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New Stuff (well, kinda)

April 17, 2011

Alright, so I’ve been working on a bunch of NXT projects recently, surprise surprise. However, of the 9-ish I’m working on, I can reveal 7 of them, in alphabetical order: the Arm-Way, the BallBot+, the Big Car, the Double Pendulum, the Dual Joystick, the Four-Legged Bot, and the OctoBug. Some of my readers will recognize some of these things, some will not. Each bot will have it’s own post, since it would be crazy to try and pack each bot into one post. 😀

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First off, before I dive into what these are, I’ll make a quick disclaimer: I’m lazy. I’m willing to admit that. So, in big posts like this, I will not be imbedding images, but providing zip files instead. Please do not ask me to post pictures, as they are provided. I do not have a fast enough computer to imbed and upload every image. -_-

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So, that aside, let’s dive into the first one: the Arm-Way.

Arm-Way

Arm-Way

The concept of a two-wheeled, inverted pendulum robot is not new. Even I have made more than a few (successful) NXT balancing robots.

However, this bot aims to change some things that seemed to create a “rut” of sorts: for some examples, a balancing robot could only balance by driving back and forth, or tilt could only be detected by Light Sensor(s) / EOPD Sensor(s) / Gyro Sensor(s).

In this design, I use only an Accelerometer for input (yes, I know that’s rather unconventional) and 3 motors for output. (Like all my current designs, I only use one NXT.)

The Accelerometer is located directly below the axle, for two reasons:
1. Locating the sensor near the axle allows you to read the actual tilt of the robot, not the actual fall speed.
2. Placing the Accelerometer directly beneath the axle causes the sensor to actually swing forward and backwards slightly as the robot tilts, and thus gives a larger reading range (and compensates for the robot’s forward-backward acceleration “noise”, if you will).

This allows for a fairly simple balancing system, but often these wheeled systems aren’t enough of a challenge of me. So, I added the third motor (mentioned above) with an arm. This makes use of the Law of Conservation of Angular Momentum, which I just learned about in Physics. This law states: “If the sum of the torques on a system is equal to zero, the angular momentum never changes.” This is similar to the Law of Momentum Conservation (The velocity that an object develops in response to launching another object), but uses a few more variables (like the Greek letter theta: Θ, θ) and works in situations where things are rotating. This is applied in things like momentum/reaction wheels. I’m using the exact same concept, except I prefer to just build a weighted arm, rather than an entire wheel. (Wheels take up more space and parts.)

Since the arm needs some mass to provide angular momentum resistance, I attached two wheels to the end. In the first few pictures in the ZIP, they look like the front wheels of a dragster, but in reality they should never touch the ground. 😛 Here are the pics, I hope you enjoy!

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Coming soon, to a blog near you: The BallBot+!

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2 Comments
  1. I can’t seem to fully load this post from my droid!!

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