JDC Creations

Building a Robot from Scratch – Part 2, Design

Posted on July 20th, 2011 by jdc15 under Building a Robot | 3 Comments »

After some basic soldering and experimentation with my Arduino, I got to work on a design for the robot.  Since I have very little experience with mechanics or building things from scratch, I figured it would be a good idea to make a plan.

Step 1 – Obtain CAD Software

There are many programs out in the wild to aid you with designing your projects.  As a student I had access to SolidWorks, a great piece of software for designing pretty much anything.  Thus I began the tutorials and figured out how the software works.  After getting a basic idea I began work on my own designs.  Unfortunately not a lot of good free cad software is out there, but decent packages such as Blender and Sketchup do exist.

Step 2 – Work Out Some Designs

At first, I had quite a bit of difficulty deciding what would work and what wouldn’t given the materials I had.  This was my initial mockup:

Originally I planned to have just a sheet of plastic, some welding rods, and some servos.  This is what I came up with.  This design had a couple of problems.  For one, the weight on the legs would lever the servo attachments out of place.  Secondly, as the arms were so short it wouldn’t be able to stand up if it fell over.  A third problem was that the servos and Arduino board run at 5V or more and three AA batteries would only supply 3.6V.  Thus, the second revision:

In this version, the legs now have supports for the opposite ends of the servos.  The little stubs would be made of Turcite plastic, which is easily available on Amazon (or so I thought, more on that later).  Aluminum hands were added for extended lengths and additional batteries were put on the back.  This would supply the needed voltage.  Also added in was the microcontroller itself.  To compensate for the weight behind the robot, additional metal bars were added in front.  Now this build had a few problems.  First and foremost, there are no sensors!  Without any input, the robot would have to walk based on a prerecorded animation.  This might work but it wouldn’t be a very sophisticated robot.  Thus I decided to add a distance sensor and an accelerometer at the very least.  But how would a distance sensor work?  It would be inefficient to turn the robot just to look right or left.  Thus I would need a head servo.  However, this was a problem on its own.  An Arduino can only control 12 servos without additional circuitry.  Again, the arms were an issue.  Even with the extended hands, by my calculations, the robot would fall over because the arms don’t bend straight downward perpendicular to the body.   The solution to these problems was yet another revision:

In this revision, a number of changes were made.  For one, two Arduinos were used.  This would enable the use of additional processing power and would allow me to control the head servo without building a multiplexer.  Instead of two AA batteries, four AAA batteries were added instead.  These would be mounted on opposite sides, along with the Arduinos.  Because this balanced things out, the metal weights could be removed.  I also decided to go with a battery case in the middle instead of using the body itself because this would be easier.  The arms were redesigned as to allow the robot to get up.  The distance sensor (not shown) would be mounted to the head.  As of now, this is probably the design I’m going to be using to build the robot.

Step 3 – Order More Parts!

Since I made a new design, I needed more raw materials.  Perhaps it was a mistake on my part to order stuff before making the design.  Anyhow, I tried to order metal and plastic on Amazon, which advertised free shipping.  Problem was, this deal only applies to the United States!  As a Canadian I had to pay exorbitant shipping fees, often costing more than the materials themselves!  To solve this problem, I spent a large amount of time tracking down local plastic and metal suppliers.  They had higher prices than Amazon, but didn’t charge for shipping because I picked the materials up myself.

 


3 Responses to “Building a Robot from Scratch – Part 2, Design”

  1. Fluffy says:

    This is sooo awesome and cool! I love it :)

  2. Puya says:

    Great job! Liking the designs. Keep us updated.

  3. iseehowitis says:

    Very impressive! Makes me want to build my own

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