Due to Multivariable Calculus, I’ve finally converted to a TI-89 Titanium… the TI-84+ just can’t cut it anymore. It’s served me well (since 7th grade!) but I feel it’s time to move on.
The TI-84+ and the TI-89 Titanium
Update: Wheels!
The Companion Cube—with new wheels!
I finished up the wheel replacement today with a pair of Vex Omniwheels, which have little rollers on them to allow movement perpendicular to the way they’re mounted, thus resolving the previous shearing force problems.
An Omniwheel
Unfortunately, since my motor shafts are 6mm single-flat and the Vex wheels are designed for 0.125″ square, I had to drill the wheels out a bit to make it work. Lacking a drill press, I made do with a slightly smaller drill bit, a hand drill, and a rotary tool, adding in a few screws to adjust the fit and to lock the wheel against the single flat. Although there were some mistakes, I think it turned out rather well:
Closeup of the left side of the robot
Closeup of the right side of the robot
The larger wheels get over bumps more easily, and they make it faster, both to turn and to drive—the omniwheels are especially helpful while turning, as they allow me to treat the system as a two-wheel system at the back instead of a four-wheel system like it actually is.
Water Rockets
So we just finished up our unit in Engineering Tech on water rocketry, and I figured I’d post some pictures of our rockets. They all beat the required 150 foot height by a decent amount—our highest was about 260 feet from the ground, as measured by the rather inaccurate triangulation based altimeters.
The Bee Bomb
The Bee Bomb—close up
Bumblebee One
Bumblebee One, again
Status Update: Rolling Along
I’m still not quite done with all of the updates for my robot—most notably the wheels. I’ve actually run into a little trouble: the wheels I was intending to use are actually too good at sticking to the ground to turn easily—the rubber tires fall off every once in a while. To solve this, I’m planning to use some omniwheels for the front, which should convert the drive system from four drive wheels to only two, and thus reduce the shearing force on the wheels.
Got some new rear drive wheels, but I'm still waiting on the omniwheels for the front.
I’ve also got a (really short) video from before I started the wheel switch:
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Snapshot: Work in Progress
Over the summer, I’ve been working on restructuring much of the robot—both to reduce its physical size and to reduce its power requirements.
A short (and incomplete) list of changes:
- Switch from old laptop motherboard to an Artigo pico-itx computer
- Move the Kinect down—empirical data shows that it does not need to be placed very high to get useful readings
- Elevate the base (by using bigger wheels): I’ve had troubles getting over bumps due to low ground clearance
- Change microcontrollers from an ATMega328P to a ATMega2560
- Add an LCD for quick feedback on important things like battery voltage and motor speed
Source code is available for download—there’s a Git repository at tpmo.im/robot.git.
git clone git://tpmo.im/robot.git
Alternatively, browse the repository over the internet here
Pictures:
Replaced the computer and moved the kinect. It's a lot smaller now!