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MeArm

I had been meaning to build a robotic arm and the open-source MeArm looked like the perfect project.

Picking a version

The MeArm is an Open Source 4DOF robot arm. It is intended to be a low cost and accessible robotics project for STEAM education.

The hardware is released under Creative Commons Share-alike 3.0.

As a result, there are a lot of versions out there and finding one that has enough documentation is tricky. V1 looked well documented and it is the version I chose.

FF

Process

From sourcing—and tweaking—vector files, to assembling, calibrating, and programming the arm, this project was really fun.

Laser cutting

Vectors files were available online and the only issue that I encountered was a scaling problem when working with Ponoko’s templates.

To be safe, I duplicated a couple of pieces that I felt could break during assembly.

Acrylic

I love the neon green 0.118 inches acrylic that I used to laser cut the parts.

It was also soft enough to screw directly into it, without having to tap the holes.

Recyclability is limited, though, and I might consider laser cutting wood instead of acrylic in the future.

Experimenting with joysticks

It felt like a good idea to operate the arm with joysticks.

Movements were way too jerky and this is one thing I’d work on if I spent more time on this project.

Interpolation

In the code that came with the meArm version I used, to go from point A to point B, the position would be accessed by activating one servo at a time.

I was not satisfied by this and coded an interpolation so two servos could be activated at once.

This resulted in a much smoother motion and faster time to destination.

Improvements

If I were to spend more time on this project, I would:

  • work on sensing (most likely by adding an HC-SR04): The arm should be aware of its surroundings and be able to act based on what’s being registered by sensors.
  • work on joystick motion: The arm should stay in position until the joystick is activated. Speed should not be linear; I’d like to implement exponential acceleration and deceleration.
  • refine the interpolation to control more than two servos at once.