as yet unnamed
robot number two

Welcome again to bent machine labs.

"bent machine labs: Desire is our one true engine." (TM.)

design notes

These are some of the actual early artist's concepts of the new robot.

Believe it or not, the current design came from ideas about the Sony Aibo, a project my friend Jeff did, and an idea for an ultimate mean-ass "battle bot" I dreamed up while doing research on Elma Beaucoups.

Dig the crab.

There were three real goals:
1. Build an extremely simple walker and get it walking.
2. Make sure it's neato (and easy to modify.)
3. Goal number 3 is not yet declassified.

Six legs make good sense for a walking robot because you have stability built right in, but somehow I just didn't want to build one. The current design is for an 8 degree-of-freedom (DOF) four legged walker.

Depending on the success, programming complexity, and load-bearing ability of this design, I may add one more joint to each leg, giving it 12 DOF.

After doing a thousand sketches and hemming & hawing over them, I finally switched to a 3D modelling package to do the preliminary design work. It was a great help to figure out where everything was going to go, and how big it should be.

After all this excitement, it was time to get to work. If you are curious about the tools, materials, and the techniques used, check out my building pages.

Hobby servomotors are used in remote control planes, cars, and boats to control rudders and steering and such. They are also ideal for use in hobby robotics. They have serious gear reduction so they're pretty powerful, and also have control electronics built in so you can tell them what position to turn to.

Here are most of the body parts unassembled. You can see the layout of the servos which will be powering the legs.

The leg assembly. I was pretty happy with how this worked out with the servo cable there going up through the leg.

One of the unfortunate things about robots is the amount of wires and cables you end up with, and it becomes such a problem that one is often forced to come up with creative solutions.

There was still a lot of stuff to install, like the power system, brains, and programming jack, but as it was, a person could kind of play with it like a robot doll.

This was actually a good thing, because although I had some ideas about how to program the thing to walk, it wasn't until I got a chance to play around with it that I saw how to do it.

Here is the servo controller board and main power distibution board. The servo controller is a product made by Scott Edwards Electronics. It uses a PIC microprocessor to take a serial signal from your robot brain and can control up to 8 servos at a time using that information. Real handy.
The power distribution board serves a couple functions. First off, servo motors are pretty electronically "noisy" so you have to supply a robot with two seperate power sources. The board supplies a place to plug both in, and also two seperate switches for them. This is handy, because sometimes you need to program the robot and don't want or need the motors running.

Also, the board takes 9 volts from one of the batteries and supplies two different voltages (9 and 5 volts) for different electronics in the robot.

A on/off indicator LED may seem pretty silly to get excited about, but it comes in handy when you are experiencing power problems.

The main brain of the robot is a Basic Stamp IISX from Parallax Inc. Of the micros available, Basic Stamps are still my choice because of the programming language.

The Sony IR decoder chip there is yet another PIC micro, programmed and sold by the guy who built the "Cricket Robot" - Henry Arnold. It uses the IR receiver module to decode the signals from a Sony TV or VCR remote control. Of course, you can also get a universal remote and program it for Sony. A great chip!

Disaster strikes. While testing the link between the brain board and the servo controller, one of the servos went crazy and started smacking the leg it powered against the body. "Whack! Whack! Whack! GRIIIIIIIIIIIIIIIIND..."

Guess now we know how well servos deal with repeated impacts.

Turned out I wasn't sending the serial info to the controller at the right baud rate.

Dang! Here's the gear that got stripped. Don't know why this fascinates me so much.

Fortunately, it is possible to order gear sets for servos, and they're cheap. Did I mention that the best place to get servos is Tower Hobby? Three days later I was up and running again. Now that I have the perspective of many years I think that I should have built something with wheels. I mean it's not as cool, but as the iRobot Roombas have shown, wheels are more practical I think.

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Everything copyright, 2000 Dave Benz

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