programmer, we determined that we could automate the spooling with a shaft encoder. Under normal circumstances, the spooling motor would pull slowly inwards on the extension cord. If the shaft encoder detected that the cord had stopped spooling, the motor would start to spool outward, loosening the cord. When the robot stopped moving, the motor would stop spooling, and then slowly pull inward again, taking up the slack in the cord.

Because we used Autodesk Inventor, we were able to design our entire robot before picking up a single wrench. Autodesk eliminated most of the time we would otherwise waste prototyping with actual pieces – in fact, we were able to construct the entire base without a single issue; all that remained was mounting the heater on top. Some of the features we found useful were the simple orbiting tools, easy mating utilities, and lightweight user interface. But perhaps the most valuable Inventor utility was the rendering tool, which made our design look just like the real thing with ease.

Although we were anticipating making a robot solely for the 2010 Digital Prototyping Challenge, we have found Heaterbot to be an incredibly useful asset in our regular build sessions. Because the robot uses so little power, we have hardly ever had to change its 7.2V battery, making it one of the most reliable, worry-free tools in our workshop.

Entry Files

  • Stage 1
    Stage 1
    We started our design by combining four identical drive sections to create the entire drive base, digitally and physically.
    file type: JPEG Image (image/jpeg)
    file name: Stage 1.jpg
    file size: 16.61 kb
    download file
    (right click, save as)
  • Stage 2
    Stage 2
    Here is the completed drive base, showing four Stage 1 components.
    file type: JPEG Image (image/jpeg)
    file name: Stage 2.jpg
    file size: 37.05 kb
    download file
    (right click, save as)
  • Stage 3
    Stage 3
    Here the superstructure has been added to the drive base. The heater mounts on the top of the superstructure, and the spool goes in the empty space on the inside.
    file type: JPEG Image (image/jpeg)
    file name: Stage 3.jpg
    file size: 41.31 kb
    download file
    (right click, save as)
  • Stage 4
    Stage 4
    Heaterbot is almost complete with the addition of the spool. Hidden behind the spool is a secondary axle. High strength chain runs between the primary and secondary axles, geared so that the latter spins five times as fast as the former. A shaft encoder mounts on the secondary to measure how fast the spool is rotating.
    file type: JPEG Image (image/jpeg)
    file name: Stage 4.jpg
    file size: 53.21 kb
    download file
    (right click, save as)
  • Stage 5
    Stage 5
    Here is the completed Heaterbot, with all the electronics mounted (microcontroller, receiver, and single-wire shaft encoder).
    file type: JPEG Image (image/jpeg)
    file name: Stage 5.jpg
    file size: 53.62 kb
    download file
    (right click, save as)
  • Superstructure Isometric
    Superstructure Isometric
    Here is the superstructure by itself. The heater goes on top.
    file type: JPEG Image (image/jpeg)
    file name: Superstructure iso.jpg
    file size: 23.1 kb
    download file
    (right click, save as)
  • Drive Isometric
    Drive Isometric
    Here is the drive train by itself. The superstructure mounts on top.
    file type: JPEG Image (image/jpeg)
    file name: Isometric Drive.jpg
    file size: 25.72 kb
    download file
    (right click, save as)
  • Spool Isometric
    Spool Isometric
    Here is the spool by itself. It mounts between the drive and the superstructure, and is what hold the extension cable. One of the 30-tooth high-strength sprockets is chained to a 6-tooth HS sprocket on the shaft encoder.
    file type: JPEG Image (image/jpeg)
    file name: Spool Iso.jpg
    file size: 21.26 kb
    download file
    (right click, save as)
  • Top
    Top
    A top view of Heaterbot.
    file type: JPEG Image (image/jpeg)
    file name: Top.jpg
    file size: 30.7 kb
    download file
    (right click, save as)
  • Side
    Side
    A side view of Heaterbot.
    file type: JPEG Image (image/jpeg)
    file name: Side.jpg
    file size: 25.67 kb
    download file
    (right click, save as)
  • Back
    Back
    A view of Heaterbot from the back.
    file type: JPEG Image (image/jpeg)
    file name: Back.jpg
    file size: 22.46 kb
    download file
    (right click, save as)
  • Front
    Front
    A frontal view of Heaterbot. The only thing that distinguishes the front, side, and back views is the placement of the microcontroller, receiver, and shaft encoder axle.
    file type: JPEG Image (image/jpeg)
    file name: Front.jpg
    file size: 27.42 kb
    download file
    (right click, save as)
  • Team 254 Heaterbot
    Team 254's submission for the 2010 Autodesk® Inventor® 2010 Digital Prototyping Challenge.

    Designers:
    John Mueller
    Charlie DePalmo
    Taylor Furtado

    CAD Lead:
    Taylor Furtado

    Build Team:
    Charlie DePalmo
    Mark Barneond
    John Mueller

    Programming Lead:
    Daniel Fernandes

    Animation Team:
    Erik Anderson
    Derrick Dominic
    Drew Willner

    Camera Work:
    Drew Willner
    Winston Young
    file type: YouTube Video (youtube)
    file URL: http://www.youtube.com/watch?v=wRRYrNrHjfM

User Details

bellpride
Team Number: 254Z
Joined: 01-29-2008 08:19 PM
Challenge Entries: 2 entries

Entry Voting

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User Comments (7)

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  • ChrisHam
    03-15-2010 12:41 PM
    Ok. I think I understand. The inner end of the extension cord twists and turns as the spool winds the cord in. Watch out as in time that bit of cord will fail and short circuit to the metal chasis. Have a look at slip rings as they are commonly used to transfer power over rotating joints. Not sure how you would design a safe one into the heaterbot though.
  • bellpride
    03-15-2010 03:40 AM
    @ChrisHam:
    I think Tman254 might have misunderstood your question (or maybe I do!). To clarify:

    The inner end of the extension cord (connected to the heater) is fastened as close to the center of the spool as possible. The female prong turns pretty much in place underneath the heater and over the spool. The heater cord is in a clump in the same area, connected to the extension cord. In the "relaxed position" the extension cord is all the way in. As this cord winds out, the heater cord (not the extension cord) slowly curls because the prong rotates in place. Since the extension cord is zip-tied to the frame itself (we saw no need to zip-tie it to the heater cord), when the cord is completely stretched out, the robot simply stops moving (unless it is on some really grippy surface traveling directly away from the plug, in which case it *might* pull the cord straight out of the wall...we haven't tried to do this).

    The outer end of the cord (connected to the outlet) does not normally have enough force to be ripped out of the outlet (the exception is the case above). The robot is direct-driven and holonomic, and is pretty light as well. Between the minimal weight and outward spooling, there is hardly any tension in the cord at all. The onboard shaft encoder makes it fairly simple to digitally stop how far the robot can spool out - eliminating any safety hazards caused by the electrical cord.
  • Tman254
    03-10-2010 08:27 PM
    @ChrisHam
    truthfully the only way we could protect against that was just not to drive that far away from the wall. In actuality though we had a really long extension cord and have a really small garage so we never ran into that problem. Although i suppose if we did end up having that problem we could just zip-tie the two cords together or use electrical tape to hold them together.

    Thanks for great questions.
  • ChrisHam
    03-08-2010 01:23 AM
    Spooling is a cool idea but how are you stopping the end of the cable that is attached to the heater being ripped out as the other end winds in?
  • Tman254
    03-07-2010 10:36 PM
    @Krummel
    Hi I am the one who did the CAD work on Heaterbot. I did not even notice that my wheels were misaligned, thank you for pointing that out. I must have misaligned the holes when i placed the two motors, they are reversed so I must have counted from the wrong side of the drive rail. The actual Heaterbot was built properly and no wheels are misaligned.

    Thank you for your concern.
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